The neonatal Fc receptor plays a crucial role in the metabolism of IgG in livestock animals

Genetic aspects of immunoglobulins and cyclophilin A in milk as potential indicators of mastitis resistance in Holstein cows

Mastitis is one of the most frequent and costly diseases affecting dairy cattle. Natural antibodies (immunoglobulins) and cyclophilin A (CyPA), the most abundant member of the family of peptidyl prolyl cis/trans isomerases, in milk may serve as indicators of mastitis resistance in dairy cattle. However, genetic information for CyPA is not available, and knowledge on the genetic and nongenetic relationships between these immune-related traits and somatic cell score (SCS) and milk yield in dairy cattle is sparse. Therefore, we aimed to comprehensively evaluate whether immune-related traits consisting of 5 Ig classes (IgG, IgG1, IgG2, IgA, and IgM) and CyPA in the test-day milk of Holstein cows can be used as genetic indicators of mastitis resistance by evaluating the genetic and nongenetic relationships with SCS in milk. The nongenetic factors affecting immune-related traits and the effects of these traits on SCS were evaluated. Furthermore, the genetic parameters of immune-related traits according to health status and genetic relationships under different SCS environments were estimated. All immune-related traits were significantly associated with SCS and directly proportional. Additionally, evaluation using a classification tree revealed that IgA, IgG2, and IgG were associated with SCS levels. Genetic factor analyses indicated that heritability estimates were low for CyPA (0.08) but moderate for IgG (0.37), IgA (0.44), and IgM (0.44), with positive genetic correlations among Ig (0.25-0.96). We also evaluated the differences in milk yield and SCS of cows between the low and high groups according to their sires' estimated breeding value for immune-related traits. In the high group, IgA had a significantly lower SCS in milk at 7 to 30 d compared with that in the low group. Furthermore, the Ig in milk had high positive genetic correlations between healthy and infected conditions (0.82-0.99), suggesting that Ig in milk under healthy conditions could interact with those under infected conditions, owing to the genetic ability based on the level of Ig in milk. Thus, Ig in milk are potential indicators for the genetic selection of mastitis resistance. However, because only the relationship between immune-related traits and SCS was investigated in this study, further study on the relationship between clinical mastitis and Ig in milk is needed before Ig can be used as an indicator of mastitis resistance.

Validation of a serum ELISA test for cyathostomin infection in equines

Cyathostomins are ubiquitous equine nematodes. Infection can result in larval cyathostominosis due to mass larval emergence. Although faecal egg count (FEC) tests provide estimates of egg shedding, these correlate poorly with burden and provide no information on mucosal/luminal larvae. Previous studies describe a serum IgG(T)-based ELISA (CT3) that exhibits utility for detection of mucosal/luminal cyathostomins. Here, this ELISA is optimised/validated for commercial application using sera from horses for which burden data were available. Optimisation included addition of total IgG-based calibrators to provide standard curves for quantification of antigen-specific IgG(T) used to generate a CT3-specific 'serum score' for each horse. Validation dataset results were then used to assess the optimised test's performance and select serum score cut-off values for diagnosis of burdens above 1000, 5000 and 10,000 cyathostomins. The test demonstrated excellent performance (Receiver Operating Characteristic Area Under the Curve values >0.9) in diagnosing infection, with >90% sensitivity and >70% specificity at the selected serum score cut-off values. CT3-specific serum IgG(T) profiles in equines in different settings were assessed to provide information for commercial test use. These studies demonstrated maternal transfer of CT3-specific IgG(T) in colostrum to newborns, levels of which declined before increasing as foals consumed contaminated pasture. Studies in geographically distinct populations demonstrated that the proportion of horses that reported as test positive at a 14.37 CT3 serum score (1000-cyathostomin threshold) was associated with parasite transmission risk. Based on the results, inclusion criteria for commercial use were developed. Logistic regression models were developed to predict probabilities that burdens of individuals are above defined thresholds based on the reported serum score. The models performed at a similar level to the serum score cut-off approach. In conclusion, the CT3 test provides an option for veterinarians to obtain evidence of low cyathostomin burdens that do not require anthelmintic treatment and to support diagnosis of infection.

Passive transfer of alloantibodies through breast milk as a mediator of hemolytic anemia

BACKGROUND

Hemolytic disease of the fetus and newborn (HDFN) is characterized by destruction of fetal/neonatal red blood cells (RBCs) secondary to maternally derived antibodies, which are typically thought to be passively acquired via placental transfer. Few cases have examined the possibility of HDFN mediated by maternal antibodies passively transferred via breast milk.

METHODS

We describe two cases of persistent HDFN in infants potentially mediated by passively acquired antibodies via maternal breast milk. We discuss supporting and refuting evidence that may account for this possibility and describe testing methodology illustrating how maternal alloantibodies can be detected in breast milk.

RESULTS

In both cases, anti-D antibodies were detected in maternal breast milk. One patient experienced a significant decrease in anti-D plasma titer from 64 to 4 dilutions following 2 weeks of breastfeeding cessation. The other patient experienced a resolution of anemia without breastfeeding cessation.

CONCLUSION

There is a paucity of data regarding the lifespan of passively acquired RBC antibodies in neonatal circulation, with significant variation noted between passively acquired IgG based on studies utilizing intravenous immunoglobulin compared to studies of maternally-acquired antiviral IgG antibodies. While our data do not definitively implicate passive transfer of alloantibodies in breast milk as a mediator of HDFN, they do illustrate the need for further investigation into the mechanisms and kinetics of passively acquired antibodies in neonatal circulation.

Immunogenic fusion proteins induce neutralizing SARS-CoV-2 antibodies in the serum and milk of sheep

Antigen-specific polyclonal immunoglobulins derived from the serum, colostrum, or milk of immunized ruminant animals have potential as scalable therapeutics for the control of viral diseases including COVID-19. Here we show that the immunization of sheep with fusions of the SARS-CoV-2 receptor binding domain (RBD) to ovine IgG2a Fc domains promotes significantly higher levels of antigen-specific antibodies compared to native RBD or full-length spike antigens. This antibody population contained elevated levels of neutralizing antibodies that suppressed binding between the RBD and hACE2 receptors in vitro. A second immune-stimulating fusion candidate, Granulocyte-macrophage colony-stimulating factor (GM-CSF), induced high neutralizing responses in select animals but narrowly missed achieving significance. We further demonstrated that the antibodies induced by these fusion antigens were transferred into colostrum/milk and possessed cross-neutralizing activity against diverse SARS-CoV-2 variants. Our findings highlight a new pathway for recombinant antigen design in ruminant animals with applications in immune milk production and animal health.

Effects of yeast-derived postbiotic supplementation in late gestation and lactation diets on performance, milk quality, and immune function in lactating sows

This experiment was conducted to determine the effects of yeast-derived postbiotic (YDP) supplementation in sow diets during late gestation and lactation on the performance of sows and their offspring. At 90-d gestation, 150 sows (Landrace × Large White, parity: 3.93 ± 0.11) were allocated to three dietary treatments (n = 50 per treatment): 1) basal diet (control [CON]), 2) basal diet with 1.25 g/kg YDP (0.125 group), and 3) basal diet with 2.00 g/kg YDP (0.200 group). The experiment continued until the end of weaning (day 21 of lactation). Supplementation with YDP resulted in greater deposition of backfat in sows during late gestation and an increasing trend in average weaning weight of piglets than observed in the CON group (P < 0.01, P = 0.05). Supplementation with YDP decreased piglet mortality and diarrhea index in piglets (P < 0.05). In farrowing sows' serum, the glutathione peroxide content in the YDP group was lower than that in the CON group (P < 0.05); the content of immunoglobulin A (IgA) in the 0.200 group or YDP group was higher than that in the CON group (P < 0.05). In lactating sows' serum, malondialdehyde content was higher in the YDP group (P < 0.05). In day 3 milk of sows, the 0.200 group tended to increase the lactose content (P = 0.07), and tended to decrease the secretory immunoglobulin A (sIgA) content (P = 0.06) with respect to that in the CON group. The sIgA content in the YDP group was lower than that in the CON group (P < 0.05). In the milk of sows, the 0.200 group tended to increase the lactose content with respect to that in the CON group (P = 0.08); the immunoglobulin G (IgG) content in the 0.125 group or YDP group was higher than that in the CON group (P < 0.05). YDP supplementation increased the IgA content in the milk (P < 0.01). In sow placenta, the content of total anti-oxidant capacity in the YDP group was higher than that in the CON group (P = 0.05); and the content of transforming growth factor-β in the YDP group was higher than that in the CON group (P < 0.05). In piglet serum, the content of IgG and immunoglobulin M in the 0.125 group was higher than that in the CON and 0.200 groups (P < 0.05). In summary, this study indicated that feeding sows diets supplemented with YDP from late gestation through lactation increased sows' backfat deposition in late gestation and piglets' weaning weight; decreased piglet mortality and diarrhea index in piglets; and improved maternal and offspring immunity.

