The relationship between cellular immune response to foot-and-mouth disease virus Asia 1 and viral persistence in Indian cattle (Bosindicus)

Foot-and-mouth disease (FMD), the most contagious animal disease, is associated with persistent viral infection in ruminants, despite the induction of systemic immune response. The present study was performed to decipher the relation between the persistent FMD virus (FMDV) infection and cellular immune response in Indian cattle (Bosindicus) following experimental inoculation of FMDV Asia 1. Persistent viral infection (carriers) was detected by antigen capture RT-PCR on the oesophageal-pharyngeal fluid. Viral excretion was found to be intermittent and strongly variable among the persistently infected Indian cattle. Lymphocyte proliferative (LP) response, assessed as reactivity of peripheral blood mononuclear cells to FMDV Asia 1 antigen (Ag) was of low magnitude indicating a weak primary cellular immune response following infection. LP response to FMDV Ag was higher among the non-carriers than carriers of FMDV Asia 1. An enhanced LP response was associated with the lack of virus shedding in the OPF. The findings of this study are suggestive of relationship between cellular immune response and virus excretion during persistence of FMDV Asia 1 in infected cattle.     

Kinetics of immune response to foot-and-mouth disease virus (type Asia 1) in experimental cattle

Humoral and mucosal (secretory antibody)immune response to FMDV type Asia 1 in cattle was analyzed after vaccination and infection using virus neutralizing test (VNT). Vaccination (1/16th the usual dose) failed to protect cattle from generalized clinical disease following experimental FMDV Asia 1 infection. Our results showed that infection induced higher and prolonged serum antibody titres indicating antigen mass is important for optimal immune response. Experimental FMDV infection induced significant secretory antibody (mucosal) response in cattle. Though, there was no difference in the serum antibody response between the cattle that developed generalized infection (unprotected) and those with only localized infection (protected), secretory antibody response differed, wherein the unprotected cattle had higher secretory response than protected cattle. Thus, FMDV Asia 1 infection stimulates a similar serum antibody response and a unique secretory antibody response among the infected cattle. An erratum to this article can be found at     

Detection of carriers of foot-and-mouth disease virus among vaccinated cattle

To investigate and optimise detection of carriers, we vaccinated 15 calves with an inactivated vaccine based on foot-and-mouth disease virus (FMDV) A Turkey strain and challenged them and two further non-vaccinated calves with the homologous virus four weeks later. To determine transmission to a sensitive animal, we put a sentinel calf among the infected cattle from 60 days post-infection until the end of the experiment at 609 days post-infection. Samples were tested for the presence of FMDV, viral genome, specific IgA antibodies, antibodies against FMDV non-structural (NS) proteins or neutralising antibodies. Virus and viral genome was intermittently isolated from probang samples and the number of isolations decreased over time. During the first 100 days significantly more samples were positive by RT-PCR than by virus isolation (VI), whereas, late after infection more samples were positive by virus isolation. All the inoculated cattle developed high titres of neutralising antibodies that remained high during the entire experiment. An IgA antibody response was intermittently detected in the oropharyngeal fluid of 14 of the 17 calves, while all of them developed detectable levels of antibodies to NS proteins of FMDV in serum, which declined slowly beyond 34 days post-infection. Nevertheless, at 609 days after inoculation, 10 cattle (60%) were still positive by NS ELISA. Of the 17 cattle in our experiment, 16 became carriers. Despite frequent reallocation between a different pair of infected cattle no transmission to the sentinel calf occurred. It remained negative in all assays during the entire experiment. The results of this experiment show that the NS ELISA is currently the most sensitive method to detect carriers in a vaccinated cattle population.     

