Dale and Betty Bumpers Vaccine Research Center National Institute of Allergy and Infectious Diseases National Institutes of Health HIV Vaccines: Basic Science Richard A. Koup, MD 6 th INTEREST Workshop May 9, 2012
Vaccine Research is not Linear Basic Science Clinical Results 1) Overview of clinical results that are driving the direction of HIV vaccine basic science 2) List unanswered questions that are the focus of current basic science efforts
Evidence for CTL Control of HIV Increased CTL activity in long-term non-progressors Rapid escape from CTL responses in acute and chronic infection Increase in SIV viremia with CD8+ T cell depletion Association between appearance of CTL and decline in viremia in acute infection
What Mediates Vaccine induced Protection? VIRUS TYPE OF VACCINE VACCINE INDUCED PROTECTION IMMUNE CONTROL Smallpox Live Antibodies, CTL CTL Rabies Killed virus Antibodies Antibodies, CD4, CTL Vaccine induced antibodies (neutralizing) most commonly protect against viral infections. Polio Live or killed virus Antibodies Antibodies Measles Live Antibodies; CTL Antibodies, CD4, CTL Mumps Live Antibodies Antibodies Rubella Live Antibodies Antibodies Little evidence that T cells actually mediate protection against viral challenge. Varicella zoster Live Antibodies; CTL Antibodies, CTL Influenza Protein Antibodies Antibodies, CD4, CTL Hepatitis A Killed virus Antibodies Antibodies, CD4, CTL Hepatitis B Protein Antibodies Antibodies, CD4, CTL However, once infected, T cells are clearly involved in mediating viral control. HPV VLP Antibodies CD4, CTL Hepatitis C CD4, CTL Cytomegalovirus CD4, CTL Epstein Barr virus CD4, CTL HSV types 1 and 2 CTL HIV 1 and HIV 2 CD4, CTL HHV 6 Antibodies, T cells
Therefore Efforts should be directed towards developing immunogens that stimulate neutralizing antibodies It has been difficult to induce neutralizing antibodies to HIV Variable loops Envelope is heavily glycosylated Shielding of neutralization domains Multiple clades of HIV with only limited crossneutralization Early vaccines generated binding, but not neutralizing, antibodies
Shifting Focus of HIV Vaccines gp160/gp120 subunits Poxvirus vector + protein rad5 gag/pol/nef DNA/rAd5 Env/gag/pol/nef 87 88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 Acquisition effect: 0 31.2% 31.5%? Antibody CD8 T cells Relative focus on vaccine effector mechanisms
RV144: The clinical result that is driving the focus of basic science
Efficacy (mitt) Objective: To carry out a correlates analysis to identify how the vaccine might work (generate hypotheses for further scientific studies)
Correlates Results on Six Assays Variable Relative risk P-value Q-value IgA Binding to Envelope 1.54 0.027 0.08 IgG Avidity A244 gp120 0.81 0.37 0.56 ADCC AE.HIV-1 Infected CD4 Cells 0.92 0.68 0.68 Tier 1 Neutralizing Antibodies 1.37 0.22 0.45 IgG Binding to gp70-v1v2 0.57 0.015 0.08 CD4+ T Cell Intracellular Cytokines 1.09 0.61 0.68 2 individual variables were significant: gp70 V1V2 inversely correlates with infection [q = 0.08] Estimated 43% reduction in infection rate Plasma IgA directly correlates with infection [q = 0.08] Estimated 54% increase in infection rate
Scaffolded gp70 V1V2 Protein V1 V2 alpha4, beta7 interaction motif V1V2 HIV-1 V1V2 His 6 gp70 Scaffold: Murine leukemia Virus gp70 Pinter A, et al. Vaccine 16:1903, 1998
Cumulative Infection Rates With V1V2 gp70 Scaffold Assay Low Medium High
Antibody Binding to Linear Peptides Proteins Loops 1.0 RV144 Vaccinees RV144 Placebos 0.8 0.6 0.4 0.2 0.0 1.0 0.8 0.6 0.4 0.2 0.0
