Molecular assay for detecting MS-H vaccine strain and immune response mechanisms in chickens receiving one or two doses of live MS-H vaccine

ABSTRACT

The MS-H vaccine, containing a live strain of Mycoplasma synoviae, is a feasible option for controlling M. synoviae infection in poultry flocks. A comprehensive understanding of vaccinated chickens, including strain differentiation and immune response mechanisms, is required to optimize vaccination strategy. This study aimed to verify the PCR-RFLP molecular assay as a convenient technique for detecting the MS-H vaccine strain and to characterize the immune response mechanisms in experimental layer-type chickens receiving one of three different vaccination programmes; a single dose at either 9 or 12 weeks of age or two doses at both 9 and 12 weeks of age. The PCR-RFLP assay, using restriction enzyme TasI to digest vlhA gene-targeted PCR amplicons, was performed to evaluate vaccine administration by detecting the MS-H vaccine strain in vaccinated chickens and differentiating it from non-vaccine strains such as WVU1853 reference strain and Thai M. synoviae field strains. Results demonstrated that vaccination in layer-type chickens, whether as one or two doses, stimulated immune response mechanisms with no significant advantages of two administrations over a single administration. Serological responses in vaccinated chickens, examined by RPA test and ELISA, were initially detected at 2 weeks post-vaccination, continuously increased, and then remained at the baseline levels from 6 to 9 weeks post-vaccination. Cellular immune responses against both homologous and heterologous antigens, examined by the MTS tetrazolium assay, were similar in the early period post-vaccination, whereas cellular immune response against the homologous MS-H antigen was improved in the late period post-vaccination.

KEYWORDS:

• Mycoplasma synoviae
• chicken
• vaccination
• cellular immune response
• serological response
• molecular assay

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was supported by the Thailand Research Fund through the Royal Golden Jubilee Ph.D. [grant number PhD/0030/2561] to K. Limpavithayakul and S. Pakpinyo; the Ratchadaphiseksomphot Fund Chulalongkorn University and the 90th Anniversary of Chulalongkorn University Fund (Ratchadaphiseksomphot Endowment Fund) under Grant Batch 46 Round 2/2020 Academic Year 2019.