Current HIV Research - Volume 7, Issue 3, 2009

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After the infusion of HIV-1 virus into a host cell, RNA is reverse transcribed to dsDNA, which persists intracellular to the infected cell in a variety of forms. Numerous in-house assays have been developed for the quantification of the different cellular HIV-1 DNA forms; these implement conventional or real-time PCR methodology. In this review we discuss recent findings about the longitudinal monitoring of cell-associated HIV-1 DNA in naïve and pre-treated patients, as a marker for clinical progression, treatment initiation and long-term success of HAART. These findings underline the importance of monitoring HIV-1 DNA in clinical practice, in addition to HIV-RNA and CD4+ T Cell counts, for the better assessment of HIV-treatment and disease progression. The lack of a standardized real-time PCR assay is major impediment to more wide-spread HIV-1 DNA monitoring.

The functional impairment of HIV-specific CD4+ T cells during chronic HIV infection is thought to be closely linked to viral replication and to T cell exhaustion. T cell exhaustion in the presence of ongoing antigen exposure is a common feature of chronic viral infection, in which dysfunctional T cells fail to eliminate the virus. Otherwise, antiviral T cell function impairment is a poorly understood mechanism. Increasing evidences show that HIV-specific T lymphocytes up-regulated inducible co-receptors, such as the Cytoxic T Lymphocyte Antigen-4, (CTLA-4, or CD152) and Programmed Death-1 (PD-1) and that blockade of the CD152 or PD-1 pathway restores HIV-specific CD4+ T cell function in HIV infection. This review will focus on finding a possible role for inhibitory receptors on virus-specific CD4+ T cells. The analysis of the role of CD152 and PD-1 in HIV-1 infection could provide important insight into the mechanism of viral induced immune dysfunction and lead to immunotherapeutic strategies to reverse immune suppression in this pathology.

Antiretroviral therapy for HIV/AIDS patients are used globally including in resource-limited settings. Successful outcomes are not always observed and HIV resistance to antiretroviral agents is a major cause of treatment failure. Both primary and secondary drug resistance have been described and reported worldwide. Primary resistance, which presumably means that individuals are infected with drug-resistant virus and secondary resistance typically, means a result of treatment failure. Pathogenesis of resistance of each antiretroviral drugs class differs and depends on the mechanism of action of the drugs. Three main laboratory investigations for diagnosis of treatment failure and HIV drug resistance are HIV RNA level, CD4 cell count, and HIV resistance testing. Management concepts for patients with HIV drug resistance are discussed. Strategies for prevention of HIV resistance emergence include finding cases with acute HIV infection, early detection of virological failure, and behavioral interventions such as adherence and condom usage.

Human Immunodeficiency Virus (HIV) leading to the diseased state Acquired Immunodeficiency syndrome (AIDS) and other Sexually Transmitted Diseases caused by various microorganisms are posing a major threat to humankind. Hence there is an urgent need for controlling its spread. In 2008, about 30 million people are living with HIV infection in the world. Heterosexual transmission particularly affecting woman is driving the epidemic today in many resource poor countries, where most of the infections are occurring. One of the biggest potential for prevention for HIV today lies in a method of using a topical microbicide. Microbicides are applied to vaginal or rectal microbicide surfaces with the goal of preventing or at least significantly reducing the transmission of sexually transmitted infections (STI’s). This article is presented here as an overview of the various HIV transmission and prevention methods, microbicide development pipeline and other important aspects concerned with it.

