Current HIV Research - Volume 5, Issue 2, 2007

Approximately 700,000 children become newly infected with HIV annually, mainly through mother-to-child transmission (MTCT), making paediatric HIV a leading cause of morbidity and mortality worldwide. The substantial interest in preventing MTCT (PMTCT) has generated information on rates of transmission and associated factors, but there is a lack of information on disease progression and mortality in vertically-infected children, especially from resource-poor settings. Peer-review journals with titles or abstracts containing reference to the review's themes were selected using widely available search engines. We review relevant literature on mortality in children born to HIV infected mothers; morbidity and mortality associated with paediatric HIV infections; eligibility to and efficacy of antiretroviral therapy (ART). Child mortality is independently associated with maternal HIV status and maternal death, with paediatric infection resulting in ∼4 fold increase in mortality by age 2 years. Morbidities seen in infected children were similar to those seen in uninfected children, although the rates and recurrences of illness were greater. There is some evidence that progression to AIDS may be more rapid in resource poor settings, although data on this are very limited. PMTCT and paediatric ART have been shown to be highly successful in resource-limited settings, but are not universally applied. Further efforts to increase coverage of both PMTCT and paediatric ART could substantially reduce the numbers of children becoming infected and improve survival of those infected. Additionally, improvements in health infrastructures could improve care provision, not only through improved detection and monitoring but also through treatment of co-morbidities and nutritional support

Background: No more than 8% of HIV positive children needing treatment in low- and middle-income countries have access to antiretroviral drugs (ARVs). Children presently account for about 4% of all treated patients, while for equitable access they should make up at least 13%. Aims: This study explores key issues, implications and interaction dynamics to boost production of easy-to-use and affordable fixed-dose combination (FDC) ARVs for children in the developing world. Potentials for equitable solutions are examined including priority steps and actions, appropriate treatment options and reliable forecasting methods for paediatric ARVs, as well as combination incentives to generic companies against market unattractiveness and enforced intellectual property (IP) rights. Moreover, implementation strategies to enhance the development and production of affordable ARV paediatric formulations and appropriate supply systems to ensure availability are investigated. Results: The current market for FDC paediatric ARVs is already substantial and will only grow with improved and scaled up diagnosis and monitoring of children. This provides an argument for immediate increase of production and development of FDC ARVs for children. These formulations must be low cost and included in the list of Essential Medicines to avoid children continuing to lag behind in access to treatment. Access-oriented, long-term drug policy strategies with the ability to pass muster of governments, the UN system, as well as generic and research-based enterprises are needed to let children gain expanded and sustained access to FDC ARVs. Under the requirements listed above, IP-bound Voluntary License (VL) flexibilities do appear, if coupled with substantial combination incentives to generic firms, as a fitting tool into the needs. Policies must consider enhancing human resource capacity in the area of caregivers and social and health workers aiming to spread correct information and awareness on effectiveness and rationale of FDC ARVs for children. Policies should urge that paediatric ARV treatment programmes entwine with extant interventions on prevention of mother-to-child transmission, as well as with HIV treatment initiatives focused on mothers and household members. Policies, again, should consider centralising functions and pooling resources to help overcome drug supply barriers. WHO's brokering role in VL-based agreements between wealthy and developing country industries, as well as its technical guidance in setting international standards should not be waived while looking for sustained access to optimised ARV treatments for children. Strategies discussed in this paper, while taking unavoidability of marketing and profit rules into account, look closely into the trade and drug policy directions of China and India according to frontier crossing implications of their IP management trends as well as their multi-faceted penetration strategies of both the wealthy and under-served markets the world over.

Previous studies of HIV-1 variants transmitted from mother-to-infant have focused primarily on computational analyses of partial envelope gene sequences, rather than analyses of functional envelope variants. There are very few examples of well-characterized functional envelope clones from mother-infant pairs, especially from envelope variants representing the most prevalent subtypes worldwide. To address this, we amplified the envelope variants present in 4 motherinfant transmission pairs, all of whom were infected with subtype A and three of whom presumably transmitted HIV-1 during the breastfeeding period. Functional envelope clones were constructed, either encoding full-length envelope sequences from the mother and baby or by making chimeric envelope clones in a common backbone sequence. The infant envelope sequences were genetically homogeneous compared to the maternal viruses, and pseudoviruses bearing these envelopes all used CCR5 as a coreceptor. The infant viruses were generally resistant to neutralization by maternal antibodies present near the time of transmission. There were no notable differences in sensitivity of the mother and infant envelope variants to neutralization by heterologous plasma or monoclonal antibodies 2G12 and b12, or to inhibition by sCD4, PSC-RANTES or TAK779. This collection of viral envelopes, which can be used for making pseudotyped viruses, may be useful for examining the efficacy of interventions to block mother-infant transmission, including sera from vaccine candidates, purified antibodies under consideration for passive immunization and viral entry inhibitors.

