ABSTRACT
Influenza A viruses exhibit segmented nucleic acid coding for eight different proteins, two of them as glycoproteins exposed on their lipoprotein envelopes, hemagglutinin (HA) and neuraminidase (NA). Hemagglutinin exhibits recptor-binding activity while neuraminidase develps sialidase cleavage activity which acts on cell receptors. Influenza A strains responsible for human, avian, equine and porcine respiratory infections all over the world present antigenically different hemagglutinin (H1 to H14) and neutraminidase (N1 to N9) structures on their surface. The objective of the present investigation was study the role of N2, N8 and N9, anti-genically diverse neuraminidase structures of human (N2) and animal (N8 and N9) influenza viruses, in the receptor-binding process. REceptor-binding activity of N2 and N8 was anlyzed by crossed tests using H3N2 and H3N8 antisera and the hemagglutination inhibition test as a model. Hemangglutinating activity of antigenically different N2 and N8 structures was demonstrable and was inhibited by homologous antisera (N2-H3N2, N8-H3N8) but not by heterologous antisera (N2-H3-N8,N8-H3-N2). This previously demonstrated N9 hemagglutinating activity was analysed for receptor-binding specificity using hemagglutination test and NeuAc alpha2,3Gal and NeuAc alpha2,6Gal derivatized erythrocytes. This highly purified N9 strain was obtained from a virus strain isolated from terns by Dr. Peter Colman (CSIRO Division of Biomolecular Engineering, Parkville, Victoria, Australia)...
Subject(s)
Hemagglutinins, Viral/physiology , Hemagglutination, Viral/physiology , Neuraminidase/physiology , Influenza A virus/immunology , Influenza A virus/physiologyABSTRACT
A number of glycoconjugates, including glycolipids and glycoproteins, participate in the process of host-cell invasion by Trypanosoma cruzi and one of the most important carbohydrates involved on this interaction is sialic acid. It is known that parasite trans-sialidase participates with sialic acid in a coordinated fashion in the initial stages of invasion. Given the importance of these sialogycoconjugates, this review sets out various possible biological models for the interaction between the parasite and mammalian cells that possess a sialylated receptor/ligand system