Coxsackievirus B3 genomes detected by polymerase chain reaction: evidence of latent persistency in the myocardium in experimental murine myocarditis.

We have investigated the time course after infection in coxsackievirus B3 murine myocarditis to determine the extent (if any) of persistent or latent infection that might be responsible for recurrence. We employed a polymerase chain reaction (PCR) method that can detect an extremely small amount of genome by amplification techniques in four-week-old BALD/c mice (n = 140) infected with coxsackievirus B3 by a single intraperitoneal injection of 1 x 10(4) plaque-forming units (PFU)/mouse (Group 1) and 1 x 10(2) PFU/mouse (Group 2). Mice were sacrificed on days 3, 5, 7, 10, 14, 21 and 28, and their hearts were resected for RNA extraction. Single chain DNA was synthesized from 1 microgram of RNA and the viral genome was amplified by PCR. The virus genome was strongly amplified in Group 1 from days 3 to 10, and in Group 2 from days 5 to 7, but afterwards both amplifications rapidly diminished. However, a positive signal, though very faint, persisted in both groups until day 28, by which time all histological evidence of myocarditis had disappeared in Group 2. Our results demonstrated that there was persistent or latent virus infection in the myocardium throughout the entire study period of 28 days. Such persistence might provide a pathomechanism for the exacerbation and recurrence of myocarditis.