Control of HIV-1 by an HLA-B*52:01-C*12:02 Protective Haplotype.

HLA-B*52:01-C*12:02, which is found in approximately 20% of all Japanese persons, is well known to be associated with ulcerative colitis and Takayasu arteritis. This haplotype is also known to be protective in individuals infected with human immunodeficiency virus (HIV) type 1. Recent studies showed that HLA-B*52:01-restricted HIV-1-specific T cells suppress HIV-1 and that HLA-C*12:02 together with KIR2DL2 play an important role in natural killer cell-mediated control of HIV-1. However, the role of HLA-C*12:02-restricted cytotoxic T lymphocytes (CTLs) in suppressing HIV-1 replication remains unknown. In the present study, we demonstrated that HLA-C*12:02-restricted CTLs specific for 2 immunodominant epitopes, Pol IY11 and Nef MY9, contributed to the suppression of HIV-1 replication in HIV-1-infected individuals. Further analysis demonstrated that these 2 HLA-C*12:02-restricted CTLs together with 4 HLA-B*52:01-restricted ones effectively suppressed HIV-1 in individuals with the HLA-B*52:01-C*12:02 haplotype. Thus, both HLA-C*12:02 and HLA-B*52:01 alleles contribute to HIV-1 suppression via both HIV-1-specific CTLs and natural killer cells in individuals with this haplotype.

Distinct HIV-1 escape patterns selected by cytotoxic T cells with identical epitope specificity.

Pol283-8-specific, HLA-B*51:01-restricted, cytotoxic T cells (CTLs) play a critical role in the long-term control of HIV-1 infection. However, these CTLs select for the reverse transcriptase (RT) I135X escape mutation, which may be accumulating in circulating HIV-1 sequences. We investigated the selection of the I135X mutation by CTLs specific for the same epitope but restricted by HLA-B*52:01. We found that Pol283-8-specific, HLA-B*52:01-restricted CTLs were elicited predominantly in chronically HIV-1-infected individuals. These CTLs had a strong ability to suppress the replication of wild-type HIV-1, though this ability was weaker than that of HLA-B*51:01-restricted CTLs. The crystal structure of the HLA-B*52:01-Pol283-8 peptide complex provided clear evidence that HLA-B*52:01 presents the peptide similarly to HLA-B*51:01, ensuring the cross-presentation of this epitope by both alleles. Population level analyses revealed a strong association of HLA-B*51:01 with the I135T mutant and a relatively weaker association of HLA-B*52:01 with several I135X mutants in both Japanese and predominantly Caucasian cohorts. An in vitro viral suppression assay revealed that the HLA-B*52:01-restricted CTLs failed to suppress the replication of the I135X mutant viruses, indicating the selection of these mutants by the CTLs. These results suggest that the different pattern of I135X mutant selection may have resulted from the difference between these two CTLs in the ability to suppress HIV-1 replication.

Selection of escape mutant by HLA-C-restricted HIV-1 Pol-specific cytotoxic T lymphocytes carrying strong ability to suppress HIV-1 replication.

HIV-1 mutants escaping from HLA-A- or HLA-B-restricted CTL have been well studied, but those from HLA-C-restricted CTL have not. Therefore we investigated the ability of HLA-C-restricted CTL to select HIV-1 escape mutants. In the present study, we identified two novel HLA-Cw(*) 1202-restricted Pol-specific CTL epitopes (Pol328-9 and Pol463-10). CTL specific for these epitopes were detected in 25-40% of chronically HIV-1-infected HLA-Cw(*) 1202(+) individuals and had strong abilities to kill HIV-1-infected cells and to suppress HIV-1 replication in vitro, suggesting that these CTL may have the ability to effectively control HIV-1 in some HLA-Cw(*) 1202(+) individuals. Sequence analysis of these epitopes showed that a V-to-A substitution at the 9th position (V9A) of Pol 463-10 was significantly associated with the HLA-Cw(*) 1202 allele and that the V9A mutant was slowly selected in the HLA-Cw(*) 1202(+) individuals. Pol 463-10-specific CTL failed both to kill the V9A virus-infected cells and to suppress replication of the V9A mutant. These results indicate that the V9A mutation was selected as an escape mutant by the Pol463-10-specific CTL. The present study strongly suggests that some HLA-C-restricted CTL have a strong ability to suppress HIV-1 replication so that they can select HIV escape mutants as in the case of HLA-A-restricted or HLA-B-restricted CTL.

Different abilities of escape mutant-specific cytotoxic T cells to suppress replication of escape mutant and wild-type human immunodeficiency virus type 1 in new hosts.

There is much evidence that in human immunodeficiency virus type 1 (HIV-1)-infected individuals, strong cytotoxic T lymphocyte (CTL)-mediated immune pressure results in the selection of HIV-1 mutants that have escaped from wild-type-specific CTLs. If escape mutant-specific CTLs are not elicited in new hosts sharing donor HLA molecules, the transmission of these mutants results in the accumulation of escape mutants in the population. However, whether escape mutant-specific CTLs are definitively not elicited in new hosts sharing donor HLA molecules still remains unclear. A previous study showed that a Y-to-F substitution at the second position (2F) of the Nef138-10 epitope is significantly detected in HLA-A*2402(+) hemophilic donors. Presently, we confirmed that this 2F mutant was an escape mutant by demonstrating strong and weak abilities of Nef138-10-specific CTL clones to suppress replication of the wild-type and 2F mutant viruses, respectively. We demonstrated the existence of the 2F-specific CTLs in three new hosts who had been primarily infected with the 2F mutant. The 2F-specific CTL clones suppressed the replication of both wild-type and mutant viruses. However, the abilities of these clones to suppress replication of the 2F virus were much weaker than those of wild-type-specific and the 2F-specific ones to suppress replication of the wild-type virus. These findings indicate that the 2F mutant is conserved in HIV-1-infected donors having HLA-A*2402, because the 2F-specific CTLs failed to completely suppress the 2F mutant replication and effectively prevented viral reversion in new hosts carrying HLA-A*2402.

Selection of escape mutation by Pol154-162-specific cytotoxic T cells among chronically HIV-1-infected HLA-B*5401-positive individuals.

Most escape mutations have been identified on cytotoxic T lymphocyte (CTL) epitopes presented by Caucasian or African human leukocyte antigen (HLA) class I alleles, whereas a limited number of studies have identified the escape mutations on epitopes presented by Asian alleles. HLA-B54 is a common HLA allele in Asian countries. We recently identified five HLA-B*5401-restricted HIV-1-specific CTL epitopes. We here investigated escape mutations in these CTL epitopes in Japanese HIV-1-infected individuals. The frequency of substitution from Glu (E) to Asp (D) at position 7 (FV9-7D) in the Pol 154-162 (FV9) epitope was significantly higher in HLA-B*5401(+) HIV-infected individuals than in HLA-B*5401(-) individuals, whereas substitutions that were significantly higher in HLA-B*5401(+) individuals than in HLA-B*5401(-) individuals were not found in the other four epitopes. FV9-specific CTLs showed reduced killing activity against target cells pulsed with the FV9-7D mutant peptide and failed to kill those infected with the FV9-7D mutant virus, strongly suggesting that FV9-7D is an escape mutant. Furthermore, longitudinal sequence analysis of the FV9 epitope in two HLA-B*5401(+) individuals revealed that the sequence had changed from the wild type to the FV9-7D during the clinical course. Taken together, these results indicate that the FV9-7D escape mutant had been selected by FV9-specific CTLs among chronically HIV-1-infected HLA-B*5401(+) individuals.