[Identification of the immunogenic outer membrane proteins of relapsing fever Borrelia]

Borrelia duttonii, a causative agent of relapsing fever, is transmitted between the distinct microenvironments of the vector tick, Ornithodoros moubata, and a mammalian host. We identified the total and membrane fraction proteins of B. duttonii strain Ly isolated from a patient in Tanzania by using two-dimensional gel electrophoresis with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). The analyses of the total and membrane fractions from bacterial cultures incubated at 37°C identified 68 and 15 proteins, respectively. Since spirochaete clearance in mice is associated with an immunoglobulin M (IgM) and immunoglobulin G3 (IgG3)-mediated response, immunoblot analyses were used to identify the proteins reactive with IgM and IgG3 of gerbil serum against B. duttonii strain Ly. The outcome showed that six proteins (antigen p83/100, membrane-associated protein P66 (P66), flagellar filament outer layer protein, hypothetical protein BDU_412, vlp protein gamma subfamily (γ-Vlp) and flagellin (FlaB)) were identified against IgM, and four (antigen p83/100, P66, γ-Vlp and FlaB) of the six proteins also reacted with IgG3. It is believed that these proteins are immunodominant antigens for the host immune response. Some of these immunogenic proteins might be used as molecular diagnostic tools in the study of relapsing fever in Tanzania.