Bumped kinase inhibitor 1369 is effective against Cystoisospora suis in vivo and in vitro.

Cystoisosporosis is a leading diarrheal disease in suckling piglets. With the confirmation of resistance against the only available drug toltrazuril, there is a substantial need for novel therapeutics to combat the infection and its negative effects on animal health. In closely related apicomplexan species, bumped kinase inhibitors (BKIs) targeting calcium-dependent protein kinase 1 (CDPK1) were shown to be effective in inhibiting host-cell invasion and parasite growth. Therefore, the gene coding for Cystoisospora suis CDPK1 (CsCDPK1) was identified and cloned to investigate activity and thermal stabilization of the recombinant CsCDPK1 enzyme by BKI 1369. In this comprehensive study, the efficacy, safety and pharmacokinetics of BKI 1369 in piglets experimentally infected with Cystoisospora suis (toltrazuril-sensitive, Wien-I and toltrazuril-resistant, Holland-I strains) were determined in vivo and in vitro using an established animal infection model and cell culture, respectively. BKI 1369 inhibited merozoite proliferation in intestinal porcine epithelial cells-1 (IPEC-1) by at least 50% at a concentration of 40 nM, and proliferation was almost completely inhibited (>95%) at 200 nM. Nonetheless, exposure of infected cultures to 200 nM BKI 1369 for five days did not induce structural alterations in surviving merozoites as confirmed by transmission electron microscopy. Five-day treatment with BKI 1369 (10 mg/kg BW twice a day) effectively suppressed oocyst excretion and diarrhea and improved body weight gains in treated piglets without obvious side effects for both toltrazuril-sensitive, Wien-I and resistant, Holland-I C. suis strains. The plasma concentration of BKI 1369 in piglets increased to 11.7 µM during treatment, suggesting constant drug accumulation and exposure of parasites to the drug. Therefore, oral applications of BKI 1369 could potentially be a therapeutic alternative against porcine cystoisosporosis. For use in pigs, future studies on BKI 1369 should be directed towards ease of drug handling and minimizing treatment frequencies.

Selected metabolic biochemical and enzyme activities associated with Besnoitia besnoiti infection in dairy cattle.

The main aim of the study was to explore, compare, and identify whether there is an association between Besnoitia besnoiti seropositivity in apparently healthy dairy cows with some biochemical parameters, enzyme activities, and beta-hydroxybutyrate (BHBA). A total of 98 dairy cows were included in the study, of which there was 50 seropositive and 48 seronegative cows. Analysis of serum antibodies against B. besnoiti antibodies was performed using an indirect enzyme-linked immunosorbent assay kit. Student's independent t test showed that there was a significant difference in BHBA, albumin, and lactate dehydrogenase (LDH) between the seropositive and seronegative groups. Univariable regression analysis showed no significant association between seropositivity status with any of the evaluated parameters except BHBA level, mastitis, and abomasum displacement. Multivariable logistic regression analysis showed that there was a strong association between seropositivity with BHBA level. The significant association between BHBA and B. besnoiti seropositivity represents preliminary finding that needs further exploration.

Characterisation of full-length mitochondrial copies and partial nuclear copies (numts) of the cytochrome b and cytochrome c oxidase subunit I genes of Toxoplasma gondii, Neospora caninum, Hammondia heydorni and Hammondia triffittae (Apicomplexa: Sarcocystidae).

