Vaccines for latent viruses.

There are two traditional ways to modify a virus for immunization: (1) kill the virus or (2) use a live, attenuated virus. There are three modern ways to prepare vaccines: (1) extract and purify a part of the virus that is immunogenic, (2) synthesize a polypeptide immunogen piece of the virus, or (3) use recombinant deoxyribonucleic acid or gene splicing to prepare an immunogenic portion of the virus. The last three produce subunit vaccines that can be made to contain no deoxyribonucleic acid. They are not infectious and are likely to be nononcogenic. Using recombinant deoxyribonucleic acid techniques, a vaccine for bovine papillomavirus has been prepared. This is in clinical trials and probably will be licensed for use in cattle in 1988. A vaccine for herpes simplex virus has been prepared using glycoprotein D from the surface of the virus. This immunizes animals but it has not reached clinical trials in humans.