Current status of vaccine research, development, and challenges of vaccines for Mycoplasma gallisepticum

Transcriptomic analysis of the effects of tylosin on the protective immunity provided by the Mycoplasma gallisepticum vaccine Vaxsafe MG ts-304

The antimicrobial tylosin is commonly used to control mycoplasma infections, sometimes in combination with vaccination. However, the efficacy of a live mycoplasma vaccine, when combined with subsequent antimicrobial treatment, against the effects of subsequent infection with a virulent strain is unknown. This study employed differential gene expression analysis to evaluate the effects of tylosin on the protection provided by the live attenuated Vaxsafe MG ts-304 vaccine, which has been shown to be safe and to provide long-term protective immunity against infection with Mycoplasma gallisepticum. The transcriptional profiles of the tracheal mucosa revealed significantly enhanced inflammation, immune cell proliferation and adaptive immune responses in unvaccinated, untreated birds and in unvaccinated birds treated with tylosin 2 weeks after infection with virulent M. gallisepticum. These responses, indicative of the typical immune dysregulation caused by infection with M. gallisepticum, were less severe in the unvaccinated, tylosin-treated birds than in the unvaccinated, untreated birds. This was attributable to the effect of residual levels of tylosin in the tracheal mucosa on replication of virulent M. gallisepticum. These responses were not detected in vaccinated, tylosin-treated birds or in vaccinated, untreated birds after infection. The tracheal mucosal transcriptional profiles of these birds resembled those of unvaccinated, untreated, uninfected birds, suggesting a rapid and protective secondary immune response and effective vaccination. Overall, these results show that, although tylosin treatment reduced the duration of immunity, the initial protective immunity induced by Vaxsafe MG ts-304 lasted for at least 22 weeks after vaccination, even after the administration of tylosin for 16 weeks following vaccination.

Immune Evasion of Mycoplasma gallisepticum: An Overview

Mycoplasma gallisepticum is one of the smallest self-replicating organisms. It causes chronic respiratory disease, leading to significant economic losses in poultry industry. Following M. gallisepticum invasion, the pathogen can persist in the host owing to its immune evasion, resulting in long-term chronic infection. The strategies of immune evasion by mycoplasmas are very complex and recent research has unraveled these sophisticated mechanisms. The antigens of M. gallisepticum exhibit high-frequency changes in size and expression cycle, allowing them to evade the activation of the host humoral immune response. M. gallisepticum can invade non-phagocytic chicken cells and also regulate microRNAs to modulate cell proliferation, inflammation, and apoptosis in tracheal epithelial cells during the disease process. M. gallisepticum has been shown to transiently activate the inflammatory response and then inhibit it by suppressing key inflammatory mediators, avoiding being cleared. The regulation and activation of immune cells are important for host response against mycoplasma infection. However, M. gallisepticum has been shown to interfere with the functions of macrophages and lymphocytes, compromising their defense capabilities. In addition, the pathogen can cause immunological damage to organs by inducing an inflammatory response, cell apoptosis, and oxidative stress, leading to immunosuppression in the host. This review comprehensively summarizes these evasion tactics employed by M. gallisepticum, providing valuable insights into better prevention and control of mycoplasma infection.

Pharmacokinetic/pharmacodynamic integration of amphenmulin: a novel pleuromutilin derivative against Mycoplasma gallisepticum

Amphenmulin is a novel pleuromutilin derivative with great anti-mycoplasma potential. The present study evaluated the action characteristics of amphenmulin against Mycoplasma gallisepticum using pharmacokinetic/pharmacodynamic (PK/PD) modeling approaches. Following intravenous administration, amphenmulin exhibited an elimination half-life of 2.13 h and an apparent volume of distribution of 3.64 L/kg in healthy broiler chickens, demonstrating PK profiles of extensive distribution and rapid elimination. The minimum inhibitory concentration (MIC) of amphenmulin against M. gallisepticum was determined to be 0.0039 µg/mL using the broth microdilution method, and the analysis of the static time-kill curves through the sigmoid Emax model showed a highly correlated relationship (R ≥ 0.9649) between the kill rate and drug concentrations (1-64 MIC). A one-compartment open model with first-order elimination was implemented to simulate the in vivo anti-mycoplasma effect of amphenmulin, and it was found that bactericidal levels were reached with continuous administration for 3 days at doses exceeding 0.8 µg/mL. Furthermore, the area under the concentration-time curve divided by MIC (AUC/MIC) correlated well with the anti-mycoplasma effect of amphenmulin within 24 h after each administration, with a target value of 904.05 h for predicting a reduction of M. gallisepticum by 1 Log10CFU/mL. These investigations broadened the antibacterial spectrum of amphenmulin and revealed its characteristics of action against M. gallisepticum, providing a theoretical basis for further clinical development.IMPORTANCEMycoplasma has long been recognized as a significant pathogen causing global livestock production losses and public health concerns, and the use of antimicrobial agents is currently one of the mainstream strategies for its prevention and control. Amphenmulin is a promising candidate pleuromutilin derivative that was designed, synthesized, and screened by our laboratory in previous studies. Moreover, this study further confirms the excellent antibacterial activity of amphenmulin against Mycoplasma gallisepticum and reveals its action characteristics and model targets on M. gallisepticum by establishing an in vitro pharmacokinetic/pharmacodynamic synchronization model. These findings can further broaden the pharmacological theoretical basis of amphenmulin and serve as data support for its clinical development, which is of great significance for the discovery of new antimicrobial drugs and the control of bacterial diseases in humans and animals.

