THE EFFECTS OF PREEXISTING COXSACKIEVIRUS-B4 MYOCARDIAL-DISEASE ON THE EXPRESSION OF COXSACKIEVIRUS-B3 MYOCARDITIS

OBJECTIVE: To assess the expression of coxsackievirus B3 (CB3) myocard itis in mice with pre-existing CB4 myocardial disease. DESIGN: Double blind comparative study of CB3 myocarditis in CD1 mice with or without prior CB4 induced cardiac damage. INTERVENTIONS: Antecedent myocardia l injury was produced by CB4 infection intraperitoneally at age two da ys. Two to three weeks later, when CB4 myocarditis was established, in fected and control animals were inoculated intraperitoneally with CB3. They were then sacrificed over a 45-day period. Virus and neutralizin g antibody titres were measured on days 3 and 13 after CB3 infection, respectively. The incidence of myocarditis and the intensity of histop athological changes (assessed according to a semiquantitative grading scale from 0 to 4) over a 45-day period were compared. MAIN RESULTS: A mong animals with prior CB4 disease, CB3 titres were lower (2.3 +/- 1. 7 versus 3.6 +/- 0.8, tissue culture infective dose 50, P=0.05) and ne utralizing antibody response was slightly higher. The incidence of myo carditis was diminished (59.1 versus 89.3%, P=0.01) and the indices of pathological changes were lower but the were not significant (0.68 +/ - .54 versus 1.10 +/- 0.20, 1.38 +/- 0.43 versus 1.50 +/- 0.25, 0.56 /- 0.56 versus 1.26 +/- 0.75, 0.38 +/- 0.58 versus 1.30 +/- 0.78, 0.12 +/- 0.28 versus 0.47 +/- 0.2 on days 3, 9, 13, 30 and 45 post infecti on, respectively, P>0.1). CONCLUSION: These results demonstrate that p rior exposure to CB4 offers some protection from subsequent CB3 infect ion. Moreover, they show that antecedent CB4 myocardial damage does no t predispose to a worsend expression of CB3 myocarditis.