Identification and characterization of novel immunogenic outer membrane proteins of Haemophilus parasuis serovar 5

Evaluation of immunoregulation and immunoprotective efficacy of Glaesserella parasuis histidine kinase QseC

QseC is a membrane sensor kinase that enables bacteria to perceive autoinducers -3, adrenaline, and norepinephrine to initiate downstream gene transcription. In this study, we found that the QseC protein of Glaesserella parasuis can serve as an effective antigen to activate the host's immune response. Therefore, we investigated the immunogenicity and host protective effect of this protein. ELISA and indirect immunofluorescence results showed that QseC protein can induce high titer levels of humoral immunity in mice and regularly generate specific serum antibodies. We used MTS reagents to detect lymphocyte proliferation levels and found that QseC protein can cause splenic lymphocyte proliferation with memory and specificity. Further immunological analysis of the spleen cell supernatant revealed significant upregulation of levels of IL-1β, IL-4 and IFN-γ in the QseC + adjuvant group. In the mouse challenge experiment, it was found that QseC + adjuvant can provide effective protection. The results of this study demonstrate that QseC protein provides effective protection in a mouse model and has the potential to serve as a candidate antigen for a novel subunit vaccine for further research.

Salmonella enterica serovar Choleraesuis vector outperforms alum as an adjuvant, increasing a cross-protective immune response against Glaesserella parasuis

The adjuvant and/or vector significantly affect a vaccine's efficacy. Although traditional adjuvants such as alum have contributed to vaccine development, deficiencies in the induction of cellular and mucosal immunity have limited their further promotion. Salmonella vectors have unique advantages for establishing cellular and mucosal immunity due to mucosal pathways of invasion and intracellular parasitism. In addition, Salmonella vectors can activate multiple innate immune pathways, thereby promoting adaptive immune responses. In this work, the attenuated Salmonella enterica serovar Choleraesuis (S. Choleraesuis) vector rSC0016 was used to deliver the conserved protective antigen HPS_06257 of Glaesserella parasuis (G. parasuis), generating a novel recombinant strain rSC0016(pS-HPS_06257). The rSC0016(pS-HPS_06257) can express and deliver the HPS_06257 protein to the lymphatic system of the host. In comparison to HPS_06257 adjuvanted with alum, rSC0016(pS-HPS_06257) significantly increased TLR4 and TLR5 activation in mice as well as the levels of proinflammatory cytokines. In addition, rSC0016 promoted a greater degree of maturation in bone marrow-derived dendritic cells (BMDCs) than alum. The specific humoral, mucosal, and cellular immune responses against HPS_06257 in mice immunized with rSC0016(pS-HPS_06257) were significantly higher than those of HPS_06257 adjuvanted with alum. HPS_06257 delivered by the S. Choleraesuis vector induces a Th1-biased Th1/Th2 mixed immune response, while HPS adjuvanted with alum can only induce a Th2-biased immune response. HPS_06257 adjuvanted with alum only causes opsonophagocytic activity (OPA) responses against a homologous strain (G. parasuis serotype 5, GPS5), whereas rSC0016(pS-HPS_06257) could generate cross-OPA responses against a homologous strain and a heterologous strain (G. parasuis serotype 12, GPS12). Ultimately, HPS_06257 adjuvanted with alum protected mice against lethal doses of GPS5 challenge by 60 % but failed to protect mice against lethal doses of GPS12. In contrast, mice immunized with rSC0016(pS-HPS_06257) had 100 % or 80 % survival when challenged with lethal doses of GPS5 or GPS12, respectively. Altogether, the S. Choleraesuis vector rSC0016 could potentially generate an improved innate immune response and an improved adaptive immunological response compared to the traditional alum adjuvant, offering a novel concept for the development of a universal G. parasuis vaccine.

Molecular Characterization and Phylogenetic Analysis of Outer membrane protein P2 (OmpP2) of Glaesserella (Haemophilus) parasuis Isolates in Central State of Peninsular Malaysia

Glaesserella (Haemophilus) parasuis, the etiological agent of Glässer's disease, is an economically significant pathogen commonly associated with serofibrinous polyserositis, arthritis, fibrinous bronchopneumonia and/or meningitis. This study is the first attempt to molecularly characterize and provide a detailed overview of the genetic variants of G. parasuis present in Malaysia, in reference to its serotype, virulence-associated trimeric autotransporters (vtaA) gene and outer membrane protein P2 (OmpP2) gene. The G. parasuis isolates (n = 11) from clinically sick field samples collected from two major pig producing states (Selangor and Perak) were selected for analysis. Upon multiplex PCR, the majority of the isolates (eight out of 11) were identified to be serotype 5 or 12, and interestingly, serotypes 3, 8 and 15 were also detected, which had never been reported in Malaysia prior to this. Generally, virulent vtaA was detected for all isolates, except for one, which displayed a nonvirulent vtaA. A phylogenetic analysis of the OmpP2 gene revealed that the majority of Malaysian isolates were clustered into genotype 1, which could be further divided into Ia and Ib, while only one isolate was clustered into genotype 2.

Screening of linear B-cell epitopes and its proinflammatory activities of Haemophilus parasuis outer membrane protein P2

Haemophilus parasuis is a commensal organism of the upper respiratory tract of pigs, but virulent strains can cause Glässer's disease, resulting in significant economic losses to the swine industry. OmpP2 is an outer membrane protein of this organism that shows considerable heterogeneity between virulent and non-virulent strains, with classification into genotypes I and II. It also acts as a dominant antigen and is involved in the inflammatory response. In this study, 32 monoclonal antibodies (mAbs) against recombinant OmpP2 (rOmpP2) of different genotypes were tested for reactivity to a panel of OmpP2 peptides. Nine linear B cell epitopes were screened, including five common genotype epitopes (Pt1a, Pt7/Pt7a, Pt9a, Pt17, and Pt19/Pt19a) and two groups of genotype-specific epitopes (Pt5 and Pt5-II, Pt11/Pt11a, and Pt11a-II). In addition, we used positive sera from mice and pigs to screen for five linear B-cell epitopes (Pt4, Pt14, Pt15, Pt21, and Pt22). After porcine alveolar macrophages (PAMs) were stimulated with overlapping OmpP2 peptides, we found that the epitope peptides Pt1 and Pt9, and the loop peptide Pt20 which was adjacent epitopes could all significantly upregulated the mRNA expression levels of IL-1α, IL-1β, IL-6, IL-8, and TNF-α. Additionally, we identified epitope peptides Pt7, Pt11/Pt11a, Pt17, Pt19, and Pt21 and loop peptides Pt13 and Pt18 which adjacent epitopes could also upregulate the mRNA expression levels of most proinflammatory cytokines. This suggested that these peptides may be the virulence-related sites of the OmpP2 protein, with proinflammatory activity. Further study revealed differences in the mRNA expression levels of proinflammatory cytokines, including IL-1β and IL-6, between genotype-specific epitopes, which may be responsible for pathogenic differences between different genotype strains. Here, we profiled a linear B-cell epitope map of the OmpP2 protein and preliminarily analyzed the proinflammatory activities and effects of these epitopes on bacterial virulence, providing a reliable theoretical basis for establishing a method to distinguish strain pathogenicity and to screen candidate peptides for subunit vaccines.

