Characterization of Babesia bigemina perforin-like protein family

PETRIGH R,; REGO N; VALENTINI B; SORIA M; MOSQUEDA J; NAYA H; ECHAIDE I; FARBER M

Zaragoza

Conferencia; http://www.higieneambiental.com/sites/default/files/images/pdf/Program-ttp7.pdf; 2011

TTP7: Ticks and Tick-borne pathogens International Conference

Bovine babesiosis, cause by Babesia bigemina and Babesia bovis,  is a critical drawback to livestock production in tropical and subtropical developing regions worldwide.  In South America, both intraerythrocytic protozoa are transmitted by Rhipicephalusmicroplus.  Host-cell invasion mechanisms are fundamental to spread infection in bovine host and tick vector.  In spite of the relevance of host-cell invasion pathways for the spread of infection, little is known about these mechanisms in Babesia genera.A Previous studies have reported a family of five paralogous genes in the genome of Plasmodium spp., encoding secreted proteins containing membrane-attack complex/perforin (MACPF)-like domain. The perforin-like 1 protein (PLP1) of P. falciparum and Toxoplasma gondii are localized into micronemas of sporozoites, organelles involved in host-cell infection. Based on data from the annotated genomes of other apicomplexans(Plasmodium falciparum, Theileria annulata, Theileria parva and Babesia bovis), we used bioinformatic  tools to identify, annotate and characterize eight genes containing MACPF domain in B. bigemina from the available sequences of the B. bigemina genome. Transcriptional studies using RT-PCR showed that all plp genes are transcribed in the intraerythrocytic stage. However, the transcriptional level analysed by qPCR revealed that plpe and plpb genes have significantly higher transcriptional rates, which might suggest that  specific PLP proteins are required to reach  its function in the parasite egress from erythrocyte. On the other hand, the plpa gene sequence analysis showed the presence of a secretion signal and a polymorphic repetitive region among different  B. bigemina isolates. To explore whether this region might represent an adaptation to immune selection pressure, we produced a recombinant PLPA (rPLPA) to test it against bovine sera. The prediction of the signal  peptide together with the specific reaction of  bovine sera against rPLPA might suggest that PLPA is being exported to the erythrocyte membrane. Besides, we demonstrated PLPA expression in intraerythrocytic stage by an indirect immunofluorescence assays using specific mice sera obtained against rPLPA. Further studies should be performed to demonstrate  PLPA role in parasite exit mechanism from erythrocyte.