On the influence of the source of porcine colostrum in the development of early immune ontogeny in piglets

The effects on the ontogeny of serum cytokines and immune cells caused by feeding suckling piglets with sow/gilt colostrum and milk replacer was assessed in the present study. After farrowing, the piglets born were randomized into six groups: GG and SS (n = 10/group): piglets were kept with their dam; GS (n = 10): piglets were changed from gilts to sows; SG (n = 10): piglets were changed from sows to gilts; GMR (n = 6) and SMR (n = 8): piglets from either gilts or sows were isolated from the dams and were bottle-fed ad libitum with commercial formula milk replacer. The piglets remained in the groups during the first 24 h of life and were later returned to their respective mothers. Serum immunoglobulin concentration and lymphocyte proliferation from the blood, spleen, thymus, and mesenteric lymph node of the piglets were assessed at 24 h and at 28 days of age. Serum cytokine concentrations were measured through a cytokine multiplex assay at 24 h. Overall, piglets suckling on sows (SS and GS) had a higher concentration of serum immunoglobulin at 24 h, which was also associated with a rise in plasma cytokine concentration and greater ability of B and T cells from lymphatic organs and blood mononuclear cells to respond to mitogens. We suggest a bias towards Th1-, Th2-, and Th17-cell polarizing and cytokines during the suckling period, which may be influenced by maternal immunological factors in the colostrum, such as dam parity. All findings suggest sow parity having a possible role, which may contribute to exerting a modulating action on immune response development.

In vitro and in vivo Studies of Soybean Peptides on Milk Production, Rumen Fermentation, Ruminal Bacterial Community, and Blood Parameters in Lactating Dairy Cows

Soybean peptides (SPs), a feed additive derived from soybean, exhibit nutritional function and biological activity in monogastric animals, but limited studies have been conducted in dairy cows. Our experiments were conducted to evaluate the effects of SPs on the nutrient degradability of dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) in vitro and milk production, rumen fermentation and bacterial community, and blood parameters of dairy cows. For in vitro experiment, ruminal fluids were collected from three ruminal cannulated Holstein dairy cows. A total of three levels of SPs (0, 0.38, and 1.92 g/kg DM of SPs) were added to the total mixed ration (TMR). Nutrient degradability and fermentation fluid pH were determined at 24 and 48 h using 3.0 g samples of the substrate. Gas production after 48 h was recorded by an automated trace gas recording system using 0.5 g samples of the substrate. The results showed that DM, NDF, ADF (p < 0.01), and CP (p < 0.05) degradabilities were significantly increased at 1.92 g/kg DM of SPs at 24 h, and asymptotic gas production (p = 0.05) was increased at 48 h. For in vivo experiment, 110 lactating Holstein cows (209.7 ± 65.2 DIM; 37.2 ± 6.4 kg/d milk yield) were randomly assigned to 0 (control group, CON) or 50 g/head/day SPs (SP-supplemented group). Yields of milk (p < 0.05), milk protein (p < 0.05), and milk lactose (0.05 < p < 0.10) increased on SPs supplementation; however, the milk fat percentage decreased (p < 0.05). The concentrations of individual volatile fatty acids (VFAs) (p < 0.05) and superoxide dismutase (SOD) (p < 0.01) were also increased. Rumen bacterial diversity in SP-supplemented cows was higher (p < 0.05). The relative abundances of Rikenellaceae_RC9_gut_group, Butyrivibrio, Selenomonas, and Shuttleworthia were significantly increased and that of Coprococcus was decreased (p < 0.05). Our results showed that supplementing 1.92 g/kg DM of SPs could improve the nutrient degradability in vitro and 50 g/head/day of SPs could improve milk production and antioxidant ability of dairy cows. The rumen bacterial diversity was also enhanced by SP supplementation.

Impact of maternally derived immunity on immune responses elicited by piglet early vaccination against the most common pathogens involved in porcine respiratory disease complex

Background

Newborn piglets can trigger an elementary immune response, but the acquirement of specific antibodies and/or cellular immunity against pathogens before they get infected post-natally is paramount to preserve their health. This is especially important for the pathogens involved in porcine respiratory disease complex (PRDC) as they are widespread, fairly resistant at environment, and genetically variable; moreover, some of them can cause intrauterine/early life infections.

Main body

Piglet protection can be achieved by either passive transfer of maternal derived immunity (MDI) and/or actively through vaccination. However, vaccinating piglets in the presence of remaining MDI might interfere with vaccine efficacy. Hence, the purpose of this work is to critically review the putative interference that MDI may exert on vaccine efficacy against PRDC pathogens. This knowledge is crucial to design a proper vaccination schedule.

Conclusion

MDI transferred from sows to offspring could potentially interfere with the development of an active humoral immune response. However, no conclusive interference has been shown regarding performance parameters based on the existing published literature.

Effects of colostrum management on transfer of passive immunity and the potential role of colostral bioactive components on neonatal calf development and metabolism

Neonatal dairy and beef calves are required to ingest adequate volumes of high-quality colostrum during their first hours of life to acquire transfer of passive immunity (TPI). As such, immunoglobulin G (IgG) has largely been the focus of colostrum research over recent decades. Yet, little is known about the additional bioactive compounds in colostrum that potentially influence newborn calf development and metabolism. The purpose of this narrative review is to synthesize research regarding the effects of colostrum management practices on TPI, as well as to address the potential role of additional colostral bioactive molecules, including oligosaccharides, fatty acids, insulin, and insulin-like growth factor-I, in promoting calf development and metabolism. Due to the importance of IgG in ensuring calf immunity and health, we review past research describing the process of colostrogenesis and dam factors influencing the concentrations of IgG in an effort to maximize TPI. We also address the transfer of additional bioactive compounds in colostrum and prepartum management and dam factors that influence their concentrations. Finally, we highlight key areas of future research for the scientific community to pursue to ultimately improve the health and welfare of neonatal dairy calves.

Interaction between the level of immunoglobulins and number of somatic cells as a factor shaping the immunomodulating properties of colostrum

The aim of this study was to investigate the association between immunoglobulins and SCC as a factor in shaping the content of the immunostimulatory components of colostrum. Seventy-eight multiparous Polish Holstein-Friesian cows were selected for the experiment. Colostrum samples were collected immediately after calving (up to a max. of 2 h). The cows were divided into groups according to the following levels: Immunoglobulins (IG class)-(IG₁) over 50 g/L, (IG₂) up to 50 g/L; SCC class-(SCC₁) up to 400 000/ml, (SCC₂) 400-800 000/ml, (SCC₃) over 800 000/ml. Colostrum assigned to the IG₁ SCC₁ group had a statistically significant higher (p ≤ 0.01) concentration of both whey proteins and fatty acids compared to the IG₁ SCC₂ and SCC₃ groups. The concentration of IgG, IgM, and IgA was shown to be higher in IG₁ SCC₁ than IG₂ SCC₃ by 226%, 149%, and 115%, respectively. The concentration of lactoferrin was shown to be higher in IG₁ SCC₁ than IG₂ SCC₃ by 149%. The determination of colostrum quality based on the concentration of immunoglobulins in the colostrum may not be sufficient because serum IgG concentrations at birth show a linear increase relative to colostrum SCC. A breakdown of colostrum into quality classes, taking into account the level of SCC, should therefore be introduced.

