The association of enteroviruses with
myocardial disease has been investigated extensively by molecular
biological techniques to detect
viral RNA, but remains controversial. This retrospective study investigated the involvement of enterovirus in
myocarditis or
dilated cardiomyopathy (DCM) by detection of
viral antigens in myocardial samples from a new patient series using an optimized immunohistochemical technique.
Formalin-fixed,
paraffin-embedded biopsy, autopsy or explanted myocardial tissue samples were obtained from 136 subjects. These comprised histologically proven cases of acute fatal
myocarditis (n=10), DCM (n=89, including 10 patients with healing/borderline
myocarditis) and a comparison group of samples from 37 unused donor hearts and cases with other conditions. A
monoclonal antibody 5-D8/1 directed against a conserved, non-conformational
epitope in
capsid protein VP1 was employed for broad detection of different enterovirus serotypes. Investigations were performed blindly. Histological sections from 7 of 10 fatal
myocarditis cases, 47 of 89 patients (52.8%) with DCM were positive for the viral
capsid protein VP1 by immunohistochemical staining. Consecutive sections of positive samples were negative when the antibody was omitted or replaced with subclass- and concentration-matched normal mouse
IgG. In contrast, only 3 of 37 samples (8.1%) in the comparison group were positive (Yates corrected chi(2)=19.99, P<0.001: odds ratio =12.68). VP1 staining was distributed in individual or grouped myofibers and localized in the cytoplasm of myocytes. In some cases, VP1 was detected in only a few myofibers within an entire section. These results provide further evidence of enterovirus involvement in a high proportion of DCM cases and demonstrate that VP1 is present in disease stages from acute
myocarditis, healing
myocarditis to end-stage DCM requiring
cardiac transplantation, indicating translation of
viral protein during persistent
enterovirus infection.