Search

Previously, we have identified a gene encoding thrombospondin-related anonymous protein of Babesia gibsoni (BgTRAP), and have shown that the antisera raised against recombinant BgTRAP expressed in Escherichia coli inhibited the growth of parasites. In the present study, a recombinant vaccinia virus expressing the BgTRAP (VV/BgTRAP) was constructed. A specific band with a molecular mass of 80 kDa, which is similar to that of native BgTRAP on the merozoites of B. gibsoni, was detected in the supernatant of VV/ BgTRAP-infected RK13 cells. Mice inoculated with VV/BgTRAP produced a specific antiBgTRAP response. The antiserum against VV/BgTRAP showed reactivity against the native BgTRAP on parasites. These results indicated that the recombinant vaccinia virus expressing BgTRAP might be a vaccine candidate against canine B. gibsoni infection.

Lyme borreliosis is a vector-borne disease transmitted through the bite of ticks infected by Borrelia burgdorferi sensu lato group, including B. burgdorferi sensu stricto, B. afzelii, and B. garinii. The goal of the present study was to detect Borrelia species in ticks infesting wild Korean water deer (KWD; Hydropotes inermis Swinhoe), using molecular and genotypic analyses. In total, 48 ticks were collected from KWD, all of which were morphologically identified as Haemaphysalis longicornis Neumann that is dominant in Korea. Nested PCR was performed to detect the Borrelia-specific 5S (rrf)-23S (rrl) intergenic spacer region and the outer surface protein A (ospA) genes in ticks. Both rrf-rrl and ospA were amplified from one of the 48 ticks (2.1%) and were identified as B. afzelii. To our knowledge, this study constitutes the first molecular detection of B. afzelii in Haemaphysalis ticks in Korea. Because B. afzelii is a zoonotic tick-borne pathogen, understanding the molecular characteristics of this bacterium is important for preventing the transmission of Borrelia from ticks to other animals and humans., (© The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The 5' UTR is widely involved in gene expression via post-transcriptional regulation. However, a detailed profile of the 5' UTR for Toxoplasma gondii has not yet been demonstrated. To investigate the issue, we compared the predicted open reading frames (ORFs) and transcription start sites (TSSs) of T. gondii obtained by TSS-seq, a method that enables analysis of encyclopedic TSSs with next-generation sequencers. As a result, it was demonstrated that the mode length of the 5' UTR is between 120 and 140 nucleotides (nts) when a subset of genes with predicted signal peptides was examined. However, when genes without the signal peptide were examined, the length was extended to approximately 600 nts. Because additional information on the predicted signal peptide generates increased reliability to the 5' end estimation of each ORF, we believe that the former value was more reliable as a representative of the 5' UTR length of T. gondii. The discrepancy suggests that current predictions of the 5' end of the ORF were less accurate and considerably more discordant with the natural status. The 5' untranslated region (5' UTR) is defined as that between the 5' end of the transcripts and just in front of a start codon of an ORF. Therefore, the 5' UTR does not contain any information for a protein sequence; however, it is involved in the control of protein expression via the modulation of translational efficiency (Kozak, 1991b; Hughes, 2006).

Three cDNAs encoding rhoptry-associated protein 1 (RAP-1) homologues were found in the Babesia gibsoni EST database. Based on similarities to BgRAP-1a, which was identified previously by serological screening of a cDNA merozoite library, the two new genes were designated BgRAP-1b (33.7%) and BgRAP-1c (57%). Mice antiserum raised against each recombinant protein reacted specifically with B. gibsoni parasites as determined by Western blotting, which showed native molecular sizes of the BgRAP-1a (51 kDa), BgRAP-1b (53 kDa) and BgRAP-1c (47 kDa) consistent with predictable molecular weights. Immunofluoresence using these antibodies revealed localization of all BgRAP-1s within the matrix of merozoites; however, BgRAP-1a appeared to diverge from the other two when it was found secreted into the cytoplasm of infected erythrocytes. Apical localization of all 3 BgRAP-1s during the extracellular stage of the parasite combined with their ability to bind a canine erythrocyte membrane fraction was suggestive of a role for these proteins in erythrocyte attachment. Lastly, the ability of these recombinant proteins to be used as diagnostic reagents was tested by ELISA and the sensitivities of BgRAP-1a and BgRAP-1c were found increased through N-terminal truncation. Taken together, our data suggest divergent roles for the 3 BgRAP-1s in the merozoite stage of B. gibsoni.