Immunization with more than one immunogen (co-immunization) is an efficient regimen to induce immunity to multiple antigens. However, immune interference has been reported using multi-plasmid DNA immunizations. HIV-1 envelope (Env) and Gag gene products are the predominant immunogens used in current AIDS vaccines, although, few studies have evaluated possible immune interference when these two antigens are co-administered. Therefore, in this study, immune interference during co-inoculation was examined using DNA vaccines expressing lentiviral Envs and Gag from gene sequences optimized for efficient expression in mammalian cells (codon-optimized). BALB/c mice vaccinated in separate hind legs with each plasmid individually elicited high titer immune responses, however, when HIV-1 Envgp120 and HIV-1 Gagp55 DNA plasmids were co-inoculated, there was a reduction in the immune responses elicited to HIV-1 Gagp55. To determine if the anti-HIV-1 Gagp55 immune interference was specific to HIV-1 Envgp120, mice were coimmunized with plasmids expressing the surface envelope protein from two additional lentiviruses, Envgp130-SIV or Envgp90-EIAV, or a soluble form of hemagglutinin (sHA) from influenza virus and HIV-1 Gagp55- or SIV Gagp55-DNA. Interestingly, there was no reduction in anti-HIV-1 Gagp55 immune responses using other lentiviral envelopes or the influenza sHA. Also, none of the lentiviral envelopes reduced anti-SIV Gagp55 immune responses during co-immunization. Therefore, anti-HIV-1 Gag immune interference appears specific to co-immunizations with HIV-1 Envgp120 and may involve a yet undefined immunological mechanism(s).

Dual infections with HIV-1 and Hepatitis C virus (HCV) may proceed in concert to cause severe disease. HIV positive individuals that become infected with HCV advance more rapidly to AIDS than those that are infected with HIV- 1 alone. In this study, HLA-A2.1 mice were immunized with a combination vaccine including HIV and HCV immunogens (polycistronic DNA + proteins) or vaccine containing either HIV or HCV immunogens. Mice immunized with the combined HIV/HCV regimen had similar antibody titers as the group receiving either the HIV-1 or HCV only regimen. Proliferative immune responses showed that mice receiving the combined HIV/HCV vaccine exhibited a three fold higher stimulation index (SI) to gp120 than mice immunized with the vaccine containing HIV alone. To determine whether our vaccine strategy induced Th1 or Th2 immune responses, IFN-γ and IL-4/IL-5 were measured. The combined HIV/HCV vaccine induced a higher level of Th1 responses to HIV-1 gag protein compared with the other groups, as measured by IFN-γ production. Interestingly, detection of IFN-γ by ELISPOT assay demonstrated that the combined HIV/HCV vaccine group had increased numbers of spot forming cells (SFC) to HIV-gp120 peptides when compared to that of the HIV-1 only vaccine group. The combined HIV/HCV vaccine group also showed an increase in SFC to HCV-core peptides in comparison with the group receiving the HCV only vaccine. Intracellular IFN-γ staining confirmed the ELISPOT results and demonstrated that the combined HIV/HCV group had significantly higher percentages of HIV and HCV-specific CD8+T cells in comparison to the groups receiving the HIV or HCV vaccines. These results suggest a new approach to maximize vaccine efficacy against HIV and HCV.

