Active and Passive Immunization for Avian Influenza Virus Infections

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1 NIAID Active and Passive Immunization for Avian Influenza Virus Infections Kanta Subbarao, MD, MPH Laboratory of Infectious Diseases NIAID, NIH

2 Immortalizing H5 HA-Specific Memory B Cells Collection of PBMC from 4 Vietnamese adults who recovered from H5N1 influenza infection >14 months after onset of illness Memory B cells were seeded cells/well in a 96 U-bottom plate in the presence of CpG (polyclonal activator of memory B cells), EBV, and irradiated mononuclear cells IgG+ memory B cells were isolated by binding to CD22 microbeads, followed by depletion of IgM+, IgD+ and IgA+ cells by FACS Screening of culture supernatants for H5 HA-specific antibodies Cloning of positive cultures by limiting dilution Antibody purification by affinity chromatography

3 Cross-neutralizing activity of H5 hmabs against H5N1 viruses NEUTRALIZING AB TITER AGAINST ANTIBODIES H3N2 HK97 HK03 VN04 JPH05 INA05 A146 mab <10 <10 <10 <10 <10 <10 Sheep anti-sera < FLA5.10 < <10 FLA3.14 < FLD20.19 < FLD21.14 <10 32 > <10 An undetectable titer is assigned a value of <10 Simmons PLoS Medicine 2007

4 Efficacy of Immunoprophylaxis: Survival

5 Immunoprophylaxis: Virus titers Mean virus titer (log 10 TCID 50 /g) *p<0.01 vs D2.2 ** p<0.001 vs D2.2 Lower limit of detection D2.2 FLA3.14 FLA5.10 D2.2 FLA3.14 FLA5.10 D 2 post-infection D 4 post-infection

6 Histopathology in mice challenged with H5N1 virus following immunoprophylaxis Irrelevant MAb D2.2 H5 MAb FLA5.10 MAb D2.2 H5 MAb FLA5.10 MAb D2.2 X100 H5 Mab FLA5.10 X100

7 Histopathological analysis of the lung Ab received Mouse # Normal bronchioles Bronchioles with Lesions Bronchiolar Necrosis D /11 (36%) 7/11 (64%) 7/11 (64%) 2 3/12 (25%) 9/12 (75%) 9/12 (75%) FLA /10 (60%) 4/10 (40%) 4/10 (40%) 2 13/13 (100%) 0/13 (0%) 0/13 (0%) FLA /10 (90%) 1/10 (10%) 0/10 (0%) 2 8/12 (67%) 4/12 (33%) 4/12 (33%)

8 Efficacy of H5 Mabs administered 24, 48 and 72 h after infection with 5LD 50 VN/04

9 Summary of Studies on H5 HA MAbs The technology can be used to generate human MAbs against emerging pathogens In addition to the 4 MAbs described in detail, 7 additional MAbs have been selected The MAbs against the H5 HA had neutralizing activity in vitro and in vivo The MAbs were efficacious in prophylaxis in mice The MAbs were efficacious in therapy in mice against homologous and heterologous viruses, even when administered 72 h after virus infection

10 Implications and Future Studies A cocktail of MAbs could be used for post-exposure prophylaxis or as an adjunct to antiviral therapy Mapping the epitopes to which the MAbs bind Extend preclinical data Proceed with clinical development

11 Options for Vaccines for Pandemic Influenza Principle: Induction of a protective immune response against the hemagglutinin protein. Inactivated vaccine: a reassortant virus containing HA and NA from avian virus (or an antigenically similar Surrogate virus) and internal genes from A/PR/8/34 Live attenuated cold-adapted (ca) vaccine: a reassortant prepared with master ca strain A/Ann Arbor/6/60 used in FluMist Purified expressed HA protein HA expressed in a vectored vaccine e.g. adenovirus DNA vaccine encoding the HA and?other genes from the avian virus

12 Development of Vaccines against Avian Influenza Viruses with Pandemic Potential Correlates of protection are known Antibodies directed against the HA and?na are critical for protection Systemic immune response is strain specific Mucosal immune response provides broader cross protection Cellular immunity for viral clearance Human influenza vaccine experience suggests that the vaccine strain must closely match the circulating strain However, it is not possible to predict which avian influenza strain will cross the species barrier The significance of antigenic drift among avian influenza viruses is not known Avian HAs are poorly immunogenic in humans H5 and H7 HAs may bear a multibasic cleavage site that makes them lethal for poultry and chicken embryos

13 Challenges in the Development of Pandemic Influenza Vaccines Diversity of avian influenza viruses Different subtypes: H1-H16, N1-N9 HPAI vs LPAI Eurasian vs North American lineages among many HA subtypes Antigenic drift caused by natural infection or vaccine use Animal models: mice, ferrets, others? Evaluation of candidate vaccines (safety and immunogenicity are evaluated but efficacy is not) Assays for immunogenicity are not sensitive and not standardized and correlates of protection are not known Avian HAs appear to be poorly immunogenic; high doses or multiple doses of HA or adjuvant are needed Others Biosafety restrictions Lack of reagents for quality control Use of reverse genetics Subbarao & Joseph Nature Rev Imm 2007

14 Goal of a Pandemic Influenza Vaccine To prevent severe illness and death from pandemic influenza and it s complications. An ideal influenza vaccine will induce a rapid systemic and mucosal immune response directed at the HA, NA and conserved internal proteins of the virus protect against a broad range of influenza viruses, within a subtype and across subtypes In practical terms, our goal is to generate a vaccine that rapidly induces a cross-reactive neutralizing antibody response

