Development and evaluation of enzyme-linked immunosorbent assay based on recombinant inorganic pyrophosphatase gene antigen for the detection of Mycoplasma suis antibodies

Mycoplasma suis Alpha-Enolase Subunit Vaccine Induces an Immune Response in Experimental Animals

Recombinant protein technology has emerged as an excellent option for vaccine development. However, prior to our study, the immune induction ability of recombinant Mycoplasma suis alpha-enolase (rMseno) in animals remained unclear. The purpose of this study was to develop a rMseno protein subunit vaccine and to determine its ability to elicit an immunological response. To accomplish this, we cloned the gene into pET-15b, expressed it in BL21 cells, and purified it. Following the establishment of immunity, the immunogenicity and potential for protection of rMseno were evaluated in mice and piglets. The results demonstrate that anti-M. suis serum recognized the pure rMseno protein in both mice and piglets as evidenced by high levels of specific anti-rMseno antibodies, significantly increased levels of IFN-γ and IL-4 cytokines, and significantly increased T lymphocyte proliferation index. Piglets also had significantly increased levels of specific IgG₁, IgG_2a, CD4⁺, and CD8⁺ cells. The rMseno findings demonstrated a robust immunological response in mice and piglets, affording partial clinical protective efficacy in piglets.

Detection of Mycoplasma suis in pre-suckling piglets indicates a vertical transmission

Background

Transmission of Mycoplasma (M.) suis mainly occurs via iatrogenic or zootechnical manipulations or due to ranking fights. Other transmission routes including ingestion of secretes/excretes; blood-sucking arthropods and intra-uterine transmission have thought to play an epidemiological role without being experimentally proven. To investigate a vertical transmission of M. suis under field conditions blood samples from pre-suckling piglets and their corresponding dam were examined for M. suis by quantitative polymerase chain reaction (qPCR) in 21 farms in Southern Germany.

Results

A total of 14.35% of the 474 blood samples from pre-suckling piglets reacted qPCR positive. Additionally, M. suis was detected in 65 (31.25%) of the 208 sows at farrowing. On farm level, 16 (76.2%) of the 21 farms had at least one M. suis positive animal. M. suis positive farms had an average of 0.41 more stillborn piglets per litter than M. suis negative farms (p = 0.007).

Conclusion

The present study provides further insights into M. suis infection dynamics as it is the first detection of M. suis in piglets immediately after birth prior to colostrum intake and the first large scale investigation of M. suis in sows at farrowing.

Seroprevalence and risk factors of Mycoplasma suis infection in pig farms in central China

Mycoplasma suis, the causative agent of porcine infectious anemia, causes large economic losses to the swine industry worldwide. A questionnaire-based survey was conducted in 69 pig farms in Hubei Province, China, from November 2011 to August 2013 to ascertain the prevalence and associated risk factors of M. suis. Four thousand and four blood samples from pigs of all the age groups were tested for M. suis antibodies using the established rMSG1-ELISA assay. Among these 4004 samples, 1615 blood samples from multiparous sows were examined to identify the association between seroprevalence and different seasons. Information on risk factors collected from farmers or attending veterinarians was recorded on a pre-designed questionnaire. The overall test seroprevalence of M. suis infection at the animal level was 31.9% (1277/4004; 95% CI: 30.5%, 33.4%), whereas at the farm level, this value was 95.65% (66/69; 95% CI: 87.8%, 99.1%). The seroprevalence of M. suis was higher in replacement gilts (40.6%; 95% CI: 35.1%, 46.3%), multiparous sows (48.2%; 95% CI: 45.8%, 50.7%) and boars (44.4%; 95% CI: 34.5%, 54.8%), as compared to piglets (13.0%; 95% CI: 9.4%, 17.3%), weaned-piglets (10.8%; 95% CI: 8.9%, 13.0%), and growing-finishing pigs (25.0%; 95% CI: 22.0%, 28.3%). In terms of seasons, the prevalence of M. suis in pigs was significantly higher in summer (65.3%; 95% CI: 61.0%, 69.5%) and autumn (65.0%; 95% CI: 59.0%, 70.6%) compared to spring (30.1%; 95% CI: 26.0%, 34.4%) and winter (36.4%; 95% CI: 31.4%, 41.5%). Farm-level risk factors were identified by multivariable logistic regression analysis. The associated factors retained in the final multivariable logistic regression model were drug treatment, presence of mosquitoes and flies, and frequency of disinfection. Drug treatment (OR=0.24; 95% CI: 0.07, 0.88; P=0.031) and frequency of disinfection (OR=0.23; 95% CI: 0.06, 0.90; P=0.035) were protective factors, and the presence of mosquitoes and flies (OR=5.994; 95% CI: 1.56, 23.00; P=0.009) was a risk factor for M. suis infection on farms. The results of the present study provide the first insight into the impact of associated determinants on M. suis infection in central China.

