In addition to the in-house assays and commercial ECLIAs, utilization and comparison of the flow cytometry based assay allowed the separate detection of IgM and IgG antibodies binding to S-expressing cells, which enables generally the discrimination between recent viral infection (IgM positive/IgG negative) and past infections (IgM positive/IgG positive or IgM negative/IgG positive). This evidence concerns the gene CD40LG and viral infectious disease.