TurboID Screening of the OmpP2 Protein Reveals Host Proteins Involved in Recognition and Phagocytosis of Glaesserella parasuis by iPAM Cells

Glaesserella parasuis is a common bacterium in the porcine upper respiratory tract that causes severe Glasser's disease, which is characterized by polyarthritis, meningitis, and fibrinous polyserositis. TurboID is an enzyme that mediates the biotinylation of endogenous proteins that can fuse with proteins of interest to label protein interactors and local proteomes. To reveal the host proteins that interact with outer membrane protein P2 (OmpP2) by TurboID-mediated proximity labeling in immortalized porcine alveolar macrophage iPAM cells, 0.1 and 2.58 mg/mL His-tagged TurboID-OmpP2 and TurboID recombinant proteins were expressed and purified. By mass spectrometry, we identified 948 and 758 iPAM cell proteins that interacted with His-TurboID-OmpP2 and His-TurboID, respectively. After removal of background proteins through comparison with the TurboID-treated group, 240 unique interacting proteins were identified in the TurboID-OmpP2-treated group. Ultimately, only four membrane proteins were identified, CAV1, ARF6, PPP2R1A, and AP2M1, from these 240 host proteins. Our data indicated that CAV1, ARF6, and PPP2R1A could interact with OmpP2 of G. parasuis, as confirmed by coimmunoprecipitation assay. Finally, we found that CAV1, ARF6, and PPP2R1A were involved in the recognition and phagocytosis of G. parasuis serotype 5 by iPAM cells by using overexpression and RNA interference assays. This study provides first-hand information regarding the interaction of the iPAM cell proteomes with G. parasuis OmpP2 protein by using the TurboID proximity labeling system and identifies three novel host membrane proteins involved in the recognition and phagocytosis of G. parasuis by iPAM cells. These results provide new insight for a better understanding of Glasser's disease pathogenesis. IMPORTANCE G. parasuis can cause serious Glasser's disease, which is characterized by polyarthritis, meningitis, and fibrinous polyserositis in pigs. It can cause high morbidity and mortality in swine herds and major economic losses to the global pig industry. Understanding the mechanism of interactions between alveolar macrophages and pathogenic G. parasuis is essential for developing effective vaccines and targeted drugs against G. parasuis. To reveal the host proteins interacting with OmpP2 by TurboID-mediated proximity labeling in immortalized porcine alveolar macrophage (iPAM) cells, we identified 240 unique proteins from iPAM cells that could interact with G. parasuis OmpP2. Among them, only four membrane proteins, CAV1, ARF6, PPP2R1A, and AP2M1, were identified, and further study showed that CAV1, ARF6, and PPP2R1A are involved in the recognition and phagocytosis of G. parasuis serotype 5 by iPAM cells. This study provides new insight into proteomic interactions between hosts and pathogenic microorganisms.

Metal Ion Periplasmic-Binding Protein YfeA of Glaesserella parasuis Induces the Secretion of Pro-Inflammatory Cytokines of Macrophages via MAPK and NF-κB Signaling through TLR2 and TLR4

The YfeA gene, belonging to the well-conserved ABC (ATP-binding cassette) transport system Yfe, encodes the substrate-binding subunit of the iron, zinc, and manganese transport system in bacteria. As a potential vaccine candidate in Glaesserella parasuis, the functional mechanisms of YfeA in the infection process remain obscure. In this study, vaccination with YfeA effectively protected the C56BL6 mouse against the G. parasuis SC1401 challenge. Bioinformatics analysis suggests that YfeA is highly conserved in G. parasuis, and its metal-binding sites have been strictly conserved throughout evolution. Stimulation of RAW 264.7 macrophages with YfeA verified that toll-like receptors (TLR) 2 and 4 participated in the positive transcription and expression of pro-inflammatory cytokines IL-1β, IL-6, and TNF-α. The activation of TLR2 and TLR4 utilized the MyD88/MAL and TRIF/TRAM pairs to initiate TLRs signaling. Furthermore, YfeA was shown to stimulate nuclear translocation of NF-κB and activated diverse mitogen-activated protein (MAP) kinase signaling cascades, which are specific to the secretion of particular cytokine(s) in murine macrophages. Separate blocking TLR2, TLR4, MAPK, and RelA (p65) pathways significantly decreased YfeA-induced pro-inflammatory cytokine production. In addition, YfeA-stimulated RAW 264.7 produces the pro-inflammatory hallmark, reactive oxygen species (ROS). In conclusion, our findings indicate that YfeA is a novel pro-inflammatory mediator in G. parasuis and induces TLR2 and TLR4-dependent pro-inflammatory activity in RAW 264.7 macrophages through P38, JNK-MAPK, and NF-κB signaling pathways.

Expression Analysis of Outer Membrane Protein HPS_06257 in Different Strains of Glaesserella parasuis and Its Potential Role in Protective Immune Response against HPS_06257-Expressing Strains via Antibody-Dependent Phagocytosis

Simple Summary

Glaesserella parasuis, one of the opportunistic pathogens causing Glässer’s disease in piglets, has become a significant concern for pig farmers. Vaccination has been shown to be effective in preventing Glaesserella parasuis infection by inducing the protective immune response. Notably, a humoral immune response plays an important role in protection of Glaesserella parasuis infection. The mechanism of protection by antibodies has been shown to be associated with antibody-opsonized phagocytosis, which facilitates uptake of Glaesserella parasuis by phagocytes such as macrophages. Outer membrane proteins of Glaesserella parasuis, as the promising candidates, are often chosen to develop subunit vaccines. HPS_06257 is one of the outer membrane proteins that has been shown to confer protection against Glaesserella parasuis infection. However, little is known about the role of HPS_06257 in the protective immune response. We demonstrate that antibody-dependent phagocytosis is involved in the protective effects of HPS_06257. Our findings extend our understanding of how antibody-dependent phagocytosis may contribute to the immune protection afforded by other outer membrane proteins. Thus, our study provides insight into the protective antigens of Glaesserella parasuis and useful information for the development of novel vaccines to prevent Glaesserella parasuis infection.

