Bovine lactogenic immunity against cholera toxin-related enterotoxins and Vibrio cholerae outer membranes.

The newly parturient cow secretes large quantities of immunoglobulin G1, a relatively protease- and heat-resistant immunoglobulin, in its colostrum and milk. This study establishes the feasibility of producing protective colostral immunoglobulins by immunizing pregnant cows with cholera toxin (CT), a CT-related enterotoxin from Escherichia coli, and Vibrio cholerae outer membranes (OMs). The OMs were prepared from bacteria grown under iron-replete or iron-deficient (to simulate the in vivo environment) conditions. Immunoglobulins were purified from the colostrum of newly parturient control and immunized cows. The bovine anti-CT and anti-H-LT (CT-related heat-labile enterotoxin produced by diarrheogenic E. coli strains of human origin) antibodies were quantitated by enzyme-linked immunosorbent assays and by neutralization of toxin activity in both Y-1 adrenal cell and infant rabbit assays. The bovine anti-OM antibodies from both high-iron-grown and low-iron-grown vibrios were assessed by bacterial agglutination and by Western blot (immunoblot) analysis of polyacrylamide gel electrophoresis of high-iron-grown and low-iron-grown OMs. To test their protective effect, immunoglobulin preparations were administered orally in infant feeding formula to 6-day-old rabbits. Anti-CT and anti-OM immunoglobulins elicited statistically significant protection against diarrhea in infant rabbits challenged intraintestinally with virulent cholera vibrios.     

Inhibition of adhesion of S-fimbriated Escherichia coli to buccal epithelial cells by human milk fat globule membrane components: a novel aspect of the protective function of mucins in the nonimmunoglobulin fraction.

We investigated the presence of factors in human milk that inhibit invasion of pathogenic bacteria. The effect of human milk fat globule membrane (HMFGM) components on adhesion of cloned S-fimbriated Escherichia coli to human buccal epithelial cells was analyzed. S fimbriae are a common feature of E. coli strains causing sepsis and meningitis in newborns and are bound to epithelia via sialyl-(alpha-2-3)galactoside structures. Human milk fat globules (HMFG) could be agglutinated by the above-mentioned bacteria. Agglutination could be inhibited by fetuin, human glycophorin, and alpha 1-acid glycoprotein. In addition, pretreatment of HMFG with Vibrio cholerae neuraminidase markedly reduced bacterium-induced agglutinations, indicating the involvement of neuraminic acid-containing glycoproteins. In contrast, lipid droplets of infant formula or artificial lipid emulsions (Intralipid) could not be agglutinated. HMFG were present in stools of breast-fed neonates as shown by indirect immunofluorescence staining with a monoclonal antibody directed against carbohydrate residues present on HMFGM. These HMFG could be agglutinated by bacteria. HMFG inhibited E. coli adhesion to buccal epithelial cells. To further characterize relevant E. coli binding structures, HMFGM components were separated by gel chromatography. The mucin fraction showed the most pronounced inhibitory effect on adhesion of S-fimbriated E. coli to human buccal epithelial cells. Our data suggest that HMFG inhibit bacterial adhesion in the entire intestine and thereby may provide protection against bacterial infection.     

New adhesive factor (antigen 8786) on a human enterotoxigenic Escherichia coli O117:H4 strain isolated in Africa.

An enterotoxigenic Escherichia coli strain, E. coli 8786, of serotype O117:H4 produced only heat-stable enterotoxin and gave mannose-resistant hemagglutination with human and bovine erythrocytes. The strain adhered to the brush border of human enterocytes and to enterocytelike cell line Caco-2. Adhesion inhibition assays using Caco-2 cells with different adhesive factor extracts showed that the adhesive factor of E. coli 8786 is different from colonization factor antigen I (CFA/I). CFA/II, CFA/III of Darfeuille et al. (A. Darfeuille, B. Lafeuille, B. Joly, and R. Cluzel, Ann. Microbiol. Inst. Pasteur 134A:53-64, 1983), CS6, and antigen 2230. A bacterial surface protein, designated antigen 8786, with a molecular mass of 16,300 Da was responsible for the adhesion to intestinal cells. It was immunologically different from previously described adhesive factors as determined by immunoblotting. Antigen 8786 was detected on the bacterial cell surface and appeared to be nonfimbrial. NH2-terminal analysis of antigen 8786 showed no homology with the previously described adhesive factors. Nevertheless, antigen 8786 is closely related to the NH2-terminal sequence of Salmonella enteritidis fimbrin. A hybridization experiment using a synthetic oligonucleotide probe based on the NH2-terminal amino acid sequence of antigen 8786 revealed that the coding region was located on a 70-MDa plasmid.     

