Administration of commercial Rhodococcus equi specific hyperimmune plasma results in variable amounts of IgG against pathogenic bacteria in foals.

The research investigates the efficiency and variability of antibody response against Rhodococcus equi, a common cause of pneumonia in foals, using commerical hyperimmune plasma (HIP). The study finds that while HIP significantly increases VapA-specific IgGs (antibodies), there is significant variation in results, possibly explaining its controversial effectiveness.

Objective & Methodology

• The study had two main objectives: to examine the antibodies (VapA-specific IgG and its subclasses) in commercial R equi HIP and to assess these antibodies in foals serum after receiving commercial R equi HIP.
• Three different batches of four commercial R equi HIP were tested.
• An ELISA (enzyme-linked immunosorbent assay) was used to evaluate VapA-specific IgG and its subclasses in all the samples.
• Serum was also collected from newborn foals, both those that had received the commercial R equi HIP (n=97) and those who hadn’t (n=70), and from each of their mothers as well.

Key Findings

• Administering HIP resulted in a significant increase in VapA-specific IgGs in the foals.
• However, there was noticeable variability in VapA-specific IgGs among foals, despite them all receiving the same product, indicating high inconsistency in response.
• The difference in IgGs was significant between HIP products and even varied within different lots of the same product.
• The variation coefficients ranged from 17 to 123 per cent, demonstrating high disparity.

Conclusion

• The substantial variation in VapA-specific IgGs in the recipient foals may explain the previously reported inconsistencies in the efficiency of HIP.
• The researchers suggest further studies to understand the underlying causes of this variability, which could contribute to developing more effective preventive measures against R. equi in the future.