Isao Kimata

Osaka City University, Ōsaka, Ōsaka, Japan

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Publications (75)92.01 Total impact

  • [Show abstract] [Hide abstract] ABSTRACT: Cryptosporidium andersoni is a protozoan parasite found in many countries that invades the stomachs of primarily adult cattle. Unlike the isolates of C. andersoni in cattle from other countries, C. andersoni isolates from Japanese cattle can infect mice and were identified as a novel type and later defined as C. andersoni Kawatabi type. The biological characteristics of C. andersoni Kawatabi type have not yet been well documented. In the present study, we assess the infectivity of this type isolate in mice with different immune competence status and age. We found that inoculation of more than 1×10(4) oocysts is needed to establish infection in mature mice irrespective of immune status. All of the infected immunocompetent mice recovered after a patent period of approximately 20days. In immunodeficient mice, the pre-patent period was prolonged compared with that of 1×10(6) oocysts, but the pattern and the maximum shedding measured by the number of oocysts per day were almost identical. In neonatal immunocompetent and immunodeficient mice, inoculation with 1×10(4) to 10(5) oocysts was also needed to establish infection. Our results indicate that there is a threshold of oocysts needed to establish patent infection in the acidic conditions of the stomach.
    No preview · Article · Nov 2012 · Parasitology International
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    [Show abstract] [Hide abstract] ABSTRACT: The aims of this study were to provide a cost-effective and valuable method for evaluating drug efficacy against Cryptosporidium parvum using a quantitative SYBR Green real-time PCR (qPCR) and to assess the efficacy of adenosine analogues as drug templates. C. parvum HNJ-1 strain growing in human ileocaecal adenocarcinoma cells was employed as an in vitro culture system. To normalize the DNA extraction efficiency, a specific plasmid was added to each sample before DNA purification; the genomic DNA of infected cells was quantified by qPCR using specific primers to confirm drug efficacy and cytotoxicity. To determine the mechanism of action, enzymatic inhibition analyses were conducted using C. parvum S-adenosyl-l-homocysteine hydrolase (CpSAHH) recombinant protein. The dose-dependent growth inhibition of C. parvum was confirmed; 50% effective concentrations of neplanocin A (NPA) and 2-fluoroadenosine (2FA) were 139 μM and 0.842 μM, respectively. Cytotoxicity evaluation showed that the 50% growth inhibition concentration of 2FA was 1.18 μM; NPA did not exhibit any cytotoxicity up to 200 μM. The screening system revealed the specific but marginal efficacy of NPA and showed 2FA to be cytotoxic. Recombinant CpSAHH inhibition analyses showed that NPA competitively inhibited CpSAHH activity (K(i )= 0.395 μM), whereas 2FA did not. This novel qPCR system confirmed not only drug efficacy against C. parvum but also cytotoxicity to host cells. Moreover, since the SYBR Green method is cost effective, it could therefore be used in a wide variety of clinical and research-oriented applications of Cryptosporidium analysis.
    Full-text · Article · Mar 2011 · Journal of Antimicrobial Chemotherapy
  • [Show abstract] [Hide abstract] ABSTRACT: A full-length cDNA library was constructed from the sporozoite of Cryptosporidium parvum. Normalized clones were subjected to Solexa shotgun sequencing, and then complete sequences for 1066 clones were reconfigured. Detailed analyses of the sequences revealed that 13.5% of the transcripts were spliced; the average and median 5' UTR lengths were 213.5 and 122 nucleotides, respectively. There were 148 inconsistencies out of 562 examined genes between the experimentally described cDNA sequence and the predicted sequence from its genome. In addition, we identified 118 sequences that had little homology against annotated genes of C. parvum as prospective candidates for addable genes. These observations should improve the reliability of C. parvum transcriptome and provide a versatile resource for further studies.
