Infection of neonates with murine gammaherpesvirus 68 results in enhanced viral persistence in lungs and absence of infectious mononucleosis syndrome.

We used the murine gammaherpesvirus 68 (gammaHV-68), which serves as a model for human gammaherpesvirus infection, to determine whether age at infection altered the pattern of gammaherpesvirus pathogenesis. We infected mice intranasally at 8 days old (pups) and 6 weeks old (adults) to investigate differences in gammaHV-68 pathogenesis. There was no difference between adults or pups in acute infection in the lungs at 6 days post-infection (p.i.). However, mice infected as pups exhibited a more disseminated viral infection with viral DNA detected in the spleen, liver and heart as measured by quantitative PCR (Q-PCR). In addition, viral DNA was detected in the lungs of mice infected as pups until 60 days p.i. Three viral transcripts (M2, M3 and M9) were expressed at both 30 and 60 days p.i. In contrast, no viral DNA or mRNA expression was detected in lungs of mice infected as adults at 30 or 60 days p.i. Mice infected as adults experienced a peak in latent infection in the spleen at 16 days p.i., corresponding with an increase in splenic weight and expansion of the Vbeta4+ CD8+ T-cell population, similar to infectious mononucleosis observed following infection of young adults with Epstein-Barr virus. However, the increase in splenic weight of infected pups was not as pronounced and no significant increase in Vbeta4+ CD8+ T-cell expansion was observed in infected pups. Together, these data suggest that the pathogenesis of murine gammaherpesvirus gammaHV-68 is age-dependent.