[Virus-neutralizing properties of rabbit anti-influenzal IgG with a lowered complement-binding and cytophilic...

Relationship between the virus-neutralizing property and the effector functions of anti-viral IgG antibody was studied by using rabbit IgG against influenza virus, strain A/PR8/34. The single disulfide bond located in the hinge region of the IgG molecule was reduced to change the effector activity of the antiviral antibody. The reduced antibody retained approximately 50% of the initial complement fixing activity, but lost completely its ability to be fixed in heterologous tissue. When tested in the inhibition-hemagglutination test the reduced antiinfluenza IgG retained complete antigen binding activity. The virus-neutralizing activity of the reduced antiinfluenza IgG (tested on chick embryo) did not differ from that of the crude preparation when 100 EID50 were used. When the dose of the virus was increased up to 1000 EID50 the neutralizing activity of the reduced IgG was found to be less than that of the unreduced one. The results obtained are discussed proceeding from the structural organization of the reduced IgG.