Progressive hearing loss and virus inoculum effect on progression of hearing loss in MCMV infected mice.

<p><b>(A)</b> MCMV infected mice exhibit increased ABR threshold as function of age. Newborn mice infected with uncloned Smith MCMV(●; n = 12) or mock infected (<b>○;</b> n = 15) were tested at approximately 3,7, and 12 months and ABR thresholds determined. Note increasing mean ABR threshold in infected mice at 7 months of age and increase in ABR threshold for both infected and mock infected groups of mice at 12 months of age. At each time point the mean ABR thresholds of mock vs. infected mice were significantly different (p<0.001 two-way Anova with Bonferroni post-test correction). (<b>B)</b> Dose dependence of progressive hearing loss and delayed onset of hearing loss. Newborn mice were inoculated with recombinant, BAC cloned MCMV(50PFU ●; 200PFU ▲) or mock uninfected (<b>○</b>) and tested for auditory function at PNd42 or PNd78. Each symbol represents one ear tested (n = 96 mock, n = 36(50PFU), n = 52(200PFU)). Note the increase in median ABR threshold in mice given 50 PFU between PNd42 and PNd78 as compared to mock infected animals. (<b>**</b>) indicates significant differences (p<0.01) between groups with increase in ABR thresholds as determined by Kruskal-Wallis test of medians with Dunn post-test correction. <b>(C)</b> Magnitude of ABR thresholds in cochlea with progression of hearing loss. The change (dB) in individual cochlea exhibiting an increase in ABR threshold between d42 and d78 (Δ ABR threshold) was plotted for each group and medians compared. Number of cochlea with progression that were analyzed were (mock = 27; 50PFU = 13; 200PFU = 26). Statistically significant differences between median Δ ABR threshold of mock vs 50PFU, (p<0.01) and mock vs. 200PFU (p<0.001) by Kruskal-Wallis test of medians with Dunn post-test correction.