Genomic DNA was extracted from three oocyst isolates of Hammondia triffittae from foxes and two oocyst isolates of Hammondia heydorni from dogs, as well as from cell culture-derived tachyzoites of Toxoplasma gondii (RH strain) and Neospora caninum (NC-Liverpool strain), and examined by PCR with primers targeting the cytochrome b (cytb) and the cytochrome c oxidase subunit I (cox1) genes in order to characterise both genes and, if possible, the remainder of the mitochondrial genome of these species. Several primers were designed and used in various combinations to amplify regions within and between both genes and to determine gene order. When certain forward primers targeting cytb were used in combination with certain reverse primers targeting cox1, two overlapping sequences were obtained for each species and isolate studied, which showed that a full-length copy of cytb was followed 36-37 bp downstream by a full-length copy of cox1, and these sequences are believed to represent the true mitochondrial genes and the gene order in the mitochondrial genome of the four species examined. The cytb of T. gondii, N. caninum, H. heydorni and H. triffittae comprised a total of 1,080 bp (359 amino acids) and used ATG and TAA as start and stop codon, respectively. The cox1 of these species also used TAA as stop codon, whereas the most likely start codon was ATG, resulting in a gene comprising 1,491 bp (496 amino acids). Pair-wise sequence comparisons based on either cytb or cox1 clearly separated T. gondii from N. caninum and both of these species from the two Hammondia species, whereas the latter two species were 100 % identical at cytb and shared 99.3 % identity at cox1. Phylogenetic analyses using the maximum-likelihood method confirmed these findings and placed T. gondii in a clade separate from the three other species and all four Toxoplasmatinae in a sister clade to Eimeria spp. PCR with other primers and/or primer pairs than those used to obtain the full-length mitochondrial genes yielded several types of about 1-1.5 kb long sequences, which comprised stretches of the primer-targeted genes at both ends and an intervening non-coding sequence of various length and composition. Thus, portions of cytb could be found both upstream and downstream from portions of cox1 and portions of the same gene could be found adjacent to each other (cytb→cox1; cox1→cytb; cytb→cytb; cox1→cox1). Sequence comparisons revealed that some of these gene fragments were truncated genes, whereas others included the putative start or stop codon of the full-length mitochondrial genes. From the nature of the gene fragments and/or their flanking sequences, they are assumed to be located on the chromosomes of the nuclear genome and to represent nuclear mitochondrial DNA segments (numts) or pseudogenes. In the four species examined, there were no nucleotide differences between the full-length mitochondrial copies of cytb and cox1 and their various incomplete nuclear counterparts. With a few exceptions, identical numt types and closely similar flanking sequences were obtained for all four species, which would indicate that the original transfer of these mitochondrial genes to the nuclear genome and/or the majority of any subsequent rearrangements of these gene fragments within the nuclear genome happened before the four species diverged. Yet, there were species-specific differences in the nucleotide composition of the nuclear gene fragments, identical to the differences in the mitochondrial genes, which would indicate that the incomplete nuclear copies of cytb and cox1 have been continuously updated during evolution to conform to their mitochondrial parent genes. The PCR-based findings of numts were further supported by Basic Local Alignment Search Tool (BLAST) searches against genome sequences of T. gondii and N. caninum using the concatenated mitochondrial cytb/cox1 sequences as queries. These searches revealed the presence of numerous numts of eighth distinct types in both species, with each one having a fixed starting and end point with respect to the nucleotide positions in the full-length mitochondrial genes. Four numt types were completely homologous between both species, whereas four other types differed with respect to their end point and/or the absence/presence of a 96-bp deletion. Each starting and end point was associated with a unique 100-200-bp long flanking sequence, which further revealed the presence of numts. For both species, the numt types and their various arrangements with respect to each other were identical or similar to those obtained by PCR in all four species examined. None of the identified numts covered a full-length gene, but together, the various numts covered the entire mitochondrial cytb and cox1 genes in an overlapping manner. In addition, they were fairly closely spaced on the chromosomes, and these features may explain why the nuclear copies were preferentially amplified to the exclusion of the true mitochondrial genes with most primers and primer pairs used in the present study. The possibility of a similar high prevalence of numts occurring in the nuclear genome of dinoflagellates is discussed.

Besnoitia besnoiti protein disulfide isomerase (BbPDI): molecular characterization, expression and in silico modelling.

Besnoitia besnoiti is an apicomplexan parasite responsible for bovine besnoitiosis, a disease with a high prevalence in tropical and subtropical regions and re-emerging in Europe. Despite the great economical losses associated with besnoitiosis, this disease has been underestimated and poorly studied, and neither an effective therapy nor an efficacious vaccine is available. Protein disulfide isomerase (PDI) is an essential enzyme for the acquisition of the correct three-dimensional structure of proteins. Current evidence suggests that in Neosporacaninum and Toxoplasmagondii, which are closely related to B. besnoiti, PDI play an important role in host cell invasion, is a relevant target for the host immune response, and represents a promising drug target and/or vaccine candidate. In this work, we present the nucleotide sequence of the B. besnoiti PDI gene. BbPDI belongs to the thioredoxin-like superfamily (cluster 00388) and is included in the PDI_a family (cluster defined cd02961) and the PDI_a_PDI_a'_c subfamily (cd02995). A 3D theoretical model was built by comparative homology using Swiss-Model server, using as a template the crystallographic deduced model of Tapasin-ERp57 (PDB code 3F8U chain C). Analysis of the phylogenetic tree for PDI within the phylum apicomplexa reinforces the close relationship among B. besnoiti, N. caninum and T. gondii. When subjected to a PDI-assay based on the polymerisation of reduced insulin, recombinant BbPDI expressed in E. coli exhibited enzymatic activity, which was inhibited by bacitracin. Antiserum directed against recombinant BbPDI reacted with PDI in Western blots and by immunofluorescence with B. besnoiti tachyzoites and bradyzoites.