New Developments in Vaccines Against Herpesviruses: Update for the Clinician

Transcription

1 PEDIATRIC AN APPROVED SYSTEM FOR CONTINUING MEDICAL EDUCATION Volume 3 PUBLICATION DATE: MARCH 1, 201 EXPIRATION DATE: MARCH 1, New Developments in Vaccines Against Herpesviruses: Update for the Clinician MODERATOR: Mark R. Schleiss, MD Professor of Pediatrics; Director, Pediatric Infectious Diseases, Division of Infectious Diseases and Immunology, University of Minnesota Medical School, Minneapolis, Minnesota DISCUSSANTS: Adam P. Geballe, MD Professor, Departments of Medicine and Microbiology, University of Washington; Member, Divisions of Human Biology and Clinical Research, Fred Hutchinson Cancer Research Center, Seattle, Washington Michael A. McVoy, PhD Professor of Pediatric Infectious Diseases; Member, Department of Microbiology and Immunology, Virginia Commonwealth University, Richmond, Virginia Editor-in-Chief: Kirstin A. Lee, MD Instructor, Pediatrics Division of Hospitalist Medicine Washington University School of Medicine St. Louis, Missouri This continuing medical education program includes: + Statement of learning objectives + Pretest questions and answers + Audio recording and printed transcript of panel discussion + Post-test questions + Post-test response form + List of recommended supplementary reading materials Washington University designates this enduring material for a maximum of 3 AMA PRA Category 1 Credit(s) TM towards the AMA Physician s Recognition Award.

2 Learning Objectives This enduring material is designed for pediatricians, nurse practitioners and other allied health professionals who care for children. The intended result of this activity is to achieve a change in competence, performance, and patient care. After completing this activity, the participant should be better able to: 1. List the eight human herpesviruses and the diseases they cause. 2. Discuss currently licensed vaccines and vaccines in clinical testing for human herpesviruses. 3. Describe similarities and differences for vaccines against varicella-zoster virus that prevent chickenpox and the long-term complications of chickenpox and shingles. 4. Identify both the short-term and long-term morbidity that can be associated with human herpesvirus infections. 5. State the clinical presentation of the major disabilities associated with congenital and perinatal infections caused by herpes simplex virus and cytomegalovirus.. Discuss the potential role of vaccines against the human herpesviruses in the prevention of human cancers caused by these pathogens. Pretest Questions Before listening to the audio CD or examining the transcript of the panel discussion, you will find it useful to test your general understanding of the subject of this program with this brief introductory quiz. (The correct answers can be found on page 9 of this booklet.) 1. Which herpesvirus infection is currently vaccine-preventable? 3 a. Epstein-Barr virus (infectious mononucleosis) 3 b. Human herpesvirus type (roseola) 3 c. Cytomegalovirus (CMV) 3 d. Varicella-zoster virus (chickenpox) 2. Which of these human herpesviruses is the most important long-term cause of disability in newborns? 3 a. Herpes simplex virus (neonatal herpes) 3 b. Cytomegalovirus 3 c. Kaposi s sarcoma herpesvirus 3 d. Epstein-Barr virus 3. One reason to drive a vaccine against CMV would be for prevention of disease in immunocompromised bone marrow or organ transplant recipients. Which of the following is NOT a complication of CMV in the transplant setting? 3 a. Failure of the transplant 3 b. Emergence of resistance of CMV to antiviral drugs 3 c. Graft-versus-host disease 3 d. Increased risk of urinary tract infection 4. Which human herpesvirus is most clearly associated with development of cancer? 3 a. Herpes simplex virus 3 b. Kaposi s sarcoma herpesvirus (human herpesvirus type 8) 3 c. Varicella-zoster virus 3 d. Human herpesvirus type 5. Human herpesvirus type can actually integrate its viral DNA into the host cell chromosome. 3 True 3 False. The same vaccine that is licensed for prevention of chickenpox is also licensed for prevention of shingles. 3 True 3 False Editorial Advisory Board Cheryl L. Grave, RN, MSN, CPNP* Kirstin A. Lee, MD Lisa M. Moscoso, MD, PhD Louis J. Muglia, MD, PhD Christopher J. Pingel, MD Joseph W. St. Geme III, MD Andrew J. White, MD # Allyson R. Zazulia, MD Disclosure Policy: It is the policy of Washington University School of Medicine, Continuing Medical Education, to ensure balance, independence, objectivity, and scientific rigor in all its educational activities. All planners, faculty and other persons who may influence content of this CME activity have disclosed all relevant financial relationships with commercial interests. All disclosures have been reported and are indicated with their presentations. Any potential conflicts were addressed and resolved. Speakers are also expected to openly disclose inclusion of discussion of any off-label, experimental, or investigational use of drugs or devices in their presentations. Presentations are expected to be based on evidence that is accepted within the profession of medicine as adequate justification for their indication in the care of patients. All scientific research should conform to the generally accepted standards of experimental design, data collection and analysis. These presentations are not an endorsement of any commercial interest. These presentations are the views and experiences of the presenters. The presenters views do not represent the policy or position of Washington University School of Medicine. Washington University School of Medicine, Continuing Medical Education is the sponsor for CME credits. Accreditation: Washington University is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians. Credit: Washington University designates this enduring material for a maximum of 3 AMA PRA Category 1 Credit(s) TM. Physicians should claim only the credit commensurate with the extent of their participation in the activity. * Has no financial interest or other relationship Has no financial interest or other relationship Has no financial interest or other relationship Has no financial interest or other relationship Has no financial interest or other relationship Has no financial interest or other relationship # Has no financial interest or other relationship Has no financial interest or other relationship This course can be completed by listening to the audio CD and by reading the transcript. A multiple-choice test must be completed to earn CME credits. In order to receive credit, a participant must have a designated passing grade of 75%. The estimated time to complete this activity is 3 hours Washington University School of Medicine.

