Loss of HIV-1-derived cytotoxic T lymphocyte epitopes restricted by protective HLA-B alleles during the HIV-1 epidemic.

OBJECTIVE AND DESIGN

HIV-1 is known to adapt to the human immune system, leading to accumulation of escape mutations during the course of infection within an individual. Cross-sectional studies have shown an inverse correlation between the prevalence of human leukocyte antigen (HLA) alleles in a population and the number of cytotoxic T lymphocyte (CTL) escape mutations in epitopes restricted by those HLA alleles. Recently, it was demonstrated that at a population level HIV-1 is adapting to the humoral immune response, which is reflected in an increase in resistance to neutralizing antibodies over time. Here we investigated whether adaptations to cellular immunity have also accumulated during the epidemic.

METHODS

We compared the number of CTL epitopes in HIV-1 strains isolated from individuals who seroconverted at the beginning of the HIV-1 epidemic and from individuals who seroconverted in recent calendar time.

RESULTS

The number of CTL epitopes in HIV-1 variants restricted by the most common HLA alleles in the population did not change significantly during the epidemic. In contrast, we found a significant loss of CTL epitopes restricted by HLA-B alleles associated with a low relative hazard of HIV-1 disease progression during the epidemic. Such a loss was not observed for CTL epitopes restricted by HLA-A alleles.

CONCLUSION

Despite the large degree of HLA polymorphism, HIV-1 has accumulated adaptations to CTL responses within 20 years of the epidemic. The fact that such adaptations are driven by the HLA-B molecules that provide best protection against HIV-1 disease progression has important implications for our understanding of HIV evolution.