Protein and Antigenic Variability among Mycoplasma hyopneumoniae Strains by SDS-PAGE and Immunoblot

Effect of multiple vaccinations on transmission and degree of Mycoplasma hyopneumoniae infection in gilts

Mycoplasma hyopneumoniae (M. hyopneumoniae) infections continue to result in significant respiratory challenges in the swine industry worldwide. Vaccination for M. hyopneumoniae is commonly utilized, as reduction in bacterial loads and clinical severity in vaccinated pigs have been shown. However, the effect of M. hyopneumoniae vaccination on transmission across different pig populations has been minimally investigated. The aim of this pilot study was to evaluate the effect of multiple vaccinations on M. hyopneumoniae infection, transmission, and genetic variability in infected and susceptible gilt populations. Thirty-two naïve gilts were allocated to four treatment groups: (1) Vaccinated seeder (VS); (2) Non-vaccinated seeder (NVS); (3) Vaccinated contact (VC); and (4) Non-vaccinated contact (NVC). At 5, 7, and 9 weeks of age, all gilts selected to be vaccinated received a commercial M. hyopneumoniae bacterin for a total of 3 doses. At 11 weeks of age, VS and NVS gilts were inoculated with M. hyopneumoniae to become seeders. At 28 days post-inoculation (dpi), VS and NVS gilts were individually relocated to clean experimental rooms, where they were placed in contact with one age-matched VC or NVC gilt (1:1 ratio) for 14 days. Blood and tracheal samples, bronchial swabs, and lung lesions were collected and/or evaluated for M. hyopneumoniae infection. In this study, a three-dose vaccination strategy against M. hyopneumoniae significantly reduced bacterial load in seeder gilts. Furthermore, a numerical reduction in M. hyopneumoniae lung lesions at 28 dpi was observed in VS gilts. All VC gilts in the VS:VC treatment group pairing remained M. hyopneumoniae negative, compared to other groups in which 1-2 transmission events occurred per treatment group. Results from this investigation provide insight on the potential impact of multiple vaccinations on reducing M. hyopneumoniae transmission and infection. Further research encompassing vaccinations of gilt groups in field settings is necessary to validate findings.

Mycoplasma hyopneumoniae variability: Current trends and proposed terminology for genomic classification

Mycoplasma hyopneumoniae (M. hyopneumoniae) is the aetiologic agent of enzootic pneumonia in swine, a prevalent chronic respiratory disease worldwide. Mycoplasma hyopneumoniae is a small, self-replicating microorganism that possesses several characteristics allowing for limited biosynthetic abilities, resulting in the fastidious, host-specific growth and unique pathogenic properties of this microorganism. Variation across several isolates of M. hyopneumoniae has been described at antigenic, proteomic, transcriptomic, pathogenic and genomic levels. The microorganism possesses a minimal number of genes that regulate the transcription process. Post-translational modifications (PTM) occur frequently in a wide range of functional proteins. The PTM by which M. hyopneumoniae regulates its surface topography could play key roles in cell adhesion, evasion and/or modulation of the host immune system. The clinical outcome of M. hyopneumoniae infections is determined by different factors, such as housing conditions, management practices, co-infections and also by virulence differences among M. hyopneumoniae isolates. Factors contributing to adherence and colonization as well as the capacity to modulate inflammatory and immune responses might be crucial. Different components of the cell membrane (i.e. proteins, glycoproteins and lipoproteins) may serve as adhesins and/or be toxic for the respiratory tract cells. Mechanisms leading to virulence are complex and more research is needed to identify markers for virulence. The utilization of typing methods and complete or partial-gene sequencing for M. hyopneumoniae characterization has increased in diagnostic laboratories as control and elimination strategies for this microorganism are attempted worldwide. A commonly employed molecular typing method for M. hyopneumoniae is Multiple-Locus Variable number tandem repeat Analysis (MLVA). The agreement of a shared terminology and classification for the various techniques, specifically MLVA, has not been described, which makes inferences across the literature unsuitable. Therefore, molecular trends for M. hyopneumoniae have been outlined and a common terminology and classification based on Variable Number Tandem Repeats (VNTR) types has been proposed.

