Fm Gotch

Loss of the CD56hiCD16− NK cell subset and NK cell interferon-γ production during antiretroviral therapy for HIV-1: partial recovery by human growth hormone

Previous studies have shown that human natural killer (NK) cells are lost from the periphery and are functionally suppressed during HIV‐1 infection, and that the administration of highly active antiretroviral therapy (HAART) results in a recovery of NK cell numbers in HIV‐1‐infected individuals. However, despite this recovery, interleukin (IL)‐2 + IL‐12‐driven interferon (IFN)‐γ production by NK cells has been shown to remain suppressed after HAART. Here we show that the innate immune factor IL‐15 in combination with IL‐12 is also unable to recover NK cell IFN‐γ production in HAART‐treated individuals. Furthermore, we also demonstrate an imbalance in the distribution of CD56loCD16hi and CD56hiCD16– NK subsets after successful HAART, CD56hiCD16– cells being reduced substantially in HIV‐1 patients on HAART. Treatment of patients with combined human growth hormone and antiretroviral therapy resulted in further enhancement in the absolute numbers and the proportion of NK cells in some individuals in the absence of parallel effects on CD4+ T cells. Furthermore, in these individuals HAART with growth hormone resulted in an enhancement of cytokine‐driven NK cell activation and IFN‐γ production compared to the HAART‐only baseline.

Reconstitution of CD4+ T cell responses in HIV-1 infected individuals initiating highly active antiretroviral therapy (HAART) is associated with renewed interleukin-2 production and responsiveness

Reconstitution of functional CD4+ T cell responsiveness to in vitro stimuli is associated with continuous highly active antiretroviral therapy (HAART). Thirty‐six antiretroviral naive patients received HAART over 16 weeks. Antigen‐specific, mitogen and interleukin (IL)‐2 induced lymphocyte proliferative responses and specific IL‐2 and IL‐4 production were assessed at each time‐point, together with quantification of HIV‐1 RNA load and lymphocyte populations. Reconstitution of recall responses was limited largely to persistent antigens such as Herpes simplex virus and Candida, rather than to HIV‐1 or neo‐antigens. Recall antigens, mitogens and IL‐2‐induced renewed responses were associated with in‐vitro production of IL‐2, but not IL‐4. Differential responsiveness to low versus high concentration IL‐2 stimulus increases in a stepwise manner, suggesting normalization of IL‐2 receptor expression and improved functionality. These increases in in‐vitro proliferative responses thus probably reflect short lived effector clones, driven by ongoing antigenic stimulus associated with persisting long‐term organisms. In this context non‐responsiveness to HIV‐1 antigens suggests ongoing HIV‐1 specific clonal T cell anergy.

Evidence of thymic reconstitution after highly active antiretroviral therapy in HIV-1 infection

We aimed to provide evidence of thymic reconstitution after highly active antiretroviral therapy (HAART) in HIV‐1 infected patients and to correlate this with the restoration of peripheral naïve T cells.

A pilot study of the safety and efficacy of thymosin α1 in augmenting immune reconstitution in HIV-infected patients with low CD4 counts taking highly active antiretroviral therapy

To study the safety and efficacy of thymosin α1 in stimulating immune reconstitution in combination with highly active antiretroviral therarpy (HAART), a phase II randomized, controlled open‐label trial of subcutaneous thymosin α1 was undertaken for 12 weeks. Twenty clinically stable patients with viral loads <400 copies/ml and CD4 counts less than 200 cells/µl were randomized to receive 3·2 mg thymosin α1 subcutaneous injections twice weekly or no injections for 12 weeks. CD4 and CD8 counts, CD45 RO+ and RA+ subsets and signal joint T cell receptor excision circles (sjTREC) in peripheral blood mononuclear cells (PBMCs) were measured every 2 weeks. Thirteen patients received thymosin α1 and seven were controls. Thymosin α1 was well tolerated and there were no serious adverse events. There was no significant difference between the thymosin α1 and control groups in CD4, CD8 and CD45 lymphocyte subset changes at week 12; however, PBMC sjTREC levels increased significantly in the thymosin α1‐treated patients compared to controls at week 12. In conclusion, the increase in PBMC sjTREC levels in patients taking thymosin α1 may represent enhanced immune reconstitution; however, the clinical benefits and long‐term consequences remain to be determined.

Alterations in blood leucocyte adhesion molecule profiles in HIV-1 infection

CD4 and CD8 lymphocyte numbers in the gut lamina propria are grossly altered in HIV‐1 infection, out of proportion to alterations in the circulation. Such alterations in lymphocyte counts in the tissues may be due to altered leucocyte migration from the blood. One factor affecting leucocyte migration is adhesion molecule expression. Levels of adhesion molecule expression on peripheral CD4 and CD8 lymphocytes, monocytes and neutrophils from HIV‐1‐infected (AIDS and non‐AIDS) and low‐risk control individuals were compared. CD11a, CD62L, CD44, CD49d and β7 integrin expression were examined by FACS analysis of fresh whole blood. Significant alterations in adhesion molecule expression were detected in HIV infection. The most striking alterations were observed in the CD8 lymphocyte population. CD11a expression was increased and CD62L and CD44 decreased. The CD4 lymphocyte population followed a similar, though less striking, pattern of alteration in adhesion molecule expression. Neutrophils displayed significantly reduced expression of both CD11a and CD62L, but only after onset of AIDS. Monocytes from infected individuals without AIDS displayed a different pattern of altered adhesion molecule expression compared with individuals with AIDS. These findings suggest that in HIV infection, leucocyte functions, such as migration, which require adhesion molecules are abnormal.

