Mvs. Coimbra et al., THE ROLE OF ANTIGENICALLY DIFFERENT VIRUS NEURAMINIDASES AS STRUCTURES IMPLICATED IN RECEPTOR-BINDING PROCESSES, Brazilian journal of medical and biological research, 28(6), 1995, pp. 627-631
Influenza A viruses exhibit segmented nucleic acid coding for eight di
fferent proteins, two of them as glycoproteins exposed on their lipopr
otein envelopes, hemagglutinin (HA) and neuraminidase (NA). Hemaggluti
nin exhibits receptor-binding activity while neuraminidase develops si
alidase cleavage activity which acts on cell receptors. Influenza A st
rains responsible for human, avian, equine and porcine respiratory inf
ections all over the world present antigenically different hemagglutin
in (H-1 to H-14) and neuraminidase (N-1 to N-9) structures on their su
rface. The objective of the present investigation was to study the rol
e of N-2, N-8, and N-9, antigenically diverse neuraminidase structures
of human (N-2) and animal (N-8 and N-9) influenza viruses, in the rec
eptor-binding process. Receptor-binding activity of N-2 and N-8 was an
alyzed by crossed tests using H3N2 and H3N8 antisera and the hemagglut
ination inhibition test as a model. Hemagglutinating activity of antig
enically different N-2 and N-8 structures was demonstrable and was inh
ibited by homologous antisera (N-2-H3N2, N-8-H3N8) but not by heterolo
gous antisera (N-2-H3N8, N-8-H3N2). This previously demonstrated Ns he
magglutinating activity was analyzed for receptor-binding specificity
using hemagglutination tests and NeuAc alpha2,3Gal and NeuAc alpha2,6G
al derivatized erythrocytes. This highly purified N-9 strain was obtai
ned from a virus strain isolated from terns by Dr. Peter Colman (CSIRO
Division of Biomolecular Engineering, Parkville, Victoria, Australia)
. It exhibited receptor-binding specificity for NeuAc alpha2,3Gal sequ
ences, a property similar to that observed in hemagglutinins from avia
n strains, These results indicate the importance of antigenically diff
erent neuraminidase structures as alternative agents for developing re
ceptor-binding activity. Further studies are needed to determine the r
ole of different neuraminidases as structures responsible for receptor
-binding activity influencing the release of progeny virus from host c
ells.