Immune Activation in HIV-Infected Patients Treated with Different ARV Regimens

Objectives: To evaluate the effects of starting therapy with either Truvada (TVD) or Combivir (CBV) in combination with Efavirenz (EFV) or a boosted Protease Inhibitor (LPV/r, ATV/r, fAPV/r and SQV/r) on clinical, immunological, and virological parameters in HIV-infected antiretroviral (ARV) naive patients. Methods: Twenty-seven patients were prospectively enrolled and received TVD-EFV, 32 TVD-PI/r, 24 CBV-EFV, and 23 CBV-PI/r. Immunovirological analyses were performed at baseline and after 3, 6, 9 and 12 months after initiation of therapy; a full set of data is available for 51 patients. Results: Median CD4+ cell counts and HIV-RNA plasma viremia were comparable in the four groups of patients (TVD-EFV, TVD-PI/r, CBV-EFV, CBV-PI/r) at baseline. At month 12 HIV RNA plasma viremia was <50 cps/ml in all patients. Median CD4 cell counts increases were higher, although not significantly, in CBV-EFV and TVD-EFV patients. Finally, CD8+/CD38+/CDRO+ T lymphocytes were significantly decreased after 12 months of therapy in all patients with, possibly, a faster effect seen in the EFV groups. Conclusions: Immunologic parameters are similarly affected by different ARV combinations, even if EFV-associated immunomodulation might be marginally better.


Introduction
T cell activation is an important parameter for predicting disease progression in HIV-positive, untreated patients independently of HIV viral load and CD4+ T cell counts [1,2].Antiretroviral therapy (ARV) reduces T cell activation, but this parameter may remain abnormally elevated even after years of HIV-RNA undetectability [3,4].Persistent immune activation is associated with a blunted recovery of CD4+ T cells and augmented susceptibility to the development of HIV infection-associated comorbidities [5].
The impairment of a number of immune parameters, involving multiple cell types, characterizes immune activation in HIV patients.Thus, cells expressing HLA-DR, CD25, CD69, and CD70, as well as serum levels of neopterin, tumor necrosis factor receptor type II, and beta2-microglobulin are known to concur to this phenomenon [6,7].The most important, and the best characterized index of immune activation seen in HIV infection is nevertheless the increase of CD8+/CD38+/CD45RO+ T lymphocytes.Increases in these cells are known to be a strong predictor of progression to AIDS independently of CD4 counts [1,8,9] and to predict the likelihood to achieve an optimal suppression of viremia in naïve patients starting therapy [10].CD38 is a multifunctional transmembrane glycoprotein that is up-regulated during the earliest stages of T cell activation [11,12].Deeks and co-workers found that the initiation of antiretroviral therapy during early HIV infection reduces the level of CD8+ T cell activation and, to a lesser degree, also that of CD4+ T cell activation [13].Different HAART combinations may have a different effect on T cell activation markers.We investigated the expression of activation markers in a group of naïve HIV-positive patients start-ing different ARV combinations containing either emtricitabine plus tenofovir fixed-dose combination (Truvada ® , TVD) vs. lamivudine plus zidovudine FDC (Combivir ® , CBV), given with efavirenz (EFV) or a ritonavirboosted protease inhibitor (PI/r).

Study Population
Naïve patients eligible for treatment in 5 partecipating Clinical Centres were selected for this study if treated with one of these four HAART combinations: 1) TVD plus EFV); 2) CBV plus EFV; 3) TVD plus PI/r; 4) CBV plus PI/r.Patients were followed every 3 months after having started the ARV treatment, and were assessed locally for clinical and laboratory parameters.They were also sampled at baseline (pre-treatment) and 3, 6 and 12 months after treatment start for a series of immunological determinations performed centrally at the Immunology Laboratory of the Milano University.The study protocol was approved by local Ethical Committees of participating Clinical Centres and all the patients signed an informed consent before enrolment.

