gamma-Herpesvirus-induced protection against bacterial infection is transient

Abstract

Herpesviruses are widely disseminated in the population and establish lifelong latency, which is associated with a variety of pathological consequences. A recent report showed that mice latently infected with either murine gamma-herpesvirus-68 (gammaHV68) or murine cytomegalovirus (mCMV), mouse pathogens genetically similar to the human herpesviruses, Epstein-Barr virus, Kaposi's sarcoma-associated herpesvirus, and cytomegalovirus, had enhanced resistance to subsequent bacterial infection, suggesting protective as well as deleterious effects of latency. Here we confirm that latent gammaHV68 infection confers protection against subsequent infection with Listeria monocytogenes. However, the effect is transient, lasting only a few months.

FIG. 1.

Herpesvirus latency-mediated protection against subsequent bacterial infection is finite. Mice latently infected with γHV68 for the indicated lengths of time (indicated by “+” and open circles) and uninfected age-matched control mice (indicated by “−” and closed circles) were challenged with L. monocytogenes. The number of viable bacteria detected in the spleens (A) and livers (B) of mice 3 d after challenge are shown. In addition, the amount of latent γHV68 present in the above groups of mice was assessed using quantitative real-time PCR, and the number of copies of viral ORF50 gene detected in DNA isolated from splenic tissue (C) are shown. Each symbol represents data obtained from an individual mouse and bars indicate the medians calculated from the data. n.d., not detected; NS, not significant; **p < 0.05 as determined using the Mann-Whitney rank test (two-tailed, 95% CI).

FIG. 2.

Temporary elevation in the levels of inflammatory cytokines following the establishment of γ-herpesvirus latency. The levels of IFN-γ (A) and TNF-α (B) in the sera of uninfected control (C) mice and mice latently infected with γHV68 for the indicated lengths of time were assessed using a cytometric bead-based immunoassay. Each symbol represents data obtained from an individual mouse, and bars indicate the medians calculated from the data. NS, not significant; **p < 0.05 as determined using the Mann-Whitney rank test (two-tailed, 95% CI).