HLA-G 3' untranslated region polymorphisms influence the susceptibility for human papillomavirus infection

Analogies between HPV Behavior in Oral and Vaginal Cavity: Narrative Review on the Current Evidence in the Literature

Human genital papilloma virus infection is the most prevalent sexually transmitted infection in the world. It is estimated that more than 75% of sexually active women contract this infection in their lifetime. In 80% of young women, there is the clearance of the virus within 18-24 months. In developed countries, oral squamous cell carcinoma (OSCC) is now the most frequent human papilloma virus (HPV)-related cancer, having surpassed cervical cancer, and it is predicted that by 2030 most squamous cell carcinomas will be the HPV-related rather than non-HPV-related form. However, there are currently no screening programs for oral cavity infection. While the natural history of HPV infection in the cervix is well known, in the oropharynx, it is not entirely clear. Furthermore, the prevalence of HPV in the oropharynx is unknown. Published studies have found wide-ranging prevalence estimates of 2.6% to 50%. There are also conflicting results regarding the percentage of women presenting the same type of HPV at two mucosal sites, ranging from 0 to 60%. Additionally, the question arises as to whether oral infection can develop from genital HPV infection, through oral and genital contact or by self-inoculation, or whether it should be considered an independent event. However, there is still no consensus on these topics, nor on the relationship between genital and oral HPV infections. Therefore, this literature review aims to evaluate whether there is evidence of a connection between oral and cervical HPV, while also endorsing the usefulness of the screening of oral infection in patients with high-risk cervical HPV as a means of facilitating the diagnosis and early management of HPV-related oral lesions. Finally, this review emphasizes the recommendation for the use of the HPV vaccines in primary prevention in the male and female population as the most effective means of successfully counteracting the increasing incidence of OSCC to date.

Harnessing the potential of HLA-G in cancer therapy: advances, challenges, and prospects

Immune checkpoint blockades have been prized in circumventing and ablating the impediments posed by immunosuppressive receptors, reaching an exciting juncture to be an innovator in anticancer therapy beyond traditional therapeutics. Thus far, approved immune checkpoint blockades have principally targeted PD-1/PD-L1 and CTLA-4 with exciting success in a plethora of tumors and yet are still trapped in dilemmas of limited response rates and adverse effects. Hence, unveiling new immunotherapeutic targets has aroused immense scientific interest in the hope of expanding the clinical application of immune checkpoint blockades to scale new heights. Human leukocyte antigen-G (HLA-G), a non-classical major histocompatibility complex (MHC) class I molecule, is enriched on various malignant cells and is involved in the hindrance of immune effector cells and the facilitation of immunosuppressive cells. HLA-G stands out as a crucial next-generation immune checkpoint showing great promise for the benefit of cancer patients. Here, we provide an overview of the current understanding of the expression pattern and immunological functions of HLA-G, as well as its interaction with well-characterized immune checkpoints. Since HLA-G can be shed from the cell surface or released by various cells as free soluble HLA-G (sHLA-G) or as part of extracellular vesicles (EVs), namely HLA-G-bearing EVs (HLA-GEV), we discuss the potential of sHLA-G and HLA-GEV as predictive biomarkers. This review also addresses the advancement of HLA-G-based therapies in preclinical and clinical settings, with a focus on their clinical application in cancer.

HLA-G 3'UTR haplotype analyses in HCV infection and HCV-derived cirrhosis, hepatocellular carcinoma and fibrosis

