[Group enterovirus infection due to coxsackievirus A16 in Northwestern Russia].

AIM: Study features of epidemic process and etiology of oral cavity and limb enterovirus exanthema group diseases in a number of territories of Northwestern Russia. MATERIALS AND METHODS: Isolation and identification of non-poliomyelitis enteroviruses from material of patients was carried out according to WHO recommendations. Phenotyping and phylogenetic analysis of enteroviruses was carried out. RESULTS: In 3 territories of Northwestern Russia oral cavity and limb enterovirus group diseases were registered. Children aged less than 14 years, predominately aged less than 3 years, were shown to be involved in the epidemic process. Coxsackie A16 enteroviruses from 27 samples of patients were isolated in cell cultures and identified by using specific sera. Coxsackie A16 enteroviruses from 16 samples were identified by using partial sequencing of VP1 genome area. Phylogenetic analysis has shown that the identified Coxsackie A16 viruses distributed among 2 phylogenetic groups. CONCLUSION: Coxsackie A16 enteroviruses that had never been detected in the region previously were established to be the etiologic factor of oral cavity and limb enterovirus exanthema group disease in the 3 territories of Northwestern Russia. The data obtained give evidence on the necessity of epidemiologic and virological control for enterovirus infection with the aim of obtaining novel information on the circulation of non-poliomyelitis enteroviruses in the population and the establishment of development patterns for epidemic process of this infection.

[Risk of introduction and spread of polioviruses in closed-type child-care facilities].

AIM: Compare frequency of isolation of polioviruses in children living in closed-type facilities (orphanages) before and after the change in poliomyelitis vaccination scheme. MATERIALS AND METHODS: Feces samples of 207 children from 5 orphanages during immunization with oral poliomyelitis vaccine (OPV) and of 259 children from 4 orphanages during vaccination with inactivated poliomyelitis vaccine (IPV) were studied. Isolation and identification of polioviruses was carried out according to WHO recommendations. RESULTS: In orphanages, where children were immunized with the oral vaccines, 21 polioviruses were isolated. In orphanages, where only inactivated vaccine was used, 10 polioviruses were isolated, the presence of polioviruses in these facilities is associated with their introduction from the outside. The percentage of poliovirus detection in children immunized with OPV was shown to be 16.9 ± 3.4% and was significantly higher than in children vaccinated with IPV (6.1 ± 1.9%). Polioviruses isolated from children immunized with OPV belonged to serotypes 1, 2 and 3 in 19.0, 14.3 and 66.7% of cases, respectively. Polioviruses detected in children immunized with IPV belonged to serotypes 1, 2 and 3 in 30, 40 and 30% of cases, respectively. All the isolated polioviruses turned out to be Sabin vaccine strains. CONCLUSION: Implementation of strict prophylaxis measures in orphanages is necessary in order to prevent the possibility of introduction, transmission and circulation of polioviruses. Improvement of control in children from closed-type facilities will ensure maintenance of Russian Federation status as the country free of poliomyelitis.

[Immunity to polioviruses in children population of various territories of the Russian Federation].

AIM: Analyze the state of population immunity to polioviruses in children population of 14 administrative territories of the Russian Federation. MATERIALS AND METHODS: Antibody titers against reference vaccine poliovirus serotypes 1, 2 and 3 were determined by using neutralization reaction in cell culture Hep-2. RESULTS: Several years after the termination of conduction of National immunizations days the percent of seronegative children was shown to increase, especially to poliovirus serotype 3, in most of the territories. Possible reasons for fluctuation of geometric mean antibody titers against polioviruses in children in various territories as well as in various years in the same territory were established. CONCLUSION: Quality vaccine prophylaxis and control of population immunity state among children population play an important role in the maintenance of Russian Federation status as a country is free from poliomyelitis.

[The role of epidemiologic surveillance of migrants in the system of poliomyelitis control].

