Human antibody response to Lethocerus salivary antigens as a correlate of protection to Buruli ulcer

Abstract

Mycobacterium ulcerans the causative agent of Buruli ulcer, a necrotizing skin disease, is an environmental mycobacterium thought to be transmitted from aquatic niches. It has previously been demonstrated that predatory aquatic insects could be both reservoirs and potential vectors of Mycobacterium ulcerans. Furthermore pre-exposure of laboratory mice to saliva of M. ulcerans infected aquatic insect could induce a protective immunity against skin lesion development. In a case-control study in Cameroon, we showed that total IgG titre antibody to Lethocerus saliva in healthy control subjects was higher than in Buruli ulcer patients (P = 0.013). This antibody response was specifically IgG1. Interestingly in addition to a few immunogenic salivary proteins (85, 64, 37 and 33 kDa bands), a 28 kDa protein derived from salivary glands homogenate of aquatic insects was able to bind to Mycobacterium ulcerans and to be recognized by IgG antibodies of healthy subjects in endemic areas. The antibody responses to the saliva of Lethocerus could be a valuable approach to the identification of an epidemiological marker that can be used to discriminate people at risk to develop Buruli ulcer among healthy population leaving in areas endemic for Mycobacterium ulcerans transmission.

Keywords : Buruli ulcer; Belostomatidae; salivary glands, Antibody response; Cameroon