3 Transcript of the Panel Discussion (As recorded in the audio CD) W DR. MARK R. SCHLEISS*: I m Mark Schleiss, and I m a Professor of Pediatrics and the Director of Pediatric Infectious Diseases at the University of Minnesota Medical School in Minneapolis, Minnesota. DR. ADAM P. GEBALLE : I m Adam Geballe. I m a Professor in the Departments of Medicine and Microbiology at the University of Washington and a member in the Divisions of Human Biology and Clinical Research at the Fred Hutchinson Cancer Research Center in Seattle, Washington. DR. MICHAEL A. McVOY : I m Michael McVoy. I m a Professor of Pediatric Infectious Diseases and a member of the Microbiology and Immunology Department at Y Virginia Commonwealth University in Richmond, Virginia. E 1 DR. SCHLEISS: We are here today to talk U about New Developments in Vaccines Against Herpesviruses: An Update for the Clinician. I m really pleased that Mike and Adam are here. Thank you both for being here today. We re going to begin by talking about the human herpesviruses: What they are and what kind of diseases they cause. There are eight human herpesviruses that are associated with disease in children and adults. These include herpes simplex viruses [HSV] type 1 and 2; the varicellazoster virus or chickenpox virus; the Epstein-Barr virus [EBV], which causes I most cases of infectious mononucleosis; cytomegalovirus [CMV], which is an important cause of birth defects in newborn infants; and human herpesviruses [HHV] type and 7, which cause an ailment in O young children known as roseola. We ll talk about some of the other diseases that are associated with that virus as well. Finally, the eighth herpesvirus is known as Kaposi s sarcoma [KS] herpesvirus or KSHV. R 2 Mike, I wonder if you could start us out by just talking about the structure of the herpesviruses. What kind of viruses are these, and what do we need to know about * Research Support/Grants: National Institutes of Health. Research Support/Grants: National Institutes of Health. Research Support/Grants: Hookipa Biotech AG; Merck & Co, Inc.; National Institutes of Health; Vical, Inc. T the biology of these viruses that might help us understand how to develop vaccines? 3 DR. McVOY: All of these viruses are similar in terms of their physical structure and composition. They all have relatively large double-stranded DNA genomes, and that s packaged within a capsid. The capsid is then surrounded by a somewhat amorphous structure of tegument proteins, and then the whole particle is surrounded by a lipid bilayer of what we call the viral envelope. The viral envelope has glycoproteins on the surface that are critically important for viral entry into cells, and these are the usual targets for neutralizing antibodies that are important for vaccine development. One thing to remember about these viruses is that they have two life cycles essentially: One is replication to produce progeny virus; and the other is latency. All of these viruses establish latency, and that can be very important in their natural history and pathogenesis. 4 DR. SCHLEISS: That s an important point to keep in mind as we discuss these potential vaccine candidates, the idea that they can cause infection, become latent, and then recur later in the course of a lifetime. 5 Let s talk about some of the diseases in childhood and adolescence that we want to target when we think about herpesvirus vaccines. Certainly, one of the most important is chickenpox, and we ll talk about chickenpox and the latent form of chickenpox virus when it reactivates later in life, a disease called shingles. We ll talk also a little bit about vaccines that are in development for mononucleosis caused by the Epstein-Barr virus and infections caused by cytomegalovirus as well. Adam, in your work you deal often with immune-compromised patients. I wonder if you had any comment about priorities for herpesvirus vaccines in that particular patient population. 7 DR. GEBALLE: Yes. Herpesviruses are a major problem in solid-organ and hematopoietic stem-cell transplant patients and in AIDS [acquired immunodeficiency syndrome] patients whose immune systems are not working well due to the HIV [human immunodeficiency virus] and other immunocompromised settings, including just cancer chemotherapy. At the Hutchinson Center, we see many patients who develop the herpesvirus active infections, and we end up using many antivirals, acyclovir and ganciclovir, to try to suppress those infections after transplants. So it s an ongoing problem. A lot of money is spent. Acyclovir is quite effective for preventing varicellazoster and herpes simplex, but we end up giving it for a year after a bone marrow transplant, for example, so it s a long commitment. The other drugs for preventing CMV are more difficult to use and have a lot of toxicity; so a vaccine for any or all of those viruses would be great. Epstein-Barr virus is also a problem, and we ll talk about that later. P 8 DR. SCHLEISS: A year is a long time to be on an antiviral medication. Are there ever issues that emerge where patients that are on long-term treatment with antiviral medicines develop strains of virus that might be resistant to those medicines? { 9 DR. GEBALLE: That certainly can happen. In our patient population, it s not too common to develop acyclovir-resistant herpes simplex or varicella-zoster, but it does happen. CMV also. It depends on the kind of immunocompromised patients: In the hematopoietic stem-cell transplants, resistance is not terribly common; but in lung transplants, for example, it s more common. The side effects of the treatment for CMV are a major limitation in its use, and we re constantly battling the trade-off between side effects and trying to suppress the virus. So, again, vaccines would be terrific. } 10 DR. SCHLEISS: It sounds like the development of a vaccine could be very useful in preventing the need for long courses of medication; so, that s an area to keep in consideration as well. q11 Let s begin to talk about some of the individual viruses on our list of the human herpesviruses. We ll start with the infection for which we have a vaccine that s licensed and available and in use by clinicians, and that s varicella-zoster virus