Another limitation of our workup was a lack of CSF HHV-6 IgM and IgG titers which may have distinguished an incidental ci-HHV-6 finding versus active infection superimposed on ci-HHV-6 since intrathecal antibody production may be a distinguishing feature between an incidental ci-HHV-6 finding and active infection superimposed on ci-HHV-6. This evidence concerns the gene CD40LG and infection.