Current HIV Research - Volume 6, Issue 2, 2008

The multidomain HIV-1 Vif protein recruits several cellular partners to achieve neutralization of the antiviral activity of APOBEC3 proteins. Vif neutralizes APOBEC3G and APOBEC3F predominantly by forming an E3 ubiquitin ligase with Cullin5, ElonginB and ElonginC that targets these proteins for degradation by the ubiquitin-proteasome pathway. Vif associates with the Cullin5-ElonginB-ElonginC complex by binding directly to ElonginC via its SOCS-box motif and to Cullin5 via hydrophobic residues within a zinc-binding region formed by a conserved HCCH motif. The HIV-1 Vif-Cullin5-ElonginBC complex is then able to ubiquitinate the APOBEC3G factor bound to Vif by its N-terminal domain. In this review, we summarize the current knowledge about the structural determinants of Vif that allow it to interact with cellular and viral partners.

To describe characteristics and prognosis of patients with suboptimal immunological response to combined antiretroviral therapy (CART). Using data from a multicenter cohort study, we selected patients who initiated CART and showed suboptimal CD4-T cell response (defined as <50 cells/L increase) after 1 year of therapy, despite sustained virological suppression. Characteristics of those patients were compared with subjects who showed optimal immunological response. Of 650 patients with virological suppression, 108 (16.6%) showed suboptimal CD4-T cell response. Independent predictors of suboptimal response were previous injection drug use (OR, 1.85; 95% CI, 1.12-2.98) and age at CART initiation (OR, 1.04 per year increase; 95%CI, 1.01-1.06). Hepatitis C virus coinfection was not associated with impaired inmunological response. As compared with patients with optimal immunological response, those with suboptimal response had a higher mortality rate (3.22 versus 0.71 per 100 person-years; p=.001), but a similar rate of new AIDSdefining events. In patients with sustained virological suppression with CART, previous injection drug use, but not hepatitis C virus coinfection, and older age at initiation of therapy were associated with suboptimal CD4 T-cell responses. Patients with suboptimal response had a higher mortality over time, mainly due to diseases other than AIDS-defining events.

The Asian HIV epidemic appears to be complex, characterized by the prevalence of multiple subtypes and circulating recombinant forms with gradual replacement of pure HIV-1 subtypes in several geographical regions. The main objectives of the present study are to identify and analyse the full-length viral genomes of three unique recombinant forms (URFs); the HIV-1 isolates 07MYKLD47, 07MYKLD48 and 07MYKLD49 from Malaysia. Long-range polymerase chain reaction (PCR) amplification of seven overlapping reading frames was used to derive near full-length HIV-1 genomes. Detailed phylogenetic and bootscanning analyses were performed to determine phylogenetic associations and subtypic assignments. We further confirmed the mosaic composition of these CRF01_AE/B inter-subtype recombinant forms, which are composed of B-subtype fragment(s) in the backbone of CRF01_AE. Both 07MYKLD47 and 07MYKLD48 have an insertion of B subtype (880 bp and 532 bp) in the gag-pol and gp41-env gene regions, respectively. Whereas the isolate 07MYKLD49 has three B-subtype fragments inserted in different gene region along the genome; one each in the gag-pol (1862 bp) and pol-vif (1935 bp) regions, and a short B-subtype insertion (541 bp) in the 5' LTR-gag region. This highlights the public health relevance of newly emerging second generation HIV-1 recombinant forms and their dispersal, along with their rapid and continuous evolution in the region.

The human immunodeficiency virus (HIV) Nef protein is myristoylated and plays a critical role in AIDS pathogenesis by enhancing viral replication, survival of the virus within infected cells and by facilitating its spread in vivo. We observed that, in the promonocytic cell line U937, myristoylated exogenous Nef protein activates NF-κB and AP-1, whereas unmyristoylated exogenous Nef protein does not. Using methyl-β-cyclodextrin (MβC) treatment, we observed that the activation of NF-κB and AP-1 by exogenous Nef protein is mediated primarily via lipid rafts both in U937 cells and in primary human macrophages. In agreement with this observation, exogenous Nef protein colocalized with GM1 ganglioside, a major component of lipid rafts, in U937 cells as detected by confocal microscopy. Since tumor necrosis factor alpha (TNF

α) activates NF-κB and AP-1, we investigated the role of exogenous Nef protein in TNFα-stimulated U937 cells and primary macrophages. We observed that exogenous Nef and TNFα synergistically activate NF-κB and AP-1 in U937 cells and primary macrophages resulting in enhanced stimulation of the HIV-1 long terminal repeat (LTR), and subsequently in enhanced viral replication in both chronically infected promonocytic U1 cells and acutely HIV-1-infected primary macrophages. Both enhanced LTR stimulation and viral replication following treatment with exogenous Nef and TNFα were mediated via lipid rafts. Therefore, our results indicate that exogenous Nef protein and enhanced TNFα production detected in HIV-infected subjects could synergize to fuel the progression of the disease via lipid raft-dependent stimulation of the HIV-1 provirus present in such cellular reservoirs as mononuclear phagocytes.

