Polar tube proteins of microsporidia of the family Encephalitozoonidae

Encephalitozoonidae are microsporidia associated with human infections incl uding hepatitis, encephalitis, conjunctivitis, and disseminated disease. Mi crosporidia produce a small resistant spore containing a polar tube which s erves as a unique vehicle of infection. Polar tube proteins (PTPs) from Enc ephalitozoon hellem, Encephalitozoon (Septata) intestinalis, and Encephalit ozoon cuniculi were purified to homogeneity by HPLC. By SDS-PAGE, the Mr of E. hellem PTP was 55 kDa, while the Mr of E. intestinalis and E. cuniculi PTP was 45 kDa. Polyclonal rabbit antiserum to these purified PTPs localize d to polar filaments by immunogold electron microscopy and immunofluorescen ce, and demonstrated cross-reactivity by both immunoblotting and immunogold electron microscopy. These PTPs have similar solubility properties, hydrop hobicity, and proline content to a 43-kDa PTP we have previously purified f rom Glugea americanus, a fish microsporidium. As the polar tube is critical in the transmission of this organism: further study of PTPs may lead to th e development of new therapeutic strategies and diagnostic tests.