Antibody isotype responses in the serum and respiratory tract to primary and secondary infections with equine influenza virus (H3N8).

This research paper studied the response of different types of antibodies in the blood and respiratory tract of ponies during initial and repeat infection by the H3N8 equine influenza virus.

Objective of the Study

The main purpose of this research was to understand how horses’ immune systems respond to initial and repeat infections with the H3N8 strain of the equine influenza virus. Notably, researchers compared how specific types of antibodies in the blood serum (IgGab, IgM, and IgA) and in the respiratory tract (nasopharyngeal and tracheal) reacted to these infections.

Methodology and Findings

• The study was conducted using horses, which were infected with the H3N8 virus through a nebulised aerosol.
• The researchers found that the levels of IgGab, a type of antibody, remained high in the blood for a long time after the initial infection. The IgM antibodies, however, were only present for a short while after both the initial as well as the repeat infections.
• When the horses were re-infected with the virus, there was enough antigenic stimulation to increase the levels of IgM and IgA, even though the IgGab levels were already high in the blood.

Implications

• This study supports the idea that testing for IgM antibodies could be useful in identifying recent viral exposure in animals with high circulating levels of IgGab.
• Unlike IgGab in the blood, IgGab antibodies in the nasal and tracheal wash did not persist for a long time after the primary infection. However, anamnestic or immune memory responses were seen with re-infection, indicating the presence of local antibody memory.
• The researchers discovered that IgA antibodies in the nasopharynx developed later than IgGab and IgM antibodies, but they lasted longer.

In summary, this research increases our understanding of how the immune system in horses responds to the equine influenza virus and suggests future directions for diagnostic tests and a potential vaccine development.