8th Conference on Retroviruses and Opportunistic Infections Chicago, IL - February 4 - 8, 2001

Conf Retroviruses Opportunistic Infect 2001 Feb 4-8; 8:51 (abstract no. 29)

M. Marovich¹, J. Mascola², M. Louder², M. Eller¹, K. Limbach³, R. El Habib⁴, P. Caudrelier⁴, M. Robb¹, J. McNeil¹, D. Birx¹, and S. Frankel^1
1US Military HIV Res. Program, Rockville, MD; ²NIH, Bethesda, MD; ³Virogenetics Corp., Troy, NY; and ⁴Aventis Pasteur, Lyon, France.

BACKGROUND: Recombinant canarypox virus (CP) vectors encoding HIV-1 genes are promising vaccine candidates inducing modest (approximately 40%) CTL responses in vaccinees. Based on prior data using DC to deliver immunogens, we postulate that direct ex vivo targeting of human dendritic cells (DC) could enhance the immunogenicity of vCP205.

METHODS: We generated DC from leukopheresis PBMCs (LP-DC; Thurner, J. Immunol. Methods 1999) in an effort to standardize DC methodology for clinical trials. LP-DC were infected with canarypox virus (lab grade CP and lyophilized vaccine, vCP205). DC were exposed to CP at the immature or mature stage. CP infection, HIV-gene expression, and DC viability and function were monitored using standard methods (immunohistochemistry, flow cytometry, blastogenesis assays, IFN-γ ELISPOTs, ELISA).

RESULTS: Both immature and mature DC could be readily infected with canarypox virus (60% infected). Gag expression was detected within 4 hours and decreased over time, likely reflecting Ag processing and MHC loading. DC viability was maintained above 80%. CP infection induced phenotypic and functional maturational effects in the immature LP-DC population manifest by increased expression of the following molecules: CD25, CD40, class I, HLA-DR, CD80, CD83, CD86 and DC-LAMP. The CP induced maturational effect was, in part, TNF-α mediated and could be blocked using a specific monoclonal antibody against TNF. Interestingly, vCP205 exposed LP-DC induced stronger tetanus specific proliferative responses than unexposed DC and the vectored DC retained full alloreactivity in an MLR. vCP205 pulsed DC also induced HIV Ag- specific CD8+ T cell derived interferon-gamma production.

CONCLUSIONS: Pre-clinical experiments using a reproducible method to generate LP-DC have been performed in an effort to improve the immunogenicity of CP HIV vaccines. The actual vaccine, vCP205, can be used to infect LP-DC, resulting in HIV gene expression and a TNF-α mediated maturation of the exposed DC. Importantly, canarypox virus exposed LP-DC remained functional, with preservation of both alloreactivity and Ag-specific stimulatory capacities.

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Copyright © 2001 - Foundation for Retrovirology and Human Health. Reproduction of this abstract (other than one copy for personal reference) must be cleared through the Foundation for Retrovirology and Human Health. Licensed (AIDSLINE) from National Library of Medicine.