AIM: Analysis of results of virological study of material from children of migrants and evaluation of intensity of immunity against polioviruses in these children. MATERIALS AND METHODS: 1668 feces samples from patients with acute flaccid paralysis and contact individuals and 479 feces samples from healthy children from families of migrants, as well as 1012 blood sera of children aged 3 - 4 and 14 - 15 years living in the same territory of Russia, and 169 blood sera of children of migrants were studied. Polioviruses and non-polio enteroviruses were isolated by standard procedures recommended by WHO in 3 cell cultures - RD, L20B and Hep-2. Virus identification was carried out by microneutralization test with rabbit antisera against poliomyelitisvirus, RIVM (Bilthoven, Netherlands). For intra-type differentiation EIA and PCRwere used. Antibody titers were determined in microneutralization reaction with reference poliovirus vaccines strains in Hep-2 cell culture. RESULTS: The frequency of detection of polioviruses in children of migrants was significantly higher than in patients with acute flaccid paralysis. In a larger percent of cases children of migrants did not have protective antibody titers against polioviruses of all the 3 serotypes. CONCLUSION: Migrants as a significant source of poliovirus detection may be an indicator group for detection of signs of unfavorable epidemic situation. Based on the results of epidemiologic surveillance of migrants the fact of import of wild poliovirus into North-West of Russia with the absence of poliomyelitis was proven, which confirms an important role of this form of monitoring in the system of poliomyelitis control.

[Control of poliomyelitis and enterovirus infection in several areas of Russian Federation].

AIM: Control of poliovirus circulation by study of material from patients with acute flaccid paralysis and contact individuals, from children of risk groups; molecular characteristics of isolated polioviruses; monitoring of circulation of polioviruses and nonpoliomyelitis enteroviruses in population and the environment. MATERIALS AND METHODS: Isolation and study of polioviruses and nonpoliomyelitis enteroviruses from various sources was performed in accordance with WHO recommendations. RESULTS: Prolonged persistence and circulation of vaccine related strains of polioviruses in children is demonstrated. Enterovirus serotypes that circulate in the population and the environment more frequently are determined. CONCLUSION. Long term control of poliomyelitis and acute flaccid paralysis in combination with additional control variants in children from risk groups and objects of the environment allowed to obtain valuable data on poliovirus and nonpoliomyelitis enteroviruses circulation for the Program of eradication of poliomyelitis.

[Characterization of vaccine polioviruses isolated in the closed pediatric collective bodies (children's homes)].

Examination of 281 healthy vaccinees from 6 children's homes could isolate 37 vaccine polioviruses. The detection rate for polioviruses in the children's homes, in which there were children born to HIV-positive mothers, was significantly higher than that in other children's homes. These children's homes showed the longest poliovirus excretion after vaccination. The RFLP analysis showed that 40% of the strains being examined were intertypic recombinant strains. The sequence analysis demonstrated that about 30% of the strains under study had a small number of nucleotide substitutions in the VP3-VP1 genomic region. The study revealed a correlation between the dynamics of poliovirus excretion after oral vaccination and the kinetics of formation of recombinant poliovirus strains.

Spread of vaccine-derived poliovirus from a paralytic case in an immunodeficient child: an insight into the natural evolution of oral polio vaccine.

Sabin strains used in the manufacture of oral polio vaccine (OPV) replicate in the human organism and can give rise to vaccine-derived polioviruses. The increased neurovirulence of vaccine derivatives has been known since the beginning of OPV use, but their ability to establish circulation in communities has been recognized only recently during the latest stages of the polio eradication campaign. This important observation called for studies of their emergence and evolution as well as extensive surveillance to determine the scope of this phenomenon. Here, we present the results of a study of vaccine-derived isolates from an immunocompromised poliomyelitis patient, the contacts, and the local sewage. All isolates were identified as closely related and slightly evolved vaccine derivatives with a recombinant type 2/type 1 genome. The strains also shared several amino acid substitutions including a mutation in the VP1 protein that was previously shown to be associated with the loss of attenuation. Another mutation in the VP3 protein resulted in altered immunological properties of the isolates, possibly facilitating virus spread in immunized populations. The patterns and rates of the accumulation of synonymous mutations in isolates collected from the patient over the extended period of excretion suggest either a substantially nonuniform rate of mutagenesis throughout the genome, or, more likely, the strains may have been intratypic recombinants between coevolving derivatives with different degrees of divergence from the vaccine parent. This study provides insight into the early stages of the establishment of circulation by runaway vaccine strains.

Genomic features of intertypic recombinant sabin poliovirus strains excreted by primary vaccinees.