15 Pandemic Influenza Vaccines Generated by Genetic Reassortment Vaccine donor virus with phenotype of attenuation or high growth in eggs PB2 PB1 PA HA NP NA M NS PB2 PB1 PA HA NP NA M NS Avian influenza virus PB2 PB1 PA HA NP NA M NS Reassortant vaccine virus with phenotype of attenuation or high growth in eggs

16 Live Attenuated Pandemic Influenza Vaccines ts Subtype (# evaluated) ca att Immunogenicity Efficacy Mice Ferrets Mice Ferrets H5 (3) H6 (3) H7 (1) H9 (1)

17 Attenuation In chickens: if HA derived from HPAI In mice: lethality (if relevant) virus replication in respiratory tract In ferrets: virus replication in the respiratory tract

18 The H5N1 ca Reassortant Viruses are not Highly Pathogenic for Chickens Virus # inoculated # died Mean time to death 1997, 2003 and 2004 H5N1 wt days 1997 H5N1 ca H5N1 ca H5N1 ca week-old SPF White Plymouth Rock chickens were inoculated intravenously with a 1:10 dilution of stock virus ( /ml) and observed for 10 days.

19 The 2004 H5N1 ca vaccine candidate is attenuated for mice and does not spread to the brain Lungs Nasal turbinates Brain Mean virus titer in log 10 TCID 50 /g A/VN/2004 (H5N1) wt A/VN/2004 (H5N1) ca H1N1 Beijing/95 ca H3N2 Panama/99 ca Days following virus administration Suguitan PLoS Medicine 2006

20 Immunogenicity In mice and in ferrets Following one dose or two doses Tested against homologous and heterologous viruses

21 Two doses of H5N1 ca vaccines are required to elicit serum neutralizing Ab titers in mice Immunizing virus Doses Geometric mean serum neutralizing Ab titers against indicated virus 1997 wt 2003 wt 2004 wt A/VN/2004 ca A/HK/2003 ca Sera were collected before (prebleed) and 28 days following each dose of vaccine; an undetectable titer is assigned a value of 10

22 ELISA and Nt Ab response to 1 or 2 doses of the 2004 H5N1 ca vaccine # of doses of vaccine s Nt Ab titer vs homologous wt H5N1 virus ELISA Ab titer vs recombinant H5 HA , ,100 Two doses of 10 6 TCID 50 of H5N ca virus was administered i.n. 4 weeks apart Sera were collected before (prebleed) and 28 days following each dose of vaccine; an undetectable titer was assigned a value of 10; prevaccination titers were 10

23 Efficacy In mice and in ferrets Following one dose or two doses Tested against homologous and heterologous viruses Efficacy against lethal challenge Protection from pulmonary replication or systemic spread of challenge virus

24 A Single Dose of H5N1 ca Vaccine Protects Mice from Lethal Challenge with 50, 500 or 5000 LD 50 of Homologous and Heterologous Wild-type H5N1 Viruses H5N wt challenge H5N wt challenge ca 2003 ca 2004 ca ca 2003 ca 2004 ca Percent survival Mock immunized Mock immunized Days following administration of challenge virus Suguitan PLoS Medicine 2006

25 Complete Protection from Pulmonary Replication of wt H5N1 Challenge Viruses is Conferred by 2 doses of the 2004 H5N1 ca Vaccine Single dose Immunization: Two doses Mean virus titer (log 10 TCID 50 /g) Mock H5N1 VN 2004/AA ca H5N wt wt 2003 wt Challenge Virus 2004 wt Vaccine dose: 10 6 TCID 50 per dose 2004 H5N1 ca; Challenge virus dose: 10 5 TCID 50 of wt virus

26 2 Doses of H5N1 ca Vaccines Provide Complete Protection from Pulmonary Replication of Homologous and Heterologous wt H5N1 Viruses 8 Mean virus titer in lungs (log10 TCID50/g) Mock H5N1 97 ca H5N ca H5N ca HK/491/97 HK/213/2003 VN/1203/2004 Indo/5/2005 H5N1 wt Challenge: Homologous Virus Heterologous Virus Suguitan PLoS Medicine 2006

27 Goals of the Pandemic Influenza Vaccine Program Generate and evaluate a library of vaccines against viruses of each subtype (H2, H4-16) to protect humans against pandemic influenza Proceed to clinical trials to evaluate safety, infectivity and immunogenicity in healthy adults Bank sera from vaccinated volunteers to test against avian viruses that emerge in humans Determine the significance of antigenic differences among avian influenza viruses in humans Program: CRADA with MedImmune Vaccines, collaboration with CIR, Johns Hopkins Univ. Approach: Live attenuated vaccines Evaluation: In inpatients

28 Acknowledgements Laura, Amorsolo, Josie, Tomy, Catherine, Celia, and Kim (and Mike) Jack Vaccines: LID: Brian Murphy SEPRL, USDA: David Swayne and Joan Beck MedImmune: George Kemble, Hong Jin, Bin Lu CIR, JHU: Ruth Karron Comparative Medicine Branch, NIAID, NIH MAbs: Antonio Lanzavecchia and Nadia Bernasconi, IRB, Switzerland Cameron Simmons, Oxford Unit, Ho Chi Minh City, VietNam Jerrold Ward, Comparative Medicine Branch, NIAID, NIH Hana Golding and Surender Khurana, CBER, FDA