Accumulation of Defective HIV-1 Variants in a Patient with Slow Disease Progression

Stefania      Paolucci; Roberto      Gulminetti; Renato      Maserati; Luca      Dossena; Fausto      Baldanti

Abstract

Viral population in a long term non progressor carrying CRF02-AG HIV-1 virus variants with a truncated RT gene and attenuated virus replication was analyzed.

The proportion of mutant and wild-type RT sequences was determined by clonal analysis of HIV-1 DNA and RNA from blood samples and peripheral blood mononuclear cell (PBMC) culture supernatants. Recombinant HIV-1 strains were generated by reverse genetics to evaluate the replicative capacity of RT variants in PBMC cultures.

HIV-1 RNA and DNA sequences in PBMC cultures showed a mixture of stop codons (RTSTOP), recombinant forms, (RTRF), and full length (RTFL) strains. In plasma, proportion of HIV-1 RNA sequences with a truncated RT gene fluctuated over time (0% in 2005, 100% in 2007 and 8.3% in 2010), while in proviral DNA was constant (96.5% to 100%). Reconstituted RTSTOP strains were unable to replicate in PBMC. However, RTFL strains could trans-complement the loss of function of RTSTOP variants.

In vivo selection of stop codons in the RT gene resulted in the accumulation of replication-defective virus strains. Nevertheless, the observed release of defective viral particles in plasma was probably the result of viral protein complementation between replication-competent and replication-incompetent HIV-1 variants. The divergence in the proportion of RTSTOP and RTFL variants as well as in the mutations pattern to antiretroviral drug resistance between HIV- 1 plasma RNA and PBMC proviral DNA, suggested that circulating lymphocytes expressing full-length RT might be negatively selected for by a specific T-cell response, possibly contributing to the slow progression to AIDS observed in this patient.

Keywords: HIV-1, RT stop codons, viral complementation, viral replication, slow progressor, defective variants, pol mutations, heterozygous, carboxytermints, male bisexual, antiretrovial therapy (ART), drug-resistance, prostease, peripheral blood mononuclear cells (PBMC)