A simple method for evaluation of colostrum status in calves

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.

Sow vaccination by combined oral and intramuscular antigen: a field study of maternal protection against neonatal Escherichia coli enteritis

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.

An examination of the O and K specificity involved in the antibody-induced loss of the K88 plasmid from porcine enteropathogenic strains of Escherichia coli

The heat-labile K88 antigen, a virulence determinant coded for by a transmissible plasmid, was eliminated from enteropathogenic strains of Escherichia coli by passage through media containing antibodies to the heat stable antigens of an Abbotstown (O149:K91,K88ac) strain. The plasmid-curing activity of O149 antisera was not O-antigen specific as O149, O45, O8 and O138 strains of E. coli could be 'cured' of their K88 plasmids by this technique. The curing activity was differentiated from the O-antibody by gel filtration, the O149 antibodies were eluted in the IgM peak while the curing activity was found in the IgG peak. In view of the lack of O-specificity and the absence of K88 antibodies it appears that antibodies to a common heat-stable antigenic determinant were involved in this phenomenon.

Intestinal defence of the neonatal pig: interrelationship of gut and mammary function providing surface immunity against colibacillosis

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.

A mechanism for secretory IgA-mediated inhibition of the cell penetration and intracellular development of Eimeria tenella

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.

Antibody induced elimination of the plasmid controlled K88 adhesion factor from a porcine enteropathogen

The heat labile K88 antigen which is a product of an episomal gene, was eliminated from a pocrine enteropathogen by passage through media containing sow colostrum antibodies raised against heart stable antigens of E. coli. In consequence the porcine enteropathogen lost its ability to adhere to and aggluinate chicken erythrocytes, and model system for piglet intestinal adhesion and virulence.

The role of secretory IgA in anti-coccidial immunity in the chicken

The serological and secretory immune responses of the chicken to infection with Eimeria tenella were evaluated in terms of various anti-coccidial activities. Serological responses were detected in the forms of precipitating, sporozoite neutralizing, anti-merozoite and anti-schizont antibodies. Similarly, anti-schizont and sporozoite neutralizing activities were found in caecal contents (containing mainly IgA) from infected birds and these also had the capacity to damage second generation merozoites. Moreover, the functional importance of IgA could be implied from the substantial predominance of IgA synthesizing cells in the intestinal immunocyte response as revealed by immunohistology. This was reflected in the immunoglobulin profile of caecal contents, for primary and secondary infection resulted in elevated levels of IgA whilst IgG and IgM generally remained extremely low or were usually undetectable. Taken with the well established lack of correlation between serum antibody and protection, these results suggest that the intestinal secretory IgA system plays an essential role in the protective immune response to E. tenella.

Characterization and localization of secretory component in the chicken

A component found free in intestinal contents and caecal contents of conventional and germ-free chickens (lacking IgA producing cells) was found to have similar characteristics to mammalian secretory component (SC). Free secretory component (FSC) showed a classic reaction of partial identity with secretory IgA (SIgA) from bile, intestinal contents and cystic oviduct fluid. Furthermore, there was demonstrable cross-reactivity between FSC and a low molecular weight component released from SIgA by mild reductive dissociation, confirming the presence of a disulphide-linked accessory polypeptide chain. Fractionation of serum IgA revealed two molecular classes of IgA, a high molecular weight 15S IgA which possessed SC and could not be differentiated antigenically from SIgA and a low molecular weight 7S IgA which showed a reaction of partial identity with 15S IgA and non-identity with FSC. Fluorescent localization of SC in young germ-free chicks demonstrated its presence in the supranuclear golgi zone, apical cytoplasm and basement membrane of crypt epithelial cells. It is concluded that the characteristics of chicken SIgA are closely aligned with those of its mammalian counterpart and are consistent with a system in which SIgA is the wynthetic product of two distinct cells, final assembly occurring in the crypt epithelium.

The role of oral immunisation in stimulating Escherichia coli antibody of the IgM class in porcine colostrum

Oral immunisation with Escherichia coli polysaccharide antigens provided a primary antigenic stimulus which facilitated the production of humoral IgM antibody following a single parenteral antigen dose. The peak antibody response of preparturient sows was manipulated to coincide with the period of colostrum formation so that high levels of IgM antibody were made available for neonatal defence. The characteristics of the immune response remained unchanged on reintroduction of the immunisation schedule for a second gestation period.

