Non-Polio Enteroviruses Isolated by Acute Flaccid Paralysis Surveillance Laboratories in the Russian Federation in 1998-2021: Distinct Epidemiological Features of Types

More than 100 types of non-polio enteroviruses (NPEVs) are ubiquitous in the human population and cause a variety of symptoms ranging from very mild to meningitis and acute flaccid paralysis (AFP). Much of the information regarding diverse pathogenic properties of NPEVs comes from the surveillance of poliovirus, which also yields NPEV. The analysis of 265 NPEV isolations from 10,433 AFP cases over 24 years of surveillance and more than 2500 NPEV findings in patients without severe neurological lesions suggests that types EV-A71, E13, and E25 were significantly associated with AFP. EV-A71 was also significantly more common among AFP patients who had fever at the onset and residual paralysis compared to all AFP cases. In addition, a significant disparity was noticed between types that were common in humans (CV-A2, CVA9, EV-A71, E9, and E30) or in sewage (CVA7, E3, E7, E11, E12, and E19). Therefore, there is significant evidence of non-polio viruses being implicated in severe neurological lesions, but further multicenter studies using uniform methodology are needed for a definitive conclusion.

Anti-Salmonella Defence and Intestinal Homeostatic Maintenance In Vitro of a Consortium Containing Limosilactobacillus fermentum 3872 and Ligilactobacillus salivarius 7247 Strains in Human, Porcine, and Chicken Enterocytes

Limosilactobacillus fermentum strain 3872 (LF3872) was originally isolated from the breast milk of a healthy woman during lactation and the breastfeeding of a child. Ligilactobacillus salivarius strain 7247 (LS7247) was isolated at the same time from the intestines and reproductive system of a healthy woman. The genomes of these strains contain genes responsible for the production of peptidoglycan-degrading enzymes and factors that increase the permeability of the outer membrane of Gram-negative pathogens. In this work, the anti-Salmonella and intestinal homeostatic features of the LF3872 and LS7247 consortium were studied. A multi-drug resistant (MDR) strain of Salmonella enteritidis (SE) was used in the experiments. The consortium effectively inhibited the adhesion of SE to intact and activated human, porcine, and chicken enterocytes and reduced invasion. The consortium had a bactericidal effect on SE in 6 h of co-culturing. A gene expression analysis of SE showed that the cell-free supernatant (CFS) of the consortium inhibited the expression of virulence genes critical for the colonization of human and animal enterocytes. The CFS stimulated the production of an intestinal homeostatic factor-intestinal alkaline phosphatase (IAP)-in Caco-2 and HT-29 enterocytes. The consortium decreased the production of pro-inflammatory cytokines IL-8, TNF-α, and IL-1β, and TLR4 mRNA expression in human and animal enterocytes. It stimulated the expression of TLR9 in human and porcine enterocytes and stimulated the expression of TLR21 in chicken enterocytes. The consortium also protected the intestinal barrier functions through the increase of transepithelial electrical resistance (TEER) and the inhibition of paracellular permeability in the monolayers of human and animal enterocytes. The results obtained suggest that a LF3872 and LS7247 consortium can be used as an innovative feed additive to reduce the spread of MDR SE among the population and farm animals.

Ligilactobacillus salivarius 7247 Strain: Probiotic Properties and Anti-Salmonella Effect with Prebiotics

The Ligilactobacillus salivarius 7247 (LS7247) strain, originally isolated from a healthy woman's intestines and reproductive system, has been studied for its probiotic potential, particularly against Salmonella Enteritidis (SE) and Salmonella Typhimurium (ST) as well as its potential use in synbiotics. LS7247 showed high tolerance to gastric and intestinal stress and effectively adhered to human and animal enterocyte monolayers, essential for realizing its probiotic properties. LS7247 showed high anti-Salmonella activity. Additionally, the cell-free culture supernatant (CFS) of LS7247 exhibited anti-Salmonella activity, with a partial reduction upon neutralization with NaOH (p < 0.05), suggesting the presence of anti-Salmonella factors such as lactic acid (LA) and bacteriocins. LS7247 produced a high concentration of LA, reaching 124.0 ± 2.5 mM after 48 h of cultivation. Unique gene clusters in the genome of LS7247 contribute to the production of Enterolysin A and metalloendopeptidase. Notably, LS7247 carries a plasmid with a gene cluster identical to human intestinal strain L. salivarius UCC118, responsible for class IIb bacteriocin synthesis, and a gene cluster identical to porcine strain L. salivarius P1ACE3, responsible for nisin S synthesis. Co-cultivation of LS7247 with SE and ST pathogens reduced their viability by 1.0-1.5 log, attributed to cell wall damage and ATP leakage caused by the CFS. For the first time, the CFS of LS7247 has been shown to inhibit adhesion of SE and ST to human and animal enterocytes (p < 0.01). The combination of Actigen prebiotic and the CFS of LS7247 demonstrated a significant combined effect in inhibiting the adhesion of SE and ST to human and animal enterocytes (p < 0.001). These findings highlight the potential of using the LS7247 as a preventive strategy and employing probiotics and synbiotics to combat the prevalence of salmonellosis in animals and humans caused by multidrug resistant (MDR) strains of SE and ST pathogens.

Antimicrobial resistance of commensal Enterococcus faecalis and Enterococcus faecium from food-producing animals in Russia

Background and Aim:

Although Enterococcus faecalis and Enterococcusfaecium are common members of human and animal gut microbiota, their resistance to different antimicrobials makes them important pathogens. Multidrug-resistant enterococci often contaminate foods of animal origin at slaughterhouses. The World Health Organization and the World Organization for Animal Health recommend including animal-derived enterococci in antimicrobial resistance (AMR) monitoring programs. This study aimed to fill a literature gap by determining the current AMR prevalence of E. faecalis and E. faecium from different food-producing animals in Russia.

Materials and Methods:

Samples of biomaterial were taken from chickens (n=187), cattle (n=155), pigs (n=49), turkeys (n=34), sheep (n=31), and ducks (n=31) raised at 28 farms in 15 regions of Russia. Isolates of E. faecalis (n=277) and of E. faecium (n=210) (487 isolates in total; 1 isolate per sample) were tested for resistance to 12 antimicrobials from 11 classes using the broth microdilution method. Three criteria were used for the interpretation of minimum inhibitory concentration: Epidemiological cutoff values (ECOFFs) from the European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Clinical and Laboratory Standards Institute (CLSI) clinical breakpoints. The AMR cloud online platform was used for data processing and statistical analysis.

