[Contribution to the antigenic study of influenza viruses in animals. II.--Antibodies, antineuraminidase in horse: conditions of apparition and importance (author's transl)].

In the first part of this paper the conditions for a specific titration of antibodies against the neuraminidase (N) of each of the two horse virus subtypes are defined. The antigens used are: the H72Neq 1 recombining agent to measure the anti Neq1 antibodies and the A/Duck/Ukraine/63 strain for the anti Neq2 antibodies. The immunity response to neuraminidase appears after the natural disease; this response is studied in two foci, one due to a virus belonging to the A equi I subtype (Loire 73 strain), the other to a virus of the A equi 2 subtype (SHN 73 strain). The kinetics of apparition of anti N antibodies is mostly comparable to that of antihemagglutinin antibodies. The vaccination also induces an immunity response to neuraminidase: the intensity of this response gives an additional information for studying and checking the efficiency of equine i influenza vaccines.