Development of a direct competitive ELISA for the detection of Mycoplasma bovis infection based on a monoclonal antibody of P48 protein

Point-of-care potentials of lateral flow-based field screening for Mycoplasma bovis infections: a literature review

Point-of-care (POC) field screening for tools for Mycoplasma bovis (M. bovis) is still lacking due to the requirement for a simple, robust field-applicable test that does not entail specialized laboratory equipment. In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines, this review identifies the methodologies that were retrieved based on our search strategy that have been reported for the diagnosis of m. bovis infection between 2014 and diagnostics. A search criterion was generated to curate 103 articles, which were reduced in number (to 46), following the screening guidelines of PRISMA. The 43 articles included in the study present 25 different assay methods. The assay methods were grouped as microbiological culture, serological assay, PCR-based assay, LAMP-based assay, NGS-based assay, or lateral flow assay. We, however, focus our discussion on the three lateral flow-based assays relative to others, highlighting the advantages they present above the other techniques and their potential applicability as a POC diagnostic test for M. bovis infections. We therefore call for further research on developing a lateral flow-based screening tool that could revolutionize the diagnosis of M. bovis infection.

Mycoplasma bovis mastitis in dairy cattle

Mycoplasma bovis has recently been identified increasingly in dairy cows causing huge economic losses to the dairy industry. M. bovis is a causative agent for mastitis, pneumonia, endometritis, endocarditis, arthritis, otitis media, and many other clinical symptoms in cattle. However, some infected cows are asymptomatic or may not shed the pathogen for weeks to years. This characteristic of M. bovis, along with the lack of adequate testing and identification methods in many parts of the world until recently, has allowed the M. bovis to be largely undetected despite its increased prevalence in dairy farms. Due to growing levels of antimicrobial resistance among wild-type M. bovis isolates and lack of cell walls in mycoplasmas that enable them to be intrinsically resistant to beta-lactam antibiotics that are widely used in dairy farms, there is no effective treatment for M. bovis mastitis. Similarly, there is no commercially available effective vaccine for M. bovis mastitis. The major constraint to developing effective intervention tools is limited knowledge of the virulence factors and mechanisms of the pathogenesis of M. bovis mastitis. There is lack of quick and reliable diagnostic methods with high specificity and sensitivity for M. bovis. This review is a summary of the current state of knowledge of the virulence factors, pathogenesis, clinical manifestations, diagnosis, and control of M. bovis mastitis in dairy cows.

A novel phage-displayed MilA ELISA for detection of antibodies against Myc. bovis in bovine milk

AIMS

The aim of this study was to assess a phage-displayed MilA protein of Myc. bovis in an indirect ELISA for the detection of Myc. bovis antibodies in milk samples.

METHODS AND RESULTS

The desired sequence of milA gene was synthesized and cloned into pCANTAB-F12 phagemid vector. The expression of the MilA on the phage surface was confirmed by Western blotting. The recombinant phage was used in the development of an indirect ELISA to detect Myc. bovis antibodies in milk samples. There was a significant agreement between the results of phage-based ELISA and recombinant GST-MilA ELISA for the detection of Myc. bovis antibodies in milk samples.

CONCLUSIONS

The inexpensive and convenient phage-based ELISA can be used instead of recombinant protein/peptide ELISA as an initial screening of Myc. bovis-associated mastitis.

SIGNIFICANCE AND IMPACT OF STUDY

Mastitis associated with Myc. bovis is a continuous and serious problem in the dairy industry. Sero-monitoring of Myc. bovis infection cases are one of the key factors for surveillance of the infections in dairy farms. Despite the existence of some commercially serological assays for Myc. bovis antibodies, they have some limitations regarding their sensitivity and availability. The development of accurate diagnosis tools could contribute to control programmes of Myc. bovis-associated mastitis in the dairy herds.