Analysis of the acute phase responses of Serum Amyloid A, Haptoglobin and Type 1 Interferon in cattle experimentally infected with foot-and-mouth disease virus serotype O

ABSTRACT: A series of challenge experiments were performed in order to investigate the acute phase responses to foot-and-mouth disease virus (FMDV) infection in cattle and possible implications for the development of persistently infected "carriers". The host response to infection was investigated through measurements of the concentrations of the acute phase proteins (APPs) serum amyloid A (SAA) and haptoglobin (HP), as well as the bioactivity of type 1 interferon (IFN) in serum of infected animals. Results were based on measurements from a total of 36 infected animals of which 24 were kept for observational periods exceeding 28 days in order to determine the carrier-status of individual animals. The systemic host response to FMDV in infected animals was evaluated in comparison to similar measurements in sera from 6 mock-inoculated control animals.There was a significant increase in serum concentrations of both APPs and type 1 IFN in infected animals coinciding with the onset of viremia and clinical disease. The measured parameters declined to baseline levels within 21 days after inoculation, indicating that there was no systemically measurable inflammatory reaction related to the carrier state of FMD. There was a statistically significant difference in the HP response between carriers and non-carriers with a lower response in the animals that subsequently developed into FMDV carriers. It was concluded that the induction of SAA, HP and type 1 IFN in serum can be used as markers of acute infection by FMDV in cattle.     

Virus carriers in foot-and-mouth disease. Review

FMDV infection can cause a long lasting virus carrier state in the oesophageal-pharyngeal (OP) region of cattle, sheep, goats, African buffalo, wildebeest and kudu. Virus can be recovered from OP fluids with low titres for several months up to more than 2 years. During this time phases of positive virus recovery are interrupted by negative phases. The number of virus carriers decreases as time progresses. The virus carrier state is always accompanied by FMDV antibodies in serum and OP fluid. Vaccinated animals also become virus carriers after FMDV infection, to the same extent as unvaccinated animals. No virus carrier state has been proven in pigs, but it cannot be excluded in some species of deer. Epizootic importance of carrier animals (in FMD) has not been found. Experimental contact transmissions of carrier virus to cattle, sheep and goats have failed. Only buffalo transmit carrier virus to the own species and perhaps to cattle. Nevertheless, virus carriers represent a natural reservoir of FMDV in infected areas and a potential source of antigenically altered virus variants, since continuous variations of the virus and selection of virus mutants take place in the animal during the carrier state.     

Development and validation of a 3ABC indirect ELISA for differentiation of foot-and-mouth disease virus infected from vaccinated animals

Non-structural protein (NSP) 3ABC antibody is considered to be the most reliable indicator of present or past infection with foot-and-mouth disease virus (FMDV) in vaccinated animals. An indirect ELISA was established, using purified His-tagged 3ABC fusion protein as antigen, for detection of the antibody response to FMDV NSP 3ABC in different animal species. The method was validated by simultaneous detection of the early antibody responses to NSP and structural protein (SP) in FMDV Asia 1 infected animals. The performance of the method was also validated by detection of antibody in reference sera from the FMD World Reference Laboratory (WRL) in Pirbright, UK, and comparison with two commercial NSP ELISA kits. The results showed that the antibody response to SP developed more quickly than that to NSP 3ABC in FMDV infected animals. In contact-infected cattle, the antibody response to NSP 3ABC was significantly delayed compared with that to SP antibody. The early antibody responses to SP and NSP 3ABC in FMDV inoculated cattle and contact-infected or inoculated sheep and pigs were generally consistent. In pigs, 3ABC antibody was linked to the presence of clinical signs; however, in sheep, subclinical infection was detected by the development of 3ABC antibodies. Therefore, the antibody responses to 3ABC varied between host species. Eight out of 10 positive serum samples from FMD WRL were tested to be positive at cutoff value of 0.2. The rate of agreement with the ceditest FMDV-NS and the UBI NSP ELISA were 98.05% (302/308) and 93.2% (287/308), respectively. The prevalence of 3ABC antibodies reached 71.4% in some diseased cattle herds. The further work is required to evaluation the performance of this method in different animal species and different field situations.     

