[Live enteroviral vaccines for the emergency nonspecific prevention of mass respiratory diseases during fall-winter epidemics of influenza and acute respiratory diseases].

The results of the 3-year controlled trials of a new method of nonspecific urgent prophylaxis of influenza and acute respiratory diseases (ADR) by immunization of healthy adults with standard live enterovirus oral vaccines, introduced in 2-3 administrations at intervals of 7-10 days, at the initial stages of autumn and winter epidemics are presented. Observations, carried out in three republics, covered more than 150,000 persons immunized with enterovirus interferonogenic vaccines. A considerable decrease in morbidity rate among the vaccinees was achieved (on the average, by 3.

Potential use of nonpathogenic enteroviruses for control of human disease.

Until recently, it has been generally assumed that all human viruses are causative agents of diseases and should be regarded as harmful pathogenic agents that require control measures. In the early 1950s we began to doubt this view. In the course of experiments on virus isolations from feces of normal children, as well as in studies of isolates from animals and from tissue cultures, data accrued which suggested that some conditionally pathogenic and some completely nonpathogenic strains of enteroviruses may provide some benefit to their host by inhibition of pathogenic viruses and by activating nonspecific protective functions of the organism.

Identification of Bulgarian strain 258 of enterovirus 71.

In 1975 in Bulgaria a severe epidemic of central nervous system (CNS) disease occurred. Clinically, histopathologically, and epidemiologically the cases resembled poliomyelitis, aseptic meningitis, meningoencephalitis, and, in some cases, encephalomyocarditis. About 21% of the 700 reported cases developed paralysis, 44 with fatal outcome [ref.

Epidemiological, clinical, and pathomorphological characteristics of epidemic poliomyelitis-like disease caused by enterovirus 71.

In May-September, 1975, an outbreak of epidemic disease clinically and pathomorphologically simulating nearly all known forms of poliomyelitis occurred predominantly among young infants in Bulgaria. Most cases presented benign aseptic meningitis, sometimes with a short period of general cerebra- symptoms. Paralytic forms, such as bulbar polioencephalitis, anterior poliomyelitis, isolated pareses of the facial nerve, occasional cases of encephalomyocarditis, etc.

Investigation of physicochemical properties of Bulgarian strain 258 of enterovirus type 71. Brief report.

In the present report some general physicochemical properties and RNA characteristics of strain 258 of enterovirus (EV) 71, isolated in 1975 from cases of poliomyelitis-like disease in Bulgaria (1), are described. It is concluded, that the features of the virus are consistent with the previous identification, based on biological studies, of this virus strain as a member of enterovirus subgroup of picornaviridae family.

Enterovirus 71 isolated from cases of epidemic poliomyelitis-like disease in Bulgaria.

Virological and serological studies of an epidemic disease in Bulgaria, 1975, were carried out. Epidemiologically, clinically and pathomorphologically, the disease simulated almost all known forms of poliomyelitis, acute stem encephalitis, encephalomyocarditis and aseptic meningitis. The studies completely rules out the participation of polioviruses and provided comprehensive evidence for the etiological role of a peculiar enterovirus subsequently identified as enterovirus (EV) type 71 known in the literature since 1974.

[Biological characteristics and the morphology of human and animal central nervous system tissue in organ culture].

It is shown that in using the method of multiple organ cultivation, the tissues of the CNS in the human and animal embryo preserve their organotypical characteristics. The use of a cartilage plate increases the viability of the tissues and the duration of its maintenance in cultures. During the process of explantation the cultivated tissue undergoes some morphological modifications.

[Isolation of type 71 enterovirus from patients with a poliomyelitis-like disease during an outbreak in Bulgaria].

Virological examinations of 72 specimens obtained during an outbreak of a poliomyelitis-like disease in Bulgaria, 1975, yielded 23 strains of enterovirus type 71 (E71) and 5 strains of enteroviruses of other types. The viruses were isolated in green monkey kidney cell cultures, in newborn cotton rats, newborn white mice and in monkeys. Most of E71 strains (16 out of 23) were isolated from the autopsy materials (brains and spinal cords) from 9 children dying of poliomyelitis, meningoencephalitis, and encephalitis.

Differences in multiplication of virulent and vaccine strains of poliovirus type I, II, and III in laboratory animals.

Multiplication of virulent and vaccine strains of poliovirus type I, II and III in laboratory animals of different species was studied comparatively. The main criterion of virus reproduction was the production of the photoresistant virus progeny after inoculation of the animals with proflavin-photosensitized virus strains. On the whole, virulent poliovirus strains were characterized by replication in a wide range of hosts (monkeys, cotton rats, white mice, guinea pigs, rabbits, chickens, chick embryos), a low infective dose, production of the photoresistant progeny to a high titre, clinically overt disease in some animal species.

The morphology of tumors of the human gastrointestinal tract in short-term organ culture and the reaction of these tumors to infection with poliovirus.

A morphologic study of 57 cancers of the human gastrointestinal tract maintained in short-term organ culture was carried out, and the response of part of these tumors to infection with poliovirus was studied. The tumors, grown in vitro, mainly retained their original characteristics and histologic types. A certain correlation between the histologic type and its viability in short-term organ culture was revealed: the more differentiated forms were maintained better than the poorly differentiated ones.

[Characteristics of encephalomyocarditis virus isolated from sick monkeys].

A cytopathic filterable agent designated EMC-70 was isolated in 1970 from Macaca rhesus monkeys with encephalomyocarditis. Its biologic and physico-chemical properties were studied. A number of primary and continuous cell cultures were found to be susceptible to the virus, and it was pathogenic for monkeys and small laboratory animals but did not multiply in chick embryos.

[Development of poliovirus infection in laboratory animals of different species].

The capacity of vaccine and virulent strains of poliomyelitis virus to multiply in laboratory animals of different species was studied. Virus reproduction was judged by formation of photoresistant virus progeny in response to inoculation of the animals with photosensitized virus. Multiplication of virulent poliomyelitis virus strains observed in the majority of animal species examined (monkeys, newborn and adult cotton rats, newborn and adult white mice, chickens, chick embryos) resulted in active formation of photoresistant virus population and in some cases was accompanied by clinical symptoms of the disease.

[Use of cross-absorbed sera in neutralization tests with viral titration by the cytopathogenic effect].

A new method for intratypic antigenic differentiation of poliovirus strains has been developed. The method is based on the use of cross-absorbed sera in neutralization tests where virus is titrated by the cytopathic effect. Qualitative differences between the antigenic structure of vaccine and "wild" strains as well as between some "wild" strains of the same serologic type have been found.

[Status of herd immunity to poliomyelitis in children in the Moscow region].

The paper presents the results of 3-year observations of the status of herd immunity to poliomyelitis in 7 towns of the Moscow region. In individual years antibody for poliomyelitis virus of 3 types was found in 63-74% of the examined children and from 2.7 to 7.