A Genetic Polymorphism of FREM1 Is Associated with Resistance against HIV Infection in the Pumwani Sex Worker Cohort

Abstract

A subgroup of women enrolled in the Pumwani sex worker cohort remain seronegative and PCR negative for human immunodeficiency virus type 1 despite repeated exposure through high-risk sex work. Studies have shown that polymorphisms of genes involved in antigen presentation and viral restriction factors are associated with resistance to HIV infection. To discover other possible genetic factors underlying this HIV-resistant phenotype, we conducted an exploratory nonbiased, low-resolution, genome-wide single-nucleotide polymorphism (SNP) analysis comparing 60 HIV-resistant women to 48 HIV-infected controls. The SNP minor allele rs1552896, in an intron of FREM1, was significantly associated with the resistant phenotype (P ‫؍‬ 1.68 ؋ 10 ؊5 ; adjusted P ‫؍‬ 2.37 ؋ 10 ؊4 ; odds ratio [OR], 9.51; 95% confidence interval [CI], 2.82 to 32.05). We expanded the sample size by genotyping rs1552896 in the Pumwani cohort and comparing 114 HIV-resistant women to 609 HIV-infected controls and confirmed the association (P ‫؍‬ 1.7 ؋ 10 ؊4 ; OR, 2.67; 95% CI, 1.47 to 4.84). To validate the association in a second cohort, we genotyped 783 women enrolled in a mother-child health study and observed the minor allele of rs1552896 enriched in HIV-uninfected women (n ‫؍‬ 488) compared to HIV-infected enrollees (n ‫؍‬ 295) (P ‫؍‬ 0.036; OR, 1.69; 95% CI, 0.98 to 2.93). Quantitative reverse transcription-PCR showed that FREM1 mRNA was highly expressed in tissues relevant for HIV-1 infection, and immunohistochemical analysis revealed that FREM1 protein is expressed in the ectocervical mucosa of HIV-resistant women. The significant association of rs1552896 with an HIV-resistant phenotype, together with the expression profile of FREM1 in tissues relevant to HIV infection, suggests that FREM1 is a potentially novel candidate gene for resistance to HIV infection.

Development of Monoclonal Antibodies to Interrogate Functional Domains and Isoforms of FREM1 Protein

“…(9) We have used a FREM1 monoclonal antibody (developed in our laboratory with a synthetic peptide) to study FREM1 expression in female cervical tissue by immunohistochemistry. (11) This panel of MAbs with defined epitopes will be very useful for detecting FREM1 expression in different cell lines and PBMCs by immunohistochemistry and flow cytometry and potentially be used to differentiate expression of different splice variants and epitopes. We hope investigators will find utility of this monoclonal antibody panel as molecular tools to design interesting experiments that will elucidate the function and role of this protein and its alternative splicing variants in susceptibility to HIV-1 infection and other diseases.…”

“…(11) Since FREM1 was first identified by the Health Mammalian Gene Collection program in 2002, (21) much has been discovered about the diverse function of this apparent ''moonlighting'' protein. Studies have shown that FREM1 mutations cause congenital diseases such as MOTA (7) and BNAR.…”

“…(9,10) Recently, we have identified the minor allele of a SNP (rs1552896) within the FREM1 gene that is associated with natural resistance to HIV-1 infection in the Pumwani sex worker cohort. (11) To further study the role of FREM1 in differential susceptibility to HIV-1 infection, we have developed a panel of monoclonal antibodies. This study describes the epitope characterization of these FREM1-specific monoclonal antibodies and the utility of using these antibodies in immunohistochemistry and Western blot and FACS analyses.…”

Immunogenetics of Small Ruminant Lentiviral Infections

“…As observed in HIV-1 studies, resistance or slower disease progression is a polygenic trait, involving a complex interaction between a variety of different innate and acquired immune genes [130,131]. It may, however, be possible to breed for resistance using phenotypic rather than genotypic selection.…”

Association Study of Common Genetic Variants and HIV-1 Acquisition in 6,300 Infected Cases and 7,200 Controls

“…A smaller number of GWAS have also investigated host genetic influences on HIV-1 acquisition using samples of individuals with known or presumed exposure to an HIV-1 infected source [12], [13], [14], [15], [16]. With the exception of CCR5Δ32 homozygosity (known to explain a proportion of HIV-1 resistance in Europeans [17]), no reproducible associations with increased or reduced HIV-1 acquisition have been observed.…”