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease. Chronic HCV infection is also an important cause of hepatic fibrosis, cirrhosis and hepatocellular carcinoma (HCC). HCV has the capacity to evade immune surveillance by altering the host immune response. Moreover, variations in immune-related genes can lead to differential susceptibility to HCV infection as well as interfere on the susceptibility to the development of hepatic fibrosis, cirrhosis and HCC. The human leucocyte antigen G (HLA-G) gene codes for an immunomodulatory protein known to be expressed in the maternal-foetal interface and in immune-privileged tissues. The HLA-G 3' untranslated region (3'UTR) is important for mRNA stability, and variants in this region are known to impact gene expression. Studies, mainly focusing in a 14 bp insertion/deletion polymorphism, have correlated HLA-G 3'UTR with susceptibility to viral infections, but other polymorphic variants in the HLA-G 3'UTR might also affect HCV infection as they are inherited as haplotypes. The present study evaluated HLA-G 3'UTR polymorphisms and performed linkage disequilibrium test and haplotype assembly in 286 HCV infected patients who have developed fibrosis, cirrhosis or HCC, as well as in 129 healthy control subjects. Haplotypes UTR-1, UTR-2 and UTR-3 were the most observed in HCV+ patients, in the frequencies of 0.276, 0.255 and 0.121, respectively. No statistically significant difference was observed between HCV+ and control subjects, even when patients were grouped according to outcome (HCC, cirrhosis or fibrosis). Despite that, some trends in the results were observed, and therefore, we cannot rule out the possibility that variants associated to high HLA-G expression can be involved in HCV infection susceptibility.

HLA-G 3'UTR polymorphism diplotypes and soluble HLA-G plasma levels impact cervical cancer susceptibility and prognosis

Background

Human leukocyte antigen G (HLA-G) is an immune checkpoint molecule with relevance in several cancers. The aim of this study was to evaluate the potential role of soluble HLA-G (sHLA-G), its genetic polymorphisms and its haplotype structure in the susceptibility and prognosis of primary cervical cancer in a Chinese Han population.

Methods

We investigated sHLA-G plasma levels and 3' untranslated region (3'UTR) polymorphisms through ELISA and direct DNA sequencing, respectively, in cervical cancer patients (120 cases) and healthy control women (96 cases). The data were analyzed for associations using PowerMarker, Haploview, and GraphPad Prism.

Results

In this study, 8 polymorphic sites, 16 haplotypes and 23 diplotypes in the HLA-G 3'UTR were identified in our study population. We observed that each pair of 8 polymorphic sites exhibited linkage disequilibrium. The heterozygote CT genotype at position +3422 (rs17875408) was more common in cervical cancer patients than in healthy women (OR=5.285, P<0.05). Haplotypes UTR-1, UTR-3, and UTR-7 accounted for more than 85% of both groups, but no significant difference was found. The frequency of the UTR-1/UTR-3 diplotype in patients was significantly higher than that in controls (P<0.05). In addition, we further observed that HLA-G 3'UTR polymorphisms may influence the sHLA-G plasma level in patients' peripheral blood, especially 14 bp Ins/Del (rs371194629) and +3142 C/G (rs1063320). A receiver operating characteristic (ROC) curve analysis showed that the sHLA-G level had good diagnostic performance in differentiating patients with cervical cancer from healthy women (AUC>0.7). Among patients, mean sHLA-G levels increased with increasing FIGO stages but were not related to the overall survival time.

Conclusions

The results of the present study enhance our understanding of how HLA-G 3'UTR polymorphisms can influence the peripheral sHLA-G plasma level and play a key role in cervical carcinogenesis. This study further confirmed that sHLA-G may represent a novel plasma biomarker for the prognosis and potential therapeutic target of cervical cancer.

