CCR5, RANTES and SDF-1 polymorphisms and mother-to-child HIV-1 transmission

IMPLICATION OF FIVE AIDS RELATED GENES IN MOTHER-TO-CHILD TRANSMISSION AND ACQUISITION OF HUMAN IMMUNODEFICIENCY VIRUS 1 IN CAMEROON

BACKGROUND

Genetic variants in the mother and/or infant have been described with evidence to be associated with mother-to-child transmission of HIV, but somehow with contradictory results depending on ethnic or geographic populations. We aimed at looking at the association between the allelic frequency of some genes with vertical transmission or acquisition of HIV in Cameroon.

METHODOLOGY

A total of 262 mothers (212 HIV-infected and 50 HIV non-infected) with their babies (270 in total, 42 HIV exposed-infected, 178 HIV exposed non-infected and 50 HIV non-exposed) were recruited in Yaounde-Cameroon. Their genotypes for CCR5-Delta32, CCR5 promoter59029A/G, CCR2-64I, SDF1-3'A and TRIM5α-136Q were analyzed using polymerase chain reaction and restriction fragment length polymorphisms.

RESULTS

Allelic frequencies were 14.7%, 41.9%, 9.5% and 14.7% for CCR2-64I, CCR5-59029-A/G, TRIM5α-136Q, SDF1-3'A respectively in the mothers and 18.8%, 35.9%, 11.3% and 20.5% in the babies. No delta 32 mutation in the CCR5 gene was found. The mutant genotype was most significantly frequent in the non-transmitter than in the transmitter (p= 0.005) for the SDF-1 3'A. SDF1-3'A [Odd ratio = 1.69; 95% confidence interval: 0.1158 to 0.7277); was associated to MTCT, P = 0.008.The homozygote mutants for the CCR5-59029-G were significantly higher in the infected than in the exposed uninfected babies (p=0.04). The mutations in the other genes were neither implicated in the acquisition nor in the transmission.

CONCLUSION

SDF1-3'A was associated to the reduction of MTCT. The CCR5-59029-A/G favored acquisition of HIV by babies. Our study showed that polymorphisms in chemokine ligand may be involved in MTCT.

Host Molecular Factors and Viral Genotypes in the Mother-to-Child HIV-1 Transmission in Sub-Saharan Africa

Maternal viral load and immune status, timing and route of delivery, viral subtype, and host genetics are known to influence the transmission, acquisition and disease progression of human immunodeficiency virus-1 (HIV-1) infection. This review summarizes the findings from published works on host molecular factors and virus genotypes affecting mother to child transmission (MTCT) in Africa and identifies the gaps that need to be addressed in future research. Articles in PubMed, Google and AIDSearch and relevant conference abstracts publications were searched. Accessible articles on host factors and viral genetics impacting the MTCT of HIV, done on African populations till 2015 were downloaded. Forty-six articles were found and accessed; 70% described host genes impacting the transmission. The most studied gene was the CCR5 promoter, followed by the CCR2-64I found to reduce MTCT; then SDF1-3’A shown to have no effect on MTCT and others like the DC-SIGNR, CD4, CCL3 and IP-10. The HLA class I was most studied and was generally linked to the protective effect on MTCT. Breast milk constituents were associated to protection against MTCT. However, existing studies in Sub Saharan Africa were done just in few countries and some done without control groups. Contradictory results obtained may be due to different genetic background, type of controls, different socio-cultural and economic environment and population size. More studies are thus needed to better understand the mechanism of transmission or prevention.

