Safety of an HIV Vaccine (AVX101) in HIV Uninfected Volunteers in the United States and South Africa

• Grade IV adverse events [ Time Frame: 1 year ] [ Designated as safety issue: Yes ]
  The sample size at each vaccine dose level was selected such that the stopping rule for not escalating the dose (2 or more vaccine-related Grade IV adverse experiences) would be met with high probability if the true toxicity rate was above 15-20%, and such that dose escalation would occur with high probability if the true toxicity rate was less than 5%.
  
  

• Local and systemic adverse events [ Time Frame: 7 days after each dose ] [ Designated as safety issue: Yes ]
  Reactogenicity assessments were performed for all participants before and after each injection, beginning 25 to 45 minutes post injection and continuing daily for 7 days. Assessments performed included systemic reactogenicity (body temperature, malaise and/or fatigue, myalgia, headache, chills, arthralgia, nausea, vomiting) and local reactogenicity (injection site pain, tenderness, erythema or induration, and axillary lymph node tenderness or enlargement).
  
  
• Binding antibodies by ELISA [ Time Frame: 1 year ] [ Designated as safety issue: No ]
  Binding antibodies to commercially available Gag protein (P55 Gag; Quality Biologicals) were assessed by ELISA using single serum dilutions (1/50 or 1/100) on samples taken at baseline, two weeks after the second and third vaccinations and at the final visit. Samples that were positive in the initial ELISA were tested by endpoint titration ELISA using six 2- to 7-fold serial dilutions of serum beginning at a 1/50 or 1/100 dilution. Magnitude of responses is reported as the difference in optical density (OD) in antigen-containing and non-antigen containing wells at the 1:50 dilution.
  
  
• Chromium release CTL assay [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  A standard 51Cr-release CTL assay was performed on fresh peripheral blood mononuclear cells (PBMC) at baseline and 2 weeks after the second and third vaccinations, using a 50:1 effector to target (E:T) ratio.
  
  
• IFN-gamma ELISpot assay [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  Bulk T cell responses were assessed by IFN-γ ELISpot, using cryopreserved PBMC collected at baseline and 2 weeks after the second and third vaccinations, and stimulated overnight with Gag peptide pools at 200,000 cells per well.
  
  
• Antibodies to VEE virus [ Time Frame: 1 year ] [ Designated as safety issue: No ]
  Neutralizing antibodies to VEE virus were measured in serum obtained at baseline, 2 weeks after the second and third vaccinations and at the final visit.
  
  
• Replication-competent viral vector viremia [ Time Frame: 2 weeks after each vaccine dose ] [ Designated as safety issue: Yes ]
  Any participant who reported a fever greater than 38oC, or other moderate symptoms consistent with a viral illness (e.g. headache or malaise) during the 7 days following vaccination, or neurological symptoms (e.g. nuchal rigidity, ataxia, convulsions, coma, paralysis) within the window of the 2-week post vaccination visit, provided a serum sample to confirm the absence of replication-competent VEE viremia.
  
  
• Lymphoproliferation assay [ Time Frame: 1 year ] [ Designated as safety issue: No ]
  A lymphocyte proliferation assay in response to purified Gag protein and/or Gag peptides was performed on cryopreserved PBMC collected at baseline, 2 weeks after the second and third vaccinations, and at the final visit.
  
  

This study was designed to evaluate the safety and immunogenicity of an alphavirus replicon HIV subtype C gag vaccine. This vaccine utilizes a propagation-defective replicon vector system derived from an attenuated strain of Venezuelan Equine Encephalitis (VEE) virus. The vaccine replicon expresses the gag gene from a South African subtype C isolate of HIV-1.

This study evaluated the AVX101 vaccine in healthy, HIV uninfected volunteers in both the United States and South Africa. Participants will be randomized to receive either vaccine or placebo at study entry and again at Months 1 and 3. The study was originally designed to enroll four groups of participants in both the US and South Africa, with successive groups receiving increasing doses of the vaccine, but was later amended to enroll only two groups. Twelve US participants (US Group 1) were randomized to receive either vaccine or placebo. After a review of initial safety data from this group, 12 South African participants (SA Group 1) were randomized to receive the same vaccine dose as US Group 1 or placebo, while 12 US participants (US Group 2) were randomized to receive the next higher vaccine dose or placebo. Review of safety data from SA Group 1 and US Group 2 was used to inform the decision to begin enrollment into SA Group 2 .

Participants had nine study visits over 12 months. Study visits included clinical evaluation, urine and blood tests, and HIV tests. After each injection, participants were asked to record their temperature and any symptoms each day for 7 days and report them to the clinic staff.