The trivalent oral poliomyelitis vaccine (OPV) contains three different poliovirus serotypes. It use therefore creates particularly favorable conditions for mixed infection of gut cells, and indeed intertypic vaccine-derived recombinants (VdRec) have been frequently found in patients with vaccine-associated paralytic poliomyelitis. Nevertheless, there have not been extensive searches for VdRec in healthy vaccinees following immunization with OPV. To determine the incidence of VdRec and their excretion kinetics in primary vaccinees, and to establish the general genomic features of the corresponding recombinant genomes, we characterized poliovirus isolates excreted by vaccinees following primary immunization with OPV. Isolates were collected from 67 children 2 to 60 days following vaccination. Recombinant strains were identified by multiple restriction fragment length polymorphism assays. The localization of junction sites in recombinant genomes was also determined. VdRec excreted by vaccinees were first detected 2 to 4 days after vaccination. The highest rate of recombinants was on day 14. The frequency of VdRec depends strongly on the serotype of the analyzed isolates (2, 53, and 79% of recombinant strains in the last-excreted type 1, 2, and 3 isolates, respectively). Particular associations of genomic segments were preferred in the recombinant genomes, and recombination junctions were found in the genomic region encoding the nonstructural proteins. Recombination junctions generally clustered in particular subgenomic regions that were dependent on the serotype of the isolate and/or on the associations of genomic segments in recombinants. Thus, VdRec are frequently excreted by vaccinees, and the poliovirus replication machinery requirements or selection factors appear to act in vivo to shape the features of the recombinant genomes.

[The biological characteristics of Shigella flexneri strains circulating in Saint Petersburg in 1992-1994]. / Biologicheskaia kharakteristika shtammov Shigella flexneri, tsirkulirovavshikh v Sankt-Peterburge v 1992--1994 gg.

S.flexneri 2a strains isolated in 1992-1994 from 371 patients in sporadic cases, from 90 patients and their contacts in cases of group diseases and from 71 lethal cases of Flexner's dysentery, were studied in comparison with strains isolated in 1980s. The study revealed the biological heterogeneity of S.flexneri 2a strains. The circulation of 3 enzymatic variants and 11 variants differing in their sensitivity to colicins from Frederick's collection was established. The overwhelming majority of strains circulating in 1990s were resistant to 6-7 antibiotics, while the strains isolated in 1980s were resistant only to 4 of these antibiotics. The strains under study possessed antilysozyme activity, as well as pronounced invasive properties. The circulation of the population of multiresistant strains in the city could affect the course of present-day Flexner's dysentery and their domination in the ecological structure of Shigella infections.

[The epidemiological characteristics of Sonne and Flexner dysentery in St. Petersburg in 1953-1994]. / Epidemiologicheskie osobennosti dizenterii Zonne i Fleksnera v S.-Peterburge v 1953--1994 gg.

In connection with the growth of mortality in Flexner's dysentery observed since 1991 and a rise in morbidity in this infection since 1993 the data on the registered cases of Shigella flexneri and Shigella sonnei infections in St. Petersburg for the period of 1953-1994 were analyzed. In the 60-80s the specific features of the epidemic process was determined by S. sonnei infection which constituted up to 90% of all documented cases of dysentery. Flexner's dysentery lost the character of a mass epidemic disease in the 60s, but in the 70s became again capable of epidemic spread, which was testified by annual seasonal rises producing a half of all cases registered per annum and two rises with peaks in 1975 and 1984. In 1991-1992 the tenfold rise of morbidity in Flexner's dysentery took place in the presence of a common level of morbidity of Shigella infections. In 1993-1994 an essential change in the etiological structures of Shigella infections was observed: morbidity in Flexner's dysentery rose 6 times and morbidity in Sonne dysentery dropped 3 times, which was probably due to socio-economical changes in the living conditions of the population during recent years.

[Interrelation of the enterotoxigenic properties and the antigenic structure of Escherichia]. / O vzaimosviazi énterotoksigennykh svoistv i antigennoi struktury ésherikhii.

The enzymatic signs and serological characteristics of Escherichia enterotoxigenic strains isolated from patients with acute intestinal diseases and from healthy persons were studied. The cultures were subdivided into 24 enzymatic variants and classified with 48 serogroups and 61 serovars. The enterotoxigenic properties of the strains were compared with their serological characteristics and enzymatic signs. The strains, isolated from different persons and classified with the same serovar, belonged to the same variant with respect to the type of enterotoxin they produced (only thermostable enterotoxin, only thermolabile enterotoxin, or both), were similar in the degree of their toxigenicity and belonged, as a rule, to the same enzymatic variant. The data on the presence of manifest interrelation between the enteropathogenicity of Escherichia and their structure, as well as on the stability of the enterotoxigenic properties of these organisms, indicate that in acute intestinal diseases the determination of Escherichia enterotoxigenic strains can be carried out by common bacteriological techniques with the use of specific agglutinating sera.