infection. Varicella-zoster virus is the cause of chickenpox, usually a disease of young children. Then, if it reactivates later in life, as Mike was talking about earlier, reactivating from latency, then that disease is called shingles. w12 Currently, this is the only herpesvirus for which we have a licensed vaccine. The licensed vaccine for chickenpox was developed actually in Japan in the 1970s, and it came from a strain of virus that was isolated from a patient. That virus was then passaged in cell culture innumerable times until it underwent a process that we refer to as attenuation. The genetics of the virus changed such that it could no longer cause serious disease but it could still elicit an immune response that would provide protection when given as a vaccine. Of course, attenuated virus vaccines are a mainstay of how we develop vaccines for many human diseases. The varicella vaccine was licensed W Numbers in black circles designate specific tracks on CD. 1

4 in 1995 in the United States. It s currently given as a two-dose series to young children, and it s had a very dramatic impact on varicella disease in infants and children. Prior to the licensure of that vaccine, there were approximately 3.5 to 4 million cases gests that shingles in older adults can lead to an increased risk for heart disease and coronary artery disease. 3 So, more and more health benefits are being noted all the time by a strategy that reduces shingles through vaccination. 12 Let s talk a little bit about Epstein-Barr virus vaccines. Epstein-Barr virus is an important cause of mononucleosis, which can be really a major problem in adolescent patients. It consumes a lot of health care resources, and pediatricians and family of chickenpox a year in the United States, o 8 Adam, I wanted to ask you a little bit practitioners in primary care deal with the and these resulted in over hospitalizations and up to 150 deaths in otherwise published just this year on a new shingles clinic. Mike, do you have any observations about some very exciting research that was problem of mononucleosis quite often in the normal, healthy children. 1 This was really vaccine that s a little bit different than the about the current state of Epstein-Barr virus one of the driving forces for licensing the chickenpox vaccine that we give to young vaccines and comments on what the clinician might need to know about the future varicella vaccine. children. Rather than a live attenuated vaccine, this vaccine evidently just picks one development for vaccines for this virus? e 1 Now, Adam, I was going to ask you to comment about using vaccines not only to protein from the virus and then gives that in A13 DR. McVOY: As I mentioned earlier, all prevent chickenpox in young children, but the form of a protein subunit with some herpesviruses have both a lytic life cycle or to prevent reactivation of the latent form or kind of immune stimulant. My understanding is that this vaccine also was shown to be more virus and a latent life cycle where they a productive life cycle where they produce shingles. What do we have currently for shingles vaccines? pretty effective in clinical trial. establish latency and remain in a host for r 2 DR. GEBALLE: The same strain of virus p 9 DR. GEBALLE: I will comment on that, the life of the host. In the case of EBV, that s attenuated that you referred to that s yes. The New England Journal [of Medicine] paper from this last year that reported more associated with that latent life cycle, much of the disease really is thought to be used in children is used at a higher dose in adults. There was a large study done to this trial showed that, rather than 50% efficacy as shown with a live attenuated vacizes those B cells and maintains them for which EBV infects B cells and immortal- show that about 50% efficacious in preventing reactivation in older adults age 50 and over, I believe. 2 So it s now recommended cine, this was more in the high 90% efficacy long periods of time. This is thought to be that people should be vaccinated at age 50 in preventing shingles reactivation. 4 So it s part of the mechanism by which Epsteinor so; it s approved at 50, but it s paid for a very promising vaccine. As far as I know, Barr virus may be associated with the after age 0. One of the problems is it only there have been no trials yet in children, and development of cancers, in particular reduces the frequency of reactivation by it could be quite different because the setting is fairly unique in the vaccine world in nasopharyngeal carcinoma, Hodgkin s lymphoma, and Burkitt s lymphoma in the case about 50%. So that s what we re limited to at the moment. that it s a therapeutic vaccine to boost of Epstein-Barr virus. 5 So, a vaccine against 3 immunity to an infection that already exists. Epstein-Barr virus would potentially benefit t DR. McVOY: I have a question, Adam. not only subjects who might develop infectious mononucleosis but may ultimately So, whether or not this subunit vaccine will Does it reduce the severity of zoster? work in children who have not been 4 DR. GEBALLE: It reduces the severity also have benefit in preventing development exposed is really an unknown at this point. beyond the preventing of zoster. Reduction of cancers like nasopharyngeal carcinoma, But it looks like it s very promising in older in severe zoster is in the range of 5% or so. Burkitt s lymphoma, and Hodgkin s. adults who are seropositive already from But it s not perfect. prior infection. S14 DR. SCHLEISS: So Epstein-Barr virus y 5 DR. SCHLEISS: Many clinicians who [ can cause not only mononucleosis, but it s 10 DR. SCHLEISS: It ll be interesting to see take care of patients who have shingles will associated with substantial risk of malignant diseases, particularly in certain parts of how that vaccine fares, then, in future studies. Perhaps clinicians listening to this point out that it s not just the rash of shingles that s the worry but the pain and disability that can take place long after that a little bit further, Mike? the world. Do you want to comment on that audio will encounter the opportunity to use that vaccine in the next few years. rash is healed, an entity that s referred to as ] D It s