Significant M78^- MCMV rescue by CD4⁺ T cell loss.

<p><b>a</b>. C57BL/6 mice were given WT or M78^- MCMV i.n. (3x10⁴ p.f.u.). 56d later sera were assayed for MCMV-specific IgG and IgM by ELISA. Naive = age-matched, uninfected controls. Each point shows the mean of results for 7 mice. M78^- MCMV elicited significantly less IgG response than WT (p<0.01). <b>b</b>. C57BL/6 mice were given WT or M78^- MCMV, or as a control MuHV-4 i.n. (3x10⁴ p.f.u.). 56d after MCMV infection or 10d after MuHV-4 infection, CD4⁺ T cells were purified from splenocytes, pooled from 2 mice per group, by depleting other cells with magnetic beads (Untouched mouse CD4 cell kit, Thermofisher). IFNγ production in response to MCMV-exposed or MuHV-4-exposed naive syngeneic spleen cells (1 p.f.u. / cell) was measured by ELIspot assay. Symbols show replicate wells, bars show means. <b>c</b>. C57BL/6 mice were given WT or M78^- MCMV i.n. (3x10⁴ p.f.u.). 56d later IFNγ production by splenocytes exposed to uninfected or MCMV-exposed naive syngeneic spleen cells was measured by ELIspot assay. Symbols show individual mice, bars show means. CD4⁺ T cell responses to WT and M78^- MCMV were not significantly different. <b>d</b>. BALB/c mice were depleted of CD4⁺ or CD8⁺ T cells (αCD4, αCD8) or left undepleted (cont), then given i.n. WT or M78^- MCMV (3x10⁴ p.f.u.). 10d later lungs and SG were plaque assayed for infectious virus. Symbols show individuals, bars show means. In lungs, immune depletions did not significantly change the ratio of WT to M78^- titers. In SG, CD4⁺ T cell depletion significantly reduced this ratio. <b>e</b>. Viral DNA loads of SG in <b>d</b> were determined by QPCR. Again CD4⁺ T cell depletion significantly reduced the ratio of WT to M78^- infection, that is significantly reversed the M78^- infection defect. <b>f</b>. Immunocompetent (IA^+/-) and MHC II^- (IA^-/-) C57BL/6 mice were given WT, M78^- or revertant (REV) MCMV i.n. (3x10⁴ p.f.u.). At d10 lungs and SG were plaque-assayed for infectious virus. Symbols show individual mice, bars show means. For both lungs (p<0.05) and SG (p<0.01), CD4⁺ T cell loss (IA^-/- mice) significantly increased M78^- plaque titers relative to WT or REV. <b>g</b>. For the mice in <b>f</b>, CD4⁺ T cell loss significantly increased M78^- viral DNA loads in SG relative to WT or REV (p<0.05). <b>h</b>. IA^-/- and IA^+/- mice were given i.n. WT, M131^- or M78 deletion mutant (M78^-I) MCMV. At d10 lungs and SG were plaque assayed for infectious virus. Symbols show individuals, bars show means. The ratio of M78^-I/WT salivary gland titers was significantly higher in IA^-/- than IA^+/- mice (p<0.01), while the ratio of M131^-/WT salivary gland titers was reduced. <b>i</b>. BALB/c mice were depleted of CD4⁺ T cells as in <b>d</b>, then given WT or M33^- MCMV i.n.. After 10d SG were plaque assayed for infectious virus. Symbols show individuals, bars show means. CD4⁺ T cell depletion increased WT MCMV SG infection but failed to rescue SG infection by M33^- MCMV. <b>j</b>. BALB/c mice were depleted of CD4⁺ T cells and given WT or M78^- MCMV i.n. as in <b>d</b>. At d10 salivary gland sections were stained for MHC II and MCMV IE1. UI = uninfected control. Arrows show example infected cells (speckled nuclear IE1 staining). These cells were all MHC II^- with WT MCMV and MHC II⁺ with M78^- MCMV. Images are representative of 6 mice per group.