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Biomedical subjects

J C Bridger

Publications and source records attributed to J C Bridger.

At least 37 records · Page 2Linked to original sources
PubMed1992

The effect of dexamethasone-induced immunosuppression on the development of faecal antibody and recovery from and resistance to rotavirus infection.

Rotavirus-naive and rotavirus-immune gnotobiotic calves were treated with high doses of dexamethasone (DX) to suppress the immune system. Calves were then infected with a virulent rotavirus inoculum, J-160, to investigate the role of immune responses both in recovery from primary rotavirus infection and in resistance to secondary rotavirus infection. Treatment of calves with DX markedly suppressed in vitro responsiveness of peripheral blood lymphocytes to mitogens within 48 h of the start of DX treatment. Suppression was similar in rotavirus-naive and rotavirus-immune calves. In contrast, the effect of DX treatment on specific antibody responses differed depending on when DX treatment started in relation to rotavirus infection. When DX treatment commenced prior to primary rotavirus infection both systemic and local specific antibody responses were inhibited. These calves, in which mitogen and antibody responses were suppressed, exhibited greater clinical signs than did control calves after infection with virulent rotavirus, but virus excretion was affected in only one of the two calves. When DX treatment was started after primary rotavirus infection but before secondary infection, systemic and local antibody responses to the primary infection and to the challenge infection were not affected. These calves resisted challenge with virulent virus as did DX-untreated rotavirus-immune calves, even though mitogen responses were suppressed. We conclude that in a primary rotavirus infection, virus excretion ceased when both antibody and mitogen responses were suppressed. Resistance to secondary rotavirus infection occurred when mitogen responsiveness was suppressed, but when antibody levels were normal. Thus, no evidence was obtained that fully functional cell-mediated immune mechanisms are essential for resistance to rotavirus infection. Evidence was provided for the ability of parenteral treatment with DX to suppress mucosal as well as systemic antibody responses.

Animals↗
PubMed1992

A study of the basis of virulence variation of bovine rotaviruses.

Rotaviruses are enteric pathogens of cattle but sub-clinical infections are common. Virulence variation has been identified with bovine rotaviruses and some rotaviruses replicated without clinical signs in non-immune calves. The rotavirus genome is composed of eleven segments of double-stranded RNA and the fourth largest segment codes for a non-glycosylated surface protein, VP4, which has been linked with virulence. In the present study the biological basis of rotavirus virulence variation was studied in vivo and compared with the known properties of the fourth gene. Calves were inoculated orally with a virulent rotavirus or a rotavirus of low virulence which multiplied but failed to cause diarrhoea. They were taken for necropsy at intervals of 2 days after inoculation. Clinical signs, virus in faeces and the percentage of infected small intestinal epithelium were determined. Damage to the small intestine was assessed by measurement of villus heights and crypt-cell production rates. Virulence was associated with a greater level of colonization of the small intestinal epithelium, greater enterocyte damage and preferential infection of the upper small intestine. The fourth gene determines the ability of rotaviruses to spread in vitro and the finding that virulence was associated with greater colonization in vivo raises the possibility that this gene may have an important role in rotavirus virulence.

Animals↗
PubMed1992

The pathogenicity of two porcine rotaviruses differing in their in vitro growth characteristics and genes 4.

The pathogenicity of two rotavirus variants, 4F and 4S, obtained following adaptation to cell culture of rotavirus from a diarrhoeic pig in China, was compared by serial passage in 24 gnotobiotic piglets. The rotavirus variants have markedly different growth characteristics in vitro, and their genome profiles differ only in the relative migration of genes 4. Both cell culture-grown variants replicated to an equal extent in gnotobiotic piglets and neither caused disease, although weight gain was slightly affected in piglets inoculated with the 4F variant. During five serial pig-to-pig passages, variant 4F became highly pathogenic at the fourth and fifth passages, causing severe diarrhoea and weight loss, and premature death in two animals. Piglets inoculated with rotavirus variant 4S remained healthy during all passages although weight gain was slightly affected. Mean duration and peak infectivity titres of virus shedding were similar for both variants. Thus, variant 4F, which grew slowly and produced small plaques in vitro and had the faster migrating gene 4, was pathogenic in pigs, whereas variant 4S was apathogenic.