Detection of foot-and-mouth disease virus RNA in pharyngeal epithelium biopsy samples obtained from infected cattle: investigation of possible sites of virus replication and persistence

Foot-and-mouth disease (FMD) is a highly contagious viral infection of significant financial importance to the export and trade of agricultural products. The occurrence of persistently infected "carriers" of FMD-virus (FMDV) in ruminant species adds further complications to disease control. There have been significant discrepancies in reports regarding the pathogenesis of FMDV infection in cattle with specific emphasis on the anatomical sites involved in early and persistent virus replication. In this study, collection of small biopsy samples from the dorsal soft palate (DSP) of live animals was used to investigate the level of FMDV RNA present at this site at sequential time points during the infection. Results were compared to measurements of virus excretion in samples of oropharyngeal fluid collected at corresponding time points. Possible sites of virus persistence were investigated through measurements of the levels of FMDV RNA in the DSP as well as mandibular and retropharyngeal lymph nodes beyond 28 days after infection. Results indicated only low levels of FMDV RNA present in samples of pharyngeal epithelia during both early and persistent phases of infection with significantly higher levels of virus detected in pharyngeal excretions. It is concluded that the targeted area for sampling within the DSP does not harbour significant levels of virus replication during acute or persistent FMDV infection in cattle. Furthermore, the DSP and the mandibular and retropharyngeal lymph nodes cannot be concluded to be principal sites for persistence of FMDV.     

Serum antibody isotype responses of Fasciola-infected sheep and cattle to excretory and secretory products of Fasciola species

This study investigated the immunoglobulin isotype responses of sheep and cattle chronically infected with Fasciola hepatica and Fasciola gigantica to adult F. hepatica excretory/secretory products (Fh-ES) or F. gigantica excretory/secretory products (Fg-ES), respectively. An antibody enzyme-linked immunosorbent assay (Ab-ELISA) was used to determine serum antibody (total Ig, IgG(1), IgM, IgG(2) and IgA) responses. At necropsy, the mean number of flukes recovered was lower in cattle than in sheep. All F. hepatica and F. gigantica infected sheep and cattle showed an increased total Ig levels from 3 to 4 weeks post-infection (wpi). Among isotypes IgG(1) was most dominant while IgM was the earliest (2 wpi) to be detected in both sheep and cattle infected with both F. hepatica and F. gigantica animals. IgG(2) response was early (2 wpi) in sheep infected by F. hepatica but there was no response in sheep infected with F. gigantica. There was a late and strong IgG(2) response in cattle infected with both flukes. The IgA isotype showed an early and a clear biphasic response in sheep with F. hepatica but was less pronounced in F. gigantica infected sheep. While IgA response to Fh-ES was noticed 5 wpi in F. hepatica infected cattle, it appeared much later (21 wpi) in those infected with F. gigantica. The dominance of IgG(1) isotype in infected sheep and cattle suggest an associated Th2 response. This early response to adult Fasciola spp. ES antigen suggests an early exposure to the antigen presumably through the cross-reacting ES products of juvenile flukes. There is clearly difference in IgG(2) isotype response in cattle (resistant) compared to sheep (susceptible). The late IgG(2) response in cattle may suggest late Th1 involvement in bovine cellular responses to adult Fh-ES/Fg-ES.     

猪A型口蹄疫病毒特异性IgA抗体间接ELISA检测方法的建立与初步应用

为建立一种检测口蹄疫病毒（foot-and-mouth disease virus,FMDV）特异性IgA抗体的检测方法,本研究以原核表达系统表达纯化的FMDV结构蛋白VP1作为包被抗原,以鼠抗猪IgA单克隆抗体为二抗,辣根过氧化酶标记的羊抗鼠IgG抗体为三抗,建立猪A型FMDV特异性IgA抗体间接ELISA检测方法。确定抗原包被浓度为3.50 μg/mL,二抗与三抗的最佳稀释度为1∶10 000,二抗和三抗作用时间均为30 min。所建立的方法与抗猪瘟病毒、猪繁殖与呼吸道综合征病毒等病原的特异性IgA抗体间无交叉反应,A型口蹄疫感染样品的阳性检出率在90%以上,批内和批间重复性试验的变异系数介于3.16%~9.76%。该方法为监测FMDV特异性IgA抗体水平变化规律及猪的黏膜免疫效果评价及口蹄疫的早期诊断提供了一种新方法。     

