CCR5 promoter polymorphisms and HIV-1 perinatal transmission in Brazilian children

CCR5Δ32 in Brazil: Impacts of a European Genetic Variant on a Highly Admixed Population

The genetic background of Brazilians encompasses Amerindian, African, and European components as a result of the colonization of an already Amerindian inhabited region by Europeans, associated to a massive influx of Africans. Other migratory flows introduced into the Brazilian population genetic components from Asia and the Middle East. Currently, Brazil has a highly admixed population and, therefore, the study of genetic factors in the context of health or disease in Brazil is a challenging and remarkably interesting subject. This phenomenon is exemplified by the genetic variant CCR5Δ32, a 32 base-pair deletion in the CCR5 gene. CCR5Δ32 originated in Europe, but the time of origin as well as the selective pressures that allowed the maintenance of this variant and the establishment of its current frequencies in the different human populations is still a field of debates. Due to its origin, the CCR5Δ32 allele frequency is high in European-derived populations (~10%) and low in Asian and African native human populations. In Brazil, the CCR5Δ32 allele frequency is intermediate (4-6%) and varies on the Brazilian States, depending on the migratory history of each region. CCR5 is a protein that regulates the activity of several immune cells, also acting as the main HIV-1 co-receptor. The CCR5 expression is influenced by CCR5Δ32 genotypes. No CCR5 expression is observed in CCR5Δ32 homozygous individuals. Thus, the CCR5Δ32 has particular effects on different diseases. At the population level, the effect that CCR5Δ32 has on European populations may be different than that observed in highly admixed populations. Besides less evident due to its low frequency in admixed groups, the effect of the CCR5Δ32 variant may be affected by other genetic traits. Understanding the effects of CCR5Δ32 on Brazilians is essential to predict the potential use of pharmacological CCR5 modulators in Brazil. Therefore, this study reviews the impacts of the CCR5Δ32 on the Brazilian population, considering infectious diseases, inflammatory conditions, and cancer. Finally, this article provides a general discussion concerning the impacts of a European-derived variant, the CCR5Δ32, on a highly admixed population.

Frequency of the CCR5-delta32 allele in Brazilian populations: A systematic literature review and meta-analysis

The CCR5 is a chemokine receptor widely expressed by several immune cells that are engaged in inflammatory responses. Some populations have individuals exhibiting a 32bp deletion in the CCR5 gene (CCR5-delta32) that produces a truncated non-functional protein not expressed on the cell surface. This polymorphism, known to be associated with susceptibility to infectious and inflammatory diseases, such as osteomyelitis, pre-eclampsia, systemic lupus erythematous, juvenile idiopathic arthritis, rheumatoid arthritis and HIV/AIDS, is more commonly found in European populations with average frequency of 10%. However, it is also possible to observe a significant frequency in other world populations, such as the Brazilian one. We performed a systematic review and meta-analysis of CCR5-delta32 genetic association studies in Brazilian populations throughout the country to estimate the frequency of this polymorphism. We also compared CCR5-delta32 frequencies across Brazilian regions. The systematic literature reviewed studies involving delta32 allele in Brazilian populations published from 1995 to 2015. Among the reviewed literature, 25 studies including 30 Brazilian populations distributed between the North, Northeast, South and Southeast regions were included in our meta-analysis. We observed an overall allelic frequency of 4% (95%-CI, 0.03-0.05), that was considered moderate and, notably, higher than some European populations, such as Cyprus (2.8%), Italy (3%) and Greece (2.4%). Regarding the regional frequency comparisons between North-Northeast (N-NE) and South-Southeast (S-SE) regions, we observed an allelic frequency of 3% (95%-CI, 0.02-0.04) and 4% (95%-CI, 0.03-0.05), respectively. The populations from S-SE regions had a slightly higher CCR5-delta32 frequency than N-NE regions (OR=1.41, p=0.002). Although there are several studies about the CCR5-delta32 polymorphism and its effect on the immune response of some infectious diseases, this report is the first meta-analysis study that provides a descriptive study of the distribution of CCR5-delta32 allele in Brazilian population.