STAT5-mediated transcription of miR-33-5p in Mycoplasma gallisepticum-infected DF-1 cells

RESEARCH HIGHLIGHTS

MG-HS regulates the expression of transcription factor STAT5.Transcription factor STAT5 can target miR-33-5p promoter element.MG-influenced STAT5 regulates miR-33-5p and its target gene expression.

Quadrivalent hemagglutinin and adhesion expressed on Saccharomyces cerevisiae induce protective immunity against Mycoplasma gallisepticum infection and improve gut microbiota

Mycoplasma gallisepticum (MG) infection causes infectious respiratory diseases in poultry, causing economic losses to the poultry industry. Therefore, this study aims to develop a safe, convenient, and effective multivalent recombinant Saccharomyces cerevisiae vaccine candidate and to explore its potential for oral immunization as a subunit vaccine. Mycoplasma gallisepticum Cytadhesin (MGC) and variable lipoprotein and hemagglutinin (vlhA) are associated with the pathogenesis of MG. In this study, a quadrivalent recombinant Saccharomyces cerevisiae (ST1814G-MG) displaying on MGC2, MGC3, VLH5, and VLH3, proteins was innovatively constructed, and its protective efficiency was evaluated in birds. The results showed that oral immunization with ST1814G-MG stimulates specific antibodies in chickens, reshapes the composition of the gut microbiota, reduces the Mycoplasma loading and pulmonary disease injury in the lungs. In addition, we found that oral ST1814G-MG had better protection against MG infection than an inactivated vaccine, and co-administration with the inactivated vaccine was even more effective. The results suggest that ST1814G-MG is a potentially safer and effective agent for controlling MG infection.

A preliminary study of the immunogenic response of plant-derived multi-epitopic peptide vaccine candidate of Mycoplasma gallisepticum in chickens

Mycoplasma gallisepticum (MG) is responsible for chronic respiratory disease in avian species, characterized by symptoms like respiratory rales and coughing. Existing vaccines for MG have limited efficacy and require multiple doses. Certain MG cytoadherence proteins (GapA, CrmA, PlpA, and Hlp3) play a crucial role in the pathogen's respiratory tract colonization and infection. Plant-based proteins and therapeutics have gained attention due to their safety and efficiency. In this study, we designed a 21.4-kDa multi-epitope peptide vaccine (MEPV) using immunogenic segments from cytoadherence proteins. The MEPV's effectiveness was verified through computational simulations. We then cloned the MEPV, introduced it into the plant expression vector pSiM24-eGFP, and expressed it in Nicotiana benthamiana leaves. The plant-produced MEPV proved to be immunogenic when administered intramuscularly to chickens. It significantly boosted the production of immunoglobulin Y (IgY)-neutralizing antibodies against cytoadherence protein epitopes in immunized chickens compared to that in the control group. This preliminary investigation demonstrates that the plant-derived MEPV is effective in triggering an immune response in chickens. To establish an efficient poultry health management system and ensure the sustainability of the poultry industry, further research is needed to develop avian vaccines using plant biotechnology.

Inflammatory responses and barrier disruption in the trachea of chicks following Mycoplasma gallisepticum infection: a focus on the TNF-α-NF-κB/MLCK pathway

Mycoplasma gallisepticum (MG) can induce persistent inflammatory damage to the tracheal mucosa of poultry and cause chronic respiratory diseases in chickens. To further investigate the mechanism of MG-induced injury to the tracheal mucosa, we used chick embryo tracheal organ culture (TOC) as a model to study the invasion and reproduction of MG, the effect of MG on tracheal morphology, and the potential factors that promote MG tissue invasion. The results showed that MG infection significantly damaged the tracheal epithelial structure and weakened tracheal epithelial barrier function; MG also increased the occurrence of bacterial displacement, with a significant (p < 0.05) increase in the bacterial load of the infected TOCs at 5 and 7 days post-infection. In addition, MG significantly (p < 0.05) increased the expression levels of inflammatory cytokines, such as TNF-α, interleukin-1β (IL-1β), and IL-6, and activated the NF-κB signalling pathway, leading to increased nuclear translocation of NF-κB p65. Simultaneously, the map kinase pathway (MAPK) was activated. This activation might be associated with increased myosin light chain (MLC) phosphorylation, which could lead to actin-myosin contraction and disruption of tight junction (TJ) protein function, potentially compromising epithelial barrier integrity and further catalysing MG migration into tissues. Overall, our results contribute to a better understanding of the interaction between MG and the host, provide insight into the mechanisms of damage to the tracheal mucosa induced by MG infection, and provide new insights into the possible pathways involved in Mycoplasma gallisepticum infection in vivo.

