Correlation between gag-specific CD8 T-cell responses, viral load, and CD4 count in HIV-1 infection is dependent on disease status.

BACKGROUND: It still remains controversial which kind of relationships exist between HIV-1-specific CD8 T-cell responses and HIV RNA load or CD4 count over the course of the infection. This study was designed to investigate the role of HIV-specific CD8 responses in patients with different disease status.

METHODS: Three cohorts of patients were selected according to CD4 count levels: long-term nonprogressors (LTNPs, n = 19), asymptomatic progressors (CD4 counts between 500 and 350 cells/mm(3), n = 14), and progressors (CD4 counts <350 cells/mm(3), n = 23). Six of the LTNPs experiencing a quick loss of CD4 T-cells and another 6 LTNPs with stable CD4 counts were followed up. T-cell responses were studied using interferon (IFN) gamma-ELISpot assay against HIV p24 and 11 pools of HIV-Gag peptides.

RESULTS: No significant differences were found in Gag-specific CD8 responses among the 3 cohorts. However, inverse correlations were identified between CD8 responses and CD4 counts in asymptomatic progressors and between CD4 responses and viral loads in progressors. In addition, the sequential dynamics of CD8 responses in 6 LTNPs showed that with a quick loss of CD4 T-cells around the range of 500 to 300 cells/mm(3), more vigorous CD8 responses were induced simultaneously, and plasma viremia was still kept relatively stable.

CONCLUSIONS: These data suggest that the relationship between CD8 response and viral load or CD4 count is not universally consistent throughout the entire course of HIV-1 infection. Gag-specific CD8 responses may play differential roles in different stages of HIV-1 infection, and the maintenance of a threshold level of CD4 T-cells may contribute to mediate effective HIV-specific responses in natural control of HIV-1 infection.