Blood Sample Collection and CD4 T Cell Count
Whole blood was collected by venipuncture in Vacutainer tubes containing EDTA (ethylenediaminetetraacetic acid) (Becton Dickinson, Rutherford, NJ).The absolute numbers of CD4 T cells were determined in fresh blood with an Epics XL-MCL flow cytometer (Beckman Coulter).

Statistical Analysis
Comparisons between the different groups were carried out with two-sided Fisher's exact test.Quantitative continuous variables were normally distributed and comparisons were performed using paired samples T-test.Statistically significant differences were considered those with a p value < 0.05.

Study Population and Clinical Efficacy
One hundred and six HIV-infected, ARV-naïve patients were prospectively enrolled and treated with TVD or CBV in combination with EFV or a PI/r (LPV/r, ATV/r, fAPVr and SQV/r).The baseline characteristics of the 4 groups of patients are shown in Table 1

(a).
Fifty-one individuals have reached 12 months of therapy.EFV-associated skin rash was observed in three of the TVD-and in one of the CBV-treated patients after a few days of starting therapy.Eight patients in the TVD groups (3 TVD-EFV and 5 TVD-PI/r) and 9 patients in the CBV groups (6 CBV-EFV and 3 CBV-PI/r) dropped out of the study; in only two cases (1 TVD: acute pancreatitis; 1 CBV: leucopenia) the drop-out was due to serious adverse events (SAE), as shown in Table 1

(b).
Clinical, immunological and virologic parameters at baseline and after 12 months of therapy are presented here in the individuals who reached 12 months of therapy.Median CD4+ cell counts and percentages as well as HIV-RNA plasma viremia were comparable in the four groups at baseline.

Discussion
During HIV infection, a state of chronic, generalized immune activation is a key determinant of CD4+ T cell depletion and progression to AIDS [5].The role of immune activation in HIV infection has generally received less attention than HIV-associated immune deficiency even if recently, immune activation has had renewed attention being a strong, and independent predictor of clinical progression to AIDS [1,8,9].Reduction of immune activation predicts CD4+ T cell increase after ARV better than virus suppression [14].In the study herein we attempted to verify whether the use of different ARV results in a diverse effect on immune activation.An optimal suppression of HIV viremia was achieved Copyright © 2012 SciRes.WJA at month 12 in patients receiving both EFV or PI/r-based ARV in association with either TVD or CBV, some differences were nevertheless seen when immune parameters were examined.Thus, whereas CD4 counts were significantly increased compared to baseline in patients undergoing all 4 types of ARV, the increases were more impressive in both groups of individuals receiving EFVbased therapies.Additionally, although all types of ARV were associated with a significant reduction of CD8+/ CD38+/CD45RO+ cells after 12 months of therapy, this effect was possibly faster in individuals undergoing EFVbased therapies.Notably, no differences were seen between baseline and 12 months of therapy in any of the other cell populations examined that are known to be part of the "immuno-activatory phenotype".The observation that circulating CD8+/CD38+/CD45RO+ T lymphocytes were reduced in all groups of patients after 12 months of therapy confirms the potency of modern day antiretroviral regimens.The observation that such reduction was possibly more precocious in EFVreceiving individuals allows to speculate that EFV-based therapeutic regimens could be associated with a more favourable immunomodulatory effect.Notably, these results confirm recently published data showing reduced immunoactivation, as measured by the percentage of circulating CD8+/CD38+ T cells after 6 months of therapy, in EFV compared to PI/r-treated individuals [15].
Results from the large SMART trial, which evaluated the strategy of interrupting ART in a large population of more than 5000 HIV-infected individuals, clearly showed that the relative risk of non-AIDS-related clinical events is associated with inflammation and immune activation [16,17].Our data, although preliminary, suggest a clinical benefit of EFV-based therapies that would be associated with their possibly earlier ability to down-modulate immune activation.
causes including: moved to another center, changed treatment, pregnancy, others.