Dual Pressure from Antiretroviral Therapy and Cell-Mediated Immune Response on the Human Immunodeficiency Virus Type 1 Protease Gene

Abstract

Human immunodeficiency virus (HIV)-specific CD8؉ T-lymphocyte pressure can lead to the development of viral escape mutants, with consequent loss of immune control. Antiretroviral drugs also exert selection pressures on HIV, leading to the emergence of drug resistance mutations and increased levels of viral replication. We have determined a minimal epitope of HIV protease, amino acids 76 to 84, towards which a CD8 ؉ T-lymphocyte response is directed. This epitope, which is HLA-A2 restricted, includes two amino acids that commonly mutate (V82A and I84V) in the face of protease inhibitor therapy. Among 29 HIV-infected patients who were treated with protease inhibitors and who had developed resistance to these drugs, we show that the wild-type PR82V 76-84 epitope is commonly recognized by cytotoxic T lymphocytes (CTL) in HLA-A2-positive patients and that the CTL directed to this epitope are of high avidity. In contrast, the mutant PR82A 76-84 epitope is generally not recognized by wild-type-specific CTL, or when recognized it is of low to moderate avidity, suggesting that the protease inhibitor-selected V82A mutation acts both as a CTL and protease inhibitor escape mutant. Paradoxically, the absence of a mutation at position 82 was associated with the presence of a high-avidity CD8 ؉ T-cell response to the wild-type virus sequence. Our results indicate that both HIV type 1-specific CD8 ؉ T cells and antiretroviral drugs provide complex pressures on the same amino acid sequence of the HIV protease gene and, thus, can influence viral sequence evolution.

Induction of T-Cell Immunity to Antiretroviral Drug-Resistant Human Immunodeficiency Virus Type 1

“…Previous studies have mapped immune responses to drugresistant peptides already described for their wild-type counterparts (e.g., M41 M/L, M184 M/V, and V82V/A) in HLA A2-positive individuals (12,27,28). The defining of the HLA Cw*0401-restricted L63P-QI9 epitope, spanning the L63P mutation in HIV-1 protease, is unique in that the wild-type peptide L63L has not been previously described as a class I cytotoxic T lymphocyte (CTL) epitope and we did not detect any responses to this wild-type peptide.…”

“…It may be beneficial if the new protein sequences generated following the development of ARV mutations were recognized as novel T-cell epitopes, potentially providing an immune barrier against the development of resistance. Prior studies have examined the interaction between CD8 T-cell responses and drug resistance in selected patient groups (12,27,28). Three of 52 (primarily HLA A2 positive) individuals from these studies had detectable CD8 T-cell responses to ARV drug-resistant forms of HIV-1 but not against the wild type.…”

Dual Selection Pressure by Drugs and HLA Class I-Restricted Immune Responses on Human Immunodeficiency Virus Type 1 Protease

“…Over the past years, some studies have provided evidence that selection pressure exerted by CTL can interfere with the development of drug resistance mutations (4,16,36,38). Drug-targeted enzymes like the viral PR are exposed to both pharmacological selection pressure and immune response selection exerted by ϩ -T-cell responses on the development of drug mutations or drug-associated polymorphisms in the PR, we analyzed PR sequences from 94 HLA class I-typed HIV-1-positive individuals.…”

“…To assess the influence of HIV-1-specific CD8 ϩ T cells on the development and patterns of drug resistance, we analyzed HIV-1 full-length PR sequences from 94 patients in the context of patients' HLA class I alleles. We could demonstrate that there are positive and negative correlations between drug-associated amino acid substitutions and certain HLA class I alleles in the population, suggesting important interactions between the T-cell-mediated immune response selection and the development of resistance (16,23,28). Biological assays could verify that the observed associations between amino acid substitutions and HLA class I alleles predict epitopes recognized by CD8 ϩ T cells, even if univariate statistical analyses are used.…”

Novel Cytotoxic T-Lymphocyte Escape Mutation by a Three-Amino-Acid Insertion in the Human Immunodeficiency Virus Type 1 p6 Pol and p6 Gag Late Domain Associated with Drug Resistance

“…In HIV patients treated with NRTI, the insertion frequency was 21.2% (35) to 36.4% (17) of viral sequences analyzed in these studies. Various effects of drug resistance mutations on T-cell immunity in HIV-1 infection have been reported (19,39,41), but none on the Pol NL8 epitope and by the STP/APP insertion. When Peters and colleagues inserted the coding sequences of the SPT/APP repeat into HIV-1 NL4-3, the resulting virus exhibited increased resistance to NRTI and increased reverse transcriptase content in the virion, and activity was elevated in the mutant virus, but there was a delay in Gag cleavage and viral particle release (35).…”