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

Acceptable Young Calf Vaccination Strategies-What, When, and How?

Vaccination is an important component for the prevention and control of disease in calves. Too often vaccines are viewed as a catch-all solution for management and nutrition errors; the "best" vaccine can never overcome these deficiencies. Proper vaccination in the young calf and developing heifer is the key to long-term development of a productive dairy cow. To actually immunize animals, animals must be able to respond to vaccines, which is dependent on the level of animal husbandry. Each vaccine program needs to be designed based on animal flow, actual "disease" threats, and labor on the farm.

The gastrointestinal frontier: IgA and viruses

Viral gastroenteritis is one of the leading causes of diseases that kill ~2.2 million people worldwide each year. IgA is one of the major immune effector products present in the gastrointestinal tract yet its importance in protection against gastrointestinal viral infections has been difficult to prove. In part this has been due to a lack of small and large animal models in which pathogenesis of and immunity to gastrointestinal viral infections is similar to that in humans. Much of what we have learned about the role of IgA in the intestinal immune response has been obtained from experimental animal models of rotavirus infection. Rotavirus-specific intestinal IgA appears to be one of the principle effectors of long term protection against rotavirus infection. Thus, there has been a focus on understanding the immunological pathways through which this virus-specific IgA is induced during infection. In addition, the experimental animal models of rotavirus infection provide excellent systems in which new areas of research on viral-specific intestinal IgA including the long term maintenance of viral-specific IgA.

Intestinal IgA response and immunity to rotavirus infection in normal and antibody-deficient chickens

Rotavirus inoculation by oesophageal cannulation resulted in subclinical infection without decreasing intestinal D-xylose absorption in both intact and embryonally bursectomised, antibody-deficient (EBx) 8-week-old specific-pathogen-free chickens. In intact chickens, rotavirus-specific IgM, IgG and IgA responses were detected in serum, while the intestinal antibody response consisted almost entirely of IgA Serum IgG and intestinal IgA levels were increased for at least 70 days following a single inoculation with the virus. Intact chickens recovered from a primary rotavirus infection between 4 and 14 days post inoculation (dpi) and developed resistance to homotypic challenge between 14 and 28 dpi. These responses were only slightly delayed in EBx birds, which recovered from primary infection between 8 and 28 dpi and developed resistance between 14 and 42 dpi. This suggested that the intestinal IgA response in chickens participated in both recovery from and resistance to rotavirus infection, but that it was not the only mediator of recovery and resistance.

Neonatal immune development in the calf and its impact on vaccine response

In this article we cover the immunologic response as it develops, the components of passive immunity, and the immune response of young calves. We discuss interference from maternal immunity in the development of specific immunity and vaccine strategies for developing protection against pathogens in calves.

Modulation by colostrum-acquired maternal antibodies of systemic and mucosal antibody responses to rotavirus in calves experimentally challenged with bovine rotavirus

The effect of colostral maternal antibodies (Abs), acquired via colostrum, on passive protection and development of systemic and mucosal immune responses against rotavirus was evaluated in neonatal calves. Colostrum-deprived (CD) calves, or calves receiving one dose of pooled control colostrum (CC) or immune colostrum (IC), containing an IgG1 titer to bovine rotavirus (BRV) of 1:16,384 or 1:262,144, respectively, were orally inoculated with 10^5.5 FFU of IND (P[5]G6) BRV at 2 days of age. Calves were monitored daily for diarrhea, virus shedding and anti-BRV Abs in feces by ELISA. Anti-rotavirus Ab titers in serum were evaluated weekly by isotype-specific ELISA and virus neutralization (VN). At 21 days post-inoculation (dpi), all animals were euthanized and the number of anti-BRV antibody secreting cells (ASC) in intestinal and systemic lymphoid tissues were evaluated by ELISPOT. After colostrum intake, IC calves had significantly higher IgG1 serum titers (GMT=28,526) than CC (GMT=1195) or CD calves (GMT<4). After BRV inoculation, all animals became infected with a mean duration of virus shedding between 6 and 10 days. However, IC calves had significantly fewer days of diarrhea (0.8 days) compared to CD and CC calves (11 and 7 days, respectively). In both groups receiving colostrum there was a delay in the onset of diarrhea and virus shedding associated with IgG1 in feces. In serum and feces, CD and CC calves had peak anti-BRV IgM titers at 7 dpi, but IgA and IgG1 responses were significantly lower in CC calves. Antibody titers detected in serum and feces were associated with circulation of ASC of the same isotype in blood. The IC calves had only an IgM response in feces. At 21 dpi, anti-BRV ASC responses were observed in all analyzed tissues of the three groups, except bone marrow. The intestine was the main site of ASC response against BRV and highest IgA ASC numbers. There was an inverse relationship between passive IgG1 titers and magnitude of ASC responses, with fewer IgG1 ASC in CC calves and significantly lower ASC numbers of all isotypes in IC calves. Thus, passive anti-BRV IgG1 negatively affects active immune responses in a dose-dependent manner. In ileal Peyer’s patches, IgM ASC predominated in calves receiving colostrum; IgG1 ASC predominated in CD calves. The presence in IC calves of IgG1 in feces in the absence of an IgG1 ASC response is consistent with the transfer of serum IgG1 back into the gut contributing to the protection of the intestinal mucosa.

