Immunoblot assays using recombinant antigens for the detection of Mycoplasma hyopneumoniae antibodies

Long simple sequence repeats in host-adapted pathogens localize near genes encoding antigens, housekeeping genes, and pseudogenes

Simple sequence repeats (SSRs) in DNA sequences are tandem iterations of a single nucleotide or a short oligonucleotide. SSRs are subject to slipped-strand mutations and a common source of phase variation in bacteria and antigenic variation in pathogens. Significantly long SSRs are generally rare in prokaryotic genomes, and long SSRs composed of iterations of mono-, di-, tri-, and tetranucleotides are mostly restricted to host-adapted pathogens. We present new results concerning associations between long SSRs and genes related to different cellular functions in genomes of host-adapted pathogens. We found that in the majority of the analyzed genomes, at least some of the genes associated with SSRs encode potential antigens, which is expected if the primary function of SSRs is their contribution to antigenic variation. However, we also found a number of long SSRs associated with housekeeping genes, including rRNA and tRNA genes, genes encoding ribosomal proteins, amino acyl-tRNA synthetases, chaperones, and important metabolic enzymes. Many of these genes are probably essential and it is unlikely that they are phase-variable. Few statistically significant associations between SSRs and gene functional classifications were detected, suggesting that most long SSRs are not related to a particular cellular function or process. Long SSRs in Mycobacterium leprae are mostly associated with pseudogenes and may be contributing to gene loss following the adaptation to an obligate pathogenic lifestyle. We speculate that LSSRs may have played a similar role in genome reduction of other host-adapted pathogens.

Proteomic survey of the pathogenic Mycoplasma hyopneumoniae strain 7448 and identification of novel post-translationally modified and antigenic proteins

Mycoplasma hyopneumoniae is an important pathogen for pigs, being the causative agent of enzootic pneumonia. Recently, the genome sequences of three strains, J, 7448 and 232 have been reported. Here, we describe the results of a proteomic analysis, based on two-dimensional gel electrophoresis of soluble protein extracts, immunoblot and mass spectrometry, which was carried out aiming the identification of gene products and antigenic proteins from the M. hyopneumoniae pathogenic strain 7448. A preliminary M. hyopneumoniae proteome map in two pH ranges (3-10 and 4-7) was produced. A total of 31 different coding DNA sequences (CDSs), including three hypothetical ones, were experimentally verified with the identification of the corresponding protein products by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. According to the Clusters of Orthologous Groups (COG) functional classification, the identified proteins were assigned to the groups of metabolism (13), cellular processes (5) and information and storage processing (4). Nine of the identified proteins were not classifiable by COG, including some related to cytoadherence and possibly involved in pathogenicity. Moreover, at least five highly antigenic proteins of M. hyopneumoniae were identified by immunoblots, including four novel ones (a heat shock protein 70, an elongation factor Tu, a pyruvate dehydrogenase E1-beta subunit and the P76 membrane protein). The now available proteome map is expected to serve as a reference for comparative analyses between M. hyopneumoniae pathogenic and non-pathogenic strains, and for methabolic studies based on cells cultured under modified conditions.

Comparison of two swine Mycoplasma hyopneumoniae enzyme-linked immunosorbent assays for detection of antibodies from vaccinated pigs and field serum samples

Mycoplasma hyopneumoniae (Mhyo) causes mycoplasmal pneumonia, an economically important disease of swine. Serodiagnosis of Mhyo is based on the current available commercial enzyme immunoassays for detection of swine antibodies against Mhyo, which are the indirect enzyme-linked immunosorbent assay (ELISA) and the blocking ELISA (B-ELISA). Because of the limited information available for these ELISAs, these 2 assays were compared by testing 347 serum samples collected from vaccinated pigs at 0, 13, 28, 43, and 62 days postimmunization (DPI), 50 samples from nonvaccinated pigs, and 1,013 field serum samples. The results of comparison study showed that the specificity for both ELISAs was 99.2% generated from 139 non-vaccinated negative samples. The sensitivities for indirect ELISA generated from samples collected from animals that received the vaccine at DPI 13, 28, 43, and 62 were 0%, 95.7%, 88.4%, and 92.6%, respectively, whereas the sensitivities for B-ELISA were 0%, 98%, 100%, and 97%, respectively. The overall agreement of 96.7% and 80.3% was generated between 2 ELISAs from negative and vaccinated pigs and from field samples, respectively.