Human Leukocyte Antigen-G 14 Base Pairs Polymorphism in the Human Immunodeficiency Virus -1 Perinatal Transmission

Research Article

Open Access

Roberta Seron Sanches¹, Juliana Doblas Massaro², Erick da Cruz Castelli³, Celso Teixeira Mendes-Junior⁴, Francielly Maiara da Penna Matos ¹, Juliana Martinez¹, Simone Kashima Haddad², Silvana Maria Quintana⁵, Maria Célia Cervi⁶, Luciana Castelar Tsuda¹, Eduardo Antônio Donadi² and Ana Paula Morais Fernandes^1*

¹Department of General and Specialized Nursing, Nursing School of RibeirãoPreto, University of São Paulo, 3900 Av Bandeirantes, CEP14 040 - 902, RibeirãoPreto, SP, Brazil

²Department of Medical Clinical, Faculty of Medicine of RibeirãoPreto, University of São Paulo, 3900 Av Bandeirantes, CEP14 049 - 900, RibeirãoPreto, SP, Brazil

³Department of Biology, Biological Sciences Institute, Federal University of Goias, Goiânia – GO, Brazil

⁴Department of Chemistry, Faculty of Philosophy, Sciences and Literature of RibeirãoPreto, University of São Paulo, 3900 Av Bandeirantes, CEP14 040 - 901, RibeirãoPreto, SP, Brazil

⁵Department of Gynecology, Faculty of Medicine of RibeirãoPreto, University of São Paulo, 3900 Av Bandeirantes, CEP14 049 - 900, RibeirãoPreto, SP, Brazil

⁶Department of Pediatric, Faculty of Medicine of RibeirãoPreto, University of São Paulo, 3900 Av Bandeirantes, CEP14 049 - 900, RibeirãoPreto, SP, Brazil

^*Corresponding author:

Ana Paula M Fernandes
Department of General and Specialized Nursing
School of Nursing of RibeirãoPreto
University of São Paulo, 3900 Av. Bandeirantes
Monte Alegre, 14 049-902, Ribeirão Preto, SP, Brazil
Tel: +55 16 3602 3414
Fax: +55 16 3633 3271
E-mail: anapaula@eerp.usp.br

Received March 02, 2013; Published March 27, 2013

Citation: Sanches RS, Massaro JD, da Cruz Castelli E , Mendes-Junior CT, da Penna Matos FM, et al. (2013) Human Leukocyte Antigen-G 14 Base Pairs Polymorphism in the Human Immunodeficiency Virus -1 Perinatal Transmission. 2:652 doi:10.4172/scientificreports.652

Copyright: © 2013 Sanches RS, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Abstract

Background: HLA-G is expressed at maternal-fetal interface and is strongly involved on maternal-fetal tolerance. The 3’ untranslated region of the HLA-G gene presents an insertion (INS) or deletion (DEL) of a 14-base pair (bp) fragment, which is associated with stability and expression levels of HLA-G mRNA. In this study we verified the influence of the 14-bp INS/DEL polymorphism on the HIV vertical transmission.

Methods: Blood samples were obtained from 49 mother-child pairs (26 pairs with and 23 without vertical transmission). All children were born from HIV-positive mothers who did not receive antiretroviral therapy during pregnancy. The 14-bp polymorphism was detected by PCR-amplified DNA using specific primers.

Results: The presence of the DEL/DEL genotype was more frequent among mothers with HIV-infected child (P=0.05). In addition, the INS/DEL genotype similarity among mother and child pairs was more frequent on vertical transmission (69%) than in the absence of vertical transmission.

Conclusion: The presence of the DEL/DEL genotype, associated with high production of HLA-G, and the INS/ DEL genotype similarities between mother and child may favor HIV mother to child transmission.

Keywords

HLA-G; HIV; Mother-to-child; Vertical; Transmission

Introduction

HLA-G is highly expressed in trophoblast and it is considered to be an important mediator of maternal–fetal tolerance due to its ability to inhibit maternal cytotoxic cells [1]. Genetic polymorphisms observed at the HLA-G 3′ untranslated region (UTR) have been associated with post-transcriptional control of HLA-G mRNA expression. One of these polymorphisms is the presence (insertion-INS) or absence (deletion- DEL) of a 14-bp fragment (5′-ATTTGTTCATGCCT-3′, in which the DEL/DEL genotype has been associated with high expression of HLA-G mRNA [2-5].

Some viruses have developed the ability to increase HLA-G expression to evade host immune response [6], and an altered HLA-G expression induced by viruses may influence mother’s immune response and, theoretically, the vertical virus transmission. Studies associating polymorphic sites at coding and 3’UTRHLA-G regions in vertical transmission [7-9] or only in children presenting or not vertical HIV transmission have been reported (10,11).

Considering that the 14-bp INS/DEL polymorphism has a wellrecognized role on the HLA-G mRNA expression, we evaluated the frequency of the 14-bp INS/DEL polymorphism and the INS/DEL genotype similarity in Southeastern Brazilian mother-child pairs perinatally exposed to HIV-1 infection.

The study was conducted on 49 mother-child pairs, stratified into two groups: i) 26 HIV-1-positive mother/HIV-1-positive child pairs and 23 HIV-1-positive mother/HIV-1-negative child pairs. All mother-child pairs were not treated with antiretroviral drugs and did not receive breastfeed. Patients were selected from the Acquired Immunodeficiency Outpatient Clinic at the University Hospital of the Faculty of Medicine of RibeirãoPreto, University of São Paulo, Brazil. HIV-1-positive mother/HIV-1-positive child pair samples were obtained from 1993 – 1996, when antiretroviral therapy was not freely dispensed by the Brazilian Ministry of Health. The local Ethics Committee of the University Hospital of Faculty of Medicine of RibeirãoPreto approved the study protocol, and informed consent was obtained from all individuals (HCFMRP-USP # 9060/2006).

