Biomedical subjects
Publications and source records attributed to P Porter.
An immunisation schedule is described that reproducibly induces long latent period skin sensitising antibody (immunoglobulin) in calves by a combined oral/parenteral route. This response is only directed towards the protein component of the antigen and is boosted upon challenge injection.
An antibody of known specificity and active in long (72 hours) latent period passive cutaneous anaphylactic reactions, was isolated and partially purified from bovine serum. This antibody was not associated with immunoglobulins IgG, IgM or IgA. A rabbit antiserum raised against this antibody and used as an immunoabsorbent, successfully recovered skin sensitising antibody from bovine reaginic serum.
Mucosal antibodies in vivo and in vitro interfere with the stability of plasmids coding for important virulence determinants in porcine enteropathogenic E. coli (EEC), such as the adhesion determinants K88ab and K88ac. The effector antibody is not directed against K88 antigens and is not serotype specific, but an antigen common to K88+ strains is implicated. Further lack of pathogen specificity is exemplified by antibody elimination of the more recently discovered K88ad plasmid. Antibodies that interfere with K88 plasmids do not affect K99, which now appears as an alternative adhesion factor in porcine enteropathogenic E. coli. This plasmid can be eliminated, however, by antibodies having K99 specificity. In extending the studies to drug-resistance plasmids, further evidence has emerged that mucosal antibodies may assist in host control of the reservoir of R factors in the intestinal microflora. A major effector mechanism is that secretory IgA and IgM antibodies from orally immunized pigs can block the transfer of R factors between donor and recipient strains of E. coli.
School problems are common in children with neuromuscular disease irrespective of their degree of handicap. They are related to difficulties in transportation and access, difficulties with adaptation of school tasks to the motorically handicapped, and difficulties that arise because of misunderstanding of the disease processes by teachers and parents. Most of these can be easily rectified by efforts by the clinic staff to educate school personnel and to enlist them as members of the treatment team. In view of the importance of the school experience to this group of patients, it is urged that these problems be identified and aggressively managed by those involved in the care of neuromuscularly handicapped children.
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Current approaches to the immunological control of enteric E. coli infections in pig herds concentrate on the provision of passive immunity for the neonate by multiple parenteral vaccination of the sow to stimulate colostral antibody production. Little account is taken of the kinetics of the animals' natural immune response. In particular the potential of the gut as a target organ for immunization has largely been ignored in practical disease control. A new approach to the problem, which combines oral with parenteral vaccination, stimulates a colostral antibody response closely mimicking a sow's natural response to infections and comparison between this and classical parenteral vaccination, using an acute E. coli infection model, demonstrated the greater protective efficacy conferred by the new protocol. The widespread use of this method of vaccination has been continuously monitored, using production parameters most relevant to the farming industry. From this evaluation of user experience and results of trials conducted in various locations, a new perspective is emerging which indicates the vaccine has a wider spectrum of biological activity than was expected. Production, health and environmental benefits are arising which could not have been predicted from a model merely concerned with the control of alimentary E. coli infection.
Antibody-producing hybridoma clones have been isolated following immunization of mice with human IgG. Twenty-five monoclonal antibodies (nine anti-C gamma 3, fourteen anti-C gamma 2, one anit-kappa and one anti-lambda) were selected for study of their cross-reactivity with the IgG of fifteen mammalian species and chicken immunoglobulin. Each antibody exhibited a unique reaction profile suggesting that human IgG expresses a very large repertoire of immunogenic epitopes. Whilst some antibodies showed a very restricted cross-reactivity profile for others a very wide reactivity profile was observed-including two clones producing autoantibodies. Antibodies demonstrating cross-reactivity between human Fc gamma and 7S chicken immunoglobulin allow its definitive assignment as a homologue of human IgG. Four clones demonstrated specificity for bovine IgG subclass gamma 1 and gamma 2 and the degree of reactivity allows their application to qualitative and quantitative assay systems. These studies suggest new perspectives for the characterization of immunoglobulins and the standardization of anti-immunoglobulin reagents.
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A simple immunoassay system has been evaluated for use on farm to examine the level of maternal immunoglobin absorbed by newborn calves. Whole blood can be used in the test rather than serum. The test proved easy and reliable when used in studies on 10 farms with 650 calves. More than 50 per cent of the animals were found to be colostrum deficient and, as with other studies, such calves were subject to health breakdown and poor performance although this could be adequately offset by good management.
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A field trial was conducted to test the efficacy of a vaccination programme which combines oral and parenteral antigen administration to produce IgM antibody in the colostrum of the sow. The trial involved 11 herds, each selected because of their history of neonatal Escherichia coli enteritis. Following more than 2300 farrowings, the progeny from vaccinated sows required 75 per cent less medication to maintain a good standard of health. The average neonatal mortality decreased from 13.8 to 7.0 per cent and the number of pigs weaned increased by 0.6 per litter.
The neonatal requirements for maternal passive immunity and the lactation immunobiology with regard to sow immunisation for neonatal protection are reviewed. A vaccination protocol which combines oral and parenteral antigen administration to produce antibody activity mediated mainly by IgM is described. Its efficacy in affording protection to neonatal piglets was tested against a lethal oral infection with a virulent strain of Escherichia coli "Abbottstown". Piglets suckled on vaccinated or non-vaccinated sows were exposed to an infective challenge in the gastrointestinal tract and the relative pathology in test and control groups observed over the neonatal period. Death ensued in 76 per cent of piglets suckled on control sows and 26 per cent of piglets suckled on sows vaccinated by two intramuscular injections. Litters suckled on orally vaccinated sows were able to resist a similar infective challenge, there being only one fatality out of 42 piglets.
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The ability of Eimeria tenella sporozoites to develop normally in cultured chick kidney cells was used as an indicator of the anticoccidial effects of sera and extracts of caecal contents or tissue. Pre-treatment of sporozoites with normal serum globulin enhanced the frequency of intracellular development but pre-treatment in balanced salt solution, without protein, damaged sporozoites so that most had lost the ability to differentiate, even when they were able to invade host cells. The same inhibitory effect was seen when sporozoites were incubated in extracts of caecal contents from non-immunized chickens, although parasitic development was unaffected when sporozoites were pretreated in similar extracts of mucosae. Extracts of immune caecal contents impaired both cell penetration and subsequent development. These results show that sporozoites can lose the ability to differentiate before the ability to penetrate cells and provide evidence of a possible synergism between non-specific factors and secretory antibodies in anticoccidial immunity.