interesting how herpesvirus vaccines DR. McVOY: In Africa, Epstein-Barr virus postherpetic neuralgia. That s one of the in general seem to reflect the same kind of is closely associated with Burkitt s lymphoma; and in Asia, nasopharyngeal carci- driving forces for shingles vaccination, not approaches that we see for vaccines for only to prevent the shingles but also to help other kinds of infections. In other words, noma. In those cases, the viral genome is reduce that long-term disability. they tend to fall either into the camp of found in the tumor cells. u DR. GEBALLE: Yes. Postherpetic neuralgia in older adults can be very debilitating then are given back as vaccines or as indi- associated with a number of other lympho- attenuated living forms of the virus that F1 DR. GEBALLE: So, Epstein-Barr virus is and require narcotics, neurosurgical interventions to try to control the pain. So there s cloned recombinant technologies and then some gastric carcinomas. 7 I think the assocividual proteins that are expressed using mas besides Hodgkin s lymphoma as well as a big need. It s not so relevant to the pediatrician in the short run, but it s important. a licensed live attenuated chickenpox vac- still being sorted out, but it likely has a role. given back to the patient. So, we have both ation of EBV with these different tumors is i 7 DR. SCHLEISS: There s recently been some evidence that I ve seen too that sugcine and then this new experimental individual protein subunit vaccine. EBV encodes a number of oncogenes, and it causes B cells to proliferate; so it likely 1. See Marin et al (17) in List of Supplementary 2. See Oxman et al (18) in List of Supplementary 3. See Wang et al (29) in List of Supplementary 4. See Lal et al (15) in List of Supplementary 5. See Longnecker et al (1) in List of Supplementary. Ibid. 7. Ibid. 2

5 plays a causal role in some of these lymphomas; so preventing EBV with a vaccine could have benefits in these other settings. G 1 DR. SCHLEISS: That s a really important point. I think that clinicians and families sometimes don t appreciate that the vaccines that we currently have in clinical practice are, in some cases, anticancer vaccines. In fact, the hepatitis B vaccine, in addition to preventing hepatitis B, is in essence an anticancer vaccine because of the strong association between hepatitis B and the L development of liver cancers. Then, of course we have the HPV vaccine or human papillomavirus vaccine, which is dramatically effective in preventing cervical cancers and other kinds of cancers and dysplasias in adolescents and young adults. So, it s quite exciting to think that an Epstein- Barr virus vaccine could one day not only be a vaccine against mono, but also be a vaccine against cancers. H 2 There s another setting in which : Epstein-Barr virus causes quite serious disease and, again, coming back to the transplant patient, Adam, I don t know if you ve had some experience with posttransplant lymphoproliferative disease, or PTLD, in Epstein-Barr virus, but there are a number of studies out there that are looking at Epstein-Barr virus vaccines to prevent that particular complication. J 3 DR. GEBALLE: Yes. It s a timely issue in that the boy in the bubble was in the news recently. Those of us that are old enough to a remember the boy with the severe combined immunodeficiency who was put into a plastic tent when he was born; and 12 years later he came out of the tent after a bone marrow transplant and died of PTLD 2 weeks after that. So it is a problem with severely immunocompromised patients and after solid-organ and hematopoietic stemcell transplants. It s not uncommon in our setting, in pediatrics in particular. Many adults are infected with EBV. We don t see it very often in the transplant setting, but a child who gets a seropositive transplant from someone who s been infected with EBV in the past, if that child is seronegative, he or she has a high likelihood of s developing acute EBV infection and a higher risk to go on to develop PTLD later on. In that setting, a number of transplant centers will monitor the patient after the transplant. In the hematopoietic stem-cell transplant, they do this fairly routinely to be able to detect when EBV is starting to replicate and follow the blood loads by quantitative PCR assays. K 4 What to do to manage it is less clear. When PTLD develops, the treatment of choice at the moment is to use an antibody to destroy the B cells, which is where EBV has established latency, and those are the cells that are proliferating out of control. So there s rituximab, a monoclonal antibody that s used commonly in lymphomas and in PTLD to knock down the number of B cells. But it s only a temporary fix, and then the hope is to be able to reduce immunosuppression so the child s own immune system can bring the B cells under control. 5 DR. SCHLEISS: We ve talked about herpesvirus vaccines and how they can be based on live attenuated variants of the virus or they can pick a protein of interest and give that back to the patient as a cloned recombinant technology approach. Mike, what do you think will be the optimal solution for Epstein-Barr virus vaccines, and what s currently out there in clinical trials that clinicians may want to learn about with this particular virus? DR. McVOY: With a virus that has potential oncogenic activity, a live attenuated vaccine strategy is very difficult to sell, and consequently a subunit vaccine is perhaps much more appropriate at least from a safety standpoint. So, with EBV, the subunit vaccine focus has really been on a viral glycoprotein called gp350, and there has been some recent successes with using a subunit recombinant expressed gp350 for vaccination and reduction of the incidence of mononucleosis. 7 DR. SCHLEISS: I think it s very important to keep in mind that this virus causes a lot of morbidity in primary care general practice. Pediatricians and primary care clinicians spend a lot of time dealing with mono and the aftermath of mono in adolescents. So, a vaccine for infectious mononucleosis would be very, very useful and I think welcome in clinical practice. It s noteworthy that there s a wide range of patients that could benefit from an EBV vaccine, and it will be of considerable interest to see how this field progresses in the next few years. Adam, do you have some additional insights into EBV vaccines? 