The application of aptamer Apt-236 targeting PvpA protein in the detection of antibodies against Mycoplasma gallisepticum

Mycoplasma gallisepticum (M. gallisepticum) is the primary agent of chronic respiratory disease causing important economic losses in the poultry industry. Compared to antibodies, aptamers used to diagnose M. gallisepticum have many advantages, such as being chemically, animal-free produced and easily modifiable without affecting their affinity. Herein, a single-stranded DNA (ssDNA) aptamer Apt-236 which can specifically bind to PvpA protein of M. gallisepticum with a Kd of 1.30 ± 0.18 nM was selected successfully. An indirect blocking ELAA (ib-ELAA) for M. gallisepticum antibodies detection was also developed using Apt-236, in which M. gallisepticum antibodies would block the binding-position of aptamers. Therefor positive sera would prevent color development whereas negative sera will allow a strong color reaction. The ib-ELAA was consistent with other three widely used assays in terms of the growth and decline of the antibody response to M. gallisepticum, and showed substantial agreement with the results obtained using a commercial ELISA kit in clinical chicken sera samples. Therefore, the ib-ELAA developed in this study was a new format for aptamer application and would be an alternative method for the surveillance of M. gallisepticum.

MBOVPG45_0375 Encodes an IgG-Binding Protein and MBOVPG45_0376 Encodes an IgG-Cleaving Protein in Mycoplasma bovis

Mycoplasma bovis is a significant bacterial pathogen which is able to persist in cattle and cause chronic diseases. This phenomenon may relate to M. bovis evading the immune system of the host. Immunoglobulin-binding proteins are widely distributed in a variety of pathogenic bacteria, including some Mycoplasma species. These proteins are considered to help the bacteria evade the immune response of the host. Here we found M. bovis strain PG45 can bind to IgG from several animals. MBOVPG45_0375 encodes a putative membrane protein, has strong amino acid sequence similarity with Immunoglobulin G-binding protein in Mycoplasma mycoides subsp. capri. Hence, we constructed recombinant MBOVPG45_0375 (r0375) in the Escherichia coli expression system and demonstrated that r0375 can bind to IgG non-immunologically rather than specific binding similar to interaction of antigen and antibody. Moreover, r0375 can bind to the Fab fragment of IgG. Also, the binding of r0375 and IgG inhibits the formation of antigen-antibody union. Furthermore, MBOVPG45_0376 encodes an IgG-cleaving protein of M. bovis strain PG45. Nevertheless, r0375 binding to IgG is required for the cleavage activity of recombinant 0376 (r0376). The activity of r0376 is also affected by incubation time and temperature. In addition, we found both MBOVPG45_0375 and MBOVPG45_0376 are membrane proteins of M. bovis strain PG45. These results about MBOVPG45_0375 as an IgG-binding protein and MBOVPG45_0376 as an IgG-cleaving protein offer a new insight into the interaction between M. bovis and its host.

Mycoplasmas bovis P48 induces apoptosis in EBL cells via an endoplasmic reticulum stress-dependent signaling pathway

Mycoplasma bovis (M. bovis) is a small bacterium that lacks a cell wall. M. bovis infection can result in chronic pneumonia and polyarthritis syndrome (CPPS), otitis media, conjunctivitis, and meningitis in feedlot cattle and mastitis in dairy cattle. To gain more understanding of the mechanism of M. bovis and host interaction, this study focused on P48, an important membrane protein involved in M. bovis adhesion, proliferation and virulence. In this study, exogenous P48 protein was introduced to explore its function in embryonic bovine lung (EBL) cells by recombinant vector and protein purification. We found that M. bovis infection inhibited EBL cells growth and enhanced apoptosis. Both intracellular and extracellular P48 protein treatment also induce apoptosis. Moreover, P48 activates endoplasmic reticulum (ER) stress response via increasing ER stress markers expression. To further explore the underlying mechanism, we performed inhibition experiments using ER stress inhibitor 4-PBA and specific siRNA interference against GRP78, and found that P48 protein modulated EBL cells apoptosis in an ER stress signaling-dependent manner. This study provided more data to further understand M. bovis infection mechanism and develop effective anti-mycoplasma strategy.

Development and application of a colloidal carbon test strip for the detection of antibodies against Mycoplasma bovis

Mycoplasma bovis (M. bovis) is an important bovine mycoplasma implicated in economically important clinical diseases, such as respiratory diseases, otitis media, and mastitis. The prevalence of M. bovis-associated mastitis in both cattle and buffaloes has been increasingly recognized as a global problem. High morbidity rates and consequential economic losses have been devastating to the affected cattle and buffalo farms, especially those in developing countries. Therefore, a rapid and accurate method is urgently needed to detect M. bovis. In this study, a rapid and simple lateral flow strip for detecting antibodies against M. bovis was established that used carbon nanoparticles (CNPs) as the labelled materials. The results from the test strip were highly consistent with those from ELISA. The test showed high specificity (100%) and no cross-reaction with other bovine pathogens. The detection sensitivity of the test was also relatively high (97.67%). All the results indicated that the colloidal carbon test strip could serve as a simple, rapid, sensitive, and specific diagnostic method for detecting antibodies against M. bovis at cattle farms.