Abstract

HPS_06257 has been identified as an important protective antigen against Glaesserella parasuis infection. However, little is known about the role of HPS_06257 in the protective immune response. A whole-genome data analysis showed that among 18 isolates of Glaesserella parasuis, 11 were positive for the HPS_06257 gene, suggesting that not every strain contains this gene. We used PCR to investigate the presence of the HPS_06257 gene among 13 reference strains and demonstrated that 5 strains contained the gene. A polyclonal antibody against HPS_06257 was generated with a recombinant protein to study the expression of HPS_06257 in those 13 strains. Consistent with the PCR data, five strains expressed HPS_06257, whereas eight strains were HPS_06257 null. We also compared the protective effects of HPS_06257 against an HPS_06257-expressing strain (HPS5) and an HPS_06257-null strain (HPS11). Immunization with HPS_06257 only protected against HPS5 and not HPS11. Moreover, phagocytosis of antibody-opsonized bacteria demonstrates that the antibody against HPS_06257 increased the phagocytosis of the HPS5 strain by macrophages but not the phagocytosis of the HPS11 strain, suggesting that antibody-dependent phagocytosis is responsible for the protective role exerted by HPS_06257 in the immune response to HPS5. Our data also show that the antibody against HPS_06257 increased the phagocytosis of the other HPS_06257-expressing strains by macrophages but not that of HPS_06257-null strains. In summary, our findings demonstrate that antibody-dependent phagocytosis contributes to the protective immune response induced by immunization with HPS_06257 against HPS_06257-expressing strains.

Evaluation of host and bacterial gene modulation during Lawsonia intracellularis infection in immunocompetent C57BL/6 mouse model

BACKGROUND

Proliferative enteritis caused by Lawsonia intracellularis undermines the economic stability of the swine industry worldwide. The development of cost-effective animal models to study the pathophysiology of the disease will help develop strategies to counter this bacterium.

OBJECTIVES

This study focused on establishing a model of gastrointestinal (GI) infection of L. intracellularis in C57BL/6 mice to evaluate the disease progression and lesions of proliferative enteropathy (PE) in murine GI tissue.

METHODS

We assessed the murine mucosal and cell-mediated immune responses generated in response to inoculation with L. intracellularis.

RESULTS

The mice developed characteristic lesions of the disease and shed L. intracellularis in the feces following oral inoculation with 5 × l07 bacteria. An increase in L. intracellularis 16s rRNA and groEL copies in the intestine of infected mice indicated intestinal dissemination of the bacteria. The C57BL/6 mice appeared capable of modulating humoral and cell-mediated immune responses to L. intracellularis infection. Notably, the expression of genes for the vitamin B12 receptor and for secreted and membrane-bound mucins were downregulated in L. intracellularis -infected mice. Furthermore, L. intracellularis colonization of the mouse intestine was confirmed by the immunohistochemistry and western blot analyses.

CONCLUSIONS

This is the first study demonstrating the contributions of bacterial chaperonin and host nutrient genes to PE using an immunocompetent mouse model. This mouse infection model may serve as a platform from which to study L. intracellularis infection and develop potential vaccination and therapeutic strategies to treat PE.

Application of mouse model for evaluation of recombinant LpxC and GmhA as novel antigenic vaccine candidates of Glaesserella parasuis serotype 13

Glaesserella parasuis (G. parasuis) has been one of the bacteria affecting the large-scale swine industry. Lack of an effective vaccine has limited control of the disease, which has an effect on prevalence. In order to improve the cross-protection of vaccines, development on subunit vaccines has become a hot spot. In this study, we firstly cloned the lpxC and gmhA genes from G. parasuis serotype 13 isolates, and expressed and purified their proteins. The results showed that LpxC and GmhA can stimulate mice to produce IgG antibodies. Through testing the cytokine levels of interleukin 4 (IL-4), IL-10 and interferon-γ (IFN-γ), it is found that recombinant GmhA, the mixed LpxC and GmhA can stimulate the body to produce Th1 and Th2 immune responses, while recombinant LpxC and inactivated bacteria can only produce Th2 immune responses. On the protection rate for mice, recombinant LpxC, GmhA and the mixture of LpxC and GmhA can provide 50%, 50% and 60% protection for lethal dose of G. parasuis infection, respectively. The partial protection achieved by the recombinant LpxC and GmhA supports their potential as novel vaccine candidate antigens against G. parasuis.

Inhibition of Haemophilus parasuis by berberine and proteomic studies of its mechanism of action

Haemophilus parasuis is the main agent of Glässer's disease, which causes substantial losses in pig production. However, the pathogenic mechanism and virulence factors of H. parasuis have not been fully determined. In this study, berberine is shown to have a good therapeutic effect in vivo against H. parasuis; the minimal inhibitory concentration (MIC) in vitro was 2 μg/mL. Berberine inhibited H. parasuis adhesion to and invasion of PK-15 pig kidney cells. Proteomics studies of H. parasuis after berberine treatment identified a total of 97 differentially-expressed proteins; 35 upregulated and 62 downregulated. Bioinformatics analysis showed that berberine may inhibit the growth of H. parasuis by affecting outer membrane proteins, transferrins, and energy metabolism. This study provides a basis for the development of new antibacterial agents.

Evaluation of the recombinant proteins RlpB and VacJ as a vaccine for protection against Glaesserella parasuis in pigs

BACKGROUND

Glaesserella parasuis, the causative agent of Glӓsser's disease, is widespread in swine globally resulting in significant economic losses to the swine industry. Prevention of Glӓsser's disease in pigs has been plagued with an inability to design broadly protective vaccines, as many bacterin based platforms generate serovar or strain specific immunity. Subunit vaccines are of interest to provide protective immunity to multiple strains of G. parasuis. Selected proteins for subunit vaccination should be widespread, highly conserved, and surface exposed.

RESULTS

Two candidate proteins for subunit vaccination (RlpB and VacJ) against G. parasuis were identified using random mutagenesis and an in vitro organ culture system. Pigs were vaccinated with recombinant RlpB and VacJ, outer membrane proteins with important contributions to cellular function and viability. Though high antibody titers to the recombinant proteins and increased interferon-γ producing cells were found in subunit vaccinated animals, the pigs were not protected from developing systemic disease.

CONCLUSIONS

It appears there may be insufficient RlpB and VacJ exposed on the bacterial surface for antibody to bind, preventing high RlpB and VacJ specific antibody titers from protecting animals from G. parasuis. Additionally, this work confirms the importance of utilizing the natural host species when assessing the efficacy of vaccine candidates.

