DNA vaccination based on pyolysin co-immunized with IL-1β enhances host antibacterial immunity against Trueperella pyogenes infection

Co-immunization with DNA vaccines encoding yidR and IL-17 augments host immune response against Klebsiella pneumoniae infection in mouse model

Klebsiella pneumoniae is an important gram-negative bacterium that causes severe respiratory and healthcare-associated infections. Although antibiotic therapy is applied to treat severe infections caused by K. pneumoniae, drug-resistant isolates pose a huge challenge to clinical practices owing to adverse reactions and the mismanagement of antibiotics. Several studies have attempted to develop vaccines against K. pneumoniae, but there are no licensed vaccines available for the control of K. pneumoniae infection. In the current study, we constructed a novel DNA vaccine, pVAX1-YidR, which encodes a highly conserved virulence factor YidR and a recombinant expression plasmid pVAX1-IL-17 encoding Interleukin-17 (IL-17) as a molecular adjuvant. Adaptive immune responses were assessed in immunized mice to compare the immunogenicity of the different vaccine schemes. The results showed that the targeted antigen gene was expressed in HEK293T cells using an immunofluorescence assay. Mice immunized with pVAX1-YidR elicited a high level of antibodies, induced strong cellular immune responses, and protected mice from K. pneumoniae challenge. Notably, co-immunization with pVAX1-YidR and pVAX1-IL-17 significantly augmented host adaptive immune responses and provided better protection against K. pneumoniae infections in vaccinated mice. Our study demonstrates that combined DNA vaccines and molecular adjuvants is a promising strategy to develop efficacious antibacterial vaccines against K. pneumoniae infections.

Molecular Characterization of Resistance and Virulence Factors of Trueperella pyogenes Isolated from Clinical Bovine Mastitis Cases in China

Purpose

The present study was designed to investigate the resistance determinants and virulence factors of 45 Trueperella pyogenes isolates from clinical bovine mastitis in Hexi Corridor of Gansu, China.

Methods

Minimum inhibitory concentrations (MICs) was tested by E-test method. Gene of antimicrobial resistance, virulence integrase and integron gene cassettes were determined by PCR and DNA sequencing.

Results

The T. pyogenes isolates exhibited high resistance to streptomycin (88.9%) and tetracycline (64.4%), followed by erythromycin (15.6%) and gentamicin (13.3%). Resistance to streptomycin was most commonly encoded by aadA9 (88.9%); and to tetracycline, by tetW (64.4%). Importantly, all streptomycin-resistant isolates carried aadA9 alone or in combination with aadA1, aadA11 and strA-strB. Similarly, all tetracycline-resistant isolates harbored tetW alone or in combination with tetA33. Meanwhile, ermX was detected in 13.3% isolates, only one erythromycin-resistant isolate was not identified for this gene. Moreover, all T. pyogenes isolates carried class 1 integrons, and 17.8% of them contained gene cassettes, including arrays aadA1-aadB (4.4%), aad A24-dfrA1-ORF1 (2.2%) and aadA1 (2.2%). Furthermore, all tested isolates harbored virulent genes plo and fimA, followed by fimC (88.9%), fimE (86.6%) nanP (75.6%), nanH (40.0%), cbpA (35.6%) and fimG (6.7%).

Conclusion

To our knowledge, this is the first report of integron gene cassettes of T. pyogenes isolates from bovine mastitis cases in China. These findings are useful for developing the prevention and the virulence factors of T. pyogenes could be promising candidates for vaccine antigens for bovine mastitis caused by T. pyogenes in China.