    No preview · Article · Mar 2011 · Parasitology International
  • [Show abstract] [Hide abstract] ABSTRACT: The genus Cryptosporidium includes many common parasites infecting animals and humans, and is a major cause of diarrheal illness worldwide. The biology of gastric Cryptosporidium spp., including replication in the stomach, has not been well documented. This study evaluated the viability of Cryptosporidium andersoni sporozoites in gastric environments after excystation and examined the endogenous development and histopathological changes in the stomachs of infected mice, using a novel type of C. andersoni. Sporozoites were affected by low pH (61.6% viability after 3h at pH2.0). Electron microscopy revealed developmental parasites on the gastric foveolae but not on the surface of the gastric mucosa. Histopathological examinations at 1, 2, 4 and 12 weeks p.i. uncovered three different lesions. The gastric mucosa of foveolae filled with parasites was extended and the amount of neutral mucopolysaccharide at the mucosal surface was decreased with the first type of lesion. The gastric mucosa was atrophied, some gastric glands were disrupted and the amount of acid mucopolysaccharide at the mucosal surface was increased with the second type. Finally, the gastric mucosa was slightly extended and goblet cells were present in the gastric mucosa, indicating intestinal metaplasia, in the third type. No parasites were detected in these areas with increased acidic mucin and indications of metaplasia. The results suggest that C. andersoni parasites could not survive in acidic environments for a long period before invading host cells and preferentially develop in neutral sites of the gastric mucosa, resulting in histopathological changes and chronic shedding of oocysts.
    No preview · Article · Nov 2010 · International journal for parasitology
  • M Matsubayashi · H Ando · I Kimata · H Nakagawa · M Furuya · H Tani · K Sasai
    [Show abstract] [Hide abstract] ABSTRACT: Cryptosporidium parvum, belonging to the phylum Apicomplexa, is a major cause of waterborne gastroenteritis throughout the world. The sporozoites are thought to invade host enterocytes using an active process termed gliding motility. However, the biological and morphological changes within the sporozoites during this process are not fully understood. In the present study, excysted sporozoites of C. parvum were analysed ultrastructurally in vitro and their viability was evaluated using fluorescent dyes. The sporozoites excysted from oocysts changed morphologically from banana-shaped to rod-shaped and finally to a rounded shape, in culture media in 3 h. Transmission microscopy revealed that the distance between the apical end and the nucleus was markedly reduced, dense granules were present close to the rhoptry in the apical region, amylopectin granules were absent, and membranes of round sporozoites were less clear. A fluorescent assay showed that the rate of survival decreased from 89% to 56% at 0-3 h (84.3% for banana-shaped and 49.2% for rod-shaped sporozoites). Therefore, post-excysted sporozoites in vitro underwent morphological changes and a rapid loss of viability. This staining method is useful, inexpensive and provides an alternative to more costly and intensive flow cytometric assays or infectivity assays with host cells in vitro.
    No preview · Article · Nov 2010 · Parasitology
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    [Show abstract] [Hide abstract] ABSTRACT: Cystoisospora spp. from feces in dogs, cats, and raccoon dogs were isolated, sequenced at the small subunit ribosomal RNA gene locus and compared to other Cystoisospora spp. Cystoisospora oocysts from dogs and raccoon dogs were morphologically similar with those of C. ohioensis, and cat isolates were similar with those of C. felis. The sequences from dogs and raccoon dogs, and cats have a homology with C. ohioensis and C. felis, respectively. Phylogenetic analysis of the DNA sequences showed that the dog and raccoon dog isolates were nested in a clade with other Cystoisospora spp. including C. ohioensis, C. belli, and C. orlovi. The cat isolate formed a sister group with C. felis that was a separate clade from the dog and raccoon dog group. We report sequence variation in these Cystoisospora sequences and have identified raccoon dogs as another carnivore host for Cystoisospora spp. infecting dogs.
    Full-text · Article · Nov 2010 · Veterinary Parasitology
  • [Show abstract] [Hide abstract] ABSTRACT: Compared with other countries, surveys of these parasites have been rarely performed in companion animals of Japan in spite of their significance for public health. Here, we investigated pet dogs and cats in Japan for the first time, and genetically analyzed the isolates to evaluate the risk of zoonotic infections. Seventy-seven fecal samples were collected from privately owned dogs and 55 samples from owned cats in Osaka city, Japan. Cryptosporidium oocysts were identified in 3/77 dogs (3.9%) and 7/55 cats (12.7%), and Giardia infection in 2/77 dogs (2.6%) and 1/55 cats (1.8%). Amplification of the target regions for genotyping was successful, Cryptosporidium isolates in dogs and cats were identified as C. canis and C. felis, respectively, and those of Giardia in dogs and cats were G. intestinalis Assemblages D and F. The discharge period of the oocysts varied within 3-16 weeks and that of the cysts was 12 weeks. To date, zoonotic types of both parasites have been identified in other animals in Japan, and further large-scale studies are needed to determine the distribution of zoonotic genotypes in these animals, especially those closely associated with humans.
