Serological diagnosis of leptospiral uveitis by HbpA IgG ELISA

Leptospirosis is a zoonotic disease that is highly prevalent in tropical countries; uveitis is one of the manifestations of leptospirosis. The leptospiral aetiology of uveitis is difficult to predict because of overlapping clinical symptoms with uveitis due to other causes. The objective of this study was to evaluate the leptospiral haemin-binding protein HbpA as a diagnostic antigen for the serodiagnosis of leptospiral uveitis. Serum samples from patients, clinically diagnosed with leptospiral uveitis, were tested by ELISA for anti-HbpA antibodies and compared against the 'gold standard' microscopic agglutination test (MAT). Non-leptospiral uveitis and normal healthy individuals were used as controls. A total of 60 serum samples from patients suffering from leptospiral uveitis were studied, obtained from Aravind Eye Hospital, Madurai. Anti-HbpA IgG antibodies were detected in 92 % of patients clinically diagnosed with leptospiral uveitis, indicating that it is more sensitive than MAT, which had a seropositivity of only 50 %, and better than the commercially available Pan Bio IgM ELISA (81 %). The mean anti-HbpA antibody titre was significantly higher in leptospiral uveitis patients compared with controls (P<0.05). The antigen showed negligible cross-reactivity with non-leptospiral uveitis samples and cataract controls. We conclude that HbpA IgG ELISA identified cases of uveitis with leptospirosis aetiology and proved to be useful in differentiating them from other forms of uveitis.