Measurement of antirotavirus IgM/IgA/IgG responses in the serum samples of Indian children following rotavirus diarrhoea and their mothers

Rotavirus specific, serum IgM/IgA/IgG levels among hospitalized children and their respective mothers were determined. Children were grouped as having rotavirus diarrhoea (RVD) and non-rotavirus diarrhoea (NRVD) on the basis of fecal excretion measured by ELISA and RT-PCR. Although IgM seropositivity was observed among children of both the groups, it was significantly higher in the acute as well as convalescent phase serum samples (P < 0.05 for both) of RVD group. Five out of ten acute sera from the NRVD group were positive for IgM and seven showed IgA/IgG seroconversion indicating rotavirus infection among these children in the past. It was noted that, three out of 24 mothers' sera from RVD group, showed presence of IgM in the serum collected during convalescence of their children. The observation suggests, subclinical rotavirus infection among mothers probably contacted from their children. This is supported by the seroconversion for IgA/IgG among these three mothers. Such a phenomenon was not noticed among the mothers from NRVD group. In general, IgA positivity did not vary significantly among the children from both the groups. IgA seropositivity was significantly higher (P < 0.001) from children of RVD group as compared to healthy group of children following rotavirus infection. From RVD group, all the child patients and 12 mothers out of 24 (50%) showed IgA/IgG seroconversion. None of the mothers from NRVD group showed seroconversion. Serum samples of healthy children and adults, showed IgM positivity at equal level (10%), but a significant difference (P < 0.01) was observed in IgA positivity. In conclusion, subclinical transmission of rotavirus infection from children to their mothers may occur. Seroconversion alone cannot be considered as a marker of rotavirus diarrhoea in children. Moreover, about 40-50% of subjects lacked rotavirus specific IgA at protective levels, making them susceptible to rotavirus infection.

Passive immunity against rotavirus in infants

Passive immunity against a variety of gastrointestinal infections, using orally administered human antibodies, has been tried in a number of clinical trials. Recently, antibodies from other species such as cows and chickens, which have shown efficacy in experimental animal systems, have also been tried in humans. This review summarizes published data on the use of immunoglobulin-containing preparations for prophylaxis and therapy against rotavirus infections in infants and children, and directions for their future use are suggested.

Effect of colostral ingestion on immunoglobulin-positive cells in calves

The importance of colostrum for passive transfer of maternal immunoglobulin in calves is well established. Colostrum is thought to have additional generalized and antigen-specific immunomodulatory activities, of which the downregulation of endogenous immunoglobulin production is best documented. The objective of this study was to examine whether ingestion of colostrum altered the B cell subpopulations in the lymph nodes of newborn calves. Calves were fed one gallon of either fresh colostrum (Group A, n = 5), milk replacer (Group B, n = 5) or treated (frozen or irradiated) colostrum (Group D, n = 4) and were euthanized at 36-48 h. An additional 5 calves (Group C, 3 newborn and 2 mid-term fetuses) did not receive any feedings; the neonatal calves were euthanized immediately following birth. Mesenteric and regional lymph nodes from all calves were analyzed by immunocytochemistry using monoclonal antibodies recognizing bovine IgA, IgG1, IgG2, and IgM. Calves from Groups B and C (colostrum deprived, neonates, and fetuses) showed a consistent pattern of IgG1 and IgG2 positive cells scattered individually and in clusters throughout lymph node cortex, paracortex, and cortico-medullary junction. In sharp contrast, no IgG1 and IgG2 positive cells were present in the lymphoid tissues of colostrum fed calves (Groups A or D). Numbers of IgM and IgA positive cells were similarly distributed in all calf groups. These findings demonstrate that colostrum feeding reduces the number of immunoglobulin positive cells in the lymphoid tissues of newborn calves in an isotype-specific manner. This results in the elimination of IgG1 and IgG2 positive cells that are present in both fetuses and newborn calves. This effect is not eliminated by freezing or irradiation, indicating that a non-cellular, cold-stable colostral factor is responsible. Systemically distributed colostral proteins such as immunoglobulin or cytokines are the most likely mediators. The significance of this phenomenon in terms of colostral modulation of calf endogenous antibody production is discussed.

Copro-antibody in calves from dams vaccinated against Salmonella typhimurium

Calves received colostrum either with (positive colostrum) or without (negative colostrum) anti-Salmonella typhimurium antibodies. Regarding the detectability of copro-antibodies, the following observations have been made. In calves that had been given positive colostrum on day 4 post natum (p.n.), copro-antibodies were detectable over 7 days, while in those that had received positive colostrum on day 1 p.n. copro-antibodies were detectable over 45 days. After supplying highly positive colostrum, copro-antibodies were found over a period of 8 weeks, and after supplying weakly positive colostrum, they were found over a period of 5 weeks. It is concluded that serum antibodies are transferred to the intestine for maximum local protection, and that there exists a preference for the intestinal system regarding the distribution of salmonella antibodies. Challenge infection on day 5 p.n. of calves that had received highly positive colostrum resulted in a copro-antibody gap that reached the limit of detectability in two calves that were excreting salmonellas. Challenge infection of calves that had received negative colostrum provoked a local IgM and IgA antibody response.