    No preview · Article · Sep 2010 · Veterinary Parasitology
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    Niichiro Abe · Isao Kimata
    Preview · Article · Jul 2010
  • [Show abstract] [Hide abstract] ABSTRACT: Cryptosporidiosis is a diarrheal illness caused by apicomplexa parasite Cryptosporidium spp. In this study, to examine the overall infection status of Cryptosporidium spp. in individuals residing in southern parts of Korea, eight counties around Yeongsan, Seomjin and Nakdong River valleys was surveyed. The investigation was carried out from April to October 2005. A total of 9,498 stool samples were collected from individuals. Stool samples were analyzed for modified acid-fast stains, and DNA fragment extracted from positive samples was identified by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) for 18S rRNA polymorphic region. Oocysts of Cryptosporidium spp. were detected in 239 specimens (2.5%) by a modified acid-fast stain. Infection rate was not significantly different between male (2.2%) and female (2.8%) individuals examined (P>0.05). In the infection rate by age, totally 1-9 (4.8%) and 80< (3.7%) age group were shown to the highest, and there was shown to significant differences (P<0.05). Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of 18S rRNA gene from 51 isolates showed that all the isolates were identified as C. parvum. Our data collectively suggested that C. parvum infection is prevalent in the studied areas of Korea and more comprehensive nation-wide epidemiological studies are needed to elucidate the infection status of Cryptosporidium infection in Korea.
    No preview · Article · Nov 2009 · Journal of Veterinary Medical Science
  • Niichiro Abe · Isao Kimata
    [Show abstract] [Hide abstract] ABSTRACT: Enterocytozoon bieneusi is an emerging and clinically significant enteric human pathogen that is mainly associated with chronic diarrhea. It has been identified in a variety of wild, domestic, and companion mammals and birds. This pathogen is genetically diverse and is composed of over 80 host-specific and zoonotic genotypes. Pigs are considered one of the main reservoirs of this pathogen given its high reported prevalence in pigs, and pigs may harbor zoonotic and pig-specific genotypes. Therefore, genotyping of isolates from pigs and other animals is essential for the control of E. bieneusi infection. In Japan, it remains unclear whether this pathogen is present in the porcine population. In the present study, we examined 30 fecal samples from pigs reared on 6 farms in western Japan. Ten pigs (33%) were found to be positive when assessed by polymerase chain reaction. The genotypes were varied and were found to be animal specific (EbpA, H, PigEBITS5) and zoonotic (D, EbpC) in genotype. The observation that pigs in Japan appear to be infected with zoonotic and animal genotypes of E. bieneusi raises questions about the prevalence of this infection among the human population in Japan.
    No preview · Article · Oct 2009 · Vector borne and zoonotic diseases (Larchmont, N.Y.)
  • [Show abstract] [Hide abstract] ABSTRACT: A coprological survey was performed at a slaughterhouse in Osaka, Japan, from 2004 to 2007 on 129 pigs reared in 8 prefectures, and on 213 cattle reared in 21 prefectures. Eimeria spp., Trichuris suis, Ascaris suum and Metastrongylus spp. infections were found in 52 (40.3%), 32 (24.8%), 19 (14.7%) and 3 pigs (2.3%), respectively, while Eimeria spp., Capillaria bovis and Trichuris sp. infections were detected in 163 (76.5%), 15 (7.0%) and 8 cattle (3.8%), respectively. Our results suggest that environmentally resistant oocysts and eggs of parasites could be widespread at the farms examined.
    No preview · Article · Sep 2009 · Journal of Veterinary Medical Science
  • [Show abstract] [Hide abstract] ABSTRACT: Blastocystis hominis is a zoonotic intestinal protozoan parasite whose pathogenic potential is still controversial. The aim of the present study was to clarify the pathogenicity of Blastocystis parasites in rats. Oral inoculation with 1 x 10(5) cysts of Blastocystis sp. strain RN94-9 in rats resulted in chronic infection in the cecum at least until 4 weeks after infection. Histological examination revealed neither mucosal sloughing nor inflammatory cell infiltration but showed a slight but significant increase in goblet cell numbers in the cecal mucosa 1-3 weeks post-infection. Differential staining of acidic and neutral mucins by the alcian blue-periodic acid-Schiff method showed that the predominantly increased cells were neutral mucin(+) but not acidic mucin(+) goblet cells. Reverse transcription real-time polymerase chain reaction studies demonstrated significant upregulation of the expression of interferon-gamma, interleukin (IL)-12, and tumor necrosis factor alpha, but not IL-6 or granulocyte-macrophage colony-stimulating factor, in the cecal mucosa at 2 and/or 3 weeks post-infection. The induction of local host responses, including mild goblet cell hyperplasia, and significant upregulation of type-1 and proinflammatory cytokines, suggest that Blastocystis sp. strain RN94-9 is a weakly pathogenic organism that could elicit proinflammatory as well as protective responses in local tissues.
