A protein-based subunit vaccine with biological adjuvants provides effective protection against Pasteurella multocida in pigs.

Streptococcus suis (S. suis) and Pasteurella multocida (P. multocida) are pathogens that can cause zoonotic diseases. P. multocida toxin (PMT) is an important virulence factor that causes atrophic rhinitis in pigs. Suilysin (Sly) is an extracellular protein of S. suis and has been shown to be a potential adjuvant. Previous studies have indicated that subunit vaccines containing several fragments of PMT as antigens are safer than traditional inactivated or live-attenuated vaccines. However, protein-based vaccines need strong adjuvants to enhance their immunogenicity. In this study, recombinant PMT-NC (rPMT-NC) protein antigen was formulated with either recombinant Sly (rSly) or CpG oligodeoxynucleotides (CpG) as the adjuvant. The immune responses elicited by these vaccines and the protective efficacy after challenge with live P. multocida were evaluated in piglets. In the dose-dependent test, piglets immunized with the low dose (100 µg) of rSly had increased antigen-specific total IgG, interferon (IFN)-γ gene expression, and CD4+ and CD8+ T-cell populations. Compared to piglets in the commercial (Al-gel) adjuvant and the control groups (p < 0.05), piglets in the biological adjuvant groups showed significantly reduced turbinate atrophy, nasal distortion, and lung lesion scores after challenge with P. multocida serotype A. Vaccines containing rSly or CpG adjuvant enhanced humoral and cellular immune responses and protection against P. multocida. This combination of a protein-based antigen formulated with a biological adjuvant showed synergistic and protective effects against atrophic rhinitis and has potential to be developed as part of a bivalent vaccine.

Evaluation of the immunobiological effects of a regenerative far-infrared heating system in pigs.

Thermal conditions are an important environmental factor in maintaining healthy pigs because they affect feed intake, growth efficiency, reproduction and immune responses in pigs. RAVI, a regenerative far-infrared heating system, can effect pig production by emitting an optimal far-infrared wavelength. Far-infrared radiation has been reported to increase microvascular dilation and vascular flow volume. The purpose of this study was to evaluate the immunobiological differences between pigs raised with the RAVI system and the gasoline heater system. Twenty-six-week-old weaned pigs were raised in two rooms that were equipped with a RAVI system or a gasoline heater for 8 weeks. A porcine atrophic rhinitis vaccine was administered after two weeks and transcriptome analysis in whole blood were analyzed at 2-week intervals. Signaling pathway analyses of the RAVI group at 8 weeks showed the activation of pathways related to nitric oxide (NO) production. This suggests that the application of RAVI might induce the production of NO and iNOS, which are important for increasing the immune activity. Similar to the result of microarray, phenotypic changes were also observed at a later period of the experiment. The increase in body weight in the RAVI group was significantly higher than the gasoline heater group at 8 weeks. The antibody titer against the vaccine in the RAVI group was also higher than that the gasoline heater group at 4 weeks and 8 weeks. This evaluation of the use of a far-infrared heating system with pigs will be helpful for applications in the pig farm industry and pig welfare.

Comparison of gene expression of Toll-like receptors and cytokines between Piau and Commercial line (Landrace×Large White crossbred) pigs vaccinated against Pasteurella multocida type D.

We aimed to compare Toll-like receptors (TLR) and cytokines expression in local Piau breed and a Commercial line (Landrace×Large White crossbred) pigs in response to vaccination against Pasteurella multocida type D. Seronegative gilts for Pasteurella multocida type D and Mycoplasma hyopneumoniae were used, from which peripheral blood mononuclear cells (PBMC) were collected in four time points (T0, T1, T2 and T3; before and after each vaccination dose). For bronchoalveolar lavage fluid cells (BALF), we set groups of vaccinated and unvaccinated animals for both genetic groups. Gene expression was evaluated on PBMC and BALF. In PBMC, when we analyzed time points within breeds, significant differences in expression for TLRs and cytokines, except TGFß, were observed for Commercial animals. For the Piau pigs, only TGFß showed differential expression. Comparing the expression among genetic groups, the Commercial pigs showed higher expression for TLRs after first vaccination dose, while for IL2, IL6, IL12 and IL13, higher expression was also observed in T3 and IL8 and IL10, in T1 and T3. Still comparing the breeds, the crossbred animals showed higher expression for TNFα in T1 and T2, while for TGFß only in T2. For gene expression in BALF, vaccinated Commercial pigs showed higher expression of TLR6, TLR10, IL6, IL8, IL10, TNFα and TGFß genes than vaccinated Piau pigs. The Commercial line pigs showed higher sensitivity to vaccination, while in local Piau breed lower responsiveness, which may partly explain genetic variability in immune response and will let us better understand the tolerance/susceptibility for pasteurellosis.

