Current HIV Research - Volume 5, Issue 4, 2007

AIDS has claimed the lives of 25 million people worldwide, an additional 40 million people are HIV-infected and new cases are being diagnosed every year. Despite the fact that HAART has moved AIDS from the category of terminal diseases to that of treatable chronic illnesses, its long-term therapeutic success may be compromised by the development of resistance to the currently used drugs. Despite the availability of RT, PR and fusion inhibitors, the development of further drugs such as inhibitors that target the third enzyme IN is essential for the clinical management of HIV-infected patients. The absence of cellular homolgues to IN and the unique nature of the reactions catalyzed by IN, make it an ideal target for drug design. Considerable progress towards designing HIV-1 IN inhibitors has been made over the last years and several lead compounds have been identified, synthesized and clinically studied. This review focuses on the existing knowledge of the biology of HIV-1 IN with emphasis on the mechanism of integration, structure and function and the technologies for measuring IN activity. This is followed by the current trends on designing HIV-1 IN inhibitors with the aid of molecular informatics and a review on the main classes of HIV-1 IN inhibitors reported this far with special emphasis on the clinical candidates.

Nucleoside reverse transcriptase inhibitors used in antiretroviral therapy may cause mitochondrial toxicity. Mitochondrial dysfunction leads to disturbance of the glucose metabolism, resulting in an accumulation of L-lactate. We tested the hypothesis that an oral glucose tolerance test (OGTT) can be used to detect mitochondrial toxicity in patients on antiretroviral nucleoside analogues. An OGTT was performed in 30 subjects: 16 HIV-infected treated patients without adverse events (group 1) and 14 HIV-infected patients with adverse events related to nucleoside reverse transcriptase inhibitor- induced mitochondrial toxicity (group 2). Lactate was measured at baseline and 60 and 120 min after glucose loading. At all time points the lactate levels were higher in the adverse events group compared to the other group, with the highest levels of lactate at t = 60 min (mean 1912 μmol/L, SD ± 609); mean lactates in the group without adverse events was 1429 μmol/L (SD ± 464). When levels above the upper limit of normal of 1800 μmol/L were used as an indication for mitochondrial toxicity, the sensitivity and specificity were 57% and 81%, respectively. The area under the ROC curve was 0.75. For L-lactate levels > 2000 μmol/L the specificity was 90%. An OGTT with measurement of lactate at baseline and one hour after glucose loading can detect (occult) hyperlactataemia in patients with mitochondrial impairment. From our study we suggest to perform an OGTT as an additional test in patients with symptoms suspect for adverse events to discern mitochondrial toxicity.

Measuring virion infectivity is critical for studying and monitoring the process of HIV-1 infection. The easiest and the most common method utilizes reporter cell lines based on the HIV LTR promoter. The early HIV gene product Tat amplifies expression from the LTR; however, there is a background transcriptional activity that is independent of Tat. Furthermore, LTR activity can be influenced by cellular activation states. We have recently constructed a Rev-dependent expression vector, and as a test of this construct's functionality, we have integrated this vector into a continuous T cell line. This novel indicator cell has no measurable background signal, is not affected by elevated metabolic states, and yet responds robustly to the presence of HIV. The line is able to complete TCID50 assays in 3-5 days, and appears sensitive to both CCR5- and CXCR4-utilizing viruses.

With the advent of Highly-Active-Anti-Retroviral-Therapy (HAART), HIV patients can expect to live beyond 10-15 years following diagnosis. An unexpected result of increased survival is the emergence of opportunistic, oncogenic virus-associated cancers such as Burkitt's lymphoma (Epstein-Barr Virus), cervical cancer (Human Papilloma Virus) and Kaposi's sarcoma (Kaposi's sarcoma-associated herpesvirus) in this immuno-compromised population. Furthermore, there are reports of colorectal cancers (CRC) in long-term HIV-AIDS survivors. Compared to the general, non-immunocompromised population, long-term AIDS patients have 4 and 3.3-fold increased risk of developing colorectal and anorectal cancer respectively. Unlike oncogenic virus-associated cancers, CRC is not known to have a viral etiology. Our study aimed to investigate one aspect of HIV infection and colorectal carcinogenesis. We proposed that the HIV transactivator protein Tat; a protein with known oncogenic properties that is secreted and can re-enter non-infected cells may have a role in CRC. Using two CRC cell lines, LIM1215 and LIM2537 we found that Tat inhibits epithelial cyto-differentiation, blocks apoptosis in vitro and accelerates tumour formation in vivo. In addition, Tat significantly increases in vitro migration in the absence of foetal calf serum. These properties underpin CRC, and as HIV infection is initiated in the gut lymphoid system, these data provide a basis for the increased incidence of CRC in long term AIDS patients.

The antimicrobial peptide LL-37 is the only cathelicidin that has been described in humans. LL-37 exerts chemotactic, immunomodulatory and angiogenic effects; activities that are mediated through binding to the formyl peptide receptor like (FPRL)-1 receptor. Agonistic ligation of FPRL-1 can also induce down-regulation of HIV-1 chemokine receptors and reduce susceptibility to HIV-1 infection in vitro. Therefore, we have evaluated the capacity of LL-37 to inhibit HIV-1 infection in vitro. Here we demonstrate that LL-37 inhibits HIV-1 replication in PBMC, including primary CD4+ T cells. This inhibition was readily reproduced using various HIV-1 isolates without detectable changes in the target cell expression of HIV-1 chemokine receptors. Accordingly, the HIV-1 inhibitory effect was shown to be independent of FPRL-1 signalling. Given the epithelial expression of LL-37, it may contribute to the local protection against HIV-1 infection.