CD38 expression on CD8 T cells has a weak association with CD4 T‐cell recovery and is a poor marker of viral replication in HIV‐1‐infected patients on antiretroviral therapy

The aim of the study was to determine whether the expression of CD38 on CD8 T cells can identify patients with virological failure on antiretroviral therapy (ART).

Immunological and virological consequences of patient-directed antiretroviral therapy interruption during chronic HIV-1 infection

Increasing numbers of patients are choosing to interrupt highly active antiretroviral therapy (HAART). We describe the effect of patient‐directed treatment interruption (PDTI) on plasma viral loads (pVL), proviral DNA (pDNA), lymphocyte subsets and immune responses in 24 chronically HIV‐1 infected individuals. Patients were divided into group A with pVL > 50 copies/ml and group B with pVL < 50 copies/ml, prior to the PDTI. pVL rose significantly in group B during the first month off HAART and was associated with a significant decrease in CD4 T‐cell count. At baseline there was a significant difference in HIV‐1 pDNA levels between groups A and B, however, levels significantly increased in group B, but not in group A during PDTI becoming equivalent after 1 month PDTI. We have previously shown no increase in pDNA over the time of substitution in patients switching HAART regimens despite a small rebound in pVL. These observations indicate that to protect low pDNA levels PDTI should be discouraged and that changing regimen at the first sign of failure should be advised where possible. Only transient, no longer than 4 week, HIV‐1‐specific responses were observed during PDTI in 5/24 patients, 2 from group A and 3 from group B. The low numbers of responders and the transient nature of the anti‐HIV‐1 immune responses do not favour the auto‐vaccination hypothesis.

Treatment of primary HIV-1 infection with nonnucleoside reverse transcriptase inhibitor-based therapy is effective and well tolerated

Objectives Highly active antiretroviral therapy (HAART) has been advocated for the management of primary HIV‐1 infection. We investigated the use of a nonnucleoside reverse transcriptase inhibitor (NNRTI)‐based regimen in this setting.

T-cell re-population in HIV-infected children on highly active anti-retroviral therapy (HAART)

In this pilot study, we address the nature of the re‐population of the T‐cell compartment in HIV‐1+ (Human Immunodeficiency Virus 1), vertically infected children placed on successful regimens of HAART (highly active anti‐retroviral therapy) incorporating 2 NRTI and a protease inhibitor. The clonality of the T‐cell compartment and the abundance of RTEs (Recent Thymic Emigrants) were determined 2 weeks before and 20 weeks after initiation of HAART in a subgroup of children taking part in the PENTA (Paediatric European Network for the Treatment of AIDS) 5 trial. Analysis of the clonality of the circulating T‐cell compartment was assessed using CDR3 spectratyping and analysed using the Kolmogorov–Smirnov two sample test. This revealed that a high degree of T‐cell clonal restriction still exists 5 months into therapy, despite the appearance of previously undetectable T‐cell clones within the periphery. We detected no increase in RTE abundance in this 5 month period, as determined by PCR detection of TRECs (T‐Cell Receptor Excision Circles). We conclude that the observed re‐population of T cells within the periphery of treated children is heavily reliant upon the maintenance/expansion of pre‐existing cells during the 5 month period immediately following the initiation of therapy.

Impact of NNRTI compared to PI-based highly active antiretroviral therapy on CCR5 receptor expression, β-chemokines and IL-16 secretion in HIV-1 infection

Summary Interleukin‐16 (IL‐16) and the β‐chemokines (RANTES, monocyte chemotactic protein‐1 (MCP‐1), macrophage inhibitory protein (MIP)‐1α and (MIP)‐1β) are soluble in vitro suppressors of macrophage tropic HIV‐1 strains. The reduction of HIV‐1 RNA plasma levels in late‐stage patients receiving protease inhibitors has been associated with increased concentrations of MIP‐1α, MIP‐1β, RANTES and IL‐16 and a decrease in levels of MCP‐1. We determined plasma levels of MCP‐1, MIP‐1α, MIP‐1β, RANTES and IL‐16 during the first 16 weeks of highly active antiretroviral therapy (HAART) in chronic HIV‐1‐infected patients. Patients were administered one of two therapeutic regimens based on either   a   protease   inhibitor (PI) or   a   non‐nucleoside   reverse   transcriptase    inhibitor (NNRTI).   No differences were seen in the levels of RANTES and IL‐16 over the first 16 weeks of HAART in either treatment group. MCP‐1 decreased significantly in the PI‐treated group over the first 16 weeks of HAART (P = 0·0003). A significant increase was observed in the levels of MIP‐1α and MIP‐1β in the NNRTI cohort (P = 0·0010 and P = 0·0012, respectively). A significant decrease in levels of MIP‐1α and MIP‐1β (P = 0·0015 and P = 0·0299, respectively) was observed over the 16 weeks in the PI cohort. A significant difference was seen when the levels of MIP‐1α and MIP‐1β were compared between the NNRTI and the PI cohorts at week 16 (P = 0·04 and P = 0·05, respectively). Evaluation of CCR5 expression ex vivo revealed no difference between the two treatment groups. Patients were genotyped for CCR5 Δ32 and the incidence of heterozygosity was lower than in the HIV‐1 seronegative controls (3% compared to 19%).