Background:

Differential protein targeting by HIV-specific CD8 T cells is associated with disparate plasma viral loads; however, it is unclear if the quality of these responses differs depending upon the specificity of the targeted epitopes.

Methods:

We examined HIV-specific CD8 T-cell responses in HIV-infected adolescents carrying either an HLA class I allele associated with a favorable prognosis (HLA-B* 57) or an allele associated with usual disease progression (HLA-B* 35 or HLA-B* 53) using interferon-γ ELISpot and ICS assays.

Results:

In an interferon-γ ELISpot assay, p24 was the dominant protein targeted by B* 57 carriers while responses to Nef dominated in B* 35 or B* 53 positive carriers. This differential protein targeting did not change during 4 years of follow-up. In these chronically infected adolescents, there were no significant differences in the quality of the immunodominant T-cell responses between the B* 57 and B* 35/B* 53 carriers as measured by peptide avidity, degranulation, and immune memory markers. There was a trend towards higher expression of interleukin-2 from B* 57-KF11 restricted CD8 T cells although this difference was not significant. Nevertheless both B* 57 and B* 35/53-restricted responses were relatively potent as reflected by the propensity of CD8 T cells to escape in p24 and Nef, respectively.

Conclusions:

Differential protein targeting rather than the quality of T-cell responses appears to be a major distinguishing feature of HIV-specific CD8 T cells induced in B* 57 carriers. These data suggest that viral fitness costs associated with CD8 T-cell pressure is an important factor determining differences in the viral load among HIV-infected patients.