Hypothesis: IgG Binding to gp70 V1V2 as a Surrogate for V2 Specific Neutralizing Antibodies V1V2 forms a beta sheet V1V2/glycan With a long CDR H3 loop V3/glycan Primary interaction with two glycans membrane proximal domain + lipid CD4 binding site gp120 inner domain gp120 outer domain McLellan et al, Nature, 2011 bridging sheet McLellan, Ofek, Zhou, Zhu, Kwong
PG 9/16 like Neutralizing Antibody Binding: C Strand of V1V2 Loop HIV infected RV144 DNA/Ad5
Conclusion: Correlates Analysis RV144 V1V2 binding antibodies correlated with protection This antibody binding maps to where broadly neutralizing PG 9/16 like antibodies bind The hypothesis these results generate is that the mechanism of protection in RV144 was mediated by PG 9/16 like (and potentially other) antibodies that were detected by the V1V2 scaffold assay, but not the neutralizing antibody panel What do we know about other neutralizing antibodies that could be targeted by a vaccine?
Other Neutralizing Antibodies V1V2/glycan V3/glycan Common Features: 1. Long CDR H3 loops Except CD4BS membrane proximal domain + lipid 2. Extensive somatic hypermutation Affinity maturation CD4 binding site gp120 inner domain gp120 outer domain bridging sheet McLellan, Ofek, Zhou, Zhu, Kwong
Neutralizing Activity of Patient Sera Chronic infection 110 HIV+ sera tested against panel of 20 viruses 100 JRFL - Infected > 15 years, stable CD4 - Plasma VL 10 20K - No ART Zhou and Kwong et al. Nature 2007 Percent Neutralization 80 60 40 20 0 10 1 0.1 0.01 IgG concentration (ug/ml) Doria Rose/Connors et al. J Virology 2010;84:1631 Li/Mascola et al, Nat Med 2007;13:1032
Strategy for isolation of new mabs based on HIV epitope specific protein probes After 15 years of infection ~1.5% of B cells recognize gp140, but fewer than 1:2000 are specific for the CD4bs SA-PE X RSC3 (negative) SA-APC RSC3 (positive) Wu et al. Science 2010; 329:856
Broad Neutralization Against Tier 2 Isolates Panel of 190 Luciferase Reporter Viruses Expressing Diverse HIV-1 Envelope Glycoproteins VRC01 b12 gp160 protein distance Neighbor-Joining tree B D IC 50 < 1 μg/ml IC 50 1-50 μg/ml IC 50 > 50 μg/ml HXB2 HXB2 C G Mike Seaman A IC 50 <50 µg 91% 41% IC 50 <1 µg 72% 17% Wu et al. Science 2010; 329:856
Mimicry of CD4 Receptor by Antibody VRC01 gp120 gp120 CD4 VRC01 heavy chain V-domain CD4 and VRC01 in highly similar positions Zhou et al. (2010) Science 329, 811
Other VRC01 like antibodies Different subjects Utilize similar IgG families IgG VH1 2*02 Extensive somatic hypermutation Affinity maturation Divergent primary aa sequences Similar mode of recognition Mimic CD4 Shared epitope target Wu et al, Science, 2011
Identification of VRC PG04 Sequences IAVI Donor 74 (VRC-PG04) VRC-PG04/VRC-PG04b 120,000 VH1-2 sequences Highly mutated > 5000 VRC-PG04 H identity (%) VRC03 VRC01, 02 10 4 10 3 10 2 10 IGHV1-2*02 divergence (%) Wu et al, Science, 2011
Functional Analysis of VRC PG04 Like Heavy Chain Sequences Expressed heavy chain sequences VRC-PG04 H identity (%) % neutralization 100 80 60 40 20 0 WT PG04 0.001 0.01 0.1 1 10 100 ug/ml H chain paired with PG04 light IGHV1-2*02 divergence (%) neutralization no neutralization Demonstration that particular heavy chains can neutralize HIV-1 Design immunogens that drive the antibody response along this pathway Wu et al, Science, 2011
Summary: Neutralizing Antibodies There are several targets for broadly neutralizing antibodies on HIV 1 Env Most share features of long CDR H3 loops and extensive somatic hypermutation New cloning and direct sequencing methods are streamlining the NA discovery effort Demonstrating somatic hypermutation pathways to guide immunogen design How can we induce long CDRH3s and extensive somatic hypermutation through vaccination?