FcRn is not the receptor mediating the transfer of serum IgG to colostrum in pigs

In contrast to humans or rabbits, in which maternal IgG is transmitted to offspring prenatally via the placenta or the yolk sac, large domestic animals such as pigs, cows and sheep transmit IgG exclusively through colostrum feeding after delivery. The extremely high IgG content in colostrum is absorbed by newborns via the small intestine. Although it is widely accepted that the neonatal Fc receptor, FcRn, is the receptor mediating IgG transfer across both the placenta and small intestine, it remains unclear whether FcRn also mediates serum IgG transfer across the mammary barrier to colostrum/milk, especially in large domestic animals. In this study, using a FcRn knockout pig model generated with a CRISPR-Cas9-based approach, we clearly demonstrate that FcRn is not responsible for the IgG transfer from serum to colostrum in pigs, although like in other mammals, it is involved in IgG homeostasis and mediates IgG absorption in the small intestine of newborns.

Methods of feeding colostrum and their effect on the passive immunity

Passive transport of colostral immunoglobulins is essential for calves to maintain optimal health. There are many factors that influence the absorption of immunoglobulins such as colostrum density, timing of ingestion, volume of colostrum but also the method of feeding. This study compares two manners of feeding calves – the esophageal tube feeder (n = 97) and the nipple bottle (n = 97), and their effect on the number of all absorbed immunoglobulins (IgG, IgM, IgA, IgD, and IgE). It was statistically proven that absorption of immunoglobulins is better with the nipple bottle (P < 0.0001). The feeding of calves through a nipple bottle is more beneficial because the content of total protein is the higher than by the feeding through an esophageal tube feeder.

Genome wide association study of passive immunity and disease traits in beef-suckler and dairy calves on Irish farms

Calves with lower concentrations of immunoglobulin G (IgG) in their blood, have a greater risk of developing diseases. There is a lack of knowledge on genetic markers known to be associated with immunological variability or disease resistance. Therefore, the objective of this study was to identify SNP markers associated with passive immunity measures (serum IgG, serum protein, albumin, globulin and total protein concentrations, total solids Brix percentage, zinc sulphate turbidity units) and disease (pneumonia, diarrhoea, crude illness) traits in Irish commercial beef-suckler and dairy calves through genome wide association studies (GWAS). Genotyping was performed on DNA samples from beef-suckler (n = 698) and dairy (n = 1178) calves, using the IDBv3 chip. Heritability of passive immunity associated traits (range 0.02-0.22) and the disease traits (range 0.03-0.20) were low-to-moderate. Twenty-five and fifteen SNPs approached genome wide significance (P < 5 × 10^-5) for the passive immunity and the disease traits, respectively. One SNP "ARS-BFGL-BAC-27914" reached Bonferroni genome wide significance (P < 1.15 × 10^-6) for an association with serum IgG concentration in beef calves. Further work will evaluate these SNPs in larger cattle populations and assess their contribution to genomic selection breeding strategies, aimed towards producing more disease resistant livestock.

Changes in expression of antimicrobial peptides and Fc receptors in the small intestines of neonatal calves during the passive immunity period

The contribution of colostrum to passive immunity transfer and intestinal protection is well known; however, the effects of colostrum intake on the expression of antimicrobial peptides (AP) and Fc receptors in the intestine of neonatal calves are unclear. Our aim was to investigate changes in the expression of AP and Fc receptor in the small intestine of calves in the first 36 h postpartum. Twenty-four Holstein bull calves were used in this study, of which 18 calves were administered 3.2 L of pooled colostrum for each calf per meal via an esophageal tube. Calves were slaughtered at 8 h (1 meal at 1-2 h), 24 h (2 meals at 1-2 h and 10-12 h), and 36 h (3 meals at 1-2 h, 10-12 h, and 22-24 h) postpartum. The remaining 6 calves without any milk administration were slaughtered at 2 h postpartum. Samples of blood and jejunum digesta were collected to determine immunoglobulin concentration using ELISA. Samples of the duodenum, jejunum, and ileum tissues after slaughter were collected to determine AP and Fc receptor expression using quantitative real-time PCR. In calves administered colostrum, IgG concentration in jejunum digesta rapidly decreased in an age-dependent manner (33.41, 9.47, and 0.34 mg/mL at 8, 24, and 36 h, respectively), whereas serum IgG concentration increased significantly, from 0.25 μg/mL at 2 h to 21.72 mg/mL at 24 h. Cathelicidin-4, β-defensin (DEFB)-7, and enteric β-defensin expression was upregulated at 8 h postpartum in the duodenum and jejunum compared with that at 2 h, but progressive recovery was detected from 24 h onward. Higher expression of cathelicidin-4, regenerating family member 3γ, lysozyme (LYZ), LYZ1, and LYZ2 and lower expression of DEFB, DEFB1, DEFB7, DEFB10, and enteric β-defensin were observed in the duodenum and jejunum compared with the ileum. Differences in AP expression between intestinal regions suggested that the innate immune defense mechanism varied significantly among the duodenum, jejunum, and ileum. No difference in the expression of Fc fragment of the IgG receptor was observed either among ages or small intestinal regions. The Fcγ receptor (FcγR)Ia and FcγRIIb expression was the highest at 8 h compared with that at 2, 24, and 36 h, and expression of FcγRIa, FcγRIIb, and FcγRIIIa was higher in the duodenum and jejunum than in the ileum. These results indicated that AP and Fcγ receptors might play important roles in intestinal defense during the passive immunity period.

Evaluation of Passive Immunity Induced by Immunisation Using Two Inactivated gE-deleted Marker Vaccines against Infectious Bovine Rhinotracheitis (IBR) in Calves

Different types of vaccines against Infectious Bovine Rhinotracheitis (IBR) are commercially available. Among these, inactivated glycoprotein E (gE)-deleted marker vaccines are commonly used, but their ability to induce passive immunity is poorly known. Here, we evaluated the passive immunity transferred from dams immunised with commercial inactivated gE-deleted marker vaccines to calves. We vaccinated 12 pregnant cattle devoid of neutralising antibodies against Bovine alphaherpesvirus 1 (BoHV-1) and divided them into two groups with 6 animals each. Both groups were injected with a different inactivated gE-deleted marker vaccine administrated via intranasal or intramuscular routes. An additional 6 pregnant cattle served as the unvaccinated control group. After calving, the number of animals in each group was increased by the newborn calves. In the dams, the humoral immune response was evaluated before calving and, subsequently, at different times until post-calving day 180 (PCD180). In addition, the antibodies in colostrum, milk, and in serum samples from newborn calves were evaluated at different times until PCD180. The results indicated that inactivated glycoprotein E (gE)-deleted marker vaccines are safe and produce a good humoral immune response in pregnant cattle until calving and PCD180. Moreover, results showed that, in calf serum, passive immunity persists until PCD180.

Immune competence traits assessed during the stress of weaning are heritable and favorably genetically correlated with temperament traits in Angus cattle1

Selection for production traits with little or no emphasis on health-related traits has the potential to increase susceptibility to disease in food-producing animals. A possible genetic strategy to mitigate such effects is to include both production and health traits in the breeding objective when selecting animals. For this to occur, reliable methodologies are required to assess beneficial health traits, such as the immune capacity of animals. We describe here a methodology to assess the immune competence of beef cattle which is both practical to apply on farm and does not restrict the future sale of tested animals. The methodology also accommodates variation in prior vaccination history of cohorts of animals being tested. In the present study, the immune competence phenotype of 1,100 Angus calves was assessed during yard weaning. Genetic parameters associated with immune competence traits were estimated and associations between immune competence, temperament, and stress-coping ability traits were investigated. Results suggested that immune competence traits, related to an animal's ability to mount both antibody and cell-mediated immune responses, are moderately heritable (h2 = 0.32 ± 0.09 and 0.27 ± 0.08, respectively) and favorably genetically correlated with the temperament trait, flight time (r = 0.63 ± 0.31 and 0.60 ± 0.29 with antibody and cell-mediated immune responses, respectively). Development of methodologies to assess the immune competence phenotype of beef cattle is a critical first step in the establishment of genetic selection strategies aimed at improving the general disease resistance of beef herds. Strategies aimed at reducing the incidence of disease in beef cattle are expected to significantly improve animal health and welfare, reduce reliance on the use of antibiotics to treat disease, and reduce disease-associated costs incurred by producers.

