HIV Vaccine Research Dina Kovarik, M.S., Ph.D. Program Manager, NWABR May 16,

The HIV/AIDS Pandemic pg Report on the Global AIDS Epidemic. Executive Summary

Human Immunodeficiency Virus (HIV) Burton et al PNAS 102: gp120 gp41 TM gag tat pol vif vpuvpr rev nef env

Immune Responses to Infection Antigen Presenting Cell (APC, Phagocyte) Virion

Immune Responses to Infection Antigen Presenting Cell (APC, Phagocyte) Virion Kill Infected Cells CD8+ T Cell Killer T Cells

Immune Responses to Infection Antigen Presenting Cell (APC, Phagocyte) Virion B Cell CD8+ T Cell Killer T Cells Antibodies Coat Pathogen Kill Infected Cells

Immune Responses to Infection Antigen Presenting Cell (APC, Phagocyte) Virion B Cell CD4+ T Cell T Helper Cells CD8+ T Cell Killer T Cells

Immune Correlates and HIV Infection CD8+ T Cells Antibodies Neutralizing Abs CD4+ T Cells Weeks Months Years T Cell Count or Antibody Titer RNA Copies per Milliliter Time Post-Infection Peak Virus Load

Y Y X Binding Antibodies (BAbs) Neutralizing Antibodies (NAb) Binding Versus Neutralizing Antibodies Adapted from Wendy Blay Puryear, Ph.D.

Nonhuman primate models for AIDS HIV-1: only replicates in chimpanzees--disease in 10 years Simian Immunodeficiency Virus (SIV): causes AIDS in months to years Simian Human Immunodeficiency Virus (SHIV): chimera with HIV env gene in the backbone of SIV; disease progression similar to SIV Macaca_fascicularis.jpg Macaca nemestrina Macaca fascicularis Macaca mulatta 007/images/0416macaque_lone.jpg

Antibodies and HIV: Passive Transfer Studies Passive transfer of SIV-specific neutralizing antibodies (NAbs) one and 14 days after SIV infection reduced viral load and prolonged healthy life. (Shibata et al Nat Med 5:204) Passive transfer of high-dose NAbs 6 hours before, but not 24 hours after, virus challenge can prevent infection. (Nishimura et al PNAS 100:15131.) Administration of NAbs after infection can accelerate the de novo antibody response. (Haigwood et al J Virol78:5883)

The Role of CD8+ T Cells in HIV Infection A rise in CD8+ T cells early in HIV infection is associated with a reduction in viral load. (Koup et al J Virol 68:4650) A decrease in CD8+ T cells numbers late in HIV infection correlates with an increase in viral load. (Walker et al Nature 328:345; Ogg et al.1998.Science 279:2103.) Depletion of CD8+ T cells in SIV-infected macaques resulted in immediate increases in viral load, while CD8+ T cell restoration resulted in virus control. (Schmitz et al.1999.Science 283:857; Jin et al J Exp Med 189:991.)

If antibodies and T cells protect from HIV infection or disease, why don’t we have an effective HIV vaccine? Timing is everything The devil is in the details

The Power of Immune Memory 1 st Infection2 nd Infection Strength of Response Primary Response Memory Response Vaccination1 st Infection Strength of Response Primary Response Memory Response

The Race to Catch HIV Mattapallil et al Science 434:1093.Brenchley et al J Exp Med 200:749.

But HIV Keeps Running Away… + = patient serum able to neutralize patient virus Virus Time Point Serum Time Point Richman et al PNAS 100:4144.

If antibodies and T cells protect from HIV infection or disease, why don’t we have an effective HIV vaccine? Timing is everything The devil is in the details

Diversity Within the Individual Average 1 mutation per replicated genome Homogeneous new infection Replicates ~ 24hrs Produces new virions a day Rapidly develop a “quasispecies” Wendy Blay Puryear, Ph.D.

HIV-1 Diversity Worldwide HIV-1 group M: - 9 subtypes (>30% difference) - several circulating recombinant forms A B C D F, G, H, J. K CRF01_AE other CRF02_AG CRF03_AB Subtype Hemelaar et al WHO/UNAIDS.

