Differential paired stage-specific expression of Babesia bovis cysteine-rich GCC2/GCC3 domain family proteins (BboGDP) during development within Rhipicephalus microplus

Authors: HUSSEIN, HALA - Washington State University; JOHNSON, WENDELL - Retired ARS Employee; Ueti, Massaro

Submitted to: Parasites & Vectors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/19/2022
Publication Date: 1/17/2023
Citation: Hussein, H.E., Johnson, W.C., Ueti, M.W. 2023. Differential paired stage-specific expression of Babesia bovis cysteine-rich GCC2/GCC3 domain family proteins (BboGDP) during development within Rhipicephalus microplus. Parasites & Vectors. 16. Article 16. https://doi.org/10.1186/s13071-022-05628-6.
DOI: https://doi.org/10.1186/s13071-022-05628-6

Interpretive Summary: Babesia bovis is a parasite that causes bovine babesiosis. This parasite is transmitted by Rhipicephalus ticks. Babesia parasites need to infect both cattle and ticks to complete its lifecycle. The development of a transmission blocking vaccine to control bovine babesiosis requires the identification of molecules expressed by the parasite during its development within tick vectors. In this study we investigated two proteins, BboGDP1 and 3, to determine if they were expressed by parasites during tick infection. The results revealed expression of BboGDP1 and 3 during parasite development within the tick vector. Antibodies confirmed expression of BboGDP1 and 3 by in vitro induced sexual stages and kinetes. Data collected in this study indicate that BboGDP1 and 3 are potential candidates for the development of a transmission blocking vaccine to prevent the spread of parasites via tick vectors.

Technical Abstract: Background: Babesia bovis, an intra-erythrocytic apicomplexan parasite, is one of the causative agents of bovine babesiosis, the most important tick-borne disease of cattle in tropical and subtropical regions. Babesia bovis has a complex lifecycle, including sexual development within the tick vector. The development of a transmission blocking vaccine to control bovine babesiosis requires the identification of antigens displayed on the surface of parasite during its development within tick vectors. Four B. bovis cysteine rich GCC2/GCC3 domain protein (BboGDP) family members were previously identified and are differentially expressed as discrete pairs by either blood stages or kinetes. In this study we focused on two family members, BboGDP1 and 3, that are expressed by Babesia parasites during tick infection. Results: Hereby, transcription analysis using qPCR demonstrated that BboGDP1 and 3 were upregulated in in vitro induced sexual stage parasites and during parasite development in the tick midgut. Moreover, protein expression analysis of BboGDP1 and 3 during development of sexual stages in in vitro culture was consistent with their transcription profile. Live immunofluorescence analysis using polyclonal antibodies confirmed surface expression of BboGDP1 and 3 on in vitro induced sexual stage parasites. In addition, fixed immunofluorescence analysis showed reactivity of anti-BboGDP1 and 3 polyclonal antibodies to kinetes. Conclusions: The collective data indicate that BboGDP1 and 3 are expressed by kinetes and on the surface of sexual stages. The identified parasite surface membrane proteins BboGDP1 and 3 are potential candidates for the development of a B. bovis transmission blocking vaccine.