Bovine antibody against Streptococcus agalactiae, type Ia, produced by preparturient intramammary and systemic vaccination.

Four pregnant heifers were immunized by the intramammary route with killed or live Streptococcus agalactiae vaccine, and a 5th heifer was vaccinated by the intramuscular route with killed vaccine. Antibody in the colostrum from vaccinated and non-vaccinated glands was compared. Antibacterial glands was compared. Antibacterial antibody titers of the 4 immunoglobulin classes were determined by indirect fluorescent antibody assay. Although the content of immunoglobulin G1 (IgG1), IgG2, and IgM in the colostrum from the vaccinated glands was not substantially different from the nonvaccinated glands, IgA content was considerably greater in the former. Antibody specific to S agalactiae was isolated from all colostrum samples. The mouse passive protection test and Ouchterlony analysis were used to demonstrate the presence of type-specific antibody to Ia strain used for vaccination. The passive mouse protection test also was useful to compare the protective capacity of specific S agalactiae, type Ia, antibodies of immunoglobulin classes IgG, IgM, and IgA. Increased protective capacity of IgM and IgA over IgG1, on a weight basis, was demonstrated. The present study indicates that S agalactiae preparations, when introduced into the mammary gland, can give rise to local antibody synthesis in the vaccinated glands.     

Transfer of maternal antibody against group A rotavirus from sows to piglets and serological responses following natural infection

An enzyme-linked immunosorbent assay (ELISA) was developed for the measurement of antirotaviral antibody in sera and faeces from pigs and used to study the dynamics of antirotaviral antibody responses in three cohorts of pigs. Piglets acquired antirotaviral antibody by sucking their dams soon after birth. Antirotaviral antibodies of IgA and IgG classes were detected in both colostrum and milk of all sows tested but IgM class antibodies were not. The antibody levels in colostrum were eight to 32 times higher than those in milk which was collected 18 days post partum. The levels of antibody in piglets' sera were comparable to those in colostrum but declined quickly to low levels by one month old. Maternal antibody was also detected in the faeces of piglets up to 18 days old. Natural rotavirus infection occurred in each of these cohorts when the geometric mean ELISA titres of maternal antibody in their sera declined to 1/1600 (by days 21, 25 and 30 for cohorts 1, 2 and 3, respectively). However, a positive correlation was not obtained between the levels of antirotaviral antibody and protection in individual litters within each of the cohort groups. In each of the cohorts, rotavirus infection usually occurred in one or two piglets first and then spread to other piglets in the same cohort. It is therefore suggested that maternally derived antibody is protective against rotavirus infection in piglets only for the first one or two weeks. Following natural infection with rotavirus, increases in serum antibodies were detected in two of the three cohorts by 20 to 30 days after the average time of onset of faecal shedding of virus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Studies on immunoglobulins and trypsin inhibitor in colostrum and milk from sows and in serum of their piglets.

The concentrations of IgG, IgM, IgA and the specific sow colostrum trypsin inhibitor (SCTI) were measured by radial immunodiffusion in colostrum and milk samples from sows and in serum samples from their offspring during the suckling period. A clear time dependence was found for all the measured variates in both whey and serum. Statistically significant positive correlations were found between, on the one hand, concentrations of IgG and IgA, but not IgM, in sera from 39 suckling piglets 1 and 3 days old, and, on the other hand, concentrations of the same immunoglobulins and of the trypsin inhibitor in maternal colostrum (n = 7). Multiple regression analyses showed that at day 1 and day 3 the levels of both IgG and IgA in serum samples from the suckling piglets were positively influenced by both the SCTI and the IgG or IgA contents in maternal colostrum.     

