To further demonstrate that these viral genome positive cells are actively infected, and to exclude the possibility of endocytic uptake of virus or abortive infection, we performed RT-PCR analysis on endothelial enriched and depleted lung cells (Fig. 8D) . The transcript for the endothelial cell marker CD31 was robustly detected in the endothelial enriched lung cells from each of the four mice analyzed, whereas a very low level of this transcript was detected from the CD31 depleted lung cells of only one out of the four mice analyzed. In combination with flow cytometric analysis (Fig. S5B) , these data support that our enrichment strategy was effective in isolating CD31+ cells from total lung cells. Additionally, the viral pol III-1 transcript was detected from both endothelial cell enriched and depleted lung cells of cHV68 infected mice, and was absent from lungs of mock infected mice. Detection of viral gene transcripts from lung cells indicates virus infection of these cells. Notably, within each infected mouse, pol III-1 detection was comparable between endothelial enriched and CD31-depleted lung cell populations, suggesting that detection of this viral transcript in the endothelial cell population was not due a few contaminating infected non-endothelial cells. Taken together, these data demonstrate cHV68 infection of endothelial cells in vivo.