Military-medical Academy (S.-Petersburg, Russia)
Эта статья опубликована в сборнике по материалы первой Международной юбилейной конференции «Актуальные проблемы инфектологии и паразитологии» , посвященной 110-летию со дня открытия проф. К.Н.Виноградовым сибирской двуустки у человека (2-5 апреля 2001, г. Томск)
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Long (more than 40 years) experience in studying toxoplasmosis covering near three thousand patients, allows us to suggest the necessity of revising currently existing approaches to the treatment of reactivated toxoplasmosis in immunocompetent persons.
Our studies show that long-term antiprotozoan therapy (courses lasting from 1 month up to 1 year and more), in cases when there are no any clinical or/and laboratory findings of AIDS, is of little benefit. The recurrence rate (according to domestic, as well as foreign researchers) is rather significant and reaches 65 %.
The pathogenesis of chronic toxoplasmosis (ChT) exacerbation, in contras to immune reactions in primary infection, is characterized by not triggering the immune response, but breaking the tolerance to toxoplasmic antigens with the development of cytotoxic effect, directed to destroying the infected cells (transformation in Th2-type immune response). But at the same time, the toxoplasmas were found not die after destroying the host cells, but continue to infect intact normal structures. Therefore, conditions are created for long persistence of the parasites, damage of cells, modification of cellular membranes, formation of an autoallergic component.
Under these conditions long-term antiprotozoan therapy can not provide the total eradication of the organisms, since doses of drugs required greatly exceed ones maximally permissible. In addition, a number of side effects greatly increase in prolonged administration of the medications (more than 2 weeks).
Pathologically the use of immunomodulators such as «Viferon» has not been adequately justified. The interferon inductors stimulate synthesis of alpha-interferon, which activates cytolysis of infected cells. However, life cycle of toxoplasmas in humans is unique in that the destruction of all infected cells may not only not be real (majority of parasites are located in cysts or/and pseudocysts and are inaccessible both for antiprotozoan medications as well as for "killing" cells), but also dangerous for human body (cytolysis in CNS, myocardium, retina).
We have long been using specific immunomodulation (vaccination, specific hyposensibilization according to professor A.Kazantsev) with toxoplasmin (complex of large surface antigen T. gondii RH-strain) in the treatment of ChT’ exacerbation in patient without any signs of AIDS. The recent studies have shown that mechanisms of the toxoplasmin’ action represent the switching of immune response from Th2 to Th1-type at the cost of activation of macrophage clone specific to T. gondii, increased production of gamma-interferon, reduction of the cytotoxic effects. The analysis of a given technique has shown that one-shot course of immunomodulation with toxoplasmin (5-8 days according to the author) leads to the development of long-term tolerance and clinical remission in 91,2 % cases.