LACTB and disease arising from reactivation of latent virus: As predicted, the frequency of beta-lactamase positive, infected germinal center B cells was significantly decreased in SR-BI-/- mice (Fig. 5B, gating strategy in Fig. 5A), indicating that germinal center B cells of SR-BI-/- mice, although increased in abundance, were less capable of supporting MHV68 latent infection.