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Ultrastructural features of antigens associated with human hepatitis.

Viruses were among the first objects to be examined in the electron microscope over 30 years ago, yet little information was gained on their fine structure, except in the bacteriophage field, until the advent in 1959 ofthe negative contrast technique for high resolution electron microscopy. Briefly, the principal advantages of negative staining are that the technique is relatively unaffected by impurities of small molecular size which merge with the background and conversely large sized impurities are clearly distinguishable from virus particles. Furthermore, negative staining has yielded clear images revealing many detailed and intricate features of particulate structures and the technique may also be readily used as a quantitative tool. The discovery of the Australia antigen in serum and its specific association with serum hepatitis or type B viral hepatitis represents a major advance in the long and frustrating search for at least specific laboratory tests. However, the exact relationship of the Australia antigen to the infectious agent or agents remains as yet unsettled, although the antigen shares a number of morphological features with known virus structure and a small amount of ribonucleic acid has been detected in purified antigen preparations.