Development and Primary Application of Indirect ELISA Method for Detecting the IgA Antibody against Foot-and-mouth Disease Virus Type A in Porcine

An indirect ELISA for detecting the IgA antibody against porcine foot-and-mouth disease virus (FMDV) type A was developed by using purified FMDV structural protein VP1 as coating antigen, mouse anti-pig IgA monoclonal antibody as second antibody and HRP-conjugated goat anti-mouse IgG as third antibody.The concentration of coating antigen was optimized as 3.50 μg/mL,the dilution and reaction time of second antibody and third antibody were optimized as 1:10 000 and 30 min, respectively.There was no cross-reactivity with anti-CSFV, PRRSV and other pathogen specific IgA antibodies.The positive detection rate of FMDV type A infectedsamples was above 90%.The coefficient variation of intra-and inter-assay was ranged from 3.16% to 9.76%.The ELISA method described in this study was proved to be specific and rapid for the detection of FMDV specific IgA antibody.It was potential to be applied for detection the level of FMDV specific IgA and evaluate the effect of mucosal immunity.Besides,it provided a new method for clinical diagnosis of foot-and-mouth disease.     

Local immunity in the respiratory tract of the chicken. II. The secretory immune response to newcastle disease virus and the role of IgA

The nature, specificity and characteristics of the secretory immune response in the respiratory tract of the chicken were investigated in young specific-pathogen-free chickens after vaccination with live lentogenic and inactivated Newcastle disease virus (NDV). Virus-neutralizing (VN) activity considerably exceeding transudation levels from serum were detected in lachrymal fluid, saliva and tracheal washes following infection by both ocular and oral routes. Heat inactivated virus inoculated into the trachea evoked neither serum nor secretory VN activity, whereas a commercial inactivated virus vaccine in mineral oil adjuvant stimulated high titres of serum antibody and some VN activity in tracheal fluids.Antibody in secretions limited, but did not prevent, reinfection of the trachea when birds were challenged 2 weeks later. In contrast to an elevation of circulating antibody titre, challenge induced only a repeated primary response of secreted antibody.All secretions contained IgA which, at least in saliva, accounted for 85% of its activity, the remainder being due to IgG. Fluorescent localization of immunoglobulin producing cells (IPC) demonstrated large numbers containing IgA in association with the upper respiratory tract, particularly in the Harderian gland which contained dense aggregations of plasma cells, many of which were producing IgA.It is concluded that the respiratory tract of the chicken possesses an antibody mediated secretory immune system analogous to that of mammalian species.     

Cattle remain immunocompetent during the acute phase of foot-and-mouth disease virus infection

ABSTRACT: Infection of cattle with foot-and-mouth disease virus (FMDV) results in the development of long-term protective antibody responses. In contrast, inactivated antigen vaccines fail to induce long-term protective immunity. Differences between susceptible species have also been observed during infection with FMDV, with cattle often developing persistent infections whilst pigs develop more severe symptoms and excrete higher levels of virus. This study examined the early immune response to FMDV in na?ve cattle after in-contact challenge. Cattle exposed to FMDV were found to be viraemic and produced neutralising antibody, consistent with previous reports. In contrast to previous studies in pigs these cattle did not develop leucopenia, and the proliferative responses of peripheral blood mononuclear cells to either mitogen or third party antigen were not suppressed. Low levels of type 1 interferon and IL-10 were detected in the circulation. Taken together, these results suggest that there was no generalised immunosuppression during the acute phase of FMDV infection in cattle.     

