Current HIV Research - Volume 6, Issue 4, 2008

Objective: To prove intra- and inter-observer's reliability of ultrasound (US) in the assessment of lipoatrophic findings related to the HIV associated Adipose Redistribution Syndrome (HARS). Patients and Methods: In two separated sessions, 2 consecutive measurements of subcutaneous fat thickness (SFT) were performed by each observer at the deepest point of Bichat pad, the dorsal face of arm and the mid thigh for the assessment of facial, brachial and crural lipoatrophy, respectively. We enrolled 20 HIV patients, rotating an experienced and untrained sonologist. The assessments were performed avoiding any stand off pads in the skin and excluding artefacts due to the too abundant quantity of gel to obtaining, with minimal transducer pressure, the best resolution of the reference points. Results: Means of facial, brachial and crural SFT showed no significant differences between the workers. Coefficients of variability (SD/mean x100) were similar for facial (ranges: 4.7-5.2% vs 4.9-5.6%, respectively), brachial (ranges: 5.8- 8.4% vs 9.7-11.2%) and crural SFTs (ranges: 5.9-6% vs 6.2-8.7%). There was greater consistency in the measurements performed by the experienced vs the untrained worker. Inter-observer agreement, assessed through kappa statistic (k) analysis, confirmed increased measurement's agreement in the facial (k ranged from 0.40 to 0.60), brachial (k: 0.23-0.63) and crural SFT assessments (k: 0.58-0.70) from the 1st to 2nd session. Conclusions: US shows low intra observer variability and good inter observer reliability in the assessment of body fat changes related to the HARS. The different degree of consistency by the workers and the improvement of interobserver agreement, suggest to stating a well defined period of training to obtain better US reliability.

An article recently published in this journal argues that the life expectancies (and other mortality statistics) produced by models of the HIV/AIDS epidemic in Southern Africa are inconsistent, and questions their reliability. To demonstrate the argument, the author of that paper derived empirical estimates of several mortality statistics from three different sources of data and, on the grounds that the estimates of life expectancy for 2001 and 2006 are somewhat higher than is typically estimated by projection models, concludes that the empirical evidence supports the theoretical view outlined in that paper. If correct, the reasoning (and its empirical demonstration) could be construed as a strong challenge to a dominant orthodoxy surrounding the estimation of mortality statistics in an era of HIV/AIDS and offering some comfort to governments with low Human Development Indices because of the index's dependence, inter alia, on estimates of life expectancy at birth derived from such models. This paper shows how, on theoretical, methodological and empirical grounds, the reasoning and estimates in the paper are severely flawed, and thus that the conclusions drawn in that paper are unjustified.

Transcription of the integrated HIV provirus is subject to regulation by chromatin organization and must employ host cell transcription factors and chromatin modifying complexes to promote the formation of latency, and then reverse this process to replicate in response to T cell activation. The repressed latent HIV-1 proviral 5' LTR is organized into a defined structure where two de-acetylated and positioned nucleosomes flank the enhancer region, presumably imposing a block to transcriptional initiation and elongation. LTR-associated nucleosomes undergo further histone H3 K9 trimethylation, to cause silencing by recruitment of HP1. In this article, we review current understanding of how the transcriptionally silenced provirus might be established through the function of transcription factors that bind conserved ciselements, including SP1, YY1, NF-κB, CBF-1 and RBF-2 (USF/TFII-I), and propose mechanisms by which factors bound to the repressed LTR can enable reactivation in response to cell signaling.

A good understanding about the structure and function of the envelope glycoprotein (Env) from primary human immunodeficiency virus-1 (HIV-1) isolates is important in facilitating the development of effective neutralizing antibody responses as a component of an effective HIV-1 vaccine. In the current study, the antigenicity of a panel of diverse HIV-1 primary Env from different clades of HIV-1 Group M was analyzed using rabbit sera produced by either 3- or 9-valent gp120 DNA vaccine formulations. Both the 3- and 9-valent gp120 DNA vaccine formulations elicited HIV-1 gp120- specific antibodies in immunized rabbits. However, we observed two levels of primary envelope antigenicity to the same set of rabbit immune sera and that the level of glycosylation, particularly in the V1 loop, may contribute to such diversity. Bioinformatics analysis on the distribution and average number of the N-linked glycosylation sites in all variable regions (V1-V5) was conducted. A linear plot demonstrated that the average number of potential N-glycosylation sites in the V1 and V4 loops correlates to the size of the loop. These data provide further evidence on the complexity of primary HIV-1 Env antigens and offers new insight into the mechanisms that HIV-1 uses to escape protective immune responses.

