FIG. 2.
Titers of MHV in livers of animals infected with parental and recombinant viruses. C57BL/6 mice were infected intrahepatically with 500 PFU of MHV-A59, MHV-2, MHV-4, and the recombinants SA59R13, Penn98-1, and S4R21, and sacrificed at days 1, 3, 5, and 7 p.i. Virus titers were determined by plaque assay. Virus titers are presented as logarithmic means of PFU per gram of liver. Error bars represent logarithmic standard deviation. The limit of detection was 300 PFU/g of liver. Numbers of mice examined were as follows: MHV-A59, 18; MHV-2, 15; MHV-4, 8; SA59R13, 23; Penn98-1, 19; and S4R21, 24. At day 5 p.i., replication of Penn98-1 was significantly higher than that of SA59R13 and S4R21 (Wilcoxon's rank sum test: P < 0.03 and P < 0.004, respectively).