Genetic factor common to schizophrenia and HIV infection is associated with risky sexual behavior: antagonistic vs. synergistic pleiotropic SNPs enriched for distinctly different biological functions.

Schizophrenia (SZ) and HIV infection are serious disorders with a complex phenotypic relationship. Observational studies have described their comorbidity; their genetic correlation is not well studied. We performed extensive analysis in search of common genetic factors for SZ and HIV, and their relationship with risky sexual behavior (RSB). Summary statistics from genome-wide association studies of HIV infection and schizophrenia were obtained and 2379 European Americans were genotyped and assessed for RSB score. Genetic relationships between traits were analyzed in three ways: linkage disequilibrium (LD) score regression to estimate genetic correlation; GPA (Genetic analysis incorporating Pleiotropy and Annotation) to test pleiotropy and identify pleiotropic loci; polygenic risk scores (PRS) of SZ and HIV to predict RSB using linear regression. We found significant pleiotropy (p = 5.31E - 28) and a positive genetic correlation (cor = 0.17, p = 0.002) for SZ and HIV infection. Pleiotropic SNPs with opposite effect directions (antagonistic) and SNPs with the same effect direction (synergistic) were enriched for distinctly different biological functions. SZ PRS computed with antagonistically pleiotropic SNPs consistently predicted RSB score with nominal significance, but SZ PRS based on either synergistically pleiotropic SNPs or all SNPs did not predict RSB. The epidemiologic correlation between schizophrenia and HIV can partly be explained by overlapping genetic risk factors, which are related to risky sexual behavior.