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Species-specific monoclonal antibodies to Escherichia coli-expressed p36 cytosolic protein of Mycoplasma hyopneumoniae.

ABSTRACT: The p36 protein of Mycoplasma hyopneumoniae is a cytosolic protein carrying species-specific antigenic determinants. Based on the genomic sequence of the reference strain ATCC 25934, primers were designed for PCR amplification of the p36-encoding gene (948 bp). These primers were shown to be specific to M. hyopneumoniae since no DNA amplicons could be obtained with other mycoplasma species and pathogenic bacteria that commonly colonize the porcine respiratory tract. The amplified p36 gene was subcloned into the pGEX-4T-1 vector to be expressed in Escherichia coli as a fusion protein with glutathione S-transferase (GST). The GST-p36 recombinant fusion protein was purified by affinity chromatography and cut by thrombin, and the enriched p36 protein was used to immunize female BALB/c mice for the production of anti-p36 monoclonal antibodies (MAbs). The polypeptide specificity of the nine MAbs obtained was confirmed by Western immunoblotting with cell lysates prepared from the homologous strain. Cross-reactivity studies of the anti-p36 MAbs towards two other M. hyopneumoniae reference strains (ATCC 25095 and J strains) and Quebec field strains that had been isolated in culture suggested that these anti-p36 MAbs were directed against a highly conserved epitope, or closely located epitopes, of the p36 protein. No reactivity was demonstrated against other mycoplasma species tested. Clinical signs and lesions suggestive of enzootic pneumonia were reproduced in specific-pathogen-free pigs infected experimentally with a virulent Quebec field strain (IAF-DM9827) of M. hyopneumoniae. The bacteria could be recovered from lung homogenates of pigs that were killed after the 3-week observation period by both PCR and cultivation procedures. Furthermore, the anti-p36 MAbs permitted effective detection by indirect immunofluorescence of M. hyopneumoniae in frozen lung sections from experimentally infected pigs. However, attempts to use the recombinant p36 protein as an antigen in an indirect enzyme-linked immunosorbent assay for the detection of antibodies in sera from convalescent pigs showed no correlation with clinical and pathological findings.

SUBMITTER: Caron J

PROVIDER: S-EPMC95908 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:The P46 and P65 proteins of Mycoplasma hyopneumoniae are two membranous proteins carrying species-specific antigenic determinants. Based on the genomic sequence of the reference strain ATCC 25934, primers were designed for PCR amplification of the genes encoding entire P46 (1,260 bp) and P65 (1,803 bp) and N-terminally truncated P65(c) (1,200 bp). These primers were shown to be specific to M. hyopneumoniae since no DNA amplicons could be obtained with other mycoplasma species that commonly colonize the porcine respiratory tract. Both amplified genes were then cloned into the pGEX-4T-1 vector to be expressed in Escherichia coli cells as recombinant fusion proteins with glutathione S-transferase (GST). Prior to generation of expression constructs, TGA nonsense codons, exceptionally used for tryptophan residues by M. hyopneumoniae, had been converted to TGG codons by PCR-directed mutagenesis. Following induction by IPTG (isopropyl-beta-D-thiogalactopyranoside), both GST-P46 and GST-P65(c) recombinant fusion proteins were recovered by disrupting transformed cells by sonication, purified by affinity chromatography, and then cut with thrombin to release the P46 and P65(c) moieties. The enriched E. coli-expressed P46 and P65c proteins were used to immunize female BALB/c mice for the generation of anti-P46 and anti-P65(c) monoclonal antibodies (MAbs). The polypeptide specificities of MAbs obtained was confirmed by Western blotting with cell lysates prepared from the homologous strain. Cross-reactivity study of the anti-P46 and anti-P65(c) MAbs towards two other M. hyopneumoniae reference strains (ATCC 25095 and J strains) and Quebec field strains that had been isolated in culture, suggested that the MAbs obtained against both membranous proteins were directed against highly conserved species-specific epitopes. No reactivity to other mycoplasma species tested was demonstrated. Clinical signs and lesions suggestive of enzootic pneumonia were reproduced in specific-pathogen-free pigs that had been inoculated intratracheally with a virulent Quebec field strain (IAF-DM9827) of M. hyopneumoniae. Both anti-P46 and anti-P65(c) MAbs permitted effective detection by indirect immunofluorescence and indirect immunoperoxidase assay of M. hyopneumoniae in, respectively, frozen and formalin-fixed, paraffin-embedded lung sections from pigs that were killed after the 6- to 7-week observation period.

Project description:The discovery of small open reading frames (smORFs) encoding for polypeptides (SEPs; <100aa) highlights that the coding capacity of the genomes has been underestimated. Most ORF-finding algorithms have historically set a minimum threshold length of 100 aa. As consequence, some transcripts encoding for SEPs, were erroneously discarded or classified as non-coding RNAs (ncRNAs). With this experiments we try to experimentally assess the existence and complexity of these small proteins. The experimental design includes: After growing each Mycoplasma for 6h at 37°C, cells were washed twice with PBS and lysed with 700 µl of Qiazol buffer. Then, samples were lysed with 700 µl of Qiazol buffer. RNA extractions were performed by using the miRNeasy mini Kit (Qiagen) following the instructions of the manufacturer. Libraries for RNA-seq were prepared following directional RNA-seq library preparation and sequencing. Briefly, 1 µg of total RNA was fragmented to ~100-150 nt using NEB Next Magnesium RNA Fragmentation Module (ref. E6150S, NEB). Treatments with Antarctic phosphatase (ref. M0289S, NEB) and PNK (ref. M0201S, NEB) were performed in order to make the 5’ and 3’ ends of the RNA available for adapter ligation. Samples were further processed using the TruSeq small RNA Sample Prep Kit (ref. RS-200-0012, Illumina) according to the manufacturer's protocol. In summary, 3’ adapters and subsequently 5’ adapters were ligated to the RNA. cDNA was synthesized using reverse transcriptase (SuperScript II, ref. 18064-014, Invitrogen) and a specific primer (RNA RT Primer) complementary to the 3’ RNA adapter. cDNA was further amplified by PCR using indexed adapters supplied in the kit. Finally, size selection of the libraries was performed using 6% Novex® TBE Gels (ref. EC6265BOX, Life Technologies). Fragments with insert sizes of 100 to 130 bp were cut from the gel, and cDNA was precipitated and eluted in 10 µl of elution buffer. Double-stranded templates were cluster amplified and sequenced on an Illumina HiSeq 2000.

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Species-specific monoclonal antibodies to Escherichia coli-expressed p36 cytosolic protein of Mycoplasma hyopneumoniae.

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