Protection by milk immunoglobulin concentrate against oral challenge with enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli is a common cause of traveler's diarrhea. Prophylaxis against traveler's diarrhea has been associated with side effects from bismuth subsalicylate and the development of resistance to antimicrobial agents. We undertook a double-blind controlled trial in which a bovine milk immunoglobulin concentrate with high titers of antibodies against enterotoxigenic E. coli was used as prophylaxis against E. coli challenge in volunteers. Lyophilized milk immunoglobulins were prepared from the colostrum of cows immunized with several enterotoxigenic E. coli serotypes and fimbria types, E. coli heat-labile enterotoxin, and cholera toxin. As a control, an immunoglobulin concentrate with no anti-E. coli activity was prepared. Ten volunteers received buffered immunoglobulin concentrate against enterotoxigenic E. coli, and 10 received the control immunoglobulin concentrate, dissolved in water, three times a day. No side effects were observed. On the third day of immunoglobulin prophylaxis, the volunteers were given 10(9) colony-forming units of enterotoxigenic E. coli H10407 (O78:H11). This strain produces colonization factor antigen I and heat-labile and heat-stable enterotoxins. None of the 10 volunteers receiving the immunoglobulin concentrate against E. coli had diarrhea, but 9 of the 10 controls did (P less than 0.0001). All volunteers excreted E. coli H10407. We conclude from these preliminary results that milk immunoglobulin concentrate may be an effective prophylaxis against traveler's diarrhea.     

Effect of fractions of Ethiopian And Norwegian colostrum on rotavirus and Escherichia coli heat-labile enterotoxin.

Samples of colostrum from both Ethiopian and Norwegian women contained antirotavirus activities of immunoglobulin and non-immunoglobulin nature. No significant differences in rotavirus immunoglobulin A or in rotavirus-inhibiting activity were found between samples from the two countries. The non-immunoglobulin inhibitory activity was trypsin sensitive and heat stable (100 degrees C for 10 min). Escherichia coli heat-labile enterotoxin antibodies were measured in the colostrum samples by enzyme-linked immunosorbent assay. No E. coli enterotoxin-specific immunoglobulin A was detected, possibly due to the high background caused by the nonspecific adsorption of immunoglobulin A to the enzyme-linked immunosorbent assay plates in the absence of toxin. A total of 5 of 15 Ethiopian colostrum samples and 0 of 11 Norwegian colostrum samples neutralized the effect of E. coli heat-labile enterotoxin on YI adrenal cells. Both the Ethiopian and the Norwegian colostrum samples contained a non-immunoglobulin enterotoxin-inhibitory activity when the toxin was measured by enzyme-linked immunosorbent assay. This inhibitory activity was not trypsin sensitive, and extraction by chloroform-methanol indicated that the inhibitor was of a lipid nature.     

Adaptation of the staphylococcal coagglutination technique for detection of heat-labile enterotoxin of Escherichia coli.

Protein A-containing staphylococci coated with specific antiserum were tested for heat-labile enterotoxin of Escherichia coli. The immunological cross-reactivity of E. coli heat-labile enterotoxin with Vibrio cholerae toxin (choleragen) was the basis for sensitizing stabilized suspensions of the Cowan I strain of Staphylococcus aureus with anticholeragen. Unconcentrated culture supernatant fluid containing E. coli heat-labile enterotoxin produced macroscopic agglutination when mixed with sensitized staphylococci in capillary tubes. A total of 15 toxigenic and 61 nontoxigenic isolates were tested by the staphylococcal coagglutination technique in a coded fashion and found to be in agreement with previous results of the Chinese hamster ovary cell assay and the passive immune hemolysis test. The staphylococcal coagglutination technique is simple, relatively inexpensive to perform, and requires the immunoglobulin fraction of anticholeragen as the only specific reagent. The staphylococcal coagglutination technique appears to have potential for routine use in diagnostic microbiology laboratories.     

Monoclonal antibodies against enterotoxigenic Escherichia coli colonization factor antigen I (CFA/I) that cross-react immunologically with heterologous CFAs.

