Coxsackievirus B3 infection induces anti-flavoprotein antibodies in mice

Abstract

SUMMARYEnteroviruses, the most common cause of acute myocarditis, are also supposed aetiological agents of dilated cardiomyopathy. Autoantibodies (anti-M7; Klein & Berg, Clin Exp Immunol 1990; 58:283±92) directed against flavoproteins with covalently bound flavin (a Fp-Ab; Otto et al., Clin Exp Immunol 1998; 111:541±2) are detected in up to 30% of sera of patients with myocarditis and idiopathic dilated cardiomyopathy (IDCM). Mice inoculated with a myocarditic variant of coxsackievirus B3 (CVB3) were employed to study the occurrence of serum aFp-Ab following viral infection. The presence of aFp-Ab was analysed by Western blotting with the flavoprotein antigens 6-hydroxy-d-nicotine oxidase (6HDNO) and sarcosine oxidase (SaO). Of 10 sera from CVB3-infected mice, five showed a strong reaction with both antigens. The sera were reactive also to the mitochondrial covalently flavinylated proteins dimethylglycine dehydrogenase and sarcosine dehydrogenase. Sera of non-infected mice did not react with these antigens. A 6HDNO mutant protein with non-covalently bound FAD no longer reacted on Western blots with sera of CVB3-infected mice. Preincubation with FAD abolished or reduced the reaction of the sera with the 6HDNO antigen. At 2 weeks p.i. the aFp-Ab were of the IgM and IgG isotypes, at 7 and 9 weeks p.i. of the IgG isotype. The sera of CVB3-infected mice reproduced closely the antigenic specificity of the anti-M7 sera of patients, lending further support to the role of coxsackieviruses in the pathogenesis of IDCM.

Comparative immunoproteome analysis of the response of susceptible A.BY/SnJ and resistant C57BL/6 mice to Coxsackievirus B3-infection

“…A variety of these proteins are avoproteins (medium-chain speci c acyl-CoA dehydrogenase, longchain speci c acyl-CoA dehydro-genase, isovaleryl-CoA dehydrogenase, electron transfer avoprotein subunit beta, succinate dehydrogenase avoprotein subunit Sdha and [ubiquinone] iron-sulfur protein Sdhb) which have already been described as cardiac antigens of auto-antibodies a er CVB3-infection in mice. [43] Since mitochondria are highly abundant in cardiomyocytes, protein release in case of myocardial damage might lead to substantial antibody formation with functional relevance. e high number of gap-junctions facilitating the penetration of plasma membrane allows antibodies to gain access even to intracellular targets [30] and might contribute to energy limitations supposed already from altered levels of transcripts and proteins involved in lipid metabolism [21] and respiratory electron transport chain.…”

Specific stimulation of peripheral blood mononuclear cells from patients with acute myocarditis by peptide-bound flavin adenine dinucleotide (FAD), a naturally occurring autologous hapten

“…If α ‐Fp antibodies were induced following myocyte destruction associated with the inflammation of the myocard and liberation of mitochondrial antigens, one would expect to detect them in the serum of mice infected with Coxsackie virus B3. Indeed, mice infected with this virus present α ‐Fp antibodies in their sera [15].…”