Influenza A virus hemagglutinin specific antibodies interfere with virion neuraminidase activity via two distinct mechanisms.
We studied the ability of monoclonal Abs (mAbs) recognizing the major hemagglutinin (HA) antigenic sites to inhibit neuraminidase (NA) cleavage of sialic acids on fetuin. We show that virion associated-NA activity in the enzyme linked lectin assay (ELLA) is largely dependent on HA-mediated attachment of virions to immobilized fetuin. For a Sb-antigenic site specific mAb, there is a nearly perfect correlation between neuraminidase inhibition and blocking virus attachment to immobilized fetuin. By contrast, Sa-, Ca-, and Cb- antigenic site specific mAbs block NA activity in ELLA or the traditional thiobarbituric acid assay by sterically interfering with NA access to substrate. We conclude first, that ELLA with intact virus can only be used to measure anti-NA Abs if sera lack HA-specific Abs, and second, that anti-HA Abs block NA activity by both limiting virion interaction with sialic acid containing surfaces and by sterically limiting NA access to sialic acids attached to macromolecules.
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, United States of America.
Ivan
I
Kosik
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, MD 20892, United States of America.
Jonathan W
JW
Yewdell
D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000494:pharmacology; D000914:Antibodies, Viral / Q000737:chemistry* / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology*; D006801:Humans; D009980:Influenza A virus / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D007251:Influenza, Human / Q000821:virology; D007700:Kinetics; D009439:Neuraminidase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D014764:Viral Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D014771:Virion / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics
D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D004791:Enzyme Inhibitors; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D014764:Viral Proteins; C487630:NA protein, influenza A virus; D009439:Neuraminidase
Canonical antigenic sites; ELLA; HA antibodies; Influenza; NA inhibition; TBAA