To determine the outcome of HIV infection in children in a resource-limited setting, a retrospective analysis of a series of 51 pediatric cases from the Serbian cohort of HIV infected patients was performed. Twenty seven patients died in the pre-HAART era, but mono/dual antiretroviral treatment had significantly (p=0.046) prolonged survival. Of the total of 24 HAART-treated patients, 10 had clinical AIDS before HAART initiation. The mean baseline CD4 cell count was 193.9 ± 170.0/mm3. After a mean follow-up of 72.6 ± 44 months, a favorable response was recorded in 62.5%, treatment failure (defined as non-achievement of undetectable viremia) in 20.8%, and a discrepant virological and immunological response (achievement of undetectable viremia but without a rise in CD4 cell counts adequate for age) in 16.7% patients. No patients died, and there were only three hospital admissions after commencing HAART. Five immune restoration inflammatory syndrome episodes were recorded, of which four were due to BCG-osis. Lipodystrophy and hyperlipidemia occurred in 18.2% and 26.3% patients, respectively. We conclude that even in suboptimal facilities, the prognosis of HIV disease among children on HAART may be rather good. The metabolic syndrome seems to emerge as an important issue among long-term surviving children on HAART.

Virakinetics II was designed as an observational, multicenter cohort study conducted in HIV-positive patients treated with NFV-based combinations. Trough (pre-dose) concentrations of NFV+M8 in plasma were determined using a novel ELISA test (NFV TDM-ELISA®) and analyzed using clinical and laboratory parameters. Drug levels were sorted as below, within or above a given interval (<0.8 μg/mL, 0.8-3.5 μg/mL and >3.5 μg/mL, respectively). Longitudinal analysis was performed in a subset of patients who underwent two or more determinations. Ninety patients on NFV-containing HAART were enrolled and 43 were coinfected with HCV and/or HBV. Among coinfected patients, 10 subjects had a clinical or histological diagnosis of cirrhosis. Compared to the HIV-monoinfected, the coinfected patients were significantly older, more treatment-experienced, with higher frequency of lipodystrophy and altered liver function test values (all p values: <0.05). Coinfected patients were also more likely to be on a reduced dose of NFV than monoinfected (p=0.03). No significant difference was observed between the two groups with regard to NFV+M8 trough values and concentration range distribution. Median NFV+M8 Ctrough concentrations were higher in coinfected patients, but without reaching statistical significance (p=0.2). This new ELISA test proved to be a rapid, convenient and reliable tool for assessing NFV+M8 plasma levels in HIV-positive patients. It could be suitable for use within the framework of routine clinical practice even in peripheral centers without specialized laboratories.

During replication, HIV-1 reverse transcriptase lacks proof reading activity and is error prone. In addition APOBEC-driven hypermutation of HIV-1 Gag and Pol genes may generate replication-deficient viral variants with inframe stop codons. Virus variants with several stop codons in the RT gene were identified in a subject with residual HIV- 1 replication during antiretroviral treatment. A role for the T-cell response in the selection of replication-deficient variants was hypothesized. Clonal analysis of HIV-1 DNA and RNA sequences from three sequential blood samples was performed. Moreover, the HIV-1-specific memory CD8+ T-cell response was investigated using a peptide-based cultured ELISPOT assay. The accumulation of HIV-1 variants with stop codons in the Pol gene (from 0% to 100%) was observed in sequential plasma samples. The cultured ELISPOT showed a sustained response to a Pol region downstream from the last stop codon. A more detailed analysis of the Pol region encompassing the detected stop codons showed a strong response to a peptide at the end of the RT region containing stop codons (positions 206 to 220) and including the last stop codon (212). These results suggest a role for a peptide-specific immunologic response in the positive selection of cells expressing the truncated HIV-1 RT and the accumulation of replication-deficient viral variants in plasma. The antigenspecific CD8+ T-cell response could be exploited to redirect the response to HIV-1 infection toward in vivo selection of viral variants with reduced or abolished pathogenicity.

A reversal of key HIV protease mutations against tipranavir has been observed in a patient undergoing a late salvage antiretroviral therapy. Our patient initially introduced tipranavir/ritonavir in absence of an optimized background and novel drug classes, and nevertheless he experienced a virological-immunological benefit. Our report is a contribution to the present debate around the role of each single HIV protease mutation, and the validation of mutational “scores” (like the so-called tipranavir weighted score), to be applied to last-generation protease inhibitor compounds initially targeted on patients with limited, residual therapeutic options.