Antibody mechanisms implicated in digestive disturbances following ingestion of soya protein in calves and piglets

Serum antibody responses to ingested aqueous alcohol-extracted soya proteins were studied in thirty-six pre-ruminant calves. Characterization of this antibody showed it to be predominantly a complement-fixing IgG1 preciptin. No evidence of tolerance was seen; previously sensitized calves responded to reintroduction of a soya diet with marked increases in antibody levels. The soya antigen was shown to be resistant to proteolysis and, to a lesser degree, to the microbial action of rumen fluid. Biopsy studies showed that the feeding of soya protein resulted in morphological disturbances to the villi and lamina propria of the intestine. Physiological studies by Thirty-Vella loop perfusion in the pig showed that soya protein solutions resulted in significant inhibition of flow rates. The effect was only observed after previous sensitization with the soya antigen. This study shows the necessity of applying immunological criteria to the quality control of soya bean processing in order to ensure that the sensitizing agent is eliminated and the nutritional qualities of soya protein concentrates are optimized.

Immunological aspects of cell membrane adhesion demonstrated by porcine enteropathogenic Escherichia coli

The K88ab antigen of porcine enteropathogenic strains of Escherichia coli exhibited specific affinity for the chicken erythrocyte membrane which correlated with its adhesion characteristics for piglet enterocytes. Thus the chicken erythrocyte provided a useful model for defining the underlying mechanisms of interaction between K88 bearing E. coli and host cell membranes.

This affinity of enteropathogenic E. coli for chicken erythrocytes and piglet enterocytes has been used in an investigation of the role of antibody against the a, b and c determinants of K88 in blocking microbial adhesion to cell membranes. Antisera raised against K88ab and K88ac inhibited the adhesion of both K88ab and K88ac bearing organisms to the microvilli of piglet enterocytes. Antisera specific for the K88a determinant also blocked adhesion of both K88 organisms to the enterocyte indicating the potential of a broad spectrum of activity against porcine enteropathogens. Antibodies against K88b and K88c determinants showed appropriate selectivity for homologous strains.

The selectivity of antibodies specific for the b and c determinants of K88 was also apparent in the chicken erythrocyte haemagglutination inhibition (HI) assay. However, only low inhibitory activity was demonstrated by anti-K88a sera indicating that the specificity of adhesion of K88ab to chicken erythrocytes does not reside in this determinant.

Elimination of Escherichia coli K88 adhesion determinant by antibody in porcine gut and mammary secretions following oral immunization

1) Although virulence of enteropathogenic E. coli in the pig is essentially associated with the K88 adhesion determinant, protection of the neonate and weanling is not necessarily dependent upon antibodies to this surface antigen. 2) Modification of the surface antigenic characteristics of enteropathogens occurs in the presence of antibody, suggesting an immune mechanism of induced loss of the genetic elements responsible for the synthesis of K88. 3) Antibodies directed against the K88 antigen do not seem to participate in the elimination of the K88 antigen. These observations provide a new concept that antibody mediated mechanisms of host defense include elimination of virulence determinants, a feature vital to maintaining the balance of the host pathogen relationship favorable to the host.

Uptake of maternal antibody by the neonatal pig following intramuscular and intramammary vaccination of the preparturient sow

Administration of heat inactivated Escherichia coli antigens by intramuscular and intramammary routes induced elevated antibody levels in sow serum and colostrum, predominantly associated with IgG. Colostral IgG accounted for approximately 80 per cent of the total antibody activity, and there was a similar distribution in the sera of one-day-old piglets. The additional antibody activity was carried almost entirely by IgM following intramuscular injections and was evenly distributed between IgM and IgA following intramammary stimulation. The distribution of antibody activity and all three major immunoglobulin classes in colostrum and milk from individual mammary glands was remarkably uniform. A similar uniformity was inferred for the ingestion and absorption of colostrum by individual piglets as judged by the contents of their blood sera during the neonatal period.

The relative frequencies and distribution of immunoglobulin-bearing cells in the intestinal mucosa of neonatal and weaned pigs and their significance in the development of secretory immunity

A comparative immunohistochemical study has been made of cells containing immunoglobulins IgM; IgA and IgG in the intestines of pigs varying in age from 2 days to 12 weeks. Cells with cytoplasmic IgM appeared in the lamina propria earlier than those containing either IgA or IgG. The duodenum appeared to be the preferred site of infiltration, the numbers of cells occurring in duodenal mucosa were consistently higher than at other levels of intestine irrespective of immunoglobulin class. Igm cells formed the majority of immunoglobulin contained cells in the lamina propria of the small bowel in suckling pigs upto 4 weeks of age. But in the weaned animal the proportion of IgM cells gradually declined with maturity until by the time the pigs were 12 weeks old nearly 90 per cent of the cells contained IgA.