Surface-exposed loops L7 and L8 of Haemophilus (Glaesserella) parasuis OmpP2 contribute to the expression of proinflammatory cytokines in porcine alveolar macrophages

Outer membrane protein P2 (OmpP2) of the virulent Haemophilus (Glaesserella) parasuis has been shown to induce the release of proinflammatory cytokines. The OmpP2 protein is composed of eight or nine surface-exposed loops, but it is unclear which of them participates in the OmpP2-induced inflammatory response. In this study, we synthesized linear peptides corresponding to surface-exposed loops L1–L8 of OmpP2 from the virulent H. parasuis SC096 strain to stimulate porcine alveolar macrophages (PAMs) in vitro. We found that both L7 and L8 significantly upregulated the mRNA expression of interleukin (IL)-1α, IL-1β, IL-6, IL-8, IL-17, and IL-23 and the chemokines CCL-4 and CCL-5 in a time- and dose-dependent manner. Additionally, we constructed ompP2ΔLoop7 and ompP2ΔLoop8 mutant SC096 strains and extracted their native OmpP2 proteins to stimulate PAMs. These mutant proteins induced significantly less mRNA expression of inflammatory cytokines than SC096 OmpP2. Next, the amino acid sequences of L7 and L8 from 15 serovars of H. parasuis OmpP2 were aligned. These sequences were relatively conserved among the most virulent reference strains, suggesting that L7 and L8 are the most active peptides of the OmpP2 protein. Furthermore, L7 and L8 significantly upregulated the NF-κB and AP-1 activity levels based on luciferase reporter assays in a dose-dependent manner. Therefore, our results demonstrated that both surface-exposed loops L7 and L8 of H. parasuis OmpP2 induced the expression of proinflammatory cytokines possibly by activating the NF-κB and MAPK signalling pathways in cells infected by H. parasuis.

An immunoproteomic approach to identify antigenic proteins in Nocardia farcinica IFM 10152

Nocardia farcinica is the etiological agent of nocardiosis, leading to serious pulmonary or systemic infections. To uncover virulence factors and early diagnostic markers, secreted proteins of N. farcinica IFM 10152 were analyzed using an immunoproteome-based approach. A total of 5 proteins were identified by matrix-assisted laser desorption (MALDI-TOF-MS). Bioinformatic analyses showed that the identified proteins were involved in defense against the host innate immune system and required for pathogenesis. All proteins were expressed in E. coli and antigenicity was analyzed with Western blot. To our knowledge, these proteins with antigenicity were identified for the first time in N. farcinica and they may help elucidate the pathogenesis underlying Nocardia and provide potential future diagnostic markers.

Characterization of Haemophilus Parasuis Serovar 2 CL120103, a Moderately Virulent Strain in China

Haemophilus parasuis is an important bacterium affecting pigs, causing Glässer’s disease. To further characterize this species, we determined the complete genomic sequence of H. parasuis CL120103, which was isolated from diseased pigs. The strain H. parasuis CL120103 was identified as serovar 2. The size of the largest scaffold is 2,326,318 bp and contains 145 large contigs, with the N50 contig being 20,573 bp in length. The complete genome of H. parasuis CL120103 is 2,305,354 bp in length with 39.97% GC content and contains 2227 protein-coding genes, 19 ribosomal rRNA operons and 60 tRNA genes. Sequence similarity of the genome of H. parasuis CL120103 to the previously sequenced genome of H. parasuis was up to 96% and query cover to 86%. Annotation of the genome of H. parasuis CL120103 identified a number of genes encoding potential virulence factors. These virulence factors are involved in metabolism, adhesion, secretion and LPS biosynthesis. These related genes pave the way to better understand mechanisms underlying metabolic capabilities. The comprehensive genetic and phylogenetic analysis shows that H. parasuis is closely related to Actinobacillus pleuropneumoniae and provides a foundation for future experimental confirmation of the virulence and pathogen-host interactions in H. parasuis.

Identification of Cross Reactive Antigens of C. botulinum Types A, B, E & F by Immunoproteomic Approach

Diseases triggered by microorganisms can be controlled by vaccines, which need neutralizing antigens. Hence, it is very crucial to identify extremely efficient immunogens for immune prevention. Botulism, a fatal neuroparalytic disease, is caused by botulinum neurotoxins produced by the anaerobic, Gram-positive spore-forming bacteria, Clostridium botulinum. Food-borne botulism and iatrogenic botulism are caused by botulinum toxin. Wound botulism, infant botulism, and adult intestinal botulism are caused by primarily C. botulinum followed by secondary intoxication. To identify protective antigens, whole cell proteome of C. botulinum type B was separated by two-dimensional gel electrophoresis. 2-D gel of whole cell proteins was probed with hyper immune sera of whole cell proteins of C. botulinum types A, E, and F. Six cross immunoreactive proteins were identified. These immunoreactive proteins will be further tested for developing vaccines and serodiagnostic markers against botulism.

Identification of novel Haemophilus parasuis serovar 5 vaccine candidates using an immunoproteomic approach

Haemophilus parasuis is the aetiological agent of Glässer's disease, which is responsible for cases of fibrinous polyserositis, polyarthritis and meningitis. No vaccine is known that provides cross-protection against all serovars. The identification of novel immunoprotective antigens would undoubtedly contribute to the development of efficient subunit vaccines. In the present study, an immunoproteomic approach was used to analyze secreted proteins of H. parasuis and six proteins with high immunogenicity were identified. Five of them were successfully expressed, and their immunogenicity and protective efficacy were assessed in a mouse challenge model. All five proteins elicited strong humoral antibody and cellular immune responses in mice. They all effectively reduced the growth of H. parasuis in mouse organs and conferred different levels of protection (40-80%) against challenge. IgG subtype analysis revealed that the five proteins induce a bias toward a Th1-type immune response, and a significant increase was observed in the cytokine levels of IL-2, IFN-γ and Th2-specific IL-4 in the culture supernatants of splenocytes isolated from immunized mice. The results suggest that both Th1 and Th2 responses are involved in mediating protection. These data suggest that the five proteins could be potential subunit vaccine candidates for use to prevent H. parasuis infection.

BIOLOGICAL SIGNIFICANCE

Haemophilus parasuis can cause huge financial loss in the swine industry worldwide. There are still no vaccines which can provide cross-protection against all serovars. To address this need, we applied an immunoproteomic approach involving 2-DE, MALDI-TOF/TOF MS and Western-blot to identify the secreted proteins which may be able to provide immunoprotection to this disease. We identified six immunogenic proteins, and the immunogenicity and protective efficacy were validated. This result provides a foundation for developing novel subunit vaccines against Haemophilus parasuis.

