Scanning and transmission electron microscopy study of ferret respiratory mucosa infected with influenza A virus.

The use of both SEM and TEM techniques in studying the alterations of the columnar ciliated epithelium of the whole respiratory tract of ferrets enables the authors to find a significant discrepancy between tracheal and nasal mucosa destructions. This discrepancy is not a function of the anatomical location of virus instillation. Theoretical and pratical meanings are discussed.

[Contribution to the antigenic study of influenza viruses in animals. I.--Neuraminidase of the equine influenza viruses (author's transl)]. / Contribution a l'étude antigénique des virus influenza des animaux. I.--Neuraminidase des virus influenza équins

From the Revised Nomenclature of WHO, the fowl influenza virus A/Duck/Ukraine/63 (Hav7 Neq2) has the same neuraminidase as the equine virus A/equi 2/Miami/63 (Heq2 Neq2); the A/Chicken Germany "N"/49 virus has the same neuraminidase as the equine virus A/equi 1/Prague/56. A comparative study of the antigenic specificities confirms that the Neq2 neuraminidases are closely connected, whatever their animal origin, and that the fowl strain Hav7 Neq2 can be used for the titration of anti Neq2 antibodies in the serums of animals immunized with the equine virus Heq2 Neq2. The Neqi neuraminidases of various animal origins are connected, but the neuraminidase of the fowl strain Hav2 Neqi is slightly inhibited by the anti Neq1 antibodies of animals immunized with the Heq1 Neq1 virus: to titrate the anti Neq1 antibodies of equine origin, the H72 Neq1 recombinant should therefore be used. The antigenic characterization of the different equine influenza strains isolated since 1967 by the study of their neuraminidase has been completed: The various neuraminidases, like the hemagglutinins of the various strains belonging to the sub-type A equi2 are closely connected; a minor antigenic variation, concerning the two surface antigens, seems to exist between the strain A equi 1/Prague/56 and the strain of the same subtype isolated in 1973.

Morphology, biochemical analysis and neuraminidase activity of rubella virus.

A simple and reproducible method for the production of purified rubella virus is described. Purified virus was subjected to morphological and chemical analysis. The virus particles were rather pleomorphic (60 nm diameter), sometimes with one or more peripheral protrusions. The viral surface, revealed by negative staining, was composed of spikes 6 nm long, featuring enlarged ends. In SDS-urea-polyacrylamide gel electrophoresis, 4 major and 4 minor polypeptide bands were revealed. Total lipids and phospholipids were analysed on the same preparation. The viral particles were composed of RNA: 0.030 mg, and lipids: 0.245 mg, of which 0.169 mg were phospholipids for each mg of viral protein. Biologically, the purified virus preparation showed high infectivity, a high hemagglutination titre and a weak neuraminidase activity under defined conditions.

Influenzavirus neuraminidase and neuraminidase-inhibition test procedures.

The adequate characterization of type A influenzaviruses requires the identification not only of the haemagglutinin but also of the neuraminidase. The neuraminidase-inhibition test, as performed in the two WHO international reference centres for influenza, is described and its use in other laboratories-particularly those collaborating in the WHO programme-is recommended.