Polyomavirus microRNA in saliva reveals persistent infectious status in the oral cavity

Current evidence suggests that Polyomavirus (PyV) microRNAs (miRNAs) circulating in biological fluids may be relevant to understanding viral persistence. Here, the expression of polyomavirus BKPyV, JCPyV, MCPyV and SV40 miRNAs in saliva was investigated to evaluate PyV prevalence/persistence in the oral cavity. PyV-DNA status and PyV-miRNA expression was examined in paired saliva and plasma samples of 100 HIV-infected patients and of 50 healthy subjects using digital droplet PCR and PyV-miRNA-5p stem-loop RT-PCR. Overall, the PyV-miRNA in saliva samples showed higher positivity (65%) than PyV-DNA (24%). In particular, the PyV-miRNA prevalence in HIV-infected patients was 66% and that in healthy subjects was 64%. The PyV-DNA prevalence values in the HIV-infected and healthy subjects were 25% and 22%, respectively. The presence of a single type of PyV-miRNA in the saliva of HIV-infected patients ranged from 14% (MCPyV) to 61% (BKPyV) and in healthy subjects ranged from 14% (SV40) to 70% (BKPyV). Moreover, the PyV-miRNA in the saliva of both HIV-infected and healthy subjects exhibited higher prevalence than that in the paired plasma samples. Notably, the saliva of the HIV-infected and healthy subjects was more frequently positive for more than one PyV-miRNA than the paired plasma samples or the PyV-DNA in the paired saliva and plasma samples. Collectively, these data suggest that additional investigations of PyV-miRNA present in saliva may be useful to shed light on their utility as a surrogate for determining viral infection.