HCV genetic variability: from quasispecies evolution to genotype classification.

HCV is a ssRNA virus belonging to the Flaviviruses and is found worldwide worldwide in humans. Following primary infection, persistent infection develops in more than 85% of cases, which in up to 30% of cases, may progress to liver disease, cirrhosis and hepatocellular carcinoma. The virus presents a high degree of genetic variability owing to the combination of a lack of proofreading by the RNA-dependent RNA polymerase and a high level of viral replication. This genetic variability allows the classification of genotypes, subtypes, isolates and quasispecies to which epidemiological and pathogenetic significance may be associated. The features and biological implications of HCV variability and of quasispecies dynamics in infection transmission, mechanisms of chronicity and resistance to antiviral therapy are discussed.

Tat protein vaccination of cynomolgus macaques influences SHIV-89.6P cy243 epitope variability.

In a previous study we showed that vaccination with the native Tat protein controlled virus replication in five out of seven monkeys against challenge with the simian human immunodeficiency virus (SHIV)-89.6P cy243 and that this protection correlated with T helper (Th)-1 response and cytotoxic T lymphocyte (CTL) activity. To address the evolution of the SHIV-89.6P cy243 both in control and vaccinated infected monkeys, the sequence of the human immunodeficiency virus (HIV)-1 Tat protein and the C2-V3 Env region of the proviral-DNA-derived clones were analyzed in both control and vaccinated but unprotected animals. We also performed analysis of the T cell epitope using a predictive epitope model taking into consideration the phylogeny of the variants. Our results suggest that even though the viral evolution observed in both groups of monkeys was directed toward variations in the major histocompatibility complex (MHC)-I epitopes, in the control animals it was associated with mutational escape of such epitopes. On the contrary, it is possible that viral evolution in the vaccinated monkeys was linked to mutations that arose to keep high the viral fitness. In the vaccinated animals the reduction of epitope variability, obtained prompting the immune system by vaccination and inducing a specific immunological response against virus, was able to reduce the emergence of escape mutants. Thus the intervention of host's selective forces in driving CTL escape mutants and in modulating viral fitness appeared to be different in the two groups of monkeys. We concluded that in the vaccinated unprotected animals, vaccination with the Tat protein induced a broad antiviral response, as demonstrated by the reduced ability to develop escape mutants, which is known to help in the control of viral replication.

Rare HVR1-HCV genotype 1b variants in patients with B non Hodgkin's lymphoma. Comparison with viral sequences detected in cases of lymphoproliferative disorders and B cell compartmentalisation.

We compared the E2-HVR1 region in HCV-1b positive B-NHL cases from a multicenter study with sequences from studies related to lymphoproliferative disorders and B cell compartmentalisation. We found rare and unique mutations both in B-NHL isolates and in cases with lymphoproliferative disorders and lymphocyte infection. These rare mutations could have an important effect on HVR1 region and, as a consequence, on the binding of E2 on CD81, with a possible implication for both antigenic stimulation and HCV entry. In conclusion, the HCV predominants circulating in B-NHL cases seem to be associated with clonal selection of rare variants.

Structural defects and variations in the HIV-1 nef gene from rapid, slow and non-progressor children.

OBJECTIVES: Evaluation of sequence evolution as well as structural defects and mutations of the human immunodeficiency virus-type 1 (HIV-1) nef gene in relation to disease progression in infected children. DESIGN: We examined a large number of nef alleles sequentially derived from perinatally HIV-1-infected children with different rates of disease progression: six non-progressors (NPs), four rapid progressors (RPs), and three slow progressors (SPs). METHODS: Nef alleles (182 total) were isolated from patients' peripheral blood mononuclear cells (PBMCs), sequenced and analysed for their evolutionary pattern, frequency of mutations and occurrence of amino acid variations associated with different stages of disease. RESULTS: The evolution rate of the nef gene apparently correlated with CD4+ decline in all progression groups. Evidence for rapid viral turnover and positive selection for changes were found only in two SPs and two RPs respectively. In NPs, a higher proportion of disrupted sequences and mutations at various functional motifs were observed. Furthermore, NP-derived Nef proteins were often changed at residues localized in the folded core domain at cytotoxic T lymphocytes (CTL) epitopes (E(105), K(106), E(110), Y(132), K(164), and R(200)), while other residues outside the core domain are more often changed in RPs (A(43)) and SPs (N(173) and Y(214)). CONCLUSIONS: Our results suggest a link between nef gene functions and the progression rate in HIV-1-infected children. Moreover, non-progressor-associated variations in the core domain of Nef, together with the genetic analysis, suggest that nef gene evolution is shaped by an effective immune system in these patients.