Change of antibody levels to ferritin in the sera of foals after birth: Possible passive transfer of maternal anti‐ferritin autoantibody via colostrum and age‐related anti‐ferritin autoantibody production

Antibody (immunoglobulin G (IgG), IgM or IgA) levels relative to ferritin in six foal sera (three male and three female) after birth (day 0 and 2, 6, 10, 20, 28, 36, 40, 52 and 56 weeks of age) were semi‐quantitatively measured with normalization with antibody activity to ferritin in one adult horse serum. After addition of horse spleen ferritin to the serum sample, the complex formed between antibodies to ferritin in the serum and ferritin was co‐immunoprecipitated using antibody to horse spleen ferritin. Antibody classes of the co‐immnoprecipitate were detected with antibodies specific for horse IgG, IgM or IgA heavy chain. Six adult horse serum samples were found to have ferritin‐binding activities in all immunoglobulin classes examined. Although ferritin antibody activities (IgG, IgM and IgA) were scant in the foal sera before sucking colostrum (day 0), their activities increased at 2 weeks of age. IgG antibodies showed a biphasic response and IgM antibody activity increased up to 40 weeks of age. Antibody (IgG, IgM and IgA) activities to ferritin in three colostrum samples were significantly higher than in adult horse serum samples. These results demonstrate that antibody to ferritin in foal serum is derived from colostrum after birth and is produced thereafter.     

Antigenicity of structural components from porcine transmissible gastroenteritis virus

Pregnant sows were inoculated with inactivated transmissible gastroenteritis virus and with preparations of virus surface projections and subviral particles derived by detergent treatment of the virus. Neutralising antibody was demonstrated in serum and colostrum from animals that received whole virus or preparations of surface projections whereas subviral particles failed to stimulate neutralising antibody formation. Similar results were obtained with serum from rabbits inoculated with whole virus and structural components. All three preparations stimulated the formation of agglutinating antibodies, as demonstrated by sedimentation analysis and filtration studies with radiolabelled virus.The immunoglobulin classes responsible for neutralising antibody activity in sows inoculated by the intramammary route were examined. In each case where the immunoglobulin class was determined, IgG was found. One sow that received surface projections also had IgA with neutralising activity in her colostrum. In contrast, infection of sows with live whole virus resulted in neutralising antibody of the IgG, IgM and IgA classes.     

The effect of intramuscular and intramammary vaccination of cows on antibody levels and resistance to intramammary infection by Staphylococcus aureus.

Cows were vaccinated simultaneously by the intramuscular and intramammary route with formolised Staphylococcus aureus cells of strains BB, Mexi and 3528. Vaccination resulted in slight increases in serum agglutinin titres, but the levels of the agglutinins in milk and colostrum were not higher in vaccinated cows than in the unvaccinated controls. Vaccination did not result in higher levels of IgM, IgG1, IgG2 or IgA immunoglobulins in serum, colostrum or milk as compared with controls. Vaccinated cows, particularly those in which strain 3528 was used, showed some resistance to infection following challenge with low numbers of viable S aureus Mexi, but there was no resistance to infection when similar numbers of the virulent BB strain were used for challenge. It is concluded that vaccination is unlikely to prevent infection of the bovine udder by S aureus.     

Quantification of bovine IgG, IgM and IgA antibodies to Clostridium perfringens B-toxin by enzyme immunoassay I. Preparturient immunization for enhancement of passive transfer of immunity

A quantitative competitive binding "triple-sandwich" enzyme immunoassay was developed and used to evaluated pathogen/class-specific antibody responses in Holstein-Friesian cows vaccinated against Clostridium perfringens B-toxin. Vaccination of cows at six weeks and again at two weeks prepartum increased pathogen-specific IgG levels in each dam's colostrum and respective calf's serum. Pathogen-specific IgG and IgM concentrations in dams' sera and colostra were related to subsequent pathogen-specific IgG and IgM neonatal sera concentrations. Only pathogen-specific IgA in dams' colostra was correlated to neonatal levels, possibly owing to a different origin and role of this immunoglobulin class. All class-specific colostral immunoglobulin levels were related to subsequent neonatal concentrations. Isotypic antibody responses against C. perfringens B-toxin were found with pathogen-specific IgM predominant in dams' sera and pathogen-specific IgA predominant in colostra and neonatal sera.     

The absorption of colostral immunoglobulins in newborn piglets. III. Influence of the duration of colostrum administration

The gastrointestinal tract of newborn piglets is permeable for intact immunoglobulins ingested with the colostrum. The duration of this passage was investigated by administering hourly rations of 25 ml of either porcine or bovine colostrum for 6, 12, 18 or 24 hrs after birth. The plasma concentrations of the subclasses porcine IgG, IgM and IgA or bovine IgG1, IgG2, IgM and IgA were determined at 12, 18 and 24 hrs after birth and on days 3 and 6. Feeding periods of 6 hrs resulted in plasma Ig levels of the same order of magnitude as observed in natural rearing. These levels were not substantially increased after prolonged feeding. The 6% gain from 6 to 12 feedings seen with porcine colostrum as compared with a gain of 24% for bovine colostrum points at an earlier closure of the intestinal wall for the species-specific proteins. There was no further increase of Ig permeation after 12 hourly feedings. Growth performances and losses were identical in all groups.     