Results:

A difference of >10% was found between E. faecalis and E. faecium resistance to several antimicrobials (erythromycin, gentamycin, tetracycline, chloramphenicol, ciprofloxacin, and streptomycin). In total, resistance to most antimicrobials for enterococci isolates of both species taken from turkeys, chicken, and pigs was higher than cattle, sheep, and ducks. The highest levels were found for turkeys and the lowest for ducks. Among antimicrobials, resistance to bacitracin and virginiamycin was 88-100% in nearly all cases. High levels of clinical resistance were found for both bacteria species: Rifampicin (44-84%) from all animals, tetracycline (45-100%) from poultry and pigs, and erythromycin (60-100%), ciprofloxacin (23-100%), and trimethoprim-sulfamethoxazole (33-53%) from chickens, turkeys, and pigs. No vancomycin-resistant isolates were found. Most isolates were simultaneously resistant to one–three classes of antimicrobials, and they were rarely resistant to more than three antimicrobials or sensitive to all classes.

Conclusion:

Differences in resistance between enterococci from different farm animals indicate that antimicrobial application is among the crucial factors determining the level of resistance. Conversely, resistance to rifampicin, erythromycin, tetracycline, and ciprofloxacin found in enterococci from farm animals in our study was notably also found in enterococci from wild animals and birds. Our results may be partly explained by the intrinsic resistance of E. faecium and E. faecalis to some antimicrobials, such as trimethoprim/sulfamethoxazole and bacitracin.

Cases of Acute Flaccid Paralysis Associated with Coxsackievirus A2: Findings of a 20-Year Surveillance in the Russian Federation

Surveillance for acute flaccid paralysis syndrome (AFP) in children under 15 is the backbone of the Global Polio Eradication Initiative. Laboratory examination of stool samples from AFP cases allows the detection of, along with polioviruses, a variety of non-polio enteroviruses (NPEV). The etiological significance of these viruses in the occurrence of AFP cases has been definitively established only for enteroviruses A71 and D68. Enterovirus Coxsackie A2 (CVA2) is most often associated with vesicular pharyngitis and hand, foot and mouth disease. Among 7280 AFP cases registered in Russia over 20 years (2001–2020), CVA2 was isolated only from five cases. However, these included three children aged 3 to 4 years, without overt immune deficiency, immunized with 4–5 doses of poliovirus vaccine in accordance with the National Vaccination Schedule. The disease resulted in persistent residual paralysis. Clinical and laboratory data corresponded to poliomyelitis developing during poliovirus infection. These findings are compatible with CVA2 being the cause of AFP. Molecular analysis of CVA2 from these patients and a number of AFP cases in other countries did not reveal association with a specific phylogenetic group, suggesting that virus genetics is unlikely to explain the pathogenic profile. The overall results highlight the value of AFP surveillance not just for polio control but for studies of uncommon AFP agents.

[Experience of application of IgY-technology for laboratory diagnostics of viral infections.]

INTRODUCTION

The well-known advantages of class Y antibodies (IgY) from egg yolks of immunized hens in comparison with class G antibodies (IgG) of laboratory animals traditionally used in laboratory diagnosis of infectious diseases determine the stable interest of researchers in using IgY for these purposes (IgY technology). Over the past 20 years, the obvious benefits of IgY technology have been demonstrated for a number of viral and bacterial infections. Goals and objectives. Construction of ELISA systems based on specific IgY for laboratory diagnosis of infections caused by tick-borne encephalitis virus, yellow fever virus, poliovirus.

MATERIAL AND METHODS

Obtaining yolk preparations of immunized chickens, obtaining highly purified IgY preparations (salting out, affinity chromatography), constructing ELISA systems for determining virus-specific antigens, testing the parameters of ELISA systems.

RESULTS AND DISCUSSION

For the first time in laboratory practice, ELISA systems based on the use of specific polyclonal IgY were designed for laboratory diagnosis of topical human viral infections caused by flaviviruses and enteroviruses: determination of antigens of tick-borne encephalitis virus, yellow fever virus, 3 types of poliovirus. It was experimentally shown that these ELISA systems have high sensitivity and specificity, which allows them to be used for the semiquantitative and quantitative determination of antigens of these viruses in various materials (infected cell cultures, vaccines, etc.).

CONCLUSION

The ELISA systems developed on the basis of specific IgY for determination of viral antigens can be effectively used for laboratory diagnosis of a number of viral infections, for the validation and control of vaccine preparations.

Antimicrobial resistance of commensal Escherichia coli from food-producing animals in Russia

Background and Aim:

Commensal Escherichia coli is an important indicator of antimicrobial resistance (AMR) in animals and food of animal origin. Therefore, it was recommended by the World Health Organization and OIE for inclusion in resistance surveillance programs. At the same time, the data on E. coli isolates from animals in Russia are scarce. The aim of this work was to determine the current prevalence of resistance and genetic markers of non-pathogenic commensal E. coli collected from major food-producing animals (poultry, pigs, and cows) in different regions of Russia and to compare these data with data from other countries to prioritize antimicrobials for limiting their use according to the National Action Plan

Materials and Methods:

Samples (n=306) were collected from biomaterial of chicken, turkey, cows, and pigs raised on 11 farms in the European part of Russia, Siberia, and North Caucasus. Isolates (n=306) of E. coli were tested for resistance to 11 antimicrobials from ten classes using the broth microdilution method. MICs were interpreted against EUCAST microbiological and clinical breakpoints. For data analysis and statistical processing, the AMRcloud online platform was used. The data are presented in comparison with other countries.

Results:

In Russia, higher levels of microbiological and clinical resistance of E. coli to critically important antimicrobials, including colistin, cefotaxime, and ciprofloxacin, were found compared to other countries, especially in poultry: About 30% of isolates from chicken were resistant to colistin, 8% to cefotaxime, and 88% to ciprofloxacin according to EUCAST ECOFFs. Only 10% of isolates from cows were resistant to cefotaxime. About 47% of isolates of E. coli from chicken had a moderate relative resistance for ampicillin and 56% for tetracycline. For most antimicrobials, isolates from cows demonstrated a lower resistance than isolates from poultry and pigs. All tested isolates from chicken, turkey, and pigs showed a simultaneous microbiological resistance to at least three classes of antimicrobials. No pan-resistant isolates were found.

