Unraveling the Complexity of the Rhomboid Serine Protease 4 Family of Babesia bovis Using Bioinformatics and Experimental Studies

ALZAN, HEBA F.; ASURMENDI, SEBASTIÁN; ROLLS, PETER; FLORIN-CHRISTENSEN, MÓNICA; HUSSEIN, HALA E.; UETI, MASSARO; ARAUJO, FLABIO R.; SCHNITTGER, LEONHARD; GALLENTI, ROMINA; SUAREZ, CARLOS E.; BENITEZ, DANIEL; SIBEKO-MATJILA, KGOMOTSO

Pathogens

MDPI

Año: 2022 vol. 11

Abstract: Babesia bovis, a tick-transmitted apicomplexan protozoon, infects cattle in tropical andsubtropical regions around the world. In the apicomplexans Toxoplasma gondii and Plasmodiumfalciparum, rhomboid serine protease 4 (ROM4) fulfills an essential role in host cell invasion. We thusinvestigated B. bovis ROM4 coding genes; their genomic organization; their expression in in vitrocultured asexual (AS) and sexual stages (SS); and strain polymorphisms. B. bovis contains five rom4paralogous genes in chromosome 2, which we have named rom4.1, 4.2, 4.3, 4.4 and 4.5. There aremoderate degrees of sequence identity between them, except for rom4.3 and 4.4, which are almostidentical. RT-qPCR analysis showed that rom4.1 and rom4.3/4.4, respectively, display 18-fold and218-fold significantly higher (p < 0.01) levels of transcription in SS than in AS, suggesting a role ingametogenesis-related processes. In contrast, transcription of rom4.4 and 4.5 differed non-significantlybetween the stages. ROM4 polymorphisms among geographic isolates were essentially restricted tothe number of tandem repeats of a 29-amino acid sequence in ROM4.5. This sequence repeat is highlyconserved and predicted as antigenic. B. bovis ROMs likely participate in relevant host?pathogeninteractions and are possibly useful targets for the development of new control strategies againstthis pathogen.