RANTES Gene Polymorphisms Associated with HIV-1 Infections in Kenyan Population

Previous studies have reported that two single nucleotide polymorphisms (SNPs) in the RANTES gene promoter region, -403G/A and -28C/G, are associated with a slower rate of decline in CD4+ T cell count. In addition, as a ligand of the major HIV coreceptor CCR5, it is known to block HIV-CCR5 interactions in the course of the HIV infection cycle. This study was carried out with the aim of determining the occurrence of single nucleotide polymorphisms (SNPs) -403G > A and -28C > G in the promoter region of RANTES, in a subset of the Kenyan population. Genomic DNA was extracted from peripheral blood monocular cells and used to amplify the RANTES gene region. Restriction fragment length polymorphism was used to determine the genotypes of the RANTES gene. Out of 100 HIV infected individuals, 19% had G1 genotypes (403G/G, 28C/G), 30% (403A/A, 28C/C), and 50% (403G/A, 28C/C), while in healthy blood donors 13% had G4 (403G/A, 28C/C) genotypes, 22% (403A/A, 28C/C), and 54% (403G/A, 28C/C). HIV negative blood donors (54%) had higher risk of alteration to risk of HIV transmission compared to those who were HIV infected (50%). However, the risk to transmission and distribution differences was not significant (P = 0.092). The study showed that RANTES polymorphisms -403 and -28 alleles do exist in the Kenyan population.

The role of genetic variants of Stromal cell-Derived Factor 1 in pediatric HIV-1 infection and disease progression

Stromal cell-Derived Factor 1 (SDF1) is the natural ligand of CXCR4, the coreceptor of HIV-1 X4 viruses. This study investigated the role of the single nucleotide polymorphism (SNP) rs1801157 (NM_000609.5:c.*519G>A) of the SDF1 gene in the natural history of mother-to-child transmission of HIV-1 and disease progression of HIV-1-infected children. The study was conducted in 428 children born to HIV-1-seropositive mothers, who had not undergone antiretroviral therapy (ART) during pregnancy, and in 120 HIV-1-infected children for whom the end-point was the onset of AIDS or the initiation of ART; 16 children developed early AIDS (<24 months of life), 13 from 24 to 84 months of age, and 14 had late AIDS (>84 months). The rs1801157 SNP was not associated with risk of perinatal infection in any genetic models tested. By contrast, this SNP influenced disease progression in a time-dependent manner. rs1801157 GA heterozygous children had a higher risk of late AIDS (HR = 6.3, 95%CI 1.9–20.7, p = 0.002) than children with the rs1801157 GG genotype. Children were studied for viral coreceptor usage at birth, after 84 months of age and/or at AIDS onset. While R5 viruses using CCR5 coreceptor were predominant at birth (94%) and at early AIDS (85%), viruses using CXCR4 coreceptor emerged during the course of infection and were detected in 49% of children older than 84 months and in 62% of late AIDS. The rs1801157 SNP did not influence the emergence of R5X4 viruses, but children with the rs1801157 GA genotype and R5X4 viruses were at significantly higher risk of late AIDS than children with rs1801157 GG genotype (OR = 8.0, 95% CI 1.2–52.2, p = 0.029). Our results indicate that the rs1801157 SNP does not influence perinatal infection, but impacts disease progression. This effect is time-dependent and linked to the coreceptor-usage of viral variants that undergo evolution during the course of HIV-1 infection.

Host factors that influence mother-to-child transmission of HIV-1: genetics, coinfections, behavior and nutrition

Mother-to-child transmission (MTCT) is the most important mode of HIV-1 acquisition among infants and children and it can occur in utero, intrapartum and postnatally through breastfeeding. Great progress has been made in preventing MTCT through use of antiretroviral regimens during gestation, labor/delivery and breastfeeding. The mechanisms of MTCT, however, are multifactorial and remain incompletely understood. This review focuses on select host factors affecting MTCT, in particular genetic factors, coexisting infections, behavioral factors and nutrition. Whereas much emphasis has been placed on decreasing maternal HIV-1 viral load, an important determinant of MTCT, through use of antiretroviral agents, complementary focus on overall maternal health is often neglected. By addressing coinfections in mothers and infants, improving the mother's nutritional status and modifying risky behaviors and practices, not only is maternal and child health improved, but a direct benefit in reducing MTCT can be derived. The study of genetic variations in susceptibility to HIV-1 infection is rapidly evolving, and the future is likely to bring revolutionary changes in HIV-1 prevention by enhancing natural resistance to infection and by individually tailoring pharmacologic regimens.