Mother-to-child transmission during pregnancy provides a unique system for studying the correlation between HLA phenotype and susceptibility to HIV infection. We studied this relationship in a Spanish cohort. We determined frequencies of HLA class I and II alleles in 120 infants born to HIV-infected mothers and 67 HIV-infected mothers. Although there was no statistical difference in the frequency of HLA-B35 between transmitting and non-transmitting mothers, the allele was more frequent in infected children than in uninfected children. HLA-B35 has been consistently reported as a risk factor in the progression to AIDS. In addition, it has been proposed that whether a given allele can confer susceptibility to, or protection against, progression depends on maternal versus paternal inheritance patterns, since the child inherits a virus that reflects the history of CTL encounters of the mother. Our results on vertical HIV transmission combine for the first time the ‘HLA-B35 disadvantage’ and the ‘pattern of inheritance’ theories.

Background: We investigated the virologic and immunologic responses to a mono-class, nucleoside/nucleotide reverse transcriptase inhibitor - combination therapy consisting of tenofovir and zidovudine/lamivudine/abacavir in therapy experienced patients. Methods: Retrospective study of 122 patients. Primary analysis was performed at 48 weeks. Virologic response was defined as viral load levels less than 400 copies/ml. Results: About half of the patients had switched to tenofovir+ zidovudine/lamivudine/abacavir for simplification purposes or toxicity while the other half had experienced virologic failure. 80/122 (66%) responded. Median viral load decreased to 78 copies/ml at week 48; median CD4 count increased to 321 cells/mm3. Of the 42 virologic failures, only 3 patients failed after week 24. 24/35 patients who had been on a non-suppressive zidovudine/lamivudine/abacavir-only regimen at baseline and added tenofovir to intensify, responded. 41/53 patients who switched from any nucleoside reverse transcriptase inhibitor-only regimen improved or maintained suppression. Genotypes were available for 85/122 patients. The only predictor of virologic failure was the combination 41L+210W+215Y/F mutational pattern.16 of the patients who failed on tenofovir+ zidovudine/lamivudine/abacavir therapy selected new primary nucleoside reverse transcriptase inhibitor resistance mutations that they previously did not have. 48/85 (56%) patients with genotype tests had at least 3 (3-10; median 4) nucleoside reverse transcriptase inhibitor resistance-associated mutations in the past. Conclusions: Patients heavily pre-treated with nucleoside analogues may show response to mono-class tenofovir+ zidovudine/ lamivudine/abacavir therapy despite having a history of failure with nucleoside reverse transcriptase inhibitors. Lower baseline viral load, higher baseline CD4 count were significant predictors for response. Archived 41L+210W+215Y/F mutational pattern was significantly associated with non-response.

We recently described that the chloroxoquinolinic ribonucleoside 6-chloro-1,4-dihydro-4-oxo-1-(β-Dribofuranosyl) quinoline-3-carboxylic acid (compound A) inhibits the human immunodeficiency virus type 1 (HIV-1) enzyme reverse transcriptase (RT), and its replication in primary cells. Based on these findings, we performed kinetic studies to investigate the mode of inhibition of compound A and its aglycan analog (compound B). We found that both molecules inhibited RT activity independently of the template/primer used. Nevertheless, compound A was 10-fold more potent than compound B. Compound A inhibited the RNA-dependent DNA polymerase (RDDP) activity of RT with an uncompetitive and a noncompetitive mode of action with respect to dTTP incorporation and to template/primer (TP) uptake, respectively. The kinetic pattern of the inhibition displayed by compound A was probably due to its greater affinity for the ternary complex (RT-TP-dNTP) than the enzyme alone or the binary complex (RT-TP). Besides, by means of molecular modeling, we show that compound A bound on the NNRTI binding pocket of RT. However, our molecule targets such a site by making novel interactions with the enzyme RT, when compared to NNRTIs. These include a hydrogen bridge between the 2'-OH of our compound and the Tyr675 of the enzyme RT's chain B. Therefore, compound A is able to synergize with both a NRTI (AZT-TP) and a NNRTI (efavirenz). Taken together, our results suggest that compound A displays a novel mechanism of action, which may be different from classical NRTIs and NNRTIs.