Background: Very little is known about the influence of Highly Active Antiretroviral Therapy (HAART) on the surface expression of CCR5 and CXCR4 with respect to receptor tropism and replication kinetics of autologous HIV strains, during continuous therapy and structured treatment interruption (STI) regimens. Objectives: The main objectives of this study were to assess whether continuous therapy and STI regimens had any modulatory effects on expression of CCR5 and CXCR4 on T lymphocytes. Study Design: We studied 6 patients on continuous HAART, 4 patients on STI and 1 treatment-naïve patient. Sequential peripheral blood mononuclear cells (PBMC) samples were analyzed to determine viral replication kinetics, the genotype influencing tropism of the autologous strain, in vitro co-receptor usage patterns in relation to the surface expression of each co-receptor. Results: Our data suggest that predominant CCR5 expression and tropism, during therapy, but significant downmodulation of CXCR4 expression. During the off-therapy phases of STI, CXCR4 expression increased, which correlated with increased CXCR4 tropism of isolates from these time points. In-vitro tropism during therapy was consistent with the HIV-1 V3 genotype, which was characteristic of CCR5 using strains. Conclusions: These results suggest that certain HAART regimens influence the surface expression of CXCR4, which may have profound implications for antiretroviral treatment.

Background: Highly active antiretroviral therapy (HAART) can successfully reduce plasma and tissue levels of HIV-1 RNA and results in reductions in HIV-related morbidity and mortality, but the slow viral evolution during therapy in cellular reservoirs is a continuing problem. In addition, little remains known how viral evolutionary process may differ between cell-free and cell-associated compartments, over time, in vivo in patients receiving HAART or STI. Objectives: The main objectives of this study were to assess viral replication kinetics, drug resistance and viral evolution during HAART and STI. Study design: We have conducted a longitudinal study of virus culture kinetics in vitro, molecular analysis of uncultured HIV-1 variants from plasma and PBMC of 6 patients on HAART, 4 patients on STI, and 6 from treatment-naïve patients. Results: Our data suggest that drug resistance mutations remained compartmentalized between plasma and PBMC. The divergent distribution of resistance mutations between plasma and PBMC coincided with divergent env gene evolution in these compartments. In contrast, the HIV strains from therapy-naive patients showed tight genetic and phylogenetic concordance between plasma and PBMC. Both STI and non-STI groups showed the presence of resistance mutations to both RT and protease inhibitors, which correlated with inadequate suppression of viremia and partially with the virus culture isolation in vitro. Conclusions: Overall, STI for HIV patients has no added advantage over regular HAART at the virologic level and in the diminution of resistance mutations that result in therapy failure. Under both forms of anti-retroviral therapies, virus could be isolated in vitro from the PBMC showing continuing low-level viral replication under suppressive therapy. Overall, these data may be useful in predicting the late emergence of drug resistance mutations via the latent integrated provirus.

To determine the degree of HIV-1-specific cytotoxic-T-lymphocyte (CTL) cross-responses to the clade B and C consensus sequences at the single peptide level. We assessed CTL responses in 46 HIV-1 clade B chronically infected individuals using an interferon-γ Elispot assay with a total of 826 overlapping peptides spanning HIV-1clade B and C consensus sequences. In general, 583 peptides were recognized by HIV-1-specific T cells in the study subjects (292 clade B, 291 clade C respectively), of which 204 peptides in both clades were recognized simultaneously. The HIV-1-specific CTL responses to both clade peptides contributed 54.23% (954/1759) to the total responses. No significant difference was observed between the overall magnitude or frequency of CTL responses to clade B proteins and those to clade C proteins. According to the profiles of CTL magnitude and CTL frequency, the top 44 and 35 synthetic peptides were identified as immunodominant regions in the clade B and C consensus sequences respectively and 27 corresponding peptides in two immunodominant regions were cross-reactive. These peptides with cross-reactivity had a significantly higher ability to elicit CTL responses (P< 0.01) and preferentially had a trend of lower entropy and higher inter-clade homology. A wide degree of cross-clade reactivity of HIV-1-specific T cells exist in clade B and clade C variants. Most of immunodominant peptides with cross-reactivity are vigorous to elicit CTL responses and preferentially be conservative. This result may make future HIV-1 vaccines including multiple copies of CTL epitopes in these immunodominant peptides effective for this population.

