Comparison of antibody and cell-mediated immune responses of foals and adult horses after vaccination with live Mycobacterium bovis BCG.

This research explores the differences in immune responses between newborn foals, older foals, and adult horses after they receive a live Mycobacterium bovis BCG vaccination. It was found that despite having an immature immune system, newborn foals were capable of mounting significant immune responses to the vaccine, which were sometimes even stronger than those in vaccinated adult horses.

Methods

• The study involved healthy 4-day old foals, 4-month-old foals, and adult horses who were each given a dose of live M. bovis BCG vaccine.
• Equal number of age-matched animals were included as non-vaccinated controls for comparison.
• Vaccine-specific immunoglobulin concentrations as well as expressions of IFN-γ, IL-4, and IL-10 mRNA in the whole blood were measured before and at intervals of 2, 4, 6, and 8 weeks after vaccination.
• Eight weeks post-vaccination, the intensity of delayed type hypersensitivity (DTH) responses were gauged by the increase in double skin thickness after intradermal injection of purified protein derivative.

Results

• All the groups showed a noteworthy rise in vaccine-specific total IgG, IgGa, IgGc, IgG(T), and IgM concentrations. However, only adult horses had discernable IgGb responses.
• Vaccine-specific total IgG and IgGa concentrations were significantly higher in adult horses when compared to 4-day old foals whereas 4-day old foals showed remarkably higher IgGc responses than the other two groups.
• While adult horses exhibited notably higher basal IFN-γ and IL-4 mRNA expression than both groups of foals, vaccination didn’t significantly increase expression of these cytokines across the different age groups.
• Immunized horses revealed significantly higher DTH responses than the age-matched unvaccinated controls.
• DTH responses were significantly greater in both vaccinated groups of foals than vaccinated adult horses.

Conclusions

• Despite having an immature immune system, newborn foals are capable of mounting both antibody and cell-mediated immune responses that are robust against Mycobacterium bovis BCG.
• These findings suggest the potential of using this live vaccine in equine neonates and its implications for understanding how immune response evolves through different stages of growth in horses.