Preparation and evaluation of recombinant pyolysin, fimbriae E and HtaA based protein vaccines against Trueperella pyogenes

Trueperella pyogenes (T. pyogenes) could cause zoonotic disease in various mammals, resulting in significant economic losses. Due to the lack of effective vaccine and the emergence of bacterial resistance, there is a big need for new and improved vaccines. In this study, the non-hemolytic pyolysin mutant (PLOW497F), fimbriae E (FimE) and a truncated cell wall protein (HtaA-2) were selected to generate single or multivalent protein vaccines and their efficacies against lethal T. pyogenes challenge were evaluated in a mouse model. The results showed that the levels of specific antibody were significantly higher than the PBS control group after the booster vaccination. Compared to PBS treated mice, vaccinated mice had upregulated expressions of the inflammatory cytokine genes after the first vaccination. There was a downward trend thereafter, but return to the similar or even higher levels after challenge. Furthermore, co-immunization with rFimE or rHtaA-2 could significantly enhance the anti-hemolysis antibodies induced by rPLOW497F. The supplement of rHtaA-2 induced higher agglutinating antibodies compared with single administration with rPLOW497F or rFimE. Apart from these, the pathological lesions of lung were alleviated in rHtaA-2, rPLOW497F or their combinations immunized mice. Notably, immunization with rPLOW497F, rHtaA-2, combinations of rPLOW497F and rHtaA-2 or rHtaA-2 and rFimE completely protected mice from challenge, whereas the PBS immunized mice could not survive past 1 day post challenge. Thus, PLOW497F and HtaA-2 might be useful in developing efficient vaccines to prevent T. pyogenes infection.

Multi-omics-based characterization of the influences of Mycobacterium tuberculosis virulence factors EsxB and PPE68 on host cells

Mycobacterium tuberculosis, the ancient master of causing tuberculosis, is one of the most successful pathogens capable of persistently colonizing host lungs. The EsxB (CFP-10) of ESX-1 system and PPE68 of the PPE family contribute to the virulence of M. tuberculosis. However, the virulence potential and pathogenetic characteristics of these two proteins during M. tuberculosis infection remain unclear. In this study, two prokaryotic expression plasmids for EsxB or PPE68 of M. tuberculosis were constructed and the recombinant proteins His-EsxB or His-PPE68 were purified. The proteome and transcriptome of MH-S cells treated with His-EsxB or His-PPE68 were explored, followed by validating the expression of the identified differentially expressed genes (DEGs) using quantitative PCR. A total of 159/439 specific proteins or 633/1117 DEGs were obtained between control and His-EsxB or His-PPE68 treated groups in the MH-S proteomes and transcriptomes. Additionally, 37/60 signal pathways were predicted in the His-EsxB or His-PPE68 treated groups and "Cytokine-cytokine receptor interaction" was the most represented pathway. Furthermore, the expression of the DEGs (IL-1β, IL-6, and TNF-α) was significantly upregulated, suggesting that these DEGs contributed to the host response during EsxB or PPE68 treatment. These findings provide detailed information on developing an effective intervention strategy to control M. tuberculosis infection.

Comparative Genome Analysis of 19 Trueperella pyogenes Strains Originating from Different Animal Species Reveal a Genetically Diverse Open Pan-Genome

Trueperella pyogenes is a Gram-positive opportunistic pathogen that causes severe cases of mastitis, metritis, and pneumonia in a wide range of animals, resulting in significant economic losses. Although little is known about the virulence factors involved in the disease pathogenesis, a comprehensive comparative genome analysis of T. pyogenes genomes has not been performed till date. Hence, present investigation was carried out to characterize and compare 19 T. pyogenes genomes originating in different geographical origins including the draftgenome of the first Indian origin strain T. pyogenes Bu5. Additionally, candidate virulence determinants that could be crucial for their pathogenesis were also detected and analyzed by using various bioinformatics tools. The pan-genome calculations revealed an open pan-genome of T. pyogenes. In addition, an inventory of virulence related genes, 190 genomic islands, 31 prophage sequences, and 40 antibiotic resistance genes that could play a significant role in organism's pathogenicity were detected. The core-genome based phylogeny of T. pyogenes demonstrates a polyphyletic, host-associated group with a high degree of genomic diversity. The identified core-genome can be further used for screening of drug and vaccine targets. The investigation has provided unique insights into pan-genome, virulome, mobiliome, and resistome of T. pyogenes genomes and laid the foundation for future investigations.

