Antiviral responses of human Leydig cells to mumps virus infection or poly I:C stimulation

The immuno-privileged status of the testis is essential to the maintenance of its functions, and innate immunity is likely to play a key role in limiting harmful viral infections, as demonstrated in the rat. In men mumps virus infects Leydig cells and has deleterious effects on testosterone production and spermatogenesis. The aim of this study was to test whether mumps virus infection of isolated human Leydig cells was associated with an inhibition of their innate antiviral defences.

Leydig cell production of mRNA and protein for interferons (IFNs) and of three antiviral proteins-2'5' oligoadenylate synthetase (2'5'OAS), double-stranded RNA-activated protein kinase (PKR) and MxA-was investigated, in the absence or presence of mumps virus or viral stimuli including poly I:C, a mimetic of RNA viruses replication product.

Stimulated or not, human Leydig cells appeared unable to produce routinely detectable IFNs alpha, beta and gamma. Although the level of PKR remained unchanged after stimulation, the expression of 2'5'OAS and MxA was enhanced following either mumps virus or poly I:C exposure (P < 0.05 versus control).

Overall, our results demonstrate that mumps virus replication in human Leydig cells is not associated with a specific inhibition of IFNs or 2'5'OAS, MxA and PKR production and that these cells display relatively weak endogenous antiviral abilities, as opposed to their rat counterparts.