Risk association of BST2 gene variants with disease progression in HIV-1 infected Indian cohort

Bone marrow stromal cell antigen 2 (BST2) is an interferon induced host restriction factor for HIV-1 that blocks the release of nascent virions from infected T cells. We aimed to characterize BST2 gene variants in HIV-1 positive individuals in Indian cohort and study the association of these variants with disease progression in long term non progressors (LTNPs) and progressors. Archived samples of 32 LTNPs, 17 progressors, and 78 controls were screened for BST2 gene polymorphisms using Sanger's sequencing method. Frequency distribution, survival analysis and bioinformatics tools were used to study the association of BST2 variants with disease progression. Eighteen variants of BST2 gene were observed in Indian cohort. Intronic SNP rs919267T/C (OR = 4.489 [0.8494-27.03], p = .04157) and exonic SNP rs13485C/G (OR = 3.887 [0.8262-25.56], p = .0488) were found to be significantly associated with disease progression. Also, rs13485C/C genotype in combination with rs919267C/T (OR = 9.406 [1.384-111], p = .0085) and rs145303329 Δ19bp (OR = 3.887 [0.826-25.5], p = .048) were found to be significantly associated with disease progression. 19 bp indel rs145303329 and its allele c.1-443_1-442insCGCCCCCAGAC[C/T]CAGGCCC from BST2 promoter also showed association with disease progression (OR = 12.97 [0.9731-850.5], p = .026). Docking of AP2 repressor with above allele showed the total binding energy of LTNPs and progressors to be -2581.42 kcal/mol and -3563.27/-3562.84 kcal/mol respectively. We have identified the novel association of three BST2 gene SNPs; rs919267, rs13485 and indel rs145303329 from Indian cohort to be associated with the risk of HIV-1 disease progression for the first time.

BST-2/tetherin is overexpressed in mammary gland and tumor tissues in MMTV-induced mammary cancer

BST-2 restricts MMTV replication, but once infection has established, MMTV modulates BST-2 levels. MMTV-directed BST-2 modulation is tissue-specific and dependent on infection and neoplastic transformation status of cells. In the lymphoid compartment of infected mice, BST-2 expression is first upregulated and then significantly downregulated regardless of absence or presence of mammary tumors. However, in mammary gland tissues, upregulation of BST-2 expression is dependent on the presence of mammary tumors and tumor tissues themselves have high BST-2 levels. Elevated BST-2 expression in these tissues is not attributable to IFN since levels of IFNα and IFNγ negatively correlate with BST-2. Importantly, soluble factors released by tumor cells suppress IFNα and IFNγ but induce BST-2. These data suggest that overexpression of BST-2 in carcinoma tissues could not be attributed to IFNs but to a yet to be determined factor that upregulates BST-2 once oncogenesis is initiated.