CD40LG and infection: When comparing the serology of IgM + and IgM − samples, we found that the titers of IgA against N and S2 in groups of < 21d (p = 0.009 and p = 0.02 respectively) and IgA against N, S1 and S2 ≥ 41d since infection (p = 0.033, p = 0.02 and p = 0.019 respectively) were higher in IgM + HWs.