Identification of Antigenic Properties of Acinetobacter baumannii Proteins as Novel Putative Vaccine Candidates Using Reverse Vaccinology Approach

Multidrug-resistant Acinetobacter baumannii (A. baumannii) infections are becoming more prevalent all over the world. As a cost-effective and preventative method, vaccination seems to be required against this bacterium. In the present study, subtractive proteomics along with reverse vaccinology approaches was used to predict suitable therapeutics against A. baumannii. Using the Vaxign online tool, we studied over 35 genomes of A. baumannii strains and chose outer membrane and secreted proteins of A. baumannii 1656-2 as possible vaccine candidates. Then, investigations were performed on the immunogenicity, antigenic characteristics, physicochemical properties, B-cell and MHC class I, and MHC class II molecules epitope densities of proteins. After optimizing the codon of the proteins, the pcDNA3.1( +) expression construct was designed and the immunogenicity, allergenicity, and physicochemical properties of the vaccine construct were predicted. Hcp and OmpC proteins were predicted as extracellular and outer membrane proteins, respectively. These proteins interact with 10 other proteins to form a network of protein interactions with virulence properties. Immunoassays of Hcp and OmpC proteins showed antigenicity of 0.88 and 0.79, respectively. These proteins have 5 structural cell epitope points and 5 linear B epitope points. They are also able to bind to different HLA alleles of MCH class I/class II as selected immunogenic proteins and designed non-allergenic structures with solubility of 0.650 and immunogenicity score of 0.91. The results of this "in silico" study indicate high specificity and the development of a significant humoral and cellular immune response. It can be concluded that the Hcp and OmpC dual vaccine construct is one of the promising candidates against A. baumannii. The findings of this "in silico" study show excellent specificity and the emergence of a substantial humoral and cellular immune response. This is a computer-based study that needs to be tested in vitro and in vivo to corroborate the conclusions of the vaccine design procedures.

Heterologous Prime-Boost Immunization with DNA Vaccine and Modified Recombinant Proteins Enhances Immune Response against Trueperella pyogenes in Mice

Trueperella pyogenes (T. pyogenes) is a crucial opportunistic pathogen normally causing mastitis, abscesses and pneumonia in economically important ruminants. Although only one commercial vaccine of T. pyogenes is currently obtainable, its immunoprotective effect is limited. Pyolysin (PLO) is the most predominant virulence factor highly expressed in T. pyogenes and is an excellent target for the development of novel vaccines against T. pyogenes. In this study, we designed a heterologous prime-boost vaccination scheme combining a DNA vaccine pVAX1-PLO and a subunit vaccine His-PLO to maximize host responses in mice. Humoral and cellular immune responses and protective effects were evaluated in mice to compare the immunogenicity induced by different immunization schemes. Compared to the PBS-control group, in vivo immunization results showed that better immune responses of mice immunized with the pVAX1-PLO plasmids and His-PLO proteins were induced. The residual bacterial burdens from the liver and peritoneal fluid were remarkably decreased in the immunized mice compared with the PBS group. Notably, the heterologous prime-boost vaccination groups significantly enhanced host humoral and cellular immune responses and protected mice from different virulent T. pyogenes strains infection. Conclusively, this study provides a favorable strategy for the further development of next-generation vaccines against T. pyogenes infections.

STING and TLR7/8 agonists-based nanovaccines for synergistic antitumor immune activation