Induction of pulmonary HLA-G expression by SARS-CoV-2 infection

The non-classical human leukocyte antigen (HLA)-G exerts immune-suppressive properties modulating both NK and T cell responses. While it is physiologically expressed at the maternal-fetal interface and in immune-privileged organs, HLA-G expression is found in tumors and in virus-infected cells. So far, there exists little information about the role of HLA-G and its interplay with immune cells in biopsies, surgical specimen or autopsy tissues of lung, kidney and/or heart muscle from SARS-CoV-2-infected patients compared to control tissues. Heterogeneous, but higher HLA-G protein expression levels were detected in lung alveolar epithelial cells of SARS-CoV-2-infected patients compared to lung epithelial cells from influenza-infected patients, but not in other organs or lung epithelia from non-viral-infected patients, which was not accompanied by high levels of SARS-CoV-2 nucleocapsid antigen and spike protein, but inversely correlated to the HLA-G-specific miRNA expression. High HLA-G expression levels not only in SARS-CoV-2-, but also in influenza-infected lung tissues were associated with a high frequency of tissue-infiltrating immune cells, but low numbers of CD8+ cells and an altered expression of hyperactivation and exhaustion markers in the lung epithelia combined with changes in the spatial distribution of macrophages and T cells. Thus, our data provide evidence for an involvement of HLA-G and HLA-G-specific miRNAs in immune escape and as suitable therapeutic targets for the treatment of SARS-CoV-2 infections.

Role of HLA-G in Viral Infections

The human leukocyte antigen (HLA)-G is a non-classical HLA class I molecule, which has distinct features to classical HLA-A, -B, -C antigens, such as a low polymorphism, different splice variants, highly restricted, tightly regulated expression and immune modulatory properties. HLA-G expression in tumor cells and virus-infected cells, as well as the release of soluble HLA-G leads to escape from host immune surveillance. Increased knowledge of the link between HLA-G expression, viral infection and disease progression is urgently required, which highlights the possible use of HLA-G as novel diagnostic and prognostic biomarker for viral infections, but also as therapeutic target. Therefore, this review aims to summarize the expression, regulation, function and impact of HLA-G in the context of different viral infections including virus-associated cancers. The characterization of HLA-G-driven immune escape mechanisms involved in the interactions between host cells and viruses might result in the design of novel immunotherapeutic strategies targeting HLA-G and/or its interaction with its receptors on immune effector cells.

Evaluating the HLA-G (rs1063320) genetic variant and risk of human papillomavirus infection: a meta-analysis of 953 cases and 877 controls

Human leukocyte antigen-G (HLA-G) has immune-modulatory functions. Although the role of genetic variant HLA-G (rs1063320) in susceptibility to human papillomavirus (HPV) infection has been widely considered, it is still a matter of discussion. In order to shed light on the issue, we, therefore, conducted a meta-analysis to evaluate the common impact of the HLA-G (rs1063320) variant on susceptibility to HPV infection. Subsequently, the distribution of genotypes, genotyping techniques and ethnicity groups was collected, and general analyses were performed. A total number of five studies with 953 cases and 877 controls were found to meet our criteria. The polymorphism of HLA-G (rs1063320) was evaluated. This is the first meta-analysis to explore the connection between the HLA-G 3' UTR + 3142C/G (rs1063320) genetic variant and the risk of HPV infection. Our results showed no association between the variant of HLA-G 3' UTR + 3142C/G (rs1063320) and susceptibility to HPV infection in studied target populations.Impact StatementWhat is already known on this subject? Human papillomavirus (HPV) is the most widespread sexually transmitted infection in both men and women all over the world. It is correlated with prominent load of diseases and malignancies, including anogenital warts and anogenital and oropharyngeal cancers. In recent years, several studies manifested that different SNPs located on special genes seems to influence HPV infection risk.What the results of this study add? Our findings disclosed no relation between the variant of HLA-G 3' UTR + 3142C/G (rs1063320) and vulnerability to HPV infection in the target individuals.What are the implications of these findings for clinical practice and/or further research? The findings in current survey may offer a basis for further study on HLA-G variant in future investigation.

