Correlation Between Serum Amyloid A and Antibody Response to West Nile Virus Vaccine Antigen in Healthy Horses.

This research aimed to discover if levels of Serum Amyloid A (SAA) in horses can be used to determine appropriate immune response to a West Nile Virus (WNV) vaccine. However, the results revealed that there isn’t a significant link between SAA levels and the production of antibodies (the measure of immune response). The study also discovered that age impacts SAA response and that the WNV vaccine might not consistently cause an increase in WNV antibodies.

Research Methodology

• The study involved 60 healthy horses in total. Initially, a pilot study was conducted with 20 horses to identify peak SAA concentration following immunization with a multivalent WNV vaccine.
• Blood samples were collected at various intervals (0, 24, 48, 72, 96, 168 hours) post-vaccination for determining SAA levels.
• The serum for WNV serum neutralization antibody testing was obtained just before vaccination and 30 days after vaccination.
• The study protocol was then repeated with an additional 40 horses, however, their SAA levels were only measured at 0-hours and 72-hours post-vaccination.

Main Findings

• The results of the study showed that 90% of the horses experienced an increase in SAA concentration in response to WNV vaccination.
• Despite such nearly universal response, no significant correlation was found between the peak SAA levels and changes in antibody titer (a measure of the concentration of antibodies in the blood), indicating that SAA levels do not reflect antibody response.
• Upon comparing WNV antibody titer changes pre- and post-vaccination, it was found that 57% of horses showed increased fold changes, 30% showed no change, while 13% showed negative changes.
• A significant negative correlation between age and SAA response was noted (P = .0008), signifying horses’ age may influence SAA response significantly.

Conclusions

• The study found that SAA response post WNV vaccination does not mirror the antibody response, contradicting the premise of the research.
• Age has a significant impact on the SAA response, with older horses seemingly producing less SAA post-vaccination.
• Last but not least, the inconsistency in positive increases in WNV antibodies post-vaccination suggests that the used WNV vaccine may not reliably induce a persistent and robust immune response.