Evaluation of immunogenicity and protective efficacy of recombinant outer membrane proteins of Haemophilus parasuis serovar 5 in a murine model

Glässer’s disease is an economically important infectious disease of pigs caused by Haemophilus parasuis. Few vaccines are currently available that could provide effective cross-protection against various serovars of H. parasuis. In this study, five OMPs (OppA, TolC, HxuC, LppC, and HAPS_0926) identified by bioinformatic approaches, were cloned and expressed as recombinant proteins. Antigenicity of the purified proteins was verified through Western blotting, and primary screening for protective potential was evaluated in vivo. Recombinant TolC (rTolC), rLppC, and rHAPS_0926 proteins showing marked protection of mice against H. parasuis infection, and were further evaluated individually or in combination. Mice treated with these three OMPs produced humoral and host cell-mediated responses, with a significant rise in antigen-specific IgG titer and lymphoproliferative response in contrast with the mock-immunized group. Significant increases were noted in CD4⁺, CD8⁺ T cells, and three cytokines (IL-2, IL-4, and IFN-γ) in vaccinated animals. The antisera against candidate antigens could efficiently impede bacterial survival in whole blood bactericidal assay against H. parasuis infection. The multi-protein vaccine induced more pronounced immune responses and offered better protection than individual vaccines. Our findings indicate that these three OMPs are promising antigens for the development of multi-component subunit vaccines against Glässer's disease.

Evaluation of recombinant protein superoxide dismutase of Haemophilus parasuis strain SH0165 as vaccine candidate in a mouse model

Haemophilus parasuis can cause a severe membrane inflammation disorder. It has been documented that superoxide dismutase (SOD) is a potential target to treat systemic inflammatory diseases. Therefore, we constructed an experimental H. parasuis subunit vaccine SOD and determined the protective efficacy of SOD using a lethal dose challenge against H. parasuis serovar 4 strain MD0322 and serovar 5 strain SH0165 in a mouse model. The results demonstrated that SOD could induce a strong humoral immune response in mice and provide significant immunoprotection efficacy against a lethal dose of H. parasuis serovar 4 strain MD0322 or serovar 5 strain SH0165 challenge. IgG subtype analysis indicated SOD protein could trigger a bias toward a Th1-type immune response and induce the proliferation of splenocytes and secretion of IL-2 and IFN-γ of splenocytes. In addition, serum in mice from the SOD-immunized group could inhibit the growth of strain MD0322 and strain SH0165 in the whole-blood killing bacteria assay. This is the first report that immunization of mice with SOD protein could provide protective effect against a lethal dose of H. parasuis serovar 4 and serovar 5 challenge in mice, which may provide a novel approach against heterogeneous serovar infection of H. parasuis in future.

Omp16-based vaccine encapsulated by alginate-chitosan microspheres provides significant protection against Haemophilus parasuis in mice

Haemophilus parasuis (H. parasuis) is the etiological agent of swine Glässer's disease, which leads to significant economic loss in swine industry over the world. Subunit vaccine based on outer membrane protein is one of the promising choices to protect pigs against H. parasuis infection despite low immunity efficiency. In this paper, outer membrane protein 16 (Omp16) of H. parasuis encapsulated by alginate-chitosan microspheres as antigen carriers was explored for the first time in a mouse model. Our results showed that the microspheres with Omp16 induced significant higher H. parasuis-specific antibodies, and higher titers of IL-2, IL-4, and IFN-γ than those by Omp16-FIA in treated mice (p<0.05). Moreover, H. parasuis load in the tissues from liver, spleen, and lung of mice immunized with microspheres containing Omp16 was significantly decreased (p<0.05) than that in the same counterpart tissues of control groups. In addition, 80% mice treated with Omp16 and 70% mice with Omp16-FIA were survived after challenged with H. parasuis virulent strain LY02 (serovar 5). Therefore, Omp16-based microsphere vaccine induces both humoral and cellular immune responses and provides promising protection against H. parasuis infection in mice.

Evaluation of glutathione-binding protein A of Haemophilus parasuis as a vaccine candidate in a mouse model

The virulent strains of Haemophilus parasuis are the causative agents of Glässer’s disease, which can cause systemic infection and result in polyserositis, meningitis and arthritis. The development of novel, effective vaccines would be beneficial to preventing H. parasuis infections. Here, we report a novel immunogenic protein, glutathione-binding protein A (GbpA), which can elicit a significant humoral antibody response and confer significant protection against challenge with a lethal dose of a highly virulent H. parasuis strain. The H. parasuis strain can be fully eliminated in the immunized mice. The results indicate that GbpA has the potential to be used as an effective component of a new vaccine against H. parasuis.

A vaccine based on a mutant transferrin binding protein B of Haemophilus parasuis induces a strong T-helper 2 response and bacterial clearance after experimental infection

This study aimed to characterize the type of immune response induced by an experimental vaccine based on a mutant Haemophilus parasuis transferrin binding protein (Tbp) B (Y167A) defective in its ability to bind porcine transferrin. Clinical and pathological signs, bacterial clearance, antibody response and the cytokine profile in alveolar macrophages and spleen after the vaccination and challenge of twenty-two colostrum-deprived pigs with 10(8) CFU of H. parasuis were analysed. Pigs vaccinated with Y167A were compared to those vaccinated with native TbpB (nTbpB), those treated with a commercial bacterin (CB) against Glässer's disease, those unvaccinated challenged (CH) and those unvaccinated unchallenged (UNCH) pigs. The rectal temperatures of Y167A pigs resembled those of UNCH pigs and were significantly lower than those of the nTbpB, CB and CH animals. A major reduction in pathological changes of the challenged pigs was observed in the Y167A group. H. parasuis was cleared from 88.9% of the samples from Y167A pigs versus 60.0% and 55.6% from those of the CB and nTbpB groups, respectively. The antibody response elicited by Y167A by ELISA was notably higher than that observed for nTbpB and CB pigs and was capable of preventing the expression and secretion of IL-8. The expression of IL-4 and IL-5, which were associated with the specific antibody levels, suggests that the main mechanism of protection conferred by Y167A vaccine is based on a strong T-helper 2 response.

Immune response to oligopeptide permease A (OppA) protein in pigs naturally and experimentally infected with Haemophilus parasuis

Haemophilus parasuis is an important swine pathogen that causes Glasser's disease, characterized by pneumonia, polyserositis and meningitis. Protection against H. parasuis infection is associated with the presence of homologous antibodies in serum. However, a H. parasuis antigen that can elicit a protective immune response against all H. parasuis strains has yet to be found. A novel immunogenic and species-specific H. parasuis protein was identified by screening H. parasuis whole cell proteins using swine convalescent sera. One protein of 52kDa was clearly immunodominant and conserved among different H. parasuis strains. This protein was further identified as an oligopeptide permease A (OppA). Because OppA elicited a specific antibody response in pigs that recovered from H. parasuis infection, we investigated its potential role in diagnostics and protective immunity. An ELISA test using recombinant OppA (rOppA) as its coating antigen was further developed and tested. H. parasuis specific antibodies to rOppA were detected in serum from convalescent pigs but not in serum from specific pathogen free (SPF) or conventional pigs. Pigs immunized with rOppA protein had robust serological responses. However, the antibodies were not protective against challenge infection. We conclude that OppA is a universal species-specific H. parasuis immunogen, and a good marker for previous systemic infection with H. parasuis.