[Biological properties of enterotoxigenic Escherichia isolated from patients with acute intestinal diseases of unknown etiology]. / Biologicheskie svoistva énterotoksigennykh ésherikhii, vydelennykh ot bol'nykh ostrymi kishechnymi zabolevaniiami neustanovlennoi étiologii.

As the result of the comparative examination of adult patients with acute enteric diseases and normal adults, 173 E. coli enterotoxigenic strains were isolated (161 strains from the patients and 12 strains from normal persons). 83% of the isolated enterotoxigenic E. coli (ETEC) produced two enterotoxins: thermolabile (LT) and thermostable (ST). Enterotoxigenicity was most pronounced in the strains of ETEC belonging to the prevaling variant ST + LT +. The enterotoxigenic properties of ETEC were highly stable: the production of ST and LT in the strains remained unchanged after their storage for up to 4 years. The isolated ETEC comprised 48 serogroups and 61 strains. The strains belonging to the same seroval had a similar degree of toxigenicity. The strains belonging to different serovars considerably differed in the activity of their enterotoxins. The production of two kinds of enterotoxins in the isolated E. coli strains was inter-related: the strains with a high activity of ST were, as a rule, good producers of LT.

[Use of stationary-growth broth cultures for obtaining Escherichia enterotoxins. II. Study of Escherichia preparations isolated from diarrhea patients]. / Primenenie statsionarno vyrashchennykh bul'onnykh kul'tur dlia polucheniia énterotoksinov ésherikhii. Soobshchenie II. Izuchenie preparatov iz esherikhii, vydelennykh uz bol'nykh diareiami.

The preparation, simple in manufacture and consisting of the supernatant fluid (SF) of 48-hour cultures grown in flasks with Hottinger's broth without shaking, was shown to be suitable for the detection of enterotoxigenic E. coli (ETEC) in diarrhea patients. SF of the cultures of 1206 E. coli strains isolated from 809 adults, together with control preparations, were studied by means of anal test in suckling mice, used to detect thermostable enterotoxin (TSE), and the paw edema test, used to detect thermolabile enterotoxin (TLE). These SF contained highly active TSE and having specific action. The use of SF ensured the high frequency of ETEC detection in patients with different intestinal diseases (in 262 out of 430 patients), placed in the same hospital. The specificity of these results and the relation of the isolated ETEC to the diseases diagnosed in the patients were confirmed by the fact that the frequency of ETEC detection was significantly less in healthy persons (in 22 out of 242 subjects).

[Detection of enterotoxigenic Escherichia in patients with diarrhea of undetermined etiology using experimental models]. / Vyiavlenie énterotoksigennykh ésherikhii u bol'nykh diareei neustanovlennoi étiologii s pomoshch'iu éksperimental'nykh modelei.

Feces from 249 adult patients hospitalized due to diarrhea of unknown etiology were investigated. In 65.5% of the patients enterotoxic E. coli (ETEC) producing thermostable enterotoxin were detected by the anal test in suckling mice. As demonstrated by the paw edema test in mice, 79% of such strains produced also thermolabile enterotoxin, the remaining strains belonged to the ETEC variants, known from the literature, producing only thermostable enterotoxin. The antigenic similarity of the thermolabile enterotoxin with cholerogen was confirmed by the phenomenon of paw edema neutralization in mice. Among the cultures isolated from the patients 2 ETEC variants, which could not be differentiated by the test in suckling mice and by the paw edema test in mice and paw edema neutralization, were detected by the intranasal infection of mice.

[Mechanism of action of secretory IgA antibodies]. / O mekhanizme deistviia sekretornykh IgA-antitel.

The antiadsorptive capacity of secretory IgA to Sh. sonnei was revealed in experiments with Shigella keratoconjunctivitis used as a model. In patients with dysentery caused by Sh. sonnei IgA in coprofiltrates proved to have greater capacity for agglutinating the antigen than serum IgA. The presence of IgA as coproantibodies in these patients sharply decreased the frequency of diagnostic seroconversions. The importance of the above-mentioned properties of SIgA for diagnosis and for protection from infections affecting the organs and tissue coming into contact with the environment are discussed.