Proteomic investigation and understanding on IgY purification and product development

An increasing demand for the development of immunoglobin Y (IgY) illustrates the necessity of the component analysis in the process of conduction and quality control. This study investigated the proteomic changes in crude IgY extracts and purified IgY products obtained by sequential polyethylene glycol precipitation (PEG) of egg yolks followed by human mycoplasma protein-based affinity chromatography compared with intact egg yolks. After confirming the extraction efficiency and purity by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, liquid chromatography tandem-mass spectrometry (LC-MS/MS) was performed with samples including fresh yolk, IgY extracted product and purified product. A total of 348 proteins were identified, with 36 proteins deleted and 209 newly detected proteins in the purified product compared to the intact egg yolk. The significantly decreased proteins mainly included phosvitin, albumin, and apolipoprotein B whereas the significantly increased proteins were mainly IgY-related proteins. GO analysis showed that the purified IgY product had ATPase activity and purine ribonucleoside triphosphate binding activity, and was mainly involved in purine and nucleic acid metabolism. This study will inevitably fasten the commercial application of IgY antibodies and is of greater significance for promotion, development and approval for new antibody derived drug products.

Detection of Mycoplasma gallisepticum, Isolation, and Determination of Tylosin Susceptibility of Isolates from Commercial Chickens

Mycoplasma gallisepticum (MG) is a contagious avian pathogen that causes financial losses to the poultry industry. Isolation of the pathogen is difficult and time-consuming, and therefore, far from a routine method. Serological testing methods to detect antibodies resistant to MG are widely used in routine diagnosis. Tylosin is a class of macrolide antibiotics tremendously administered in veterinary medicine for the treatment of mycoplasmosis and prophylaxis. This study aimed to detect MG by immunoassay testing, culture, and polymerase chain reaction (PCR) in commercial poultry farms and to investigate the tylosin susceptibility of the isolates. To verify the presence of antibodies resistant to MG, 750 blood samples were randomly collected from 38 broiler farms from 2019 to 2022 in Mazandaran and Golestan provinces, Iran, and rapid slide agglutination (RSA) assay was performed. Positive results were analyzed by the enzyme-linked immunosorbent assay (ELISA) for further investigation. Here, 920 swab samples were collected from 38 non-vaccinated commercial farms for culture, and PCR tests were performed for the isolated strains. The activities of tylosin were tested in vitro against these isolates using the broth microdilution method. The lowest antibiotic concentration that resulted in a color change was considered the minimum inhibitory concentration (MIC) value. Twenty-four (63.1%) farms were positive in the RSA test, and 21 (55.2%) farms were positive in the ELISA test. Nine (23.68%) of the farms grew on culture media, and 8 (21.05%) were detected as Gallisepticum species by PCR. The geometric mean of MIC for tylosin was 5.75 µg/ml, MIC50 was 4 µg/ml, and MIC90 was 8 µg/ml. The results indicated that commercial farms were infected with MG. Considering the ability of MG to spread and the probable use of the RSA test as a rapid and cheap method, it can be argued that ELISA and RSA serological tests can be used to find MG in poultry flocks, and the positive result should be confirmed by standard microbiological tests or PCR. It was also found that the isolated parts of MG changed their sensitivity to tylosin, indicating the need for routine testing to optimize treatment dose and efficiency.

Baicalin ameliorates Mycoplasma gallisepticum-induced inflammatory injury via inhibiting STIM1-regulated ceramide accumulation in DF-1 cells

Mycoplasma gallisepticum (MG) is dependent on its host for many nutrients due to the loss of many important metabolic pathways. Ceramide is a sphingolipid that regulates multiple cellular processes in eukaryotic cell. Several studies highlighted the crucial role of ceramide on the pathogenesis of various pathogens. This study aimed to determine whether ceramide plays a crucial role in the pathogenesis of MG. Based on an MG infection model in DF-1 cells, the results revealed that MG infection induced ceramide accumulation in DF-1 cells. Inhibiting the de novo synthesis of ceramide significantly inhibited MG proliferation and inflammatory injury caused by MG in DF-1 cells. Meanwhile, MG infection led to endoplasmic reticulum stress, and pharmacologic inhibition of endoplasmic reticulum stress prevented ceramide accumulation and MG proliferation in DF-1 cells, alleviating the inflammatory injury caused by MG. In addition, MG infection significantly promoted expression level of stromal interaction molecule 1 (STIM1), thus induced calcium overload and oxidative stress. Furthermore, inhibition of STIM1 expression partially restored calcium homeostasis and mitigated oxidative stress, thus alleviated endoplasmic reticulum stress. Importantly, the inflammatory injury caused by MG were partially ameliorated by baicalin treatment (20 µg/mL) through downregulating STIM1 expression. In summary, these results suggests that ceramide accumulation through the de novo pathway plays an important role to promote MG proliferation and baicalin can alleviate MG infection induced inflammatory injury via regulating STIM1-related oxidative stress, endoplasmic reticulum stress and ceramide accumulation in DF-1 cells.

