Characterization and immunological properties of influenza A virus nucleoprotein (NP): cell-associated NP isolated from infected cells or viral NP expressed by vaccinia recombinant virus do not confer protection.

Abstract	A nucleoprotein (NP) preparation purified from the chorioallantoic membrane of chicken eggs infected with fowl plague virus (A/FPV/Rostock/34, H7N1) yielded, in addition to the commonly known 56K protein, a 42K component that could not be detected in virus particles. After testing with a series of NP-specific monoclonal antibodies it was found that some reacted with both proteins and others were bound only by the 56K protein. Among both types of NP-specific monoclonal antibodies only a limited number were bound to infected murine cells. Some antibodies bound to cells infected with a given subtype failed to react with the surface of cells infected with a different subtype. Binding was demonstrated by cellular ELISA, radioimmunoassay and immunofluorescence. The results indicate that only restricted antigenic domains of the native NP and perhaps NP fragments are exposed at the surface of infected murine cells. Additionally, the purified NP preparation was used to immunize mice in order to determine the protective capacity of cell-associated NP. In parallel, and as a relevant control, mice were immunized with a vaccinia virus recombinant containing the gene for NP prior to challenge with infectious virus. High levels of monospecific antibodies and a cytotoxic T cell activity was found in mice immunized with purified NP or infected with the vaccinia recombinant after secondary restimulation in vitro. After treatment with specific antibodies the cytotoxic cells were shown to be classical CD8+ cytotoxic T lymphocytes. Despite the elicitation of a humoral and a cellular immune response by the forms of NP employed mice were not protected from influenza virus infection.
Authors	L Stitz, C Schmitz, D Binder, R Zinkernagel, E Paoletti, H Becht
Journal	The Journal of general virology (J Gen Virol) Vol. 71 ( Pt 5) Pg. 1169-79 (May 1990) ISSN: 0022-1317 [Print] England
PMID	1693165 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References	Antibodies, Monoclonal Antigens, Viral DNA, Recombinant Epitopes NP protein, Influenza A virus Nucleocapsid Proteins Nucleoproteins RNA-Binding Proteins Viral Core Proteins Viral Proteins
Topics	Animals Antibodies, Monoclonal Antigens, Viral (immunology) Cell Line Chick Embryo DNA, Recombinant Enzyme-Linked Immunosorbent Assay Epitopes (analysis) Female Fluorescent Antibody Technique Immunization Influenza A virus (immunology) Lymphocyte Activation Male Mice Mice, Inbred Strains Nucleocapsid Proteins Nucleoproteins (immunology) Orthomyxoviridae Infections (immunology, prevention & control) RNA-Binding Proteins Radioimmunoassay T-Lymphocytes, Cytotoxic (immunology) Vaccinia virus (genetics, immunology) Viral Core Proteins Viral Proteins (immunology)

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