Conclusion:

High levels of AMR of commensal E. coli from poultry, especially for critically important drugs, are a matter of concern and should be taken into account when choosing antimicrobials to be restricted for use in animal husbandry according to the National Action Plan.

[Development of inactivated cultural yellow fever vaccine]

INTRODUCTION

The only currently available live vaccine against yellow fever (YF) based on chicken embryos infected with an attenuated 17D strain of the YF virus is one of the most effective vaccine preparations. However, the live vaccine is associated with "viscerotropic syndrome" (approximately 0.4 cases per 100 000 vaccinated). Therefore, the development and introduction of highly purified inactivated vaccine against YF is intended to ensure the maximum safety of vaccination against one of the most common human viral diseases.Goals and objectives. Development and evaluation of immunogenicity of the cultural inactivated vaccine against YF at the laboratory model level.

MATERIAL AND METHODS

Adaptation of 17D strain of YF virus to Vero cell culture, cultivation, removal of cellular DNA, inactivation with β-propiolactone, concentration, chromatographic purification, determination of protein and antigen of YF virus, assessment of immunogenicity in mice in parallel with commercial live vaccine.

RESULTS AND DISCUSSION

Immunogenicity: the determination of specific antibodies of class G (IgG) and virus neutralizing antibodies in the sera of immunized mice showed high level of antibodies exceeding that of immunized with commercial live vaccine. The optimal dose of antigen in the vaccine (total protein) was 50 μg/ml (5 μg/0.1 ml -dose and volume per 1 vaccination of mice). Thus, the laboratory version of cultural inactivated vaccine against YF is as effective (and even superior) as the commercial live vaccine.

CONCLUSION

Laboratory version of cultural inactivated vaccine against YF, which is not inferior in immunogenicity (in animal model) to commercial live vaccine, has been developed.

Case of Poliomyelitis Caused by Significantly Diverged Derivative of the Poliovirus Type 3 Vaccine Sabin Strain Circulating in the Orphanage

Significantly divergent polioviruses (VDPV) derived from the oral poliovirus vaccine (OPV) from Sabin strains, like wild polioviruses, are capable of prolonged transmission and neuropathology. This is mainly shown for VDPV type 2. Here we describe a molecular-epidemiological investigation of a case of VDPV type 3 circulation leading to paralytic poliomyelitis in a child in an orphanage, where OPV has not been used. Samples of feces and blood serum from the patient and 52 contacts from the same orphanage were collected twice and investigated. The complete genome sequencing was performed for five polioviruses isolated from the patient and three contact children. The level of divergence of the genomes of the isolates corresponded to approximately 9–10 months of evolution. The presence of 61 common substitutions in all isolates indicated a common intermediate progenitor. The possibility of VDPV3 transmission from the excretor to susceptible recipients (unvaccinated against polio or vaccinated with inactivated poliovirus vaccine, IPV) with subsequent circulation in a closed children’s group was demonstrated. The study of the blood sera of orphanage residents at least twice vaccinated with IPV revealed the absence of neutralizing antibodies against at least two poliovirus serotypes in almost 20% of children. Therefore, a complete rejection of OPV vaccination can lead to a critical decrease in collective immunity level. The development of new poliovirus vaccines that create mucosal immunity for the adequate replacement of OPV from Sabin strains is necessary.

Mega-plasmid found worldwide confers multiple antimicrobial resistance in Salmonella Infantis of broiler origin in Russia

Plasmids which are the mobile part of the bacterial genome can acquire and carry over genes conferring antimicrobial resistance, thus contributing to rapid adaptation of bacterial community to human-defined environment. In 2014, Israeli scientists have reported a large conjugative mega-plasmid pESI (plasmid for emerging S. Infantis) that provides multiple drug resistance (MDR) of Salmonella Infantis isolated from broilers. Later, very similar pESI-like plasmids have been found in Salmonella isolated from poultry in the United States, Italy, Switzerland, Hungary, and Japan. Here we report detection of pESI-like plasmids in Salmonella Infantis isolated from chicken food products in Russia. Whole genome sequencing of three MDR isolates revealed pESI-like plasmids in all three cases. These plasmids have such typical pESI features as a locus for siderophore yersiniabactin, a cluster of IncI1 conjugative genes, a cluster of type IV pilus genes, and three toxin-antitoxin modules. The pESI-like plasmids carry from two to five resistance genes in each isolate. In total, we observed six antimicrobial resistance genes associated with pESI-like plasmids (aadA1, bla_CTX-M-14, dfrA14, sul1, tetA/tetR, tetM). Besides plasmid genes of antimicrobial resistance, all three MDR isolates of S. Infantis harbor a mutation in chromosomal gene gyrA (p.S83Y or p.D87Y) that is associated with resistance to fluoroquinolones. In addition, we performed a comparative bioinformatics meta-analysis of 25 pESI-like plasmids hosted by S. Infantis from the USA, Europe, Latin America, Israel, and Japan. This analysis identified a 173 kB sequence that is common for all pESI-like plasmids and carries virulence operons and toxin-antitoxin modules.

Vaccine-associated paralytic poliomyelitis in the Russian Federation in 1998-2014

OBJECTIVES

Different polio vaccination schemes have been used in Russia: oral polio vaccine (OPV) was used in 1998-2007 and inactivated polio vaccine (IPV) followed by OPV in 2008-2014. This article presents the characteristics of vaccine-associated paralytic poliomyelitis (VAPP) cases in Russia during this period.

METHODS

VAPP cases were identified through the acute flaccid paralysis surveillance system, classified by the National Expert Classification Committee. Criteria for a 'recipient VAPP' (rVAPP) case were poliomyelitis symptoms 6-30days after OPV administration, isolation of the vaccine virus, and residual paralysis 60days after disease onset. Unvaccinated cases with a similar picture 6-60days after contact with an OPV recipient were classified as 'contact VAPP' (cVAPP) cases.

RESULTS

During 1998-2014, 127 VAPP cases were registered: 82 rVAPP and 45 cVAPP. During the period in which only OPV was used, rVAPP cases prevailed (73.8%); cases of rVAPP were reduced during the sequential scheme period (15%). Poliovirus type 3 (39.5%) and type 2 (23.7%) were isolated more often. Vaccine-derived poliovirus types 1, 2, and 3 were isolated from three cases of cVAPP. The incidence of VAPP cases was higher during the period of OPV use (1 case/1.59 million OPV doses) than during the sequential scheme period (1 case/4.18 million doses).