Quercetin alleviates Mycoplasma gallisepticum-induced inflammatory damage and oxidative stress through inhibition of TLR2/MyD88/NF-κB pathway in vivo and in vitro

Chronic respiratory disease (CRD) caused by Mycoplasma gallisepticum (MG) in chickens leads to enormous economic damage to the poultry industry yearly. The active components and mechanism of action of the traditional herbal remedy Ephedra houttuynia powder (EHP), which had been approved for clinical treatment against MG infection in China, remain unknown. In this study, the active components of EHP against MG were screened using a network pharmacological method, additionally, we studied the mechanism of action of the screened results (quercetin (QUE)). The findings demonstrated that QUE was an essential element of EHP against MG infection, effectively attenuating MG-induced oxidative stress and activation of the TLR2/MyD88/NF-κB pathway. Following QUE therapy, IL-1, IL-6, and TNF-α content and expression were downregulated, whereas IL-4 and IL-10 expression were upregulated, eventually suppressing the inflammatory response both in vitro and in vivo. Together, this study presents a strong rationale for using QUE as a therapeutic strategy to inhibit MG infection-induced inflammatory damage and oxidative stress.

Infection, Transmission, Pathogenesis and Vaccine Development against Mycoplasma gallisepticum

Mycoplasma sp. comprises cell wall-less bacteria with reduced genome size and can infect mammals, reptiles, birds, and plants. Avian mycoplasmosis, particularly in chickens, is primarily caused by Mycoplasma gallisepticum (MG) and Mycoplasma synoviae. It causes infection and pathology mainly in the respiratory, reproductive, and musculoskeletal systems. MG is the most widely distributed pathogenic avian mycoplasma with a wide range of host susceptibility and virulence. MG is transmitted both by horizontal and vertical routes. MG infection induces innate, cellular, mucosal, and adaptive immune responses in the host. Macrophages aid in phagocytosis and clearance, and B and T cells play critical roles in the clearance and prevention of MG. The virulent factors of MG are adhesion proteins, lipoproteins, heat shock proteins, and antigenic variation proteins, all of which play pivotal roles in host cell entry and pathogenesis. Prevention of MG relies on farm and flock biosecurity, management strategies, early diagnosis, use of antimicrobials, and vaccination. This review summarizes the vital pathogenic mechanisms underlying MG infection and recapitulates the virulence factors of MG-host cell adhesion, antigenic variation, nutrient transport, and immune evasion. The review also highlights the limitations of current vaccines and the development of innovative future vaccines against MG.

Common viral and bacterial avian respiratory infections: an updated review

Many pathogens that cause chronic diseases in birds use the respiratory tract as a primary route of infection, and respiratory disorders are the main leading source of financial losses in the poultry business. Respiratory infections are a serious problem facing the poultry sector, causing severe economic losses. Avian influenza virus, Newcastle disease virus, infectious bronchitis virus, and avian pneumovirus are particularly serious viral respiratory pathogens. Mycoplasma gallisepticum, Staphylococcus, Bordetella avium, Pasteurella multocida, Riemerella anatipestifer, Chlamydophila psittaci, and Escherichia coli have been identified as the most serious bacterial respiratory pathogens in poultry. This review gives an updated summary, incorporating the latest data, about the evidence for the circulation of widespread, economically important poultry respiratory pathogens, with special reference to possible methods for the control and prevention of these pathogens.

A Multiplex PCR Assay for Differential Identification of Wild-type and Vaccine Strains of Mycoplasma gallisepticum

Mycoplasma gallisepticum (MG) can cause respiratory disease in chickens and result in serious economic losses in the chicken industry. The use of live vaccines has been a favorable option for the control of MG infection in multi-age commercial layers and broiler breeders. There are three live vaccines, including ts-11, 6/85, and F strain, that have been commonly used in various parts of the world, including South Korea. The definitive diagnosis of the infection, therefore, requires the differentiation of wild-type field strains of MG from the vaccine strains used. Thus, we aimed to develop a novel multiplex PCR assay to discriminate between vaccine strains (ts-11, 6/85, and F strain) and wild-type field strains of MG isolated from infected chickens. We designed four novel primer sets that are each specific to MG species, ts-11, 6/85, and F strain. The multiplex PCR assay using the primer sets differentially identified wild-type and vaccine strains of MG but did not detect other avian bacteria. The detection limit of this assay was 250 fg/μL of genomic DNA of each strain tested. In addition, this assay was applied to 36 MG strains isolated from chickens over the past 20 years in South Korea. As a result, the assay identified 22 wild-type strains and 14 vaccine strains. Consequently, the novel multiplex PCR assay can discriminate between vaccine and wild-type field strains of MG and could be a valuable tool for the diagnosis of MG infection in MG-vaccinated chicken flocks.

Genome Editing of Veterinary Relevant Mycoplasmas Using a CRISPR-Cas Base Editor System

Mycoplasmas are minimal bacteria that infect humans, wildlife, and most economically relevant livestock species. Mycoplasma infections cause a large range of chronic inflammatory diseases, eventually leading to death in some animals. Due to the lack of efficient recombination and genome engineering tools for most species, the production of mutant strains for the identification of virulence factors and the development of improved vaccine strains is limited. Here, we demonstrate the adaptation of an efficient Cas9-Base Editor system to introduce targeted mutations into three major pathogenic species that span the phylogenetic diversity of these bacteria: the avian pathogen Mycoplasma gallisepticum and the two most important bovine mycoplasmas, Mycoplasma bovis and Mycoplasma mycoides subsp. mycoides. As a proof of concept, we successfully used an inducible SpdCas9-pmcDA1 cytosine deaminase system to disrupt several major virulence factors in these pathogens. Various induction times and inducer concentrations were evaluated to optimize editing efficiency. The optimized system was powerful enough to disrupt 54 of 55 insertion sequence transposases in a single experiment. Whole-genome sequencing of the edited strains showed that off-target mutations were limited, suggesting that most variations detected in the edited genomes are Cas9-independent. This effective, rapid, and easy-to-use genetic tool opens a new avenue for the study of these important animal pathogens and likely the entire class Mollicutes.