    No preview · Article · Apr 2009 · Parasitology Research
  • Niichiro Abe · Isao Kimata · Motohiro Iseki
    [Show abstract] [Hide abstract] ABSTRACT: Enterocytozoon bieneusi is an emerging and clinically significant enteric pathogen in humans associated mainly with chronic diarrhea. It has been found in a variety of wild, domestic and companion mammals and birds. To date, epidemiological surveys of E. bieneusi infection in humans, other mammals and birds have been performed in more than 21 countries in Africa, the Americas, Australasia and Europe. In Asia E. bieneusi has been found in India, Thailand, Vietnam and Korea, but it has been quite unclear whether this pathogen is present in Japan. In the present study, we examined 149 DNAs extracted from 45 human (9 of them HIV-positive) and 104 animal fecal samples by PCR. Two dogs and a cat were positive and their genotypes were found to be dog specific and zoonotic (genotype K) types, respectively. Present study is the first record of E. bieneusi in Japan.
    No preview · Article · Mar 2009 · Journal of Veterinary Medical Science
  • [Show abstract] [Hide abstract] ABSTRACT: Previously, we reported that an isolate of novel type of Cryptosporidium andersoni detected in cattle in Japan contained Type A (identical to C. andersoni reported previously) and Type B (having a thymine nucleotide insertion unlike the Type A) genotypes in the 18S rRNA gene. Here, we conducted an extensive investigation of Cryptosporidium infections in adult cattle in Japan from 2004 to 2007. Consequently, Cryptosporidium sp. were detected in 12 of the 205 cattle examined (5.9%), and partial sequences of the Cryptosporidium oocyst wall protein (COWP) gene in all isolates were identical to those of the previously reported data for C. andersoni whereas two signals were observed in the sequence of the partial 18S rRNA gene in all the isolates. In transmission studies using five of the isolates, they all infected SCID mice. Modified multiplex PCR using DNA of a single oocyst isolated from the infected SCID mice revealed that the partial sequences in the 18S rRNA gene of 40-80% of 10 isolates were identical to the Type A genotype of C. andersoni and those of other samples were identical to the Type B genotype. These results suggested that the C. andersoni novel type is widespread in cattle throughout Japan, and have multiple copies (Types A and B) in the 18S rRNA gene.
    No preview · Article · Oct 2008 · Veterinary Parasitology
  • M Matsubayashi · H Takase · I Kimata · H Nakagawa · H Tani · K Sasai · E Baba
    [Show abstract] [Hide abstract] ABSTRACT: Cryptosporidium parvum is an intracellular protozoan parasite belonging to the phylum Apicomplexa, and a major cause of waterborne gastroenteritis throughout the world. Invasive zoites of apicomplexan parasites, including C. parvum, are thought to have characteristic organelles on the apical apex; however, compared with other parasites, the cytoskeletal ultrastructure of C. parvum zoites is poorly understood. Thus, in the present study, we ultrastructurally examined C. parvum sporozoites using electron microscopy to clarify the framework of invasive stages. Consequently, at the apical end of sporozoites, 3 apical rings and an electron-dense collar were seen. Two thick central microtubules were seen further inside sporozoites and extended to the posterior region. Using anti-alpha and -beta tubulin antibodies generated from sea urchin and rat brain, both antibodies cross-reacted at the apical region of sporozoites in immunofluorescent morphology. The molecular mass of C. parvum alpha tubulin antigen was 50 kDa by Western blotting and the observed apical cytoskeletal structures were shown to be composed of alpha tubulin by immunoelectron microscopy. These results suggested that C. parvum sporozoites were clearly different in their cytoskeletal structure from those of other apicomplexan parasites.