Passive immune transfer in puppies

The puppy, born without immunoglobulins G (IgG), acquires a passive systemic immunity thanks to colostrum intake during the two first days of life. The quality of passive immune transfer (i.e. blood IgG concentration at two days of age), highly variable between litters and between puppies within litters, depends mainly on the time elapsed between birth and ingestion of colostrum, with limited influence of colostrum IgG concentration. Deficit in passive immune transfer, impacting puppy's health and neonatal mortality rate, can be indirectly diagnosed through blood gammaglutamyltransferases assay and evaluation of growth rate over the two first days of life. In the absence of maternal colostrum, few homo- and heterospecific immune sources are available and canine colostrum banking remains the optimal solution. Whereas passive immune transfer is crucial for survival during the neonatal period, it later interferes with response to vaccination. In addition to systemic passive immune transfer, maternal antibodies (mainly IgA) would provide local (digestive) immunity, ensuring mid-term protection of the puppies' gut together with probably long term training of the digestive immune system.

Effect of butyrate on passive transfer of immunity in dairy calves

The objectives of this study were to determine the effects of supplemental butyrate on (1) Ig production in dams and (2) Ig absorption in their calves. Twenty dry dams fed a close-up total mixed ration were assigned to either a control treatment (CTRL-D) or a butyrate treatment where the close-up total mixed ration was supplemented with butyrate at 1% of dry matter intake (wt/wt; BUT-D). At calving, calves were assigned to 1 of 2 treatments: a control group fed colostrum replacer only (CTRL-C) and a butyrate group fed colostrum replacer with supplemental butyrate at 2.5% (wt/vol; BUT-C). Serum IgG, glucose, and β-hydroxybutyrate were measured weekly in both dams and calves. Additionally, calves were weighed weekly to determine average daily gain. In dams, serum IgG concentration was not different between CTRL-D and BUT-D (1,785 ± 117 vs. 1,736 ± 137 mg/dL, respectively), nor was there a change in Ig levels in the colostrum between control and butyrate groups. Serum total protein did not differ between CTRL-D and BUT-D dams. Dam dry matter intake did not differ between CTRL-D and BUT-D but did decrease 1 wk before parturition. Compared with CTRL-C calves, BUT-C calves had significantly decreased serum IgG concentration at 24 h (2,110 ± 124 vs. 1,400 ± 115 mg/dL), wk 1 (1,397 ± 121 vs. 866 ± 115 mg/dL), and wk 2 (1,310 ± 121 vs. 797 ± 115 mg/dL). Additionally, apparent efficiency of absorption was lower for the BUT-C group compared with the CTRL-C group (35.3 ± 2.1 vs. 25.9 ± 2.0). Differences in serum Ig concentrations between the CTRL-C and BUT-C groups did not affect average daily gain (0.59 ± 0.05 vs. 0.48 ± 0.05 kg/d, respectively), serum glucose concentrations, or serum β-hydroxybutyrate concentrations. These data demonstrate that butyrate inclusion in colostrum negatively affects IgG absorption in newborn calves, whereas calf body weight gains were unaffected.

Immunomodulating effect of a seaweed extract from Ulva armoricana in pig: Specific IgG and total IgA in colostrum, milk, and blood

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MSP extract increased IgG anti-Bordetella titers with the highest dosage.

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Improved IgG anti-Bordetella transudation from the blood to the colostrum.

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MSP extract increased total IgA titers in the milk, 7 days after farrowing.

The transfer of passive immunity from sows to piglets can be improved through the administration of immuno-stimulating products before farrowing. This study evaluated the immuno-stimulating effect of an algal sulfated polysaccharide extract (MSP extract) from the green algae Ulva armoricana when administrated orally to sows at the end of gestation. Four diets were tested: Control (no MSP extract), MSP1 (2 g/day of MSP extract), MSP2 (8 g/day), and MSP3 (16 g/day). The experimental diets were provided in two periods: before the last atrophic rhinitis vaccine booster, and a week before farrowing. Anti-Bordetella IgG antibodies were recorded in blood, colostrum, and milk, and total IgA were measured in colostrum and milk. Titer kinetics between the blood sampled before farrowing and colostrum displayed an increase in specific IgG for MSP3. Moreover, the MSP2 diet increased the level of total IgA in milk compared to the control group. Although the immuno-stimulating effect of MSP extract on piglet performance was not concurrent across the different supplementation levels, the present study supports the use of natural algae extract (MSP) as an immunomodulating solution in swine production.

Effects of Bovine Immunoglobulins on Immune Function, Allergy, and Infection

This review aims to provide an in depth overview of the current knowledge of the effects of bovine immunoglobulins on the human immune system. The stability and functional effects of orally ingested bovine immunoglobulins in milk products are described and potential mechanisms of action are discussed. Orally ingested bovine IgG (bovine IgG) can be recovered from feces, ranging from very low levels up to 50% of the ingested IgG that has passed through the gastrointestinal tract. In infants the recovered levels are higher than in adults most likely due to differences in stomach and intestinal conditions such as pH. This indicates that bovine IgG can be functionally active throughout the gastrointestinal tract. Indeed, a large number of studies in infants and adults have shown that bovine IgG (or colostrum as a rich source thereof) can prevent gastrointestinal tract infections, upper respiratory tract infections, and LPS-induced inflammation. These studies vary considerably in target group, design, source of bovine IgG, dosage, and endpoints measured making it hard to draw general conclusions on effectiveness of bovine immunoglobulin rich preparations. Typical sources of bovine IgG used in human studies are serum-derived IgG, colostrum, colostrum-derived IgG, or milk-derived immunoglobulins. In addition, many studies have used IgG from vaccinated cows, but studies using IgG from nonimmunized animals have also been reported to be effective. Mechanistically, bovine IgG binds to many human pathogens and allergens, can neutralize experimental infection of human cells, and limits gastrointestinal inflammation. Furthermore, bovine IgG binds to human Fc receptors which, enhances phagocytosis, killing of bacteria and antigen presentation and bovine IgG supports gastrointestinal barrier function in in vitro models. These mechanisms are becoming more and more established and explain why bovine IgG can have immunological effects in vivo. The inclusion of oral bovine immunoglobulins in specialized dairy products and infant nutrition may therefore be a promising approach to support immune function in vulnerable groups such as infants, children, elderly and immunocompromised patients.

Detection, molecular characterization and phylogenetic analysis of G3P[12] and G14P[12] equine rotavirus strains co-circulating in central Kentucky

Equine rotavirus A (ERVA) is the leading cause of diarrhea in neonatal foals and a major health problem to the equine breeding industry worldwide. The G3P[12] and G14P[12] ERVA genotypes are the most prevalent in foals with diarrhea. Control and prevention strategies include vaccination of pregnant mares with an inactivated vaccine containing a prototype ERVA G3P[12] strain with limited and controversial field efficacy. Here, we performed the molecular characterization of ERVA strains circulating in central Kentucky using fecal samples collected during the 2017 foaling season. The data indicated for the first time that the G14P[12] genotype is predominant in this region in contrast to a previous serotyping study where only G3 genotype strains were reported. Overall, analysis of antigenic sites in the VP7 protein demonstrated the presence of several amino acid substitutions in the epitopes exposed on the surface including a non-conserved N-linked glycosylation site (D123N) in G14P[12] strains, while changes in antigenic sites of VP8* were minor. Also, we report the successful isolation of three ERVA G14P[12] strains which presented a high identity with other G14 strains from around the world. These may constitute ideal reference strains to comparatively study the molecular biology of G3 and G14 strains and perform vaccine efficacy studies following heterologous challenge in the future.