IMPORTANCE Mycoplasmas are minimal pathogenic bacteria that infect a wide range of hosts, including humans, livestock, and wild animals. Major pathogenic species cause acute to chronic infections involving still poorly characterized virulence factors. The lack of precise genome editing tools has hampered functional studies of many species, leaving multiple questions about the molecular basis of their pathogenicity unanswered. Here, we demonstrate the adaptation of a CRISPR-derived base editor for three major pathogenic species: Mycoplasma gallisepticum, Mycoplasma bovis, and Mycoplasma mycoides subsp. mycoides. Several virulence factors were successfully targeted, and we were able to edit up to 54 target sites in a single step. The availability of this efficient and easy-to-use genetic tool will greatly facilitate functional studies of these economically important bacteria.

Inactivated pentavalent vaccine against mycoplasmosis and salmonellosis for chickens

Mycoplasma and Salmonella are serious pathogens threaten the poultry industry. This study aimed to prepare and evaluate an inactivated pentavalent vaccine targeting bacteria, including Salmonella enterica serovar Typhimurium (ST), Salmonella enterica serovar Enteritidis (SE), Salmonella enterica serovar Kentucky (SK), Mycoplasma gallisepticum (MG), and Mycoplasma synoviae (MS), from locally isolated strains. The prepared vaccine was adjuvanted with Montanide ISA70 oil and then tested for safety, sterility, and potency. The vaccine efficacy was evaluated in 110 specific pathogen-free, 1-day-old chicks, which were divided into three groups as follows: 1) vaccinated group (50 birds), which was subdivided into five subgroups of ten birds each; 2) control positive (challenged) group (50 birds), which was subdivided into five subgroups of ten birds each; and 3) control negative (blank) group, which included ten birds. Chicks in group 1 were administered the first dose of vaccine at 7 d of age followed by a booster dose after 3 wk. At 3 wk after booster vaccination, the chicks who were administered the booster dose were challenged and kept under observation until the end of the experiment when the chicks were approximately 10 wk. Details of clinical symptoms, daily mortality, weights, and postmortem lesions; serum samples; cloacal swabs; and nasal swabs were collected during the experiment. The humoral immune response to the prepared pentavalent vaccine was assessed using enzyme-linked immunosorbent assay. Our findings revealed that the prepared vaccine showed high protective antibody titers against Salmonella and Mycoplasma with 100% efficacy and no mortalities (100% survival rate) were recorded in vaccinated and challenged birds. The vaccine reduced both clinical signs and bacterial shedding post challenge in vaccinated birds in comparison with control positive group. The prepared vaccine did not affect the body weight gain of the vaccinated birds in comparison with control negative birds. The current study concluded that locally manufactured inactivated pentavalent vaccine offers protection to birds and could be employed as an effective tool along with biosecurity measures to overcome mycoplasmosis and salmonellosis in layer and breeder chicken farms in Egypt.

Mycoplasmas as Host Pantropic and Specific Pathogens: Clinical Implications, Gene Transfer, Virulence Factors, and Future Perspectives

Mycoplasmas as economically important and pantropic pathogens can cause similar clinical diseases in different hosts by eluding host defense and establishing their niches despite their limited metabolic capacities. Besides, enormous undiscovered virulence has a fundamental role in the pathogenesis of pathogenic mycoplasmas. On the other hand, they are host-specific pathogens with some highly pathogenic members that can colonize a vast number of habitats. Reshuffling mycoplasmas genetic information and evolving rapidly is a way to avoid their host's immune system. However, currently, only a few control measures exist against some mycoplasmosis which are far from satisfaction. This review aimed to provide an updated insight into the state of mycoplasmas as pathogens by summarizing and analyzing the comprehensive progress, current challenge, and future perspectives of mycoplasmas. It covers clinical implications of mycoplasmas in humans and domestic and wild animals, virulence-related factors, the process of gene transfer and its crucial prospects, the current application and future perspectives of nanotechnology for diagnosing and curing mycoplasmosis, Mycoplasma vaccination, and protective immunity. Several questions remain unanswered and are recommended to pay close attention to. The findings would be helpful to develop new strategies for basic and applied research on mycoplasmas and facilitate the control of mycoplasmosis for humans and various species of animals.