Adaptation, Biological↗
PubMed1990

Group C rotavirus associated with fatal enteritis in a family outbreak.

A family outbreak of gastroenteritis involving three adults and three children is described in which diarrhoea and vomiting were the main clinical features. One infant died in whom no pathogens could be detected in either small or large intestinal postmortem samples. Stool samples from two symptomatic siblings contained rotaviruses as demonstrated by electron microscopy. Both of these faecal samples were negative when assayed in a group A specific rotavirus enzyme-linked immunosorbent assay (ELISA) and subsequent genomic analysis of these rotaviruses was suggestive of group C rotavirus. Serological evidence showed that these atypical rotaviruses were members of serogroup C. Other atypical rotaviruses in faecal samples from sporadic cases in symptomatic children were detected over a similar time period and location. These had electrophoretic RNA profiles similar to those in the family outbreak. Furthermore, seroepidemiological studies detected group C rotavirus antibody in blood donors resident in the location of the family outbreak.

Adult↗
PubMed1988

Atypical rotaviruses in Australian pigs.

Atypical rotaviruses of two different electropherotypes were identified by PAGE in 16 out of 237 (5.3%) diarrhoeic faecal samples from piglets. A cDNA probe derived from a group B rotavirus hybridized strongly to two samples (of 3 tested) with electropherotypes suggestive of groups B or E, identifying them as group B. The electropherotype(s) of seven samples were typical of group C. By immunofluorescence, antibodies to group B, C, and E rotaviruses have been detected in sera from Australian sows, so it appears that atypical rotaviruses belonging to three different groups occur in pigs in this country.

Animals↗
PubMed1987

Novel rotaviruses in animals and man.

Novel (non-group A) rotaviruses have many of the morphological, biochemical and biological properties described originally for group A rotaviruses but they do not share the same group antigens. By negative-stain electron microscopy, novel rotaviruses have the characteristic rotavirus morphology, although with some novel rotaviruses the characteristic single- and double-shelled particles may not be readily apparent. Comparison of novel rotaviruses in serological tests has revealed the existence of at least six rotavirus serogroups, A to F, with the original rotaviruses belonging to group A. As with group A rotaviruses, viruses from different animal species, including man, can belong to the same serogroup. A further point of difference between novel and group A rotaviruses is their genome profiles, which lack the triplet of segments in the 7-8-9 region of group A rotaviruses. This is a useful diagnostic aid. Novel rotaviruses have been found in farm animals and man. They can cause enteritis experimentally and infect villus enterocytes. In chickens, turkeys, lambs and pigs the viruses and/or antibody to them are commonly found, in association with either clinical or subclinical infection. In humans one type of novel virus has emerged as a cause of severe diarrhoeal disease in adults. The possible reasons for the relatively recent discovery of the novel rotaviruses are discussed.

Animals↗
PubMed1987

Avirulent rotavirus infections protect calves from disease with and without inducing high levels of neutralizing antibody.

Two bovine rotaviruses, C3-160 and 17/4, which multiplied in calves without inducing disease, were studied for their ability to protect against disease caused by a virulent rotavirus, CP-1. Rotavirus 17/4 and the virulent virus CP-1 cross-neutralized poorly and, on the basis of 20-fold differences in neutralization titres, belonged to different serotypes. Rotaviruses C3-160 and CP-1 were more closely related: neutralization of the CP-1 virus by C3-160 antisera was within 20-fold of the homologous titre although neutralization of the C3-160 virus by CP-1 antisera was not. Nine gnotobiotic calves infected with either C3-160 or 17/4, had rotavirus antibody in their faeces and/or serum 21 days after oral inoculation as detected by indirect immunofluorescence and IgG, IgM and/or IgA antibodies by ELISA. As expected from the antigenic relationships between the viruses, the sera and faeces from the four calves infected with C3-160 contained moderate levels of neutralizing antibody to the virulent virus CP-1 and the sera and most of the faeces from the five calves infected with 17/4 contained undetectable or low levels. When challenged with CP-1 on day 21, four age-matched controls developed disease whereas all of four calves previously infected with C3-160 and four of five calves previously infected with 17/4 were protected from disease. It was concluded that avirulent rotavirus infection provided protection against disease caused by a virulent rotavirus even when one of the avirulent viruses was poorly related to the virulent virus by neutralization. Mechanisms other than neutralizing antibody appeared to be important in protection.

