Tween 20 soluble proteins of Mycoplasma hyopneumoniae as antigen for an enzyme linked immunosorbent assay

Improving Mycoplasma hyopneumoniae diagnostic capabilities by harnessing the infection dynamics

Mycoplasma hyopneumoniae remains one of the most problematic bacterial pathogens for pig production. Despite an abundance of observational and laboratory testing capabilities for this organism, diagnostic interpretation of test results can be challenging and ambiguous. This is partly explained by the chronic nature of M. hyopneumoniae infection and its tropism for lower respiratory tract epithelium, which affects diagnostic sensitivities associated with sampling location and stage of infection. A thorough knowledge of the available tools for routine M. hyopneumoniae diagnostic testing, together with a detailed understanding of infection dynamics, are essential for optimizing sampling strategies and providing confidence in the diagnostic process. This study reviewed known information on sampling and diagnostic tools for M. hyopneumoniae and summarized literature reports of the dynamics of key infection outcomes, including clinical signs, lung lesions, pathogen detection, and humoral immune responses. Such knowledge could facilitate better understanding of the performance of different diagnostic approaches at various stages of infection.

Use of serological and mucosal immune responses to Mycoplasma hyopneumoniae antigens P97R1, P46 and P36 in the diagnosis of infection

Currently available ELISAs used to diagnose Mycoplasma hyopneumoniae infection in pigs have high specificity but low sensitivity. To develop more sensitive assays, the kinetics of specific serum IgG and respiratory mucosal sIgA responses against three M. hyopneumoniae antigens, namely, P97R1 (an adhesin protein), P46 (a membrane protein), and P36 (a cytosolic protein), were characterised over 133 days following experimental infection. Immunoglobulin G against the three proteins remained at high concentrations from 28 to 133 days post-infection (dpi), although IgG against P97R1 was detected earlier and was more reactive than the other two antigens under assessment. Mucosal sIgA appeared earlier than serum IgG but did not persist as long; sIgA concentrations against P97R1 were the highest. Seroconversion was detected 2 weeks earlier with the P97R1-based ELISA than with a commercially available ELISA. On analysis of serum samples from five pig farms that did not use a M. hyopneumoniae vaccine, the P97R1-based IgG ELISA demonstrated a 73.6% coincidence rate with the commercial kit. Moreover, this more specific P97R1-based ELISA detected more positive samples than the commercial kit (52.8% vs. 39.2%). It was concluded that the systemic immune response to M. hyopneumoniae infection in pigs was delayed in onset but persistent whereas the mucosal response developed more rapidly but was less sustained. The P97R1 antigen was identified as a suitable serological marker for diagnosing M. hyopneumoniae infection in pigs, particularly early stage infection.

Evaluation of enzyme-linked immunosorbent assays for detection of Mycoplasma bovis-specific antibody in bison sera

Mycoplasma bovis has recently emerged as a significant and costly infectious disease problem in bison. A method for the detection of M. bovis-specific serum antibodies is needed in order to establish prevalence and transmission patterns. Enzyme-linked immunosorbent assays (ELISAs) validated for the detection of M. bovis-specific serum IgG in cattle are commercially available, but their suitability for bison sera has not been determined. A collection of bison sera, most from animals with a known history of infection or vaccination with M. bovis, was tested for M. bovis-specific IgG using commercially available kits as well as an in-house ELISA in which either cattle or bison M. bovis isolates were used as a source of antigen. Comparison of the results demonstrates that ELISAs optimized for cattle sera may not be optimal for the identification of bison seropositive for M. bovis, particularly those with low to moderate antibody levels. The reagent used for the detection of bison IgG and the source of the antigen affect the sensitivity of the assay. Optimal performance was obtained when the capture antigen was derived from bison isolates rather than cattle isolates and when a protein G conjugate rather than an anti-bovine IgG conjugate was used for the detection of bison IgG.