Somatic cell count-based selection reduces susceptibility to energy shortage during early lactation in a sheep model

During the transition from late gestation to early lactation ruminants experience a negative energy balance (NEB), which is considered to increase susceptibility to mammary infections. Our previous study in 2 divergent lines of sheep selected for high and low somatic cell score (SCS) suggested an association between the response to NEB and genetic susceptibility to mastitis. Forty-eight early-lactation primiparous dairy ewes from the 2 SCS genetic lines were allocated to 2 homogeneous subgroups-an NEB group, which was energy restricted and received 60% of the energy requirements for 15 d, and a control-fed group-to obtain 4 balanced groups of 12 ewes: high-SCS positive energy balance, low-SCS positive energy balance, high-SCS NEB, and low-SCS NEB. High-SCS ewes showed greater weight loss and increased plasmatic concentrations of β-hydroxybutyrate and nonesterified fatty acids than low-SCS ewes when confronted with an induced NEB. The aim of this study was to further characterize this interaction by combining transcriptomic and phenotypic data with a generalized partial least squares discriminant analysis using mixOmics package framework. A preliminary analysis using 3 blocks of phenotypes (fatty acids, weight and production, blood metabolites) revealed a high correlation between fat-to-protein ratio, β-hydroxybutyrate, and nonesterified fatty acids concentrations with milk long-chain fatty acid yields. These phenotypes allowed good discrimination of the energy-restricted high-SCS ewes and confirmed a high level of adipose tissue mobilization in this group. A second analysis, which included RNA-seq data, revealed high correlations between the long-chain fatty acid yields in milk and PDK4, CPT1A, SLC25A20, KLF10, and KLF11 expression, highlighting the relationship between mobilization of body reserves and enhanced fatty acids utilization for energy production in blood cells. Finally, analysis of milk composition measured in 1,025 ewes from the 2 genetic lines over 10 yr confirmed significant higher fat-to-protein ratio in high-SCS ewes in early lactation. Altogether, our results strongly confirmed a genetic link between susceptibility to mastitis and metabolic adaptation to energy shortage. Improving genetic resistance to mastitis using SCS should be accompanied by a favorable effect on the response to metabolic stress, especially in highly stressful early lactation. Moreover, this study suggests that the fat-to-protein ratio could be used as a low-cost tool for monitoring energy balance and ketosis during this critical phase of lactation.

Maternal Vaccination. Immunization of Sows during Pregnancy against ETEC Infections

The immunology of pregnancy is an evolving consequence of multiple reciprocal interactions between the maternal and the fetal-placental systems. The immune response must warrant the pregnancy outcome (including tolerance to paternal antigens), but at the same time, efficiently respond to pathogenic challenges. Enterotoxigenic Escherichia coli (ETEC) strains are a major cause of illness and death in neonatal and recently weaned pigs. This review aims to give an overview of the current rationale on the maternal vaccination strategies for the protection of the newborn pig against ETEC. Newborn piglets are immunodeficient and naturally dependent on the maternal immunity transferred by colostrum for protection—a maternal immunity that can be obtained by vaccinating the sow during pregnancy. Our current knowledge of the interactions between the pathogen strategies, virulence factors, and the host immune system is aiding the better design of vaccination strategies in this particular and challenging host status. Challenges include the need for better induction of immunity at the mucosal level with the appropriate use of adjuvants, able to induce the most appropriate and long-lasting protective immune response. These include nanoparticle-based adjuvants for oral immunization. Experiences can be extrapolated to other species, including humans.

An investigation into the effects of maternal supplementation with excess iodine on the mechanisms and impacts of reduced IgG absorption in the lamb postpartum

An experiment was conducted to determine: (1) the effect of excess maternal I supplementation on the thyroid hormone status of the ewe and her progeny; (2) potential mechanisms underpinning the failure of passive transfer associated with excess I and (3) the growing lambs' response to natural gastrointestinal infection. Twin-bearing ewes received one of two treatments (n 32/treatment group): basal diet (C) or C plus 26·6 mg of iodine/ewe per d (I), supplied as calcium iodate. Ewes were individually fed from day 119 of gestation to parturition. Progeny of I ewes had lower (P<0·01) serum IgG concentrations from 24 h to 28 d postpartum but higher serum IgG concentrations at day 70 postpartum (P<0·05). I supplementation increased the relative expression of Fc receptor, IgA, IgM high affinity and polymeric Ig receptor in the ileum of the lamb at 24 h postpartum; however, thyroid hormone receptor-β (THRB) and β-2-microglobulin (B2M) expression declined (P<0·05). Progeny of I ewes had higher growth rates to weaning (P<0·05) and lower faecal egg count (FEC) for Nematodirus battus (P<0·05) between weeks 6 and 10 postpartum. In conclusion, excess maternal I supplementation negatively affected the thyroid hormone status, serum IgG concentration, ileal morphology and the gene expression of THRB and B2M in the ileum and ras-related protein (RAB) RAB25 and the mucin gene (MUC) MUC1 in the duodenum of the lamb postpartum. These effects were followed by an enhancement of average daily gain and lower N. battus FEC in the pre-weaning period of I-supplemented lambs.

Passive immunisation, an old idea revisited: Basic principles and application to modern animal production systems

Immunisation by administration of antibodies (immunoglobulins) has been known for more than one hundred years as a very efficient means of obtaining immediate, short-lived protection against infection and/or against the disease-causing effects of toxins from microbial pathogens and from other sources. Thus, due to its rapid action, passive immunisation is often used to treat disease caused by infection and/or toxin exposure. However immunoglobulins may also be administered prior to exposure to infection and/or toxin, although they will not provide long-lasting protection as is seen with active immunisation (vaccination) in which an immunological memory is established by controlled exposure of the host to the pathogen in question. With multi-factorial infectious diseases in production animals, especially those that have proven hard to control by vaccination, the potential of passive immunisation remains big. This review highlights a number of examples on the use of passive immunisation for the control of infectious disease in the modern production of a range of animals, including pigs, cattle, sheep, goat, poultry and fish. Special emphasis is given on the enablement of passive immunisation strategies in these production systems through low cost and ease of use as well as on the sources, composition and purity of immunoglobulin preparations used and their benefits as compared to current measures, including vaccination (also comprising maternal vaccination), antibiotics and feed additives such as spray-dried plasma. It is concluded that provided highly efficient, relatively low-price immunoglobulin products are available, passive immunisation has a clear role in the modern animal production sector as a means of controlling infectious diseases, importantly with a very low risk of causing development of bacterial resistance, thus constituting a real and widely applicable alternative to antibiotics.

Quarter variation and correlations of colostrum albumin, immunoglobulin G1 and G2 in dairy cows

A high variation in immunoglobulin G1 (IgG1) concentration in first milked quarter colostrum has been reported, but BSA quarter colostrum variation is not known. The occurrence of serum albumin in milk has been attributed to increased blood-milk barrier penetration. Reports of serum albumin binding to the Fc Receptor of the neonate, the receptor thought to be responsible for IgG1 transcytosis, suggested that a correlation with the appearance of IgG1 in colostrum of dairy cows was likely. The objective of the study was to establish the quarter colostrum concentration and mass of immunoglobulins and serum albumin. First colostrum was quarter collected within 4 h of parturition from healthy udders of 31 multiparous dairy cows. Individual quarter colostrum weight was determined and a sample of each was frozen for subsequent analysis. Concentrations of immunoglobulin G1, G2, and BSA were measured by ELISA and total mass of components was calculated. In addition, colostrum was also analysed for L-lactate dehydrogenase activity. Analysis of concentration and mass of BSA, immunoglobulin G1, G2 established that the quarter variations were different by cow, quarter and quarter within cow. Partial correlations corrected for colostrum weight indicated that BSA and IgG2 concentration and mass are closely correlated while that of BSA and IgG1 concentration and mass exhibited no correlation suggesting that BSA and IgG1 may have different transport mechanisms. Interestingly, immunoglobulin G1 and G2 concentration and mass exhibited strong correlations suggesting that also some unknown mechanism of immunoglobulin G2 appearance in colostrum is occurring. Finally, no measured protein exhibited any correlation with the activity of lactate dehydrogenase in colostrum.

