Thrombospondin-related anonymous protein (TRAP) family expression by Babesia bovis life stages within the mammalian host and tick vector

Authors: MASTERSON, HALEY - Washington State University; Taus, Naomi; JOHNSON, WENDELL - Retired ARS Employee; Kappmeyer, Lowell; CAPELLI-PEIXOTO, JANAINA - Washington State University; HUSSEIN, HALA - Washington State University; Mousel, Michelle; HERNANDEZ-SILVA, DIEGO - Autonomous University Of Queretaro; LAUGHERY, JACOB - Washington State University; MOSQUEDA, JUAN - Autonomous University Of Queretaro; Ueti, Massaro

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2022
Publication Date: 11/12/2022
Citation: Masterson, H.E., Taus, N.S., Johnson, W.C., Kappmeyer, L.S., Capelli-Peixoto, J., Hussein, H.E., Mousel, M.R., Hernandez-Silva, D.J., Laughery, J.M., Mosqueda, J., Ueti, M.W. 2022. Thrombospondin-related anonymous protein (TRAP) family expression by Babesia bovis life stages within the mammalian host and tick vector. Microorganisms. 10(11). Article 2173. https://doi.org/10.3390/microorganisms10112173.
DOI: https://doi.org/10.3390/microorganisms10112173

Interpretive Summary: The tick-transmitted disease bovine babesiosis causes significant economic losses in many countries around the world. Current control methods for preventing the disease include modified live-attenuated vaccines. However, live vaccines have limited efficacy, and a more reliable alternative strategy is required. Studying proteins critical for various stages of the parasites' lifecycles can lead to identification of target antigens that can be used in vaccines. We used reverse transcriptase quantitative PCR and immunofluorescence assays to evaluate the expression of thrombospondin-related anonymous protein (TRAP) family transcripts and proteins, respectively, during Babesia bovis life stages in the mammalian and tick hosts. Differential expression of TRAPs was demonstrated thus indicating that TRAP proteins may be potential vaccine targets to prevent B. bovis infection and disease in the mammalian host or to block infection of the tick vector and, consequently, prevent the transmission of B. bovis by the tick vector.

Technical Abstract: The tick-transmitted disease bovine babesiosis causes significant economic losses in many countries around the world. Current control methods include modified live-attenuated vaccines that have limited efficacy. Recombinant proteins could provide effective, safe, and low-cost alternative vaccines. We compared the expression of the Babesia bovis thrombospondin-related anonymous protein (TRAP) family from parasites in bovine blood, in vitro induced sexual stages, and kinetes from tick hemolymph. Quantitative PCR showed that in blood and sexual stages, TRAP3 was highly transcribed as compared to the other TRAPs. In contrast, the TRAP1 gene was highly transcribed in kinetes as compared to the other TRAPs. Fixed immunofluorescence assays showed that TRAP2, 3, and 4 proteins were expressed by both blood and sexual stages. Conversely, TRAP1 protein, undetected on blood and induced sexual stages, was the only family member expressed by kinetes. Live IFA revealed that TRAP2, 3, and 4 proteins were expressed on the surface of both B. bovis blood and sexual stages. Modeling of B. bovis TRAP1 and TRAP4 tertiary structure demonstrated both proteins folded the metal-ion-dependent adhesion site (MIDAS) domain structure of Plasmodium TRAP. In conclusion, TRAP proteins may serve as potential vaccine targets to prevent infection of bovine and ticks with B. bovis essential for controlling the spread of bovine babesiosis.