Effects of Human Parvovirus B19 on Expression of Defensins and Toll-Like Receptors

Both cell-mediated and humoral immunity have been widely investigated for the roles in pathogenesis of human parvovirus B19 (B19) infection. However, little is known about the effects of B19 infection on innate immunity. In the current study, expression of alpha-human neutrophil peptides (HNP) 1-3, alpha-human defensin (HD) 5, HD6, beta-human defensin (hBD)-1, hBD-3, toll-like receptor (TLR) 4, TLR5, TLR7 and TLR9 in B19-nonstructural protein (NS)-1 or B19-viral protein (VP)-2 transfected COS-7 cells was investigated by reverse transcription (RT)-PCR or by western blots. Significantly increased HNP1-3, HD5, HD6, hBD1 and hBD3 mRNA levels were detected at both 24 h and 20 days post-transfection in COS-7 cells transfected with pEGFP-NS1. In pEGFP-VP2-transfected COS-7 cells, significantly increased HNP1-3, HD5, HD6, hBD-1 and hBD-3 mRNA expression levels were observed on day 20, albeit only hBD3 mRNA increased significantly at 24 h post-transfection. Additionally, TLR4, TLR5 and TLR7 proteins decreased significantly in COS-7 cells transfected with pEGFP-NS1 or pEGFP-VP2 at 48 h but significantly increased on day 20. Notably, only TLR9 protein increased significantly in the cells transfected with pEGFP-NS1 on day 20. No significant variation of TLRs was observed in cells transfected with pEGFP-NS1K334E, a single substitution mutantation of B19-NS1 protein without original cytotoxicity, at both 48 h and on day 20. These novel findings revealed the different effects of B19-NS1 and VP2 on the stimulation of defensins and TLRs and could provide a clue in understanding the roles of B19-NS1 and VP2 on innate immunity.