8 DR. GEBALLE: The vaccine development is a complicated issue in the herpesvirus. There are many different populations. I think it s interesting in EBV that one of the clinical settings being envisioned to study the EBV vaccine is in college. The freshmen come in at a fairly low seropositivity rate: 20% or 30% seroconvert during those 4 years in college. So it s a population in which a vaccine like the gp350 could be tested. I think some of the studies are being done in that setting. It s difficult to establish efficacy with the tumor reduction because those tumors are rare and occur in many different settings; so it s going to be a while before we know whether a vaccine could prevent those complications. d 9 DR. SCHLEISS: Is it understood at this point why college students seem to be at such a high risk to acquire EBV infections during their college experience? f10 DR. GEBALLE: EBV is sometimes called the kissing disease. So, children leaving home and becoming more sexually active is perhaps the risk factor in that age range, but I don t know if that s established. Early college is the setting where papillomavirus vaccine was studied early on as well. g11 DR. SCHLEISS: So it s interesting, as we think about the human herpesviruses and herpesvirus vaccines, we can identify different points in a lifetime where these vaccines might be most useful. Although, as we ve discussed with chickenpox, we think of that as a disease of young children, Epstein-Barr virus we might think of as a vaccine-preventable disease someday for adolescents where there s a particularly high attack rate. One thing that we observe in general, I think, in adolescent vaccines is that they are not used as often as public health officials would like to see them used. Whether you re talking about HPV vaccine rates for human papillomavirus infection, which are disappointingly low in the United States, or future vaccines for other adolescent diseases, I think we all need to do a better job to encourage families and young adolescents and adults to use these very effective vaccines that become available. h12 DR. GEBALLE: One other comment about the epidemiology of these viruses, they vary a lot by geography. In Africa, EBV is acquired at a young age very commonly. 8 So, applying the vaccine in different settings is going to require some additional study. j13 DR. SCHLEISS: Let s discuss another herpesvirus vaccine that could be useful in a number of patient populations, potentially both infants and adolescents, and that s a vaccine for herpes simplex virus. There are two different types of herpes simplex virus, type 1 and type 2. Herpes simplex virus type 1 typically causes recurrent oropharyngeal lesions or mouth lesions, whereas herpes simplex virus type 2 is the virus that s most commonly associated with genital 8. See Slyker et al (23) in List of Supplementary 3

6 N 9 DR. SCHLEISS: That s an important question. As Adam alluded to earlier, there are a lot of variations around the world on this question. For example, it s been known for quite some number of years that in Japan, genital herpes due to herpes simplex virus type 1 is just as prevalent as type On the other hand, recently here in Minneapolis, we typed a number of strains from sexually active adolescents who had typical genital herpes, and they were all type So I think that these variations need to be considered on a region-by-region basis. M10 The greater point, though, is that a vaccine that could confer protection against both of these viruses would be a very exciting development. We know that HSV type 1 causes other problems and diseases in addition to genital herpes. The two viruses, herpes simplex 1 and herpes simplex 2 are quite similar to each other at the molecular level, and the possibility that a single vaccine could protect against both is something that needs to be considered in vaccine design as well. z11 DR. GEBALLE: I would make one other comment about how this field might move forward. I have a colleague who s working on HSV vaccines and has pointed out to me that doing a therapeutic vaccine trial may be easier than doing a preventive prophylactic trial because now, especially with the evidence that patients shed the virus very often, there s something to measure in the short-term to see whether or not a therapeu- herpes, which is a sexually transmitted disease. Both of these diseases may be worth preventing. A lot of groups of herpesvirusinfected patients can be identified. These include young children attending group daycare. Wrestlers are particularly at risk for a form of herpesviruses infection called herpesviruses gladiatorum. Herpes simplex virus type 1 can be associated with encephalitis, which is a brain infection that can be very devastating, and that s seen both in adolescents and adults. So, a wide variety of populations may benefit from herpes simplex virus vaccines. k 1 But the one that s discussed the most is genital herpes, which is a sexually transmitted infection. There have been a lot of X efforts over the years to develop a vaccine for genital herpes. Mike, do you want to comment a little bit on the targets of the immune response that have been explored with herpesvirus vaccines so far in clinical trials? We were discussing earlier the structure of the virus particle. Are there particular targets in the herpes simplex virus that C have been exploited by vaccine design that have been tested in the clinic to this date? l 2 DR. McVOY: Much of the focus has, again, been on neutralizing antibodies that can target glycoproteins in the viral envelope and prevent viral infection of the target cell. In the case of herpes simplex virus vaccines, again, that s been largely directed at a viral glycoprotein called gd or glycoprotein D. This has been the major focus, I think. There s also an interest in T-cell immunity as a potential goal of inducing protection with a vaccine. ; 3 DR. SCHLEISS: Genital herpes is a disease, of course, that s characterized by frequent recurrences. An individual who gets a genital herpes infection