A possible etiological link between the onset of endemic
pemphigus in Tunisia and
bites of Phlebotomus papatasi, the vector of zoonotic
cutaneous leishmaniasis, has been previously suggested. We hypothesized that the immunodominant P. papatasi
salivary protein PpSP32 binds to
desmogleins 1 and 3 (Dsg1 and Dsg3), triggering loss of tolerance to these
pemphigus target
autoantigens. Here, we show using far-Western blot that the recombinant PpSP32
protein (rPpSP32) binds to epidermal
proteins with a MW of approximately 170 kDa. Coimmunoprecipitation revealed the interaction of rPpSP32 with either Dsg1 or Dsg3. A specific interaction between PpSP32 and Dsg1 and Dsg3 was further demonstrated by ELISA assays. Finally, mice immunized with rPpSP32 twice per week exhibited significantly increased levels of anti-Dsg1 and -Dsg3
antibodies from day 75 to 120. Such
antibodies were specific for Dsg1 and Dsg3 and were not the result of cross-reactivity to PpSP32. In this study, we demonstrated for the first time to our knowledge a specific binding between PpSP32 and Dsg1 and Dsg3, which might underlie the triggering of anti-Dsg
antibodies in patients exposed to sand fly
bites. We also confirmed the development of specific anti-Dsg1 and -Dsg3
antibodies in vivo after PpSP32 immunization in mice. Collectively, our results provide evidence that environmental factors, such as the exposure to P. papatasi
bites, can trigger the development of autoimmune
antibodies.