Identification of Mycoplasma suis antigens and development of a multiplex microbead immunoassay

The aims of the current study were to identify Mycoplasma suis antigens and develop a multiplex microbead immunoassay (MIA). A M. suis-expression library was screened for immunogens using sera from infected pigs. Based on bioinformatics, putative antigens were identified within positive inserts; gene fragments were expressed and purified as polyhistidine fusion proteins, and immunoreactivity was confirmed by Western blot. Selected antigens were used to develop a MIA. Sera from noninfected and infected pigs were used to set the median fluorescent intensity (MFI) cutoffs and as positive controls, respectively. Assay specificity was tested using sera from pigs seropositive for other pathogens (2 different pigs seropositive for each pathogen). Samples from 51 field pigs and 2 pigs during the course of acute (pig 1) and chronic (pig 2) infections were tested using MIA, indirect hemagglutination assay (IHA), and quantitative polymerase chain reaction (qPCR). Sixteen reactive plaques (52 genes) were detected. A heat-shock protein (GrpE), a nicotinamide adenine dinucleotide-dependent glyceraldehyde 3-phosphate dehydrogenase (GAPN), and 4 proteins from paralogous gene families (PGFs) were identified as antigens by Western blot. While GrpE, GAPN, and 1 PGF protein were strong antigens, the others were not suitable as MIA targets. A MIA using GrpE, GAPN, and the strongly reactive PGF protein was developed. Cross-reactivity with sera from pigs infected with Mycoplasma hyopneumoniae, Porcine circovirus-2, Porcine parvovirus, Porcine reproductive and respiratory syndrome virus, and Porcine respiratory coronavirus with this MIA was not observed. Pig 2 was consistently positive by MIA and qPCR, whereas pig 1, initially negative, seroconverted before becoming qPCR positive. Only 2 samples (from pig 1) were IHA positive. Five (9.8%) field samples were qPCR positive and 40 (78.43%) were positive for all 3 MIA antigens; however, all were IHA negative. In summary, the MIA is specific and more sensitive than qPCR and IHA, providing simultaneous evaluation of antibody response to M. suis antigens.

Neospora caninum surface antigen (p40) is a potential diagnostic marker for cattle neosporosis

Neospora caninum is an intracellular protozoan that infects domestic and wild canids as well as many warm-blooded animals as shown by the isolation of viable parasites. The effectiveness of diagnostic tests for detecting specific antibodies against N. caninum is hampered by potential cross-reaction with other Coccidia. So, there is currently an urgent need for a sensitive and specific diagnostic assay for detecting N. caninum in animals. The N. caninum 40-kD surface antigen (p40), similar to NcSAG1 and NcSRS2, was shown to belong to surface antigen super family and thus represents an excellent marker for the diagnosis of neosporosis. In order to test the hypothesis, recombinant Ncp40 (rNcp40) was expressed in Escherichia coli, and an indirect ELISA test was developed using recombinant NCp40 antigen for N. caninum serodiagnosis. The antigen used in this study did not have cross-reactivity with anti-Toxoplasma gondii serum. Anti-p40 antibodies were detected by ELISA in the sera of Yellow cattle and were compared with (IFAT). Optimal sensitivity and specificity (98.2 and 98.6 %) were identified by IFAT. Additionally, 37 positive sera of T. gondii were detected and there was no significant difference with the negative serum of N. caninum. The rNcp40 ELISA developed here provides a specific and sensitive assay for detecting neosporosis in cattle.