Serodiagnosis of louse-borne relapsing fever with glycerophosphodiester phosphodiesterase (GlpQ) from Borrelia recurrentis

Human louse-borne relapsing fever occurs in sporadic outbreaks ih central a nd eastern Africa that are characterized by significant morbidity and morta lity. Isolates of the causative agent, Borrelia recurrentis, were obtained from the blood of four patients during a recent epidemic of the disease in southern Sudan. The glpQ gene, encoding glycerophosphodiester phosphodieste rase, from these isolates was sequenced and compared with the glpQ sequence s obtained from other relapsing-fever spirochetes. Previously we showed tha t GlpQ of Borrelia hermsii is an immunogenic protein with utility as a sero logical test antigen for discriminating tick borne relapsing fever front Ly me disease. In the present work, we Cloned and expressed the glpQ gene from B. recurrentis and used recombinant GlpQ in serological tests. Acute- and convalescent-phase serum: samples obtained from 42 patients with louse-born e relapsing fever were tested with an indirect immunofluorescence assay (IF A) and an enzyme-linked immunosorbent assay (ELISA) that used whole cells o f B. recurrentis and with immunoblotting to whole-cell lysates of the spiro chete and Escherichia: coli producing recombinant GlpQ. The geometric mean titers of the acute- and Convalescent-phase serum samples measured by IFA w ere 1:83 and 1:575, respectively. The immunoblot analysis identified a high level of reactivity and seroconversion to GlpQ, and the assay was more sen sitive than the whole-cell IFA and ELISA using purified, recombinant histid ine-tagged GlpQ. Serum antibodies to GlpQ and other antigens persisted for 27 Sears in one patient. We conclude that assessment of anti-GlpQ antibodie s will allow serological confirmation of louse-borne relapsing fever and de termination of disease prevalence.