Data from patients with acute HAV, HCV and HEV infection suggests: (1) virus-specific pIgA is detectable in patients during the acute phase of infection (Fig. 2); (2) transient profile of serum anti-HCV pIgA may differ from total anti-HCV IgA, and discriminate acute from chronic HCV infections (Fig. 3B); (3) anti-HEV pIgA is not correlated with and has higher specificity than anti-HEV IgM; and (4) anti-HAV pIgA is undetectable in HAV-vaccinated individual and may be more specific to natural infection. Here, CD40LG is linked to infection.