CONCLUSION

The risk of VAPP exists if OPV remains in the vaccination schedule.

[A case of vaccine-associated paralytic poliomyelitis in an infant]

AIM

To present the clinical history, vaccination status, features of the clinical picture, composition of the cerebrospinal fluid (CSF), results of laboratory and instrumental examinations of a patient with vaccine-associated paralytic poliomyelitis (VAPP).

MATERIAL AND METHODS

In 2017, a child, aged 15 month, mistakenly vaccinated with the first dose of bivalent (types 1 & 3) polioviruses oral vaccine (OPV) was followed up.

RESULTS AND CONCLUSION

Clinical parameters of VAPP in the recipient of OPV are considered. Clinical features of disease caused by wild poliovirus and VAPP are compared. The disease was characterized by sudden onset, recurrence, short (2-4 days) period of progression of paresis, persistent residual effects, CSF protein-cell dissociation. It is emphasized that the occurrence of VAPP cases reflects primarily immunization defects.

Pressure for Pattern-Specific Intertypic Recombination between Sabin Polioviruses: Evolutionary Implications

Complete genomic sequences of a non-redundant set of 70 recombinants between three serotypes of attenuated Sabin polioviruses as well as location (based on partial sequencing) of crossover sites of 28 additional recombinants were determined and compared with the previously published data. It is demonstrated that the genomes of Sabin viruses contain distinct strain-specific segments that are eliminated by recombination. The presumed low fitness of these segments could be linked to mutations acquired upon derivation of the vaccine strains and/or may have been present in wild-type parents of Sabin viruses. These “weak” segments contribute to the propensity of these viruses to recombine with each other and with other enteroviruses as well as determine the choice of crossover sites. The knowledge of location of such segments opens additional possibilities for the design of more genetically stable and/or more attenuated variants, i.e., candidates for new oral polio vaccines. The results also suggest that the genome of wild polioviruses, and, by generalization, of other RNA viruses, may harbor hidden low-fitness segments that can be readily eliminated only by recombination.

Enterovirus A71 Meningoencephalitis Outbreak, Rostov-on-Don, Russia, 2013

Seventy-eight cases of enterovirus infection, including 25 neuroinfections, occurred in Rostov-on-Don, Russia, during May–June 2013. The outbreak was caused by an enterovirus A type 71 (EV-A71) subgenotype C4 lineage that spread to neighboring countries from China ≈3 years earlier. Enterovirus associated neuroinfection may emerge in areas with a preceding background circulation of EV-A71 with apparently asymptomatic infection.

[VACCINE-ASSOCIATED PARALYTIC POLIOMYELITIS IN RUSSIAN FEDERATION DURING THE PERIOD OF CHANGES IN VACCINATION SCHEDULE (2006-2013 yy.)]

The results of virologic testing of clinical materials and epidemiological analysis of vaccine-associated paralytic poliomyelitis (VAPP) cases obtained in 2006-2013 during AFP surveillance are presented. Among the 2976 cases of AFP 30 cases were VAPP. 15 cases were observed in OPV recipients, whereas 15 cases were observed in non-vaccinated contacts. The age of the patients varied from 4 months to 5.5 years (13.6 ± 12.4 months old). Children younger than 1 year constituted 63.3% of the group; boys were dominant (73.3%); 53.3% of children were vaccinated with OPV; the time period between receipt of OPV and onset of palsy was from 2 to 32 days (18.7 ± 8.2). Lower paraparesis was documented in 48.3% of patients; lower monoparesis in 37.9%; upper monoparesis, in 6.9%; tetraparesis with bulbar syndrome, in 6%. The majority of the patients (85.7%) had an unfavorable premorbid status. The violations of the humoral immunity were found in 73.9% cases: CVID (52.9%), hypogammaglobulinemia (41.2%); selective lgA deflciency (5.9%). In 70.6% cases damage to humoral immunity was combined with poor premorbid status. The most frequently observed (76%, p < 0.05) represented the single type of poliovirus--type 2 (44%) and type 3 (32%). All strains were of the vaccine origin, the divergence from the homotypic Sabin strains fell within the region of the gene encoding VPI protein, which did not exceed 0.5% of nucleotide substitutions except vaccine derived poliovirus type 2--multiple recombinant (type 2/type 3/ type 2/type 1) with the degree of the divergence of 1.44% isolated from 6-month old unvaccinated child (RUS08063034001). The frequency of the VAPP cases was a total of 1 case per 3.4 million doses of distributed OPV in 2006-2013; 2.2 cases per 1 million of newborns were observed. This frequency decreased after the introduction of the sequential scheme of vaccination (IPV, OPV) in 2008-2013 as compared with the period of exclusive use of OPV in 2006-2007: 1 case per 4.9 million doses, 1.4 cases per million newborns and 1 case per 1.9 million doses, 4.9 cases per 1 million newborns, respectively. The study has been financed from Russian Federation budget within the framework of the Program for eradication of poliomyelitis in the Russian Federation, WHO Polio eradication initiative, WHO's European Regional Bureau, Russian Foundation for Basic Research (project No. 15-15-00147).

[Prevalence of hepatitis E markers in children]

AIM

Frequency of detection determination for past and current hepatitis E virus (HEV) infection markers in children with immune suppression, as well as children with normal immune status.

MATERIALS AND METHODS

The presence of HEV markers (anti-HEV IgG and IgM, HEV RNA) was studied in 609 sera samples of children with neurologic pathologies, 87 samples--from children with immune deficiencies, as well as 3122 samples from conditionally healthy children of 6 regions of Russia. The children were divided into 5 age groups. Anti-HEV IgG and IgM determination was carried out in EIA, HEV RNA--by RT-PCR.

RESULTS

The frequency of detection of anamnestic anti-HEV IgG turned out to be significantly higher among immune-compromised. children compared with healthy children (5.7% against 1.4%, p < 0.05). Anti-HEV IgM, that testify to current or recent infection, were also detected significantly more frequently among children with immune-suppression (1.1-1.6%) compared with healthy children (0.25%, p < 0.05). HEV RNA was detected in 1 child with the absence of anti-HEV IgM and IgG. Nucleotide sequence analysis of HEV confirmed membership of this isolate in genotype 3, that is prevalent in non-endemic territories.

CONCLUSION

The data obtained have demonstrated, that HEV-infection is prevalent among children in Russia and its course is, probably, asymptomatic in most cases. Immune suppression is a factor of increased risk of infection of children with HEV.