Immunostimulatory therapies based on pattern recognition receptors (PRRs) have emerged as an effective approach in the fight against cancer, with the ability to recruit tumor-specific lymphocytes in a low-immunogenicity tumor environment. The agonist cyclic dinucleotides (CDNs) of the stimulator of interferon gene (STING) are a group of very promising anticancer molecules that increase tumor immunogenicity by activating innate immunity. However, the tumor immune efficacy of CDNs is limited by several factors, including relatively narrow cytokine production, inefficient delivery to STING, and rapid clearance. In addition, a single adjuvant molecule is unable to elicit a broad cytokine response and thus cannot further amplify the anticancer effect. To address this problem, two or more agonist molecules are often used together to synergistically enhance immune efficacy. In this work, we found that a combination of the STING agonist CDG^SF and the Toll-like receptor 7/8 (TLR7/8) agonist 522 produced a broader cytokine response. Subsequently, we developed multicomponent nanovaccines (MCNVs) consisting of a PC7A polymer as a nanocarrier encapsulating the antigen OVA and adjuvant molecules. These MCNVs activate bone marrow-derived dendritic cells (BMDCs) to produce multiple proinflammatory factors that promote antigen cross-presentation to stimulate specific antitumor T-cell responses. In in vivo experiments, we observed that MCNVs triggered a strong T-cell response in tumor-infiltrating lymphocytes, resulting in significant tumor regression and, notably, a 100% survival rate in mice through 25 days without other partnering therapies. These data suggest that our nanovaccines have great potential to advance cancer immunotherapy with increased durability and potency.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (synthesis of CDG^SF, 522, PC7A and OVA; preparation of MCNVs; representative gating strategies for flow cytometry) is available in the online version of this article at 10.1007/s12274-022-4282-x.

Search of Potential Vaccine Candidates against Trueperella pyogenes Infections through Proteomic and Bioinformatic Analysis

Trueperella pyogenes is an opportunistic pathogen, responsible for important infections in pigs and significant economic losses in swine production. To date, there are no available commercial vaccines to control diseases caused by this bacterium. In this work, we performed a comparative proteomic analysis of 15 T. pyogenes clinical isolates, by “shaving” live cells, followed by LC-MS/MS, aiming at the identification of the whole set of surface proteins (i.e., the “pan-surfome”) as a source of antigens to be tested in further studies as putative vaccine candidates, or used in diagnostic tools. A total of 140 surface proteins were detected, comprising 25 cell wall proteins, 10 secreted proteins, 23 lipoproteins and 82 membrane proteins. After describing the “pan-surfome”, the identified proteins were ranked in three different groups based on the following criteria: to be (i) surface-exposed, (ii) highly conserved and (iii) widely distributed among different isolates. Two cell wall proteins, three lipoproteins, four secreted and seven membrane proteins were identified in more than 70% of the studied strains, were highly expressed and highly conserved. These proteins are potential candidates, alone or in combination, to obtain effective vaccines against T. pyogenes or to be used in the diagnosis of this pathogen.

Evaluation of the Potency of Two Pyolysin-Derived Recombinant Proteins as Vaccine Candidates of Trueperella Pyogenes in a Mouse Model: Pyolysin Oligomerization and Structural Change Affect the Efficacy of Pyolysin-Based Vaccines

Trueperella pyogenes (T. pyogenes) is an important opportunistic pathogen in livestock and wild animals. However, only one commercial T. pyogenes vaccine is currently available, and its immunoprotective effect is not ideal. Pyolysin (PLO) is one of the important virulence factors expressed by T. pyogenes and one of the targets for the development of new T. pyogenes vaccines. In this study, we constructed two recombinant antigens, tPLOA1 (contains amino acids 1–110 and domain 4 of the PLO molecule) and tPLOA2 (contains amino acids 190–296 and domain 4 of the PLO molecule). Vaccines were prepared by mixing the two recombinant antigens with incomplete Freund’s adjuvant or sheep red blood cell membrane and provided partial immune protection to immunized mice against the lethal challenge of T. pyogenes. Analysis of the PLO-specific IgG levels of immunized mice indicated that the antibody-inducing potency and immunoprotective efficacy of PLO-based vaccines are affected by the oligomerization and structural changes of PLO after binding to a cholesterol-containing membrane. In addition, the titer of anti-hemolysis antibodies is not a suitable indicator of the immunoprotective effect of these vaccines in PLO-based vaccine-immunized animals. The results provide new insights into the development of T. pyogenes vaccines.