Previous studies have demonstrated that nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs) act as chemical enhancers of human immunodeficiency virus type 1 (HIV-1) RT dimerization. In the current study, we sought to define the role of key residues (101, 103, 108, 181, 188, 190, 225 and 318) in the NNRTI-binding pocket on HIV-1 RT heterodimer stability. Thirteen mutant RTs were constructed and evaluated for p66/p51 RT heterodimer formation using the well-established yeast two-hybrid assay. We found that the mutations K101A, P225H, Y318F and Y318W decreased RT heterodimer stability whereas K103N, V108I, V108W, Y181C, Y188L, G190A, G190E, G190W and P225W increased RT heterodimer stability. While these results demonstrate that residues that comprise the NNRTI-binding pocket contribute to the stability of p66/p51 HIV-1 RT, they did not suggest any obvious correlation between RT dimer stability and the extent of NNRTI resistance. Remarkably, mutations at residue G190 (A, E, W) in the p66 RT subunit were found to dramatically increase heterodimer stability. Notably, the G190W mutation increased RT dimer stability almost to the same extent as did 5 μM efavirenz. In light of these findings, we characterized the in vitro activity of recombinant RT expressing mutations at G190 in the p66 subunit only and compared them with a wild-type enzyme complexed with efavirenz. We found that while mutations at G190 had a significant effect on both the DNA polymerase and ribonuclease H activity of the enzyme, their phenotypic effects did not mirror those induced by efavirenz-binding to RT.

We assessed the correlation between HIV-RNA viral load in blood (BPVL) and seminal plasma (SPVL) in a cross-sectional cohort of 119 asymptomatic, antiretroviral-naive and experienced HIV-1 subjects (BPVL < 50 copies/mL for minimum 12 months and stable on one drug regimen). The cohort was divided into 3 groups: 2 according to the non nucleoside reverse transcriptase inhibitor (NNRTI) and protease inhibitor (PI) used, and 1 untreated group. At the initial visit, subjects were screened for gonorrhoea, chlamydia and syphilis. Blood was collected for CD4 count, BPVL, and general biochemistry and haematology. Semen was collected concurrently and SPVL determined by the NucliSens® HIV- 1 QT PCR (BioMerieux, Boxtel, The Netherlands). At a subsequent visit, a second semen sample was obtained and SPVL was repeated for 10 subjects on ART. All NNRTI subjects (n = 36, mean treatment 33 months ± 14) and PI subjects (n = 45, mean treatment 31 months ± 25) had BPVL < 50 copies/mL and SPVL < 250 copies/mL at baseline and with repeat sampling. 9/119 subjects (8%) had an asymptomatic STI; 4 cases in the treated groups and 5 in the untreated group. Treated subjects were less likely to have an STI than untreated subjects. In conclusion, asymptomatic STIs had no effect on BPVL or SPVL in either treated group and SPVL remains undetectable over time. STIs minimally increase, or do not increase, SPVL in untreated patients. Our data supports the role of ART in lowering the risk of sexual transmission of HIV-1.

Since the outbreak of the HIV epidemic in the 1980s, various organisations and researchers have produced statistics on HIV/AIDS including HIV prevalence, incidence, number of AIDS cases, AIDS-related mortality as well as life expectancy at birth in the context of HIV/AIDS. Until recently HIV-prevalence statistics as well as models projecting the impact of HIV/AIDS utilised HIV-prevalence statistics based on women attending antenatal clinics as population-based prevalence statistics were non-existent. Among others, the extrapolation of HIV-prevalence statistics from surveillance sites to the general population has been questioned. Recent statistics on HIV-prevalence from population-based surveys strongly suggest that HIV-prevalence in many countries may not be as high as earlier estimated and projected. In addition, model estimates of HIV/AIDS-prevalence and impact on mortality often use conventional model life tables such as the Coale-Demeny Regional, UN, and Brass standard life tables, which in the case of South Africa give female life expectancy at birth plummeting from about 65 years in the mid-1990s to around 49-50 years in 2005. The standard life tables often employed in these estimates do not take account of the ‘hump’ in the mortality curve due to AIDS-related deaths as these standard mortality schedules were developed prior to the HIV/AIDS epidemic. Given this background, this paper provides a critical look at recent statistics on infant mortality rates and life expectancies at birth in the context of HIV/AIDS in parts of Southern and Eastern Africa with particular reference to South Africa.