Molecular epidemiology of echoviruses 11 and 30 in Russia: different properties of genotypes within an enterovirus serotype

Over 100 known enterovirus serotypes differ in their epidemiological and pathogenic properties. Much less is known about variation of these features on a sub-serotype level, such as genotypes. Echovirus 11 (E11) and E30 are amongst the most frequent causative agents of aseptic meningitis. We studied the molecular epidemiology of these pathogens to evaluate potential epidemiological and pathogenic dissimilarities of their genotypes. The complete VP1 genome region was sequenced for 97 E11 and 62 E30 isolates collected in Russia from 2008 to 2012, and they were studied in comparison with all 140 E11 and 432 E30 sequences available in GenBank. A geographic pattern of genotype prevalence was observed for both types. Russian E11 isolates belonged mainly to A genotype, which is common in Asia, and D5, which is predominant in Europe. For E30, genotype III by classification of Ke et al. (2011), also termed genotype a by Bailly et al. (2009), was endemic in Russia from 2003 to 2012, while it was not detected in Europe and North America during this time. The E30 genotypes VI-B, VI-G, and VI-H (e, f and h) were regularly introduced from different countries, became predominant and vanished after no more than 4years. In addition to geographic patterns, E11 genotypes also differed by isolation source. Genotype A2 viruses were significantly more often found in sewage, compared to genotype D5 that was isolated from both sewage and human samples. In addition, there was evidence of a different capacity for international transfers among E11 GtA subclusters.

[THE ROLE OF NUTRITION IN THE GENESIS OF-HEPATIC OSTEODYSTROPHY IN PRIMARY BILIARY CIRRHOSIS]

THE PURPOSE

To evaluate the effect of diet on the development of hepatic osteodystrophy in patients with primary biliary cirrhosis.

MATERIALS AND METHODS

In 24 women with PBC, including signs of autoimmune hepatitis (PBC/AIH)--9 persons and 19 women in the control group were analyzed the daily diet, body composition, as well as bone mineral density in the lumbar spine and femur by dual-energy X-ray adsorbtsiometrii (DEXA).

THE RESULTS

In PBC incidence of osteoporosis and severe osteoporosis was 22.7% and 9.1%, respectively, and osteopenia--59.1%, with a lesion predominantly lumbar spine. Inadequate intake of calcium in patients with PBC is associated with lower density of the femur. The high protein content in the diet has a protective effect on bone mineral density, associating with the development of osteopenia.

[Production of the polyclonal enterovirus antibodies of chicken (IgY) and its evaluation as alternative to the rabbit enterovirus neutralizing sera]

Experimental data show the usefulness of the Leghorn chicken as a producer of the enterovirus neutralizing antibodies (IgY). The resulting serum is not inferior to the specific activity of the commercial rabbit enterovirus diagnostic sera (EDS) in the neutralization reaction. The IgY have lower backgrounds than mammalian IgG and do not cause toxic effect to cell culture. Compared with the conventional manufacturing method EDS IgY, preparation process is much more effective: the number of serum producers is significantly lower, whereas the yield of the product is higher. Reduction of the volume of the immunogens, immunization cycle, and number of injections is also an advantage of this manufacturing method.

Poliovirus-Binding Inhibition ELISA for Evaluation of Immune Response to Oral Poliovirus Vaccine: A Possible Alternative to the Neutralization Test

This study describes an ELISA variant (Binding Inhibition ELISA, BI ELISA) for the quantitative determination of neutralization-relevant antibodies to polioviruses. The test differs from previously described analogs by utilizing polyclonal immune reagents: capture antibodies and biotin-labeled detecting antibodies. The BI ELISA was compared with the conventional neutralization test (NT) by testing live Sabin and wild-type poliovirus strains. The comparison of 68 serum samples taken from Oral Poliovirus Vaccine (OPV) recipients showed 100% specificity and sensitivity for Sabin 1 and Sabin 2, and 100% sensitivity and 97% specificity for Sabin 3. Good correlations (r = 0.7, 0.77, 0.65 for Sabin 1, 2, 3, respectively) were demonstrated between the NT and BI ELISA results. These results indicate that the BI ELISA can be used as a reliable alternative to the NT for determination of neutralization-relevant antibodies to polioviruses in vaccinees and in large-scale sero-epidemiological studies.

The 2010 outbreak of poliomyelitis in Tajikistan: epidemiology and lessons learnt

A large outbreak of poliomyelitis, with 463 laboratory-confirmed and 47 polio-compatible cases, took place in 2010 in Tajikistan. Phylogenetic analysis of the viral VP1 gene suggested a single importation of wild poliovirus type 1 from India in late 2009, its further circulation in Tajikistan and expansion into neighbouring countries, namely Kazakhstan, Russia, Turkmenistan and Uzbekistan. Whole-genome sequencing of 14 isolates revealed recombination events with enterovirus C with cross-overs within the P2 region. Viruses with one class of recombinant genomes co-circulated with the parental virus, and representatives of both caused paralytic poliomyelitis. Serological analysis of 327 sera from acute flaccid paralysis cases as well as from patients with other diagnoses and from healthy people demonstrated inadequate immunity against polio in the years preceding the outbreak. Evidence was obtained suggesting that vaccination against poliomyelitis, in rare cases, may not prevent the disease. Factors contributing to the peculiarities of this outbreak are discussed. The outbreak emphasises the necessity of continued vaccination against polio and the need, at least in risk areas, of quality control of this vaccination through well planned serological surveillance.

Recombination strategies and evolutionary dynamics of the Human enterovirus A global gene pool

We analysed natural recombination in 79 Human enterovirus A strains representing 13 serotypes by sequencing of VP1, 2C and 3D genome regions. The half-life of a non-recombinant tree node in coxsackieviruses 2, 4 and 10 was only 3.5 years, and never more than 9 years. All coxsackieviruses that differed by more than 7 % of the nucleotide sequence in any genome region were recombinants relative to each other. Enterovirus 71 (EV71), on the contrary, displayed remarkable genetic stability. Three major EV71 clades were stable for 19-29 years, with a half-life of non-recombinant viruses between 13 and 18.5 years in different clades. Only five EV71 strains out of over 150 recently acquired non-structural genome regions from coxsackieviruses, while none of 80 contemporary coxsackieviruses had non-structural genes transferred from the three EV71 clades. In contrast to earlier observations, recombination between VP1 and 2C genome regions was not more frequent than between 2C and 3D regions.

