The prevalence of enteroviral RNA and protein in mitral valves of chronic rheumatic heart disease.

Acute Rheumatic Fever/ Rheumatic Heart Disease (ARF/RHD), a sequel of group A streptococcal (GAS) infection, even today constitutes a public health issue in developing countries including India. Differences in the prevalence of ARF/RHD in countries with a similar prevalence of GAS infections indicate the role of other cofactors in pathogenesis of RHD. We investigated the prevalence of enterovirus (EV) in RHD by probing for both EV RNA and VP1 protein using Nonisotopic In Situ Hybridization (NISH) and Immunohistochemistry (IHC) respectively in 75 valvectomy specimens obtained from RHD cases. Twenty-eight (37%) of the valves showed tissue inflammation with lymphocytic infiltration in a majority of the cases. Twenty-six and 27 (38% and 40%) of the 68 valves showed the presence of EV by IHC and NISH respectively, indicating a very good association between the two tests; however, only about 46 to 48% of them exhibited tissue inflammation. In eight cases (12%) the EV genome was detectable in absence of VP1 protein perhaps indicating a latent viral infection. Due to a high degree of endemicity of EV in India, we are tempted to speculate that EV may be responsible for the severity and rapid progression of RHD. The virus could either be working synergistically with GAS or could be an opportunist infecting damaged valves.