Maternal-neonatal immunoregulation: suppression of de novo synthesis of IgG and IgA, but not IgM, in neonatal pigs by bovine colostrum, is lost upon storage

Fifty-four neonatal pigs were allotted to 4 groups and reared in an electrically controlled automatic feeding device (autosow). Each group was reared on a different pool of bovine colostrum: fresh, stored 1 month, stored 6 months, and stored 8 years. Bovine and porcine immunoglobulins in the sera of these pigs, and in a group of conventionally reared pigs, were measured periodically during the first 42 days after birth. The maximal concentration of absorbed bovine immunoglobulin was reached between 12 and 18 hours and equaled or exceeded the amount of porcine immunoglobulin absorbed by the conventionally reared pigs. Large differences in the concentrations of the bovine immunoglobulin isotypes among the various pools of colostrum were positively correlated with concentration of these isotypes in the sera of the neonatal pigs fed these pools. Relative to their concentrations in colostrum, approximately 41% of the IgG1, 55% of the IgG2, 29% of the IgM, and 67% of the IgA was absorbed. The IgA was absorbed the best and IgM was least absorbed. Significant trends or differences in absorption were not observed among groups. Neonatal pigs given fresh colostrum, which had a higher fat content, had significantly more weight gain (P less than 0.05). This occurred, despite the fact that the fresh colostrum had the lowest concentration of bovine immunoglobulin. Serum half-lives for bovine IgG1 and IgG2 were significantly less than for porcine IgG (P less than 0.05), whereas the half-lives for bovine and porcine IgM and IgA were similar. De novo-synthesized immunoglobulins were detectable in serum after 6 days; IgM concentrations reached a maximum at 15 days in neonatal pigs given stored, but not fresh, colostrum.(ABSTRACT TRUNCATED AT 250 WORDS)     

Investigation of some factors which influence the absorption of IgG by the neonatal piglet

The absorption by the neonatal gut of purified swine IgG isolated from maternal serum was studied in 91 motherless piglets raised without swine colostrum, to investigate some of the factors which influence absorption. Factors studied included the amount of IgG administered, the effect of bovine colostrum fed concurrently, the influence of starvation and the effect of lactose.Administration of iodinated IgG within 3 hours after birth resulted in the appearance of IgG in the piglet circulation in unaltered form. Immediate feeding of bovine colostrum followed by administration of iodinated IgG at 72 hours resulted in the appearance of only IgG digestion fragments in the circulation.Administration of 15 g of lactose during the first 24 hours reduced absorption of IgG by 26% compared to controls while treatment with 54 g of lactose reduced absorption by 94%. On the contrary, when bovine colostrum was administered immediately after purified IgG, the amount of swine IgG absorbed was 50–70% greater than in controls. Mature milk failed to have the same influence. Finally, in experiments in which the amount of purified swine IgG administered varied from 1.0 to 8.0 g, absorption was directly proportional to the amount administered. When these data were compared with data on naturally reared piglets, the same proportionality was seen and indicated a consistent 1:2.5 to 1:3 ratio of ingested IgG (g) to the maximal serum level of immunglobulin (mg/ml) resulting from absorption. IgA and IgM follow a similar pattern.The data are consistent with a regulated absorption mechanism, that appears to be lost very quickly after the initial ingestion of food. Heterologous protein and lactose alone can switch off this absorption mechanism, thus arguing against “gut closure” by a mechanism of receptor saturation by absorbed IgG. Bovine colostrum, when compared to mature milk, is able to augment the absorption of swine IgG by an unknown mechanism.     

