Multilayered defense in HLA-B51-associated HIV viral control

Area of Science:

• Immunogenetics
• Virology
• Human retroviruses

Background:

• Polymorphism in the Human Leukocyte Antigen (HLA) region is a major determinant of HIV-1 disease progression.
• The mechanisms by which protective HLA class I alleles, such as HLA-B51, confer beneficial effects on HIV-1 outcome are not fully understood.

Purpose of the Study:

• To investigate the mechanisms of HIV-1 control associated with the HLA-B51 allele.
• To analyze T cell responses and viral immune escape mutations within dominant HLA-B51-restricted epitopes in a controlled HIV-1 cohort.

Main Methods:

• Analysis of a unique cohort of individuals infected with clade B' HIV-1 via contaminated blood to control for variables.
• Comprehensive sequencing of T cell epitopes (Gag327-345/NI9, Pol743-751/LI9, Pol283-289/TI8) to identify mutations.
• Correlation of viral load and CD4+ T cell counts with T cell responses to unmutated and mutated epitopes.

Main Results:

• Mutations within the Gag NI9, Pol LI9, and Pol TI8 epitopes were significantly associated with the HLA-B51 allele.
• A hierarchy of epitope mutation selection was observed, with specific mutations in LI9, TI8, and NI9 epitopes appearing sequentially.
• Control of viral load and higher CD4+ counts were associated with responses to unmutated epitopes, while escape mutations in all three epitopes correlated with poorer outcomes.

Conclusions:

• HLA-B51-associated HIV-1 control is mediated by effective T cell responses against multiple dominant epitopes.
• The development of immune escape mutations in these epitopes can compromise viral control.
• Patients with HLA-B51 may benefit from a multi-layered defense against the emergence of viral escape mutations.