HIV-1 co-receptor usage: influence on mother-to-child transmission and pediatric infection

The Interplay of HIV and Autophagy in Early Infection

HIV/AIDS is still a global threat despite the notable efforts made by the scientific and health communities to understand viral infection, to design new drugs or to improve existing ones, as well as to develop advanced therapies and vaccine designs for functional cure and viral eradication. The identification and analysis of HIV-1 positive individuals that naturally control viral replication in the absence of antiretroviral treatment has provided clues about cellular processes that could interact with viral proteins and RNA and define subsequent viral replication and clinical progression. This is the case of autophagy, a degradative process that not only maintains cell homeostasis by recycling misfolded/old cellular elements to obtain nutrients, but is also relevant in the innate and adaptive immunity against viruses, such as HIV-1. Several studies suggest that early steps of HIV-1 infection, such as virus binding to CD4 or membrane fusion, allow the virus to modulate autophagy pathways preparing cells to be permissive for viral infection. Confirming this interplay, strategies based on autophagy modulation are able to inhibit early steps of HIV-1 infection. Moreover, autophagy dysregulation in late steps of the HIV-1 replication cycle may promote autophagic cell-death of CD4⁺ T cells or control of HIV-1 latency, likely contributing to disease progression and HIV persistence in infected individuals. In this scenario, understanding the molecular mechanisms underlying HIV/autophagy interplay may contribute to the development of new strategies to control HIV-1 replication. Therefore, the aim of this review is to summarize the knowledge of the interplay between autophagy and the early events of HIV-1 infection, and how autophagy modulation could impair or benefit HIV-1 infection and persistence, impacting viral pathogenesis, immune control of viral replication, and clinical progression of HIV-1 infected patients.

CCR2 Genetic Polymorphism And Its Potential Effect On HIV Acquisition In A Population Of Children Living In The Northern Region Of Cameroon

Background and objectives

The association of chemokine receptor-2 (CCR2) polymorphism with HIV transmission or disease progression remains highly controversial. The role of CCR2-64I allele in HIV infection may differ from one population to another because of their genetic background. The objectives of this study were to characterize the CCR2 genetic polymorphism and to determine its potential effect in HIV acquisition in children living in the Northern Region of Cameroon.

Materials and methods

A cross-sectional study was carried out in five health facilities in the Northern region of Cameroon. DNA was extracted from the Buffy coat of each participant using the QIAamp^®DNA mini kit. The DNA extract was then subjected to polymorphic analyses. CCR2 genotypes were analyzed by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). The Chi-Squared test was used for the assessment of the Hardy-Weinberg equilibrium.

Results

A total of 134 children under 15 years comprised of 38 HIV-exposed infected (28.36%) and 96 HIV-exposed un-infected (71.64%) participants were recruited. Prevalences of 44.78% wild type homozygous, 48.52% heterozygous and 6.7% mutant homozygous alleles were found in the overall population. An allelic frequency of 29.69% for the mutant allele CCR2-64I was found in HIV-exposed un-infected individuals as compared to 34.21% in HIV-infected children (p=0.47).

Conclusion

The CCR2-64I allele is relatively common in the Northern Region of Cameroon, with a similar distribution among HIV-exposed un-infected and infected children. As this allele alone does not seem to confer protection against HIV-1 infection, further studies using genotype-combination of CCR2 polymorphism and other single nucleotide polymorphisms would be of great relevance in both HIV prevention and novel therapeutic strategies.

The evolution of HIV-1 interactions with coreceptors and mannose C-type lectin receptors

The phenotype of human immunodeficiency virus type 1 (HIV-1) commonly evolves between and within infected individuals, at virus transmission, and during disease progression. This evolution includes altered interactions between the virus and its coreceptors, i.e., chemokine receptors, as well as mannose C-type lectin receptors (CLRs). Transmitted/founder viruses are predominantly restricted to CCR5, whereas the subsequent intrapatient evolution of HIV-1 coreceptor use during progressive disease can be subdivided into two distinct pathways. Accordingly, the CCR5-restricted virus population is either gradually replaced by virus variants able to use CXCR4 or evolves toward an altered, more flexible use of CCR5. Despite a strong dependency on these coreceptors for host cell entry, HIV-1 also interacts with other cell surface molecules during target cell attachment, including the CLRs. The virus interaction with the CLRs may result either in the efficient transfer of virus to CD4(+) T cells or in the degradation of the virus in endosomal compartments. The determinants of the diverse outcomes depend on which CLR is engaged and also on the glycan makeup of the envelope glycoproteins, which may evolve with the strength of the immune pressure during the disease course. With the current clinical introduction of CCR5 antagonists and the development of additional entry inhibitors, knowledge on the evolution and baseline characteristics of HIV-1 interactions with coreceptor and CLR interactions may play important roles for individualized and optimized treatment strategies. This review summarizes our current understanding of the evolution of HIV-1 interactions with these receptors.