A genetic toolkit and gene switches to limit Mycoplasma growth for biosafety applications

Mycoplasmas have exceptionally streamlined genomes and are strongly adapted to their many hosts, which provide them with essential nutrients. Owing to their relative genomic simplicity, Mycoplasmas have been used to develop chassis for biotechnological applications. However, the dearth of robust and precise toolkits for genomic manipulation and tight regulation has hindered any substantial advance. Herein we describe the construction of a robust genetic toolkit for M. pneumoniae, and its successful deployment to engineer synthetic gene switches that control and limit Mycoplasma growth, for biosafety containment applications. We found these synthetic gene circuits to be stable and robust in the long-term, in the context of a minimal cell. With this work, we lay a foundation to develop viable and robust biosafety systems to exploit a synthetic Mycoplasma chassis for live attenuated vectors for therapeutic applications.

Mycoplasmas are minimal cell model organisms but lack genetic tools. Here the authors provide a robust genetic toolkit for Mycoplasma demonstrating gene circuit engineering applications.

Genome Engineering in Mycoplasma gallisepticum Using Exogenous Recombination Systems

Mycoplasma gallisepticum (Mgal) is a common pathogen of poultry worldwide that has recently spread to North American house finches after a single host shift in 1994. The molecular determinants of Mgal virulence and host specificity are still largely unknown, mostly due to the absence of efficient methods for functional genomics. After evaluating two exogenous recombination systems derived from phages found in the phylogenetically related Spiroplasma phoeniceum and the more distant Bacillus subtilis, the RecET-like system from B. subtilis was successfully used for gene inactivation and targeted replacement in Mgal. In a second step, the Cre-lox recombination system was used for the removal of the antibiotic resistance marker in recombinant mutants. This study therefore describes the first genetic tool for targeted genome engineering of Mgal and demonstrates the efficiency of heterologous recombination systems in minimal bacteria.

Glycyrrhizic Acid against Mycoplasma gallisepticum-Induced Inflammation and Apoptosis Through Suppressing the MAPK Pathway in Chickens

Mycoplasma gallisepticum (MG) is the primary pathogen of chronic respiratory diseases (CRDs) in chickens. In poultry production, antibiotics are mostly used to prevent and control MG infection, but the drug resistance and residue problems caused by them cannot be ignored. Glycyrrhizic acid (GA) is derived from licorice, a herb traditionally used to treat various respiratory diseases. Our study results showed that GA significantly inhibited the mRNA and protein expression of pMGA1.2 and GapA in vitro and in vivo. Furthermore, the network pharmacology study revealed that GA most probably resisted MG infection through the MAPK signaling pathway. Our results demonstrated that GA inhibited MG-induced expression of MMP2/MMP9 and inflammatory factors through the p38 and JUN signaling pathways, but not the ERK pathway in vitro. Besides, histopathological sections showed that GA treatment obviously attenuated tracheal and lung damage caused by MG invasion. In conclusion, GA can inhibit MG-triggered inflammation and apoptosis by suppressing the expression of MMP2/MMP9 through the JNK and p38 pathways and inhibit the expression of virulence genes to resist MG. Our results suggest that GA might serve as one of the antibiotic alternatives to prevent MG infection.

Challenges in Veterinary Vaccine Development

Animals provide food and clothing in addition to other value-added products. Changes in diet and lifestyle have increased the consumption and the use of animal products. Infectious diseases in animals are a major threat to global animal health and its welfare; their effective control is crucial for agronomic health, for safeguarding food security and also alleviating rural poverty. Development of vaccines has led to increased production of healthy poultry, livestock, and fish. Animal production increases have alleviated food insecurity. In addition, development of effective vaccines has led to healthier companion animals. However, challenges remain including climate change that has led to enhancement in vectors and pathogens that may lead to emergent diseases in animals. Preventing transmission of emerging infectious diseases at the animal-human interface is critically important for protecting the world population from epizootics and pandemics. Hence, there is a need to develop new vaccines to prevent diseases in animals. This review describes the broad challenges to be considered in the development of vaccines for animals.

Beware of Mycoplasma Anti-immunoglobulin Strategies

Mycoplasmas are small, genome-reduced bacteria. They are obligate parasites that can be found in a wide range of host species, including the majority of livestock animals and humans. Colonization of the host can result in a wide spectrum of outcomes. In many cases, these successful parasites are considered commensal, as they are found in the microbiota of asymptomatic carriers. Conversely, mycoplasmas can also be pathogenic, as they are associated with a range of both acute and chronic inflammatory diseases which are problematic in veterinary and human medicine. The chronicity of mycoplasma infections and the ability of these bacteria to infect even recently vaccinated individuals clearly indicate that they are able to successfully evade their host’s humoral immune response. Over the years, multiple strategies of immune evasion have been identified in mycoplasmas, with a number of them aimed at generating important antigenic diversity. More recently, mycoplasma-specific anti-immunoglobulin strategies have also been characterized. Through the expression of the immunoglobulin-binding proteins protein M or mycoplasma immunoglobulin binding (MIB), mycoplasmas have the ability to target the host’s antibodies and to prevent them from interacting with their cognate antigens. In this review, we discuss how these discoveries shed new light on the relationship between mycoplasmas and their host’s immune system. We also propose that these strategies should be taken into consideration for future studies, as they are key to our understanding of mycoplasma diseases' chronic and inflammatory nature and are probably a contributing factor to reduce vaccine efficacy.

