Kenji Oonaka

ハトおよびカラスからのVero毒素産生性大腸菌 (VTEC) の分離および血清型

To clarify the source and route of infection with Vero toxin-producing Escherichia coli (VTEC) in humans, we sampled gastrointestinal contents and isolated VTEC from wild birds captured to exterminate harmful birds between August 1997 and January 1998. Pigeons were caught in Sagamihara-shi and crows were caught in Sagamihara-shi, Kawasaki-shi, Yokohama-shi, and the Tokyo metropolitan area. The following results were obtained. 1) VTEC was isolated from 32 of 521 birds (6.1%) examined. Among pigeons, VTEC was isolated from 25 of 262 birds (9.5%) captured in Sagamihara-shi. Among crows, VTEC was isolated from 7 of 184 birds (3.8%) captured in Sagamihara-shi, but not isolated from any bird of 11.4, and 60 birds captured in Yokohama-shi, Kawasaki-shi, and the Tokyo metropolitan area, respectively. 2) Toxin was typed in 33 isolates. There were four VT1-producing isolates (6.5%), 27 VT2-producing isolates (88.7%), and two VT1, VT2-producing isolates (4.8%). 3) The serotypes of the isolates were: O78: H-, 10; O152: H-, 7; O153: H19.2; O164: H-, 1; O128: H-, 1; O164/143: H-, and O1: HUT, 1. The serotype was unknown in 10 isolates. Among 10 isolates for which the serotype could not be determined, auto-aggregation was observed in one isolate. 4) EaeA was investigated in the 33 isolates, and 31 isolates (93.9%) possessed eaeA. The above findings showed that strains with same toxin types and serotypes of human diarrhea-derived VTEC were isolated from pigeons and crows, and the isolates frequently possessed eaeA, which is considered to have an important association with its pathology, suggesting that birds are involved in VTEC infection in humans as a source of infection.

Biology of fowl adenovirus type 1 infection of heterologous cells

The JM1/1 strain of fowl adenovirus (FAV) serotype 1 isolated from gizzard erosion was used to investigate the biology of FAV in homologous (susceptible) and heterologous cells. The FAV JM1/1 strain is capable of efficient multiplication in primary chicken kidney (CK) cells, but not in Crandell-Rees feline kidney (CRFK) cells or Vero cells. FAV adsorption in heterologous cells was slightly higher than in CK cells. An early gene encoding a DNA-binding protein and a late gene encoding the hexon protein were expressed in CK cells. Only the early gene was expressed in Vero cells. Neither of these genes was expressed in CRFK cells. These results suggest that the virus was unable to multiply effectively due to suppression of viral gene expression in the heterologous cells used in this study.

In vitro Anti-Influenza Virus Activity of Agaricus brasiliensis KA21

　Agaricus is known to have immunostimulatory and anti-tumor effects. However, the antiviral effects of Agaricus have not yet been examined. In the present study, the antiviral effects of an extract of Agaricus brasiliensis KA21 (AE) on the H1N1 influenza virus (PR8 strain) were investigated.　The anti-influenza virus effects of AE were examined by using the plaque formation inhibition test. AE inhibited the plaque formation of PR8 in a dose-dependent manner: 98 and 50% (IC50) inhibition at 2.5 and 0.99 mg/mL, respectively. To elucidate the mechanisms of AE, the direct actions and adsorption and invasion inhibition of AE were examined, and were found to have no inhibitory effect on PR8 infection. Thus, in vitro antiviral effects may somehow inhibit PR8 after the viral invasion of cells. These results demonstrated that it is expected that AE can effectively prevent the spread of the influenza virus.