Enzyme-linked immunosorbent assay for detection of antibody to Pseudomonas aeruginosa and measurement of antibody titer in horse serum

Enzyme-linked immunosorbent assay (ELISA) was used for detection of immunoglobulin (Ig) M and IgG antibodies against a serologically common antigen (original endotoxin protein), protease, and elastase of Pseudomonas aeruginosa. The P aeruginosa antibody in horse sera was measured, using ELISA. Horseradish peroxidase-labeled rabbit anti-horse IgM and IgG antibodies were used for enzyme-labeled antibody conjugate. 5-Aminosalicylic acid and H2O2 were used for substrate. Sera collected from a vaccinated horse, a newborn foal, and 72 healthy racehorses were investigated for antibodies against P aeruginosa by ELISA and passive hemagglutination procedure. Changes in IgM and IgG antibody titers with vaccination were clear by ELISA. In the newborn foal, significant amounts of IgM and IgG antibodies from colostrum were present on the 1st day after birth. It was shown by ELISA that the level of antibodies in the newborn decreased initially and then increased. Some antibodies against original endotoxin protein, protease, and elastase of P aeruginosa were detected in almost all the healthy racehorses investigated.     

Intestinal antibody response after vaccination and infection with rotavirus of calves fed colostrum with or without rotavirus antibody

The intestinal and systemic antibody response of calves vaccinated and/or challenged with rotavirus was studied employing isotype-specific ELISAs for the detection of IgG1, IgG2, IgM and IgA antibodies to rotavirus. Monoclonal antibodies to bovine immunoglobulin isotypes of proven specificity were used as conjugated or catching antibody. Five days after oral inoculation (dpi) of a 5-day-old gnotobiotic calf with rotavirus, IgM rotavirus antibodies were excreted in faeces, followed 5 days later by IgA rotavirus antibodies. The increase in IgM rotavirus antibody titre coincided with the inability to detect further rotavirus excretion. Faeces IgM and IgA rotavirus antibody titres fell to low levels within 3 weeks post infection. IgG1 and IgG2 rotavirus antibodies were not detected in faecal samples. In serum, antibodies to rotavirus of all four isotypes were detected, starting with IgM at 5 dpi. Two SPF-calves, which were fed colostrum free of rotavirus antibodies, were vaccinated with a modified live rotavirus vaccine and challenged with virulent rotavirus 6 days later. Upon vaccination, the calves showed an antibody response similar to the response of the infected gnotobiotic calf. Intestinal IgM rotavirus antibodies were excreted before or on the day of challenge and appeared to be associated with protection against challenge infection with virulent virus and rotavirus-induced diarrhoea. In 3 control calves, which were challenged only, the antibody patterns also resembled that of the gnotobiotic calf and again the appearance of IgM rotavirus antibodies coincided with the end of the rotavirus detection period. Two other groups of 3 SPF-calves were treated similarly, but the calves were fed colostrum with rotavirus antibodies during the first 48 h of life. These calves excreted passively acquired IgG1 and IgG2 rotavirus antibodies in their faeces from 2 to 6 days after birth. After vaccination, no IgM or IgA antibody activity in serum or faeces was detectable. Upon challenge, all calves developed diarrhoea and excreted rotavirus. Seven to 10 days after challenge low levels of IgM rotavirus antibody were detected for a short period. These data indicate that the intestinal antibody response of young calves to an enteric viral infection is associated with the excretion of IgM antibodies, immediately followed by IgA antibodies. This response is absent or diminished in calves with passively acquired specific antibodies which may explain the failure to induce a protective intestinal immune response by oral vaccination with modified live rotavirus of calves fed colostrum containing rotavirus antibodies.     

The Influence of Sow Colostrum Trypsin Inhibitor on the Immunoglobulin Absorption in Newborn Piglets

The influence of sow colostrum trypsin inhibitor (SCTI) on the immunoglobulin absorption from the gut of 16 newborn colostrum-deprived piglets was investigated in a paired feeding experiment.Three times at 1 h intervals the piglets were fed an experimental diet consisting of sow milk, purified swine serum immunoglobulins containing agglutinins against Bordetella bronchiseptica, and purified SGTI (diet I) or saline (diet II). The serum concentrations of IgG, IgM, IgA, and antibodies for B. bronchiseptica were measured by single radial immunodiffusion and by a tube agglutination procedure and used to evaluate the immunoglobulin absorption. Four and 6 h after the first experimental meal, blood samples from the piglets given SGTI in their diet had a generally higher level of IgG, IgA and aggutinins against B. bronchiseptica than blood samples from the piglets d no SGTI. No real differences were found in the IgM levels. Although the piglets fed no SGTI all showed a considerable immunoglobulin absorption, the SCTI was found to have a statistically significant positive influence on the IgG and IgA absorption.     