Intestinal immune response to E. coli antigens in the germ-free chicken

The secretory intestinal immune response to live and heat-inactivated E. coli 02 has been studied in young germ-free chicks. A response to live organisms was evident from an infiltration of the intestinal mucosa with IgA and IgM immunoglobulin-producing cells (IPC). Antibody associated with both immunoglobulin classes which was specific for E. coli 02 was demonstrated in saline extracts of contents from the small intestine. Repeated oral immunization with heat-killed E. coli 02 failed to stimulate serum or intestinal antibody. This finding reflected the complete absence of IPC within the intestinal mucosa of these birds. The IPC profile of unimmunized germ-free chicks was identical to that seen in chicks orally immunized with inactivated E. coli. An interesting feature of all gnotobiotic birds was a considerable elevation of serum IgM levels, compared to those of conventional birds, which was unassociated with immunization procedures. Serum IgG and IgA levels in gnotobiotes were much lower than those in the serum of conventional birds of comparable age. Studies on the fate of orally administered antigen using radiolabelled E. coli endotoxin indicated that a proportion remained intact as far down the intestinal tract as the caecum. However, unaccountably high levels of low mol. wt antigen in the faeces suggested degradation, intestinal absorption and subsequent excretion of endotoxin fragments in the urine. The differences between the avian response and that observed in mammals are discussed in relation to the comparative roles of Peyer's patches and the bursa of Fabricius in initiating intestinal immununity.

Significance of immune mechanisms in relation to enteric infections of the gastrointestinal tract in animals

The impact of bacterial colonization on the alimentary tract in early life is reflected in gross changes in morphology. Subsequent health, if not survival, may largely be determined by a continuum of local intestinal immune mechanisms and it is essential for antibody development during the neonatal period to compensate adequately for declining passive maternal antibody. Consequent upon the development of the gut microflora the lamina becomes infiltrated with immunocytes in which the dominant immunoglobulins produced are IgM and IgA. Both immunoglobulins are transported across the epithelium by a process involving membrane-bound vesicles. Germ-free and fistulated pigs and calves are shown to be able to respond to oral immunization with Escherichia coli O somatic antigens during the first week of life. Resistance to infection with enteropathogenic E. coli was significantly enhanced, along with other parameters of nutrition and performance. However, in the young chick, although the intestinal response to infection with E. coli was similar to that in the mammal, no response to E. coli O antigens could be determined on oral administration in germ-free or local intestinal applications in fistulated birds. In the mammalian intestine secretory antibodies participate in the control of pathogenic E. coli by blocking adhesion to the mucosal epithelium, interfering with the elaboration of surface antigens, inhibiting toxins, and facilitating rapid elimination from the alimentary tract by agglutination and bacteriostasis. In consequence fewer enteropathogens are excreted into the environment, an important feature in modern intensive systems of animal production.

Further characterization of IgA in chicken serum and secretions with evidence of a possible analogue of mammalian secretory component

Immunochemical studies of the intestinal secretory immune system of the chicken have led to further characterization of IgA in bile, intestinal contents and serum. A component was detected in late Sephadex G-200 fractions of caecal and intestinal contents which showed partial identity with bile, intestinal and a high molecular weight fraction of serum IgA. This component showed similar sedimentation characteristics to bovine serum albumin in sucrose density gradients, a fast electrophoretic mobility on polyacrylamide gel and is a possible analogue of mammalian secretory component (SC). Fractionation of serum from birds affected with infectious synovitis revealed two moleculare classes of IgA. Comparative double diffusion studies produced a reaction of complete identity between bile IgA and high molecular weight serum IgA (15S) and partial identity with low molecular weight serum IgA (7S), suggesting a lack of an SC determinant on the latter. A spur of partial identity between 15S and 7S serum IgA was also observed. Although no direct structural homology with mammalian or human IgA could be demonstrated by immunological cross-reactivity, the similarities of molecular characteristics, particularly emphasized by the presence of a secretory component, favour a functional analogy between the secretory immune system of the fowl and mammalian species.

Evidence for the secretory transport mechanism of intestinal immunoglobulin. The ultrastructural distribution of IgM

The intracellular localization of IgM in porcine intestinal tissue has been studied by immunoelectron microscopy and immunofluorescence. IgM was demonstrated in vesicles in the cytoplasm of crypt epithelial cells particularly in the supranuclear region. It was also shown in the ergastoplasmic cisternae of plasma cells in the intercryptal lamina propria. The findings are compared with those of a previous similar study on secretory IgA and their implications for possible mechanisms of selective transport are discussed.