Studio longitudinale dell'evoluzione del tropismo per X4/R5, dei livelli di HIV-1 DNA cellulare, dei parametri immunologici e della viremia residua in una popolazione di pazienti naive trattati con successo

Abstract

Background: Nowadays HIV-1 RNA levels and CD4+ T lymphocyte counts are the standard markers used in clinical practice for the management of HIV infection. However the evolution of HIV infection can be monitored also by measuring HIV-DNA and this measurement can be determined in PBMCs, even during powerful and prolonged antiretroviral therapy. In successfull treated HIV-1 patients, viral load is undetectable and the strategies for managing long-term side effects may involve a new class of antiretroviral-like CCR5 antagonists. Moreover the dynamics and the influence of viral tropism on the course of HIV-1 infection in subjects exposed to antiretroviral therapy are not fully understood. Then the evolution and determination of HIV-1 tropism based on cellular DNA sequence could be useful for patients with a successfully suppressed plasma viral load. Aims: In this study we aimed to determine whether the HIV-1 tropism for CXCR4 or CCR5 correlates with residual viraemia, cellular HIV-1 DNA load and CD4+ count; moreover, we evaluated if exist a correlation between baseline and follow-up HIV-1 DNA levels with residual viraemia, baseline plasma HIV-1 RNA, and the condition of primary or chronic HIV infection at the start of antiretroviral therapy. Methods: In the CAVeAT, that is a prospective cohort of HIV-infected patients enrolled starting from 2004 in five infectious diseases units in Northeastern Italy (Veneto region), we retrospectively selected two subgroup of patients (cohort I and cohort II); they were a subset of subjects achieving virological suppression within 6 months after initiation of first-line therapy and maintaining plasma HIV RNA levels < 50 copies/ml, without virological failures, until evaluation at the follow-up time points. In order to be included in the our study, the patients needed to be naïve and treated with effective antiretroviral therapy. None of the patients were treated with CCR5 antagonists. The cohort I consisted on 219 patients with median follow-up time of 3 years (T0, T1, T2) while the cohort II was represented of 181 patients with median follow-up times of 4 years (T0, T1, T2, T3). Genotypic analysis of viral tropism was performed on PBMCs throught the sequencing of V3 loop of gp120; the generated sequences were interpreted using the bioinformatic tool Geno2pheno coreceptor while proviral DNA was quantified by Real-Time PCR using TaqMan probes. Results: In the cohort I, HIV-1 DNA, CD4+ count and plasma viraemia were available from all 219 patients at T0 and T1, and in 86 subjects at T2, while tropism determinations were available from 109 subjects at T0, 219 at T1, and from 86 subjects at T2. The results showed that achieving a residual viraemia < 2.5 cp/ml at T1 correlated with having the same condition at T2 and that there was a positive correlation between To and T1 -T2 tropism. X4 tropism at T1 negatively correlated with the possibility of achieving viraemia < 2.5 cp/ml at T2 while a positive correlation between viremic suppression and R5 coreceptor affinity was found. In 181 patients of the cohort II, viroimmunological data were collected at baseline (T0) and at two follow-up time points (T1, T2); in a subgroup of 70 subjects, we evaluated also a third follow-up time point (T3). We observed that high baseline plasma HIV-1 RNA values positive correlated with high levels of HIV-1 DNA at T0, T1, T2, T3 and negative correlated with residual viraemia at T1, T2, T3; having high levels of HIV-1 DNA at T0 positive correlated with high values at T1, T2, T3 and negatively correlated with achieving residual viraemia. Primary infection was associated with lower probability of having high HIV-1 DNA levels at T1, T2, T3 and with a higher probability of achieving residual viraemia at T1 and T3, with respect to chronic infection. Conclusions: The tropism of archived virus was stable during an effective treatment, although a low percentage of patients switched over time. R5 tropism and its stability were related to achieving and maintaining viraemia < 2.5 copies/ml, in treatment responder patients, suggesting a relation among viral tropism and response to treatment in the long term. Moreover, we demonstrated a strong and long-lasting correlation between viral load and cellular HIV-1 DNA before and after the start of HAART and that cellular HIV-1 DNA is closely related to residual viraemia over long-term follow-up of ART responders, particularly when treated during primary infection