FIG. 4.

Detection of MHV-76 DNA in the tissues of mice at 5 months p.i. Four BALB/c mice were infected with 2 × 10⁵ PFU of MHV-76, and the lungs, livers, spleens, kidneys, and blood were harvested at 5 months p.i. Two uninfected mice were also harvested as negative controls, and one mouse infected 5 months previously with MHV-68 was harvested as a positive control. Viral DNA was extracted, and PCR amplification was performed on 1 μg of high-molecular-weight DNA. Samples containing MHV-68 viral DNA as a template (first lanes) or lacking DNA (second lanes) were used as positive and negative controls, respectively. (A) PCR amplification using primers specific for gp150. PCR products were analyzed by Southern blot hybridization with a ³²P-labeled gp150 probe to confirm specificity. (B) PCR amplification using primers specific for M3 (a gene absent from MHV-76). PCR products were analyzed by Southern blot hybridization with a ³²P-labeled M3 probe to confirm specificity.