Enterotoxigenic Escherichia coli binds to enterocytes in the small intestine by means of antigenically distinct colonization factors (CFs), usually termed colonization factor antigens (CFAs), coli surface antigens (CS), or putative colonization factor antigens (PCFs). To explore the immunological relationship between different CFs, we dissociated CFA/I fimbriae into subunits and produced monoclonal antibodies (MAbs) against these subunits. We selected three MAbs that cross-reacted immunologically with a number of different, whole purified CFs in a dot blot test and with the corresponding subunits in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. One of the MAbs, i.e., subunit CFA/I 17:8 (S-CFA/I 17:8), reacted more strongly with subunits of CFA/I than with whole purified fimbriae. This MAb cross-reacted with whole purified fimbriae and subunits of CS4, PCFO166, CS1, and CS2. Moreover, it bound strongly to a peptide of 25 amino acids corresponding to the N-terminal end of CFA/I. The other two MAbs, i.e., S-CFA/I 5:6 and S-CFA/I 8:11, cross-reacted with CS1, CS2, CS4, PCFO166, and CS17 fimbriae but reacted only slightly or not at all with the CFA/I peptide. MAbs S-CFA/I 17:8 and S-CFA/I 5:6 were shown to inhibit hemagglutination by bacterial strains that express either CFA/I, CS1, or CS4. In addition, the binding of enterotoxigenic E. coli strains expressing CFA/I, CS2, CS4, and PCFO166 to enterocyte-like cell-line Caco-2 was inhibited by both MAbs. These results show that several antigenically different CFs have common epitopes and that among these at least one is located in the N-terminal end of the subunit protein. Moreover, antibodies against the common epitopes seem to block binding of the bacterial strains that express different CFs to both erythrocytes and Caco-2 cells.     

Interaction of Escherichia coli with Different Fimbriae and Polymorphonuclear Leukocytes

The effects of Escherichia coli strains with various fimbriae on bacteria-polymorphonuclear leukocyte (PMN) interactions were studied. Strains of E. coli were cultivated at 37 degrees C to express and at 18 degrees C to suppress the formation of fimbriae. The presence of fimbriae was confirmed by electron microscopic studies and hemagglutination and salt aggregation tests. Fimbriated E. coli strains were more readily PMN associated than the nonfimbriated strains in the absence of opsonins, confirming the results of previous studies. However, the PMN chemiluminescence (CL) induced by the various strains in the absence of serum opsonins depended on the type of fimbriae they expressed. Strains with type 1 fimbriae expressing mannose-sensitive hemagglutination induced 5 to 15 times more CL than the same strains grown at 18 degrees C, i.e., not expressing this type of fimbriae. For strains showing mannose-resistant hemagglutination, the differences between fimbriated and nonfimbriated variants of the same strains grown at 37 and 18 degrees C, respectively, were less pronounced. Analysis of enterotoxigenic strains expressing colonization factor antigen I (CFA/I) fimbriae showed that these induced only 25 to 33% of the CL induced by the same E. coli strains not expressing CFA/I, whereas enterotoxigenic strains expressing CFA/II fimbriae induced 100 to 200% of the CL induced by the nonfimbriated variants. Although less CL was induced by bacteria with CFA/I fimbriae than by nonfimbriated variants, this situation was reversed when the microorganisms were opsonized. Thus, CFA/I fimbriae, while enhancing adhesion to cells, induce less activation of PMN-killing mechanisms in a serum-free environment. These findings may be relevant for the virulence in certain body sites, since CFA/I fimbriae, while facilitating adhesiveness, may protect the bacteria from PMN killing. Our findings indicate that PMN interactions with fimbriated E. coli in the host defense may be complex. Certain fimbriae may indeed be advantageous to the bacteria, enabling them to interact with PMNs without activating the bactericidal oxidative metabolism.     

Rapid visual detection of Escherichia coli and Vibrio cholerae Heat-labile enterotoxins by nitrocellulose enzyme-linked immunosorbent assay

A modification of the enzyme-linked immunosorbent assay for a sensitive and rapid visual detection of heat-labile enterotoxins from Escherichia coli and Vibrio cholerae is described. Small amounts of bacterial supernatant fluids are bound to nitrocellulose filters which are used as sorbents in the nitrocellulose enzyme-linked immunosorbent assay. The test is based on the immunological similarity between V. cholerae and E. coli heat-labile enterotoxins. Six isolates of V. cholerae and 48 isolates of E. coli were examined for heat-labile enterotoxins by the nitrocellulose enzyme-linked immunosorbent assay and the Vero cell bioassay. With some strains, the nitrocellulose enzyme-linked immunosorbent assay was found to be more sensitive for detection of E. coli heat-labile enterotoxin than the Vero cell test. A similar result was obtained by endpoint titration of heat-labile enterotoxin-positive E. coli H10407 culture fluid in both assays. The sensitivity of the nitrocellulose enzyme-linked immunosorbent assay for the detection of purified cholera toxin was at a total level of 1 ng, which is a good result when compared with other serological assays.     

