Hemagglutinin inhibition assay with swine sera.

Hemagglutination is based on the ability of viruses such as influenza A virus to agglutinate red blood cells (RBCs) of specific animal species by formation of cross-linking lattices between RBCs. Antibodies that have the ability to inhibit the hemagglutination property of influenza A viruses are correlated with protection from infection. The hemagglutination inhibition (HI) test is a serological assay that measures the titer of specific antibodies in the sera and is the most common serological assay used to detect anti-influenza antibodies in swine sera.