Isotype-specific antibody responses in sera and mucosal secretions of calves experimentally infected with bovine herpesvirus 1

Enzyme-linked immunosorbent assays (ELISAs) were developed for studying the kinetics of isotype-specific antibody responses in sera, nasal, ocular and genital secretions of calves infected with bovine herpesvirus 1 (BHV1). The BHV1-specific IgM and IgA antibodies were measured in antibody capture assays, and the IgG1 and IgG2 antibodies in indirect double antibody sandwich assays. The ELISAs were shown to be isotype-specific, sensitive and reproducible. Antibodies of all isotypes were able to neutralise the virus in vitro. Calves were infected intranasally with one of seven BHV1 field strains. Nine to 13 days after infection BHV1-specific antibodies of the IgM isotype appeared in serum, nasal and ocular secretions and these were detectable until four weeks after infection. The first IgA antibodies were detected a few days later than the IgM antibodies. In serum the IgA antibodies were no longer detectable after 3 weeks, but these did persist for prolonged periods in mucosal secretions. The calves developed a uniform IgG1 response from 13 days after infection, but the IgG2 response was quite variable; both persisted until the end of the experiment. No antibody responses were detected in genital secretions. There were no marked differences in isotype responses between calves infected with different strains of BHV1.

Immunogenicity in cows of Staphylococcus aureus type 5 capsular polysaccharide-ovalbumin conjugate

Six dairy cows were immunized subcutaneously with purified type 5 capsular polysaccharide (CP5) of Staphylococcus aureus or CP5-ovalbumin conjugate in Freund's incomplete adjuvant. The CP5 antibodies elicited were measured in sera and analysed with regard to isotypes by enzyme-linked immunosorbent assay. At the doses tested, the purified CP5 did not induce a humoral response in the cows. Immunization of two cows with the CP5-ovalbumin conjugate elicited a CP5 antibody response mainly of the IgG2 isotype, which culminated 4 weeks later. A second injection of conjugate, 3 months after the first one, resulted in a rapid and durable anti-CP5 response without exceeding the first antibody peak value. Intramammary infusion of purified CP5 failed to provoke an inflammatory response in the milk of the immunized cows. In contrast, a marked recruitment of cells was recorded in the milk of the sensitized cows after intramammary infusion of ovalbumin. These results demonstrate that injection of CP5-protein carrier conjugate in cows entails both antibody response against CP5 and carrier-specific recruitment of cells in milk of immunized animals.

Toroviruses of animals and humans: a review

Toroviruses are a group of enveloped positive-stranded RNA viruses that cause enteric, respiratory, and perhaps generalized infections in animals and humans. Their name refers to their unique morphological features: an elongated bacilliform core with two rounded ends is surrounded by a membrane that may either tightly adhere to or “shrink-wrap” it, without respecting the capsid's rod shape; in the first instance, straight or curved rhabdovirus-like particles are formed, whereas in the latter a biconcave disk results. Torovirus history is brief: the first representative, Berne virus (BEV), was isolated in Berne, Switzerland, in 1972 from a rectal swab taken from a horse with diarrhea 1 week before it died. BEV is the only equine torovirus isolate that replicates in cell culture; since most molecular data have been obtained with this isolate, BEV has been acknowledged as the torovirus prototype. Recognition of toroviruses as a new group of potentially pathogenic viruses came seven years after the discovery of BEV, when morphologically similar particles were discovered by electron microscopy (EM) in stool specimens from calves with severe diarrhea in a dairy herd in Breda, Iowa. Despite repeated attempts, BRV has not been adapted to the growth in cell or tissue culture, a problem which has hampered its biochemical, bio-physical, and molecular characterization. However, its pathogenesis and pathology have been studied in the experimentally infected gnotobiotic calves, showing that BRV infections may cause gastroenteritis. Recently, Vanopdenbosch et al. reported the isolation of a torovirus-like virus from the respiratory tract of calves with pneumonia, suggesting that both enterotropic and pneumotropic bovine toroviruses exist. Besides the established toroviruses of horses and cattle, torovirus-like particles (TVLPs) have been found by EM in different animal species; torovirus antibodies appear to be widespread in higher vertebrates, indicating that these viruses infect a broad range of animal hosts. The possibility of a torovirus infecting humans was first reported in 1984 and has become more likely in view of the recent data. This chapter is intended to update the information about toroviruses, and to describe the similarities and differences with the related coronaviruses.