Bacteriostatic effect of human milk on Escherichia coli: the role of IgA.

Previous work showed that lactoferrin was involved in the bacteriostatic effect of human milk on E. coli O111. Further experiments on the general nature of this effect have been carried out together with an examination of the role of IgA. Milk samples from different individuals differed in their ability to produce bacteriostasis of three pathogenic serotypes of E. coli. The bacteriostatic effect was stable to heating at 60 degrees for 35 min. As in the case of serum, the bacterial iron transporting compound, enterochelin, abolished the bacteriostatic effect of human milk. IgA was isolated from the milk samples in two forms which appeared to differ in molecular weight. When mixed with lactoferrin, some of these fractions induced bacteriostasis which could be reversed by Fe3+. Since the fractions were devoid of bactericidal activity in the presence of complement it appeared that IgA was involved in the induction of bacteriostasis. It was also concluded that the mechanism of bacteriostasis was identical in serum and milk. These results are discussed in relation to both the protective effect of feeding colostrum and milk and also the resistance of the adult gastrointestinal tract to infection.     

Immunization of swine with heat-stable Escherichia coli enterotoxin coupled to a carrier protein does not protect suckling pigs against an Escherichia coli strain that produces heat-stable enterotoxin.

Pregnant swine were immunized parenterally with purified heat-stable Escherichia coli enterotoxin that was made antigenic by coupling it to bovine immunoglobulin G. Immunized swine had high titers of antitoxin in serum and colostrum as measured by radioimmunoassay. However, the heat-stable enterotoxin neutralizing titers of the serum and colostrum from immunized swine were comparatively low. Newborn pigs suckling their immunized dams were not protected against challenge with porcine enterotoxigenic E. coli that produce heat-stable toxin but do not produce heat-labile toxin.     

Identification of a new fimbrial structure in enterotoxigenic Escherichia coli (ETEC) serotype O148:H28 which adheres to human intestinal mucosa: a potentially new human ETEC colonization factor.

Three important fimbrial colonization factor antigens (CFAs) designated CFA/I, CFA/II, and E8775 were identified originally in some human enterotoxigenic Escherichia coli (ETEC) strains because of their mannose-resistant hemagglutination properties. To identify CFA, in strains lacking mannose-resistant hemagglutination properties we exploited the ability of human ETEC strains to adhere to human proximal small intestinal mucosa. ETEC strain B7A (O148:H28) was selected for study because it belongs to an epidemiologically important serotype and does not produce a known CFA, and yet it is known to be pathogenic and cause diarrheal disease in human volunteers. Results of an human enterocyte adhesion assay indicated that some bacteria in cultures of B7A produced adhesive factors. To select for such bacteria, cultured human duodenal mucosal biopsy samples were infected with B7A for up to 12 h, after which time a large percentage of the mucosal surface became colonized by bacteria. A new fimbrial structure morphologically distinct from CFA/I, CFA/II, and E8775 fimbriae and consisting of curly fibrils (approximately 3 nm in diameter) was readily identified when bacteria were subcultured from the mucosa and examined by electron microscopy. Identical fimbriae were produced by ETEC strain 1782-77 of the same serotype. Identification of these fimbriae only on bacteria subcultured from human intestinal mucosa strongly suggests that they promote mucosal adhesion of ETEC serotype O148:H28 and thus represent a potentially new human ETEC CFA.     

Bacteriostatic effect of human milk and bovine colostrum on Escherichia coli: importance of bicarbonate.