Immunologic study and optimization of Salmonella delivery strains expressing adhesin and toxin antigens for protection against progressive atrophic rhinitis in a murine model.

Mice were intranasally inoculated at various times to optimize the vaccination strategy with a new live candidate vaccine expressing the antigens CP39, FimA, PtfA, and ToxA of Pasteurella multocida and F1P2 of Bordetella bronchiseptica in an attenuated live Salmonella system to protect against progressive atrophic rhinitis (PAR). Sixty BALB/c mice were divided equally into 4 groups. The group A mice were vaccinated only at 12 wk of age, the group B mice received a primary vaccination at 9 wk of age and a booster at 12 wk of age, the group C mice received a primary vaccination at 6 wk of age and boosters at 9 and 12 wk of age, and the group D mice were inoculated intranasally with sterile phosphate-buffered saline as a control. The humoral and mucosal immune responses of groups A, B, and C increased significantly compared with those of the control group. Expression of the cytokines interleukin-4 and interferon-γ in splenocytes also increased significantly. In addition, the group B mice exhibited significantly fewer gross lesions in lung tissue compared with the other vaccinated groups after challenge with a virulent P. multocida strain. These results indicate that a strategy of double intranasal vaccination can optimize protection against PAR.

Des souris furent inoculées par voie intra-nasale à différents temps pour optimiser la stratégie de vaccination avec un nouveau vaccin candidat vivant exprimant les antigènes CP39, FimA, PtfA, et ToxA de Pasteurella multocida et F1P2 de Bordetella bronchiseptica dans un système vivant atténué de Salmonella afin de protéger contre la rhinite atrophique progressive (PAR). Soixante souris BALB/c ont été divisées également en quatre groupes. Les souris du groupe A furent vaccinées seulement à 12 semaines d'âge, les souris du groupe B ont reçu une première vaccination à 9 sem d'âge et un rappel à 12 sem d'âge, les souris du groupe C ont reçu une première vaccination à 6 sem d'âge et des rappels à 9 et 12 sem d'âge, et les souris du groupe D (groupe témoin négatif) furent inoculées par voie intra-nasale avec uniquement de la saline tamponnée stérile. Les réponses immunes humorales et mucosales des groupes A, B et C augmentèrent de manière significative comparativement à celles du groupe témoin. L'expression des cytokines interleukine-4 et interféron-γ dans les splénocytes augmenta également de manière significative. De plus, les souris du groupe B avaient significativement moins de lésions macroscopiques dans le tissu pulmonaire comparativement aux autres animaux des groupes vaccinés suite à une infection avec une souche virulente de P. multocida. Ces résultats indiquent qu'une stratégie de double vaccination intra-nasale peut optimiser la protection envers PAR.(Traduit par Docteur Serge Messier).

Generation of an attenuated Salmonella-delivery strains expressing adhesin and toxin antigens for progressive atrophic rhinitis, and evaluation of its immune responses in a murine model.

An expression/secretion plasmid containing genes encoding the FimA, CP39, PtfA, ToxA and F1P2 antigens associated with porcine pneumonic pasteurellosis and progressive atrophic rhinitis (PAR) was constructed and harbored in an attenuated Salmonella Typhimurium, which was used as the vaccine candidate. The immune responses induced by this delivery strain were investigated in a murine model. Each antigen secreted from the delivery strain was confirmed by Western blot analysis. Thirty BALB/c mice were divided equally into two groups; group A were intranasally inoculated with the mixture of the five delivery strains, and group B were inoculated with sterile PBS. In group A, all antigen-specific serum IgG were significantly increased compared to those of group B from the 2nd week post-inoculation (WPI) till the 8th WPI. All antigen-specific mucosal IgA in group A were also significantly greater than those of group B. In addition, the significant splenic lymphocyte proliferative responses, the elevations of CD3(+)CD4(+), CD3(+)CD8(+) and B-cell populations, and the induction of IFN-γ expression in group A were observed. In conclusion, the mixture of five delivery strains expressing specific antigen for these diseases was found to be capable of inducing significant humoral and cellular immune responses.