can have repeated episodes over the course of many years where painful lesions appear. It can be very emotionally devastating and psychologically debilitating in addition to the physical discomfort that s been associated with that. I think, Adam, there have been colleagues V of yours in Seattle who ve paid a lot of attention to the question of whether or not patients with genital herpes might, in fact, be shedding the virus even when they don t have lesions and don t appear ill. Z 4 DR. GEBALLE: Yes. One of the surprises in the past few years has been the recognition that genital herpes seems to reactivate much more often on a daily basis even for short periods of time, sometimes just hours, and that you can detect DNA in the genital tract without lesions. Herpes type 2 is a risk factor for HIV transmission; so there was a big study done to try to see if suppressing HSV with acyclovir or valacyclovir could reduce transmission of HIV. 9 People who are HSV positive are more likely to acquire the infection, and people who are HSV positive are more likely to pass it on than those who are negative. That trial was not successful, and it may be because the low-level reactivation occurs frequently and recruits CD4 cells to the genital mucosa where they re at risk for becoming infected with HIV. That s still being worked out, but it s another reason why an HSV vaccine would have benefits beyond just HSV. It would likely help with preventing HIV. 5 DR. SCHLEISS: As Mike already alluded to, the recombinant protein subunit vaccines for genital herpes have been disappointing in clinical trials so far. In other words, studies that have been designed to see if immunization prevents somebody from acquiring a genital herpes infection have not shown a very strong protection rate. Another strategy that s worth considering is the idea of giving a vaccine to somebody who s already infected with the genital herpesvirus. In other words, they re already positive for HSV-2. Could you decrease the number of recurrences that they have by augmenting their immunity with a vaccine? Could you perhaps decrease the amount of viral shedding that goes on by giving them a vaccine as well? So this concept of a therapeutic vaccine to somebody who s already infected with that particular virus is one that s still being evaluated in the clinic. There was a promising study that just came out a few months ago that looked at a herpes simplex virus vaccine based on the glycoprotein gd2 [glycoprotein D from HSV-2] and a T-cell target known as ICP4 given with an adjuvant. This looked actually pretty promising in early studies of immunogenicity. So, decreasing the number of recurrences of genital herpes could be another situation where a vaccine might be employed in clinical practice. 7 DR. GEBALLE: I would just make one other comment about herpes simplex type 1, which can also cause genital disease. There was a large study done with a gd2 recombinant vaccine that showed no efficacy against herpes simplex type 2, but in a subset of women, there was efficacy against HSV type 1 disease. 10 It was puzzling why 9. See Celum et al (8) in List of Supplementary 10. See Belshe et al () in List of Supplementary B HSV-2 glycoprotein would protect against HSV-1 and not HSV-2. There s some conjecture about how easy it might be to neutralize one virus versus the other. HSV-1 might be easier to neutralize, and that might be the result. But there s a lot we don t understand about neutralizing HSV-1 and 2, I think. 8 DR. McVOY: Mark, we all teach our students that HSV-1 is primarily responsible for oral herpes and HSV-2 primarily responsible for genital herpes. We also tell them that that paradigm seems to be shifting. I was wondering if you could give your perspective on how much it s shifting, and we ll be dropping that distinction in the future? Also, the trial that Adam referred to had a surprisingly high incidence, I think, of HSV-1 in the genital herpes setting Ibid. 12. See Umene and Kawana (27) in List of Supplementary 13. Unpublished data. See also Voigt and Balfour (28) in List of Supplementary 4

7 tic vaccine is having an effect on shedding; b and, for people who have frequent recurrences, on the frequency of recurrences. Whereas, it s much more expensive and time consuming to do what we would like to do, which ultimately is to prevent infection in the first place. x 1 DR. SCHLEISS: We re also thinking about these issues against a backdrop in the last few months where we ve seen a large resurgence in many different kinds of sexually transmitted infections in the United States, particularly strains of gonorrhea that are resistant to antibiotics and difficult to treat, and increased numbers of cases of syphilis. 14 That s a disconcerting development. Genital herpes is still a national epidemic. I think as clinicians we need to be mindful of prevention not just with vaccines that may be developed in the future but also encouraging condom use in our young, sexually active patients to try to prevent not only genital herpes but other sexually transmitted infections. c 2 There may be benefit from a genital herpes vaccine that could be realized not only for a young woman but also for her newborn infant. About 4000 cases of what we call neonatal herpes occur in the United States every year. 15 These are very devastating infections which can produce long-term neurologic injury to these infants and in some cases lead to mortality along with permanent disability. So one of the goals of a herpes vaccine program might be to help protect against neonatal herpes in infants who are born to women of child-bearing age, particularly if that young woman is at risk for getting a primary genital herpes infection during pregnancy. n v 3 DR. GEBALLE: Mark, can I ask you a question about pediatrics practice these days? Because I know for many years there have been attempts to try to predict which newborns could develop herpes in the first few days of life based on a variety of parameters, particularly mother s shedding. I understand that has never been very successful. So is the practice just to observe; for example, if a woman has a primary lesion, an active lesion, that might be m a tipping point to start empiric acyclovir? Or how do you approach a newborn with that question? 