Identification of CCp5 and FNPA as Novel Non-canonical Members of the CCp Protein Family in .

Bovine babesiosis, caused by , is an economically significant tick-borne disease that imposes restrictions to livestock production worldwide. Current methods to control bovine babesiosis have severe limitations and novel approaches, including transmission-blocking vaccines, are needed. Members of the widely conserved CCp family are multidomain adhesion proteins containing LCCL motifs, which are differentially expressed on gametocytes of apicomplexans, including spp. and spp. While parasites contain 6 distinct genes, only three members (CCp 1-3) were previously identified in . In this study, we describe the identification and characterization of two novel non-canonical members of the gene family in , named CCp5 and FNPA. The genes were identified by TBLASTN using CCp family domains as queries. Unlike CCp1-3, the CCp5 and FNPA proteins lack the LCCL canonical domain but contain other typical multidomain adhesion motifs which are present in classical CCp proteins. In addition, the and are in synteny with known genes in related apicomplexans. Sequence analysis of these two proteins demonstrated high sequence conservation among different isolates. Transcription, immunoblot, and immunofluorescence analyses demonstrated expression of CCp5 and FNPA in blood and induced sexual stages of . The FNPA, in contrast to CCp5, has a predicted transmembrane domain, suggesting that it might be expressed in the surface of sexual stage parasites. Altogether, finding of this study support FNPA as a possible target of a transmission-blocking vaccine against .