An increase of the mean corpuscular volume of the red blood cells has been repeatedly described in antiretroviral treated patients. Most commonly macrocytosis was associated with the use of certain nucleoside reverse transcriptase inhibitors. The aim of this study was to analyse if macrocytosis might be a marker of mitochondrial toxicity in antiretrovirally treated HIV-infected patients. Using the 13C-methionine breath test we analysed the hepatic mitochondrial function in vivo in antiretrovirally treated HIV-infected patients with macrocytosis. MCV was significantly negatively correlated to the breath test results. For the first time we could show a significant association between an increase of the mean corpuscular erythrocyte volume by treatment with nucleoside reverse transcriptase inhibitors (NRTI) and the hepatic mitochondrial function in vivo.

CD4 T cell recovery after highly active antiretroviral therapy (HAART) has been reported mostly from developed countries. A retrospective cohort study was conducted among naïve HIV-infected patients initiating HAART between July 1, 2001 and December 31, 2004 at Chiang Mai University, Thailand. We evaluated the CD4 cell count recovery over 4 years among patients initiated HAART at low (CD4 count 51-200 cells/mm3) and very low (CD4 count ≤ 50 cells/mm3) CD4 counts. Of 287 patients, 153 and 134 had low and very low baseline CD4 count, respectively. There were 126 men (43.9%), and the mean age was 34.2 ± 7.9 years. The median baseline CD4 count was 50 cells/mm3 (IQR 25, 104). GPO-VIR® (a combination of lamivudine, stavudine, and nevirapine) was the most common prescribed HAART (262 patients, 91.3%). Overall, the mean CD4 count significantly increased 108 cells/mm3 in the first 6 months after HAART initiation and continued to increase up to 4 years, but in the lesser extent. The overall slope of CD4 count was not significantly different between groups. (p = 0.052) The median time to achieve CD4 count of ≥ 200 cells/mm3 was 6 and 18 months in those with low and very low baseline CD4 count, respectively (p<0.001). By 4 years, 19.9% of patients achieved CD4 count of ≥ 500 cells/mm3. The earlier HAART is initiated among patients with low and very low baseline CD4 count, the sooner the patients will achieve adequate immune status to prevent morbidity and mortality from opportunistic infections.

Shared transmission routes of HCV and HIV mean parenteral HIV/HCV coinfection still occurs, often in resource- limited settings. The extent to which coinfection and treatment impact on morbidity and mortality in HIV/HCV coinfected children remains unknown thus optimal management and treatment is difficult to achieve. Using data from a unique, large, prospective cohort of parenterally HIV/HCV coinfected children in Libya we determine the immunological, virological and clinical profiles of HIV/HCV coinfected children documenting the natural and treated history of parenterally acquired coinfection for the first time in such a large group. 160 parenterally HIV/HCV coinfected children were analysed. Thirty-three (21%) received antiretroviral treatment (ART) for HIV disease during follow-up. In children receiving ART, HIV RNA viral load decreased in two-thirds 6-12 months after initiation. 85% (17/20) experienced a positive immunological response to ART with a median increase in CD4 cell count z-score of 131%%. Half had progressed to moderate or severe immunosuppression and/or moderate or severe clinical symptoms three years after infection. In those who progressed during follow-up, 85% had done so within three years of infection. Children progressing to moderate or severe immunosuppression and/or clinical symptoms were significantly more likely to be receiving ART. This novel investigation of the natural and treated history of parenterally HIV/HCV coinfected children in a large prospectively followed group demonstrates minimal clinical symptoms and immunosuppression to date, despite low prevalence of treatment, and a response to ART similar to vertically HIV-only infected children.