Dynamic changes of immunoglobulin concentrations in pig colostrum and serum around parturition

The aim of the study was the determination of IgA, IgM and IgG concentrations in porcine serum and colostrum, in order to evaluate their variations in the perinatal period, as well as to clarify whether there is a correlation between colostrum intake, initial level of immunoglobulins (Ig) in piglet serum and development of their own immunity. The mean IgA, IgM and IgG concentrations in sow serum 10 days before parturition were 1.58, 6.12 and 39.56 mg/ml, respectively. Seven days later only the IgG level was insignificantly lower (34.94 mg/ml, p = 0.55), while concentrations of IgA and IgM increased to 2.25 and 7.25 mg/ml, respectively (p = 0.23 and 0.62, respectively). The mean initial IgG concentration in colostrum at farrowing was 118.5 mg/ml and differed between sows. The average value of IgA in colostrum at birth was 23.8 mg/ml and decreased to 7.85 mg/ml at 6 hours (h) and to 4.59 mg/ml at 24 h after the onset of farrowing. IgM concentration at birth was 12.1 mg/ml and decreased to 4.23 mg/ml at 24 h postpartum. Positive relationships were found between concentrations of IgM and IgA in serum of piglets at 14 and 56 days of life (r = 0.41 and 0.80, respectively, p < or = 0.05) as well as for IgG concentration in the piglets serum at 7 days and 56 days of age (r = 0.48, p < or = 0.05). The above observations suggest that there is a correlation between the level of Ig in piglet serum in the first days of life and improvement of their own immunity.     

A longitudinal study of rotavirus antibody titers in swine in a closed specific pathogen-free herd.

In a newly established closed specific pathogen-free (SPF) swine herd, gilt/sow suckling and weaned pig rotavirus specific antibody titers were followed for three lactations by enzyme-linked immunosorbent assay (ELISA) to gain insight into the dynamics of herd antibody titers to group A rotavirus. Among gilts/sows, serum antirotavirus IgG titers increased during each lactation with a subsequent drop in titer between farrowings. Serum antirotavirus IgM titers declined during each lactation and with subsequent parity. Serum antirotavirus IgA titers remained constant during lactations and among parities. In colostrum and milk, antirotavirus IgA antibody was abundant. Differences in titer were not noticed between gilts and second litter sows but third litter sows had significantly higher titers than the first two groups. Antirotavirus IgG was high in colostrum but nearly nonexistent in milk. This titer did not vary significantly within or among parities. There was a linear regression in the titers of baby pig serum antirotavirus IgG from the post colostral sample through to seven weeks old, after which titer began to increase. No difference in baby pig serum antirotavirus IgG was noted among the three litters. Serum antirotavirus IgA and IgM were undetectable in baby pig sera after 2-3 weeks of age. Coproantibody to rotavirus was sporadically present in pig feces for 2-3 weeks after birth with highest titers in the IgA fraction. We conclude that although it is probable that age resistance of pigs to rotavirus diarrhea occurs, humoral immunity as measured by ELISA rotavirus antibody titers may not be intimately involved in virus clearance since in our studies baby pigs passively received large amounts of antibody but still excreted pathogenic virus. The finding of increasing levels of serum antirotavirus IgG in gilt/sow serum suggest that exposure to antigen of dams occur without significant increases in antirotavirus IgG titers in either colostrum, milk, or baby pig serum.     

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to bovine viral diarrhoea virus (BVDV) in cattle sera

A microtitre ELISA has been established for the quantitation of antibodies to bovine viral diarrhoea virus (BVDV). Single dilutions of sera were assayed and units of antibody were calculated from a standard curve. In order to detect the maximum number of responding animals both IgG1 and IgG2 antibody should be assayed, although detection of IgG1 alone was nearly as effective. The ELISA was as sensitive as the virus neutralization test for detection of antibody; comparison of an ELISA that detected IgG1 plus IgG2 antibody to BVDV with the virus neutralization test gave a correlation coefficient (r) of 0.89 (P less than 0.001 for 95 compared sera). Although similar amounts of IgG1 and IgG2 antibodies were present in sera from both experimentally- and naturally-infected cattle, antibody to BVDV in colostrum and in the sera from young calves was predominantly IgG1. The number of adult cows with antibody was 40 out of 41 while 36 of 44 calves reared in a beef unit were found to have produced antibody by the time they were 31.5 weeks old, an indication of the high prevalence of BVDV in the cattle population.     