Regeneration of toxigenic Pasteurella multocida induced severe turbinate atrophy in pigs detected by computed tomography.

BACKGROUND: Atrophic rhinitis is a widely prevalent infectious disease of swine caused by Bordetella bronchiseptica and Pasteurella multocida. The course of the disease is considered to be different depending on the principal aetiological agents distinguishing B. bronchiseptica induced non-progressive and toxigenic P. multocida produced progressive forms. In order to compare the pathological events of the two forms of the disease, the development of nasal lesions has longitudinally been studied in pigs infected by either B. bronchiseptica alone or B. bronchiseptica and toxigenic P. multocida together using computed tomography to visualise the nasal structures. RESULTS: B. bronchiseptica infection alone caused moderately severe nasal turbinate atrophy and these lesions completely regenerated by the time of slaughter. Unexpectedly, complete regeneration of the bony structures of the nasal cavity was also observed in pigs infected by B. bronchiseptica and toxigenic P. multocida together in spite of seeing severe turbinate atrophy in most of the infected animals around the age of six weeks. CONCLUSIONS: B. bronchiseptica mono-infection has been confirmed to cause only mild to moderate and transient lesions, at least in high health status pigs. Even severe turbinate atrophy induced by B. bronchiseptica and toxigenic P. multocida combined infection is able to be reorganised to their normal anatomical structure. Computed tomography has further been verified to be a useful tool to examine the pathological events of atrophic rhinitis in a longitudinal manner.

aroA deleted Bordetella bronchiseptica inspiring robust mucosal immune response and provide full protection against intranasal challenge.

Bordetella bronchiseptica is a Gram-negative respiratory pathogen responsible for atrophic rhinitis and bronchopneumonia in swine. Several vaccines aimed at preventing B. bronchiseptica have been used, but a safe and efficient live vaccine for use in piglets remains elusive. In this study, we constructed an aroA-deleted B. bronchiseptica strain (QH0814) and evaluated its safety and protective efficiency in piglets. Lung lesion scores in QH0814-immunized piglets post-challenge were significantly lower than those in piglets immunized with the parent strain (P<0.05). Immunization with QH0814 induced a vigorous immune response, especially at the mucosal surface of the respiratory tract. IgA titers in bronchoalveolar lavage fluid (BALF) and serum were significantly higher in the QH0814-immunized group compared to the inactivated-vaccine-immunized group. Piglets immunized with QH0814 were better protected than those in the inactivated-vaccine and negative control groups. The clinical symptoms, histopathological changes and immune responses elicited in the piglets were recorded. The results of this study suggest that QH0814 was able to confer complete protection against B. bronchiseptica infection and could thus be used as a candidate attenuated live vaccine against B. bronchiseptica in piglets.

A genome-wide scan for quantitative trait loci affecting respiratory disease and immune capacity in Landrace pigs.

Respiratory disease is the most important health concern for the swine industry. Genetic improvement for disease resistance is challenging because of the difficulty in obtaining good phenotypes related with disease resistance; however, identification of genes or markers associated with disease resistance can help in the genetic improvement of pig health. The purpose of our study was to investigate whether quantitative trait loci (QTL) associated with disease resistance were segregated in a purebred population of Landrace pigs that had been selected for meat production traits and mycoplasmal pneumonia of swine (MPS) scores over five generations. We analysed 1395 pigs from the base to the fifth generation of this population. Two respiratory disease traits [MPS scores and atrophic rhinitis (AR) scores] and 11 immune-capacity traits were measured in 630-1332 animals at 7 weeks of age and when the animal's body weight reached 105 kg. Each of the pigs, except sires in the base population, was genotyped using 109 microsatellite markers, and then, QTL analysis of the full-sib family population with a multi-generational pedigree structure was performed. Variance component analysis was used to detect QTL associated with MPS or AR scores, and the logarithm of odds (LOD) score and genotypic heritability of the QTL were estimated. Five significant (LOD > 2.51) and 18 suggestive (LOD > 1.35) QTL for respiratory disease traits and immune-capacity traits were detected. The significant QTL for Log-MPS score, located on S. scrofa chromosome 2, could explain 87% of the genetic variance of this score in this analysis. This is the first report of QTL associated with respiratory disease lesions.

