Introduction: HIV type-1 (HIV-1) protease (PR) and cleavage site (CS) mutations accumulate in protease-inhibitor-resistant isolates. HIV-1 CS mutation 431V is the most frequent treatment-associated CS mutation; however, little is known about its origin in treatment-naive HIV-1 isolates. Recently, it has been shown that the CS mutation 431V is located within the human leukocyte antigen (HLA)-B*13-restricted cytotoxic T-lymphocyte (CTL) epitope RQANFLGKI (RI9). Therefore, we investigated whether the presence of CS mutation 431V might additionally be related to immune escape.
Methods: CTL recognition of RI9 and of RI9 variants carrying the 431V or the 436R mutation was analysed by ELISPOT in nine HLA-B*13-positive HIV-1-infected patients. Treatment-naive HIV-1-infected patients with primary drug-resistant HIV-1 isolates (n=58) or carrying 431V (n=4) were genotyped for HLA class I alleles.
Results: ELISPOT analysis showed different patterns of CTL recognition of RI9. CS mutation 431V could abrogate recognition by RI9-specific CTL in a subgroup of patients. Nevertheless, in our study, the occurrence of 431V in treatment-naive HIV-1 without primary drug resistance could not be explained by HLA-B*13-mediated immune selection. In patients with primary drug-resistant HIV-1 isolates, the frequency of HLA-B*13 was not increased and HLA-B*13 did not correlate with CS mutations 436R or 431V.
Conclusions: HIV-1 CS mutation 431V can abrogate CTL recognition, indicating interactions between development of drug resistance and the CTL response. However, we could not find evidence that the presence of 431V in treatment-naive HIV-1 isolates with and without primary drug resistance is related to immune selection by HLA-B*13 or other HLA class I alleles.