Higher homologous and lower cross-reactive Gag-specific T-cell responses in human immunodeficiency virus type 2 (HIV-2) than in HIV-1 infection.
Human immunodeficiency virus type 2 (HIV-2) infection results in slower CD4(+) T-cell decline, lower plasma viral load levels, and hence slower progression of the disease than does HIV-1 infection. Although the reasons for this are not clear, it is possible that HIV-2 replication is more effectively controlled by host responses. We used aligned pools of overlapping HIV-1 and HIV-2 Gag peptides in an enhanced gamma interferon enzyme-linked immunospot assay to compare the levels of homologous and cross-reactive Gag-specific T-cell responses between HIV-1- and HIV-2-infected patients. HIV-2-infected patients showed broader and stronger homologous Gag-specific T-cell responses than HIV-1-infected patients. In contrast, the cross-reactive T-cell responses in HIV-2-infected patients were both narrower and weaker than those in HIV-1-infected patients, in line with overall weaker correlations between homologous and heterologous T-cell responses among HIV-2-infected patients than among HIV-1-infected patients. Cross-reactive responses in HIV-2-infected patients tended to correlate directly with HIV-1/HIV-2 Gag sequence similarities; this was not found in HIV-1-infected patients. The CD4(+) T-cell counts of HIV-2-infected patients correlated directly with homologous responses and inversely with cross-reactive responses; this was not found in HIV-1-infected patients. Our data support a model whereby high-level HIV-2-specific T-cell responses control the replication of HIV-2, thus limiting viral diversification and priming of HIV-1 cross-reactive T-cell responses over time. However, we cannot exclude the possibility that HIV-2 replication is controlled by other host factors and that HIV-2-specific T-cell responses are better maintained in the context of slow viral divergence and a less damaged immune system. Understanding the nature of immune control of HIV-2 infection could be crucial for HIV vaccine design.
Department of Microbiology, Laboratory of Immunology, Institute of Tropical Medicine, Antwerp, Belgium. wjennes@itg.be
Wim
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Jennes
Makhtar
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Camara
Tandakha
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Dièye
Souleymane
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Mboup
Luc
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Kestens
D000328:Adult; D000595:Amino Acid Sequence; D001530:Belgium / Q000453:epidemiology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D016022:Case-Control Studies; D002478:Cells, Cultured; D015331:Cohort Studies; D003429:Cross Reactions; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D005260:Female; D015683:Gene Products, gag / Q000737:chemistry / Q000276:immunology*; D015658:HIV Infections / Q000097:blood / Q000276:immunology*; D018023:HIV Seronegativity; D015497:HIV-1 / Q000276:immunology*; D015498:HIV-2 / Q000276:immunology*; D006801:Humans; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D012675:Senegal / Q000453:epidemiology; D012680:Sensitivity and Specificity; D013601:T-Lymphocytes / Q000276:immunology*
D000939:Epitopes; D015683:Gene Products, gag; D007371:Interferon-gamma