SEMA3G and HIV infectious disease: PAP85-120 is naturally found in human seminal fluid (Arnold et al., 2012), whereas SEM1(45-107) and SEM2(49-107) were initially suspected to be present in seminal fluid (Roan et al., 2011), but subsequent studies suggest that shorter peptides, e.g. SEM1(86-107), are naturally more abundant and also promote HIV infection (Roan et al., 2014).