The association of HLA-G polymorphism with oral and genital HPV infection in men

The host genetic factors that influence the natural history of human papillomavirus (HPV) infection in men are not well known. Our aim was to evaluate the role of human leukocyte antigen (HLA)-G polymorphism in oral and genital HPV infection in men. Altogether, 130 men from the Finnish Family HPV Study, with a 6-year follow-up, were included in the analyses. HLA-G alleles were tested by direct sequencing. Oral, urethral, and semen samples were collected and analyzed for 24 different HPV genotypes. Unconditional logistic regression was used to determine associations between HLA-G alleles and genotypes with HPV infection and its outcomes. Overall, eight different HLA-G alleles were identified with 15 different HLA-G genotype combinations. The most common HLA-G allele among the men was G*01:01:01 (86.2%, n = 112) followed by G*01:01:02 (36.2%, n = 47). Allele G*01:01:02 showed to be protective against any- and high-risk (HR) oral HPV (OR range of 0.20–0.24, 95% CI range of 0.06–0.85). Men having allele G*01:01:01 showed a reduced risk for incident (OR 0.30, 95% CI 0.11–0.84) and persistent (OR 0.24, 95% CI 0.08–0.69) oral infections. Allele G*01:01:03 was associated with increased risk for urethral HR-HPV infections (OR 4.94, 95% CI 1.34–18.27). Among self-reported demographic data, genotype G*01:01:01/01:01:03 was associated with an increased risk for oral warts (OR 8.00, 95% CI 1.23–51.89) and allele G*01:03:01 increased the risk of pollen and/or animal allergy (OR 13.59, 95% CI 1.57–117.25). To conclude, HLA-G polymorphism in men largely impacts the outcome of an oral HPV infection and seems to associate with self-reported allergies.

Non-classical human leukocyte antigen class I in Tunisian children with autism

Autism spectrum disorders (ASD) are one of the most common childhood morbidities characterized by deficits in communication and social skills. Increasing evidence has suggested associations between immune genes located in the human leukocyte antigen (HLA) complex and etiology of autism.

In this study, we investigated whether the non-classical class I HLA-G, -E, and -F polymorphisms are associated with genetic predisposition to autism in Tunisia. We aimed to find a correlation between HLA-G genotypes and soluble HLA-G (sHLA-G) levels. We have analyzed the HLA-G, -E, and -F genotypes of 15 autistic children and their parents. DNA typing of HLA class I genes was performed using PCR-SSP and PCR-RFLP methods. Also, we evaluated the serum levels of HLA-G (1 and 5) by a validated ELISA technique in autistic probands and their parents.

No association was found between any polymorphism and autism in the study subjects. Additionally, we found no correlation between sHLA-G1 and sHLA-G5 and autism. Also, no significant difference in sHLA-G testing in parents and offspring was found. However, parents carrying [GG] genotype presented a higher sHLA-G levels than those carrying ([CC]+[GC]) genotypes (p = 0.037).

From this preliminary study, we conclude that the investigated polymorphisms of HLA-G, -E, and -F genes did not lead to autism susceptibility in Tunisian children. However, the CGTIGA haplotype was found to be associated with the disease.

HLA-G: Function, polymorphisms and pathology

HLA-G immune modulatory genes and molecules are presently being studied by a widespread number of research groups. In the present study, we do not aim to be exhaustive since the number of manuscripts published every year is overwhelming. Instead, our aim is pointing out facts about HLA-G function, polymorphism and pathology that have been confirmed by several different researchers, together with exposing aspects that may have been overlooked or not sufficiently remarked in this productive field of study. On the other hand, we question whether performing mainly studies on HLA-G and disease associations is going to give a clear answer in the future, since 40 years of study of classical HLA molecules association with disease has still given no definite answer on this issue.