C-C chemokine receptor type five (CCR5): An emerging target for the control of HIV infection

When HIV was initially discovered as the causative agent of AIDS, many expected to find a vaccine within a few years. This has however proven to be elusive; it has been approximately 30 years since HIV was first discovered, and a suitable vaccine is still not in effect. In 2009, a paper published by Hutter et al. reported on a bone marrow transplant performed on an HIV positive individual using stem cells that were derived from a donor who was homozygous for a mutation in the CCR5 gene known as CCR5 delta-32 (Δ32) (Hütter et al., 2009). The HIV positive individual became HIV negative and remained free of viral detection after transplantation despite having halted anti-retroviral (ARV) treatment. This review will focus on CCR5 as a key component in HIV immunity and will discuss the role of CCR5 in the control of HIV infection.

HIV mother-to-child transmission: a complex genetic puzzle tackled by Brazil and Argentina research teams

Human immunodeficiency virus (HIV) mother-to-child transmission is a complex event, depending upon environmental factors and is affected by host genetic factors from mother and child, as well as viral genetic elements. The integration of multiple parameters (CD4 cell count, virus load, HIV subtype, and host genetic markers) could account for the susceptibility to HIV infection, a multifactorial trait. The goal of this manuscript is to analyze the immunogenetic factors associated to HIV mother-to-child transmission, trying to unravel the genetic puzzle of HIV mother-to-child transmission and considering the experience in this topic of two research groups from Brazil and Argentina.

Distribution of CCR-5Δ32, CCR2-64I, and SDF-1-3'A alleles among Jordanians

Entry of HIV virus into cells is mediated by chemokine receptors. Genetic variations in chemokine receptors have been shown to modulate susceptibility to HIV infection and disease course. In this study, the frequencies of CCR5 (CCR5-Δ32), CCR2 (CCR2-64I), and SDF-1 (SDF-1-3') gene polymorphisms were determined in a Jordanian population. A total of 540 subjects were randomly selected from different regions of Jordan (South, Middle, and North). Six individuals were found to carry the CCR5-Δ32 allele (0.6%) and only in the heterozygous genotype. The frequencies of CCR2-64I and SDF1-3'A were 17.5% and 34.2%, respectively. In addition, no significant difference in the distribution of the examined polymorphisms among different regions of Jordan was detected. In conclusion, the CCR5-Δ32 allele is rare, whereas the CCR2-64I and SDF1-3'A alleles are common among Jordanians.

The genetic associations and epistatic effects of the CCR5 promoter and CCR2-V64I polymorphisms on susceptibility to HIV-1 infection in a Northern Han Chinese population

The outcome of human immunodeficiency virus (HIV)-1 infection and course to AIDS are variable among individuals. Both chemokine receptor 5 (CCR5) and CCR2 gene polymorphisms play essential roles in the susceptibility of HIV-1 infection. To investigate the main and epistatic effects of the CCR5 promoter and CCR2-V64I polymorphisms on HIV-1 infection in the Northern Han Chinese, subjects of 91 HIV-1-infected patients and 91 health controls were recruited. Single-nucleotide polymorphisms (SNPs) in the CCR5 promoter region and CCR2-V64I variants were genotyped. In the single-locus analysis, CCR5 58755-G and CCR5 59653-T alleles were significantly associated with HIV-1 infection (odds ratio [OR]=0.529, 95% confidence interval [CI]: 0.295-0.948; OR=1.710, 95% CI: 1.039-2.814). After adjustment with age and gender, subjects with the CCR5 59653-CT genotype showed the increased risk of HIV-1 infection compared with those with the wild-type CC genotype (adjusted OR=2.502; 95% CI: 1.332-4.698). No positive association was observed in other SNPs. Haplotype-based association analysis revealed that the haplotype TATGC was associated with the susceptibility to HIV-1 infection (p=0.003). Besides, we found the significant epistatic effects between the CCR5 58755-A/G and CCR5 59029-A/G polymorphisms associated with the lower risk of HIV-1 infection. In addition, we also identified the best three-factor interaction model, including the CCR5 58755-A/G, 59029-A/G, and CCR2-V64I polymorphisms, indicating that there were also strong gene-gene interactions between the CCR5 promoter and CCR2 polymorphisms on the susceptibility of HIV-1 infection. These findings contribute to understanding the genetic mechanism for the susceptibility of HIV-1 infection in Northern Han Chinese.