In vivo role of lymphocyte subpopulations in the control of virus excretion and mucosal antibody responses of cattle infected with rotavirus

T-cell control of primary rotavirus infection and mucosal antibody responses to rotavirus was studied with monoclonal antibodies (MAb) to deplete gnotobiotic calves of CD4+, CD8+, BoWC1+, or both CD4+ and CD8+ lymphocytes prior to infection with rotavirus. Injection of these MAb produced specific reductions in circulating and tissue lymphocyte subpopulations. Following infection, control calves developed fecal immunoglobulin M (IgM) and IgA antibodies and serum IgM and IgG1 antibodies; there was no IgG2 antibody produced. Anti-CD4-treated calves had reduced fecal and serum antibody responses to rotavirus compared with control calves. The IgM response was less affected than the other isotypes. Calves concurrently injected with MAb to CD4 and CD8 had antibody responses similar to those of calves injected with anti-CD4 antibody alone. No effect on serum or fecal antibody levels was seen when MAb to CD8 or BoWC1 were injected alone. Virus excretion was significantly increased in calves depleted of CD8+ cells. Depletion of CD4+ cells or BoWC1+ cells had no effect on virus excretion. Calves depleted of both CD4+ and CD8+ cells excreted amounts of virus similar to those of calves depleted of CD8+ cells alone. Onset and duration of virus excretion were not affected by any of the MAb treatments. We conclude that a CD8+ cell population is involved in limiting primary rotavirus infection, while CD4+ or BoWC1+ (gamma/delta+ TcR) lymphocytes are not. Furthermore, CD4+ lymphocytes (but not CD8+ or BoWC1+ lymphocytes) were shown to be important in the generation of mucosal, as well as systemic, antibody responses.

The potential of molecular biology for the production of monoclonal antibodies derived from outbred veterinary animals

The protein structure of immunoglobulins and the genetics on the regulation of immunoglobulin expression are reviewed. This basic knowledge has led to the development of systems to produce monoclonal antibodies in eukaryotic or prokaryotic cells. The potential and limitations of molecular biology for the understanding of immunoglobulin regulation and for the production of monoclonal antibodies derived from animals of veterinary importance are discussed.

Isotype antibody response in cows to Streptococcus agalactiae group B polysaccharide-ovalbumin conjugate

Adult dairy cows were immunized with group B antigen (GBA) of Streptococcus agalactiae or GBA coupled to ovalbumin, both emulsified in incomplete Freund adjuvant, and their sera were examined by an enzyme-linked immunosorbent assay measuring bovine immunoglobulin isotypes (immunoglobulin G1 [IgG1], IgG2, and IgM) specific for GBA. All of the cows possessed naturally acquired antibodies against GBA, which implied that primary antibody responses could not be studied. At the highest dose tested (200 micrograms), free GBA elicited a slight increase in antibody titers only in the IgM isotype, to which most of the naturally acquired antibodies to GBA belonged. A second administration of antigen was not more effective. The conjugate was able to induce a strong humoral response against GBA, particularly in the IgG1 and IgG2 subisotypes, and a second injection of the conjugate induced a doubling of the peak antibody titers. Therefore, conjugation of GBA to a protein carrier markedly improved the antibody response, which showed the main characteristics of T-cell dependency. The opsonic activity of serum against an unencapsulated strain of S. agalactiae was reinforced by the immunization with the conjugate.

The effect of dexamethasone-induced immunosuppression on the development of faecal antibody and recovery from and resistance to rotavirus infection

Rotavirus-naive and rotavirus-immune gnotobiotic calves were treated with high doses of dexamethasone (DX) to suppress the immune system. Calves were then infected with a virulent rotavirus inoculum, J-160, to investigate the role of immune responses both in recovery from primary rotavirus infection and in resistance to secondary rotavirus infection. Treatment of calves with DX markedly suppressed in vitro responsiveness of peripheral blood lymphocytes to mitogens within 48 h of the start of DX treatment. Suppression was similar in rotavirus-naive and rotavirus-immune calves. In contrast, the effect of DX treatment on specific antibody responses differed depending on when DX treatment started in relation to rotavirus infection. When DX treatment commenced prior to primary rotavirus infection both systemic and local specific antibody responses were inhibited. These calves, in which mitogen and antibody responses were suppressed, exhibited greater clinical signs than did control calves after infection with virulent rotavirus, but virus excretion was affected in only one of the two calves. When DX treatment was started after primary rotavirus infection but before secondary infection, systemic and local antibody responses to the primary infection and to the challenge infection were not affected. These calves resisted challenge with virulent virus as did DX-untreated rotavirus-immune calves, even though mitogen responses were suppressed. We conclude that in a primary rotavirus infection, virus excretion ceased when both antibody and mitogen responses were suppressed. Resistance to secondary rotavirus infection occurred when mitogen responsiveness was suppressed, but when antibody levels were normal. Thus, no evidence was obtained that fully functional cell-mediated immune mechanisms are essential for resistance to rotavirus infection. Evidence was provided for the ability of parenteral treatment with DX to suppress mucosal as well as systemic antibody responses.

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.