The Role of HLA-G in Human Papillomavirus Infections and Cervical Carcinogenesis

Human leukocyte antigen (HLA)-G, a non-classical HLA-class I molecule, has a low polymorphism frequency, restricted tissue distribution and immunoinhibitory property. HLA-G expression in tumor cells and cells chronically infected with virus may enable them to escape from host immune surveillance. It is well-known that the HLA-G molecule is a novel biomarker and potential therapeutic target that is relevant in various types of cancers, but its role in cervical cancer has not been fully explored. In this review, we aim to summarize and discuss the immunologic role of the HLA-G molecule in the context of HPV infections and the process of cervical cancer carcinogenesis. A better understanding of the potential impact of HLA-G on the clinical course of persistent HPV infections, cervical epithelial cell transformation, tumor growth, recurrence and metastasis is needed to identify a novel diagnostic/prognostic biomarker for cervical cancer, which is critical for cervical cancer risk screening. In addition, it is also necessary to identify HLA-G-driven immune mechanisms involved in the interactions between host and virus to explore novel immunotherapy strategies that target HLA-G/immunoglobulin-like transcript (ILT) immune checkpoints.

Association of HLA-G 3' UTR polymorphism and expression with the progression of cervical lesions in human papillomavirus 18 infections

Background

Human leukocyte antigen (HLA)-G is an immune checkpoint molecule, which expression in cervical cancer cells enables them to escape immunosurveillance. To date, limited information has been published on the association of HLA-G genetic background in malignant cells with levels of HLA-G expression and the clinical outcome of patients.

Methods

We investigated the influence of the HLA-G 14 bp In/Del (rs66554220) and + 3142C/G (rs1063320) polymorphisms in 130 cases of HPV16 infection, 130 cases of HPV18 infection and 185 age-matched, unrelated, HPV-negative, and cytologically normal Chinese Han women. Case-matched cervical biopsy tissues were evaluated by immunohistochemistry.

Results

Our findings show that the frequency of alleles, 14 bp In (38.5% vs 29.2%, OR = 1.52, P < 0.05) and + 3142G (72.7% vs 57.0%, OR = 2.01, P < 0.05), were significantly increased in the HPV18-infected group compared with the control group. The HLA-G polymorphisms (alleles 14 bp In and + 3142G) are also associated with the progression of HPV18-related cervical lesions. Moreover, HLA-G expression increased from CIN1 to CIN2/3 lesions and was highest in patients with adenocarcinoma; however, a significant association between these characteristics and the HLA-G polymorphisms was not observed.

Conclusion

Our results support that the HLA-G 14 bp In and + 3142G alleles are risk factors for HPV18 infections and influence the progression of HPV18-related cervical lesions. This suggests that HLA-G-driven immune mechanisms play an important role in cervical carcinogenesis.

Variation sites at the HLA-G 3' untranslated region confer differential susceptibility to HIV/HPV co-infection and aneuploidy in cervical cell

Post-transcriptional regulatory elements associated with transcript degradation or transcript instability have been described at the 3' untranslated region (3'UTR) of the HLA-G gene. Considering that HPV infection and aneuploidy, which causes gene instability, are associated with cervical cell malignancy, as well as the fact that HIV infection and HLA-G may modulate the immune response, the present study aimed to compare the frequencies of HLA-G 3'UTR polymorphic sites (14-base pair insertion/deletion, +3142C/G, and +3187A/G) between 226 HIV+ women co-infected (n = 82) or not with HPV (n = 144) and 138 healthy women. We also evaluated the relationship between those HLA-G 3'UTR variants and aneuploidy in cervical cells. HPV types and HLA-G polymorphisms were determined by PCR and sequencing of cervical samples DNA. Aneuploidy in cervical cell was measured by flow cytometry. The HLA-G 3'UTR 14-bp ins/del was not associated with either HIV nor HIV/HPV co-infection. The +3142G allele (p = 0.049) and +3142GG genotype (p = 0.047) were overrepresented in all HIV-infected women. On the other hand, the +3187G allele (p = 0.028) and the +3187GG genotype (p = 0.026) predominated among healthy women. The +3142G (p = 0.023) and +3187A (p = 0.003) alleles were associated with predisposition to HIV infection, irrespective of the presence or not of HIV/HPV co-infection. The diplotype formed by the combination of the +3142CX (CC or CG) and +3187AA genotype conferred the highest risk for aneuploidy in cervical cell induced by HPV. The HLA-G 3'UTR +3142 and +3187 variants conferred distinct susceptibility to HIV infection and aneuploidy.

