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Further studies on the use of protein A in immune electron microscopy for detecting virus particles
The immune electron microscopic technique which involves pre-coating electron microscope grids with protein A before coating them with the specific antiserum, has been found suitable for detecting isometric insect and plant viruses. With the three virus-antibody combinations tested, the optimum antiserum dilution for protein A plus antiserum treatment was found to be 1:100 or less, whereas in the case of grids treated with antiserum alone it ranged from 1:1000 to 1:2000 although the titre of the antisera ranged from 1:512 to 1:4096. The increase in the number of particles on grids treated with protein A plus antiserum over those treated with antiserum alone, at each optimal antiserum dilution, was 25.7-fold (sugarcane mosaic virus), 2.1-fold (tobacco mosaic virus) and 1.6- and 2.4-fold (Erysimum latent virus--two different sap dilutions). Protein A plus antiserum-coated grids can be stored for up to 6 months at 4 degrees C, but not at room temperature or in a desiccator, and still retain about 25% of their activity, sufficient to detect any virus using the electron microscope. Antisera preserved in glycerol can be used successfully for detecting viruses by immune electron microscopy.
The immune electron microscopic technique which involves pre-coating electron microscope grids with protein A before coating them with the specific antiserum, has been found suitable for detecting isometric insect and plant viruses. With the three virus-antibody combinations tested, the optimum antiserum dilution for protein A plus antiserum treatment was found to be 1:100 or less, whereas in the case of grids treated with antiserum alone it ranged from 1:1000 to 1:2000 although the titre of the antisera ranged from 1:512 to 1:4096. The increase in the number of particles on grids treated with protein A plus antiserum over those treated with antiserum alone, at each optimal antiserum dilution, was 25.7-fold (sugarcane mosaic virus), 2.1-fold (tobacco mosaic virus) and 1.6- and 2.4-fold (Erysimum latent virus--two different sap dilutions). Protein A plus antiserum-coated grids can be stored for up to 6 months at 4 degrees C, but not at room temperature or in a desiccator, and still retain about 25% of their activity, sufficient to detect any virus using the electron microscope. Antisera preserved in glycerol can be used successfully for detecting viruses by immune electron microscopy.