Exosomal miR-181a-5p reduce Mycoplasma gallisepticum (HS strain) infection in chicken by targeting PPM1B and activating the TLR2-mediated MyD88/NF-κB signaling pathway

Mycoplasma gallisepticum (MG) is one of the most important pathogens that causes chronic respiratory disease (CRD) in chickens. Exosomes secreted from cells have been well demonstrated to deliver miRNAs to recipient cells to modulate cellular functions. The purpose of this study is to explore the underlying functions and mechanisms of exosomal miR-181a-5p in MG-HS infection. In this study, we found that miR-181a-5p expression in vivo and in vitro was significantly up-regulated after MG-HS infection. It was also upregulated in exosomes, which were derived from MG-HS-infected type-II pneumocytes cells (CP-II). In addition, exosomes secreted by MG-HS-infected CP-II were able to transfer miR-181a-5p to recipient chicken embryo fibroblast cells (DF-1), resulting in a significant upregulation of miR-181a-5p expression in recipient DF-1 cells. We further identified that Mg²⁺/Mn²⁺-dependent protein phosphatase 1B (PPM1B) was the target gene of miR-181a-5p. Overexpression of miR-181a-5p or knockdown of PPM1B activated the nuclear factor-κB (NF-κB) signaling pathway, whereas inhibition of miR-181a-5p and overexpression of PPM1B led to the opposite results. Besides, up-regulation of miR-181a-5p significantly increased the expression of toll-like receptor 2 (TLR2), myeloid differentiation factor 88 (MyD88), tumor necrosis factors alpha (TNF-α) and interleukin-1β (IL-1β), whereas inhibition of miR-181a-5p showed a contrary result. Up-regulation of miR-181a-5p promoted cell proliferation, cell cycle progression and inhibited apoptosis to resist MG-HS infection. Moreover, overexpression of miR-181a-5p significantly negative regulated the expression of Mycoplasma gallisepticum adhesin protein (pMGA1.2) by directly inhibiting PPM1B. Thus, we concluded that exosomal miR-181a-5p from CP-II cells activated the TLR2-mediated MyD88/NF-κB signaling pathways by directly targeting PPM1B to promote the expression of pro-inflammatory cytokines for defending against MG-HS infection in recipient DF-1 cells.

Baicalin alleviates Mycoplasma gallisepticum-induced oxidative stress and inflammation via modulating NLRP3 inflammasome-autophagy pathway

Baicalin is a well-known flavonoid compound, possess therapeutic potential against inflammatory diseases. Previous studies reported that Mycoplasma gallisepticum (MG) induced inflammatory response and immune dysregulation inside the host body. However, the underlying molecular mechanisms of baicalin against MG-infected chicken-like macrophages (HD11 cells) are still illusive. Oxidant status and total reactive oxygen species (ROS) were detected by ELISA assays and flow cytometry respectively. Mitochondrial membrane potential (ΔΨ_M) was evaluated by immunofluorescence microscopy. Transmission electron microscopy was used for ultrastructural analysis. The hallmarks of inflammation and autophagy were determined by western blotting. Oxidative stress and reactive oxygen species (ROS) were significantly enhanced in the MG-infected HD11 cells. MG infection caused disruption in the mitochondrial membrane potential (ΔΨ_M) compared to the control conditions. Meanwhile, baicalin treatment reduced MG-induced reactive oxygen species (ROS), oxidative stress and alleviated the disruption in ΔΨ_M. The activities of inflammatory markers were significantly enhanced in the MG-infected HD11 cells. Increased protein expressions of TLR-2-NF-κB pathway, NLRP3-inflammasome and autophagy-related proteins were detected in the MG-infected HD11 cells. Besides, baicalin treatment significantly reduced the protein expressions of TLR-2-NF-κB pathway and NLRP3 inflammasome. While, the autophagy-related proteins were significantly enhanced with baicalin treatment in a dose-dependent manner in the MG-infected HD11 cells. The results showed that baicalin prevented HD11 cells from MG-induced oxidative stress and inflammation via the opposite modulation of TLR-2-NF-κB-mediated NLRP3-inflammasome pathway and autophagy, and baicalin could be a promising candidate for the prevention of inflammatory effects caused by MG-infection in macrophages.

Pooled molecular occurrence of Mycoplasma gallisepticum and Mycoplasma synoviae in poultry: A systematic review and meta-analysis

Worldwide, Mycoplasma gallisepticum (MG) and M. synoviae (MS) are the main agents responsible for chronic respiratory disease in poultry. Therefore, we conducted a systematic review and meta-analysis to estimate their occurrence. We searched electronic databases to find peer-reviewed publications reporting the molecular detection of MG and MS in poultry and used meta-analysis to estimate their pooled global occurrence (combined flock and individual), aggregating results at the regional and national levels. We performed a subgroup meta-analysis for subpopulations (broilers, layers, breeders and diverse poultry including turkeys, ducks and ostriches) and used meta-regression with categorical modifiers. We retrieved 2294 publications from six electronic databases and included 85 publications from 33 countries that reported 62 studies with 22,162 samples for MG and 48 studies with 26,413 samples for MS. The pooled global occurrence was 38.4% (95% CI: 23.5-54.5) for MS and 27.0% (20.4-34.2) for MG. Among regions, Europe and Central Asia had the lowest occurrence for both pathogens, while MG and MS were highly prevalent in South Asia and sub-Saharan Africa, respectively. At the national level, MG occurrence was higher in Algeria, Saudi Arabia and Sudan, whereas China, Egypt and Ethiopia reported higher values of MS. Among the poultry subpopulations, MS and MG were more prevalent in the breeders and layers (62.6% and 31.2%, respectively) than in diverse poultry. The year of publication, the sample size and the level of ambient air pollution (measured indirectly by PM2.5) were associated with the occurrence of both mycoplasmas. Our study revealed high and heterogeneous occurrence values of MG and MS and justifies the need for early detection and improved control measures to reduce the spread of these pathogens.