Genetic association between HLA-G 14-bp polymorphism and diseases: A systematic review and meta-analysis

BACKGROUND

HLA-G is an immune checkpoint molecule. Since a differential molecule expression has been reported even for healthy individuals, many studies have focused on polymorphisms at HLA-G regulatory regions, particularly the 3' untranslated region (3'UTR). The presence/absence of a 14-bp sequence was the first polymorphism described and it is the most studied in association between HLA-G and disorders.

METHODS

In this study, we performed a systematic review and meta-analysis of all association studies published regarding the HLA-G 14-bp.

RESULTS

We verified association between 14-bp alleles and diseases in the following situations: (1) presence of 14-bp (insertion) conferred susceptibility to preeclampsia (child alleles evaluated) and systemic lupus erythematosus (OR = 1.42; 95%CI = 1.04-1.93; p = 0.026 and OR = 1.13; 95%CI = 1.01-1.27, p = 0.028); (2) 14-bp absence (deletion) was associated with increased risk to breast cancer (OR = 1.23; 95%CI = 1.06-1.43; p = 0.006) and human Cytomegalovirus infection (OR = 2.06; 95%CI = 1.60-2.64; p < 0.0001); and (3) a risk association was observed between the group of reproductive disorders and the 14-bp insertion (OR = 1.12; 95%CI = 1.01-1.24; p = 0.034).

CONCLUSIONS

Considering that others 14-bp associations were inconclusive and that other variation sites observed at HLA-G 3'UTR exhibit a proven role on post-transcriptional regulation of HLA-G expression, the complete 3'UTR segment should be analyzed in terms of disease susceptibility, instead of a single polymorphism.

Meta-analysis of correlationship between HLA-G 3'UTR 14-bp Ins/Del polymorphism and virus susceptibility

BACKGROUND

There is a considerable amount of literature on the potential relationship between human leukocyte antigen-G 14-bp Ins/Del polymorphism and virus infection; however, results from these studies were inconclusive.

OBJECTIVES

A meta-analysis was carried out to determine whether the 14-bp Ins/Del polymorphism is a susceptible factor for virus infection.

METHODS

Data were extracted from PubMed and Web of Science databases, and included 10 case-control studies (1835 patients and 2357 controls).

RESULTS

A total of 177 records from 10 studies were retrieved. Overall, no significant correlation was found between HLA-G 14-bp Ins/Del polymorphism and total viruses under all genetic models (dominant model: OR = 0.93, 95% CI = 0.68-1.29; recessive model: OR = 1.12, 95% CI = 0.84-1.48; deletion/deletion (DD) vs insertion/insertion (II): OR = 1.03, 95% CI = 0.71-1.49; deletion (D) vs insertion (I): OR = 1.01, 95% CI = 0.81-1.25). However, further subgroup analyses by virus type and ethnicity revealed that HLA-G 14-bp Ins/Del polymorphism was significantly associated with HTLV-1 infection in mixed population under the dominant model.

CONCLUSIONS

Our study demonstrated that HLA-G 14-bp Ins/Del polymorphism may not have any effect on susceptibility to viruses.

Human leukocyte antigen-G expression and polymorphisms promote cancer development and guide cancer diagnosis/treatment

Human leukocyte antigen-G (HLA-G) is a non-classical HLA molecule, predominantly expressed in cytotrophoblast cells to protect the fetus during pregnancy. Notably, a high frequency of HLA-G expression has been observed in a wide variety of cancer types in previous studies. Furthermore, HLA-G expression in cancer has been considered to be detrimental, since it can protect cancer cells from natural killer cell cytotoxic T lymphocyte-mediated destruction, promote tumor spreading and shorten the survival time of patients by facilitating tumor immune evasion. In addition, HLA-G polymorphisms have been investigated in numerous types of cancer and are considered as risk factors and predictive markers of cancer. This review focuses on HLA-G expression and its polymorphisms in cancer, analyzing the mechanisms of HLA-G in promoting cancer development, and evaluating the potential and value of its clinical application as a diagnostic and prognostic biomarker, or even as a prospective therapeutic target in certain types of tumors.

