Influenza virus A/HKx31 (X31, H3N2) was propagated in the allantoic cavity of 9-day-old embryonated chicken eggs at 35 ◦C. Titers were determined by an influenza plaque assay using MDCK cells [38]. Murine gammaherpesvirus (MHV) 68 clone g2.4 was used in the study and character- ...