Natural killer cell activity of chicken intraepithelial leukocytes against rotavirus-infected target cells

Intraepithelial leukocytes (IEL) and splenocytes collected from uninfected and rotavirus-infected chickens were evaluated for cytotoxic activity against a natural killer (NK) cell-susceptible lymphoblastoid cell line (LSCC-RP9) and against rotavirus-infected chick kidney cells in 4-h chromium-release assays. Both splenocytes and IELs from uninfected and rotavirus-infected chickens were cytotoxic for LSCC-RP9, and the levels of this NK cell activity were not altered by infection of the host with rotavirus. IELs but not splenocytes from uninfected and rotavirus-infected chickens were cytotoxic for rotavirus-infected but not for uninfected chick kidney cell targets. Because this cytotoxic activity was not induced nor altered by rotavirus infection of the host, and was not major histocompatibility complex-restricted, it was considered to be due to NK cell activity. The cytotoxicity of IELs against rotavirus-infected target cells was dose-dependent; however, there was some suppression of cytotoxic activity at high effector to target cell ratios. There were no differences in the cytotoxic activities of IELs collected from the duodenum versus the jejunum. The in vitro cytotoxic activity of IELs against rotavirus-infected target cells suggested that NK cell activity may be an important immune response to rotavirus infections in vivo. The absence of cytotoxic activity by splenocytes against rotavirus-infected target cells indicated that there may be different subpopulations of NK cells in the spleen and intestinal epithelium of chickens.

Some infectious causes of diarrhea in young farm animals

Escherichia coli, rotaviruses, and Cryptosporidium parvum are discussed in this review as they relate to enteric disease in calves, lambs, and pigs. These microorganisms are frequently incriminated as causative agents in diarrheas among neonatal food animals, and in some cases different strains or serotypes of the same organism cause diarrhea in humans. E. coli causes diarrhea by mechanisms that include production of heat-labile or heat-stable enterotoxins and synthesis of potent cytotoxins, and some strains cause diarrhea by yet undetermined mechanisms. Rotaviruses and C. parvum induce various degrees of villous atrophy. Rotaviruses infect and replicate within the cytoplasm of enterocytes, whereas C. parvum resides in an intracellular, extracytoplasmic location. E. coli, rotavirus, and C. parvum infections are of concern to producers, veterinarians, and public health officials. These agents are a major cause of economic loss to the producer because of costs associated with therapy, reduced performance, and high morbidity and mortality rates. Moreover, diarrheic animals may harbor, incubate, and act as a source to healthy animals and humans of some of these agents.

A longitudinal study of bovine coronavirus enteric and respiratory infections in dairy calves in two herds in Ohio

This prospective longitudinal study examined the epidemiology and disease syndrome associated with bovine coronavirus (BCV) infections in a cohort of 8 conventional calves from 0 to 120 days of age, in two dairy herds in Ohio. The periods of respiratory shedding of BCV were determined by direct immunofluorescent (DIF) staining of nasal epithelial cells and ELISA of nasal swab supernatant fluids. The periods of fecal shedding of BCV were determined by ELISA and immunoelectron microscopy (IEM). The isotype-specific antibody titers to BCV in serum (at selected intervals between 0 and 120 days of age) and the post-suckling (24 to 48 h after birth) total immunoglobulin levels were examined by ELISA and zinc sulfate turbidity tests, respectively. Of the 8 calves studied, 4 had evidence of BCV respiratory (by DIF or ELISA) or enteric infections (by IEM or ELISA) in association with diarrhea or rhinitis, even though 7 of 8 calves showed increases in one or more serum antibody isotypes to BCV and 6 of 8 calves showed BCV respiratory or enteric antigen shedding by ELISA. Serological antibody titer increases occurred in 3 calves before 30 days of age and in 4 calves after 30 days of age; two of the latter calves had a second rise in serum antibody titers to BCV after the initial rise. A serological antibody titer increase was not observed in one calf. This suggests that BCV infections may be very common in a closed herd and may occur in older calves, although many may be subclinical and some may be recurrent. There were no statistically significant correlations between total serum immunoglobulin levels or BCV antibody isotype titers in serum (24-48 h after birth) and clinical disease or infection by BCV; however, calves with low levels of IgA BCV antibodies in serum (24-48 h after birth) had a significantly greater average number of days with diarrhea than those calves having high levels of IgA BCV-specific antibodies in serum.

The use of monoclonal antibodies in an enzyme immunospot assay to detect isotype-specific antibody-secreting cells in pigs and chickens

Monoclonal antibodies directed against porcine immunoglobulin isotypes G, G1, G2, M, and A and against chicken immunoglobulin isotopes G, M, and A were tested in an antigen-specific spot-forming cell (SFC) assay based on the principle of the enzyme immunoassay. The SFC assay was used to quantitate ovalbumin (OA)-specific antibody-secreting cells (ASC) in pigs that had been primed and boosted with OA. The SFC assay was also used to quantitate trinitrophenyl (TNP)-specific ASC in chickens that had been primed with TNP-conjugated keyhole lympet haemocyanin (TNP-KLH). Although, the classical plaque-forming cell (PFC) assay cannot reliably detect isotope-specific ASC in pigs and chickens, it can detect these cells in mice. Therefore, we compared the OA- and TNP-specific SFC assays with PFC assays that were specific for these antigens in mice. The study demonstrated that the SFC assay is superior to the PFC assay in detecting both OA-specific ASC and TNP-specific ASC. The frequencies of OA-specific and TNP-specific SFC detected in mice were of the same order of magnitude as those detected in pigs and chickens. We concluded that the SFC assay is the better method for quantitating ASC in pigs, chickens, and probably all domestic animals for which isotype-specific monoclonal antibodies are available.