Development and antigenic characterization of three recombinant proteins with potential for Glässer's disease prevention

Haemophilus parasuis is the causative agent of Glässer's disease, which causes high morbidity and mortality in piglets, leading to severe economic losses. The lack of a commercial vaccine against a broad spectrum of strains has limited the disease control. H. parasuis outer membrane proteins (OMPs) are potentially essential components for vaccine formulation. In this study, seven putative OMPs were selected from the annotated H. parasuis serovar 5 genome; they were predicted by bioinformatics and annotated as potential virulence-related factors. These proteins were cloned, expressed, and purified as His-tagged proteins. Antigenicity of the candidate proteins was assessed using Western blotting with convalescent sera against H. parasuis serovar 5. The immunogenicity of the seven OMPs was assessed in a guinea pig model. Except VacJ, all the other six recombinant proteins elicited a detectable antibody response. Antisera against four of the selected proteins effectively killed the bacteria in vitro. Three proteins (Omp26, VacJ, and HAPS_0742) were found to confer significant protection against challenge with a lethal dose of H. parasuis in a guinea pig model. The results suggest that these three proteins have a strong potential to be vaccine candidates against Glässer's disease.

Characterization and Vaccine Potential of Outer Membrane Vesicles Produced by Haemophilus parasuis

Haemophilus parasuis is a Gram-negative bacterium that colonizes the upper respiratory tract of swine and is capable of causing a systemic infection, resulting in high morbidity and mortality. H. parasuis isolates display a wide range of virulence and virulence factors are largely unknown. Commercial bacterins are often used to vaccinate swine against H. parasuis, though strain variability and lack of cross-reactivity can make this an ineffective means of protection. Outer membrane vesicles (OMV) are spherical structures naturally released from the membrane of bacteria and OMV are often enriched in toxins, signaling molecules and other bacterial components. Examination of OMV structures has led to identification of virulence factors in a number of bacteria and they have been successfully used as subunit vaccines. We have isolated OMV from both virulent and avirulent strains of H. parasuis, have examined their protein content and assessed their ability to induce an immune response in the host. Vaccination with purified OMV derived from the virulent H. parasuis Nagasaki strain provided protection against challenge with a lethal dose of the bacteria.

[Proteomics in infectious diseases]

Infectious diseases have a high incidence in the population, causing a major impact on global health. In vitro culture of microorganisms is the first technique applied for infection diagnosis which is laborious and time consuming. In recent decades, efforts have been focused on the applicability of "Omics" sciences, highlighting the progress provided by proteomic techniques in the field of infectious diseases. This review describes the management, processing and analysis of biological samples for proteomic research.

Identification of putative virulence-associated genes among Haemophilus parasuis strains and the virulence difference of different serovars

This study was aimed at determining virulence-associated genes among Haemophilus parasuis (H. parasuis) strains, and supplying for the Kielstein-Rapp-Gabrielson serotyping scheme. The subtractive fragments, obtained through suppression subtractive hybridization and reverse Southern blot hybridization, were found to encode genes representative of 7 different functions. PCR was used to investigate the distribution of these fragments in H. parasuis strains isolated from different infection sites in pigs. Mice challenge was then used to analyze the correlationship between subtractive fragments, infection sites and bacterial virulence. Eight weeks old female BALB/c mice (10 mice/group) were inoculated intraperitoneally with 3.0 × 10(9) CFU suspension (0.5 ml/mouse) of H. parasuis strains in PBS. Results indicated that H. parasuis possessed varied virulence even among the same serovar strains. Transcription units hsdR, hsdS, gpT and ompP2, identified from the subtractive fragments, were uniformly expressed in highly virulent strains, while absent in weakly virulent strains, and demonstrated variable degrees of expression in moderately virulent strains. Moreover, H. parasuis strains, isolated from pericardium and heart blood, were all highly virulent strains, while from nasal cavity and joint were moderately or weakly virulent strains. This study indicated that fragments hsdR, hsdS, gpT and ompP2 were associated with the virulence of H. parasuis. The virulence of H. parasuis strains isolated from different infection sites was different. The current research provides a new reference for determining bacterial virulence in different H. parasuis strains.

Fifteen novel immunoreactive proteins of Chinese virulent Haemophilus parasuis serotype 5 verified by an immunoproteomic assay

Haemophilus parasuis (H. parasuis) is associated with meningitis, polyserositis, polyarthritis and bacterial pneumonia. At present, its prevention and control is difficult because of the lack of suitable subunit vaccines. Nowadays, high-throughput methods, immunoproteomics, are available to screen for more vaccine candidates. A protein extraction method for H. parasuis and two-dimensional electrophoresis (2-DE) were optimized to provide high-resolution profiles covering pH 3 to 10. Twenty immunoreactive spots were excised from gels after strict comparison between 2-DE Western blot membranes and the relevant gels. Matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) and MALDI-TOF-TOF-MS successfully identified 16 different proteins. Fifteen of them were reported as immunoreactive proteins in H. parasuis for the first time. In addition, recombinant HP5-7 (ABC transporter, periplasmic-binding protein) showed immunoreactivity both with hyperimmune rabbit serum and convalescent swine serum. Four recombinants of the 14 successfully expressed genes showed immunoreactivity with hyperimmune rabbit serum.

Virulence and draft genome sequence overview of multiple strains of the swine pathogen Haemophilus parasuis

Haemophilus parasuis is the cause of Glässer's disease in swine, which is characterized by systemic infection resulting in polyserositis, meningitis, and arthritis. Investigation of this animal disease is complicated by the enormous differences in the severity of disease caused by H. parasuis strains, ranging from lethal systemic disease to subclinical carriage. To identify differences in genotype that could account for virulence phenotypes, we established the virulence of, and performed whole genome sequence analysis on, 11 H. parasuis strains. Virulence was assessed by evaluating morbidity and mortality following intranasal challenge of Caesarean-derived, colostrum-deprived (CDCD) pigs. Genomic DNA from strains Nagasaki (serotype 5), 12939 (serotype 1), SW140 (serotype 2), 29755 (serotype 5), MN-H (serotype 13), 84-15995 (serotype 15), SW114 (serotype 3), H465 (serotype 11), D74 (serotype 9), and 174 (serotype 7) was used to generate Illumina paired-end libraries for genomic sequencing and de novo assembly. H. parasuis strains Nagasaki, 12939, SH0165 (serotype 5), SW140, 29755, and MN-H exhibited a high level of virulence. Despite minor differences in expression of disease among these groups, all pigs challenged with these strains developed clinical signs consistent with Glässer's disease between 1–7 days post-challenge. H. parasuis strains 84-15995 and SW114 were moderately virulent, in that approximately half of the pigs infected with each developed Glässer's disease. H. parasuis strains H465, D74, and 174 were minimally virulent or avirulent in the CDCD pig model. Comparative genomic analysis among strains identified several noteworthy differences in coding regions. These coding regions include predicted outer membrane, metabolism, and pilin or adhesin related genes, some of which likely contributed to the differences in virulence and systemic disease observed following challenge. These data will be useful for identifying H. parasuis virulence factors and vaccine targets.

