Administration of Lactococcus lactis strain Plasma induces maturation of plasmacytoid dendritic cells and protection from rotavirus infection in suckling mice

Lactococcus lactis subsp. lactis JCM 5805 (LC-Plasma) is a strain of lactic acid bacteria (LAB) that activates murine and human plasmacytoid dendritic cells (pDCs) to express interferons (IFNs). Oral administration of LC-Plasma drastically decreased fatality levels caused by parainfluenza virus infection in a murine model. In this study, we investigated the anti-viral effects of oral administration of LC-Plasma using a suckling mouse model of rhesus rotavirus (RV) infection. LC-Plasma-fed mice showed improvement in retardation of body weight gain, fecal scores, and a reduction in RV titer in the feces when compared to control mice. The mechanism of anti-viral effects elicited by LC-Plasma administration was investigated using naive mice: in the LC-Plasma -fed mice, lamina propria (LP) pDCs resident in the small intestine were significantly matured and the proportion of pDCs was increased. The expression levels of anti-viral factors induced by IFNs, such as Isg15, Mx1, Oasl2 and Viperin, and an anti-bacterial factor Reg3γ, were up-regulated in the small intestinal epithelial cells (IECs) of LC-Plasma-fed mice. The specific LAB strain may affect the anti-viral immunological profile of IECs via maturation of LP pDCs, leading to protection from RV virus infection in vivo.