[An ELISA system based on the specific class Y (IgY) antibodies from egg yolks for the quantitative determination of D-antigen in inactivated poliovirus vaccines]

The results of the construction of the first Russian ELISA system for the quantitative determination of D-antigen of 1-3 poliovirus types in the preparations of inactivated poliovirus vaccines are presented. For the first time, this kind of system is based on the use of specific antibodies of class Y (IgY) from egg yolks of immunized hens. It was shown that this ELISA system is specific, sufficiently sensitive, and can be used for quantitative determination of D-antigen of 1-3 poliovirus types in inactivated poliovirus vaccines.

[Seroepidemiology and molecular epidemiology of enterovirus type 71 in the world and the Russian Federation]

A review of recent publications on epidemiology and seroepidemiology of enterovirus type 71 in various regions of the world and authors' own results of study of seroepidemiology and molecular epidemiology of EV71 in Russia are presented.

[Experience of application of multiplex qPCR for differential diagnostics of intestinal viral infections]

AIM

Evaluate the effectiveness of multiplex reverse transcription (RT) and polymerase chain reaction with fluorescence detection in real time mode (qPCR) methods for differential detection of 11 groups of intestine viruses (adenoviruses, enteroviruses, polioviruses, hepatitis A and E viruses, group A and C rotaviruses, orthoreoviruses, noroviruses, sapoviruses and astroviruses) in various biological samples.

MATERIALS AND METHODS

Panels of virus isolates and clinical samples characterized by reference methods were used to evaluate sensitivity of detection of various intestine viruses. Nucleic acids were isolated from study samples and multiplex RT and qPCR were carried out.

RESULTS

Sensitivity of laboratory reagent kit (LRK) when compared with results obtained from reference methods was 100% for rotavirus A, adenovirus, enterovirus and norovirus, 88.9% for hepatitis E virus and 92.3% for hepatitis A virus, and diagnostic specificity - 99.4%. During analysis of 697 clinical samples from patients with acute intestine infection symptoms nucleic acids of various intestine viruses were isolated in 71.7%.

CONCLUSION

Multiplex qRT-PCR was shown as an effective method of etiologic diagnostics of an intestine viral infection. Use of LRK was demonstrated to establish etiology of intestine diseases in 63 - 72% and in children with watery diarrhea - in approximately 90% of cases.

Adenovirus isolation rates in acute flaccid paralysis patients

Adenoviruses usually cause asymptomatic or mild infection, but occasionally they produce various severe syndromes including neurological disorders. Association of adenovirus infection with acute flaccid paralysis has been investigated. Shedding of adenovirus with feces was detected in 1.05% of young children (mostly infants) with acute flaccid paralysis syndrome versus 0.42% in healthy contact children (P < 0.01). However, 85% of adenoviruses in the pediatric AFP patients belonged to HAdV-C species, which does not have a known neuropathogenic potential. Also, 40% of adenoviruses were isolated from patients with consequently established diagnosis of traumatic neuritis at the discharge, which was not compatible with virus ethology of neurological lesions. Higher adenovirus prevalence in young neurological patients could be affected by an underlying immune deficiency or by congestion in children's hospitals. Indeed, among 70 patients (40 infants, 30 adults) with primary immune deficiencies, asymptomatic shedding of adenoviruses was found in 10-17%; in one adult patient a mixture of HAdV-C2 and HAdV-D15 persisted for several months. Adenoviruses also could be detected in feces of 12% and 57% of healthy young children from two orphanages, respectively. A significant fraction of samples in these groups contained adenovirus mixtures. Therefore, immune deficiencies and congested groups in children's facilities (orphanages and hospitals) could affect significantly the prevalence of adenovirus shedding. The role of adenoviruses in AFP requires further study.

[Poliomyelitis and vaccination strategy in Russian Federation in post-certification period]

Immunization schedules implemented in various countries by using poliovirus vaccines are presented. Approaches to prevent development of vaccine associated paralytic poliomyelitis and risk groups for this infection are discussed. In recent years poliomyelitis morbidity situation in the European region has become more complex, with the example of poliomyelitis outbreak in Tajikistan in 2010. The resulting problem of protection of Russian against emergence and spread of poliomyelitis caused by wild type virus is discussed.

[Social and economic significance of enterovirus infection and its role in etiologic structure of infectious diseases in the world]

Human enteroviruses comprised by more than 100 serotypes, they spread everywhere and can cause wide spectrum of diseases as well as significant social and economic loss. Influenza-like illness and mild forms of enterovirus infection (herpangina, exanthema) are widespread and causes of significant number of visits in clinics. Economic cost of mild form of enterovirus infection is not high although great number of cases (10 - 15 mln cases yearly in USA) determines its important economic significance. Single cases and outbreaks of enterovirus aseptic meningitis occur less frequently but lead to significant economic burden due to hospitalization costs. Enteroviruses are also cause up to 30% of sepsis-like disease in newborns and play important role in infant morbidity and mortality. Potential of enteroviruses as a source of new diseases in humans has a special significance for practical healthcare. In XX century enteroviruses became a cause of pandemics of paralytic poliomyelitis, hemorrhagic conjunctivitis, and foot-and-mouth-like disease, which caused vast social and economic loss, and emergence of new forms of enterovirus infection is quite possible in XXI century.

[Testing of sewage water in orphanage for younger children as a way of surveillance for circulation of polioviruses]

Ability to test sewage water for surveillance on circulation of polioviruses was assessed. Stool samples from children living in orphanage for younger children were collected monthly. Simultaneously, samples of sewage water from orphanage's collector and community collector, in which sewage from neighborhood dwellings is dumped, were collected by snap sample and sorption methods. Rate of isolation of polio--and nonpolioenteroviruses (NPEV) from stool samples for 6 months was 44%; rate of isolation from sewage water for the same period was 79% for sorption method and 50% for snap sample method. Between viruses circulating in orphanage, NPEV of different serotypes predominated (99 isolates out of 170). Domination of polioviruses in isolates from sewage samples obtained by sorption method (23 strains out of 32) can be associated with properties of the sorbent. Number of poliovirus strains and NPEV isolated by snap sample method was equal. Season fluctuations in proportion of stool and sewage samples containing viruses coincided. Comparison of efficacy of the methods during total study period (14 samplings) did not reveal significant difference in rate of virus isolation (in orphanage's collector--72% and 50% for sorption and snap sample collection methods respectively; in community collector--31% for both methods). Detection of type 1 poliovirus with changed antigenic properties in one stool sample and one sewage water sample argue for possibility to detect in sewage minor quantity of virus excreting by one person. Thus testing of sewage water provides information on viruses circulating in the community of children. Study of stool samples revealed high rate of poliovirus isolation (up to 32%) including nonvaccinated children.