Detection of urease-negative Bordetella bronchiseptica from the field.

Four urease-negative Bordetella bronchiseptica isolates originating from pigs were examined by phenotypic and molecular methods. The phenotypic properties of the isolates were in harmony with the data of the literature, except for the lack of urease activity in conventional tube test, API 20 NE and Diatabs™ assays. Using genotypic methods, the urease-negative isolates did not differ from the urease-positive reference strain. They were positive in species-specific and ureC PCR, and all strains showed uniform bands in PCR-RFLP studies of flaA genes. The reason for the lack of urease activity, a characteristic considered species specific for B. bronchiseptica, needs to be studied further. The finding underlines the significance of genotyping when the phenotypic identification of B. bronchiseptica seems questionable.

Kinetics of the response of four positive acute phase proteins in pigs experimentally infected with toxigenic Pasteurella multocida.

In the present study, acute phase proteins (APP) responses in pigs after infection with toxigenic strain of Pasteurella multocida (Pm) were evaluated. Twelve piglets from a herd free from toxigenic Pm were used. Six of them were infected intranasally with Pm. CRP, Hp, SAA and Pig-MAP concentrations were measured using commercial ELISA tests. CRP and Hp were significantly induced from 2 days post inoculation (dpi). The concentration of Hp in inoculated pigs remained elevated until the end of the study. The concentrations of SAA and Pig-MAP increased significantly from 3 dpi, and remained elevated to 5 or 7 dpi, respectively. Strong correlations were observed between concentration of Hp or SAA and changes in the lungs. No correlations were found between levels of APP in serum and changes observed in the turbinates. On the basis of our investigation, we cannot state that evaluation of APP concentrations in serum may provide useful information about severity of atrophic rhinitis. However, the concentration of all investigated APP increased after inoculation. Thus, APP-measurements may reveal ongoing infection. Monitoring of APP concentrations in the pig herds may help to pinpoint infected animals even before clinical signs are present. If found, these "APP-high" animals may be chosen next for pathogen-specific diagnostics. Early diagnosis and therapy may prevent the infection from spreading in the herd. Moreover, monitoring of APP concentrations in serum may be useful for selecting clinically healthy pigs before integration into an uninfected herd. Future studies should focus on the possibility of distinguishing infected and non-infected pigs under field conditions.

Expression of 4 truncated fragments of Pasteurella multocida toxin and their immunogenicity.

Pasteurella multocida toxin (PMT) is a poor antigen that becomes more immunogenic after its native structure has been destroyed. In contrast, partially truncated PMT proteins, which are predicted to be good antigens when used as a vaccine, might be used to improve the control of atrophic rhinitis in pigs. In this study, 4 truncated PMT fragments were expressed in Escherichia coli, and those 4 fragments were inoculated into mice to produce the polyclonal antibodies. The results of an enzyme-linked immunosorbent assay (ELISA) revealed that #1 and #4 fragments were the most immunogenic. Immunized mice were subsequently challenged intraperitoneally with P. multocida type D. Five of the eight #1 fragment-immunized mice showed some protection against death and bacterial clearance. Pigs immunized with #1 fragment produced no or mild atrophic rhinitis (turbinate conchal score) after challenge, suggesting that this #1 fragment could be a good candidate for a subunit recombinant-type vaccine.

Genetic diversity of porcine Pasteurella multocida strains from the respiratory tract of healthy and diseased swine.

A total of 382 porcine Pasteurella multocida strains, isolated from cases of pneumonia and progressive atrophic rhinitis (PAR) as well as from clinically healthy pigs of more than 150 German husbandries were characterized by detection of virulence-associated genes (VAGs) and ribotyping to understand the relationships between "commensal" and "pathogenic" strains, enabling a rational choice of vaccine strains. The diversity of the strains according to VAGs was low and mainly limited to capsular type genes (capA: 53.4%; capD: 45.8%; capF: 0.3%; cap-negative: 0.5%; hssB: 95.3%), dermonecrotoxin gene toxA (3.4%), as well as adhesion-related genes pfhaB (20.9%) and hgbB (84.3%). Ribotyping identified 13 patterns, but the vast majority of strains (95.8%) clustered in only three of these, namely IA-1 (45.5%), IA-7 (30.1%), and IIA-1 (20.2%). Pattern IA-1 was associated with capD(+) strains (93.6%) and harboured the majority of toxA(+) strains (84.6%). Pattern IA-7 mostly contained pfhaB(-), toxA(-)capA(+) strains (93.9%), while pattern IIA-1 was predominantly composed of pfhaB(+), toxA(-)capA(+) strains (87.0%). Clinical strains associated with pneumonia or PAR shared the above mentioned major ribotypes in comparable proportions with strains derived from healthy pigs, suggesting P. multocida to act more as an opportunistic than as an obligate pathogen in pigs. The limited number of subpopulations may either reflect a recent evolution of P. multocida in pigs or a selection by means of horizontal transfer of capsular genes, toxA or pfhaB. These data enforce further phylogenetic and epidemiological studies, examining the properties of different subpopulations of porcine P. multocida strains as well as factors of the porcine hosts themselves, which might be involved in disease susceptibility.

