Characterization of Babesia bigemina perforin-like protein family

ROMINA PETRIGH; NATALIA REGO; BEATRIZ VALENTINI; MARCELO SORIA; JUAN MOSQUEDA; HUGO NAYA; IGNACIO ECHAIDE; MARISA FARBER

Zaragoza

Conferencia; VII Internacional Conference on Ticks and Ticks- borne pathogens.; 2011

  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 Rhipicephalus microplus. Host-cell invasion processes are fundamental to spread infection in bovine host and tick vector.  However, little is known regarding invasion mechanisms in Babesia genera. A previous study have reported a family of five paralogous genes in the genome of Plasmodium spp., encoding secreted proteins with membrane-attack complex/perforin (MACPF)-like domain. Both in P. falciparum and Toxoplasma gondii, perforin-like 1 protein (PLP1) is 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 determined by qPCR revealed that plpe and plpb genes have significantly higher transcriptional rates, which suggested that specific PLP proteins might be involved in 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 B. bigemina isolates. To explore whether this region might represent an adaptation to immune selection pressure, we produced recombinant PLPA (rPLPA) for testing against bovine sera. The presence of a signal peptide together with the specific recognition of rPLPA by positive Babesia bovine sera, might suggest that PLPA is being exported to the erythrocyte membrane. Besides, we demonstrated intraerythrocytic stage PLPA expression by indirect immunofluorescence assay, using specific mice sera obtained against rPLPA. Further studies should be undertaken to demonstrate PLPA role in  erythrocyte exit mechanism.