MTOR involved in bacterial elimination against Trueperella pyogenes infection based on mice model by transcriptome and biochemical analysis

Trueperella pyogenes is an importantly opportunistic and commensal pathogen that causes suppurative lesions of most economically important livestock. To understand the molecular mechanism underlying the infection by T. pyogenes, we carried out a large-scale transcriptome sequencing of mice livers intraperitoneally infected with T. pyogenes using RNA-sequencing. A total of 47 G clean bases were obtained and 136 differentially expressed genes were detected between the control and the infection groups in the liver transcriptomes. Additionally, we found that the expression of a key autophagy regulator, mTOR (mechanistic target of rapamycin) was significantly up-regulated in the infection groups. Mechanistically, T. pyogenes infection induced the expression of mTOR and subsequently inhibited the autophagy of host cell. Blocking autophagy with inhibitor 3-methyladenine (3-MA) or silencing autophagy-related gene 7 (Atg7) reduced the effect of bacterial elimination. Interestingly, inhibition of mTOR induced autophagy and reduced T. pyogenes viability in RAW264.7 murine macrophages. The silencing mTOR regulated oxidation and cytokines (interleukin-1β, IL-6 and tumor necrosis factro-α) against T. pyogenes in macrophages and significantly protected mice from T. pyogenes challenge. These findings indicate that mTOR is a novel functional regulator in autophagy-mediated T. pyogenes elimination and will be useful to further knowledge on the development of effective therapeutic strategy to control T. pyogenes-related diseases.

Comparative Genomics Reveals the Genetic Mechanisms of Musk Secretion and Adaptive Immunity in Chinese Forest Musk Deer

The Chinese forest musk deer (Moschus berezovskii; FMD) is an artiodactyl mammal and is both economically valuable and highly endangered. To investigate the genetic mechanisms of musk secretion and adaptive immunity in FMD, we compared its genome to nine other artiodactyl genomes. Comparative genomics demonstrated that eight positively selected genes (PSGs) in FMD were annotated in three KEGG pathways that were related to metabolic and synthetic activity of musk, similar to previous transcriptome studies. Functional enrichment analysis indicated that many PSGs were involved in the regulation of immune system processes, implying important reorganization of the immune system in FMD. FMD-specific missense mutations were found in two PSGs (MHC class II antigen DRA and ADA) that were classified as deleterious by PolyPhen-2, possibly contributing to immune adaptation to infectious diseases. Functional assessment showed that the FMD-specific mutation enhanced the ADA activity, which was likely to strengthen the immune defense against pathogenic invasion. Single nucleotide polymorphism-based inference showed the recent demographic trajectory for FMD. Our data and findings provide valuable genomic resources not only for studying the genetic mechanisms of musk secretion and adaptive immunity, but also for facilitating more effective management of the captive breeding programs for this endangered species.

Pathogenicity and Virulence of Trueperella pyogenes: A Review

Bacteria from the species Trueperella pyogenes are a part of the biota of skin and mucous membranes of the upper respiratory, gastrointestinal, or urogenital tracts of animals, but also, opportunistic pathogens. T. pyogenes causes a variety of purulent infections, such as metritis, mastitis, pneumonia, and abscesses, which, in livestock breeding, generate significant economic losses. Although this species has been known for a long time, many questions concerning the mechanisms of infection pathogenesis, as well as reservoirs and routes of transmission of bacteria, remain poorly understood. Pyolysin is a major known virulence factor of T. pyogenes that belongs to the family of cholesterol-dependent cytolysins. Its cytolytic activity is associated with transmembrane pore formation. Other putative virulence factors, including neuraminidases, extracellular matrix-binding proteins, fimbriae, and biofilm formation ability, contribute to the adhesion and colonization of the host tissues. However, data about the pathogen–host interactions that may be involved in the development of T. pyogenes infection are still limited. The aim of this review is to present the current knowledge about the pathogenic potential and virulence of T. pyogenes.

