Enterovirus‐specific serum IgA antibody responses in patients with acute infections, chronic cardiac disease, and recently diagnosed insulin‐dependent diabetes mellitus

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Abstract
Employing an antibody class capture ELISA, we assessed the significance of enterovirus (EV)‐specific serum IgA (EV‐IgA) as a marker of EV infection. EV‐IgA was detectable in 64% of sera from patients with acute illnesses which may be attributable to EV infection who also had EV‐IgM, but also in 30% of sera from patients without evidence of EV infection. High EV‐IgA levels were more closely associated with the presence of EV‐IgM and were demonstrable in 39% of patients with acute infections who were EV‐IgM positive, compared to 3% of those who were EV‐IgM negative. Among patients with acute EV infection confirmed by virus isolation, EV‐IgA was present in 67% and EV‐IgM was present in 83%. As a marker of acute EV infection, EV‐IgA is less sensitive and less specific than EV‐IgM. EV‐IgA responses in patients with chronic cardiac disease paralleled EV‐IgM responses in some cases but there was no significant association between these two antibody responses in this group as a whole. High EV‐IgA responses were present in 20% of EV‐IgM positive and 21% of EV‐IgM negative patients, and may persist as a result of an immunoregulatory defect leading to virus or antigen persistence at mucosal surfaces. High EV‐IgA levels were also detectable in 33% of EV‐IgM positive newly diagnosed insulin‐dependent diabetics but in none who were EV‐IgM negative, which suggests that most EV infections in these patient were acute rather than persistent.