Efficacy of a novel Pasteurella multocida vaccine against progressive atrophic rhinitis of swine.

The efficacy of a novel vaccine composed of three short recombinant subunit Pasteurella multocida toxin (PMT) proteins in combination with a bi-valent P. multocida whole-cell bacterin (rsPMT-PM) was evaluated in field studies for prevention and control of progressive atrophic rhinitis (PAR) of swine at 15 conventional farrow-to-finish farms. Experimental piglets that were immunized twice with the rsPMT-PM vaccine developed detectable titers of neutralizing antibodies (greater than 1:8) that prevented the growth retardation and pathological lesions typically observed following challenge with authentic PMT. A total of 542 sows were vaccinated once or twice prior to parturition and serum neutralizing antibody titers were evaluated. Both single and double vaccination protocols induced neutralizing antibody titers of 1:16 or higher in 62% and 74% of sows, respectively. Notably, neither sows nor piglets at a farm experiencing a severe outbreak of PAR at the time of the vaccination trial had detectable antibody titers, but antibody titers increased significantly to 1:16 or higher in 40% of sows following double vaccination. During the year after vaccination, clinical signs of PAR decreased in fattening pigs and growth performance improved sufficiently to reduce the rearing period until marketing by 2 weeks. Collectively, these results indicate that the rsPMT-PM vaccine could be used to provide protective immunity for controlling the prevalence and severity of PAR among farm-raised swine.

Atrophic rhinitis vaccine composition triggers different serological profiles that do not correlate with protection.

Atrophic rhinitis (AR) is a widespread and economically important disease of swine caused by Bordetella bronchiseptica and Pasteurella multocida. It can be controlled by vaccination. This study investigates the effect of altering the composition (adjuvants and/or addition of formalin-inactivated P. multocida toxin, fPMT) of conventional vaccines on the serological profile and on protection against AR in swine. A significantly higher B. bronchiseptica specific antibody titre was detected for vaccines with novel immunostimulants, the best being Montanide IMS 1313 (1:630 compared to 1:274 obtained with alum). The highest B. bronchiseptica antibody titre was demonstrated for a combination of B. bronchiseptica--fPMT, while PMT antibody titre was highest for monovalent fPMT (both adjuvanted with IMS 1313). The AR-specific antibodies were transmitted from dams to their offspring in similar titres and with the same hierarchy of effectiveness. After a B. bronchiseptica--P. multocida bacterial challenge, piglets from dams vaccinated with fPMT combined with B. bronchiseptica or B. bronchiseptica--P. multocida bacterins showed the lowest nasal lesions scores (4.5 and 3.2, respectively, out of a possible maximum score of 18). These combinations, both of which were adjuvanted with IMS 1313, gave the best protection against experimentally induced AR. Our results show that the adjuvant and the antigen composition of the vaccine strongly affect seroconversion, and that the AR-specific antibody titre does not necessarily correlate with the degree of protection.

Prevalence of clinical signs of disease in Danish finisher pigs.

