Intrathecal Antibody Production in Two Cases of Yellow Fever Vaccine Associated Neurotropic Disease in Argentina

Abstract

During the period 2007?2008 several epizootics of Yellow fever with dead of monkeys occurredin southeastern Brasil, Paraguay, and northeastern Argentina. In 2008 after a Yellow fever outbreak an exhaustive prevention campaign took place in Argentina using 17D live attenuatedYellow fever vaccine. This vaccine is considered one of the safest live virus vaccines, although serious adverse reactions may occur after vaccination, and vaccine-associated neurotropicdisease are reported rarely. The aim of this study was to confirm two serious adverseevents associated to Yellow fever vaccine in Argentina, and to describe the analysis performedto assess the origin of specific IgM against Yellow fever virus (YFV) in cerebrospinalfluid (CSF). Both cases coincided with theYellow fever vaccine-associated neurotropicdisease case definition, being clinical diagnosis longitudinal myelitis (case 1) and meningoencephalitis (case 2). Specific YFV antibodies were detected in CSF and serum samples in both cases by IgM antibody-capture ELISA. No other cause of neurological disease wasidentified. In order to obtain a conclusive diagnosis of central nervous system (CNS) infection the IgM antibody index (AIIgM) was calculated. High AIIgM values were found in both cases indicating intrathecal production of antibodies and, therefore, CNS post-vaccinal YFV infection could be definitively associated to YFV vaccination.