Progresses on bacterial secretomes enlighten research on Mycoplasma secretome

Bacterial secretome is a comprehensive catalog of bacterial proteins that are released or secreted outside the cells. They offer a number of factors that possess several significant roles in virulence as well as cell to cell communication and hence play a core role in bacterial pathogenesis. Sometimes these proteins are bounded with membranes giving them the shape of vesicles called extracellular vesicles (EVs) or outer membrane vesicles (OMVs). Bacteria secrete these proteins via Sec and Tat pathways into the periplasm. Secreted proteins have found to be important as diagnostic markers as well as antigenic factors for the development of an effective candidate vaccine. Recently, the research in the field of secretomics is growing up and getting more interesting due to their direct involvement in the pathogenesis of the microorganisms leading to the infection. Many pathogenic bacteria have been studied for their secretome and the results illustrated novel antigens. This review highlights the secretome studies of different pathogenic bacteria in humans and animals, general secretion mechanisms, different approaches and challenges in the secretome of Mycoplasma sp.

iTRAQ-based proteomic analysis of Mycoplasma bovis NM-28 strain from two generations for vaccine screening

Mycoplasma bovis is an important pathogenic bacterium affecting cows and cattle. Clinically, an inactivated vaccine of M. bovis is mainly used to prevent infection by this bacterium. The changes that occur in the antigen when M. bovis is continuously passaged in vitro remain unknown. Therefore, we performed an in vitro serial passage of the M. bovis NM-28 strain, which was isolated and identified in our laboratory. An isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics method was used to analyse the differences between generations 3 and 60. Many major membrane proteins or protective antigens reported in the literature did not exhibit changes between these generations. We found an imbalance between growth rate and nutrition in the 60th generation. The proteomics results were verified by western blotting and real-time PCR. Growth curves were also prepared based on colony-forming units (CFUs) between the 3rd and 60th generations. The number of colonies in the 60th generation in the stationary phase was 5 × 10⁹ CFU mL^-1, which was 10-fold higher than that in the 3rd generation. The 60th generation of the NM-28 strain can be used as an inactivated vaccine strain of M. bovis to lower production costs compared to use of the 3rd generation.

A European inter-laboratory trial to evaluate the performance of three serological methods for diagnosis of Mycoplasma bovis infection in cattle using latent class analysis

Background

Mycoplasma bovis (M. bovis) is an emerging bovine pathogen, leading to significant economic losses in the livestock industry worldwide. Infection can result in a variety of clinical signs, such as arthritis, pneumonia, mastitis and keratoconjunctivitis, none of which are M. bovis-specific. Laboratory diagnosis is therefore important. Serological tests to detect M. bovis antibodies is considered an effective indicator of infection in a herd and often used as a herd test. Combined with clinical judgement, it can also be used to implement control strategies and/or to estimate the disease prevalence within a country. However, due to lack of harmonisation of approaches to testing, and serological tests used by different laboratories, comparisons of prevalence data between countries is often difficult. A network of researchers from six European countries designed and participated in an inter-laboratory trial, with the aim of evaluating the sensitivity (Se) and specificity (Sp) of two commercially available ELISA tests (ID Screen® ELISA (IDvet) and BIO K302 ELISA (BIO-X Diagnostics)) for diagnosis of M. bovis infection. Each laboratory received a blinded panel of bovine sera and tested independently, according to manufacturer’s instructions. Western blot analyses (WB) performed by one of the participating laboratories was used as a third diagnostic test in the statistical evaluation of Se and Sp values using latent class analysis.

Results

The Se of WB, the ID Screen® ELISA and the BIO K302 ELISA were determined to be 91.8, 93.5 and 49.1% respectively, and corresponding Sp of the three tests were 99.6, 98.6 and 89.6%, respectively.