HIV-1 control in battlegrounds: important host genetic variations for HIV-1 mother-to-child transmission and progression to clinical pediatric AIDS

HIV-1 mother-to-child transmission (MTCT) is the passing of maternal HIV-1 to the offspring during pregnancy, labor and delivery, and/or breastfeeding. HIV-1 MTCT and the evolution to pediatric AIDS are multifactorial, dynamic and variable phenotypic conditions. Both genetic and nongenetic variables can influence susceptibility to HIV-1 MTCT or the rate of progression to clinical pediatric AIDS. In this review, we summarize the current state of knowledge about the roles of genetic variations seen in host immune response genes, and those that have been independently associated, mostly through population genetics of candidate genes, with interindividual susceptibility to HIV-1 MTCT, and progression to pediatric AIDS. We examine common and rare host genetic variations at coding and noncoding polymorphisms, whether functional or not, in agonists and antagonists of the immune response, which have been implicated in HIV-1 control in battlegrounds of cell entry, replication and evolution to AIDS. Further, we point to over 380 single-nucleotide polymorphisms, mostly within the HLA super region, recently identified in unbiased genome-wide association studies of HIV replication and evolution in adults, still unexplored in the context of HIV-1 MTCT, and which are likely to also influence susceptibility to pediatric HIV-1/AIDS.

A haplotype in the CCR5 gene promoter was associated with the susceptibility to HIV-1 infection in a northern Chinese population

It has been reported that single nucleotide polymorphisms (SNPs) in the promoter of the CCR5 gene are associated with the risk for HIV-1 infection and AIDS progression. Using resequencing, we performed a systematic survey of 78 HIV-1 seropositive individuals and 70 population-matched healthy control individuals from northern China to investigate SNPs of the CCR5 gene promoter and evaluated their effects on HIV-1 infection and the progression of AIDS. Linkage disequilibrium (LD) plots and haplotypes were generated using Haploview software. The association analyses were statistically compared using the Chi-square test with SPSS13.0 software for Windows. Seven SNPs (58755A>G, 58791C>T, 58934G>T, 59029A>G, 59353C>T, 59402A>G and 59653C>T) in the region of the CCR5 gene promoter were evaluated in this study. Among the seven SNPs, the minor allele frequencies of 58755G and 58791T were less than 2%. The differences in frequencies of the other five SNPs were not significant between case and control cohorts (P>0.05). In the case cohort, the association between these SNPs and clinical features (CD4+ T-lymphocyte counts and clinical categories) was not significant (P>0.05); however, there was a significant association between the haplotype GGTAC and susceptibility to HIV-1 infection (P<0.05), which is not consistent with other reports studied in different populations. The results suggest that the haplotype GGTAC may have a role in the process of HIV-1 infection in the northern Chinese population.

Analysis of the CCR5 gene coding region diversity in five South American populations reveals two new non-synonymous alleles in Amerindians and high CCR5*D32 frequency in Euro-Brazilians