In sub-Saharan Africa, approximately 1 in 2 HIV-1-infected persons living in a couple have a serodiscordant partner. Recent data suggest a large proportion of new HIV-1 infections in mature epidemics occur within discordant couples, making discordancy a major contributor to the spread of HIV/AIDS in Africa. What accounts for high rates of HIV-1 discordance and why some individuals remain uninfected despite repeated sexual exposure to HIV-1 is unknown. Studying HIV-1-discordant couples may contribute to understanding correlates of HIV-1 immunity and acute infection. Additionally, HIV-1-discordant couples are an important population for prevention efforts. Consequently, HIV-1-discordant couples are increasingly viewed as a valuable source of participants for HIV vaccine and prevention trials. This review summarizes and critiques existing data on HIV-1-discordant couples in developing countries, including an analysis of transmission rates within discordant couples, description of biological and behavioral characteristics important in planning HIV-1 vaccine and prevention trials, and challenges faced when carrying out such studies.

This study assessed the relationship between changes in CD4 T-cell count, HIV Viral Load (VL) level and evolutionary patterns in Antiretroviral (ARV) resistance mutations of circulating HIV in those with persistent viraemia despite treatment. The study examined the dynamics of change in resistance mutations to explore potential predictors of evolution in the circulating virus over a prolonged period. Four longitudinal blood samples from 29 HIV-infected Australian patients at RPAH are analysed for the presence of genotypically resistant HIV virus. The subjects had CD4 cells counts (40-670 cells/mm3), VL levels (1.7-5.7 log10 copies/ml), drug resistance mutations, and had been treated with ARV regimens for varying periods between February 1998 and June 2005 (i.e., 88 months). Parametric and nonparametric tests were used to examine changes in CD4 T-cell counts and VL levels, and in frequencies of mutations at different sample points. Nonparametric LOESS fitting curves were used to analyse changes in CD4 T-cell counts and VL levels. During the study period, changes in mean values of CD4 cell counts and VL levels in patients displaying an evolving genotypic resistance profile differed from those without evidence of an evolving mutational pattern; applied for both Reverse- Transcriptase (RT) and Protease (PR) gene profiles. In patients with Evolution-of-Resistance (EoR) at the RT site, there was a significant decrease in mean CD4 cell count during the first 36 months (-194 cells/mm3, P=0.0466) but no significant change in the last 52 months or thereafter (-10 cells/mm3, P=0.8464). Conversely, in patients with EoR at the PR site, there was no significant change in mean CD4 cell count during the first 36 months (-30 cells/mm3, P=0.6187) but a significant decrease (-155 cells/mm3, P=0.0348) thereafter. In patients without EoR at the RT site, there was no significant change in mean CD4 count during the first 36 months (-12 cells/mm3, P=0.8371), however, a significant increase in mean CD4 cell count occurred thereafter (+242 cells/mm3, P=0.0077). Similarly, in patients without EoR at the PR site there was no significant change in mean CD4 count during the first 36 months (-19 cells/mm3, P=0.6647) and there was a significant increase in the last 52 months (+145 cells/mm3, P=0.0348). The only significant decrease in mean value of VL levels occurred in patients without EoR associated with NRTIs thereafter (-1.33 log10 copies/ml, P=0.0477), while no significant changes in mean value of VL levels in patients with/without EoR associated with any ARV drugs at any other time points (-0.65 to +0.15 log10 copies/ml, P=0.1855 to 0.7958). Low CD4 cell counts (<250 cells/mm3) and high VL levels (>4.50 log10 copies/ml) in the early stage of HIV infection, a significant decrease in CD4 cell counts during the first 36 months (-50 or more cells/mm3), and high frequencies of mutations during the first 36 months of antiretroviral regimen (>3 mutations) emerged as potential predictive factors of EoR associated with NRTI/PRI agents thereafter. Stable VL in the first 36 months correlated with lack of lability of resistance mutations thereafter.

A HIV-infected patient treated since eight years with all antiretroviral classes save boosted protease inhibitors, at the time of changing therapy due to an emerging genotyping resistance to non-nucleoside reverse transcriptase inhibitors, experienced repeated episodes of hypersensitivity reactions to all available boosted protease inhibitors. After documenting a combined ritonavir and lopinavir hypersensitivity by means of a specific in vitro cellular antigen stimulation test (CAST), antiretroviral therapy was safely continued with unboosted atazanavir. According to our knowledge, we report the first case of application of the in vitro CAST assay to antiretroviral intolerance, and the subsequent, specific regimen selection in a HIV-infected subject who showed multiple allergy to all boosted protease inhibitors. Further, controlled investigation is strongly needed to implement in vitro allergometric testing in patients with HIV infection and related diseases, who are prone to show unpredictable drug intolerance reactions. In fact, HIV-infected patients may suffer from frequent allergic drug reactions which may be difficult to be systematically recognized (due to the frequent, multiple concurrent pharmacotherapy), while eventual drug rechallenges are expected to be potentially dangerous.