Preliminary comparative analysis of the genomes of selected field reisolates of the Mycoplasma synoviae vaccine strain MS-H reveals both stable and unstable mutations after passage in vivo

Abstract

Background Genomic comparison of Mycoplasma synoviae vaccine strain MS-H and the MS-H parental strain 86,079/7NS established a preliminary profile of genes related to attenuation of MS-H. In this study we aimed to identify the stability of mutations found in MS-H after passage in experimental or field chickens, and to evaluate if any reverse mutation may be associated with changes in characteristics of MS-H in vitro or in vivo. Results Whole genome sequence analysis of 5 selected MS-H field reisolates revealed that out of 32 mutations reported previously in MS-H, 28 remained stable, while four found to be reversible to the wild-type. Each isolate possessed mutations in one to three of the genes obg, oppF1 and gap and/or a non-coding region. Examination of the 4 reversible mutations by protein modeling predicted that only two of them (in obg and oppF1 genes) could potentially restore the function of the respective protein to that of the wild-type. Conclusions These results suggest that the majority of the MS-H mutations are stable after passage in vaccinated chickens. Characterisation of stable mutations found in MS-H could be utilised to develop rapid diagnostic techniques for differentiation of vaccine from field strains or ts- MS-H reisolates.

Genomic Diversity of a Globally Used, Live Attenuated Mycoplasma Vaccine

“…Therefore, the GAPDH Lys306Arg variant is proposed to provide a significant advantage in cell adhesion for those MS-H reisolates, as well as for the wild-type 7NS, and thus potentially confers a superior pathogenicity, compared to MS-H. This is consistent with the report by Kordafshari et al (2020) that this mutation was likely to influence the systemic antibody responses raised by the host against MS-H ( 24 ). The absence of any variation in the GAPDH-1150 suggests that this copy could still be useful in providing the enzymatic activity of the GAPDH tetramer, despite its difference from the wild-type version.…”

“…In this study, the stability of a live attenuated mycoplasma vaccine was assessed after in vitro and in vivo passages under different circumstances to complement previous findings regarding the stability of the MS-H genome in a limited number of field reisolates ( 24 ).…”

“…Most of the variations found in the oppF region of the MS-H reisolates resulted in a frameshift which removed a stop codon. The T insertion at position 467 of this coding region is a back mutation to the wild-type genotype in the 7NS genome and has been shown to result in the full-length expression of the OppF protein in vitro ( 24 ). Therefore, it appears that while the truncated version of OppF in MS-H does not affect the peptide uptake of MS-H under in vitro conditions, it is unlikely to be sufficient under the in vivo conditions for this purpose.…”

“…To explore the genetic bases of virulence attenuation and temperature sensitivity in MS-H, the complete genome sequence of this strain (GenBank accession number CP021129 ) was compared to that of its parent 7NS (GenBank accession number CP029258.1 ), which revealed 32 single nucleotide polymorphisms (SNPs) ( 23 ). A genome analysis of M. synoviae isolates that were recovered from vaccinated flocks identified that only a few of the mutations in the MS-H strain have reverted to the parent strain sequence ( 24 ). Studying the genomic stability of the live MS-H strain and the dynamics of the population after vaccination will improve our understanding on whether there are any clues regarding factors that could potentially influence the health of vaccinated or in-contact, naive birds.…”

Comparative Genomics of Mycoplasma synoviae and New Targets for Molecular Diagnostics

“…Comparative genome analysis of the vaccine strain and its wildtype parent strain can be used to find possible pathogenesisrelated genes. For example, the obg gene, which may affect the temperature sensitivity of the MS-H strain, as well as the possible virulence-related gene oppF, were found via comparative genome analysis of the vaccine strain MS-H and its parent strain 86079/7NS (8)(9)(10). However, a comparative genomic analysis of M. synoviae and other major Mycoplasma has not yet been systematically conducted and is the focus of this study.…”