An alternative vaccine might employ one or a number of antigens of the virus prepared by recombinant DNA technology, probably in commercial yeast cells. Much progress on this approach has been made by a number of groups recently (National Institute of Allergy and Infectious Diseases, Chiron Corporation, Merck Sharp & Dohme [National Institute of Allergy and Infectious Diseases, 1985]) and has been reviewed by Purcell et al. (1984). One of these noninfective antigens might be ideal for inclusion in a complex vaccine against multiple agents. A possible combination would include an HAV subunit and agents of the herpesvirus family (e.g., herpes simplex, cytomegalovirus, and varicella-zoster).
Other approaches to hepatitis A vaccines include the use of synthetic peptides mimicking portions of the viral coat proteins. These would be used with adjuvants or carriers.
A single injection of live virus vaccine would be expected to induce lifetime immunity. The noninfective antigens might have to be administered intermittently. Predictions on the prospects of vaccine development are shown in Table 5.1.
Clinical testing of an attenuated live virus vaccine prepared by the National Institute of Allergy and Infectious Diseases has been projected for 1986 (National Institute of Allergy and Infectious Diseases, 1985).
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