Serological diagnosis of enzootic pneumonia of swine by a double-sandwich enzyme-linked immunosorbent assay using a monoclonal antibody and recombinant antigen (P46) of Mycoplasma hyopneumoniae

To facilitate the control of enzootic pneumonia (EP) of swine caused by Mycoplasma hyopneumoniae, the complement fixation (CF) test has been used for the detection of M. hyopneumoniae antibodies. However, the CF test is a cumbersome and time-consuming technique and cross-reactivity are major drawbacks associated with this method. To circumvent these drawbacks, we have developed a double-sandwich enzyme-linked immunosorbent assay (ELISA), consisting of purified monoclonal antibody (Mab) against the 46 kDa surface antigen (P46) of M. hyopneumoniae and recombinant P46 protein expressed in Escherichia coli, for the detection of antibodies to M. hyopneumoniae in serum samples from pigs experimentally inoculated with M. hyopneumoniae and from naturally infected pigs, and compared the practical usefulness of ELISA using the CF test. In experimentally inoculated pigs, the CF and ELISA antibodies were detected at almost the same time, and a good correlation was demonstrated between the CF test and the ELISA. In a survey conducted on field samples, the seropositivity by ELISA in pigs of age 2-6 months was increased. At the time of slaughter, approximately 80% of the animals were seropositive for ELISA. However, a gradual decrease in the prevalence of ELISA positive samples was observed in sows with increasing parity. No correlation was seen between the results obtained with the two methods in the clinical samples. The CF test appears to have limited value for the diagnosis of EP in conventional herds because nonspecific reactions were frequently observed. Therefore, this ELISA is a useful alternative to the CF test currently used for the diagnosis of EP.

Serological study of contagious agalactia in herds of goats in the Canary Islands

An indirect ELISA, using local strains of Mycoplasma agalactiae and Mycoplasma mycoides subspecies mycoides large colony (MmmLC), was applied to evaluate the seroprevalence of M agalactiae and MmmLC in flocks of goats on each of the Canary Islands. In total 3890 samples of serum were collected from 204 flocks. The results indicated that the seroprevalence of both organisms is high on all the islands; average values of 55 per cent and 67 per cent were recorded, respectively, for M agalactiae and MmmLC.

An attempt at measuring health in nucleus and multiplier pig farms

A pilot epidemiological inquiry was undertaken in France in a group of 205 nucleus and multiplier pig farms. The aim was to find out a method for a quantitative evaluation of the health level in farms selling young breeders. An exhaustive protocol was prepared for data collection. The sources of information were clinical inspections on the farms, meat inspection data at slaughter and laboratory investigations. Data processing issued in the selection of a profile made of 14 prevailing health indicators. These were then associated so as to set up a health index with an overall score. In a second phase, the relevance of the method with respect to disease transmission was assessed. The principle was a contact challenge within totally controlled facilities between SPF pigs hysterectomy-derived and gilts taken from farms with different health scores as previously checked. The contact lasted for 28 days. Eleven farms were chosen and in every one of them 7 gilts were sampled and 10 SPF pigs were assigned to each of these farms. All the pigs were submitted to a detailed observation. At the end of it the pigs were euthanized at the laboratory and checked to find out any lesions and infectious agents. A wide range of symptoms appeared among the SPF pigs. Mortality rate was 14.6%. Pneumonia affected 23.7% of them. A relationship was found between the germ transfer and the severity of the troubles. The degree of illness in SPF pigs was clearly related to the score obtained previously in the corresponding farms. Consequently, the method was considered as valid with respect to health evaluation.

Vaccine efficacy of the attenuated Erysipelothrix rhusiopathiae YS-19 expressing a recombinant protein of Mycoplasma hyopneumoniae P97 adhesin against mycoplasmal pneumonia of swine

The attenuated Erysipelothrix rhusiopathiae YS-19 strain was constructed for the purpose of delivering the C-terminal portion of the Mycoplasma hyopneumoniae P97 adhesin to the mucosal surface of the respiratory tract of pigs. In this study, the efficacy of the YS-19 vaccine against mycoplasmal pneumonia of swine was evaluated. Animal experiments revealed that intranasal immunization of pigs with the YS-19 strain significantly reduced the severity of pneumonic lung lesions caused by M. hyopneumoniae infection. In YS-19-immunized pigs, P97-specific serum antibodies were not detected. However, when stimulated with the P97 protein, peripheral blood mononuclear cells from the YS-19-immunized pigs had a significantly higher stimulation index (P<0.05) than that of cells from control pigs at 7 days post-challenge.

