STUDIES OF PROTEIN-A AND HERPES-SIMPLEX VIRUS-1 INDUCED FC-GAMMA-BINDING SPECIFICITIES - DIFFERENT BINDING PATTERNS FOR IGG3 FROM CAUCASIANAND ORIENTAL SUBJECTS

Herpes simplex virus type 1 (HSV-1) expresses a receptor that binds th e Fc portion of IgG. This HSV-1 Fc gamma-binding protein is, like prot ein A of Staphylococcus aureus, known to bind human IgG1, IgG2 and IgG 4 but not IgG3 subclasses. However, IgC3 with the allotype Gm(s(+))(t( +)), prominent in the Oriental population, reacts with protein A. This prompted us to investigate the reactivity of Oriental IgG3 monoclonal myeloma proteins of various allotypes with the HSV-1 Fc gamma-binding protein. Of seven Oriental IgG3 myeloma proteins with allotypes Gm(s( +))(t(+)) (u(-))(b(+))(g(-)), Gm(s(-))(t(-))(u(+))(b(+))(g(-)) and Gm( s(-))(t(-))(u(+))(b(-))(g(+)), all reacted with the HSV-1 Fc gamma-bin ding protein. This was in contrast to negative reactions obtained with three IgG3 myeloma proteins of Caucasian origin with Gm(b(+))(g(-)) o r Gm(b(-))(g(+)) phenotypes. The same binding pattern, i.e. binding of IgG3 of Oriental but not of Caucasian origin, was found with protein A. The binding of the monoclonal Oriental IgG3 proteins was again inde pendent of the G3m phenotype. These findings support the concept that the HSV-1 Fc gamma-binding protein and protein A have a similar bindin g site on the IgG molecule. All monoclonal IgG3 proteins derived from Oriental subjects with or without histidine at position 435 bound to H SV Fc gamma-binding protein. This suggests that Oriental IgG3 myeloma proteins with Gm(s(-))(t(-)) phenotypes have additional critical amino acid residue substitutions important for HSV Fc gamma binding differe nt from those already known.