Efficacy of an inactivated oil-adjuvanted rotavirus vaccine in the control of calf diarrhoea in beef herds in Argentina

We have assessed the potency of an inactivated oil-adjuvanted rotavirus vaccine in beef herds in Argentina. Two different vaccine trials were conducted. In a small-scale experimental trial, involving 21 pregnant cows (13 vaccinated and eight unvaccinated controls), a significant increase in neutralizing antibody titres against different serotypes of bovine rotaviruses was found in both the colostrum and serum of vaccinated cows compared with that of unvaccinated controls. Seven days after birth, half of the calves born to vaccinated dams or to control cows were challenged with live virulent virus whereas the other half of both groups were left in contact with the infected calves in order to mimic a natural field challenge. Although no statistically significant differences in the rate of protection were observed among the different groups of animals, a larger number of vaccinated calves were protected in comparison with their controls, particularly where animals in contact with infected calves were concerned. Secondly, a large-scale field trial was carried out in 17 beef herds involving a total of 4066 vaccinated pregnant cows. In 11 farms morbidity and mortality in calves from vaccinated cows were compared with historical data from the previous 3 years at the same locations. In the other six herds, control groups were used to compare data of the same year: 1540 cows were vaccinated and 2700 were left as controls. Taking into account the previous and current incidence of diarrhoea, morbidity and mortality were significantly reduced in 16 of the 17 beef herds tested. Vaccine effectiveness was also evident in farms where other enteropathogens such as cryptosporidium and coronaviruses were present, together with rotavirus.

Quantification of antigen-specific antibody-secreting cells in the small intestine and other lymphoid organs of mice after oral booster immunization

The intestinal immune response of mice against ovalbumin (OVA) was quantified by isolating lymphoid cells from the small intestine (SI) and testing them for antigen-specific immunoglobulin (Ig) secretion. The isolation procedure for functionally active lymphoid cells from the SI, originally developed to quantify the number of 'background' Ig-secreting cells in the SI, proved to be a useful method for evaluating antigen-specific intestinal immune responses quantitatively. The method was able to detect antigen-specific antibody-secreting cells (ASC) in the SI even when these cells occurred at a minimum frequency of only 0.006%. When mice were primed intraperitoneally (i.p.) with polymerized OVA and given an oral OVA booster immunization, OVA-specific ASC appeared in the SI from Day 3 after booster. After i.p. priming and an i.p. booster these cells could not be detected in the SI. The OVA-specific IgA-ASC responses in various organs after oral booster immunization were compared. From Day 5 after booster, when the response peaked, most OVA-specific IgA-ASC occurred in the SI. This suggested that these cells are mainly responsible for the OVA-specific antibodies demonstrated by ELISA in intestinal secretions from Day 6 after oral booster immunization. It is concluded that the quantitative method used in this study detects antigen-specific ASC in the SI with great sensitivity and could be used to evaluate immunization regimes aimed at inducing intestinal mucosal immune responses.

Passive immunity to bovine rotavirus infection associated with transfer of serum antibody into the intestinal lumen

The effect of circulating passive antibody on immunity to bovine rotavirus infections in neonatal calves was investigated. In the first experiment, rotavirus antibody titers in the small intestinal lumina of 5- and 10-day-old calves with a wide range of serum rotavirus antibody titers were determined. Neutralizing antibody was present in the small intestinal lumina in titers that correlated with the calves' serum titers (r = +0.84, P less than 0.01). Immunoglobulin G1 was the predominant isotype of intestinal luminal rotavirus antibody. Calves not fed colostrum during the absorptive period lacked rotavirus antibody in circulation and in the intestinal lumen at 7 days of age, even when they were fed large volumes of colostrum with a high rotavirus antibody titer at 48 h after birth. Therefore, rotavirus antibody is not retained in the intestinal lumen for 5 days following a colostrum meal, and the luminal antibody in the 5- and 10-day-old seropositive calves were probably derived from circulating antibody. In a second experiment, calves were passively immunized by subcutaneous injection of colostral whey with a high immunoglobulin G1 rotavirus antibody titer and challenged with virulent bovine rotavirus 48 h later. The passively immunized calves were protected from rotavirus infection and diarrhea compared with calves with comparable serum immunoglobulin concentrations but with lower serum rotavirus with lower serum rotavirus antibody titers. The results of these experiments indicate that circulating immunoglobulin G1 antibody appears in the gastrointestinal tract of neonatal calves and that circulating rotavirus antibody can prevent infection and diarrhea after rotavirus challenge.