Conclusions

The present study is, to our knowledge, the first to present an inter-laboratory comparison of the BIO K302 ELISA and the ID Screen® ELISA. Based on our results, the ID Screen® ELISA showed high consistency with WB and performed with higher precision and accuracy than the BIO K302 ELISA.

A review of mycoplasma diagnostics in cattle

Mycoplasma species have a global distribution causing serious diseases in cattle worldwide including mastitis, arthritis, pneumonia, otitis media and reproductive disorders. Mycoplasma species are typically highly contagious, are capable of causing severe disease, and are difficult infections to resolve requiring rapid and accurate diagnosis to prevent and control disease outbreaks. This review discusses the development and use of different diagnostic methods to identify Mycoplasma species relevant to cattle, with a particular focus on Mycoplasma bovis. Traditionally, the identification and diagnosis of mycoplasma has been performed via microbial culture. More recently, the use of polymerase chain reaction to detect Mycoplasma species from various bovine samples has increased. Polymerase chain reaction has a higher efficiency, specificity, and sensitivity for laboratory diagnosis when compared with conventional culture‐based methods. Several tools are now available for typing Mycoplasma spp. isolates, allowing for genetic characterization in disease outbreak investigations. Serological diagnosis through the use of indirect ELISA allows the detection of antimycoplasma antibodies in sera and milk, with their use demonstrated on individual animal samples as well as BTM samples. While each testing method has strengths and limitations, their combined use provides complementary information, which when interpreted in conjunction with clinical signs and herd history, facilitates pathogen detection, and characterization of the disease status of cattle populations.

Mechanism of Apoptosis Induction by Mycoplasmal Nuclease MGA_0676 in Chicken Embryo Fibroblasts

MGA_0676 has been characterized as a Mycoplasma gallisepticum nuclease that can induce apoptosis of chicken cells. However, the mechanism by which MGA_0676 induces apoptosis has remained unclear. In this study, we evaluated MGA_0676-induced apoptosis and internalization in immortalized chicken embryo fibroblasts (DF-1) and cancer cell lines. The internalization of MGA_0676 was proven through caveolin-mediated endocytosis by blocking the endocytosis with specific inhibitors or with siRNA. We identified the Thif domain of NEDD8-activating enzyme E1 regulatory subunit (NAE) in DF-1 as the target region interacting with the SNC domain of MGA_0676. The interaction between the Thif and SNC domains was observed co-located in the perinuclear and nuclear of DF-1. We found that the interaction between NAE and MGA_0676 increased the ability of apoptosis and accelerated the process of cullin neddylation in DF-1 cells, in turn activating NF-κB. This resulted in the observed aggregation of NF-κB in the nuclei of DF-1 cells. Moreover, the apoptosis induced by MGA_0676 decreased significantly when NF-κB was inhibited by siRNA or BAY 11-7082 or when NAE was silenced by siRNA. Overall, our results demonstrate that MGA_0676 is internalized through caveolin-mediated endocytosis, interacts with SNC-dependent Thif to accelerate the process of cullin neddylation and activates NF-κB in DF-1 cells, ultimately playing a key role in apoptosis in chicken cells. Our results indicate MGA_0676 constitutes a critical etiological virulence factor of the respiratory disease caused by M. gallisepticum. This study also opens a venue to investigate MGA_0676 as a potential candidate as pro-apoptotic drug in cancer studies.

The Performance of Three Immune Assays to Assess the Serological Status of Cattle Experimentally Exposed to Mycoplasma bovis

Mycoplasma bovis is associated with several clinical syndromes of cattle. Currently, limited information is available on the sensitivity (Se) and specificity (Sp) of serological assays used for the detection of M. bovis-specific antibodies. Consequently, it is difficult to critically evaluate the outcomes of studies that use these assays. Therefore, the current study used bovine sera sourced from M. bovis exposure studies from three countries to estimate the Se and Sp of two commercial M. bovis enzyme-linked immunosorbent assays (ELISA), BIO K302 and BIO K260, and Western blotting. Western blotting had the highest Se estimate of 74% (95% confidence interval (CI): 16–98%), compared to the BIO K302: 47% (95% CI: 10–87%) and BIO K260: 28% (95% CI: 1–92%). However, for Sp, the BIO K302: 96% (95% CI: 87–99%) and the BIO K260: 100% (95% CI: 93–100%) out-performed Western blotting: 88% (95% CI: 56–98%). Western blotting was the best assay for detecting seroconversion, correctly identifying 61% (95% CI: 29–86%) of exposed animals compared to 35% for BIO K302 (95% CI: 21–54%) and 8% for BIO K260 (95% CI: 0–87%). While none of the methods assessed had high Se and Sp, the availability of these estimates will aid in the interpretation of studies that use these assays. The results of this study highlight the difficulties encountered when using serology to detect exposure to M. bovis in cattle.