Follicular T Helper Cells: T FH Proliferation of B cells Induction of AID (activation induced deaminase) Leads to somatic hypermutation At what stage of B cell development is the CDRH3 length determined? Nutt and Tarlinton Nature Immunology 12:472-477, 2011
Heavy chain Igs are rearranged by the pre B cell stage, in the bone marrow HCDR3 Length Long HCDR3s are present in naïve B cells, before encounter with antigen QIAGEN
Don t Forget the Other End of the Antibody Can the interactions of the Fc domain with cell and complement receptors contribute to vaccine-induced Ab-mediated protection?
AIDS Vaccine Science A Work in Progress Michelangelo s Unfinished Atlas In the battle between antibody and T cell vaccines, antibodies appear to have won Unanswered questions: 1. Do V2-specific antibodies mediate protection, or are they just a surrogate? 2. If they mediate protection, what is the mechanism: Neutralizing vs nonneutralizing? 3. Can other targets of neutralizing antibodies be exploited in vaccine design? MPER, CD4BS 4. Do we need to induce antibodies with long CDRH3 loops and extensive hypermutation? 5. If so, how do we do that? 6. What is the mechanism of protection by nonneutralizing antibodies? 7. Is the Fc tail involved? 8. How do we induce the correct Fc modifications through vaccination?
Conclusions Correlates of risk have been determined for RV144 V1V2 binding antibodies This correlate raises the hypothesis that V2 directed antibodies mediated the protection in that trial This knowledge is leading to new areas of scientific discovery in HIV vaccine science Other neutralizing antibody targets are known Ab structure and sequence analysis is being applied to guide immunogen design Future trials (HVTN505) will benefit from the experience gained in evaluating RV144
Results from HIV prevention trials Study Length Effect size of Study (CI) HIV Vaccine (Thai RV144) 3.5 y 31% (1, 51) 1% TDF gel (Caprisa, Karim et al.) 2.5 y 39% (6, 60) TDF/FTC PrEP (iprex, Grant et al 2010) 1.2 y 44% (15, 63) 12 mo effect 60 50 Circumcision (Orange Farm, Rakai, Kisumu) 57% (42, 68) 0% 10 20 30 40 50 60 70 80 90 100% Efficacy An HIV vaccine should be considered a component of a comprehensive approach to HIV prevention Prof. Glenda Gray, HVTN Conference, Nov 2010 Padian NS, et al. Weighing the gold in the gold standard: challenges in HIV prevention research. AIDS 2010, 24:621 635
Dale and Betty Bumpers Vaccine Research Center National Institute of Allergy and Infectious Diseases National Institutes of Health Vaccine Research Center Gary Nabel Peter Kwong John Mascola Daniel Douek Robert Seder Immunology Core Bob Bailer & staff Laurie Lamoreaux Collaborators Nelson Michael Jerome Kim Larry Corey Julie McElrath Flow Cytometry Core Mario Roederer & staff Clinical Trials Core Barney Graham Mary Enama & staff Brenda Larkin & staff Contractors Vical GenVec Community Advisory Board Vaccine trial volunteers! www.vrc.nih.gov
Acknowledgements
Acknowledgements University of Washington And 16,402 Thai men and women who participated in the trial