Objectives

To characterize HIV-specific cytotoxic T-lymphocyte (CTL) activities in HIV-2-infected individuals and to relate these to HIV-2 proviral load.

Methods

Peripheral blood mononuclear cells were collected from 16 HIV-2-seropositive and four HIV-1/-2 dually seropositive subjects. CTL were restimulated with autologous phytohaemagglutinin-stimulated blasts and CTL activities in'bulk'cultures were evaluated 7 and 14 days later by a standard 51 Cr-release assay using autologous B-cell lines infected with recombinant vaccinia expressing HIV-2 Gag, Pol or Nef protein. Proviral load was quantified by polymerase chain reaction (PCR) which used HIV-2 long terminal repeat primers and an external standard control made by an HIV-2 CBL-22 chronically infected C8166 cell line. A biotinylated primer was used to capture the 35 S dATP-incorporated secondary PCR product in a quantitative radiometric assay.

Results

After 14 days of culture CTL responses against Gag or Pol protein were seen in 18 (90.0%) and 14 (70.0%) out of 20 subjects, respectively, whereas a CTL response was noted against Nef protein in five (25.0%) out of 20 subjects. In 14 (70.0%) out of 20 subjects multiple HIV proteins were simultaneously recognized. The sum of specific lysis (%) against HIV-2 Gag, Pol and Nef at 30: 1 effector-to-target ratio, or specific lysis of the dominant CTL response, correlated strongly with HIV-2 proviral load expressed as copies per 10 5 CD4+ cells (r=-0.625, P= 0.003 and r=-0.674, P= 0.001, respectively).

Conclusion

HIV-2-specific CTL to multiple gene products was demonstrated in most HIV-2-infected individuals. An inverse correlation between the level of CTL activity and proviral load was found, which supports the hypothesis that CTL are important in the control of HIV-2 replication.