HLA-G 3'-untranslated region polymorphisms are associated with HTLV-1 infection, proviral load and HTLV-associated myelopathy/tropical spastic paraparesis development

Most human T-lymphotropic virus type 1 (HTLV-1)-infected patients remain asymptomatic throughout life. The factors associated with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) development have not been fully elucidated; immunological and genetic factors may be involved. The association of 14 bp INS/DEL HLA-G polymorphism with HTLV-1 infection susceptibility has been reported previously. Here, other polymorphic sites at the HLA-G 3'-UTR (14-bp D/I, +3003C/T, +3010C/G, +3027A/C, +3035C/T, +3142C/G, +3187A/G and +3196C/G) were evaluated in 37 HTLV-1-infected individuals exhibiting HAM/TSP, 45 HTLV-1 asymptomatic carriers (HAC) and 153 uninfected individuals, followed up at University Hospital of the Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil. It was observed that: (i) 14bpDI genotype is a risk factor for HTLV-1 infection, while the 14bpDD and +3142CC genotypes were associated with protection against infection; (ii) the +3142C allele and the +3003CT and +3142CC genotypes were associated with susceptibility, while 14bpII and +3003TT genotypes were associated with protection against HAM/TSP development; and (iii) the 14bpII, +3010CC, +3142GG and +3187AA genotypes were associated with lower HTLV-1 proviral load compared to respective counterpart genotypes. Findings that HLA-G has a well-recognized immunomodulatory role and that the genetic variability at HLA-G 3'-UTR may post-transcriptionally modify HLA-G production indicate a differential genetic susceptibility to: (i) the development of HTLV-1 infection, (ii) the magnitude of HTLV-1 proviral load and (iii) HAM/TSP development.

The effect of human leukocyte antigen G alleles on human papillomavirus infection and persistence in a cohort of HIV-positive pregnant women from Brazil

Patients with compromised immune systems have more severe intraepithelial lesions and more rapid disease progression, in addition to increased risk for cervical cancer. Persistent infection by the human papillomavirus (HPV) is a necessary step in that process. By inducing expression of inhibitory ligands of natural killer cells, like HLA-G, HPV avoids the elimination of infected cells. Recent studies have investigated polymorphisms in HLA-G that may be associated with susceptibility to HPV infection and persistence. One hundred-forty HIV(+) pregnant women from Brazil had a DNA fragment comprising HLA-G exons 2-4 PCR-amplified, cloned, sequenced and analyzed for allele determination. Altogether, 22 alleles comprising 52 different genotypes were found. Four novel HLA-G alleles were characterized. We have not observed association of specific HLA-G alleles with HPV infection, but found a protective effect of the G:01:01:02 allele against the occurrence of intraepithelial lesions. In addition to describing new HLA-G alleles and defining new reference sequences, our data provide a better understanding of the impact of HLA-G alleles on HPV-related disease.

HLA-G Molecules in Autoimmune Diseases and Infections

Human leukocyte antigen (HLA)-G molecule, a non-classical HLA-Ib molecule, is less polymorphic when compared to classical HLA class I molecules. Human leukocyte antigen-G (HLA-G) was first detected on cytotrophoblast cells at the feto-maternal interface but its expression is prevalent during viral infections and several autoimmune diseases. HLA-G gene is characterized by polymorphisms at the 3' un-translated region and 5' upstream regulatory region that regulate its expression and are associated with autoimmune diseases and viral infection susceptibility, creating an unbalanced and pathologic environment. This review focuses on the role of HLA-G genetic polymorphisms, mRNA, and protein expression in autoimmune conditions and viral infections.