[Molecular epidemiology of ECHO 6 virus, the causative agent of the 2006 outbreak of serous meningitis in Khabarovsk]

A total of 3194 cases of enterovirus meningitis were notified in the Russian Federation in 2005, of them there were 1434 cases in the Khabarovsk Territory. Enteroviruses were isolated from 1020 out of the virologically studied 1362 patients from the Khabarovsk Territory. Viruses E6 and E30 were isolated in 80 and 14.7% of cases, respectively. E1, E3, E7, E33, Coxsackie virus B1, B4, B5, and A10 were sporadically detected. The E6 strains isolated in Komsomolsk-on-Amur were identical while E6 strains isolated in Khabarovsk belonged to two different genotypes and greatly differed from those isolated in Konsomolsk-on-Amur. The virus E30 strains isolated in Khabarovsk and Komsomolsk-on-Amur had a 1% difference in VP1 genome nucleotide sequence and belonged to E30 subtype that circulated in Russia and Kazakhstan in 2004-2005.

[Epidemiologic and etiologic characteristic of enterovirus infections in Khabarovsk region]

Results of epidemiologic, virologic, and serologic studies of enterovirus infections in Khabarovsk region from 1975 to 2006 were analyzed. Patterns of epidemic process of these infections were established: periodic change of dominating type of pathogen in the population; onset of the large epidemic peaks of incidence during emergence of circulation of new for the given area serotypes of enteroviruses; possibility of realization of several routes of virus transmission. Role of water factor in the progress of the epidemic process was revealed. Etiology of the large epidemic rise of aseptic meningitis incidence in Khabarovsk region in 2006 was established--the leading pathogens were ECHO viruses serotypes E6 and E30.

[Real-time multiplex PCR for rapid detection of enteroviruses, adenoviruses and hepatitis A virus in clinical specimens]

Real-time multiplex polymerase chain reaction (PCR) with internal positive control (IPC) was developed for simultaneous detection of adenoviruses (AV), enteroviruses (EV) and hepatitis A virus (HAV). Primes and probes labeled with different fluorophores (FAM, R6G, ROX, and Cy5) and able to detect up to four viral RNAs (DNAs) with high specificity in a single tube in real-time PCR were designed. Sensitivity and specificity of the method was estimated using cultural strains of 8 serotypes of EV, 5 serotypes of AV and 2 clinical specimens containing HAV. Sensitivity of the method for detection of polioviruses types 1, 2, and 3 (Sabin vaccine strains) was 0.5--1 TCID50 per reaction mixture. Thirty clinical specimens were analyzed by the multiplex PCR with and without IPC, and by mono-specific PCR. Comparison of these methods with cultural one revealed results agreement in 86.7% in case of multiplex PCR with IPC and in 100% in case of multiplex PCR without IPC and mono-specific PCR. This method can be used for rapid diagnostics of enteric viral infections as well as for determination of viral contamination level of water. As intermediate results of the study the methods for quantitative assessment of HAV, AV, and EV nucleic acids were developed which are convenient tools for the control of antiviral therapy effectiveness.

[Paralytic poliomyelitis in Russian Federation in 1998-2005]

From 1998 through 2005 3,294 cases of acute flaccid paralysis (AFP) including 93 cases with clinical picture of poliomyelitis were registered in Russian Federation. From the latter cases 91 were classified as vaccine-associated paralytic poliomyelitis (VAPP): 66 were VAPP cases in oral poliomyelitis vaccine (OPV) recipients and 25--VAPP cases in contacts. VAPP rate was 1 case per 1.6 million of distributed OPV doses, 1 case per 2.2 million doses for OPV recipients, and 1 case per 186,000 doses for recipients of 1st OPV dose in children aged < 1 year. Majority of VAPP cases in recipients occurred after 1st dose (89.4%) and in contacts--in non-vaccinated children (76%). Mean interval between OPV administration and onset of VAPP in recipients was 21 days. Children aged < 1 year were predominant among VAPP cases (92.4% among recipient VAPP cases, and 80% among contact VAPP cases). Majority of the patients had unfavorable health status including defects of immunity. Most of poliovirus strains isolated from VAPP cases belonged to type 3 (52.9%) whereas to type 2 and 1--29.8% and 17.4% of strains respectively. All VAPP cases were associated with vaccine-derived polioviruses. A highly diverged poliovirus type 1 (2.65% of nucleotide substitutions in VP1 region) was isolated from patient with contact VAPP. Formation of poliovirus-neutralizing serum antibodies in children with VAPP including persons with immunodeficiency reflects the ability of the organism to produce specific antiviral immune response.

[Cellular and humoral immunodeficiency in children with vaccine-associated paralytic poliomyelitis]

Markers of humoral and cellular immunity in 16 patients with vaccine-associated paralytic poliomyelitis (VAPP) were evaluated. Signs of immunodeficiency (decrease of T- and B-lymphocytes counts, impaired synthesis of immunoglobulins, defects of phagocytosis, decrease of NK number) were revealed in all of the patients. Majority of them (81.3%) had defects in humoral immunity. Decrease of CD31, CD4+ and CD8+ was detected in 86.7, 35.7 and 91.7% of the patients respectively. Study of serum immunoglobulins performed in 15 patients showed decrease of IgG, IgM and IgA levels in 6 (40%), 1 (6.7%) and 6 (40%) of the patients respectively. Agammaglobulinemia was diagnosed in one patient in which only trace quantities of IgA and IgG were detected and IgM level was well below the normal. Congenital deficiency of IgA was diagnosed in 3 children. Majority of the children (11 from 12) had comorbidities (frequent respiratory infections, dermatitis, changes of intestinal microflora). Thus, immunocompromised condition of a child is a risk factor for VAPP after administration of alive oral poliovaccine.

[Global eradication of poliomyelitis: intralaboratory contamination with wild poliovirus in the implementation of the program for safe laboratory containment of wild-type polioviruses in the Russian Federation]

The paper describes a case of contamination of sewage samples by a wild poliovirus type 1 strain (Mahoney) in one of the virological laboratories of the Russian Federation. It discusses the possible sources and the mechanism of contamination, as well as the problems in the implementation of the program for safe laboratory containments of wild-type polioviruses.

