Measles virus-specific plasma cells are prominent in subacute sclerosing panencephalitis CSF

Objective: To demonstrate the specificity of expanded CD138(+) plasma cell clones recovered from the CSF of a patient with subacute sclerosing panencephalitis ( SSPE) for measles virus (MV). Methods: IgG variable region sequences of single-antibody-secreting CD138(+) cells sorted from SSPE CSF were amplified by single-cell PCR and analyzed. Human IgG1 recombinant antibodies (rAbs) were produced from four expanded CD138(+) clones and assayed for immunoreactivity against MV proteins. Results: Clonal expansion was a prominent feature of the SSPE plasma cell repertoire, and each of the four rAbs assayed was specific for either the MV fusion or the MV nucleocapsid protein. Conclusions: Expanded plasma cell clones in the CSF of patients with subacute sclerosing panencephalitis produce disease-relevant antibodies. Recombinant antibodies derived from CSF B cells could provide a tool to identify target antigens in idiopathic inflammatory disorders.