Changes in immunoglobulin levels in whey during experimental Streptococcus agalactiae mastitis

Area of Science:

• Veterinary Immunology
• Bovine Health
• Mastitis Research

Background:

• Intramammary infections (IMIs) caused by Streptococcus agalactiae pose a significant threat to dairy cattle health and productivity.
• Understanding the host's immune response, particularly in first-lactation heifers, is crucial for developing effective prevention and treatment strategies.
• Immunoglobulin profiles in whey can indicate the local immune status during infection.

Purpose of the Study:

• To evaluate the impact of vaccination on the whey protein and immunoglobulin profiles of first-lactation heifers during repeated experimental Streptococcus agalactiae intramammary infections.
• To compare the immune responses between vaccinated and unvaccinated heifers following sequential infections.

Main Methods:

• Whey total protein and immunoglobulin (IgG1, IgG2, IgA, IgM) levels were measured in eight first-lactation heifers (four vaccinated, four unvaccinated) over three consecutive experimental Streptococcus agalactiae IMIs.
• Uninfected quarters served as controls to assess baseline levels.
• Whey samples were collected at regular intervals post-infection to monitor dynamic changes.

Main Results:

• No significant differences in protein or immunoglobulin content were observed in uninfected quarters between groups or infections.
• Peak whey total protein in infected quarters occurred earlier with each successive infection, reaching 8 hours by the third infection.
• A reversal of the normal milk IgG1/IgG2 ratio was noted in infected quarters during the acute phase.
• Vaccinated heifers exhibited increased whey IgA and IgM in infected quarters earlier than unvaccinated heifers, whose response was primarily seen after the third infection.
• All immunoglobulin levels returned to baseline by 48 hours post-infection, with a subsequent increase in IgG1 in infected quarters.

Conclusions:

• Vaccination against Streptococcus agalactiae primes heifers for a more robust and accelerated local immune response during subsequent intramammary infections.
• The observed changes in whey protein and immunoglobulin profiles, particularly the IgG1/IgG2 ratio reversal and increased IgA/IgM, highlight key aspects of the adaptive immune response to mastitis.
• These findings support the use of vaccination as a strategy to enhance resistance against Streptococcus agalactiae-induced mastitis in dairy cattle.