MCMV lacking M35 recruits antiviral CD3⁺ cells more efficiently to infected IE1⁺ tissue cells for the formation of protective nodular inflammatory foci (NIF).

<p>(A) For the quantification of focal infiltrates in the liver, tissue sections were collected randomly from four BALB/c mice per group on day 3 after i.v. infection with 2 x 10⁵ PFU of either MCMV-M35stop (M35stop) or MCMV-M35stop-REV (REV). Sections were stained by 2-color IHC (2C-IHC) for the expression of intranuclear viral IE1 protein (red staining) in infected liver tissue cells, as well as for the CD3ε molecule (black staining) expressed by T cells and NKT cells. Sections were counterstained with hematoxylin. Representative low-magnification overview images documenting a marked difference in the numbers of NIF (upper panels). Higher resolution images of representative foci that are marked by arrows in the overview images (lower panels). Scale bars represent 100 μm. (B) Data quantification and statistical evaluation of differences for representative tissue section areas of 40 mm². Each dot symbol (n = 29 for M35stop and n = 149 for REV) represents a focus of infection or a NIF in case of CD3⁺ cell recruitment. P values were calculated by using the unpaired two-tailed Student’s t-test with Welch’s correction to account for unequal variances. Differences between data sets are considered statistically significant for *p< 0.05 and***p<0.001.