Mycoplasma agassizii strain variation and distinct host antibody responses explain differences between enzyme-linked immunosorbent assays and Western blot assays

The precarious status of desert (Gopherus agassizii) and gopher (G. polyphemus) tortoises has resulted in conservation efforts that now include health assessment as an important component of management decision-making. Mycoplasmal upper respiratory tract disease (URTD) is one of very few diseases in chelonians for which comprehensive and rigorously validated diagnostic tests exist. In this study, serum samples obtained from eight Gopherus tortoises documented at necropsy to (i) be enzyme-linked immunosorbent assay (ELISA) seropositive using the PS6 antigen, (ii) be infected with Mycoplasma agassizii as indicated by direct isolation of the pathogen from the respiratory surfaces, and (iii) have histological lesions of mycoplasmal URTD were used to evaluate four distinct clinical isolates of M. agassizii as antigens for ELISA and Western blot analyses. Each animal sample reacted in the Western blot with its homologous M. agassizii strain, but recognition of heterologous M. agassizii strains was variable. Further, individual animals varied significantly with respect to the specific proteins recognized by the humoral immune response. An additional 114 Gopherus serum samples were evaluated using ELISA antigens prepared from the four distinct M. agassizii strains; A₄₀₅ values were significantly correlated (r² goodness of fit range, 0.708 to 0.771; P < 0.0001) for all antigens tested. The results confirm that strain variation is responsible for the observed differences between Western blot binding patterns. Thus, reliance on a single M. agassizii strain as an antigen in Western blot assays may provide false-negative results. This could have adverse consequences for the well-being of these environmentally sensitive hosts if false-negative animals were relocated to sites consisting of true-negative populations.

Current perspectives on the diagnosis and epidemiology of Mycoplasma hyopneumoniae infection

Mycoplasma hyopneumoniae is the principal aetiological agent of enzootic pneumonia (EP), a chronic respiratory disease that affects mainly finishing pigs. Although major efforts to control M. hyopneumoniae infection and its detrimental effects have been made, significant economic losses in pig production worldwide due to EP continue. M. hyopneumoniae is typically introduced into pig herds by the purchase of subclinically infected animals or, less frequently, through airborne transmission over short distances. Once in the herd, M. hyopneumoniae may be transmitted by direct contact from infected sows to their offspring or between pen mates.

The ‘gold standard’ technique used to diagnose M. hyopneumoniae infection, bacteriological culture, is laborious and is seldom used routinely. Enzyme-linked immunosorbent assay and polymerase chain reaction detection methods, in addition to post-mortem inspection in the form of abattoir surveillance or field necropsy, are the techniques most frequently used to investigate the potential involvement of M. hyopneumoniae in porcine respiratory disease. Such techniques have been used to monitor the incidence of M. hyopneumoniae infection in herds both clinically and subclinically affected by EP, in vaccinated and non-vaccinated herds and under different production and management conditions. Differences in the clinical course of EP at farm level and in the efficacy of M. hyopneumoniae vaccination suggest that the transmission and virulence characteristics of different field isolates of M. hyopneumoniae may vary. This paper reviews the current state of knowledge of the epidemiology of M. hyopneumoniae infection including its transmission, infection and seroconversion dynamics and also compares the various epidemiological tools used to monitor EP.

Protein variability among Mycoplasma hyopneumoniae isolates

Sodium-dodecyl-sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was used to study the protein variability of Mycoplasma hyopneumoniae isolates. Fifty-six M. hyopneumoniae isolates from 6 different countries and 37 different herds were used. From eight herds, more than one isolate was available. All SDS-PAGE patterns of isolates originating from different herds were clearly divergent. Intra-species protein variability was quantified using the reference strain J and seven field strains all obtained from different herds and classified according to virulence. Between the field strains, a variability of 25% was found, while the culture-adapted strain J was clearly divergent and showed 30% variability with the field strains. No clustering according to virulence was obtained, but a protein band of about 181kDa was present in the two highly virulent isolates whereas this protein band was absent in the moderately and low virulent isolates. Protein patterns of isolates derived from different animals from the same herd, were identical or differed in only a few protein bands. This study clearly indicates that, in agreement with previous studies on genomic diversity of M. hyopneumoniae isolates, proteomic variability within the species is high. Our study did not find clear evidence that more than one M. hyopneumoniae isolate circulates within a herd at a specific time point. The minor differences found between M. hyopneumoniae isolates from the same herd might reflect the organism's ability to alter its proteomic expression profile under field conditions.