Electroporation-Mediated Immunization of a Candidate DNA Vaccine Expressing Dengue Virus Serotype 4 prM-E Antigen Confers Long-Term Protection in Mice

Dengue fever, caused by dengue viruses (DENVs), is a widespread mosquito-borne zoonotic disease; however, there is no available anti-dengue vaccine for worldwide use. In the current study, a DNA vaccine candidate (pV-D4ME) expressing prM-E protein of DENV serotype 4 (DENV-4) was constructed, and its immunogenicity and protection were evaluated in immunocompetent BALB/c mice. The pV-D4ME candidate vaccine induced effective humoral and cellular immunity of mice against DENV-4 in vivo when administered both at 50 μg and 5 μg through electroporation. Two weeks after receiving three immunizations, both doses of pV-D4ME DNA were shown to confer effective protection against lethal DENV-4 challenge. Notably, at 6 months after the three immunizations, 50 μg, but not 5 μg, of pV-D4ME could provide stable protection (100% survival rate) against DENV-4 lethal challenge without any obvious clinical signs. These results suggest that immunization with 50 μg pV-D4ME through electroporation could confer effective and long-term protection against DENV-4, offering a promising approach for development of a novel DNA vaccine against DENVs.

Acetalated Dextran Microparticles for Codelivery of STING and TLR7/8 Agonists

Vaccines are the most effective tool for preventing infectious diseases; however, subunit vaccines, considered the safest type, suffer from poor immunogenicity and require adjuvants to create a strong and sustained immune response. As adjuvants, pathogen-associated molecular patterns (PAMPs) offer potent immunostimulatory properties and defined mechanisms of action through their cognate pattern recognition receptors (PRRs). Their activity can be further enhanced through combining two or more PAMPs, particularly those that activate multiple immune signaling pathways. However, the cytosolic localization of many PRRs requires intracellular delivery of PAMPs for optimal biological activity, which is particularly true of the stimulator of interferon genes (STING) PRR. Using acetalated dextran (Ace-DEX) microparticles (MPs) encapsulating STING agonist 3'3'-cyclic GMP-AMP (cGAMP) combined with soluble PAMPS, we screened the effect of codelivery of adjuvants using primary mouse bone marrow derived dendritic cells (BMDCs). We identified that codelivery of cGAMP MPs and soluble Toll-like receptor 7/8 (TLR7/8) agonist resiquimod (R848) elicited the broadest cytokine response. cGAMP and R848 were then coencapsulated within Ace-DEX MPs via electrospray. Using the model antigen ovalbumin, we observed that Ace-DEX MPs coencapsulating cGAMP and R848 (cGAMP/R848 Ace-DEX MPs) induced antigen-specific cellular immunity, and a balanced Th1/Th2 humoral response that was greater than cGAMP Ace-DEX MPs alone and PAMPs delivered in separate MPs. These data indicate that polymeric Ace-DEX MPs loaded with STING and TLR7/8 agonists represent a potent cellular and humoral vaccine adjuvant.

Chitosan-DNA nanoparticles enhanced the immunogenicity of multivalent DNA vaccination on mice against Trueperella pyogenes infection

BACKGROUND

Trueperella pyogenes is a commensal and opportunistic pathogen that normally causes mastitis, liver abscesses and pneumonia of economically important livestock. To develop efficacious and potent vaccine against T. pyogenes, chimeric gene DNA vaccines were constructed and encapsulated in chitosan nanoparticles (pPCFN-CpG-CS-NPs).

RESULTS

The pPCFN-CpG-CS-NPs consists of the plo, cbpA, fimA, and nanH gene of T. pyogenes and CpG ODN1826. It was produced with good morphology, high stability, a mean diameter of 93.58 nm, and a zeta potential of + 5.27 mV. Additionally, chitosan encapsulation was confirmed to protect the DNA plasmid from DNase I digestion. The immunofluorescence assay indicated that the four-chimeric gene could synchronously express in HEK293T cells and maintain good bioactivity. Compared to the mice immunized with the control plasmid, in vivo immunization showed that mice immunized with the pPCFN-CpG-CS-NPs had better immune responses, and release of the plasmid DNA was prolonged. Importantly, immunization with pPCFN-CpG-CS-NPs could significantly protect mice from highly virulent T. pyogenes TP7 infection.