Erysipelothrix rhusiopathiae YS-1 as a live vaccine vehicle for heterologous protein expression and intranasal immunization of pigs

We have developed a system in which a foreign antigen is delivered and expressed on the surface of an attenuated strain of Erysipelothrix rhusiopathiae YS-1 and have examined the ability of a such recombinant E. rhusiopathiae strain to function as a mucosal vaccine vector. The C-terminal portion, including two repeat regions, R1 and R2, of the P97 adhesin of Mycoplasma hyopneumoniae strain E-1 was successfully translocated and expressed on the E. rhusiopathiae YS-1 cell surface after it was fused to SpaA.1, a cell surface protective antigen of E. rhusiopathiae. BALB/c mice subcutaneously immunized with the E. rhusiopathiae recombinant strains developed specific antibodies against SpaA.1 protein and were protected from lethal challenge with the highly virulent homologous E. rhusiopathiae Fujisawa-SmR strain, showing the efficacy of this heterologous-antigen expression system as a vaccine against E. rhusiopathiae infection. To determine whether protective immune responses are induced in target species, newborn, specific-pathogen-free piglets were immunized intranasally with a recombinant strain designated YS-19. The immunized piglets developed specific anti-SpaA.1 immunoglobulin G (IgG) antibodies in their serum and were protected from death by erysipelas, showing that mucosal vaccination of piglets with YS-19 induces systemic immune responses. Furthermore, YS-19-immunized piglets showed higher levels of P97-specific IgA antibodies in the respiratory tract than did YS-1-immunized piglets. Thus, E. rhusiopathiae YS-1 appears to be a promising vaccine vector for mucosal delivery that can induce local and systemic immune responses.

Development of a blocking enzyme-linked immunosorbent assay for detection of turkey antibodies to Mycoplasma meleagridis

A blocking enzyme-linked immunosorbent assay (B-ELISA) was developed to detect antibodies to Mycoplasma meleagridis (MM) in turkey sera. This assay was based on two mouse monoclonal antibodies recognising all MM strains tested but none of seven avian mycoplasmal species tested. Furthermore, their binding to the Tween 20 antigen was inhibited by serum from MM-infected birds. The B-ELISA test format was optimized. The cut-off was determined using a set of sera from MM-free turkeys. This B-ELISA was then compared with a commercial indirect ELISA (I-ELISA). Specificities of the two ELISA tests were not significantly different (100 or 99%, respectively). The sensitivity of B-ELISA was significantly higher than the I-ELISA when I-ELISA suspicious results were considered as negative. Testing sera from experimentally MM-infected animals showed that serum plate agglutination (SPA) test detected positive birds before both ELISA methods. Samples were collected in MM-infected commercial flocks and analyzed by SPA, ELISAs, MM-PCR or culture. Results showed that the sensitivity of the B-ELISA appeared superior to the I-ELISA. Moreover, the ability to detect maternal antibodies makes it a useful tool for eradication or control of MM infections.

Differential serologic response to Mycoplasma ovipneumoniae and Mycoplasma arginini in lambs affected with chronic respiratory disease

An enzyme-linked immunoabsorbent assay (ELISA) was used to evaluate the levels of antibodies to Mycoplasma ovipneumoniae and M. arginini in lambs with chronic respiratory disease. Sera were obtained from lambs in several flocks at various stages of the clinical disease and tested with sodium dodecyl sulfate (SDS)-treated M. ovipneumoniae and M. arginini whole cells and a crude capsular extract of M. ovipneumoniae as the antigens. There were low levels of antibody to M. ovipneumoniae in flocks sampled at the early stages of infection, whereas increased levels of antibody were present in lambs from flocks that had apparently recovered from the clinical disease. Slowly rising titers of circulating antibodies to M. ovipneumoniae were confirmed by sequential bleeding of lambs during the course of the clinical disease. However, antibody levels of M. arginini were more likely to increase earlier in the disease process. There was significant cross-reactivity between the 2 SDS-treated antigens in both the ELISA test and western immunoblotting. In contrast, the crude capsular extract was specific for detecting antibodies to M. ovipneumoniae.