At pH 7.4 and in the presence of NaHCO3, human milk and bovine colostrum inhibited the growth of Escherichia coli O111. Adding sufficient iron to saturate the iron-binding capacity of the lactoferrin present in the milk or colostrum prevented bacteriostasis. At pH 6.8 neither molk nor colostrum inhibited E. coli 0111. Adjusting the pH to 7.4 with NaHCO3 resulted in the development of bacteriostatic activity. Adjusting the pH to 7.4 with NaOH was ineffective. Dialyzed colostrum and milk inhibited bacterial growth at pH 6.8 in the absence of added NaHCO3; addition of citrate or iron abolished bacteriostasis. The chromatographic elution profile of tyrosyl-transfer ribonucleic acid (tRNA) from iron-replete E. coli differs significantly from that of tyrosyl-tRNA from iron-deficient organisms. Examination of the elution profile tyrosyl-tRNA from E. coli 0111 growing in colostrum without added NaHCO3 showed that such bacteria were fully replete in iron. The nature of the elution profile of tyrosyl-tRNA also showed that iron was freely available to the bacteria when citrate was added to dialyzed colostrum but not available in its absence, even at pH 6.8. Results support the idea that the bacteriostatic action of milk and colostrum, due to the combined action of antibody and lactoferrin, depends on the addition of bicarbonate to counteract the iron-mobilizing effect of the citrate normally present in these secretions.     

Purification and characterization of the CFA/I antigen of enterotoxigenic Escherichia coli.

The fimbral colonization factor antigen CFA/I of enterotoxigenic Escherichia coli was purified and characterized. The initial purification step was release of these fimbriae from the bacterial cells by homogenization with a Waring blender. Common fimbriae and flagellar antigen were avoided by careful control of growth conditions and the use of a nonmotile (H-) mutant of the prototype strain H-10407 (O78:H11). The essential purification steps were membrane filtration (Millipore Corp.), ammonium sulfate fractionation, and negative diethylaminoethyl-Sephadex column chromatography. Yields were approximately 4.0 mg of CFA/I protein per g (wet weight) of bacteria. Purified CFA/I is a fimbrial molecule 7.0 nm in diameter and has an average molecular weight of 1.6 X 10(6), as determined by sedimentation equilibrium. CFA/I is a polymer of identical subunits of molecular weight 23,800 with an N-terminal valine, 37% hydrophobic amino acid residues, and 11 residues of proline per mol. The purified antigen retains its morphology, antigenicity, and biological activity. Purified antigen retains its morphology, antigenicity, and biological activity. Purified CFA/I exhibits mannose-resistant hemagglutination of human group A, bovine, and chicken erythrocytes, as do CFA/I-positive bacteria. This was demonstrated by sensitizing latex microbeads with the purified antigen since cell-free CFA/I fimbriae do not hemagglutinate erythrocytes. Thus, CFA/I detached from the bacteria are monovalent; however, purified CFA/I antigen retains an affinity for the epithelial cells of rabbit small intestine and blocks adhesion of CFA/I-positive bacteria. These results demonstrate that purified CFA/I is a good candidate for use in an oral vaccine for immunoprotection against diarrhea caused by CFA/I-positive enterotoxigenic E. coli.     

Reduction of reactivity of Escherichia coli enterotoxins by intestinal mucosal components.

Incubation studies involving rabbit and piglet small intestinal mucosal components and Escherichia coli and Vibrio cholerae enterotoxins were conducted at 37 and 4 degrees C. Mucosal homogenate cytosol from rabbits did not significantly alter the reactivities of either cholera enterotoxin (CT) or E. coli labile enterotoxin (LT). However, mucosal homogenate cytosol from piglets was capable of neutralizing LT, though it had no effect on E. coli stable enterotoxin. LT became bound to piglet and rabbit microvillous membranes at 4 degrees C in the presence of a protective protein. In rabbits, the binding of LT was not dependent upon an intact glycocalyx or free unbound CT-receptors, although some binding was apparently associated with the glycocalyx and CT-receptors. These results indicated the presence of two different LT-receptors in microvillous membranes one being associated with the membrane proper and the other with the glycocalyx. Stable enterotoxin did not bind to in vitro preparations of piglet mucosal components, which is evidence for a different mechanism for inducing intestinal secretion.     

Synergistic protective effect of antibodies against Escherichia coli enterotoxin and colonization factor antigens.

We studied the ability of antisera against different Escherichia coli surface antigens, both alone and in combination with anti-enterotoxin, to decrease fluid secretion induced by intestinal challenge with enterotoxigenic E. coli in rabbits. Antiserum against lipopolysaccharide protected significantly against O group homologous bacteria. Monospecific antisera against pilus-associated colonization factor antigens CFA/I and CFA/II were also effective, giving highly significant protection against enterotoxigenic E. coli strains bearing the corresponding colonization factor antigens. Protection was also observed with Fab fragments of the CFA/I antibodies. Addition of the anti-lipopolysaccharide serum to a protective antiserum against purified heat-labile enterotoxin resulted in an antisecretory effect which slightly exceeded the sum of the effects obtained with each preparation alone. The combination of antiserum against CFA/I or CFA/II with anti-enterotoxin gave protection that equaled the product of the effects obtained with each antiserum alone; i.e. the antisera cooperated synergistically.     