Immunoglobulins (Ig) of pooled healthy human sera were purified by affinity chromatography based on their reactivity with human IgG. This Ig fraction represent connected, natural antibodies (NAbs) and here are denoted as anti- IgG antibodies. The data revealed that IgG, IgA and IgM isotypes are constituents of anti-IgG fraction. The ability of anti- IgG antibodies to prevent infection of PBMC by HIV-1 was demonstrated. They exhibited different neutralizing activity depending on the phenotype of the tested virus. The efficacy of neutralization was comparable to monoclonal antibodies (MAbs) IgG1b12 at least for the HIV-1 92HT593B strain. These studies suggest that connected antibodies thus, constituents of immune network, could prevent infection by HIV-1. NAbs as essential components of therapeutic molecules of intravenous Ig (IVIg) have a beneficial effect on variety of immunological disorders by affecting the structure, function and dynamics of the immune network. Since, hallmark of HIV-1 infection are immunological disorders we hypothesizes that they might be corrected to some extend by anti-IgG antibodies.

In this paper we report the study of tryptophan metabolism via serotonin in ventricular CSF in HIV-1 infection in order to investigate the origin of tryptophan metabolites in the human brain. The patients (n=4) were affected with noncommunicating hydrocephalus. One of these also was suffering from HIV-1 infection. The CSF was withdrawn from different sites of the cerebral cavity with a neuroendoscopic procedure which allows an accurate exploration of all the cerebral ventricles. The measurement of tryptophan, 5-hydroxytryptophan, serotonin, 5-hydroxyindoleacetic acid, and melatonin was carried out by HPLC with fluorometric detection. In HIV-1 infection the highest concentration of tryptophan is present in the CSF of the choroid plexus; however, the levels are markedly lower than those in hydrocephalic individuals (control group). 5-Hydroxytryptophan CSF content is higher in HIV-1 infection than in hydrocephalic controls in all districts examined. Regarding serotonin, a great difference appears in the choroid plexus and in the pituitary recess between the HIV-1 infected patient and the control group. The values of 5-hydroxyindoleacetic acid are much lower in the CSF of the HIV-1 infected patient than in hydrocephalic controls. Melatonin levels appear to fluctuate largely but, in the HIV-1 infection, a great variability is present among the sites of CSF withdrawal. The third ventricle contains the highest concentration of melatonin and the choroid plexus and the pituitary recess the lowest. All the melatonin concentrations in HIV-1 infection are largely different than in hydrocephalic controls. This is the first report on the measurement of tryptophan metabolites via serotonin in ventricular CSF in HIV-1 infection.

Toxoplasmosis is a well recognized manifestation of AIDS, but the disseminated disease is a rare condition and it has not been associated to HIV seroconversion to our knowledge. We describe a fatal episode of disseminated T. gondii acute infection with massive organ involvement during primary HIV infection. The serological data demonstrate primary T. gondii infection. The avidity index for HIV antibodies supports recent HIV-1 infection.

Background: High cardiovascular risk and accelerated atherosclerosis are associated with human immunodeficiency virus (HIV). Recently, the use of highly active antiretroviral therapy (HAART) for the treatment of HIV infection is correlated with the development of HAART-associated metabolic syndrome and lipodystrophy (LDS). Detection of epicardial fat thickness, new index of visceral adiposity in non HIV-infected patients, might be important as diagnostic tool in HIV-infected patients on HAART. Objective: Primary objective of this study was to evaluate whether echocardiographic epicardial adipose tissue is related to visceral adipose tissue (VAT) and Carotid Intima-Media Thickness (IMT), index of atherosclerosis in HIV-infected patients on HAART with LDS Design: We studied 60 consecutive HIV-infected HIV-infected subjects on HAART without LDS. Main Outcomes Measures: Epicardial fat thickness and IMT were measured by ultrasonography in both study and control groups. Magnetic resonance imaging (MRI) was used to calculate VAT in HIV-infected subjects on HAART with LDS. Results: Epicardial adipose tissue thickness showed an excellent correlation with MRI-VAT (r=0.85; P<0.001) and IMT (r=0.78;P<0.001) in HIV-infected patients on HAART-with LDS. Multiple regression analysis showed that epicardial fat thickness was best predicted by MRI-VAT and IMT (R2=0.57, p<0.001 and p<0.01, respectively). HIV-infected patients with HAART-associated metabolic syndrome and LDS showed higher epicardial fat thickness and IMT (8 vs 6.5 mm; 0.71 vs 0.66 mm, respectively, p<0.01 for both) than HIV-infected subjects on HAART without LDS. Conclusion: Echocardiographic assessment of epicardial fat may have the potential to be a simple and reliable marker of visceral adiposity and increased cardiovascular risk in HIV-infected patients with HAART-associated metabolic syndrome and LDS.