Role of gangliosides in reception of influenza virus

The ganglioside composition of Ehrlich ascites carcinoma (EAC) cells and the role of the individual gangliosides in binding and penetration into the cell of influenza virus were determined. EAC gangliosides identical with or close to GM3, GM2, GM1, GT1a and GT1b were characterized by thin-layer chromarography, compositional analyses, methylation analysis and mass-spectrometry. The ganglioside uptake capacity of native and neuraminidase-treated EAC cells was studied with tritium-labeled gangliosides of definite structure and the binding of influenza virus to cells was determinated by using [3H]uridine-labeled virus and by hemagglutination studies. Treatment of the cells with Vibrio cholerae neuraminidase largely decreased binding of the virus. Exogenous gangliosides with a terminal galactose unit or a penultimate galactose masked by neuraminic acid were able to restore the virus-binding capacity of neuraminidase-treated cells, however, the main ganglioside of EAC cells, GM2, which carbohydrate chain is terminated by N-acetylgalactosamine, was completely ineffective. The common carbohydrate sequence of the gangliosides showing binding activity (formula; see text) is proposed to be the main recognition structure of the influenza virus receptor on the surface of EAC cells. Penetration of labeled influenza virus into the nuclei of EAC cells was evaluated by measuring the radioactivity of the nuclei of neuraminidase-treated ganglioside-loaded cells after exposition to the labeled virus. Of all gangliosides tested only trisialogangliosides of the GT1b type were able to induce increased entry of the virus into the cells and accumulation of its radioactive component into the nuclei. It is suggested that GT1b gangliosides react specifically with the virus protein responsible for membrane fusion (apparently the hemagglutinin HA2 subunit) and thus are involved in virus penetration and delivery of the virus genome to the nuclei.