Peptidases of parasitic protozoa are currently under intense investigation in order to identify novel virulence factors, drug targets, and vaccine candidates, except in Babesia. Leucine aminopeptidases in protozoa, such as Plasmodium and Leishmania, have been identified to be involved in free amino acid regulation. We report here the molecular and enzymatic characterization, as well as the localization of a leucine aminopeptidase, a member of the M17 cytosolic aminopeptidase family, from B. gibsoni (BgLAP). A functional recombinant BgLAP (rBgLAP) expressed in Escherichia coli efficiently hydrolysed synthetic substrates for aminopeptidase, a leucine substrate. Enzyme activity of the rBgLAP was found to be optimum at pH 8.0 and at 37 degrees C. The substrate profile was slightly different from its homologue in P. falciprum. The activity was also strongly dependent on metal divalent cations, and was inhibited by bestatin, which is a specific inhibitor for metalloprotease. These results indicated that BgLAP played an important role in free amino acid regulation.

Serological immunoscreening was used to identify a gene encoding heat shock protein-70 from Babesia gibsoni (BgHSP-70) that showed high homology with HSP-70s from other apicomplexan parasites. This gene corresponded to a full-length cDNA containing an open reading frame of 1968 bp predicted to result in a 70-kDa mature protein consisting of 656 amino acids. Analysis of the expression levels of BgHSP-70 indicated elevated transcription from cultured parasites incubated at 40 degrees C for 1 h, but not at 30 degrees C. Interestingly, antiserum raised against recombinant BgHSP-70 protein reacted specifically not only with a 70-kDa protein of B. gibsoni but also with a corresponding native protein of B. microti (BmHSP-70), indicating the high degree of conservation of this protein. The BmHSP-70 gene was then isolated and characterized and the immunoprotective properties of recombinant BgHSP-70 (rBgHSP-70) and rBmHSP-70 were compared in vitro and in vivo. Both proteins had potent mitogenic effects on murine and canine mononuclear cells as evidenced by high proliferative responses and IFN-gamma production after stimulation. Immunization regimes in BALB/c and C57BL/6 mice using rBgHSP-70 and rBmHSP-70 elicited high antibody levels, with concurrent significant reductions in peripheral parasitaemias. Taken together, these results emphasize the potential of HSP-70s as a molecular adjuvant vaccine.

We have studied the impact of complement component 3 (C3) deficiency on the progression of lethal Babesia rodhaini infection in immune mice. A B. gibsoni ribosomal phosphoprotein P0 (BgP0) previously reported to be a cross-protective antigen against Babesia infection was used to immunize C57BL/6 wild-type (WT) and C3-deficient (C3-/-) mice. Test mice were immunized intraperitoneally (i.p.) with recombinant BgP0 (rBgP0), while controls either were immunized with PBS or did not receive any immunization. Following the immunization regime, test WT mice induced a specifically strong humoral response consisting of mixed immunoglobulins IgG1 and IgG2 associated with high production of IFN-gamma in the supernatant of splenocytes. While test C3-/- mice had significantly decreased total IgG, IgG1 and IgG2b responses, the secretions of IL-12 and IFN-gamma tended to be lower than those in WT mice. Furthermore, partial protection was only observed in rBgP0-immunized WT mice but not in C3-/- mice or controls. Indeed, rBgP0-immunized WT mice showed significant reductions in the initiation of parasitaemia correlated with delayed mortalities and considerable survival rates. Taken together, our results indicate that cross-protection was impaired in C3-/- mice in view of the decrease in the antibody responses and cytokine production and the high susceptibility to infection.