Detection of enterotoxigenic Escherichia coli colonization factor antigen I in stool specimens by an enzyme-linked immunosorbent assay.

An enzyme-linked immunosorbent assay (ELISA) was employed to detect and quantitate the fimbrial colonization factor antigen (CFA/I) of enterotoxigenic Escherichia coli in stool specimens obtained from adult cases of diarrhea in which CFA/I-positive E. coli was the known causative agent. The inhibition method, or blocking technique, was used. In this method, a standardized dilution of human anti-CFA/I serum was preincubated with dilutions of stool extract before transfer to CFA/I-coated microtiter plate wells, and then ELISA was performed with alkaline phosphatase-conjugated anti-human immunoglobulin. CFA/I purified from E. coli strain H-10407 (O78:H11) was used. Acute-phase diarrheal stool specimens were found to contain approximately 3.0 mg of antigen (mean value) per g stool, whereas control (CFA/I-negative) specimens contained insignificant amounts (less than 0.03 mg/g) of antigen. Also, CFA/I was detected in culture fluids of CFA/I positive enterotoxigenic E. coli belonging to a variety of serotypes and was undetectable in similar preparations from P-strains (spontaneous CFA/I-negative derivatives) of the same test cultures. Equivalent results were obtained in ELISA tests by using bacterial cells taken from isolated colonies grown on CFA agar. These results indicate that the ELISA technique will be useful for the diagnosis of diarrhea caused by CFA/I-positive enterotoxigenic E. coli.     

Microtiter solid-phase radioimmunoassay for detection of Escherichia coli heat-labile enterotoxin.

The development of a microtiter solid-phase radioimmunoassay for the detection of Vibrio cholerae enterotoxin and heat-labile Escherichia coli enterotoxin is described. The test is based on the immunological similarity between V. cholerae toxin and E. coli heat-labile toxin. The assay is easy to perform, quantitative, and at least as sensitive and specific as the Y-1 adrenal cell system.     

New fimbrial antigenic type (E8775) that may represent a colonization factor in enterotoxigenic Escherichia coli in humans.

An enterotoxigenic strain of Escherichia coli O25:H42 (strain E8775), isolated from a patient in Bangladesh with diarrhea, caused mannose-resistant hemagglutination (MRHA) of human and bovine erythrocytes. The strain did not show slide agglutination or immunodiffusion precipitin lines with antiserum specific for the colonization factor antigen CFA/I or CFA/II. A variant E. coli strain, E8775-B, did not cause MRHA or produce enterotoxin. Electron microscopy revealed the presence of fimbriae on the surface of strain E8775 but not strain E8775-B. When strain E8775 was grown at 22 degrees C, it became MRHA negative and fimbriae were absent. An antiserum prepared against strain E8775 was absorbed with strain E8775-B to make an antiserum specific for the fimbrial antigen. Using this absorbed antiserum, we found the fimbrial antigen in 48 of 742 enterotoxigenic E. coli strains. The 48 strains belonged to serogroups O25, O115, and O167. It is suggested by analogy to the properties of previously described colonization factors that these fimbriae may play a part in the colonization of the intestinal epithelium.     

Escherichia coli-associated porcine neonatal diarrhea: antibacterial activities of colostrum from genetically susceptible and resistant sows.

Antibacterial properties of colostrum from genetically resistant and susceptible sows in a herd in which only the susceptible sows had acquired natural immunity to K88-positive Escherichia coli have been investigated. Significant differences in antiadhesive and opsonic activities occurred. Colostrum from susceptible sows inhibited the binding of 125I-labeled K88 antigen to brush borders significantly better than did the colostrum from resistant dams. Colostrum from susceptible dams effected more efficient in vitro opsonic phagocytosis and killing of K88 E. coli than did colostrum from resistant dams. Differences in bactericidal properties of colostrum between the two groups of pigs were not significant. Fractionation of colostrum from susceptible dams by gel filtration and ion-exchange chromatography revealed that the fractions rich in immunoglobulin M had the highest opsonic activity, whereas those containing predominantly immunoglobulins G and A were of lower activity.