Polar Tube Proteins of Microsporidia of the Family Encephalitozoonidae

Abstract

Encephalitozoonidae are microsporidia associated with human infections including hepatitis, encephalitis, conjunctivitis, and disseminated disease. Microsporidia produce a small resistant spore containing a polar tube which serves as a unique vehicle of infection. Polar tube proteins (PTPs) from Encephalitozoon hellem. Encephalitozoon (Septata) intestinalis, and Encephalitozoon 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 localized to polar filaments by immunogold electron microscopy and immunofluorescence, and demonstrated cross-reactivity by both immunoblotting and immunogold electron microscopy. These PTPs have similar solubility properties, hydrophobicity, and proline content to a 43-kDa PTP we have previously purified from Glugea americanus, a fish microsporidium. As the polar tube is critical in the transmission of this organism, further study of PTPs may lead to the development of new therapeutic strategies and diagnostic tests.

The microsporidian polar tube: A highly specialised invasion organelle

“…They are ubiquitous in the animal kingdom with over a 1000 species parasitising a wide range of invertebrate and vertebrate hosts, including humans (Wittner and Weiss, 1999). While it had been suggested that the Microsporidia are primitive eukaryotes lacking mitochondria, recent data suggests they are related to the Fungi Keeling, 2003;Thomarat et al, 2004), have homologues for mitochondrial hsp70 (Hirt et al, 1997;Arisue et al, 2002) and a mitochondrial relic organelle (the mitosome) (Williams et al, 2002).…”

“…Reported prevalence rates in the 25 studies conducted on patients with HIV infection before the widespread use of highly active antiretroviral therapy demonstrated rates that varied between 2 and 70% depending on the symptoms of the population studied and the diagnostic technique employed (Weber and Bryan, 1994;Drobniewski et al, 1995;van Gool et al, 1995;Weitz et al, 1995;Coyle et al, 1996;Deplazes et al, 2000). In immunocompromised patients, Encephalitozoon has been associated with hepatitis, peritonitis, keratoconjunctivitis, sinusitis and disseminated infections involving the lungs and/or kidneys (Zender et al, 1989;Moss et al, 1997;Weber et al, 1997Weber et al, , 1999Wittner and Weiss, 1999;Franzen and Muller, 2001). Three cases of Pleistophora-like microsporidian infection involving skeletal muscles and myositis have been described in two HIV-infected patients and in a non-HIV-infected patient (Chupp et al, 1993;Cali and Takvorian, 2003).…”

“…The first suggestion that microsporidia are associated with human infections was made in 1924, and up to 1985, there were less than a dozen reports of human microsporidiosis (Wittner and Weiss, 1999). Since 1985 with the recognition that Enterocytozoon bieneusi causes diarrhoea in patients with AIDS (Desportes et al, 1985), many infections with different species of microsporidia have been reported from all over the world and microsporidia are now frequently recognised as etiologic agents of opportunistic infections in persons with AIDS, and more recently, in organ transplant recipients, patients being treated with immunosuppressive drugs and immunocompetent patients (Weber and Bryan, 1994;Sax et al, 1995;Wanke et al, 1996;Bryan et al, 1997;Raynaud et al, 1998;Gumbo et al, 1999;Wittner and Weiss, 1999;Metge et al, 2000;Lores et al, 2002;Lewis et al, 2003).…”

“…While it had been suggested that the Microsporidia are primitive eukaryotes lacking mitochondria, recent data suggests they are related to the Fungi Keeling, 2003;Thomarat et al, 2004), have homologues for mitochondrial hsp70 (Hirt et al, 1997;Arisue et al, 2002) and a mitochondrial relic organelle (the mitosome) (Williams et al, 2002). Encephalitozoon species have very small genomes (2.9, 2.6, and 2.3 Mb in Encephalitozoon cuniculi, Encephalitozoon hellem and Encephalitozoon intestinalis, respectively) (Biderre et al, 1999;Wittner and Weiss, 1999). With the completion of the E. cuniculi genome, the phylogenetic relationship between microsporidia and fungi has been further solidified by the presence of numerous genes that on phylogenetic analysis cluster the Microsporidia with the Fungi (Katinka et al, 2001;Thomarat et al, 2004).…”

“…Microsporidium) have been described as pathogens in humans (Sprague et al, 1992;Wittner and Weiss, 1999;Franzen and Muller, 2001). Reported prevalence rates in the 25 studies conducted on patients with HIV infection before the widespread use of highly active antiretroviral therapy demonstrated rates that varied between 2 and 70% depending on the symptoms of the population studied and the diagnostic technique employed (Weber and Bryan, 1994;Drobniewski et al, 1995;van Gool et al, 1995;Weitz et al, 1995;Coyle et al, 1996;Deplazes et al, 2000).…”