Foot-and-mouth disease virus-like particles produced by a SUMO fusion protein system in Escherichia coli induce potent protective immune responses in guinea pigs,swine and cattle

Foot-and-mouth disease virus (FMDV) causes a highly contagious infection in cloven-hoofed animals. The format of FMD virus-like particles (VLP) as a non-replicating particulate vaccine candidate is a promising alternative to conventional inactivated FMDV vaccines. In this study, we explored a prokaryotic system to express and assemble the FMD VLP and validated the potential of VLP as an FMDV vaccine candidate. VLP composed entirely of FMDV (Asia1/Jiangsu/China/2005) capsid proteins (VP0, VP1 and VP3) were simultaneously produced as SUMO fusion proteins by an improved SUMO fusion protein system in E. coli. Proteolytic removal of the SUMO moiety from the fusion proteins resulted in the assembly of VLP with size and shape resembling the authentic FMDV. Immunization of guinea pigs, swine and cattle with FMD VLP by intramuscular inoculation stimulated the FMDV-specific antibody response, neutralizing antibody response, T-cell proliferation response and secretion of cytokine IFN-γ. In addition, immunization with one dose of the VLP resulted in complete protection of these animals from homologous FMDV challenge. The 50% protection dose (PD₅₀) of FMD VLP in cattle is up to 6.34. These results suggest that FMD VLP expressed in E. coli are an effective vaccine in guinea pigs, swine and cattle and support further development of these VLP as a vaccine candidate for protection against FMDV.     

Helicobacter pylori-specific immunoglobulin synthesis in gnotobiotic piglets: evidence for the induction of mucosal immunity in the stomach

Short term tissue biopsy cultures and paired, sera, bile and gastric and intestinal contents from Helicobacter pylori-infected gnotobiotic piglets were tested for the synthesis of H. pylori-specific immunoglobulin (Ig) isotype production by antigen-specific ELISA from post-infection days (PIDs) 2-28. Serum antibody levels in all three Ig isotypes were elevated from baseline values by PID 14, serum IgM levels reached peak levels on PID 14 and by PID 28 bile was strongly positive for IgA and IgG.Intestinal, but not gastric contents from infected piglets, contained IgA-specific antibody from PID 14 onward. Gastric mucosal epithelia adjacent to areas of inflammation in infected but not uninfected control piglets produced readily detectable amounts of porcine secretory component (SC); IgA-positive plasma cells were identified in gastric submucosa and lamina propria in these areas. Culture fluid supernatants, collected from explanted gastric cardia and antra and intestinal ilea of H. pylori-infected piglets had trace amounts of IgA as early as PID 2 in some animals, and strong IgA reactivity in all by PID 28. Supernatants also contained H. pylori-specific IgG by PID 14. A strong gastric lymph node IgA response contrasted with moderate IgA production in mesenteric lymph nodes and spleen. Mucosal biopsy production of H. pylori-specific IgG was more evenly distributed throughout the lymphoid system. These data support the contention that the Ig response to H. pylori is initiated within the gastric compartment and matures over time to a generalized IgA-dominated mucosal and IgG-dominated nonmucosal humoral immune response.     

Maturation of functional antibody affinity in animals immunised with synthetic foot-and-mouth disease virus.

A good correlation exists between specific neutralising antibody titre and protection against challenge with foot-and-mouth disease virus (FMDV) in infected or virus-vaccinated cattle, but not in the case of animals immunised with synthetic FMDV peptides. Therefore, mechanisms other than simple neutralisation are likely to be important in vivo. Antibody affinity may influence the protective capacity of sera from immunised animals and experiments were carried out to measure the functional affinity for synthetic FMDV peptide of sera from guinea pigs and cattle given various synthetic vaccines. In guinea pigs given a single dose of synthetic vaccine, antibody affinity increased with time after immunisation. In cattle, however, administration of a second dose of peptide 21 days after the first markedly retarded the process of affinity maturation. For guinea pig sera of equivalent neutralising activity, those of higher functional affinity had higher protective indices than those of lower functional affinity. Knowledge of the importance of antibody affinity in protection against FMD is important for an improved understanding of the mechanisms of protection and for the design of novel vaccines.     

