In this study, MHC class II positive regulators IFN-γ, transactivator CIITA and MHC class II-associated invariant chain (CD74), which is a type II integral membrane protein essential for proper MHC class II folding in the endoplasmic reticulum (Matza et al., 2003), were suppressed to some extent at 10 days after the CVS-11 infection compared with the HEP-Flury infection. This evidence concerns the gene CD74 and infection.