The feline AIDS model for HIV-1 treatment failed in the 1990s, due to structural features resembling protease inhibitor (PI) resistant HIV-1 variants. Widespread drug-resistance to PIs now invokes the possibility of rescuing feline immunodeficiency virus (FIV) as a model for PI treatment. We here analyzed susceptibility of FIV to second generation PIs, lopinavir, atazanavir, and the structurally unrelated non-peptidic PI tipranavir. We found that FIV protease resembles HIV-1 protease drug resistance mutations limiting binding of lopinavir and atazanavir but not tipranavir. All three PIs were found to inhibit FIV replication in a concentration-dependent manner, but only tipranavir inhibited FIV similarly to HIV-1. This drug inhibited FIV synergistically with ritonavir. Inhibition of protease activity was confirmed by Western blot analysis. In molecular docking simulations, tipranavir displayed energetically favorable interactions with the catalytic cavity of the mature dimeric FIV protease. The calculated hydrogen bond network was similar to that found in HIV-1 protease/ tipranavir complexes and involved atoms in the protein backbone. We also modeled the interaction of tipranavir with an immature protease monomer, suggesting that inhibition of protease dimerization may be a secondary modality for FIV inhibition by tipranavir. In conclusion, tipranavir is the first FDA-approved non-reverse transcriptase inhibitor of HIV-1 to show anti-FIV properties. The tipranavir response by FIV may 1) support the idea of using FIV as a small animal model for PI-resistant HIV-1, thus expanding access to animal AIDS models; and 2) pave the way for development of novel broad-based inhibitors for treatment of drug resistant HIV-1.

VGV-1™, a clinical-grade formulation of bovine thymus nuclear protein (TNP) has been demonstrated to possess anti-viral activity in HIV-1 patients in five clinical trials, one of which was placebo controlled double-blinded. However, to date molecular mechanisms remain to be identified. Using surface plasmon resonance we observed TNP components bind with high affinity to HIV-1 proteins involved in viral entry, gp41 and pg120, as well as the T cell HIV-1 receptor CD4. To identify protein components of TNP, gel electrophoresis was performed followed by tandem mass spectrometry (MS/MS). Searching of bovine protein databases revealed the presence of numerous histones. Further analysis of TNP by immunoaffinity chromatography using gp120 and CD4 molecules as targets followed by gel electrophoresis and MS/MS analysis confirmed these data, demonstrating that H1.1, H2B, H4, and H2A histones are the active component of TNP that bind to HIV envelop glycoprotein and its receptor. To conclusively demonstrate binding of histones to target proteins, we repeated the surface plasmon resonance experiments using commercially available bovine histones and demonstrated high-affinity interaction of histones with gp120, and CD4. The binding of histone proteins to CD4, as well as viral molecules has profound implications for basic understanding of immune functions as well as a possible mechanism of VGV-1 activity in AIDS patients.

Although HIV-1 clade B variants are predominant in Western Europe, non-B subtypes are rapidly spreading, mainly due to immigration from endemic regions. All newly diagnosed HIV-1-infected individuals at a HIV/AIDS clinic in Madrid from 2000 to 2007 were identified. Subtype assignment was based on phylogenetic analysis of pol sequences from plasma specimens collected at first visit. A total of 1,430 newly diagnosed HIV-1 individuals were identified: 902 Spaniards, 232 South Americans, and 162 Africans, among others. The proportion of South-Americans and Africans among diagnosed HIV-1 patients increased from 2000 to 2007 (from 17% to 22% and from 4% to 21%, respectively). Half of diagnosis of HIV-1 in 2007 was in foreigners whereas in previous years Spaniards were predominant. Non-B variants were found in 157 (24%) of the 649 subjects who could be subtyped: 11A, 6C, 2D, 1F2, 13G, 4H, 1J, 3CRF01_AE, 64CRF02_AG, 2CRF03_AB, 3CRF06_cpx, 3CRF10_CD, 7CRF11_cpx, 9CRF12_BF, 9CRF14_BG, 1CRF18_cpx, 1CRF19_cpx, 2CRF31_BC, 10 URF and 5 outgroups. They represented 93%, 14% and 4% of newly-diagnosed HIV-1 Africans, South-Americans and native Spaniards, respectively. Non-B subtypes increased from 9% in 2000 to 32% in 2007, specially among South-Americans (from 11% to 20%) and native Spaniards (from 4% to 10%). Most (75%) were recombinant viruses. The highest number and diversity of HIV-1 variants among natives was observed in 2007. HIV-1 non-B subtypes are increasingly present among newly diagnosed HIV-1 individuals in Madrid, representing a third of cases in 2007, whereas 10% of newly diagnosed HIV-1 native Spaniards had non-B viruses.

To assess the immunodominance patterns of HIV-1-specific cytotoxic T lymphocyte (CTL) responses and the contribution of these responses against the peptides scanning optimal epitopes in chronic infection, we test the HIV-1-specific CTL responses against a panel of 413 overlapping peptides spanning HIV-1 Asian B sequence, including 147 peptides corresponding to optimal clade B epitopes in 49 chronically HIV-1 infected individuals by interferon-γ Elispot assay. A large variation in the recognition of peptides restricted by the same HLA class I allele is presented. Some epitopes are targeted frequently by individuals while other epitopes restricted by the same allele are rarely recognized in our research. HLA-B35 and HLA-A03 rather than other HLA alleles contribute greatly to total virus-specific CTL responses. Furthermore, there is a significant inverse correlation between the total contribution of HIV-1-specific CTL responses restricted by different HLA alleles to virus-specific immune responses and viral load in the individuals during advanced infection (P=0.002, r=-0.549). The peptides targeted by individuals have significantly lower entropy compared with those not targeted but restricted by the same HLA class I alleles (P<0.05) in 49 individuals infected by HIV-1, especially the advanced infection subgroup (P=0.044). These data demonstrate that the consistent immunodominance patterns of HIV-1-specific CTL responses of Chinese HIV-1 infected individuals and an inverse correlation between the relative contribution of responses restricted by HLA alleles and viral load, which indicates the important protective effect of optimal epitopes against slow disease progression even in advanced infection.

