CD40LG and infection: Indeed, 40% of patient sera may be negative for IgG and IgM antibodies against the DENV E and prM glycoproteins on day 3 after the onset of fever [19], and DENV prM/E glycoprotein-specific IgM antibodies were not generated during secondary DENV infections in patients from either Asia (28% IgM-negative) [27] or the Americas (33% IgM-negative) [19].