Comparison of serum and mucosal antibody responses following severe acute rotavirus gastroenteritis in young children

The development of mucosal immunity is presumed to be the most important marker of rotavirus infection. The practical difficulties of obtaining small-bowel secretions stimulated this study of the antibody response to acute rotavirus infection at other sites. Forty-four infants admitted to the hospital with rotavirus gastroenteritis had serum, saliva, and feces collected at the acute phase (median, 5.5 days), during convalescence (median, 33.5 days), and 4 months later (median, 12.2 weeks). A subgroup of 19 children also had duodenal juice collected in parallel. Rotavirus-specific immunoglobulin G (IgG), IgA, secretory immunoglobulin, and IgM were measured and compared in all samples. The results showed that the estimation of antirotavirus serum IgM, serum IgG, duodenal juice IgA, and duodenal juice IgM by an enzyme immunoassay indicated an immune response to severe primary rotavirus infection in all children. Four months later, the levels of serum IgG and IgA served as the most sensitive markers of the preceding rotavirus infection. The predictive accuracies of immune responses at different sites in relation to a positive IgA immune response in the duodenum were calculated. Fecal IgA predicted duodenal IgA rotavirus antibodies with accuracies of 86% at 1 month and 92% at 4 months. The high sensitivity of serum IgM and IgG in detecting rotavirus infection and the high predictive accuracy of fecal IgA as an indicator of duodenal IgA abrogates the need for duodenal intubation to detect (or monitor) an immune response to rotavirus infection. This finding has important practical implications for epidemiological studies of acute diarrhea in children and in rotavirus vaccine trials.

Standardization and kinetics of in vitro bovine blood lymphocyte stimulation with bovine rotavirus

Two groups of 3-month old calves were immunized intramuscularly with attenuated bovine rotavirus and boosted 21 and 42 days later. The first group of three calves were vaccinated with live virus emulsified with incomplete Freund's adjuvant (IFA) and the second group was immunized with live virus suspended in phosphate buffered saline (PBS). Three other calves, serving as controls, were inoculated with PBS emulsified with IFA. The specific cell-mediated and antibody responses of the animals were studied. Preliminary analysis of in vitro peripheral blood lymphocyte transformation to bovine rotavirus determined optimal conditions as: 96 h culture period, 5 X 10(5) cells per culture in RPMI 1640 medium containing 10% heat-inactivated bovine fetal serum and the use of inactivated virus in the cell culture at a concentration of 5 X 10(6) median tissue culture infective dose before inactivation. Specific blastic stimulation was observed on calves immunized with the rotavirus emulsified with IFA after the second and third vaccine inoculation with stimulation index values varying from 2.00 to 5.73. Serum neutralizing antibody titers of 1/25,600 were also induced in the same calves. Calves immunized with rotavirus-PBS suspension developed a mean antibody titer of 1/1,600, but showed no specific lymphocyte stimulation. No increase in specific immune responses was detected in the control animals.

Development of nasal, fecal and serum isotype-specific antibodies in calves challenged with bovine coronavirus or rotavirus

Unsuckled specific pathogen free calves were inoculated at 3-4 weeks of age, either intranasally (IN) or orally (O) with bovine coronavirus or O plus IN (O/IN) or O with bovine rotavirus. Shedding of virus in nasal or fecal samples, and virus-infected nasal epithelial cells were detected using immunofluorescent staining (IF), ELISA or immune electron microscopy (IEM). Isotype-specific antibody titers in sera, nasal and fecal samples were determined by ELISA. Calves inoculated with coronavirus shed virus in feces and virus was detected in nasal epithelial cells. Nasal shedding persisted longer in IN-inoculated calves than in O-inoculated calves and longer than fecal shedding in both IN and O-inoculated calves. Diarrhea occurred in all calves, but there were no signs of respiratory disease. Calves inoculated with rotavirus had similar patterns of diarrhea and fecal shedding, but generally of shorter duration than in coronavirus-inoculated calves. No nasal shedding of rotavirus was detected. Peak IgM antibody responses, in most calves, were detected in fecal and nasal speciments at 7-10 days post-exposure (DPE), preceeding peak IgA responses which occurred at 10-14 DPE. The nasal antibody responses occurred in all virus-inoculated calves even in the absence of nasal shedding of virus in rotavirus-inoculated calves. Calves inoculated with coronavirus had higher titers of IgM and IgA antibodies in fecal and nasal samples than rotavirus-inoculated calves. In most inoculated calves, maximal titers of IgM or IgA antibodies correlated with the cessation of fecal or nasal virus shedding. A similar sequence of appearance of IgM and IgA antibodies occurred in serum, but IgA antibodies persisted for a shorter period than in fecal or nasal samples. Serum IgG1 antibody responses generally preceeded IgG2 responses and were predominant in most calves after 14-21 DPE.

