A part of the VP4 capsid protein exhibited by coxsackievirus B4 E2 is the target of antibodies contained in plasma from patients with type 1 diabetes

Abstract

The capsid protein VP4 was identified previously as the target of antibodies contained in plasma enhancing the coxscakievirus B4 (CV-B4) E2-induced production of IFN-alpha by peripheral blood mononuclear cells (PBMCs). The sequence of VP4 recognized by these antibodies was investigated. This sequence was identified as amino acids 11 to 30 by using synthetic overlapping peptides spanning VP4(CV-B4 E2) in competition experiments for antibodies enhancing the CV(B4 E2) induced production of IFN-alpha by PBMCs. This amino acid sequence was the major target of anti-VP4 antibodies according to enzyme-linked immunosorbent assays (ELISA). There was a positive correlation between the levels of anti-VP4 and anti-VP4(11-30) peptide antibodies detected by ELISA. The levels and the prevalences of these antibodies were significantly higher in patients with type 1 diabetes than in healthy controls. The proportions and the levels of those antibodies in patients were independent of HLA-DR alleles, age, or presence of ketosis in blood and were not associated with newly or previously diagnosed disease. The VP4(CV-B4 E2) amino acid sequence was submitted to the Swiss-model in project mode to visualize the possible shape of the sequence of VP4 corresponding to amino acids 11-30 which appeared to be constituted principally by an non-structured loop. In conclusion, the sequence of VP4 corresponding to amino acids 11-30, or a part of it plays a role in the plasma-dependent enhancement of CV-B4 E2-induced production of IFN-alpha by PBMCs, suggesting that at 37 degrees C the virus exhibits that region of VP4 to antibodies.