Comparative Genetic Diversity of HIV and Influenza Weiss Nat Med. 9:887, adapted from Korber et al Brit Med Bull 58:19.

Components of a Potentially Successful HIV Vaccine Target multiple HIV antigens –Overcome viral resistance and diversity Cell Mediated Immunity –CD4+ T Helper Cells –CD8+ “Killer” T Cells Humoral Immunity / Antibodies –Binding antibodies  Antibody-dependent cellular cytotoxicity –Neutralizing antibodies (NAbs)  Block infection of target cells

Vaccines in Clinical Use StrategyAgent / Pathogen(s) Live-AttenuatedSmallpoxTuberculosis (BCG) Polio (OPV / Oral, Sabin)Varicella (chickenpox) Measles, Mumps, Rubella (MMR)Yellow Fever Inactivated (Killed)Polio (IPV / injected, Salk)Hepatitis A Virus InfluenzaRabies CholeraPlague ToxoidTetanus toxoidDiphtheria toxin Pertussis toxin Virus-Like ParticlesHepatitis B VirusHuman Papillomavirus (HPV) ComponentHaemophilus influenzae type b (Hib)Pneumococcal conjugate vaccine

A Brief History of HIV Vaccines gp120 gp140 trimers Recombinant Proteins Peptides Moderately Potent NAbs Live Infection Vector Viruses (Adenovirus, Poxvirus) Attenuated HIV Safety (HIV) and Efficacy (Merck) Other Approaches Plasmid DNAVirus-Like Particles (VLPs) Inactivated Virions

Variables in HIV Vaccine Development Vaccine ModalityGeneModelVirus Whole, killedenvMouseSHIV SF162 AttenuatedgagRabbitSHIV 89.6/P DNApolGuinea PigSIVmac239/251 Recombinant ProteinsnefFerretSIV E660 PeptidestatMonkeySIV mne Virus-like particles rev Macaca nemestrina Mimetopesvif Macaca fascicularis Vectors: vpr Macaca mulatta Vaccinia vpu Modified Vaccinia Ankara Fowlpox Canarypox Adenovirus Herpes simplex virus Rabies virus Vesicular Stomatitis Virus Semiliki Forest Virus Adeno-associated virus OPV Salmonella Moloney Leukemia virus Hepatitis B virus Listeria monocytogenes Adapted from Nancy Haigwood, Ph.D. AdjuvantAdminitration AlumDose CytokinesRoute Pulsed DCTiming Co-stimulatory QS-21 CpG oligos PROPRIETARY

Stages of Vaccine Clinical Trials PhaseObjectiveNumber of Volunteers 1Evaluate Vaccine Safety Test Immunogenicity of Vaccine (production of antibodies and/or T cells) and Obtain Additional Safety Information 100s 3Test Effectiveness of Vaccine (i.e. ability to prevent infection and/or disease) 1000s

Clinical HIV Trial Sponsors National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH) –Vaccine Research Center (VRC), –HIV Vaccine Trials Network (HVTN) International AIDS Vaccine Initiative (IAVI) Center for HIV/AIDS Vaccine Immunology (CHAVI) South African AIDS Vaccine Initiative (SAAVI) Pharmexa-EpimmuneAventis-Sanofi Pasteur/ANRS Bavarian NordicTherion Aaron Diamond AIDS Research CenterChrion WyethVaxGen GeoVaxMerck

Endpoints: Prevention of HIV Infection Reduction in Viral Load Maintenance of CD4+ T cells AIDSVAX: Targeting gp120 World’s First Phase III Trial of an AIDS Vaccine N=5,400 in USA, Canada, Netherlands (5,100 MSM) and N=2,500 in Thailand Sponsors: VaxGen, a spin-off of Genetech run by Dr. Don Francis, formerly of the CDC Study Design: VaxGen’s AIDSVAX, two forms of rgp120 from clade B (B/B) or one from clade B and one from clade E (B/E) 0, 1, 6, 12, 18, 24 & 30 months Follow up for 3 years ( ) B B Protective Effectiveness less than 30% (or indeterminant) However, the vaccine was safe, and the trial itself was a success B E Nitayaphan et al J Infect Dis 190:702.