Iodine supplementation of the pregnant dam alters intestinal gene expression and immunoglobulin uptake in the newborn lamb

Excess iodine intake by the pregnant dam reduces lamb serum antibody concentration, specifically immunoglobulin G (IgG). An experiment was conducted to investigate the mechanisms under pinning the reduced serum IgG concentration at 24 h postpartum in the progeny of iodine supplemented dams. Forty-five mature twin bearing ewes (n=15/treatment) were allocated to one of three dietary treatments as follows: basal diet (Control); basal diet plus 26.6 mg of iodine per ewe per day as calcium iodate (CaIO3); or potassium iodide (KI). Ewes were individually housed and fed from d 119 of gestation until parturition. All lambs received colostrum at 1, 10 and 18 h postpartum via stomach tube. At 1 h postpartum lambs from the control and an iodine supplemented treatment (n=10 per treatment from control and CaIO3) were euthanised before colostrum consumption and ileal segments isolated to determine the gene expression profile of a panel of genes identified as having a role in antibody transfer. Preceding euthanasia, lambs were blood sampled for determination of serum IgG, total thyroxine and free tri-iodothyronine concentrations. Progeny of CaIO3 supplemented dams had lower tri-iodothyronine concentrations (P<0.01) at 1 h postpartum and lower serum IgG concentrations (P<0.001) at 24 h postpartum when compared with the progeny of control dams. Iodine (CaIO3) supplementation of the dam increased the relative expression (P<0.05) of the B2M, PIGR and MYC genes in the ileum of the lamb, before colostrum consumption; while the expression of THRB declined when compared with the progeny of C dams (P<0.01). In conclusion, the results of this study show that it is the actual inclusion of excess iodine in the diet of the ewe, regardless of the carrier element, that negatively affects passive transfer in the newborn lamb. This study presents novel data describing the relationship between maternal iodine nutrition and its effect on the thyroid hormone status and subsequent gene expression in the newborn lamb; which results in a failure of passive transfer and a decline in serum IgG concentration.

Maternal immunity enhances systemic recall immune responses upon oral immunization of piglets with F4 fimbriae

F4 enterotoxigenic Escherichia coli (ETEC) cause diarrhoea and mortality in piglets leading to severe economic losses. Oral immunization of piglets with F4 fimbriae induces a protective intestinal immune response evidenced by an F4-specific serum and intestinal IgA response. However, successful oral immunization of pigs with F4 fimbriae in the presence of maternal immunity has not been demonstrated yet. In the present study we aimed to evaluate the effect of maternal immunity on the induction of a systemic immune response upon oral immunization of piglets. Whereas F4-specific IgG and IgA could be induced by oral immunization of pigs without maternal antibodies and by intramuscular immunization of pigs with maternal antibodies, no such response was seen in the orally immunized animals with maternal antibodies. Since maternal antibodies can mask an antibody response, we also looked by ELIspot assays for circulating F4-specific antibody secreting cells (ASCs). Enumerating the F4-specific ASCs within the circulating peripheral blood mononuclear cells, and the number of F4-specific IgA ASCs within the circulating IgA⁺ B-cells revealed an F4-specific immune response in the orally immunized animals with maternal antibodies. Interestingly, results suggest a more robust IgA booster response by oral immunization of pigs with than without maternal antibodies. These results demonstrate that oral immunization of piglets with F4-specific maternal antibodies is feasible and that these maternal antibodies seem to enhance the secondary systemic immune response. Furthermore, our ELIspot assay on enriched IgA⁺ B-cells could be used as a screening procedure to optimize mucosal immunization protocols in pigs with maternal immunity.

Impact of Infection Dose and Previous Serum Antibodies against the Locus of Enterocyte Effacement Proteins on Escherichia coli O157:H7 Shedding in Calves following Experimental Infection

Escherichia coli O157:H7 is the main causative agent of haemolytic uremic syndrome. Cattle are the main reservoir of these bacteria, and have been shown to develop immune response to colonization. Our aim was to investigate the faecal shedding pattern of E. coli O157:H7 in calves challenged intragastrically with either 10⁸ or 10¹⁰ CFU, as well as the ability of specific preexisting antibodies to reduce shedding of the pathogen. Shedding was analysed by direct counting as well as enrichment of rectoanal mucosal swabs. Statistical analysis was performed using a linear model for repeated measures with and without the inclusion of preexisting antibodies against the carboxy-terminal fraction of intimin-γ (γ-intimin C280) as a covariable. Results suggest that there is a statistical difference in the area under the shedding curves between both doses for 14 as well as 28 days after challenge (p = 0.0069 and 0.0209, resp.). This difference is increased when the prechallenge antibodies are taken into account (p = 0.0056 and 0.0185). We concluded that the bacterial dose influences shedding on calves experimentally challenged and that preexisting antibodies against E. coli O157:H7 γ-intimin C280 could partially reduce faecal excretion.

A longitudinal study of factors influencing the result of a Mycobacterium avium ssp. paratuberculosis antibody ELISA in milk of dairy cows

The influence of milk yield and milk composition on the diagnosis of Mycobacterium avium ssp. paratuberculosis (MAP) by milk ELISA in the context of the total IgG secretion patterns in milk throughout lactation and serum concentrations were investigated. A 2-yr trial was performed in which 1,410 dairy cows were sampled monthly and MAP milk ELISA status and milk yield and composition were determined. Data were analyzed by mixed model analysis. Milk yield was found to significantly influence ELISA results expressed as sample-to-positive (S/P) ratios. For each 5-kg increase in milk, the S/P ratio has to be multiplied by 0.89; therefore, high milk yield can change the MAP milk ELISA outcome of a cow in early infection from positive to negative. Parity influenced ELISA outcome significantly, indicating that cows with a parity >1 are more likely to be identified by milk testing. Also, herd was an important predictor, showing that herd prevalence influences the milk ELISA strongly. Other factors influencing the S/P ratios were protein concentration, somatic cell count, and days in milk. The IgG concentration and mass excreted per day were determined longitudinally in a subset of 41 cows of which samples and data of a complete lactation were available. Again, the IgG concentration in milk was mainly influenced by milk yield. The total IgG mass secreted per day in milk was found to be relatively constant, with a mean of 8.70 ± 5.38 g despite an increasing IgG concentration in serum at the same time. The variation of IgG concentration in milk can be mainly attributed to dilution through changes in milk yield. This supports the assumption that concentrations of MAP-specific antibodies are influenced by changes in milk yield similarly. In conclusion, we confirmed that antibody concentrations, and therefore MAP ELISA outcome, were influenced by milk yield, herd, and parity. To enhance performance, milk ELISA tests should either be performed in early or late lactation, when milk yield is low. From a management perspective, sampling should be done during early lactation before cows are bred again. Based on the slow progressive infection dynamics, only first-parity cows should be preferentially tested at the end of their first lactation to avoid false-negative results.

