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Volume 9 Supplement 2

AIDS Vaccine 2012

Safety and immunogenicity of a randomized phase I prime-boost trial with ALVAC-HIV (vCP205) and gp160 MN/LAI-2 adjuvanted in alum or polyphosphazene


ALVAC-HIV prime/HIV-1 Env protein boost regimens have shown HIV-specific neutralizing antibody (NAb) and cell-mediated immune responses, but the impact of protein subunit schedule and adjuvant requires further definition.


A Phase 1 trial was conducted in two parts. In Part A, (open-label) 19 volunteers received oligomeric gp160 MN/LAI-2 (ogp160) with a dose escalation (25, 50, 100 μg). In Part B, 72 volunteers (60 active, 12 placebo) received placebo or recombinant canarypox expressing HIV-1 antigens, (ALVAC-HIV, vCP205) prime with different doses and schedules of ogp160MN/LAI-2 in alum or polyphosphazene (PCPP).


The vaccines were safe and well tolerated with no vaccine-related serious adverse events. Cumulative chromium release CTL frequency was 37%, and 54% of volunteers showed proliferative responses to HIV antigens. Lymphoproliferative CD4+, HIV-specific responses were seen in 53% of ogp160 only and 57% of prime-boost recipients, respectively. Induced binding antibody to ogp160 was dose-dependent. NAb responses to vaccine homologous Tier 1 HIV-1 MN were seen in 99% of vaccine recipients. While NAb to the heterologous Tier 2 US-1 (R5, clade B) pseudovirus was negative in all volunteers tested using TZM-bl cells, in a PBMC-based assay, US-1 primary isolate Nab was induced in 2/19 (10.5%) recipients of ogp160 protein alone and in 5/30 (16.7%) prime-boost volunteers who received ogp160 in PCPP. Primary isolate neutralization was observed more frequently overall in recipients of ogp160 in PCPP, as compared with alum (p=0.027). Using an intracellular p24 flow-cytometry assay, sera from an ALVAC-HIV/ogp160 recipient demonstrated 94% neutralization of US-1.


A small percentage of vaccine recipients developed Nab to heterologous primary isolates, responses that to our knowledge have not been previously described. These results constitute proof of concept that Tier 2 NAb can be elicited by vaccination in humans, and underscore the importance of further optimization of prime-boost vaccination and adjuvanting strategies for HIV-1 prevention.

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Correspondence to RJ O'Connell.

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This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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O'Connell, R., Polonis, V., Ratto-Kim, S. et al. Safety and immunogenicity of a randomized phase I prime-boost trial with ALVAC-HIV (vCP205) and gp160 MN/LAI-2 adjuvanted in alum or polyphosphazene. Retrovirology 9, O50 (2012).

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  • Primary Isolate
  • Vaccine Recipient
  • Chromium Release
  • Adjuvanting Strategy
  • Boost Regimen