Improved procedure for the isolation of functionally active lymphoid cells from the murine intestine

An isolation procedure for functionally active lamina propria lymphoid cells (LPL) from the murine intestine is described. The procedure involved EDTA-dithiothreitol incubation of intestinal tissue to remove epithelial and intraepithelial cells, followed by collagenase digestion of the basement membrane to liberate part of the LPL. The LPL were suspended by squeezing the remaining tissue strips through a nylon gauze filter. Functional activity was tested by enumeration of the immunoglobulin-secreting cells in the cell suspensions obtained by an isotype-specific protein A plaque-forming cell assay. On average 1-2 X 10(8) LPL were isolated from the intestine of C3H/He mice. 11% of these cells actively secreted Ig. From these Ig-secreting cells 99% produced IgA. The isolation procedure described in this paper permitted a higher recovery of viable cells than has previously been obtained with other methods.

Monoclonal antibodies against porcine immunoglobulin isotypes

Monoclonal antibodies (MCAs) against porcine immunoglobulin isotypes* G, G1, G2, M and A have been produced and characterized in detail. Epitope analysis using a competitive direct enzyme-linked immunosorbent assay (ELISA) indicated that the MCAs recognized 3 class-specific epitopes of IgG, 4 epitopes specific for IgG1, 3 epitopes specific for IgG2, 2 epitopes of IgM and 2 epitopes of IgA. Two MCAs against IgG2 were shown to react with an allotypic determinant (B2) and one MCA against IgM is probably allotype specific. The production of MCAs specific for IgG and for its subclasses G1 and G2 and, in addition, the one-step isolation of nearly pure IgG1 and IgG2 preparations by immunoaffinity chromatography using MCA 34.1.1a (anti-IgG2) confirmed the existence of at least two subclasses of IgG. Preliminary results further suggested the existence of a subpopulation of IgG1 which could be eluted selectively from Protein A-Sepharose columns at pH 5.0. MCA 34.17.2a appeared to react preferentially with this IgG1 subpopulation and could be used to isolate a similar IgG1 subpopulation by immuno-affinity chromatography. Several of the MCAs have been successfully applied for the detection of porcine immunoglobulin isotypes by a double antibody sandwich ELISA and for the (isotype-specific) detection of antibodies against various porcine viruses. The availability of a full set of MCAs against porcine immunoglobulin isotypes will stimulate and facilitate the further study of the porcine immune system.

Local and systemic antibody response to bovine respiratory syncytial virus infection and reinfection in calves with and without maternal antibodies

Enzyme-linked immunosorbent assays for the detection of immunoglobulin M (IgM), IgA, IgG1, and IgG2 antibodies against bovine respiratory syncytial virus (BRSV) were used to measure antibody responses of calves after experimental or natural infection with BRSV. Serially collected sera, lung lavage samples, nasal and eye secretions, and feces were tested for the presence of these antibodies. Lung lavage fluids and nasal secretions were further examined for the presence of virus. After experimental infection of 3- to 4-week-old, colostrum-deprived (seronegative) calves, the virus was detected from days 3 to 8 post-initial inoculation day (PID). An immune response was first detected 8 to 10 days PID, when BRSV-specific IgM and IgA appeared nearly simultaneously in serum, secretions, and feces. BRSV-specific IgG1 appeared only in serum on days 13 to 17 PID, and IgG2 was first detected in sera from 1 to 3 months PID. Specific IgM and IgA were detectable in the different samples for various periods. In the respiratory and eye secretions, IgA usually remained detectable for long periods, that is, for up to 3.5 months or longer. In lung lavage samples, BRSV-specific IgG1 was only incidentally demonstrated and appeared to be blood derived. The immune response of a 5-month-old calf strongly resembled that of the 3- to 4-week-old calves (feces excepted), indicating that an age effect on the immune response to BRSV is unlikely. After experimental infection of colostrum-fed, seropositive calves, both local and systemic antibody responses were largely or totally suppressed. The degree of suppression seemed to be related to the level of preinoculation virus-specific serum IgG1. Of all isotypes, IgM was least affected. Colostrum-fed animals shed virus in about equal amounts and for the same length of time as colostrum-deprived calves. Clinical signs were mild in both groups. After reinfection, no virus shedding was detected in either colostrum-deprived or colostrum-fed calves. In both groups, a secondary immune response developed, characterized by strong and rapid (from about day 6 PID) mucosal and systemic IgA responses, but reaching higher titers in colostrum-deprived calves. Also, strong mucosal, but not serum, IgM responses were observed, which, however, did not develop faster than those observed after primary infection. Naturally infected calves, showing severe signs of respiratory disease, had various levels of, most likely, maternally derived antibodies on the first day of illness. Mucosal and systemic antibody responses of various heights and durations were observed, but in general these responses were stronger than those observed after experimental infection. The results point to an important role for local IgA, rather for serum IgG1, in the protection against BRSV infection. The capacity to mount a local memory IgA response seems especially important. Priming for such a mucosal memory response is possible even when the primary immune response is severely suppressed because of the presence of material antibodies.