Regulation of IgA responses in cattle, humans and mice

Secretory IgA (SIgA) constitutes the largest component of the humoral immune system of the body with gram quantities of this isotype produced by mammals on a daily basis. Secretory IgA (SIgA) antibodies function by both blocking pathogen/commensal entry at mucosal surfaces and virus neutralization. Several pathways of induction of IgA responses have been described which depend on T cells (T cell dependent or TD) pathways or are independent of T cells (T-independent or TI) and are mediated by dendritic cells (DCs) and/or epithelial cells. Many elements of IgA regulation readily cross species barriers (adjuvants, soluble and cognate factors) and are highly conserved whereas other pathways may be more specific to any given species and must be evaluated. Regulation of IgA production in cattle is not completely understood and thus we have focused in part on highly conserved factors such as transforming growth factor beta, Type I and Type 2 interferons, neuropeptides which interdigitate mucosal tissues (vasoactive intestinal peptide or VIP), and a small peptide (IgA inducing peptide or IGIP) which can serve as targets for modulation and increasing SIgA virus-specific antibodies. We have evaluated the potential utility of modulating these factors in vitro in regulation of qualitative aspects of antibodies of the IgM, IgG and IgA isotypes at mucosal surfaces and in secretions of the upper and lower respiratory tract to a virus of economic and public health importance, foot and mouth disease virus (FMDV). IgA responses in cattle are essential for host defense in response to various infectious agents. In cattle, IgA is not released into the colostrum, as is the case for other mammals but only IgG1 is selectively transported. In previous studies in cattle, IgA has been shown to be regulated by several cytokines including IFN-gamma, Type I interferons such as IFN-alpha and IFN-tau, transforming growth factor beta, IgA inducing peptide and other potential factors such as APRIL and BlyS which have not yet been fully evaluated in cattle. Many of these factors, namely TGF-beta and Type I interferons block cell cycle progression which is an essential component of Ig class switching and thus these factors require additional regulatory factors such as IL-2 to drive cells through cell cycle resulting in class switch recombination. Among these factors, IgA inducing peptide was originally identified from a bovine gut associated lymphoid tissue expression library and is highly conserved in pigs and humans at >90% at the amino acid level. The factor is regulated differently in various species but is consistently produced by dendritic cells.     

Evaluation of systemic and secretory IgA concentrations and immunohistochemical stains for IgA-containing B cells in mucosal tissues of an Irish setter with selective IgA deficiency

Immunoglobulin A is the predominant secretory antibody at mucosal surfaces. In the dog, immunoglobulin A deficiency (IgAD) is characterized by low to absent serum IgA and normal to elevated serum immunoglobulin G (IgG) and immunoglobulin M (IgM) concentrations. However, studies comparing serum and secretory IgA in dogs have often documented a poor correlation, suggesting that serum concentrations should not be used to estimate mucosal secretion of this antibody. This report demonstrates the concurrent use of serum IgA, IgG, and IgM; secretory IgA (from bronchoalveolar lavage fluid); and immunohistochemical stains on bronchial and duodenal mucosa for IgA-containing B cells in a young Irish setter with recurrent respiratory and gastrointestinal signs.     

Comparative study of experimental Foot-and-Mouth Disease in cattle (<Emphasis Type="Italic">Bos indicus</Emphasis>) and buffaloes (<Emphasis Type="Italic">Bubalis bubalus</Emphasis>)

Foot-and-mouth disease (FMD) is one of the most contagious diseases affecting wide range of host species with variable severity and decreased productivity. The present study was undertaken to compare the clinical and leucocytic changes in indigenous Indian cattle and buffaloes experimentally infected with FMD virus (FMDV) Asia 1. A mild type of disease was observed in the cattle, more so in buffaloes infected with FMDV. Difference in terms of type, site and healing of lesion was observed between cattle and buffaloes. Foot lesions were more common than tongue in buffaloes, which were mainly evident in bulb of the heel in contrast to interdigital foot lesions in cattle. Further, FMDV infection induced a transient moderate leucopenia with lymphopenia in both cattle and buffaloes, but monocyte levels diverged. Relationship between the raised body temperature, leucocytic changes and lesion development was observed. Microscopic changes were observed in the keratinized epithelium of tongue and foot. The findings of the present study indicated the need to investigate the early leucocytic changes in cattle and buffaloes in depth for better understanding of the disease process.     