Detection of Mycoplasma hyopneumoniae by air sampling with a nested PCR assay

This article describes the first successful detection of airborne Mycoplasma hyopneumoniae under experimental and field conditions with a new nested PCR assay. Air was sampled with polyethersulfone membranes (pore size, 0.2 micron) mounted in filter holders. Filters were processed by dissolution and direct extraction of DNA for PCR analysis. For the PCR, two nested pairs of oligonucleotide primers were designed by using an M. hyopneumoniae-specific DNA sequence of a repeated gene segment. A nested PCR assay was developed and used to analyze samples collected in eight pig houses where respiratory problems had been common. Air was also sampled from a mycoplasma-free herd. The nested PCR was highly specific and 10(4) times as sensitive as a one-step PCR. Under field conditions, the sampling system was able to detect airborne M. hyopneumoniae on 80% of farms where acute respiratory disease was present. No airborne M. hyopneumoniae was detected on infected farms without acute cases. The chance of successful detection was increased if air was sampled at several locations within a room and a lower air humidity.

A blocking ELISA using a monoclonal antibody for the serological detection of Mycoplasma hyopneumoniae

A blocking ELISA was developed by using a monoclonal antibody (4082-05-344-18) which specifically detected an epitope on the Mycoplasma hyopneumoniae 40 kDa membrane protein without cross-reacting with M flocculare or M hyorhinis. The results obtained with sera from specific pathogen-free pigs inoculated with M flocculare or M hyorhinis confirmed the specificity of the assay. An immunoblotting procedure was used to characterise the antibody response of pigs experimentally infected with M hyopneumoniae. Antibodies to the 40 kDa antigen were detected two weeks after infection and remained as major markers for at least 20 weeks. Cross-reacting antibodies to this antigen were not detected in convalescent sera from piglets infected with M flocculare or M hyorhinis. Sera from experimentally infected pigs were compared by means of the blocking ELISA and an indirect ELISA. The kinetics of ELISA antibodies after experimental inoculation were also studied. The detection of antibody was rather more stable for a longer time with the blocking ELISA than with the indirect ELISA. In an evaluation of more than 1000 sera from the field there was excellent agreement between the two methods.

Rapid purification of antiserum against Mycoplasma hyopneumoniae by an efficient absorption method

A simple and efficient method for the removal of unwanted cross-reactive antibodies has been developed. The antiserum purification method was based on treatment of the antiserum with both sonicated extracts and boiling extracts of the Escherichia coli host cells used in immunoscreening the lambda EMBL3 library. We have demonstrated unambiguously that through this simple treatment, the rabbit anti-Mycoplasma hyopneumoniae antiserum can be effectively purified so that the amount of antibodies cross-reacted with Escherichia coli lysate proteins is drastically reduced. Compared with the traditional absorption methods, which require the chemical coupling of an absorbing agent to an insoluble support, and affinity purification methods, which have harsh denaturing condition, this method should greatly facilitate a successful immunoscreening experiment.

Evaluation of an enzyme-linked immunosorbent assay for the detection of Mycoplasma hyopneumoniae antibody in porcine serum

An enzyme-linked immunosorbent assay (ELISA) for detecting antibody to Mycoplasma hyopneumoniae in porcine serum is described. The results are presented as an ELISA ratio, calculated by dividing the absorbance of the test sample by the mean absorbance of control negative sera. In known infected pigs, the ELISA ratio was highest when the serum concentration applied to the ELISA plate was diluted 1 in 20 in PBS - Tween. Mean ELISA ratios ranged from 1.2 +/- 0.3 for pigs without porcine enzootic pneumonia (PEP) lesions to 5.5 +/- 1.5 for pigs observed with a PEP lesion reacting positively with immunofluorescent histopathology. Pigs observed with typical PEP lesions at slaughter, but not confirmed by immunofluorescent histopathology had a mean ELISA ratio of 4.9 +/- 1.7. The ELISA was highly sensitive (95.6%) and specific (98.8%) when pig sera from commercial piggeries of known M hyopneumoniae infection status were assessed. No cross-reactivity with serum from a pig hyperimmunised with killed M flocculare was detected, and reactivity with serum from another pig hyperimmunised with killed M hyorhinis showed only weak cross-reactivity, which failed to reach the ELISA positive threshold (ELISA ratio 3) for M hyopneumoniae.