Identification and immunological characterization of conserved Mycoplasma hyopneumoniae lipoproteins Mhp378 and Mhp651

Mycoplasma hyopneumoniae, the etiological agent of swine enzootic pneumonia, is an important pathogen in the swine industry worldwide. Investigations on pathogenicity mechanisms as well as current serological detection methods and the development of new recombinant subunit vaccines are hampered by the lack of known and well characterized, species-specific M. hyopneumoniae antigens. As a first step to solve these problems membrane and membrane-associated proteins were enriched from M. hyopneumoniae cells by Triton X-114 fractionation and further analyzed by 2D gel electrophoresis and Western blot analyses using convalescent sera. Two previously unknown immunogenic proteins were identified by quadrupole time-of-flight mass spectrometry and database analyses as the conserved putative lipoproteins, Mhp378 and Mhp651. Both proteins were expressed as recombinant GST fusion proteins and reacted with sera from convalescent pigs. Coated as solid-phase antigen, Mhp651 showed a distinct cross-reaction only with Mycoplasma flocculare specific rabbit hyperimmune serum, whereas Mhp378 was only recognized by the positive control serum directed against M. hyopneumoniae, thereby indicating its species specificity.

A recombinant chimera composed of R1 repeat region of Mycoplasma hyopneumoniae P97 adhesin with Escherichia coli heat-labile enterotoxin B subunit elicits immune response in mice

Swine mycoplasmal pneumonia (SMP), caused by fastidious bacterium Mycoplasma hyopneumoniae, is the most important respiratory disease in swine breeding. The commonly used vaccines to control this disease consist of inactivated whole cells (bacterins), whose production cost is high and the efficiency is limited. The objective of this study was to develop and to evaluate in BALB/c mice a recombinant subunit vaccine (rLTBR1) containing the R1 region of P97 adhesin of M. hyopneumoniae (R1) fused to the B subunit of the heat-labile enterotoxin of Escherichia coli (LTB). rLTBR1 formed functional oligomers that presented high affinity to GM1 ganglioside. Mice inoculated with rLTBR1 by intranasal (IN) or intramuscular (IM) route produced high levels of anti-R1 systemic and mucosal antibodies (IgA), which recognized the native P97. On the other hand, mice inoculated with the inactivated whole cell vaccine did not produce anti-R1 antibodies. The administration route influenced the modulation of the immune response by LTB, showing that IM rLTBR1 induced Th2-biased immune responses and IN rLTBR1 induced Th1-biased immune responses. rLTBR1 administrated by IN route also induced IFN-gamma secretion by lymphocytes. rLTBR1 may constitute a new strategy for preventing infection by M. hyopneumoniae and may have potential for developing vaccines against other infectious diseases as well.

Variable number of tandem aminoacid repeats in adhesion-related CDS products in Mycoplasma hyopneumoniae strains

The Mycoplasma hyopneumoniae genome contains at least 22 regions with a variable number of tandem nucleotide repeats (VNTRs) within coding DNA sequences (CDSs). In this work, the VNTR-containing CDSs were analysed in order to evaluate their degree of variation, possible correlations with antigenic properties, and their potential to be used as a basis for a strain typing PCR assay. We have analysed the VNTRs in five M. hyopneumoniae strains (J, 7448, 7422, PMS, and 232), based on published genomic sequences and on amplified and sequenced DNA segments. These VNTRs are distributed among 12 genes, most of which encode putative surface proteins, including known adhesins. The number of repeat units in any of the VNTRs is highly variable among the analysed strains, but they are, without exception, translationally in frame, and, therefore, code for a variable number of aminoacid repeats (VNTARs). These VNTARs determine putative structural, physicochemical and antigenic variations in the corresponding proteins, with potential implications for aspects associated to M. hyopneumoniae pathogenicity, such as cell adhesion and interactions with the host immune system. Considering that the characterized VNTARs are relatively stable, at least in vitro, and their sizes are strain-specific, we have developed a VNTR-based PCR assay for M. hyopneumoniae strain identification, useful for enzootic pneumonia (EP) diagnosis, strain typing, and distinction of circulating field isolates from vaccine strains in animals vaccinated against EP.