Katsuya Hirai

Bio: Katsuya Hirai is an academic researcher from Gifu University. The author has contributed to research in topics: Coxiella burnetii & Infectious bursal disease. The author has an hindex of 40, co-authored 134 publications receiving 3938 citations.

Proposal of Chlamydia pecorum sp. nov. for Chlamydia strains derived from ruminants.

Abstract: Chlamydia pecorum sp. nov. is proposed as the fourth species of the genus Chlamydia on the basis of the results of a genetic analysis of Chlamydia strains that were isolated from cattle and sheep which had various diseases, including sporadic encephalitis, infectious polyarthritis, pneumonia, and diarrhea. The levels of DNA-DNA homology between C. pecorum and strains of C. psittaci, Chlamydia pneumoniae, and Chlamydia trachomatis were less than 10%. Several DNA probes were used to identify C. pecorum. The C. pecorum strains were distinguished from C. psittaci strains by the results of immunological assays, including an immunofluorescence antibody assay performed with monoclonal antibodies and an immunoblot analysis of the immunological specificity of the major outer membrane protein. Species identification was based on results obtained from DNA analyses and serology. The type strain of C. pecorum is strain ATCC VR628.

Coxiella burnetii Isolates Cause Genogroup-Specific Virulence in Mouse and Guinea Pig Models of Acute Q Fever

Abstract: Q fever is a zoonotic disease of worldwide significance caused by the obligate intracellular bacterium Coxiella burnetii. Humans with Q fever may experience an acute flu-like illness and pneumonia and/or chronic hepatitis or endocarditis. Various markers demonstrate significant phylogenetic separation between and clustering among isolates from acute and chronic human disease. The clinical and pathological responses to infection with phase I C. burnetii isolates from the following four genomic groups were evaluated in immunocompetent and immunocompromised mice and in guinea pig infection models: group I (Nine Mile, African, and Ohio), group IV (Priscilla and P), group V (G and S), and group VI (Dugway). Isolates from all of the groups produced disease in the SCID mouse model, and genogroup-consistent trends were noted in cytokine production in response to infection in the immunocompetent-mouse model. Guinea pigs developed severe acute disease when aerosol challenged with group I isolates, mild to moderate acute disease in response to group V isolates, and no acute disease when infected with group IV and VI isolates. C. burnetii isolates have a range of disease potentials; isolates within the same genomic group cause similar pathological responses, and there is a clear distinction in strain virulence between these genomic groups.

Isolation of Coxiella burnetii from dairy cattle and ticks, and some characteristics of the isolates in Japan.

Abstract: Coxiella burnetii was isolated from raw milk (36/214, 16.8%) and uterus swab samples (13/61, 21.3%) originating from dairy cattle with reproductive disorders, aborted bovine fetus samples (2/4, 50%), mammary gland samples (4/50, 8%) originating from healthy dairy cattle, and tick samples (4/15, 26.7%) originating from 2 pastures. Fifty-nine strains had various degrees of pathogenicity, high (8; 13.6%), moderate (28; 47.5%) and low (23; 39%), for guinea pigs. The results of isolation suggested a high prevalence of Coxiella infection in dairy cattle with reproductive problems in Japan. Twelve strains (7, 2 and 3 strains from cattle, ticks and humans, respectively) and the reference Nine Mile strain of phases I and II were propagated in both yolk sacs of embryonated hen eggs and Buffalo green monkey (BGM) cell cultures. Protein profiles of these strains were similar to those of the reference strain of phase I. Lipopolysaccharide (LPS) profiles of 12 strains were similar to those of the reference strain of phase I and different from those of the reference strain of phase II. The LPS profiles of 12 strains suggested that these strains are associated with an acute form of Q fever.

The immunodepressive effect of infectious bursal disease virus in chickens.

Abstract: SUMMARY Infectious bursal disease virus (IBVD) depressed the humoral antibody response of chickens to various vaccines. The virus had that effect whether injected at the same time as vaccination or 4 or 7 days before. The depression was slightly greater when injection was 7 days before, and was most pronounced in chickens inoculated with IBDV when 6 weeks old, slight in 4-week-olds, and absent in 2-week-olds. Protection against challenge by virulent ND virus 3 weeks after ND vaccination showed the marked differences between IBDV-inoculated and uninoculated chickens.

Reorganization of genera in the families Rickettsiaceae and Anaplasmataceae in the order Rickettsiales: unification of some species of Ehrlichia with Anaplasma, Cowdria with Ehrlichia and Ehrlichia with Neorickettsia, descriptions of six new species combinations and designation of Ehrlichia equi and 'HGE agent' as subjective synonyms of Ehrlichia phagocytophila.