大肠杆菌MM—3基因工程活菌苗免疫母猪所产仔猪抗K_(88ac)及抗LTB抗体动态

应用BA-ELISA,分别检测了用大肠杆菌MM-3基因工程活菌苗免疫妊娠92d母猪所产仔猪血清和消化液中抗K_(88ac)及抗LTB抗体的动态消长.结果表明,新生仔猪在吃初乳后24h内,血清及消化液中抗K_(88ac)及抗LTB抗体水平均很高,但以后逐渐下降,1周后IgM、2～3周后IgA、3～4周后IgG分别下降到最低水平;仔猪35日龄时,抗体水平有所回升.消化液中抗体水平比血清中抗体水平下降快,并与母体乳汁中的抗体水平呈正相关关系.     

Variations in the concentrations of the immunoglobulins IgG1, IgG2, IgM and IgA in sheep. 2. Changes in the blood of lambs of different breeds and crossbreeds during the course of the rearing period

The sera of 188 lambs from seven breed groups were analyzed for the concentrations of IgG1, IgG2, IgM and IgA by radial immunodiffusion using monospecific antibodies. From each lamb, 14 blood samples were drawn before and 5 samples after weaning. The following results were obtained: 1. Immunoglobulins could not be detected in sera drawn before the first intake of colostrum. 2. In normally suckling lambs, the peak concentrations of maternal immunoglobulins are attained at 0-18 hrs after birth. They can be assessed in a single blood sample drawn between 18 and 24 hrs. 3. The half-life times of maternal immunoglobulin in lamb sera are 11 days for IgG1, 7 days for IgG2, 6 days for IgM and 18 hours for IgA. 4. The absolute peak heights relate to the amounts of colostrum ingested before 12-18 hrs after birth. 5. The decline of maternal immunoglobulins in lamb sera over-laps with the onset of lamb immunoglobulin synthesis. Renewed rises of concentrations are observed for IgG2 after week 2, for IgM after week 3 and for IgG1 after week 7. The concentrations of IgA remain at the low levels characteristic for the serum of grown sheep. 6. The role of immunoglobulin synthesis in suckling lambs is only briefly and to a small extent reduced after weaning.     

Humoral immune response of the duck to duck hepatitis virus: virus-neutralizing vs. virus-precipitating antibodies

Ducks were induced to develop high-level duck hepatitis virus (DHV)-neutralizing antibodies by inculation with a chicken-embryo-adapted DHV via subcutaneous, intramuscular, and intratracheal routes. Administration of the DHV orally in a gelatin capsule failed to stimulate immune response in the ducks. Contact controls of these ducks also remained negative for anti-DHV antibodies. These observations indicated that the DHV administered orally, in gelatin capsule, failed to infect the ducks. None of numerous duck anti-DHV immune sera, with virus-neutralizing activity in the range of 1.8 to 5.57 log10 median- embryo-infective-dose (EID50) neutralization index, developed precipitin lines against a variety of DHV preparations tested in low- and high-ionic-strength agar. The results suggest that the agar-gel immunodiffusion test is unsuitable for serologic testing of duck sera for anti-DHV antibody activity. Virus-neutralizing activity was revealed in both immunoglobulin M (IgM) and IgG classes of sera of actively immunized ducks. Immunodiffusion tests of Sephadex G-200 fractions of 1-day-old duckling sera with monospecific rabbit anti-duck IgM (DIgM) serum failed to detect DIgM. These results demonstrated that the IgM is not being transferred from the dam to the newly hatched ducklings. Seven- and 14-day-old ducks had DIgM in their sera. However, this IgM had no DHV-neutralizing activity, indicating that it was newly developed by the ducklings, which had no active DHV immune response, not having been exposed to DHV.     

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.