Plant-based solutions for veterinary immunotherapeutics and prophylactics

An alarming increase in emergence of antibiotic resistance among pathogens worldwide has become a serious threat to our ability to treat infectious diseases according to the World Health Organization. Extensive use of antibiotics by livestock producers promotes the spread of new resistant strains, some of zoonotic concern, which increases food-borne illness in humans and causes significant economic burden on healthcare systems. Furthermore, consumer preferences for meat/poultry/fish produced without the use of antibiotics shape today's market demand. So, it is viewed as inevitable by the One Health Initiative that humans need to reduce the use of antibiotics and turn to alternative, improved means to control disease: vaccination and prophylactics. Besides the intense research focused on novel therapeutic molecules, both these strategies rely heavily on the availability of cost-effective, efficient and scalable production platforms which will allow large-volume manufacturing for vaccines, antibodies and other biopharmaceuticals. Within this context, plant-based platforms for production of recombinant therapeutic proteins offer significant advantages over conventional expression systems, including lack of animal pathogens, low production costs, fast turnaround and response times and rapid, nearly-unlimited scalability. Also, because dried leaves and seeds can be stored at room temperature for lengthy periods without loss of recombinant proteins, plant expression systems have the potential to offer lucrative benefits from the development of edible vaccines and prophylactics, as these would not require "cold chain" storage and transportation, and could be administered in mass volumes with minimal processing. Several biotechnology companies currently have developed and adopted plant-based platforms for commercial production of recombinant protein therapeutics. In this manuscript, we outline the challenges in the process of livestock immunization as well as the current plant biotechnology developments aimed to address these challenges.

Exploiting ovine immunology to improve the relevance of biomedical models

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Sheep make a valuable contribution to immunology research.

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Lessons to be learned from studying infections in the natural host.

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Factors to consider when selecting biomedical models.

Animal models of human disease are important tools in many areas of biomedicine; for example, in infectious disease research and in the development of novel drugs and medical devices. Most studies involving animals use rodents, in particular congenic mice, due to the availability of a wide number of strains and the ease with which they can be genetically manipulated. The use of mouse models has led to major advances in many fields of research, in particular in immunology but despite these advances, no animal model can exactly reproduce all the features of human disease. It is increasingly becoming recognised that in many circumstances mice do not provide the best model and that alternative species may be more appropriate. Here, we describe the relative merits of sheep as biomedical models for human physiology and disease in comparison to mice, with a particular focus on reproductive and respiratory pathogens.

Maternal antibodies: clinical significance, mechanism of interference with immune responses, and possible vaccination strategies

Neonates have an immature immune system, which cannot adequately protect against infectious diseases. Early in life, immune protection is accomplished by maternal antibodies transferred from mother to offspring. However, decaying maternal antibodies inhibit vaccination as is exemplified by the inhibition of seroconversion after measles vaccination. This phenomenon has been described in both human and veterinary medicine and is independent of the type of vaccine being used. This review will discuss the use of animal models for vaccine research. I will review clinical solutions for inhibition of vaccination by maternal antibodies, and the testing and development of potentially effective vaccines. These are based on new mechanistic insight about the inhibitory mechanism of maternal antibodies. Maternal antibodies inhibit the generation of antibodies whereas the T cell response is usually unaffected. B cell inhibition is mediated through a cross-link between B cell receptor (BCR) with the Fcγ-receptor IIB by a vaccine-antibody complex. In animal experiments, this inhibition can be partially overcome by injection of a vaccine-specific monoclonal IgM antibody. IgM stimulates the B cell directly through cross-linking the BCR via complement protein C3d and antigen to the complement receptor 2 (CR2) signaling complex. In addition, it was shown that interferon alpha binds to the CD21 chain of CR2 as well as the interferon receptor and that this dual receptor usage drives B cell responses in the presence of maternal antibodies. In lieu of immunizing the infant, the concept of maternal immunization as a strategy to protect neonates has been proposed. This approach would still not solve the question of how to immunize in the presence of maternal antibodies but would defer the time of infection to an age where infection might not have such a detrimental outcome as in neonates. I will review successful examples and potential challenges of implementing this concept.

Effect of continuous milking on immunoglobulin concentrations in bovine colostrum

Continuous milking is defined as a dairy cattle management system without a planned dry period for cows in late gestation. Continuous milking has been described to reduce health problems common in periparturient cattle, but may affect colostrum immunoglobulin (Ig) concentration and subsequently calf health. This study reports the influence of continuous milking on Ig concentrations of bovine colostrum in commercial dairy farms. Colostrum Ig concentrations of 227 cows from 13 herds were quantified with a quantitative ELISA for IgG, IgG1, IgG2, IgA and IgM. Colostrum samples of continuous milked (CM) cows (n=38) were compared with colostrum samples of cows (n=189) after a traditional dry period (DP) of at least 42 days.

RESULTS

indicated that colostrum Ig concentration was significantly lower in continuous milking systems where IgG, IgG1, IgG2, IgA and IgM concentrations were reduced by half compared with cows that had a planned dry period. When relating the results from this study to recommendations for colostrum management it can be concluded that although colostrum Ig concentrations are significantly lower in a continuous milking management system an adequate passive immune transfer can still be achieved based on colostrum quality provided colostrum feeding management is optimal.

Colostrogenesis during an induced lactation in dairy cattle

Colostrum immunoglobulin G (IgG) is of major importance for the newborn calf because epitheliochorial placentae do not provide transport in utero. The formation of colostrum occurs in the later stages of pregnancy. Our objectives were to induce lactation in non-pregnant dairy cows and (i) to determine the changes of IgG in serum and mammary secretions during the induction process and (ii) to establish α-lactalbumin (αLA) and prolactin (Prl) alterations to monitor the changing mammary epithelial tight junction status and development pattern. Estradiol-17β (E2) and progesterone (P4) injections in a 1-7 days series were combined with a 3-day injection series (day 21-23) of dexamethasone (DEX). Blood and both front quarter secretion samples were collected daily. Milking started 24 days after the start of the experiment. Results show that the mammary secretory IgG1 was increased at >7 days after the start of steroid injections and depicted a bimodal pattern reaching a high of 16 mg/ml at 21 day compared with 3.2 mg/ml in the serum. There was a small increase in secretory IgG2 that did not correlate with tight junction status, but never reached the serum concentration. The injections of DEX resulted in constriction of tight junctions. Secretory αLA was immediately increased with steroid injections, dropped precipitously after 7 days and then began a steady increase until the start of milking. Changes in serum αLA are related to mammary tight junctions while serum Prl gradually increased from 30 to >60 ng/ml after the steroid injections stopped. These results provide insights into the mechanisms and timing of colostrogenesis during an induced lactation protocol.

Stimulation and analysis of the immune response in calves from vaccinated pregnant cows

The effect of vaccinating pregnant cows with an inactivated vaccine against Mannheimia haemolytica, BRSV and PI3V infections on selected immune responses in their offspring was examined. Blood samples were collected weekly for 12 weeks from six newborn calves from each of vaccinated (experimental) and unvaccinated (control) dams. Specific antibodies to M. haemolytica, BRSV and PI3V and mean values of IgA, IgG concentrations were significantly higher in the experimental calves compared with the controls. However, specific antibody titres to adenovirus type 3, BHV1 and BVDV in the experimental calves had constant levels while the control group levels changed. The IgM, Hp and SAA concentrations generally increased until week 8 in the experimental group, but the control group titres became higher after week 9. This study demonstrates that specific immunisation of cows pre-partum significantly stimulated parameters associated with immunity and it also controlled the acute phase response intensity in their offspring. Therefore the vaccination of dams may provide additional antibody protection against infection to their offspring.

Colostrogenesis: IgG1 transcytosis mechanisms

Biological transport of intact proteins across epithelial cells has been documented for many absorptive and secretory tissues. Immunoglobulins were some of the earliest studied proteins in this category. The transcellular transport (transcytosis) of immunoglobulins in neonatal health and development has been recognized; the process is especially significant with ungulates because they do not transcytose immunoglobulins across the placenta to the neonate. Rather, they depend upon mammary secretion of colostrum and intestinal absorption of immunoglobulins in order to provide intestinal and systemic defense until the young ungulate develops its own humoral defense mechanisms. The neonatal dairy calf's ability to absorb immunoglobulins from colostrum is assisted by a ~24 h "open gut" phenomenon where large proteins pass the intestinal epithelial cells and enter the systemic system. However, a critical problem recognized for newborn dairy calves is that an optimum mass of colostrum Immunoglobulin G (IgG) needs to be absorbed within that 24 h window in order to provide maximal resistance to disease. Many calves do not achieve the optimum because of poor quality colostrum. While many studies have focused on calf absorption, the principal cause of the problem resides with the extreme variation (g to kg) in the mammary gland's capacity to transfer blood IgG1 into colostrum. Colostrum is a unique mammary secretory product that is formed during late pregnancy when mammary cells are proliferating and differentiating in preparation for lactation. In addition to the transcytosis of immunoglobulins, the mammary gland also concentrates a number of circulating hormones into colostrum. Remarkably, the mechanisms in the formation of colostrum in ungulates have been rather modestly studied. The mechanisms and causes of this variation in mammary gland transcytosis of IgG1 are examined, evaluated, and in some cases, explained.