Abstract: The genera Anaplasma, Ehrlichia, Cowdria, Neorickettsia and Wolbachia encompass a group of obligate intracellular bacteria that reside in vacuoles of eukaryotic cells and were previously placed in taxa based upon morphological, ecological, epidemiological and clinical characteristics. Recent genetic analyses of 16S rRNA genes, groESL and surface protein genes have indicated that the existing taxa designations are flawed. All 16S rRNA gene and groESL sequences deposited in GenBank prior to 2000 and selected sequences deposited thereafter were aligned and phylogenetic trees and bootstrap values were calculated using the neighbour-joining method and compared with trees generated with maximum-probability, maximum-likelihood, majority-rule consensus and parsimony methods. Supported by bootstrap probabilities of at least 54%, 16S rRNA gene comparisons consistently clustered to yield four distinct clades characterized roughly as Anaplasma (including the Ehrlichia phagocytophila group, Ehrlichia platys and Ehrlichia bovis) with a minimum of 96.1% similarity, Ehrlichia (including Cowdria ruminantium) with a minimum of 97.7% similarity, Wolbachia with a minimum of 95.6% similarity and Neorickettsia (including Ehrlichia sennetsu and Ehrlichia risticii) with a minimum of 94.9% similarity. Maximum similarity between clades ranged from 87.1 to 94.9%. Insufficient differences existed among E. phagocytophila, Ehrlichia equi and the human granulocytic ehrlichiosis (HGE) agent to support separate species designations, and this group was at least 98.2% similar to any Anaplasma species. These 16S rRNA gene analyses are strongly supported by similar groESL clades, as well as biological and antigenic characteristics. It is proposed that all members of the tribes Ehrlichieae and Wolbachieae be transferred to the family Anaplasmataceae and that the tribe structure of the family Rickettsiaceae be eliminated. The genus Anaplasma should be emended to include Anaplasma (Ehrlichia) phagocytophila comb. nov. (which also encompasses the former E. equi and the HGE agent), Anaplasma (Ehrlichia) bovis comb. nov. and Anaplasma (Ehrlichia) platys comb. nov., the genus Ehrlichia should be emended to include Ehrlichia (Cowdria) ruminantium comb. nov. and the genus Neorickettsia should be emended to include Neorickettsia (Ehrlichia) risticii comb. nov. and Neorickettsia (Ehrlichia) sennetsu comb. nov.

Lounging in a lysosome: the intracellular lifestyle of Coxiella burnetii.

Abstract: Summary Most intracellular parasites employ sophisticated mechanisms to direct biogenesis of a vacuolar replicative niche that circumvents default maturation through the endolysosomal cascade. However, this is not the case of the Q fever bacterium, Coxiella burnetii. This hardy, obligate intracellular pathogen has evolved to not only survive, but to thrive, in the harshest of intracellular compartments: the phagolysosome. Following internalization, the nascent Coxiella phagosome ultimately develops into a large and spacious parasitophorous vacuole (PV) that acquires lysosomal characteristics such as acidic pH, acid hydrolases and cationic peptides, defences designed to rid the host of intruders. However, transit of Coxiella to this environment is initially stalled, a process that is apparently modulated by interactions with the autophagic pathway. Coxiella actively participates in biogenesis of its PV by synthesizing proteins that mediate phagosome stalling, autophagic interactions, and development and maintenance of the mature vacuole. Among the potential mechanisms mediating these processes is deployment of a type IV secretion system to deliver effector proteins to the host cytosol. Here we summarize our current understanding of the cellular events that occur during parasitism of host cells by Coxiella.

Emended description of the order Chlamydiales, proposal of Parachlamydiaceae fam. nov. and Simkaniaceae fam. nov., each containing one monotypic genus, revised taxonomy of the family Chlamydiaceae, including a new genus and five new species, and standards for the identification of organisms.

Abstract: The current taxonomic classification of Chlamydia is based on limited phenotypic, morphologic and genetic criteria This classification does not take into account recent analysis of the ribosomal operon or recently identified obligately intracellular organisms that have a chlamydia-like developmental cycle of replication Neither does it provide a systematic rationale for identifying new strains In this study, phylogenetic analyses of the 16S and 23S rRNA genes are presented with corroborating genetic and phenotypic information to show that the order Chlamydiales contains at least four distinct groups at the family level and that within the Chlamydiaceae are two distinct lineages which branch into nine separate clusters In this report a reclassification of the order Chlamydiales and its current taxa is proposed This proposal retains currently known strains with > 90% 16S rRNA identity in the family Chlamydiaceae and separates other chlamydia-like organisms that have 80--90% 16S rRNA relatedness to the Chlamydiaceae into new families Chlamydiae that were previously described as ‘Candidatus Parachlamydia acanthamoebae’ Amann, Springer, Schonhuber, Ludwig, Schmid, Muller and Michel 1997, become members of Parachlamydiaceae fam nov, Parachlamydia acanthamoebae gen nov, sp nov ‘Simkania’ strain Z becomes the founding member of Simkaniaceae fam nov, Simkania negevensis gen nov, sp nov The fourth group, which includes strain WSU 86--1044, was left unnamed The Chlamydiaceae, which currently has only the genus Chlamydia, is divided into two genera, Chlamydia and Chlamydophila gen nov Two new species, Chlamydia muridarum sp nov and Chlamydia suis sp nov, join Chlamydia trachomatis in the emended genus Chlamydia Chlamydophila gen nov assimilates the current species, Chlamydia pecorum, Chlamydia pneumoniae and Chlamydia psittaci, to form Chlamydophila pecorum comb nov, Chlamydophila pneumoniae comb nov and Chlamydophila psittaci comb nov Three new Chlamydophila species are derived from Chlamydia psittaci: Chlamydophila abortus gen nov, sp nov, Chlamydophila caviae gen nov, sp nov and Chlamydophila felis gen nov, sp nov Emended descriptions for the order Chlamydiales and for the family Chlamydiaceae are provided These families, genera and species are readily distinguished by analysis of signature sequences in the 165 and 235 ribosomal genes