Endpoints: Prevention of HIV Infection Reduction in Viral Load Maintenance of CD4+ T cells Thai Prime-Boost Study N = 16,000 volunteers ages Sponsors: Thai Government, Aventis Pasteur, VaxGen, US Military Study Design: Prominent clade in Thailand is CRF01_AE VaxGen’s AIDSVAX rgp120 from clades B and E 0, 1, 3 & 6 months with ALVAC canarypox vaccine (vCP1521, Aventis Pasteur); contains HIV genes gag, pol, and nef, clade B Co-administer AIDSVAX B/E at 3 and 6 months Started in 2003, 6 year study B E

Thai Prime-Boost Study “We have a concern about the wisdom of the U.S. government’s sponsoring a recently initiated phase III trial in Thailand…Multiple phase I and II clinical trial have revealed that the ALVAC vector is poorly immunogenic. The gp120 component as now been proven in phase III trials in the United States and Thailand to be completely incapable of prevention or ameliorating HIV-1 infection. Society expects the scientific community to develop a vaccine to counter the AIDS pandemic, but there are adverse consequences to conducting large-scale trials of inadequate HIV-1 vaccines…. …One price for repetitive failure could be crucial erosion of confidence by the public and politicians in our capability of developing an effective AIDS vaccine collectively… …The decision about whether or not to proceed with mounting a phase III HIV-1 vaccine trial needs to take into account the likelihood of success and the consequences of failure, the value of what can realistically be learned, and the human and financial costs involved.” Burton et al Science 303:316. Trial Cost: $119 million Cost of rgp120: $3 million 2007 Interim Analysis: No safety concerns Final results expected by the end of 2009.

Endpoints: Prevention of HIV Infection Reduction of Viral Load: Delayed onset of AIDS, reduced transmission V520: The STEP & Phambili Trials N = 3,000 volunteers (STEP, begin in 2004); 801 (Phambili). Sponsors: HIV Vaccine Trials Network (HVTN) & Merck Study Design: Ad5 is a replication-defective adenovirus (common cold virus) Three doses of Clade B Ad5-gag, Ad5-pol & Ad5-nef Doses at 0, 1 and 6 months Target cellular immune responses Started in 2004 Sites: North & South America, Australia (STEP); South Africa (Phambili) STEP Trial Efficacy Analyses: HVTN Full Group Meeting. Nov 7, 2007.

2007 Interim Analysis: Modified intent-to-treat (MITT) population includes all participants who received at least one study injection Per protocol (PP) population includes all participants who received at least the first 2 study injections STEP Interim Analysis VaccinePlacebo Total MITT Cases24 / 741 = 3.2%21 / 762 = 2.8% Cases included in PP Efficacy Analysis19 / 672 = 2.8%11 / 691 = 1.6% STEP Trial Efficacy Analyses: HVTN Full Group Meeting. Nov 7, 2007.

HIV Infection Associated with Pre-existing Ad5 Antibodies Baseline Ad5 Titer Vaccine V Placebo P Relative Incidence (V:P) < 18* > Incidence (%) of HIV Infection MITT Population (males) *Note: 18 is the limit of detection for the Ad5 assay. USA: Approximately half population Ad5+ East Africa: 95% population Ad5+

Immediate Implications for Future Studies: PAVE STEP Partnership for AIDS Vaccine Evaluation (PAVE) Steinbrook NEJM 357:2653.

According to Anthony Fauci, the director of the NIAID, "To be brutally honest with ourselves, we have to leave open the possibility... that we might not ever get a vaccine for HIV. People are afraid to say that because they think it would then indicate that maybe we are giving up. We are not giving up. We are going to push this agenda as aggressively and energetically as we always have. But there is a possibility — a clear finite possibility — that that's the case."

The longest journey begins with a single step, and then another, and then another…. VaccineTime from Bench to Clinic Human Papillomavirus 14 years Rotavirus 15 years MMR (combination vaccine) 16 years FluMist® nasal flu vaccine 27 years Chickenpx (VARIVAX®) 33 years Source: Stefan Kappe, Ph.D. Seattle Biomedical Research Institute Development of Clinical Vaccines

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