Characterization of Histomonas meleagridis antigens

Histomonas meleagridis is a protozoan parasite of many galliform birds. It causes a type of enterohepatitis termed "blackhead" disease or histomoniasis. Histomoniasis is characterized by diarrhea and typhlo-hepatitis in infected birds, and in turkeys by presence of tan-yellow "sulfur" dropping as an early clinical indication. Due to the ban of substances for prophylaxis or therapeutic treatment, histomoniasis is nowadays a re-emerging disease in poultry. It predominantly affects turkeys, causing high mortality, whereas in chickens clinical signs may vary considerably. However, increasing numbers of reports strengthen the importance of this flagellate especially in free-range production systems. Most of the work published on H. meleagridis characterizes its phylogenetic position, while detailed molecular biology studies, like studies on proteins that cause immune response of the host, are still missing. The present study aims at identifying and characterizing H. meleagridis antigens capable of eliciting the immune response of the host. To identify these antigens we plan to use a phage display method for which we will employ a H. meleagridids cDNA-expression library constructed in Lambda ZAP Express vector (Stratagene). We intent to screen the library with sera from infected poultry, namely chickens. In addition, we will also use polyclonal antibodies already raised in rabbits against highly purified in vitro propagated H. meleagridis trophozoites. The positive clones isolated during screening procedures will be characterized by performing extensive database searches to compare nucleotide and deduced amino acid sequences with known genes of other protozoa. The most interesting candidates, the ones with significant homologies to already described domains or proteins in other microorganisms, will be further characterized with respect to genomic locus organization, start of transcription, size and number of transcripts and cellular localization.

Histomonas meleagridis is a protozoan parasite of many galliform birds. It causes a type of enterohepatitis termed "blackhead" disease or histomoniasis. Histomoniasis is characterized by diarrhea and typhlo-hepatitis in infected birds, and in turkeys by presence of tan-yellow "sulfur" dropping as an early clinical indication. Due to the ban of substances for prophylaxis or therapeutic treatment, histomoniasis is nowadays a re-emerging disease in poultry. It predominantly affects turkeys, causing high mortality, whereas in chickens clinical signs may vary considerably. However, increasing numbers of reports strengthen the importance of this flagellate especially in free-range production systems. Most of the work published on H. meleagridis characterizes its phylogenetic position, while detailed molecular biology studies, like studies on proteins that cause immune response of the host, are still missing. The present study aims at identifying and characterizing H. meleagridis antigens capable of eliciting the immune response of the host. To identify these antigens we plan to use a phage display method for which we will employ a H. meleagridids cDNA-expression library constructed in Lambda ZAP Express vector (Stratagene). We intent to screen the library with sera from infected poultry, namely chickens. In addition, we will also use polyclonal antibodies already raised in rabbits against highly purified in vitro propagated H. meleagridis trophozoites. The positive clones isolated during screening procedures will be characterized by performing extensive database searches to compare nucleotide and deduced amino acid sequences with known genes of other protozoa. The most interesting candidates, the ones with significant homologies to already described domains or proteins in other microorganisms, will be further characterized with respect to genomic locus organization, start of transcription, size and number of transcripts and cellular localization.