Fig. 1.

Oral infection of neonates with MCMV. (A) Six-day-old C57BL/6 pups were infected with 1,000 PFU of MCMV (Smith) by gavage using soft polyethylene tubing. At 4, 7, or 10 days after infection, total RNA was isolated from the brain, liver, lung, kidney, spleen, and salivary glands of individual mice and examined for MCMV IE-1 gene expression. Detection of MCMV IE-1 mRNA was performed by RT-PCR with Southern analysis, where spliced IE-1 RNA (188 bp) was distinguished from contaminating IE-1 genomic DNA (310 bp) on the basis of size. (B) The same RNA preparations were analyzed by RT-PCR for expression of the reference gene β-actin (representative results are shown for lung samples). Similar results were obtained in an independent experiment in which total RNA isolated from the lung and spleen of neonates orally infected with MCMV was evaluated at 8 and 15 days after infection (data not shown).