Immunological and pathological reactions in piglets experimentally infected with Mycoplasma hyopneumoniae and/or Mycoplasma flocculare

The aim of this work was to examine in vivo whether infection with Mycoplasma hyopneumoniae (M. hyop) and/or Mycoplasma flocculare (M. floc) would interact and influence the severity of enzootic pneumonia in piglets. Specific pathogen-free, hysterectomy-derived piglets were allocated to six groups and experimentally inoculated with M. hyop. and/or M. floc at the age of 2 or 8 weeks. Clinical symptoms, frequency of coughing and temperature measurement were noted daily. Lung lesions were recorded by post-mortem examination and histological observations. The cross-inoculation with both mycoplasmas did not influence the clinical or the pathological picture of the disease. Evolution of specific and crossreacting antibodies was analyzed by ELISA and immunoblotting. Animals inoculated with M. floc did not develop any lesions but showed a weak antibody response 6-8 weeks post-infection (p.i.). No cross-reacting antibodies against M. hyop proteins were detected. In animals inoculated with M. hyop, the first antibody response was detectable 4-5 weeks p.i. and was stronger in piglets infected at the age of 2 weeks than at the age of 8 weeks. Three cross-reacting antibodies against M. floc proteins with molecular weights of 110, 47 and 33 kDa were detected by antibodies to M. hyop. Experimental infections with both mycoplasmas did not show differences in the pattern of species-specific proteins.

A monoclonal blocking ELISA detecting serum antibodies to Mycoplasma hyopneumoniae

A monoclonal blocking enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to Mycoplasma hyopneumoniae in porcine serum has been developed. The monoclonal antibody (mAb) reacts with an M. hyopneumoniae specific epitope on a molecule of approximately 74 kDa. Only sera from M. hyopneumoniae infected pigs were able to block the binding of the mAb although antibodies from M. flocculare infected pigs also recognized a 74 kDa molecule. Sera from experimentally infected pigs as well as field samples were compared by the ELISA and by an indirect hemagglutination assay (IHA). In experimental pigs, the earliest detectable antibody response was found to be almost identical for both assays, but for some of the pigs the time of detection was significantly earlier by blocking ELISA than by IHA. In naturally infected herds more samples were found to be positive by ELISA than by IHA. Furthermore, the results indicate that sera from naturally M. flocculare infected pigs may give rise to cross-reactions in the IHA. The blocking ELISA appears to be a valuable and reproducible tool in the surveillance and serodiagnosis of M. hyopneumoniae infections in pigs.

Evaluation of the ELISA and comparison to the complement fixation test and radial immunodiffusion enzyme assay for detection of antibodies against Mycoplasma hyopneumoniae in swine serum

An enzyme-linked immunosorbent assay (ELISA) was evaluated for detection of antibodies (Ab) against Mycoplasma hyopneumoniae and M. flocculare in sera from swine experimentally infected with these agents. In addition, the ELISA was compared with the complement fixation test (CFT), and radial immunodiffusion enzyme assay (RIDEA) for the demonstration of Ab against M. hyopneumoniae. Twenty two 6-week-old swine from a respiratory disease-free herd were divided into five groups. Two or three pigs from each of the four groups were inoculated, respectively, with M. hyopneumoniae or with M. flocculare while two pigs in each group were contact exposed to the inoculated penmates. A fifth group, consisting of three pigs, served as inoculated controls. Pigs inoculated with M. hyopneumoniae began coughing 13 days post inoculation (PI). Antibodies were first detected 2 weeks PI with the CFT, 3 weeks PI with the ELISA, and 5 weeks PI with the RIDEA. With the ELISA and RIDEA, Ab were still detectable one year PI at a very low level. With the CFT, Ab were not detectable in sera from any swine beyond 5 months PI. At necropsy 1 year PI, no lesions were detected in lungs of any of the animals nor were mycoplasmas detected. M. flocculare inoculated or contact-exposed pigs never evidenced clinical signs. Antibodies against M. flocculare were first detected 5 to 12 weeks PI with CFT, and 6 to 12 weeks PI with the ELISA. Peak optical density (OD) values obtained in the ELISA with M. flocculare Ab were as high as the values obtained with peak M. hyopneumoniae Ab titers. Levels of Ab against M. flocculare were at relatively higher OD at 1 year PI than Ab against M. hyopneumoniae. Sera with high levels of Ab against M. flocculare cross-reacted slightly with M. hyopneumoniae antigen in immunoblotting and ELISA.