Redox Homeostasis in Poultry: Regulatory Roles of NF-κB

Redox biology is a very quickly developing area of modern biological sciences, and roles of redox homeostasis in health and disease have recently received tremendous attention. There are a range of redox pairs in the cells/tissues responsible for redox homeostasis maintenance/regulation. In general, all redox elements are interconnected and regulated by various means, including antioxidant and vitagene networks. The redox status is responsible for maintenance of cell signaling and cell stress adaptation. Physiological roles of redox homeostasis maintenance in avian species, including poultry, have received limited attention and are poorly characterized. However, for the last 5 years, this topic attracted much attention, and a range of publications covered some related aspects. In fact, transcription factor Nrf2 was shown to be a master regulator of antioxidant defenses via activation of various vitagenes and other protective molecules to maintain redox homeostasis in cells/tissues. It was shown that Nrf2 is closely related to another transcription factor, namely, NF-κB, responsible for control of inflammation; however, its roles in poultry have not yet been characterized. Therefore, the aim of this review is to describe a current view on NF-κB functioning in poultry with a specific emphasis to its nutritional modulation under various stress conditions. In particular, on the one hand, it has been shown that, in many stress conditions in poultry, NF-κB activation can lead to increased synthesis of proinflammatory cytokines leading to systemic inflammation. On the other hand, there are a range of nutrients/supplements that can downregulate NF-κB and decrease the negative consequences of stress-related disturbances in redox homeostasis. In general, vitagene-NF-κB interactions in relation to redox balance homeostasis, immunity, and gut health in poultry production await further research.

Lactobacillus salivarius ameliorated Mycoplasma gallisepticum-induced inflammatory injury and secondary Escherichia coli infection in chickens: Involvement of intestinal microbiota

Mycoplasma gallisepticum (MG) infection alone or in combination with other pathogens have brought huge economic losses to the poultry industry. The intestinal microbiota plays a critical role in host defence against respiratory infection. To explore the role of intestinal microbiota in MG-induced inflammation-mediated lung injury and secondary Escherichia coli infection, MG infection model and fecal microbiota transplantation model were developed. The results showed that MG infection changed gut microbiota composition along with lung inflammation injury. Fecal microbiota transplantation from chickens infected with MG to antibiotics cocktail treated chickens decreased host defense against Escherichia coli due to impaired intestinal mucosal barrier, downregulated the mRNA expression levels of host defense enzymes and blocked autophagic flux. Lactobacillus salivarius intake alleviated lung inflammation injury caused by MG infection and increased host defense against Escherichia coli by improved gut microbiota composition. These results highlighted the role of gut microbiota in MG-infection induced lung inflammation injury and secondary infection that offered a new strategy for preventive intervention against MG infection.

Mycoplasma gallisepticum infection triggered histopathological changes, oxidative stress and apoptosis in chicken thymus and spleen

Previous studies mainly focused on the inflammatory responses caused by Mycoplasma gallisepticum (MG) in the chicken respiratory mucosa, setting the stage for chronic infection and disease manifestation. However, the underlying mechanism is still unknown. Spleen and thymus are important immune organs, which play a critical role in eliciting protective immune responses to ensure healing process and elimination of harmful stimuli. In the present study, the effects of MG infection on chicken spleen and thymus were investigated. The results showed that MG infection reduced antioxidant activities and induced oxidative stress in the spleen and thymus tissues. Histological examination showed normal morphology of chicken spleen and thymus in control group compared to MG infection group. In contrast, increased number of necrotic and nuclear debris, lymphocytolysis, prominent reticuloepithelial cells and loose arrangement of cells in the spleen and thymus were seen in MG-infected chickens. Ultrastructural analysis indicated nuclear and mitochondrial damage including mitochondrial swelling, deformation of nuclear membrane and congestion of chromatin material in MG infection group. The mRNA and protein expression of apoptosis-related genes were significantly upregulated in the spleen and thymus of MG-infected chickens compared to control group. Moreover, Terminal deoxynucleotidyl transferase-mediated dUTP nick endlabeling (TUNEL) assay results suggested that MG infection increased the number of positive-stained nuclei in the spleen and thymus. Meanwhile, the mRNA expression of mitochondrial dynamics in the spleen and thymus were altered by MG infection. In summary, these results showed that MG induced oxidative stress and apoptosis, which could be the possible causes associated with the immune damage, structural impairment and disease pathogenesis of MG infection.