Dermovaccine

DERMOVACCINE (from Greek derma- skin), the poison of cowpox (vaccine), obtained by cultivation in the skin epithelium of various animals (see Detritus). The need to highlight the special properties of D. arose in connection with the teaching of Levaditi about the tropism of the pox and vaccine viruses. According to Levaditi, both viruses have a special affinity for derivatives of the outer germ layer (skin, brain, testicle, mammary gland, ovary, etc.). After a series of passages through the rabbit brain, D. becomes exclusively neurotropic and acquires other new properties. For the first time, Marie (1920) showed that the vaccine poison, injected under the dura mater of a rabbit, multiplies in the brain substance, and the animal dies on the 5-6th day with paralytic phenomena, while the brain obtained with aseptic precautions turns out to be sterile (thus, ordinary vaccine microbes die in the rabbit brain). If the brain of a dead rabbit is injected subdurally into a healthy rabbit, the above phenomenon is repeated (Levaditi and Nicolau). To the present day, Levaditi and other researchers have obtained more than 200 passages (e.g., Gallardo in Spain - 240 passages of brain vaccine - 'neurovaccine'). The differences between dermo- and neurovaccine are as follows: 1) D., cultivated in the rabbit brain, acquiring with increasing number of passages an increasing affinity for the nervous system, at the same time loses the ability to take on the skin. These non-neurotropic properties are stably inherited and appear to the same degree regardless of the method of administration of the poison (on the cornea, in the brain, in the testicle, in the skin, in the veins, etc.). Thus, the neurovaccine poison injected into the testicle more quickly and easily makes its way to the brain than D. (Levaditi). The same is also true with intravenous administration. However, Levaditi himself admits that in the latter case, multiplication of the virus in the brain often does not occur, despite its abundance in other organs. Other authors either dispute Levaditi's data on the neurotropic properties of the passage poison or confirm it only in part. Recently, Levaditi has not been so categorical about this and has put forward another feature of neurovaccine in the first place: its special reactivity when applied to the skin. Thus, for example, the difference between the two poisons sharply manifests itself when applied to the comb of a rooster: D. causes the formation of powerful pocks, while neurovaccine causes only individual small nodules or does not take at all. This difference is even more pronounced in relation to rabbit skin: pocks from neurovaccine are larger, more deeply embedded in the tissues, surrounded by a wide belt of inflammatory redness; infiltration is very pronounced, and edema is almost always observed. The pocks are hemorrhagic, of a bluish-purple color, prone to dry necrosis, the scabs fall off later, and deeper scars remain in their place. 2. D. is more resistant to thermal influences; for example, when heated to 55° it dies much later than neurovaccine; D. also has this increased resistance to the action of concentrated bile. 3. There is cross-immunity between dermo- and neurovaccine. On this basis, Levaditi and Nicolau consider it possible to use neurovaccine in practice of vaccination instead of ordinary D. The most extensive experience was carried out by Gallardo in Spain, who vaccinated more than 2^1/2 million people with neurovaccine. At the same time, the following distinctive features of neurovaccine compared to D. were found: slower development of pocks on the first vaccination (and the pocks are very often smaller than the length of the incision), their tendency to form central necrosis. Cases of excessively strong local reaction with the appearance of satellite pocks, with diffuse redness and even with the development of generalized vaccinia were also noted. The take rate of neurovaccine (85-90%) is significantly lower than that characteristic of D. (98-100%). In addition, inexplicable fluctuations in the virulence of neurovaccine have been noted (Gilmeister). According to Stanley, neurovaccine (Gallardo strain) runs milder in humans than D. About 100 people were vaccinated with viruses of both poisons. Upon revaccination with strong D., a higher degree of immunity was found in those previously vaccinated with the same virus (D.). In connection with the increasing cases of vaccinal encephalitis (see Vaccination and Encephalitis), recently the assumption (Goiter) has arisen about the spontaneous appearance of neurotropic properties in ordinary dermovaccine. In Holland, where this complication was observed particularly often (1 case in 15,000 vaccinations), after replacing D. with neurovaccine in 50,000 vaccinations, 5 cases of encephalitis were still observed, i.e., 1:10,000. In general, neurovaccine has by no means justified the hopes placed in it by some researchers. D. still remains the best and most reliable preparation for vaccination in humans.