The diagnostic usefulness of an
enzyme-linked
immunosorbent assay (ELISA) using a purified recombinant
ribosome recycling factor from Brucella melitensis (CP24
antigen) was tested in human and canine
infections caused by smooth and rough Brucella species, respectively. Anti-CP24
antibodies were detected in 9 (43%) of 21 consecutive cases of canine
brucellosis and in 8 (53%) of 15 dogs followed for 60 days after the diagnosis of acute
brucellosis. Among eight patients with acute
brucellosis, anti-CP24
antibodies were detected in four in the 10 weeks following diagnosis, but the remaining four were negative during the whole follow-up (22 weeks). The frequency of anti-CP24
antibodies was also low among 24 patients with subacute
brucellosis and 23 patients with
chronic illness (29 and 26%, respectively). While all patients positive for anti-CP24
antibodies were also positive for
antibodies to total cytoplasmic
proteins of Brucella (CP), five were negative for
antibodies to another cytoplasmic
protein, the Brucella
lumazine synthase (BLS). When a larger sample of 35 human sera negative for anti-BLS
antibodies was assayed, 85.7% were positive for anti-CP24
antibodies, suggesting that the combined measurement of both reactivities could yield a higher sensitivity than any test alone. To test this hypothesis, an ELISA combining both
antigens was designed. The percentage of positive results among chronic cases was higher for this assay than for the individual measurement of anti-CP24 or anti-BLS
antibodies (83 versus 26 and 65%, respectively) and was closer to the value obtained for anti-CP
antibodies (91%). The frequency of anti-CP24
antibodies is low in both canine and human
brucellosis. In the latter case, however, an ELISA combining CP24 and BLS is more sensitive than assays measuring anti-CP24 or anti-BLS
antibodies separately and almost as sensitive as the ELISA using CP.