Genomic DNA was obtained from peripheral blood mononuclear cells using a salting out procedure. The HLA-G 14-bp INS/DEL polymorphism was evaluated as previously described [12]. Allelic and genotypic frequencies were computed by the direct counting method. The frequency of each allele or genotype was compared between patients and controls by the two-sided Fisher exact test, with the aid of the GraphPadInStat3.06 software, which was also used to estimate the odds ratio (OR) and its 95% confidence interval (95%CI). GENEPOP 3.4 software was used to observe the adherences of genotypic proportions to expectations under Hardy-Weinberg equilibrium (HWE) by the complete enumeration method [13].

The 14-bp INS/DEL allele and genotype frequencies were compared between the two groups, i.e., HIV-1 positive transmission and HIV-1 negative transmission, and only an increased frequency of the DEL/DEL genotype among mothers with HIV-infected child (P=0.05) (Table 1) was detected. In addition, the 14-bpgenotype similarity among mother and child pairs was more frequent on vertical transmission (69%) than in the absence of vertical transmission (P=0.09).

Table 1: Allelic and genotypic frequencies of the 14-bp INS/DEL polymorphisms in HIV-positive mothers and in their children. Samples were distributed in two groups, according to perinatal HIV transmission. Mother/child pairs were also organized according to genotype similarity.

The role of the HLA-G polymorphisms in HIV-1 infection has not been elucidated. Considering the HIV horizontal transmission, the HLA-G*01:05N allele, which codes truncated non-functional HLA-G molecules, was associated with protection against the HIV-1 infection, while the HLA-G*01:01:08 allele, which codes functional soluble and membrane-bound molecules, was associated with an increased risk of HIV-1 infection in Zimbabwean women [4,5]. Since HLA-G inhibits NK cell-mediated lysis [14-16], the absence or reduced expression of HLA-G molecules may allow NK cells to destroy HIV-infected cells, protecting against HIV infection.

Regarding the role of HLA-G gene on HIV vertical transmission, contradictory results have been reported. The first published paper on this issue reported that mother-child pair discordance at HLA-G codon 57 was associated with reduced risk of HIV-1 transmission in North-American Caucasians [7], a finding that was not confirmed in the Zimbabwean population [9]. Since the polymorphism at codon 57 does not change the HLA-G amino acid composition and presumably HLA-G function, it is difficult to understand how this silent mutation could have a direct influence on HIV transmission. Such finding could reflect the effect of other polymorphic sites at the HLA-G gene in linkage disequilibrium with the codon 57 polymorphism. Then, other gene regions have been studied, and a likely candidate region is HLA-G3’ UTR, which has several post-transcriptional control elements, and the most widely studied is the 14 bp INS/DEL polymorphism.

Two independent studies reported an association between HLA-G nucleotide sequences located at 3′UTR, including the C variant at position +3777C/G (also designated as +3010C/G) and 14-bp DEL polymorphism, with decreased risk of HIV-1 vertical transmission [8,10]. Moreover, two other independent studies have shown that the HLA-G+3777 and 14-bp polymorphisms are in linkage disequilibrium, especially the association between the 14-bp DEL and the +3777C allele [ 11,17]. The HLA-G +3777C variant alone has no effect on vertical transmission of HIV-1 but, when linked with the 14-bp DEL allele, it exerts a protective role [11]. In two studies performed in Brazilian children from Recife (North East Brazil), evaluating the transmission of HLA-G 3’ UTR alleles only in children infected or not with HIV and born from HIV-infected mothers, reported that the DEL/INS and +3777G > C polymorphisms were in linkage disequilibrium and the presence of the DEL-C/DEL-C combined genotype conferred protection against HIV mother-to-child transmission [10,11,18].

We analyzed Brazilian mother-child pairs from São Paulo (South East Brazil) and observed an increased frequency of the DEL/DEL homozygote genotype was observed among mothers with HIVinfected child, and the 14-bp INS/DEL genotype similarities were more frequent on vertical transmission than on its absence. Aikhionbare et al. [8] showed similarities at the HLA-G 3’ UTR polymorphic sites (+3742, +3743 and +3777) in mother-child HIV-infected pairs. Since the +3742 and +3743 polymorphic sites are associated with 14-bpDEL and are in linkage disequilibrium with +3777, our results are similar to the mentioned study. Considering that the population backgrounds of both studies are different, concordant associations reinforces the power of such finding.

HLA-G alleles presenting the 14-bp DEL have been associated with increased production of HLA-G, but with lower stability of mRNA. Considering that HLA-G is highly expressed in trophoblast at the maternal-fetal interface, exhibiting an important role on fetal immunological tolerance [19,20], the role of HLA-G in the HIV-1 mother-to-child transmission shall be important. To corroborate this idea, a recent study reported high expression placental HLA-G1 expression among HIV-1-infected mothers with infected babies when compared to uninfected babies [21].

Taken together, the expression of HLA-G is a complex process modulated by many factors, such as HLA-G polymorphisms, which may contribute to an immunological environment affecting the outcome of HIV-1 mother-to-child transmission. In conclusion, the presence of the DEL/DEL genotype in mothers, associated with high production of HLA-G, and 14-bp genotype similarities between mother and child may favor HIV mother to child transmission.

Acknowledgements

This work received financial support from FAPESP (Fernandes APM #2011/08177-1) and CNPq.

References