Structural changes of mucous membrane and the presence of immunoglobulins in small intestines of neonatal pigs

The structure of the small intestine of neonatal pigs has an important effect on immunoglobulin absorption. The aim of the experiment was to observe changes in the mucous membrane and the presence of immunoglobulins in the intestines of piglets during the first hours of their postnatal lives. In total, 80 piglets of the Large White breed were divided into two groups of 40 pigs. One group (control) came from an infection-free breeding, the other (experimental) group came from a breeding with the reproduction and respiration syndrome of pigs. Samples (n = 80) of duodenum, jejunum and ileum were taken at intervals of 0, 3, 6 and 12 h after colostrum intake in order to carry out histological tests. Primary pig antibodies were detected by immunohistochemical staining. The low content of immunoglobulins IgG, IgA and IgM was detected in all segments of intestines of precolostral piglets. Difference (P < 0.05) in size of the mucous membrane was found in the duodenum at the interval of 0, 3 and 6 h (46.03%), in the jejunum at 0 and 12 h (45.98%) and in favour of the control group. Compared to the control group, more Ig (P < 0.01) antibodies were observed in the experimental group: in the duodenum IgG at 12 h (37.22 vs. 10.81%), IgA, 6 h (43.29 vs. 16.71%), IgM, 12 h (25.29 vs. 8.40%), in the jejunum at IgG 12 h (23.97 vs. 9.96%), IgA, 0 h (0.48 vs. 0.37%) and IgM, 3 h (21.80 vs. 10.10%), in the ileum IgG, 0 h (0.38 vs. 0.29%), IgA, 3 h (20.46 vs. 6.45%), IgM, 3 h (31.5 vs. 12.29%). We can conclude that the colostrum intake and the presence of reproduction and respiration syndrome of pigs resulted in changes of microscopic structures of intestines as well as in the presence of Ig in piglet intestines. These mucosal changes significantly affect the development of passive immunity in piglets in the postnatal period.

Colostrogenesis: candidate genes for IgG1 transcytosis mechanisms in primary bovine mammary epithelial cells

Bovine colostrogenesis is distinguished by the specific transfer of IgG1 from the blood to mammary secretions. The process has been shown to be initiated by hormones and occurs during the last weeks of pregnancy when steroid concentrations of estradiol (E2 ) and progesterone (P4 ) are highly elevated. Rodent intestinal uptake of immunoglobulin G is mediated by a receptor termed Fc fragment of IgG, Receptor, Transporter, alpha (FcGRT) and supported by light chain Beta-2-Microglobulin (β2M). We hypothesized that steroid hormone treatments (E2 and P4 ) of bovine mammary epithelial cells in vitro would induce up-regulation of IgG1 transcytosis candidate gene mRNA expression suggesting involvement in IgG1 transcytosis. Two different primary bovine mammary epithelial cell cultures were cultured on plastic and rat tail collagen and treated with hormonal combinations (steroids/lactogenic hormones). Evaluated mRNA components were bLactoferrin (bLf: a control), bFcGRT, β2M, and various small GTPases; the latter components are reported to direct endosomal movements in eukaryotic cells. All tested transcytosis components showed strong expression of mRNA in the cells. Expression of bFcGRT, bRab25 and bRhoB were significantly up-regulated (p < 0.05) by steroid hormones. bRab25 and bRhoB showed increased expression by steroid treatments, but also with lactogenic hormones. Analysis for the oestrogen receptor (ER) mRNA was mostly negative, but 25% of the cultures tested exhibited weak expression, while the progesterone receptor (PR) mRNA was always detected. bRab25 and bRhoB and likely bFcGRT are potential candidate genes for IgG1 transcytosis in bovine mammary cells.

The evolutionary basis for differences between the immune systems of man, mouse, pig and ruminants

Studying the pathogenesis of an infectious disease like colibacillosis requires an understanding of the responses of target hosts to the organism both as a pathogen and as a commensal. The mucosal immune system constitutes the primary line of defence against luminal micro-organisms. The immunoglobulin-superfamily-based adaptive immune system evolved in the earliest jawed vertebrates, and the adaptive and innate immune system of humans, mice, pigs and ruminants co-evolved in common ancestors for approximately 300 million years. The divergence occurred only 100 mya and, as a consequence, most of the fundamental immunological mechanisms are very similar. However, since pressure on the immune system comes from rapidly evolving pathogens, immune systems must also evolve rapidly to maintain the ability of the host to survive and reproduce. As a consequence, there are a number of areas of detail where mammalian immune systems have diverged markedly from each other, such that results obtained in one species are not always immediately transferable to another. Thus, animal models of specific diseases need to be selected carefully, and the results interpreted with caution. Selection is made simpler where specific host species like cattle and pigs can be both target species and reservoirs for human disease, as in infections with Escherichia coli.

A simple novel measure of passive transfer of maternal immunoglobulin is predictive of preweaning mortality in piglets

Two factors that contribute to preweaning mortality in piglets are the initiation of lactation by sows and their ability to nurse their piglets. The objective of this study was to determine if the quantification of the transfer of immunoglobulins (Igs) from sow to piglet could act as a measure of these sow factors in terms of their influence on preweaning mortality. To measure passive transfer, a simple, rapid Ig immunocrit method was developed. For validation, the smallest piglets from 204 gilts were sacrificed on day 1 after birth and blood was collected. Piglet serum Ig concentrations were measured three ways: (1) by protein A sepharose precipitation, SDS-PAGE, and densitometry of the IgG heavy chain; (2) by precipitation of Ig with (NH(4))(2)SO(4) followed by spectrophotometric measurement; and (3) by precipitation of Ig with (NH(4))(2)SO(4) and measurement of the ratio of precipitate to sample volume using a hematocrit microcapillary (the Ig immunocrit method). Results from the (NH(4))(2)SO(4) methods correlated (r=0.86) with those obtained using SDS-PAGE. Day 1 weights and immunocrit ratios and preweaning survival data were then collected from every piglet from first (n=90), and second (n=145) parity sows. Bodyweight and immunocrit ratios accounted for 4.8% and 16.7% (P<0.01) of the variation in preweaning mortality, respectively. Litter average immunocrit ratios were not correlated with preweaning mortality. In conclusion, the Ig immunocrit method is a simple, rapid measure of passive transfer from sow to piglet, and is useful in assessing the initiation of colostrum and the nursing ability of sows, and the effect of these events on preweaning piglet mortality.

Commensal bacteria coated by secretory immunoglobulin A and immunoglobulin G in the gastrointestinal tract of pigs and calves

A large amount of secretory immunoglobulin A (S-IgA) is secreted in the alimentary tract of mammals. It has been reported that S-IgA coats a portion of commensal intestinal bacteria in human and mouse. However, S-IgA-coated bacteria have not been studied in pigs and calves. In this study, we evaluated the distribution of S-IgA-coated commensal intestinal bacteria in each portion of the gastrointestinal tracts of pigs and calves. Immunoglobulin G (IgG)-coated bacteria were also analyzed because a considerable amount of IgG is secreted in the gastrointestinal tracts of pigs, and in particular, calves. S-IgA- or IgG-coated bacteria were detected in all the segments of the gastrointestinal tracts of pigs and calves. The proportion of S-IgA-coated bacteria to total bacteria (i.e. S-IgA coating ratio) varied in the segments of the gastrointestinal tract in pigs, whereas those of calves were nearly the same throughout the gastrointestinal tract. The S-IgA and IgG coating ratios were higher in pigs than in calves for all segments of the gastrointestinal tract.