Figure 1. Long-term MuHV-4 latent loads depend on viral M2 expression and host H2 haplotype.

Mice were infected intranasally with wild-type (vWT) or M2⁻ (vM2FS) viruses. At d14 or d50 post-infection spleens were removed and titrated for reactivation-competent virus by explant co-culture with BHK-21 cells. Each point shows the titre of one mouse. The horizontal bars show arithmetic means. The dashed horizontal line represents the limit of assay detection. Pre-formed infectious virus, as measured by the parallel titration of equivalent frozen/thawed samples, was below the limit of assay detection. At d50 post-infection the vM2FS latent load was significantly higher than the vWT latent load in BALB/c (P = 0.011) and DBA/2 (P = 3×10⁻⁵) and close to significance in B6.C.H2^d (P = 0.056), but not in C57BL/6 (P = 0.228) and FVB-N (P = 0.347) by a one-tailed Student's t-Test. This was also confirmed by combining all data from H2^d mouse strains (P<0.0001) but not from non-H2^d mice (P = 0.71) using a 2-way non-parametric ANOVA Friedman's test. Data were reproducible over two independent experimental groups.