In order to adapt African programs for antiretroviral treatment (ART) to children's needs, a good understanding of the unique features of pediatric HIV in Africa and realistic expectations of the results of such programs are crucial. We compared pediatric HIV in African settings to pediatric HIV in Western settings and to adult HIV in African settings. As an illustration, we also compared baseline characteristics and ART-outcomes from 15 African pediatric studies, 11 Western pediatric studies and 15 studies of African adults. Several differences in diagnostic, clinical, immunological and virological characteristics were identified, as well as variations in the most influential factors for disease progression and response to ART. Environmental factors may influence disease progression, mortality, loss to follow-up, adherence and the need to adapt the regimen. Many of the responses to ART are two-phased, the first phase taking longer in children than in adults. The selected African pediatric programs recorded a higher increase in median CD4-percent than the selected Western pediatric programs and a higher increase in CD4-count than the selected African adult programs. Compared to the adult programs, the African pediatric programs had lower drop-out rates, higher reported adherence levels and comparable mortality rates. The Western pediatric programs, however, had the lowest mortality rates. While several challenges complicate comparisons between ART-programs, increased knowledge of the unique features of pediatric HIV in Africa may greatly assist in improving pediatric HIV care on a global level.

The extent of immune restoration in HIV-1 patients on antiretroviral therapy is an important marker of disease progression. In this work, we investigate the dynamics of immune reconstitution and address the question of whether the early response to antiretroviral treatments allows to predict the late immune restoration. We select a cohort of twelve patients on GRT-HAART who achieve virological suppression, but show variable recovery of immune competence. HIV-RNA and CD4+ T cell assessments are used for estimation of the dynamic parameters of an established mathematical model of the viral-immune system interactions. We find that failure in immune reconstitution is associated with an abnormal increase of the death rate of uninfected CD4+ T cells. In contrast, their production rate is up to three times higher than in healthy seronegative individuals. This finding is in line with the view of chronic activation as a major cause of immune depletion. According to non parametric statistics, CD4+ T cell responders and non responders do not show significantly different dynamic parameters. Such result suggests that the employed model does not allow to predict the long term immune reconstitution.

As the number of HIV-1 sequences has increased in the public database and new tools of immunological bioinformatics have become available, making it possible to better understand at a population level how host immune response drives the evolution of HIV-1 envelope (Env). We analyzed 1100 unique full-length envelope sequences and systematically determined positive selection (PS) sites by QUASI analysis and found that PS sites were widely dispersed across Env. The frequency of Env PS sites appears to be relatively stable over time. Moreover, between 25% and 61% of PS sites are shared between subtypes A, B, C, and D, suggesting that host immune responses target the same regions of Env gene across different clades at the population level. Significant correlations were observed between PS sites and Neutralizing antibody (NAb) response, as well as PS sites and Th epitopes. Furthermore, NAb sites in combination with cytotoxic-T lymphocyte (CTL) epitopes and proteasome cleavage sites were also significantly associated with PS sites, suggesting NAb may be the major force driving the evolution of HIV-1 Env. We also identified regions that are free from PS, but heavily targeted by CTL or NAb, implying that functional constraints may be responsible for the lack of positive selection in these regions. These findings should help researchers to identify epitopes or regions of HIV-1 that may aid in designing vaccines.

The incidence of maternal-to-fetal human immunodeficiency virus type 1 (HIV-1) transmission is 25-30% in absence of antiretroviral therapy, and is inversely associated with Human leukocyte antigens (HLA) class-I discordance. Based on our earlier report that mixed lymphocyte reactions (MLR) induce a ribonuclease (RNase) that inhibits HIV-1 replication, we proposed that maternal-fetal alloantigen stimulation activates factors that protect the fetus against vertically- transmitted infections. We investigate here whether the degree of mother-infant HLA discordance associates with the ability to produce anti-HIV-1 alloantigen-stimulated factor (ASF), and affects placental RNases. We also determine whether such HLA association is influenced by the mother's HIV-1 status. Paired maternal and cord blood leukocytes were tested for the induction of ASF by MLR, and typed for HLA-A and -B. The placentas were tested for mRNA expression of three RNases. Neonate anti-mother, but not mother anti-neonate MLR generated supernatants with anti-HIV-1 activity, that was associated with HLA class I discordance. This HLA association was not seen in the HIV-infected cohort. HLA class I discordance was also associated with expression of placental RNase 1. Our findings are consistent with the hypothesis that HLA class I discordance induces expression of RNases in the placenta that contribute to innate host resistance to HIV-1 and other viral infections.