14. See Workowski and Bolan (30) in List of Supplementary 15. See Stanberry (24) in List of Supplementary 1. See Stanberry et al (25) in List of Supplementary 4 DR. SCHLEISS: Yes. It continues to be a source of uncertainty how best to protect and treat empirically infants that might be at high risk. Certainly, a baby born vaginally in the setting of a herpetic lesion should be empirically covered with antiviral treatment in the newborn period. I think the really difficult cases are the young women, and typically they are young, unmarried women who have histories of other sexually transmitted infections who may present in labor with an unrecognized or undiagnosed case of primary genital herpes. As we talked about earlier with the shedding studies that are ongoing in Seattle and other places, we know that, in fact, patients may have genital herpes infections and yet not have the classic lesions or vesicles that we think of when we think of herpes. So I think we have to be very mindful of the risk and think about babies that might be at increased risk and have a very low index of suspicion for intervening and treating empirically. One of the revolutions in infectious disease care at the bedside is the burgeoning number of pointof-care assays that we see now that can rapidly identify pathogenic DNA or protein sequences from microorganisms including viruses in a matter of hours or even minutes, in some circumstances. I think those point-of-care tests, as they become incorporated into clinical practice, may help us identify these babies sooner. A vaccine for herpes simplex virus infection, then, is considered to still be a very high priority even in the setting of some recent clinical trials that have been disappointing and failed to show efficacy levels that would have been hoped for. 1 The pharmaceutical industry continues to push these studies forward very aggressively. 5 Another vaccine that s considered to have a very, very high priority from a public health perspective would be a vaccine against cytomegalovirus infection. That s the next herpesvirus that we want to consider in this discussion of new herpesvirus vaccines. Mike, can you comment about why we need a cytomegalovirus vaccine? Who would get the vaccine, and what kind of diseases are we trying to prevent? DR. McVOY: There are really two categories when we think about CMV disease. One is the immunocompromised patient, a transplant patient or HIV patient. In that situation, they re often CMV infected, latently infected prior to their immunocompromised state, and they suffer from reactivation of CMV. In that setting, it s very clear that T cell immunity is critically important for control of CMV disease. So, a vaccine in that context might be designed to drive a T cell response, and there have been many trials of candidates in that strategy. The second category is the congenital infection in which CMV is transmitted during pregnancy from a pregnant woman who either acquires it during pregnancy and transmits to the fetus or may be infected sometimes decades earlier and is latently infected and then may reactivate virus during pregnancy and transmit to the fetus. Then, the third opportunity is that the woman may well have been latently infected decades earlier, but during pregnancy is reinfected by a different strain of CMV, an exogenous strain very much similar to the primary infection. So, in that setting the focus has really been on neutralizing antibodies and envelope glycoprotein vaccine strategies that could induce potent neutralizing antibody responses., 7 So who would need a CMV vaccine? It would depend on whether you re discussing a transplant or AIDS patient or the congenital CMV situation. You may disagree with me, Mark, or you have your own thoughts, but my understanding is that the current focus for congenital CMV vaccine would be seronegative women of childbearing age or perhaps adolescent teenagers with the eventual hope, perhaps, of moving that vaccine strategy forward to the younger childhood vaccine scenario.. 8 DR. SCHLEISS: You mentioned that, if a baby acquires a CMV infection before birth, there can be some important longterm consequences. Can you comment on that further? What kinds of problems do these babies have? gl 9 DR. GEBALLE: The hearing loss is by far the predominant manifestation of congenital CMV infection, and it can manifest very early in childhood or not appear for a few years. It also can cause mental retardation and death even at a much lower frequency. But, Mark, you re the expert on this. gm10 DR. SCHLEISS: To talk a little bit further about the kinds of disabilities that are associated with CMV infection in the newborn infant, I think we have to keep in perspective just how common and important this problem is. It turns out that, if you take other identifiable and well-known causes of fetal injury, such as fetal alcohol exposure leading to fetal alcohol syndrome or congenital toxoplasmosis infection or neural tube defects, the magnitude of disability associated with CMV exceeds all of these 5

8 different kinds of problems combined. So it s currently estimated that about 1% of the birth cohort in the United States, or newborns a year, are born with congenital CMV infection. 17 Up to 15% of these babies will have long-term disabilities, most commonly hearing loss but sometimes other kinds of neurodevelopmental disability, including cerebral palsy, mental retardation, seizure disorders, and other kinds of developmental delay. 