An ex vivo trial utilizing photopheresis with Benzoporphyrin Derivative as the photoactive compound, identified the minimum energy levels of light and concentrations of BPD that eradicated both cell-free and cell-associated HIV- 1 infectivity without destroying the virus particles or infected leukocytes. Leukocytes remained viable with altered chemokine/cytokine expression. Apoptosis was induced in a minority of CD4 but not CD8 positive cells with a statistically significant increase in cytolytic T-cell activity. In the 24 week clinical trial in 7 HIV-1 infected patients, three who had rapidly rising viral loads prior to initiating therapy stabilized. Two had a sustained greater than 0.5 log decrement and 5 had stable plasma viral loads (less than a 0.5 log increment or decrement) with varied effects on absolute CD4 and CD8 positive lymphocytes counts. One achieved a greater than 1 log decrement in HIV-1 plasma viral load and undetectable in vivo cell-free and cell-associated HIV-1 infectivity with an increased in vitro lymphocyte mitogen stimulation index. Under amended protocol, 5 additional 12 month courses were administered to three additional patients and two of the previous enrollees. Area under the curve for viral load showed a significant decrease from pre- to post-therapy (p 0.007). No associated toxicities were observed.

Adherence to highly active antiretroviral therapy (HAART) has been scarcely studied in correctional settings. Our study aims to evaluate the relationship between adherence and virological outcome and to determine factors related to adherence in correctional settings. A cross-sectional retrospective study was performed in Topas prison (Salamanca, Spain). 50 inmates starting HAART were studied. Adherence was estimated through a self-report questionnaire and variables related to adherence (covering individual factors, the illness itself and the therapeutic regimen) were recorded. HIVRNA levels and CD4 lymphocyte count were measured before starting therapy and six months after. Statistical analysis was performed using univariate and multivariate methods. 21 inmates (42%) were considered adherent and 29 (58%) were non-adherent. Adherence to treatment, as measured by our questionnaire, was the only significant and independent factor associated with an undetectable viral load at six months of therapy. Five variables were significantly associated with adherence to treatment, four of them as predictor factors for good adherence: an active occupation inside prison, the absence of HIV-related symptoms, a good or average acceptance of treatment, and a higher academic background; previous injection drug use as a risk factor for HIV transmission was associated with non-adherence. A simple self-report questionnaire may be useful for assessing adherence in prison inmates. Recognizing variables associated with adherence is essential to identify prisoners at high risk of being non-adherents in order to develop strategies for improving compliance.

Aim of our report is to discuss some key adherence features in the real world, by reporting two exceptional patients, who deliberately took all antiretroviral medications at half-dosage compared with standard prescriptions, and maintained a fully stable and sustained virological and immunological response after 6-10 consecutive years. The potential causes and consequences of this apparent misconduct of our patients on drug tolerability, resistance development, compliance monitoring, direct drug delivery, and health care providers behavior, are discussed.

Prevalence and impact of occult HBV infection in HIV positive patients is controversial. The aims of this study were to determine the prevalence of occult HBV infection and its impact on histological and virological parameters. 52 HIV/HCV (but HBsAg-negative) co-infected patients, 29 HBsAg and anti-HCV negative chronic hepatitis, and 20 HBsAg positive chronic hepatitis controls were studied. DNA was extracted from frozen biopsies and amplified with primers for S, C and X regions, and for (ccc) HBV-DNA. Sera were tested for HBV-DNA with two quantitative assays (Cobas Amplicor HBV Monitor, and the real-time COBAS (r) Taqman HBV Test, Roche Diagnostics, UK). Occult HBV infection was detected in 7 (13.4%) liver biopsies of the study group, and in none case of the non viral chronic hepatitis group (p=0.04). All serum samples were HBV-DNA negative with Cobas Amplicor HBV monitor assay, while 3 cases were found positive with real time PCR. Statistical analysis didn't show any impact of occult HBV infection on liver histology, CD4+ cells count, HIV and HCV load, and ALT levels. Occult B infection is relatively frequent in HIV/HCV co-infected patients, and is underestimated by common HBV-DNA serological assays. However, it doesn't seem to exert a relevant impact.

This is with reference to the article entitled, “HIV-1 Integrase: From Biology to Chemotherapeutics”, by Eriketi Zeinalipour-Loizidou, Christos Nicolaou, Athanasios Nicolaidesand Leondios G. Kostrikis, published in Current HIV Research , July 2007, Vol. 5, No. 4, pp. 365-388. Due to an oversight Figure 1, Figure 2 and Figure 3 of this paper were printed in black in white on reproduction in the printing. Color figures 1, 2 and 3 are being presented below with their corresponding captions.