Serum antibody response to Mycoplasma hyopneumoniae measured by enzyme-linked immunosorbent assay after experimental and natural infection of pigs

Studies were conducted under experimental and field conditions to determine the effect of infection with M. hyopneumoniae on the immune response in serum as measured by ELISA. Following intratracheal challenge or contact exposure, serologically negative pigs derived from mycoplasma-free piggeries developed an immune response within 10 days. This response continued to rise for a further 50 days. In a field study in a commercial piggery, no animals (0/44) were observed to have M. hyopneumoniae antibodies at day 86 of life. However between day 86 and day 144, 97.7% (42/43) animals sero-converted. These results are discussed in terms of infection spread, particularly in the grower/finisher shed.

Immunoblotting analysis of antibody response in swine experimentally inoculated with Mycoplasma hyopneumoniae

Serological cross-reactivity among swine mycoplasmas, and porcine antibody response to Mycoplasma hyopneumoniae antigens during experimental infection were investigated by enzyme-linked immunosorbent assay (ELISA) and the immunoblotting technique. Mycoplasmas solubilized with Tween 20 were used as antigen. Cross-reactivity between M. hyopneumoniae and M. flocculare was indicated by ELISA and it was demonstrated by immunoblotting, which revealed that the predominant cross-reactive antigens were components of M. hyopneumoniae with molecular weights of 74,000 (74 K) and 53 K. Further, it was indicated that 96 K, 70 K, 46 K and 38 K antigenic components of M. hyopneumoniae and 67 K, 56 K and 23 K antigens of M. flocculare were specific for the respective species. Antibodies to 96 K, 76 K, 70 K, 53 K, 46 K and 38 K antigens were detected in serum from pigs experimentally infected with M. hyopneumoniae. Of these antibodies, those against the 46 K antigen reacted early and were most consistently detected during experimental infection. Therefore, the antibodies against the 46 K antigen of M. hyopneumoniae proved to be excellent markers of mycoplasmal pneumonia of swine.

Antibody response in calves experimentally or naturally exposed to Mycoplasma bovoculi

An antiglobulin-ELISA has been developed to detect antibody activity to Mycoplasma bovoculi in sera, nasal fluids and lacrimal fluids of field and experimentally exposed calves. Low IgG activity with no IgM or IgA was detected in sera of experimental calves. In nasal and lacrimal fluids, IgA appeared as early as the first week following exposure to M. bovoculi and predominated in both of these fluids throughout the 9 wk observation period. Sera from field-exposed animals showed high IgG and IgM activities. The metabolic-inhibition (MI) test was applied to detect growth inhibition of M. bovoculi in those fluids. This property was found only in sera of exposed animals and thus could be used to test for M. bovoculi infection. The ELISA test and the MI test were considered reliable tests for the detection of antibodies to M. bovoculi infection. The implications of finding no growth-inhibiting activity in nasal and lacrimal fluids concurrent with a high IgA activity are discussed.

Detection of antibodies against membrane-glycoproteins of swine erythrocytes after experimental infection with Mycoplasma hyopneumoniae

During enzootic pneumonia of pig, antibodies against membrane glycoproteins of erythrocytes were detected with an enzyme-linked immunosorbent assay (ELISA). These antibodies arise simultaneously with the specific antibodies. They are not identical to cold agglutinins.

A urease-ELISA for the detection of mycoplasma infections in poultry

An ELISA utilising a urease-antibody conjugate specific to chicken IgG was examined as an alternative to the serum agglutination and the haemagglutination inhibition tests in the diagnosis of Mycoplasma gallisepticum and M. synoviae infections in poultry. Use of a urease conjugate allowed the serum reactions to be appraised without the need for expensive photometric equipment. Non-specific binding of conjugate to antigen was eliminated by treatment of antigen coated microplates with 10% foetal calf serum in phosphate buffered saline. Some chicken serums produced non-specific reactions. These reactions were reduced without any loss of test sensitivity by making the initial 1:5 dilution of chicken serum in whole sheep serum rather than diluting buffer. Tests on serums from experimentally infected chickens showed that the urease ELISA was specific, and was as sensitive as the serum agglutination test but more sensitive than the haemagglutination inhibition test.