Proteomics analysis and its role in elucidation of functionally significant proteins in Mycoplasma bovis

Mycoplasma bovis (M. bovis) is an emerging devastating cause of pneumonia in dairy and feedlot calves around the world, largely due to its increasing resistance to new generation effective antibiotics and lack of efficient vaccine. Failure of protective measures against M. bovis is mainly due to nonspecific targets. Most of the virulent factors of M. bovis and their underlying mechanisms are obscure to devise an effective control strategy. Full genome sequences of M. bovis strains basically provided a useful platform for the accurate identification of novel proteins and understanding their biological value using proteomics tools. Most of the previously documented proteins of M. bovis are involved in adhesion to host cells and are antigenic in nature. However, host immune response to some antigens proved to be non-protective. For the diagnosis of M. bovis infection, a serological assay based on whole cell proteins of M. bovis is commercially available but the specificity is likely to be improved by identifying and targeting the specific proteins. Many of the predicted proteins of M. bovis remain hypothetical, as their functions are yet to be confirmed experimentally. This review mainly focuses on the proteomics analysis of M. bovis and its role in identification of the virulence related factors and antigenic proteins of M. bovis. Future research directions have also been highlighted in this script for the application of important antigenic factors of M. bovis.

Status of the development of a vaccine against Mycoplasma bovis

Mycoplasma bovis is an important pathogen of cattle and, despite numerous efforts an effective vaccine for control of the disease it causes remains elusive. Although we now know more about the biology of this pathogen, information is lacking about appropriate protective antigens, the type of immune response that confers protection and adjuvants selection. The use of conserved recombinant proteins, selected using in silico approaches, as components of a vaccine may be a better choice over bacterin-based vaccines due to the limited protection afforded by them and adverse reactions caused by them. More studies are needed on the characterization of host-pathogen interactions and to elucidate M. bovis products modulating these interactions. These products could be the basis for development of vaccines to control M. bovis infections in dairy farms and feedlots.

Immunoproteomic identification of MbovP579, a promising diagnostic biomarker for serological detection of Mycoplasma bovis infection

A lack of knowledge regarding the antigenic properties of Mycoplasma bovis proteins prevents the effective control of bovine infections using immunological approaches. In this study, we detected and characterized a specific and sensitive M. bovis diagnostic biomarker. After M. bovis total proteins and membrane fractions were separated with two dimensional gel electrophoresis, proteins reacting with antiserawere detected using MALDI-TOF MS. Thirty-nine proteins were identified, 32 of which were previously unreported. Among them, immunoinformatics predicted eight antigens, encoded by Mbov_0106, 0116, 0126, 0212, 0275, 0579, 0739, and 0789, to have high immunological value. These genes were expressed in E. coli after mutagenesis of UGA to UGG using overlap extension PCR. A lipoprotein, MbovP579, encoded by a functionally unknown gene, was a sensitive and specific antigen for detection of antibodies in sera from both M. bovis-infected and vaccinated cattle. The specificity of MbovP579 was confirmed by its lack of cross-reactivity with other mycoplasmas, including Mycoplasma agalactiae. An iELISA based on rMbovP579 detected seroconversion 7 days post-infection (dpi). The ELISA had sensitivity of 90.2% (95% CI: 83.7%, 94.3%) and a specificity of 97.8% (95% CI: 88.7%, 99.6%) with clinical samples. Additional comparative studies showed that both diagnostic and analytic sensitivities of the ELISA were higher than those of a commercially available kit (p<0.01). We have thus detected and characterized the novel antigen, MbovP579, and established an rMbovP579-based ELISA as a highly sensitive and specific method for the early diagnosis of M. bovis infection.