Multiple virus infection alters rotavirus replication and expression of cytokines and Toll-like receptors in intestinal epithelial cells.

Two live oral rotavirus vaccines have shown to be effective in protecting young children from severe illness in developed and middle income countries, but their efficacy is significantly lower in low income countries. One of the reasons for this lower efficacy may be mixed virus infection in the gut that is commonly encountered among infants in the developing world. We investigated whether multiple virus infection interferes with rotavirus replication and alters host response by comparing single and mixed enteric virus infections in Caco-2 cells. We observed a dramatic reduction in rotavirus replication and growth in mixed rotavirus, astrovirus and enterovirus infection compared to single rotavirus infection. By contrast, the levels of astrovirus and enterovirus RNA in mixed infection remained unchanged when compared to those of the corresponding single virus infection. We then examined cells with single or multiple virus infections for the expression of 10 cytokine genes and demonstrated elevated expressions for 7 (IFN-α, IFN-β, IFN-γ, TNF-α, IL-6, IL-8, and IL-17) in dual rotavirus and enterovirus or triple rotavirus, enterovirus and astrovirus-infected cells but only 3 (IFN-β, TNF-α, and IL-8) in dual rotavirus and astrovirus-infected cells. We further observed elevated levels of TLR4, TLR5, TLR7 and TLR9 mRNAs in cells with rotavirus and enterovirus or rotavirus, enterovirus and astrovirus infections when compared to single rotavirus infections. Our data suggest that rotavirus infection is susceptible to interference by other enteric viruses in the gut, which could result in reduced virus replication and contribute to lower immunogenicity and efficacy of oral rotavirus vaccines in low income countries.