Generation of a Tn5 transposon library in Haemophilus parasuis and analysis by transposon-directed insertion-site sequencing (TraDIS)

Haemophilus parasuis is an important respiratory tract pathogen of swine and the etiological agent of Glässer's disease. The molecular pathogenesis of H. parasuis is not well studied, mainly due to the lack of efficient tools for genetic manipulation of this bacterium. In this study we describe a Tn5-based random mutagenesis method for use in H. parasuis. A novel chloramphenicol-resistant Tn5 transposome was electroporated into the virulent H. parasuis serovar 5 strain 29755. High transposition efficiency of Tn5, up to 10(4) transformants/μg of transposon DNA, was obtained by modification of the Tn5 DNA in the H. parasuis strain HS071 and establishment of optimal electrotransformation conditions, and a library of approximately 10,500 mutants was constructed. Analysis of the library using transposon-directed insertion-site sequencing (TraDIS) revealed that the insertion of Tn5 was evenly distributed throughout the genome. 10,001 individual mutants were identified, with 1561 genes being disrupted (69.4% of the genome). This newly-developed, efficient mutagenesis approach will be a powerful tool for genetic manipulation of H. parasuis in order to study its physiology and pathogenesis.

Cross-protective efficacy of recombinant transferrin-binding protein A of Haemophilus parasuis in guinea pigs

The causative agent of Glasser's disease in swine is Haemophilus parasuis. Commercial bacterins are widely used for protection of the swine population. However, cross protection is limited because H. parasuis has more than 15 serovars. Transferrin-binding protein A has shown potential as a broad-spectrum vaccine candidate against homologous and heterologous strains. Here we amplified the full-length tbpA gene from an H. parasuis serovar 13 isolate and cloned it into a pET-SUMO expression vector. We then expressed and purified the TbpA protein by Ni affinity chromatography. First, the immunogenicity and protective efficacy of the protein were evaluated in guinea pigs by two subcutaneous immunizations with different doses of Montanide IMS 206 VG adjuvant. The immunized guinea pigs were, respectively, challenged on week 3 after a booster immunization with homologous strain LJ3 (serovar 13) and heterologous strain FX1 (serovar 4), and vaccine-inoculated groups were compared with nonvaccinated controls. All immunized groups showed serum antibody titers higher than those of negative-control groups. Furthermore, the cytokine and chemokine levels were evaluated at the transcriptional level by the real-time PCR analysis of six cytokines and chemokines. Gamma interferon and interleukin-5 in groups immunized with 100 μg were elevated more than 15-fold over those in negative-control groups. The protection rates were 80 and 60% after a challenge with strains LJ3 and FX1, respectively, in the groups vaccinated with 100 μg of recombinant TbpA protein. Subsequently, the data showed that guinea pigs immunized with a single dose (100 μg) were protected at levels of 80, 80, and 60% against LJ3, FX1, and another heterologous strain, SZ (serovar 14), respectively. The results indicate for the first time that TbpA protein cross protects guinea pigs against serovars 13, 4, and 14 of H. parasuis. Taken together, these results suggest that the recombinant TbpA protein is a promising vaccine candidate that needs to be confirmed in a swine population.

Protection of piglets by a Haemophilus parasuis ghost vaccine against homologous challenge

Commercial bacterins for Glässer's disease are widely used for the prevention of this disease caused by Haemophilus parasuis; however, the protective efficacy varies depending on the strain and serovar. Bacterial ghosts (BGs) are empty bacterial envelopes that, unlike classic bacterins, suffer no denaturing steps during their production. These properties may lead to superior protection. In this study, a BG vaccine generated from the Haemophilus parasuis serovar 5 reference strain Nagasaki was prepared and used to inoculate piglets. The efficacy of the BG vaccine was evaluated by clinical, bacteriological, serological, and postmortem examinations. Inactivated bacterin (IB) and a placebo control (PC) were compared with the BG vaccine in this study. The results showed that the piglets inoculated with the BG vaccine developed higher antibody activity and higher gamma interferon and interleukin 4 levels than those vaccinated with IB or those in the PC group after primary and secondary exposure to the antigens and challenge. CD4(+) T lymphocyte levels were observed to increase following secondary immunization more in the BG-vaccinated group than in the IB (P < 0.05) and PC (P < 0.05) groups. CD8(+) T lymphocyte levels increased dramatically in all three groups after challenge, and the differences between groups were all significant (P < 0.05). There were fewer tissue lesions and lower bacterial loads in the tissue homogenates in the BG group after challenge. The results suggest that higher CD4(+) T lymphocyte levels and both CD4(+) major histocompatibility complex class II-restricted Th1-type and Th2-type immune responses in the BG group are relevant for protection.

The live attenuated Actinobacillus pleuropneumoniae triple-deletion mutant ΔapxIC ΔapxIIC ΔapxIV-ORF1 strain, SLW05, Immunizes pigs against lethal challenge with Haemophilus parasuis

Haemophilus parasuis and Actinobacillus pleuropneumoniae both belong to the family Pasteurellaceae and are major respiratory pathogens that cause large economic losses in the pig industry worldwide. We previously constructed an attenuated A. pleuropneumoniae serovar 1 live vaccine prototype, SLW05 (ΔapxIC ΔapxIIC ΔapxIV-ORF1), which is able to produce nontoxic but immunogenic ApxIA, ApxIIA, and ApxIVA. This triple-deletion mutant strain was shown to elicit protective immunity against virulent A. pleuropneumoniae. In the present study, we investigated whether immunization with SLW05 could also protect against lethal challenge with virulent H. parasuis SH0165 (serovar 5) or MD0322 (serovar 4). The SLW05 strain was found to elicit a strong humoral antibody response in pigs and to confer significant protection against challenge with a lethal dose of H. parasuis SH0165 or MD0322. IgG subtype analysis revealed that SLW05 induces a bias toward a Th1-type immune response and stimulates interleukin 2 (IL-2) and gamma interferon (IFN-γ) production. Moreover, antisera from SLW05-vaccinated pigs efficiently inhibited both A. pleuropneumoniae and H. parasuis growth in a whole-blood assay. This is the first report that a live attenuated A. pleuropneumoniae vaccine with SLW05 can protect against lethal H. parasuis infection, which provides a novel approach for developing an attenuated H. parasuis vaccine.