Animals↗
PubMed1986

Microbiology of calf diarrhoea in southern Britain.

Faeces samples from calves with diarrhoea in 45 outbreaks were examined for six enteropathogens. Rotavirus and coronavirus were detected by ELISA in 208 (42 per cent) and 69 (14 per cent) of 490 calves respectively; calici-like viruses were detected by electron microscopy in 14 of 132 calves (11 per cent). Cryptosporidium were detected in 106 of 465 (23 per cent), Salmonella species in 58 of 490 (12 per cent) and enterotoxigenic Escherichia coli bearing the K99 adhesin (K99+ E coli) in nine of 310 calves (3 per cent). In the faeces of 20 per cent of calves with diarrhoea more than one enteropathogen was detected; in 31 per cent no enteropathogen was found. Faces samples from 385 healthy calves in the same outbreaks were also examined. There was a significant statistical association of disease with the presence of rotavirus, coronavirus, Cryptosporidium and Salmonella species (P less than 0.001). Healthy calves were not examined for calici-like viruses and the association of K99+ E coli with disease was not analysed because there were too few positive samples. Rotavirus infections were more common in dairy herds and single suckler beef herds whereas Salmonella infections were more often found in calf rearing units. Cryptosporidium were more common in single and multiple suckler beef herds. K99+ E coli were found in one dairy herd and one multiple suckler beef herd both with unhygienic calving accommodation. Variations in coronavirus detection among different farm types were not statistically significant. In this survey rotavirus was the most commonly detected agent in calf diarrhoea and Cryptosporidium were found in approximately one quarter of affected calves. Infection with Salmonella species was widespread, but K99+ E coli infections were less common in the United Kingdom than in other countries.

Animals↗
PubMed1986

A new type of atypical rotavirus in pigs.

Two independent isolates of an unusual type of rotavirus were obtained from over 900 faecal samples obtained from piglets with diarrhoea. Genome profiles, containing eleven segments, were not characteristic of group A electropherotypes and corresponded to an atypical virus. The profiles were, however, distinct from those of other previously described atypical porcine rotaviruses. Serological comparisons showed that the two isolates were related, but unrelated to other known groups of porcine rotavirus. The new isolates were passaged in gnotobiotic piglets in which they caused mild clinical signs of enteritis. A survey of porcine sera from the United Kingdom indicated a widespread distribution of antibody to this virus in pigs aged 10 weeks and over.

Animals↗
PubMed1986

Variation in virulence of bovine rotaviruses.

Forty-six gnotobiotic calves aged less than 16 days or 42-116 days were infected with three strains of bovine rotavirus designated C3-160, CP-1 and PP-1. Each virus was passaged and cloned in cell culture (cloned viruses) but CP-1 and PP-1 were also used before culture (faecal viruses). Infection of calves aged less than 16 days with faecal or cloned CP-1 caused disease whereas cloned C3-160 and faecal or cloned PP-1 caused subclinical infections. The clinical signs of disease were change in faecal colour to pale yellow or cream, increase of 2- to 7-fold in the volume of faecal output and, usually, anorexia. With the virulent CP-1 virus and the avirulent C3-160, similar amounts of virus were excreted in the faeces for 4-6 days. Infection of calves aged 56-116 days with faecal CP-1 produced disease of similar severity to that seen in calves aged 7-10 days infected with the same virus. No differences in clinical signs, virus excretion or levels of convalescent antibody were seen between the two groups. With cloned CP-1, 5 of 8 older calves developed disease but 3 showed only mild signs of infection. It was concluded that two strains of rotavirus caused sub-clinical infections in young calves while a third was virulent in calves up to at least 116 days of age.

