Evolución del virus de la inmunodeficiencia humana tipo 1 (VIH-1), en pacientes no progresores con virus ancestrales

Abstract

The main goal of the project was to study the evolution of the human immunodeficiency virus type 1 (HIV-1) in a group of long term non progressor patients (LTNPs), particulary in a sub-group classified as ancestral. Based on the analysis of the nucleotide sequence in env gen of the viruses of different isolates collected in different geographical areas of Spain, we established a correlation between the genetic distance and the date of the specimen collection. Based on this study, we were able to determine the existence of two distinct groups within LTNPs. First we defined a group of ancestral LTNP patients showing only ancestral nucleotide sequences close in dating to the time of seroconversion; and second group of LTNPs, referred to as modern patients, displaying modern viral dating, with the estimation time of the sequence close to the sampling date. Viral evolution was analyzed using the viral DNA extracted from the PBMCs of eight HIV-1 ancestral LTNPs with an extreme control of their viral replication. Plasma viral load in these patients except for independent blips below 2000 copies/ml, was below the detection limit (<50copies/ml). DNA copies per million of cells were estimated close to 1-55 in these ancestral patients. The Maximum likelihood (ML) phylogenetic trees showed extremely short branch length and, consequently, an extremely low viral evolution from their most recent common ancestor (MRCA). In spite of, we were able to define two groups within the ancestral patients, with different viral evolution: first a group of patients without viral evolution, in which the lack of evolution correlated with the maintenance of a good clinical stage over the time, and a second group of patients characterized by the existence of limited viral evolution that corresponds to clinical deterioration and is mainly caused by the loss of CD4+ T cells over time. The analysis of the complete genome sequencing of viral DNA from these patients showed a large number of genome deletions as a dominant form in the first group of ancestral LTNPs. The presence of these deleted viruses and their contribution to the pathology of the infection are still not clear. However, the existence of fewer deletions in regular progressor patients could indicate their importance in HIV pathogenesis. Furthemore, we detected a high number of hypermutated sequences or escape mutations in the second group of ancestral LTNPs. Analysis of the mutations in these ancestral LTNPs showed a large number of common mutations present in all the patient´s viruses indicating a common origin. In adition, many host factors have been associated with patients having a non progressive HIV-1 infection. The strongest association was found with certain HLA alleles and different Single nucleotide polymorphisms (SNP). Analysis of the host characteristics in the ancestral patients showed at least one, and possibly two, host markers related with non progression. In summary, control of viral replication in ancestral LTNPs was achieved by different combinations of virological and host protective factors.