The dynamic influence of the DRB1*1101 allele on the resistance of sheep to experimental Teladorsagia circumcincta infection

ABSTRACT: Suffolk sheep carrying the DRB1*1101 (previously referred to as-DRB1*0203 or G2) allele have been reported to show increased resistance to natural Teladorsagia circumcincta infection compared to non-carriers. The objective of this study was to compare the biochemical and physiological responses of DRB1*1101 carrier and non-carrier twin lambs to an experimental infection with 3 × 104 L3 Teladorsagia circumcincta. The variables studied included worm burden, faecal egg count, abomasal mast cells, IgA, IgE, IgG1 plus IgG2 and haematological parameters at 0, 3, 7, 21 and 35 days post infection (dpi), and duodenal smooth muscle contractility at 0 and 35 dpi. DRB1*1101 carrier lambs had significantly lower worm burden, higher mast cell and plasma platelet counts than the DRB1*1101 non-carriers (P < 0.05). Before infection, the non-carrier lambs exhibited significantly higher mucosal levels of all antibody isotypes measured compared to the carriers; these levels remained relatively stable over the course of infection in the non-carriers while there was a slow build up of these antibodies in the carriers up to day 21 post infection (pi). The DRB1*1101 non-carrier lambs had a significantly higher plasma lymphocyte count, and produced greater duodenal contractile force relative to the carrier lambs (P < 0.05). There was no significant difference between genotypes in the level of plasma eosinophils, monocytes, neutrophils or FEC. This evidence suggests that resistance conferred by DRB1*1101 is acquired rather than innate, depends on worm expulsion rather than fecundity and is dependent on mucosal mast cell proliferation, platelet activation, and IgA and IgE antibody responses.     

Brucella abortus-specific immunoglobulin in isotypes in serum and vaginal mucus from cattle vaccinated with strain 19 and challenge exposed with virulent strain 2308

The immunoglobulins (IgG1, IgG2, IgM, and IgA) of the Brucella-specific antibody response of 69 crossbred beef heifers were studied after Brucella abortus strain 19 vaccination and strain 2308 challenge exposure. The immunoglobulin isotype responses in serum and vaginal mucus were measured by use of fluorescent immunoassay. Serum antibody responses were detected also by 3 standard serologic tests (complement fixation [CF], Rivanol precipitation, and the CARD test] and 2 primary bindings assays that detect IgG antibodies. One month after vaccination, mean antibody titers for all immunoglobulin isotypes were higher for vaccinated cattle (n = 46) than for nonvaccinated controls (n = 23). After vaccination, IgA antibody responses in vaccinated cattle were only 2-fold higher than those for controls, whereas IgG1, IgG2, and IgM antibody responses were 3- to 90-fold greater than those for controls. Measurement of IgA antibody responses classified 21 of 39 vaccinates as seropositive after vaccination, whereas the other isotypes classified 28 or 34 cattle as seropositive. Three months after challenge exposure, the mean antibody responses for each isotype were higher in cattle that aborted or were culture positive than in cattle that did not abort and were culture negative. Although IgG1, IgG2, and IgM antibody titers were each of benefit in identifying B abortus-infected cattle, it did not appear that the magnitude of the antibody responses provided sufficient discrimination between S19-vaccinated cattle and S2308 challenge-exposed cattle. Serum IgA antibody responses were 10-fold higher after challenge exposure than after vaccination and may be a response to mucosal infection with the virulent organism.(ABSTRACT TRUNCATED AT 250 WORDS)