CONCLUSIONS

This study indicates that chitosan-DNA nanoparticles are potent immunization candidates against T. pyogenes infection and provides strategies for the further development of novel vaccines encapsulated in chitosan nanoparticles.

Blood transcriptomics of captive forest musk deer (Moschus berezovskii) and possible associations with the immune response to abscesses

Forest musk deer (Moschus berezovskii; FMD) are both economically valuable and highly endangered. A problem for FMD captive breeding programs has been the susceptibility of FMD to abscesses. To investigate the mechanisms of abscess development in FMD, the blood transcriptomes of three purulent and three healthy individuals were generated. A total of ~39.68 Gb bases were generated using Illumina HiSeq 4000 sequencing technology and 77,752 unigenes were identified after assembling. All the unigenes were annotated, with 63,531 (81.71%) mapping to at least one database. Based on these functional annotations, 45,798 coding sequences (CDS) were detected, along with 12,697 simple sequence repeats (SSRs) and 65,536 single nucleotide polymorphisms (SNPs). A total of 113 unigenes were found to be differentially expressed between healthy and purulent individuals. Functional annotation indicated that most of these differentially expressed genes were involved in the regulation of immune system processes, particularly those associated with parasitic and bacterial infection pathways.

Quorum-sensing molecules N-acyl homoserine lactones inhibit Trueperella pyogenes infection in mouse model

Trueperella pyogenes is a gram-positive opportunistic pathogen normally causes mastitis, liver abscesses and pneumonia of economically important livestock. It has been suggested that gram-negative bacteria can suppress the growth and virulence of T. pyogenes in vitro by using the quorum-sensing (QS) signal molecules and cause the transition of predominant species. However, whether these QS signals can be used as potential anti-virulence drugs against T. pyogenes infection is unclear. In this study, the in vivo inhibitory effect N-acyl homoserine lactones (AHLs) from Escherichia coli and Pseudomonas aeruginosa on T. pyogenes was tested by using mouse model. Mice were first peritoneally infected with T. pyogenes followed by intravenous injection of N-Octanoyl-DL-homoserine lactone (C8HSL) or N-(3-oxododecanoyl) homoserine-l-lactone (C12HSL). The results showed that C8HSL and C12HSL significantly reduced bacterial load and increased the survival rate of mice against T. pyogenes challenge. Additionally, the treatment of AHLs promoted the secretion of IL-1β, IL-6, IL-8 and TNF-α in mouse peritoneal fluid, and significantly decreased the expression levels of virulence genes of residual T. pyogenes. Importantly, murine macrophages rapidly phagocytosed bacteria when they were treated with AHLs compared to untreated cells. Collectively, our findings provide a major advance in understanding the inhibitory effect of AHLs in vivo and a promise for developing new clinical or veterinary treatments of T. pyogenes-related infection.

A combined Clostridium perfringens/Trueperella pyogenes inactivated vaccine induces complete immunoprotection in a mouse model

Clostridium perfringens (C. perfringens) and Trueperella pyogenes (T. pyogenes) are two bacterial pathogens frequently associated with wound infections and following lethal complications in livestock. However, prudent use of antimicrobial agents is highly required given the emergence of multidrug-resistant strains of both bacteria and need for food safety. In the current study, a combined vaccine, composed of inactivated C. perfringens and T. pyogenes, was prepared. The amount of formaldehyde being used to inactivate two bacteria was optimized to retain the immunogenicity of antigens. Three adjuvants were tested for their potency in improving specific immune responses against the candidate antigens. Then inactivated combined C. perfringens/T. pyogenes vaccine was prepared using inactive cultures of two organisms. The ratio of inactive cultures of two organisms for preparation of combined vaccine was optimized to gain effective protective immunity against the two pathogens. Results revealed that combined C. perfringens/T. pyogenes inactive vaccine can elicit high level of exotoxins and cell-associated antigen-specific antibodies and induce complete protection against C. perfringens and T. pyogenes infections in mice. The combined vaccine could be used as an alternative of antibiotics for prevention of C. perfringens and T. pyogenes infections in animals.