Identification of CCp5 and FNPA as novel non-canonical members of the CCp protein family in Babesia bovis

Authors: OZUBEK, SEZAYI - Washington State University; ALZAN, HEBA - Washington State University; BASTOS, REGINALDO - Washington State University; LAUGHERY, JACOB - Washington State University; Suarez, Carlos

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2022
Publication Date: 2/15/2022
Citation: Ozubek, S., Alzan, H.F., Bastos, R.G., Laughery, J.M., Suarez, C.E. 2022. Identification of CCp5 and FNPA as novel non-canonical members of the CCp protein family in Babesia bovis. Frontiers in Veterinary Science. 9. Article 833183. https://doi.org/10.3389/fvets.2022.833183.
DOI: https://doi.org/10.3389/fvets.2022.833183

Interpretive Summary: Bovine babesiosis caused by Babesia bovis 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. In this study we identified two genes (termed CCp5 and FNPA) encoding for proteins that can are non canonical members of the CCp family of proteins, which are known to involved in the development of sexual reproduction of Babesia-related apicomplexan parasites. Sexual reproduction in Babesia parasites occurs in the midgut of their tick vectors, and is an event required for efficient transmission of the parasite in nature. Some of the members of this family are expressed in the surface of Babesia gametocytes and can be the targets for the development of transmission-blocking vaccines. The data provides inside on the biology of the parasite and supports FNPA as a possible candidate component of a transmission-blocking vaccine against B. bovis.

Technical Abstract: Bovine babesiosis caused by Babesia bovis 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 Babesia spp. and Plasmodium spp. While Plasmodium parasites contain 6 distinct CCp genes, only three members (CCp 1-3) were previously identified in B. bovis. In this study, we describe the identification and characterization of two novel non-canonical members of the CCp gene family in B. bovis, named CCp5 and FNPA. The genes were identified in silico by TBLASTN using P. falciparum CCp family domains as queries. Unlike CCp1-3, the B. bovis CCp5 and FNPA proteins lack the LCCL canonical domain but contain other typical multidomain adhesion motifs which are also present in canonical CCp proteins, and conserved synteny with known CCp genes in related apicomplexans. Sequence analysis of these two proteins demonstrated high sequence conservation among isolates. Also, transcription, immunoblot, and immunofluorescence analyses demonstrated expression of CCp5 and FNPA in blood and in vitro induced sexual stages of B. bovis. Also, FNPA, in contrast to CCp5, has a predicted transmembrane domain, suggesting that it might be expressed in the surface of sexual stage parasites. Altogether, the data supports FNPA as a possible candidate component of a transmission-blocking vaccine against B. bovis.