Evolution of HIV-1 coreceptor usage and coreceptor switching during pregnancy

Coreceptor switch from CCR5 to CXCR4 is associated with HIV disease progression. To document the evolution of coreceptor tropism during pregnancy, a longitudinal study of envelope gene sequences was performed in a group of pregnant women infected with HIV-1 of clade B (n=10) or non-B (n=9). Polymerase chain reaction (PCR) amplification of the V1-V3 region was performed on plasma viral RNA, followed by cloning and sequencing. Using geno2pheno and PSSMX4R5, the presence of X4 variants was predicted in nine of 19 subjects (X4 subjects) independent of HIV-1 clade. Six of nine X4 subjects exhibited CD4(+) T cell counts <200 cells/mm(3), and the presence of X4-capable virus was confirmed using a recombinant phenotypic assay in four of seven cases where testing was successful. In five of nine X4 subjects, a statistically significant decline in the geno2pheno false-positive rate was observed during the course of pregnancy, invariably accompanied by progressive increases in the PSSMX4R5 score, the net charge of V3, and the relative representation of X4 sequences. Evolution toward X4 tropism was also echoed in the primary structure of V2, as an accumulation of substitutions associated with CXCR4 tropism was seen in X4 subjects. Results from these experiments provide the first evidence of the ongoing evolution of coreceptor utilization from CCR5 to CXCR4 during pregnancy in a significant fraction of HIV-infected women. These results inform changes in host-pathogen interactions that lead to a directional shaping of viral populations and viral tropism during pregnancy, and provide insights into the biology of HIV transmission from mother to child.

HIV-1 Nef breaches placental barrier in rat model

The vertical transmission of HIV-1 from the mother to fetus is known, but the molecular mechanism regulating this transmission is not fully characterized. The fetus is highly protected by the placenta, which does not permit microbial pathogens to cross the placental barrier. In the present study, a rat model was established to observe the effect of HIV-1 protein Nef on placental barrier. Evans blue dye was used to assay permeability of placental barrier and fourteen day pregnant Sprague Dawley rats were injected intravenously with 2% Evans blue dye along with various concentrations of recombinant Nef. After an hour, animals were sacrificed and dye migration was observed through the assimilation of peripheral blood into fetus. Interestingly, traces of recombinant Nef protein were detected in the embryo as well as amniotic fluid and amniotic membrane along with placenta and uterus. Our study indicates that recombinant HIV-1-Nef protein breaches the placental barrier and allows the migration of Evans blue dye to the growing fetus. Further the concentration of Nef protein in blood is directly proportional to the intensity of dye migration and to the amount of Nef protein detected in uterus, placenta, amniotic membrane, amniotic fluid and embryo. Based on this study, it can be concluded that the HIV-1 Nef protein has a direct effect on breaching of the placental barrier in the model we have established in this study. Our observations will be helpful to understand the molecular mechanisms related to this breach of placental barrier by Nef in humans and may be helpful to identify specific Nef inhibitors.

Human immunodeficiency virus type 1 mother-to-child transmission and prevention: successes and controversies

The World Health Organization (WHO) and United Nations Programme on HIV/AIDS (UNAIDS) estimated that an additional 370 000 new human immunodeficiency virus type 1 (HIV-1) infections occurred in children in 2009, mainly through mother-to-child transmission (MTCT). Intrapartum transmission contributes to approximately 20-25% of infections, in utero transmission to 5-10% and postnatal transmission to an additional 10-15% of cases. MTCT accounts for only a few hundred infected newborns in those countries in which services are established for voluntary counselling and testing of pregnant women, and a supply of antiretroviral drugs is available throughout pregnancy with recommendations for elective Caesarean section and avoidance of breastfeeding. The single-dose nevirapine regimen has provided the momentum to initiate MTCT programmes in many resource-limited countries; however, regimens using a combination of antiretroviral drugs are needed also to effectively reduce transmission via breastfeeding.