    No preview · Article · Apr 2008 · Parasitology
  • [Show abstract] [Hide abstract] ABSTRACT: Cryptosporidium oocysts were detected in the feces of cattle in Saga, Japan. Isolates were morphologically large. We attempted to identify the species or genotypes of the isolates by analyzing the partial sequences of the 18S rRNA and Cryptosporidium oocyst wall protein (COWP) genes, and measuring the infectivity in mice. The isolates showed 100% homology with Cryptosporidium andersoni in the COWP gene sequence and it could be transmitted to mice, but in the 18S rRNA gene, there was an additional signal in the ABI sequence chromatogram. To examine the additional signal, we analyzed both the 18S rRNA and the COWP gene sequences of a single oocyst passaged from mice using a modified multiplex PCR that was able to amplify both genes. As a result, it was revealed that two distinct genotypes (Types A and B) of a novel C. andersoni type existed in the 18S rRNA gene, whereas the COWP gene sequences of both oocysts were identical to C. andersoni. Although the sequence of the 18S rRNA gene of Type A was identical to that of C. andersoni, that of Type B had a thymine insertion and was not identical to any sequence registered with GenBank. Here we report that this is a new type of C. andersoni.
    No preview · Article · Dec 2007 · Veterinary Parasitology
  • [Show abstract] [Hide abstract] ABSTRACT: To investigate Cryptosporidium infection among healthy people, we collected stool samples from 150 healthy individuals in Gokseong, Muan, and Imshil Counties, southwest Korea, where neighbors on both an animal farm and a river respectively. In 12 of 150 samples, Cryptosporidium oocysts were detected by means of modified acid-fast staining. The bovine genotype, Cryptosporidium parvum, was identified by PCR/RFLP and 18S rRNA sequencing. C. parvum existed endemically in these areas, and the residents showed a relatively higher infection rate for C. parvum than that for C. hominis. Our results indicate that countermeasures against Cryptosporidium infection must be taken in these areas to ensure human health.
    No preview · Article · Nov 2007 · Journal of Veterinary Medical Science
  • [Show abstract] [Hide abstract] ABSTRACT: Most Blastocystis hominis isolates from humans are believed to be potentially zoonotic. This is because B. hominis isolates found in a variety of other host species have been found to have identical or relatively similar genotypes to those found in human isolates. However, the transmission of human B. hominis isolates to other animals has not been confirmed experimentally. In this study, the infectivity associated with several unique human Blastocystis genotypes (subtypes 2, 3, 4 and 7) was therefore investigated by infecting chickens and rats with two isolates of each subtype experimentally. The results showed that one isolate of subtype 4 and one isolate of subtype 7 was capable of infecting both chickens and rats, while two isolates of subtype 2, another isolate of subtype 4, and another isolate of subtype 7 could only infect chickens. Conversely, two isolates of subtype 3 failed to infect either of the animals. These results confirmed that several genotypes from human isolates could infect chickens and/or rats, indicating that chickens and rats are suitable experimental animal models for studying the zoonotic potential of human Blastocystis isolates.
    No preview · Article · Jul 2007 · Parasitology International
  • [Show abstract] [Hide abstract] ABSTRACT: Cryptosporidium parvum is a well-known intestinal parasite which is associated with severe acute diarrhea in humans and animals. This parasite is composed of morphologically identical but genetically different multiple genotypes. In humans, cryptosporidiosis is mainly caused by two C. parvum genotypes, human genotype (previously known as genotype 1 and recently proposed as new species C. hominis) and cattle genotype (previously known as genotype 2). However, recent molecular studies indicate the genetic heterogeneity among the isolates of C. parvum human or cattle genotype. Therefore, identification of the isolates at the subgenotype level is more useful for control of the Cryptosporidium infection or for understanding of the population structure of C. parvum genotypes. In the present study, we identified the subgenotypes of the C. parvum human or cattle genotype isolates from humans and animals in Japan using DNA sequencing analysis of the C. parvum 60-kDa glycoprotein gene (GP60) and showed the new subgenotype in a raccoon dog isolate. This study suggested that C. parvum cattle genotype might be composed of zoonotic and host-specific multiple subgenotypes.
    No preview · Article · Sep 2006 · Parasitology Research
  • Niichiro Abe · Kazunari Tominaga · Isao Kimata
    No preview · Article · Mar 2006 · Japanese journal of infectious diseases