AEGiS-14IAC: Comparisons of cellular immune responses in HIV-1 and HIV-2 infections.

14th International AIDS Conference

Barcelona, Spain - July 7-12, 2002

Comparisons of cellular immune responses in HIV-1 and HIV-2 infections.

Int Conf AIDS 2002 Jul 7-12; 14:(abstract no. A10083)

Jaye A, Sarge-Njie R, Schim van der Loeff M, Todd J, Jallow S, Alabi A, Sabally S, Whittle HC
MRC Laboratories, Banjul, Gambia

OBJECTIVE: To gain insight into mechanisms of long-term non-progression in HIV-2 as few HIV-2 infected individuals progress to AIDS compared to HIV-1infection.

METHODS: We compared the cellular immune responses between the two infections in 35 HIV-2 and 28 HIV-1 asymptomatic subjects who had CD4 counts >20%. We assessed IFN-γ release by peripheral mononuclear cells (PBMC) using the ELISPOT and CTL responses by a standard 51Cr-release assay. T cell helper activity was measured by lymphocyte proliferation to PHA and PPD and to HIV antigens.

RESULTS: Inspite of 20-fold difference in plasma viral load between the two infections (geometric mean of 69,200 copies/ml in HIV-1 and 3,500 copies/ml in HIV-2, p<0.006), the frequencies of CTL reactive to gag and pol were similar in both infections. Forty percent of HIV-1 subjects and 53% of HIV-2 individuals responded to gag, whereas frequency of response to pol was 12% and 24% respectively. The ELISPOT assay for IFN-γ from stimulated cells confirmed the results of the CTL and being a more sensitive assay, the attained frequency of responses were higher than in CTL, where 68% of HIV-1 and 71% of HIV-2 subjects showed significant gag-specific IFN-γ spots forming cells. Responders to pol were 40% of HIV-1 subjects and 38% of HIV-2 individuals. There was also no difference in the frequency of circulating effectors from the fresh peripheral blood lymphocytes and no differences were observed in the CD4 responses to specific HIV proteins or to PPD and PHA. There was an inverse relationship between gag-stimulated IFN-γ response and viral load and in the direct Elispot assay there was tendency for higher viral load association with a greater response.

CONCLUSION: Contrary to widely held views, these results suggest that more vigorous immune responses are not necessarily associated with the non-progression or low plasma viral load in HIV-2 infection.

Keywords: AEGIS, HIV-1, HIV-2, Viral Load, HIV Infections, CD4 Lymphocyte Count, Acquired Immunodeficiency Syndrome, HIV Antigens, HIV, HIV Long-Term Survivors, T-Lymphocytes, immunology

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A10083