Characteristics of maternal antibodies transferred to foals raised through maternal equine rotavirus A vaccination.

Overview

• This research investigates the transmission, durability, and cross-reactivity of maternal antibodies against equine rotavirus A (ERVA) genotypes in foals born to vaccinated mares.
• The study specifically evaluates how vaccination of mares with a G3P[12] genotype vaccine affects neutralizing antibody levels in mares and their foals, and whether these antibodies also react with a different ERVA genotype, G14P[12].

Background

• Equine Rotavirus A (ERVA) is a virus that causes diarrhea in foals, primarily involving genotypes G3P[12] and G14P[12].
• Vaccination of mares with a monovalent killed vaccine targeting the G3P[12] genotype has been employed to reduce neonatal infection rates.
• Maternally derived antibodies (from the mare to the foal) are critical in providing early protection to the newborn foal until its immune system matures.

Research Aim

• To measure the levels (dynamics) and duration (longevity) of maternally derived neutralizing antibodies (NAbs) against the ERVA G3P[12] genotype in foals originating from vaccinated mares.
• To assess whether these maternally derived antibodies also show cross-reactivity with the G14P[12] ERVA genotype.

Methods

• Serum samples were collected from 50 pairs of mares and their foals:
• Mare samples were collected prior to each vaccination and up to 6 months after foaling.
• Foal samples were collected up to 7 months of age.
• Virus-neutralization assays were performed using both G3P[12] and G14P[12] virus strains to measure antibody titers.
• Foal samples were taken both before and after nursing to determine antibody transfer through colostrum.

Key Findings

• Vaccination of mares significantly increased their serum neutralizing antibody titers against G3P[12].
• Foals had no detectable neutralizing antibodies at birth before nursing, indicating that in utero transfer of these antibodies is negligible or absent.
• Post-nursing foal serum contained significant levels of neutralizing antibodies, showing successful transfer through the mare’s colostrum.
• There was variability in how effectively mares transferred neutralizing antibodies to their foals.
• Evidence of cross-reactivity was found: antibodies produced against G3P[12] in mares also had some neutralizing capacity against the G14P[12] genotype.
• However, the cross-reactive NAb titers against G14P[12] were 2 to 4 times lower compared to those against G3P[12] in colostrum, milk, and serum of both mares and foals.
• Neutralizing antibody levels against both genotypes steadily declined in the foals’ serum, reaching the lowest point at around 4 months after birth.

Implications

• Maternal vaccination with the G3P[12] ERVA vaccine effectively boosts colostral antibody levels, providing passive immunity to foals during their early life.
• Passive immunity is mainly acquired through nursing rather than transplacental antibody transfer in horses.
• Cross-reactivity between ERVA genotypes suggests that the vaccine may offer partial protection against multiple virus strains, though protection against G14P[12] is weaker.
• The decline in foal serum antibody levels over four months post-birth indicates a critical period when foals become more susceptible to ERVA infections as maternal antibodies wane.
• Results support ongoing vaccination of mares to ensure high antibody levels in colostrum and highlight the necessity to understand cross-protection when considering vaccine composition or booster strategies.

Summary

• This study provides detailed insight into the transfer and duration of protective antibodies from vaccinated mares to their foals and suggests that maternal equine rotavirus vaccination is beneficial for early foal immunity.
• The knowledge of cross-reactivity and antibody decline informs veterinary practices on timing and targeting of vaccination to minimize foal rotavirus infections.