Rabies Oral Immunization

Abstract

My interest in oral immunization dates to 1950 when I fed a child the live, attenuated polio virus vaccine. During the ensuing several years, many more children were immunized with this vaccine, and these efforts culminated in mass oral immunization of 250,000 infants in the Belgian Congo, during the epidemic of true infantile paralysis. This immunization required six weeks to perform. Our current interest in oral immunization stems from the fact that our real problem, as far as rabies is concerned, is not domestic animals, and not even vaccines for humans, but for effective vaccines for wildlife. The experience, particularly of Europeans with foxes, has indicated that the eradication of rabies in wildlife cannot be achieved by reducing the reservoir species by killing, gassing, or any other rather barbaric method. Instead, immunization of the wild reservoir animals offers an alternative approach (Steck et al. 1982). The questions are, how and what type of vaccine could be used, and how effective it would be — and this is the subject of my contribution. I will be discussing only one type of vaccine — the vaccinia-rabies glycoprotein recombinant vaccine (V-RG). I do not need to present details about the vaccine, other than that it is obtained by the cDNA derived from the mRNA for rabies glycoprotein incorporated into a construct plasmid from which it is in turn incorporated with vaccinia virus TK gene plasmid (Kieny et al. 1984). Transfection of vaccinia-infected cells with the plasmid allows double reciprocal recombination in vivo and final construction of the V-RG recombinant virus vaccine with the rabies glycoprotein gene interrupting the vaccinia TK gene sequence.