Immunogenicity and protective efficacy of recombinant Haemophilus parasuis SH0165 putative outer membrane proteins

Haemophilus parasuis (H. parasuis), the causative agent of swine polyserositis, polyarthritis, and meningitis, is one of the most important bacterial diseases of pigs worldwide. Little vaccines currently exist that have a significant effect on infections with all pathogenic serovars of H. parasuis. H. parasuis putative outer membrane proteins (OMPs) are potentially essential components of more effective vaccines. Recently, the genomic sequence of H. parasuis serovar 5 strain SH0165 was completed in our laboratory, which allow us to target OMPs for the development of recombinant vaccines. In this study, we focused on 10 putative OMPs and all the putative OMPs were cloned, expressed and purified as HIS fusion proteins. Primary screening for immunoprotective potential was performed in mice challenged with an LD50 challenge. Out of these 10 OMPs three fusion proteins rGAPDH, rOapA, and rHPS-0675 were found to be protective in a mouse model of H. parasuis infection. We further evaluated the immune responses and protective efficacy of rGAPDH, rOapA, and rHPS-0675 in pig models. All three proteins elicited humoral antibody responses and conferred different levels of protection against challenge with a lethal dose of H. parasuis SH0165 in pig models. In addition, the antisera against the three individual proteins and the synergistic protein efficiently inhibited bacterial growth in a whole blood assay. The data demonstrated that the three proteins showed high value individually and the combination of rGAPDH, rOapA, and rHPS-0675 offered the best protection. Our results indicate that rGAPDH, rOapA, and rHPS-0675 induced protection against H. parasuis SH0165 infection, which may facilitate the development of a multi-component vaccine.

Construction and immune effect of Haemophilus parasuis DNA vaccine encoding glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in mice

Haemophilus parasuis, the causative agent of swine polyserositis, polyarthritis, and meningitis, is one of the most important bacterial diseases of pigs worldwide. The development of a vaccine against H. parasuis has been impeded due to the lack of induction of reliable cross-serotype protection. In this study the gapA gene that encodes glyceraldehyde-3-phosphate dehydrogenase (GAPDH) was shown to be present and highly conserved in various serotypes of H. parasuis and we constructed a novel DNA vaccine encoding GAPDH (pCgap) to evaluate the immune response and protective efficacy against infection with H. parasuis MD0322 serovar 4 or SH0165 serovar 5 in mice. A significant antibody response against GAPDH was generated following pCgap intramuscular immunization; moreover, antibodies to the pCgap DNA vaccine were bactericidal, suggesting that it was expressed in vivo. The gapA transcript was detected in muscle, liver, spleen, and kidney of the mice seven days post-vaccination. The IgG subclass (IgG1 and IgG2a) analysis indicated that the DNA vaccine induced both Th1 and Th2 immune responses, but the IgG1 response was greater than the IgG2a response. Moreover, the groups vaccinated with the pCgap vaccine exhibited 83.3% and 50% protective efficacy against the H. parasuis MD0322 serovar 4 or SH0165 serovar 5 challenges, respectively. The pCgap DNA vaccine provided significantly greater protective efficacy compared to the negative control groups or blank control groups (P<0.05 for both). Taken together, these findings indicate that the pCgap DNA vaccine provides a novel strategy against infection of H. parasuis and offer insight concerning the underlying immune mechanisms of a bacterial DNA vaccine.

New insights in cellular immune response in colostrum-deprived pigs after immunization with subunit and commercial vaccines against Glässer's disease

Four groups of colostrum-deprived pigs were immunized with Porcilis Glässer® (PG) or with subunit vaccines developed by us (rTbpA, NPAPT(M) or NPAPT(Cp)) against Glässer's disease, and they were challenged with 3×10(8)CFU of Haemophilus parasuis. A strong reduction in CD3(+)γδTCR(+) cells was seen in non-immunized control and scarcely protected (rTbpA) groups, suggesting that these cells could represent a target of H. parasuis infection. A significant increase in CD172α(+)CD163(+) cells was detected in all groups but PG, while a reduction in SLAIIDR(+) molecules expression was observed after challenge in control animals. Significant increases in CD3ε(+)CD8α(+)CD8β(+) and B cells were detected respectively in control and NPAPT groups, and in scarcely (rTbpA) and well-protected (NPAPT(M) and NPAPT(Cp)) groups. Finally, a greater response in CD4(+)CD8α(-) cells was observed in NPAPT(Cp) compared to NPAPT(M) and PG groups. These results state the potential of NPAPT antigen for developing effective vaccines against Glässer's disease.

Identification of novel immunogenic proteins in Mycoplasma capricolum subsp. Capripneumoniae strain M1601

The purpose of this study was to obtain immunogenic proteins and potential proteins of interest that were isolated from Mycoplasma capricolum subsp. capripneumoniae (Mccp) by MALDI-TOF mass spectrometry. One-dimensional SDS-PAGE and two-dimensional gel electrophoresis of whole cell preparation were conducted, and membrane proteome maps were prepared by immunoblotting. One-dimensional SDS-PAGE identified three immunogenic proteins with molecular masses in the range 29-97.2 kDa, two of which were in the membrane protein fraction. After two-dimensional gel electrophoresis, 20 highly immunogenic proteins were identified in the whole cell protein preparation while 9 immunogenic proteins were identified in the membrane protein fraction. This indicated that membrane proteins were the principle immunogenic proteins in Mccp. These proteins may have potential for the development of improved diagnostic tests and possible vaccines.

Identification of Streptococcus equi ssp. zooepidemicus surface associated proteins by enzymatic shaving

Streptococcus equi ssp. zooepidemicus (Streptococcus zooepidemicus, SEZ) is responsible for a wide variety of infections in many species. Attempts to control the infection caused by this agent are hampered by a lack of effective vaccines and useful diagnostic kits. Surface proteins of bacterial species are usually involved in interaction with host and hopefully act as biomarkers for serodiagnosis and subunit vaccine components. In this study, the surface proteins of SEZ C55138 strain were systematically identified by surface shaving with trypsin and a total of 20 surface associated proteins were found. Further analysis of five selected novel proteins (SzM, FBP, SAP, CSP and 5'-Nu) revealed that they all expressed in vivo and their recombinant derived proteins could be reactive with convalescent sera. These identified immunogenic surface proteins have potential as SEZ vaccine candidates and diagnostic markers.