LKR/SDH Plays Important Roles throughout the Tick Life Cycle Including a Long Starvation Period

BACKGROUND:Lysine-ketoglutarate reductase/saccharopine dehydrogenase (LKR/SDH) is a bifunctional enzyme catalyzing the first two steps of lysine catabolism in plants and mammals. However, to date, the properties of the lysine degradation pathway and biological functions of LKR/SDH have been very little described in arthropods such as ticks. METHODOLOGY/PRINCIPAL FINDINGS:We isolated and characterized the gene encoding lysine-ketoglutarate reductase (LKR, EC 1.5.1.8) and saccharopine dehydrogenase (SDH, EC 1.5.1.9) from a tick, Haemaphysalis longicornis, cDNA library that encodes a bifunctional polypeptide bearing domains similar to the plant and mammalian LKR/SDH enzymes. Expression of LKR/SDH was detected in all developmental stages, indicating an important role throughout the tick life cycle, including a long period of starvation after detachment from the host. The LKR/SDH mRNA transcripts were more abundant in unfed and starved ticks than in fed and engorged ticks, suggesting that tick LKR/SDH are important for the starved tick. Gene silencing of LKR/SDH by RNAi indicated that the tick LKR/SDH plays an integral role in the osmotic regulation of water balance and development of eggs in ovary of engorged females. CONCLUSIONS/SIGNIFICANCE:Transcription analysis and gene silencing of LKR/SDH indicated that tick LKR/SDH enzyme plays not only important roles in egg production, reproduction and development of the tick, but also in carbon, nitrogen and water balance, crucial physiological processes for the survival of ticks. This is the first report on the role of LKR/SDH in osmotic regulation in animals including vertebrate and arthropods

Babesial Vector Tick Defensin against Babesia sp. Parasites▿ †

Antimicrobial peptides are major components of host innate immunity, a well-conserved, evolutionarily ancient defensive mechanism. Infectious disease-bearing vector ticks are thought to possess specific defense molecules against the transmitted pathogens that have been acquired during their evolution. We found in the tick Haemaphysalis longicornis a novel parasiticidal peptide named longicin that may have evolved from a common ancestral peptide resembling spider and scorpion toxins. H. longicornis is the primary vector for Babesia sp. parasites in Japan. Longicin also displayed bactericidal and fungicidal properties that resemble those of defensin homologues from invertebrates and vertebrates. Longicin showed a remarkable ability to inhibit the proliferation of merozoites, an erythrocyte blood stage of equine Babesia equi, by killing the parasites. Longicin was localized at the surface of the Babesia sp. parasites, as demonstrated by confocal microscopic analysis. In an in vivo experiment, longicin induced significant reduction of parasitemia in animals infected with the zoonotic and murine B. microti. Moreover, RNA interference data demonstrated that endogenous longicin is able to directly kill the canine B. gibsoni, thus indicating that it may play a role in regulating the vectorial capacity in the vector tick H. longicornis. Theoretically, longicin may serve as a model for the development of chemotherapeutic compounds against tick-borne disease organisms

Detection and molecular characterization of rabies virus in Mongolia during 2008-2010

Aim: We aimed to investigate the prevalence and molecular characterization of rabies virus (RABV) from wild and domestic animals in Mongolia during 2008-2010. Materials and Methods: Brain tissue samples were collected from 24 rabid animals in Zavkhan, Omnogovi, Tov, Dundgovi, Govi-Altai, Selenge, Ovorkhangai, and Khentii provinces in Mongolia. Herein, samples were included from 13 domestic animals (dogs, cattle, camels, sheep, and goat) and 11 wild animals (wolves and foxes) in this study. Direct fluorescent antibody (DFA) test and reverse transcriptase polymerase chain reaction (RT-PCR) were performed for detection of RABV, and positive samples were further processed for molecular characterization of the virus using nucleoprotein gene. Subsequently, the molecular characterization was determined based on the nucleoprotein gene. Results: Out of 24 samples, 22 samples were detected positive for RABV by DFA test, and its nucleoprotein gene was amplified in all of the 24 samples by RT-PCR. These Mongolian RABVs were classified within steppe-type virus clade by phylogenetic analysis of nucleoprotein gene sequences. This steppe-type virus clade was clearly divided by two Sub-clades (A and B). The most of Mongolian RABVs belongs to the Sub-clade A in the phylogenetic tree. Conclusion: These findings have clearly confirmed RABV in domestic and wild animals of Mongolia. Further molecular characterization indicated that this Mongolian strain is steppe-type virus clade consisting of two sub-clades; the Subclade A might be prevalent in Altai, Khangai, Khentii Mountains as a major genotype, whereas the Subclade B seems to be cosmopolitan in the steppe-type virus clade, is spread in northern central Eurasia

Detection of equine Babesia spp. gene fragments in Dermacentor nuttalli olenev 1929 infesting Mongolian horses, and their amplification in egg and larval progenies

Babesia equi (EMA-1) and Babesia caballi (BC48) gene fragments were amplified by polymerase chain reaction (PCR), in blood samples, and partially fed-females and egg and larval progenies of Dermacentor nuttalli, collected from horses in Altanbulag, Tuv Province, Mongolia. While Babesia parasite DNA was detected in some horse blood samples during the first PCR, all positive cases in partially fed-female ticks, eggs and larvae were confirmed by nested PCR. Present study reinforces earlier similar findings in unfed D. nuttalli ticks collected from an open space vegetation in Bayanonjuul, Tuv Province in Central Mongolia, pointing to the most likely important role of D. nuttalli in the transmission of equine babesiosis in Mongolia. The detection of parasite DNA in eggs and larval progenies is likewise suggestive of transovarial parasite transmission in this tick species