18 gn 1 Hearing loss is particularly problematic because babies can go on to have congenital CMV-associated hearing loss in early childhood but have normal hearing at birth when they have the routine newborn hearing screen. So that s an important issue for clinicians to be aware of, that passing the newborn hearing screen does not assure that gr that infant s not going to have CMV-associated deafness later on in childhood. go 2 So, a vaccine that could prevent these kinds of disabilities would have a major public health impact. The amount of money that s spent on caring for children with congenital CMV infection every year in the United States is in the billions of dollars. It s a very, very important issue economically, not to mention the devastating psychological and personal impact that it has on families. gp 3 So, recognizing that this is a major public health priority, I wonder if you could comment, Mike, on what we ve learned from CMV vaccine studies that have been done in the past. Have any of these been evaluated in the clinic, and does anything show promise at this stage? gq 4 DR. McVOY: There are two vaccines that have been tested for efficacy in phase 2 trials. The first was a live attenuated vaccine strategy developed back in the 1970s. This vaccine was shown to have some efficacy in transplant settings and was shown to be immunogenic and produce what we gs believed at the time to be desirable neutralizing antibody responses and T cell responses. 19 This vaccine ultimately was tested in the context of preventing primary infection in seronegative women, and showed no efficacy. 20 So, that was quite a 17. See Swanson and Schleiss (2) in List of Supplementary 18. See James and Kimberlin (14) in List of Supplementary 19. See Adler et al (1), Balfour et al (3), Brayman et al (7), Cui et al (9), Jacobson et al (13), Plotkin et al (20), and Plotkin et al (21) in List of Supplementary 20. See Adler et al (2) in List of Supplementary disappointment. Subsequently, a subunit vaccine, glycoprotein B [gb]-based subunit vaccine, was developed and also tested in a phase 2 trial against primary infection in young women. 21 This vaccine showed 50% efficacy, which was encouraging. It was the first time that any experimental CMV vaccine had shown the ability to prevent a CMV infection and alter the natural history of the disease. Unfortunately, 50% was perhaps not adequate for moving forward. Also the antibody responses, the immune responses were relatively short-lived. That vaccine, to my knowledge, is not going forward at least for congenital CMV. It may show some promise in the transplant setting and has been shown to have some efficacy in that setting in another phase 2 trial So what have we learned from this? The gb vaccine was believed to be primarily mediating protection through neutralizing antibody responses. That has really shifted the focus more towards development of new generations of vaccines that will drive more potent, more robust neutralizing antibody responses. Just in recent years new glycoprotein complexes that mediate viral entry into certain cell types but not others have been identified as extremely potent targets for neutralizing antibody responses. It was found that this gb vaccine that showed 50% efficacy really wasn t very potent at inducing this novel neutralizing antibody response. So, in the last 10 years or so there s been a rebirth of CMV vaccine development in the preclinical phase and now we re moving into the early clinical development phase that focuses in large part on neutralizing antibody responses and also incorporating not just glycoprotein B but the new complexes and targets that we are very hopeful will provide greater efficacy than the 50% that we ve achieved so far. DR. GEBALLE: As Mike mentioned, in the transplant setting, we re thinking more in terms of a therapeutic vaccine. I would put on my basic science hat for a moment and point out that CMV is an ancient virus. It s been in the human population for probably 50 million years or so, and it s coevolved with us, and it has many, many different proteins. We used to think it had about 15 different proteins, which is a lot for a human virus. But now we believe there may be more, on the order of 700 and 21. See Pass et al (19) in List of Supplementary 22. See Griffiths et al (12) in List of Supplementary gt hk hl 750, different proteins made. Furthermore, with the T cell response, there are some dominant epitopes. When people have looked, they found that T cells react to many different proteins in CMV. One of the recurring themes in reading the literature on developing vaccines in the herpes world is that we don t really know very often what the protective antigens are. One develops antibodies and T cell responses to many antigens that may not help us particularly. So sorting out the basic biology and immunology of these viruses continues to be a need in the area. 7 DR. SCHLEISS: It s possible to take herpes simplex virus that causes cold sores or genital herpes and test vaccines for that in animal models. You can infect mice or other small animals with the human herpes simplex. But human cytomegalovirus won t infect any other kind of animal. Why is that, Adam? Do you have any insights into why the cytomegalovirus are so species-specific, compared to herpes simplex virus? 8 DR. GEBALLE: There are a number of antiviral factors that our cells have that have evolved in a kind of arms race with the virus. So, the virus has evolved to overcome the host restriction factor, the host restriction factor has evolved to overcome the virus, and so on and so forth. So that the virus that we now have in humans differs to a great extent from even primate CMVs in how these factors bind to each other and how the human restriction factors work. Some of the restriction factors we ve shown in rhesus CMV and African green monkey CMV, for example, are unable to overcome the human defense system that we have. So, therefore the rhesus CMV won t grow in humans. We re learning more about it. A lot of it s coming out of the HIV research, but we understand that there are differences in species that account for some of this restriction of viral replication across species. 9 DR. SCHLEISS: When we think about health issues during pregnancy, most women who are pregnant or considering pregnancy recognize that they should avoid risk factors like alcohol. They should avoid dealing with cat litter because of the risk of an infection called toxoplasmosis. They re aware of the fact that they should take supplemental vitamins to try to prevent neural tube defects. Women are also aware of the risks of Down syndrome and other kinds of genetic problems. But if you take all of these and combine them, it s still a lot fewer babies than are injured by CMV every year. I m wondering, Mike, if you have any thoughts as to why such an important public