Between December 1999 and February 2001, two visits, eight weeks apart, were made to 90 herds of Danish finisher pigs. The prevalence of clinical signs was recorded by three veterinary technicians from the Danish Bacon and Meat Council according to a standardised procedure; they had been trained and their observations were monitored and validated before and during the study. A total of 154,347 finisher pigs were examined and 22,136 clinical signs were recorded. Vices accounted for 43 per cent of the signs. The highest mean prevalence was observed for ear necrosis (4.44 per cent), followed by respiratory signs (2.17 per cent), lameness (1.92 per cent), other skin diseases (1.73 per cent), tail bites (1.26 per cent), umbilical hernia (0.78 per cent), flank bites (0.52 per cent), diarrhoea (0.27 per cent), respiratory distress (0.12 per cent), atrophic rhinitis (0.10 per cent), recumbency (0.09 per cent) and central nervous disease (0.05 per cent). The prevalence of atrophic rhinitis was higher in conventional herds than in specific pathogen-free herds. The prevalence of clinical signs of atrophic rhinitis was higher among finishers weighing 51 to 75 kg than among finishers weighing up to 50 kg, and the prevalence of respiratory signs was higher among finishers weighing 51 to 75 kg then among finishers weighing 76 to 100 kg.

Expression of the dermonecrotic toxin by Bordetella bronchiseptica is not necessary for predisposing to infection with toxigenic Pasteurella multocida.

This experiment was designed to determine whether a Bordetella bronchiseptica mutant that does not produce dermonecrotic toxin (DNT) is still capable of predisposing pigs to infection with toxigenic Pasteurella multocida. Three groups of pigs were initially inoculated intranasally with a wild type B. bronchiseptica that produces DNT, an isogenic mutant of B. bronchiseptica that does not produce DNT, or PBS. All pigs were then challenged intranasally with a toxigenic strain of P. multocida 4 days later. P. multocida was recovered infrequently and in low numbers from pigs initially inoculated with PBS, and no turbinate atrophy was present in these pigs. P. multocida was isolated in similar numbers from the pigs initially inoculated with either the wild type or the DNT mutant of B. bronchiseptica, and turbinate atrophy of a similar magnitude was also seen in pigs from both of these groups. Thus, although the DNT has been shown to be responsible for much of the pathology seen during infection with B. bronchiseptica by itself, infection with non-DNT-producing strains can still predispose to secondary respiratory infections with P. multocida.

Analytical verification of a multiplex PCR for identification of Bordetella bronchiseptica and Pasteurella multocida from swine.

Bordetella bronchiseptica and Pasteurella multocida are etiologic agents of progressive atrophic rhinitis (PAR) and bronchopneumonia in swine. Only dermonecrotic toxin-producing strains of P. multocida play a role in atrophic rhinitis while both toxigenic and nontoxigenic strains have been associated with pneumonia. Monitoring and investigation of outbreaks involving these bacteria require sensitive and accurate identification and reliable determination of the toxigenic status of P. multocida isolates. In the present study, we report the development, optimization, and performance characteristics of a multiplex PCR assay for simultaneous amplification of up to three different targets, one common to all P. multocida strains, one found only in toxigenic P. multocida strains, and one common to B. bronchiseptica strains. Based on analysis of 94 P. multocida isolates (31 toxigenic) and 126 B. bronchiseptica isolates assay sensitivity is 100% for all amplicons. Evaluation of 22 isolates of other bacterial genera and species commonly found in the swine respiratory tract demonstrated a specificity of 100% for all gene targets. The limit of detection for simultaneous amplification of all targets is 1-10pg of DNA per target, corresponding to a few hundred genomes or less. Amplicon mobility in agarose gels and sequence analysis indicate the amplicons are highly stable. The data presented establish this multiplex PCR as a reliable method for identification of B. bronchiseptica and both toxigenic and nontoxigenic P. multocida that may greatly simplify investigations of swine PAR and bronchopneumonia.

Immunogenicity and efficacy of three recombinant subunit Pasteurella multocida toxin vaccines against progressive atrophic rhinitis in pigs.

Three short fragments of recombinant subunit Pasteurella multocida toxin (rsPMT) were constructed for evaluation as candidate vaccines against progressive atrophic rhinitis (PAR) of swine. PMT-specific antibody secreting cells and evidence of cellular immunity were detected in rsPMT-immunized pigs following authentic PMT challenge or homologous antigen booster. Piglets immunized with rsPMT fragments containing either the N-terminal or the C-terminal portions of PMT developed high titers of neutralizing antibodies. Pregnant sows immunized with rsPMT had higher levels of maternal antibodies in their colostrum than did those immunized with a conventional PAR-toxoid vaccine. Offspring from rsPMT vaccinated sows had better survival after challenge with a five-fold lethal dose of authentic PMT and had better growth performance after challenge with a sublethal dose of toxin. Our findings indicate these non-toxic rsPMT proteins are attractive candidates for development of a subunit vaccine against PAR in pigs.