The CC chemokine receptor 5 (CCR5) molecule is an important co-receptor for HIV. The effect of the CCR5*D32 allele in susceptibility to HIV infection and AIDS disease is well known. Other alleles than CCR5*D32 have not been analysed before, neither in Amerindians nor in the majority of the populations all over the world. We investigated the distribution of the CCR5 coding region alleles in South Brazil and noticed a high CCR5*D32 frequency in the Euro-Brazilian population of the Paraná State (9.3%), which is the highest thus far reported for Latin America. The D32 frequency is even higher among the Euro-Brazilian Mennonites (14.2%). This allele is uncommon in Afro-Brazilians (2.0%), rare in the Guarani Amerindians (0.4%) and absent in the Kaingang Amerindians and the Oriental-Brazilians. R223Q is common in the Oriental-Brazilians (7.7%) and R60S in the Afro-Brazilians (5.0%). A29S and L55Q present an impaired response to β-chemokines and occurred in Afro- and Euro-Brazilians with cumulative frequencies of 4.4% and 2.7%, respectively. Two new non-synonymous alleles were found in Amerindians: C323F (g.3729G > T) in Guarani (1.4%) and Y68C (g.2964A > G) in Kaingang (10.3%). The functional characteristics of these alleles should be defined and considered in epidemiological investigations about HIV-1 infection and AIDS incidence in Amerindian populations.

CCR5 expression and duration of high risk sexual activity among HIV-seronegative men who have sex with men

OBJECTIVES

To test the hypothesis that in comparison with those with shorter risk duration, individuals with longer HIV risk duration would have reduced susceptibility to HIV-1 infection as measured by CCR5 expression, and to evaluate whether variation in CCR5 expression could be explained by known genetic polymorphisms.

DESIGN AND METHODS

A cross-sectional study of HIV-1 exposed but uninfected men who have sex with men. The risk duration was estimated from self-reported years since first receptive anal intercourse. CCR5 expression on peripheral blood CD4+ monocytes and T cells was determined by flow cytometry. The CCR5-Delta32 mutation and polymorphisms in the CCR5 promoter and CCR2 as well as the copy number of CCL3L1 were analyzed by polymerase chain reaction. Plasma levels of MIP-1alpha (CCL3), MIP-1beta (CCL4) and RANTES (CCL5) were also measured. As risk duration varied with age, analyses were restricted to 67 individuals aged 30-49 years.

RESULTS

Multiple linear regression analyses, adjusted for age and race, showed a significant negative association between HIV risk duration and CCR5 expression on monocytes (P = 0.01), and in a separate model, a similar negative association with CCR5 expression on T cells (P = 0.03). Low CCR5 expression was attributable mainly to CCR5-Delta32 heterozygosity and the CCR5-59029G allele.

CONCLUSIONS

We confirmed a role for reduced CCR5 expression in HIV-1 resistance. CCR5-Delta32 heterozygosity and the CCR5-59029G allele were significant predictors of low CCR5 expression. Individuals with high CCR5 expression who resisted infection despite long HIV risk duration form an interesting group within which to search for additional mechanisms of resistance to HIV infection.

[Brazilian psychosocial and operational research vis-à-vis the UNGASS targets]

Items from the UNGASS Draft Declaration of Commitment on HIV/AIDS (2001) are analyzed. The Brazilian experience of new methods for testing and counseling among vulnerable populations, preventive methods controlled by women, prevention, psychosocial support for people living with HIV/AIDS, and mother-child transmission, is discussed. These items were put into operation in the form of keywords, in systematic searches within the standard biomedicine databases, also including the subdivisions of the Web of Science relating to natural and social sciences. The Brazilian experience relating to testing and counseling strategies has been consolidated through the utilization of algorithms aimed at estimating incidence rates and identifying recently infected individuals, testing and counseling for pregnant women, and application of quick tests. The introduction of alternative methods and new technologies for collecting data from vulnerable populations has been allowing speedy monitoring of the epidemic. Psychosocial support assessments for people living with HIV/AIDS have gained impetus in Brazil, probably as a result of increased survival and quality of life among these individuals. Substantial advances in controlling mother-child transmission have been observed. This is one of the most important victories within the field of HIV/AIDS in Brazil, but deficiencies in prenatal care still constitute a challenge. With regard to prevention methods for women, Brazil has only shown a halting response. Widespread implementation of new technologies for data gathering and management depends on investments in infrastructure and professional skills acquisition.