Animals↗
PubMed1986

Definition of two new groups of atypical rotaviruses.

Comparative antigenic and nuclei acid analyses were carried out on two new atypical rotavirus isolates coming respectively from chickens (D/132) and pigs (E/DC-9). Indirect immunofluorescence showed that each virus carried different group antigens which were also distinct from those of previously described rotavirus groups. By genome profile analysis each virus had a pattern of genomic RNAs clearly distinct from those of the other rotavirus groups. Comparative terminal fingerprinting of corresponding genome segments from the two viruses showed large differences between them, indicating that all of their genomic RNAs had significant differences in sequence both from each other and from the three previously defined rotavirus groups. On the basis of these results, extension of the number of rotavirus groups from three to five is proposed, with isolates D/132 and E/DC-9 being the type members of groups D and E respectively.

Animals↗
PubMed1986

Group C rotaviruses in humans.

Atypical rotaviruses obtained from human feces from Australia, Brazil, and the United Kingdom were shown by a combination of techniques--immunoelectron microscopy, immunofluorescence, genome profile analysis, terminal fingerprint analysis of genome segments, and dot-blot hybridization--to be related to group C porcine rotaviruses. The prevalence of antibody to group C rotaviruses was found to be low in human sera and immunoglobulin pools from six countries. No signs of infection were obtained when one of the human viruses was inoculated into gnotobiotic piglets. We conclude that the atypical human viruses are the first examples of group C rotaviruses in humans.

Animals↗
PubMed1985

Dysentery caused by Escherichia coli (S102-9) in calves: natural and experimental disease.

A dysentery syndrome was recognized among the Institute's calves at 18 to 21 days of age. It was reproduced experimentally in gnotobiotic calves with an atypical Escherichia coli (S102-9) isolated from the affected calves. In both natural and experimental disease the calves passed copious bright red blood in the feces and developed diarrhea. Walls of the colon and rectum were thickened, and the mucosa was reddened and covered by an exudate that contained mucus and blood clots. Bacteria were seen closely adherent to the luminal surfaces of enterocytes, often in cup-shaped depressions or on cytoplasmic pedestals. Microvilli were distorted, disorientated or absent. There was exfoliation of infected enterocytes and a mild acute inflammation of the underlying lamina. In two of five calves with natural disease, the adherent bacteria did not stain by the immunoperoxidase method with antisera raised against E. coli (S102-9). This indicated that there was possibly more than one bacterial cause of the syndrome. Lesions in experimentally infected calves were indistinguishable from those produced by some E. coli which are enteropathogenic for man, rabbits, and pigs.

Animals↗
PubMed1985

Plasma enteroglucagon and neurotensin levels in gnotobiotic calves infected with enteropathogenic and non-enteropathogenic viruses.

Five gnotobiotic calves were each infected with five viruses. Each calf was inoculated with coronavirus at seven days old, followed by astrovirus, Newbury agent, parainfluenzavirus type 3 and rotavirus at intervals of two weeks. Three of the viruses were enteropathogenic (bovine coronavirus, bovine calici-like virus and bovine rotavirus) and two were not (bovine astrovirus and parainfluenzavirus type 3). Plasma levels of the peptide hormones enteroglucagon and neurotensin and faecal output were measured daily and xylose absorption was studied before and after each infection. A close correlation was found between a rise in plasma enteroglucagon and neurotensin and infection with enteropathogenic viruses. The three enteropathogenic viruses caused increased daily faecal output, and elevated plasma levels of enteroglucagon and neurotensin, while the non-enteropathogens did not. The calici-like virus and rotavirus but not the coronavirus caused xylose malabsorption.

Animals↗