Antigenic evolution of vaccine-derived polioviruses: changes in individual epitopes and relative stability of the overall immunological properties

The Sabin oral poliovirus vaccine (OPV) readily undergoes changes in antigenic sites upon replication in humans. Here, a set of antigenically altered descendants of the three OPV serotypes (76 isolates) was characterized to determine the driving forces behind these changes and their biological implications. The amino acid residues of OPV derivatives that lie within or close to the known antigenic sites exhibited a marked tendency to be replaced by residues characteristic of homotypic wild polioviruses, and these changes may occur very early in OPV evolution. The specific amino acid alterations nicely correlated with serotype-specific changes in the reactivity of certain individual antigenic sites, as revealed by the recently devised monoclonal antibody-based enzyme-linked immunosorbent assay. In comparison to the original vaccine, small changes, if any, in the neutralizing capacity of human or rabbit sera were observed in highly diverged vaccine polioviruses of three serotypes, in spite of strong alterations of certain epitopes. We propose that the common antigenic alterations in evolving OPV strains largely reflect attempts to eliminate fitness-decreasing mutations acquired either during the original selection of the vaccine or already present in the parental strains. Variability of individual epitopes does not appear to be primarily caused by, or lead to, a significant immune evasion, enhancing only slightly, if at all, the capacity of OPV derivatives to overcome immunity in human populations. This study reveals some important patterns of poliovirus evolution and has obvious implications for the rational design of live viral vaccines.

Recombination in circulating Human enterovirus B: independent evolution of structural and non-structural genome regions

The complete nucleotide sequences of eight Human enterovirus B (HEV-B) strains were determined, representing five serotypes, E6, E7, E11, CVB3 and CVB5, which were isolated in the former Soviet Union between 1998 and 2002. All strains were mosaic recombinants and only the VP2–VP3–VP1 genome region was similar to that of the corresponding prototype HEV-B strains. In seven of the eight strains studied, the 2C–3D genome region was most similar to the prototype E30, EV74 and EV75 strains, whilst the remaining strain was most similar to the prototype E1 and E9 strains in the non-structural protein genome region. Most viruses also bore marks of additional recombination events in this part of the genome. In the 5′ non-translated region, all strains were more similar to the prototype E9 than to other enteroviruses. In most cases, recombination mapped to the VP4 and 2ABC genome regions. This, together with the star-like topology of the phylogenetic trees for these genome regions, identified these genome parts as recombination hot spots. These findings further support the concept of independent evolution of enterovirus genome fragments and indicate a requirement for more advanced typing approaches. A range of available phylogenetic methods was also compared for efficient detection of recombination in enteroviruses.

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.

[Molecular epidemiology of the ECHO 30 virus in Russia and CIS countries]

Nucleotide sequences of the VP1 genome of 28 ECHO 30 strains isolated in 1998-2002 in Russia and several CIS countries were determined. The EV30 studies strain were divided into 4 groups according to isolation place and time. Group 1 is presented by 2 strains isolated in 1998 in Russia and Byelorussia. Group 2 comprises 17 strains isolated in 1999-2000 in Russia (its southern regions and Stavropol Territory), Ukraine, Georgia, and Azerbaijan. Five strains isolated in 2002 in Russia (Kalmykia) belong to Group 3; and Group 4 has 4 strains isolated in 2002 in Moldova and Russia (Magadan). A frequently changing EV30 subtype was simultaneously detected in extensive territories.

[Use of atomic force microscopy for detecting intestinal viruses]

A possibility was demonstrated to use the atomic force microscopy in visualizing and identifying a variety of viruses contained in water samples by their morphological characteristics (shape and size), which was made by the example of 3 model objects, i.e. poliovirus, rotavirus and adenovirus. High-quality AFM images were made and typical sizes (half-height diameter and mean height) were measured for the above objects absorbed in unspecific substrates. Special software was elaborated that automated the object identification procedure and sped up the analysis process.

Recombination in circulating enteroviruses

Recombination is a well-known phenomenon for enteroviruses. However, the actual extent of recombination in circulating nonpoliovirus enteroviruses is not known. We have analyzed the phylogenetic relationships in four genome regions, VP1, 2A, 3D, and the 5' nontranslated region (NTR), of 40 enterovirus B strains (coxsackie B viruses and echoviruses) representing 11 serotypes and isolated in 1981 to 2002 in the former Soviet Union states. In the VP1 region, strains of the same serotype expectedly grouped with their prototype strain. However, as early as the 2A region, phylogenetic grouping differed significantly from that in the VP1 region and indicated recombination within the 2A region. Moreover, in the 5' NTR and 3D region, only 1 strain of 40 grouped with its prototype strain. Instead, we observed a major group in both the 5' NTR and the 3D region that united most (in the 5' NTR) or all (in the 3D region) of the strains studied, regardless of the serotype. Subdivision within that major group in the 3D region correlated with the time of virus isolation but not with the serotype. Therefore, we conclude that a majority, if not all, circulating enterovirus B strains are recombinants relative to the prototype strains, isolated mostly in the 1950s. Moreover, the ubiquitous recombination has allowed different regions of the enterovirus genome to evolve independently. Thus, a novel model of enterovirus genetics is proposed: the enterovirus genome is a stable symbiosis of genes, and enterovirus species consist of a finite set of capsid genes responsible for different serotypes and a continuum of nonstructural protein genes that seem to evolve in a relatively independent manner.

Evaluation of the new control methods for oral poliomyelitis vaccine

In the draft recommendations for production and control of OPV the WHO proposed new control methods: (i) mutant analysis with PCR and restriction enzyme cleavage (MAPREC) assay that allows evaluation of poliovirus population heterogeneity at the molecular level; (ii) neurovirulence (NV) test using transgenic mice susceptible to polioviruses and (iii) control of the seed lots for the presence of the simian virus 40 (SV40) DNA sequence. This paper is focused on our experience in the practical implementation of the new methods at the Institute of Poliomyelitis and Viral Encephalitides (IPVE). Using methods based on PCR we have demonstrated that working seed viruses used by IPVE for OPV production are free from SV40 DNA sequences. Our experience on the conduction of the OPV type 3 control using TgPVR21 mice NV test (seven vaccine lots) and the MAPREC assay (more than 150 samples of single harvests and monovalent bulks) showed that these methods may be used instead of the monkey NV test, because they could not pass the vaccine failed monkey NV test. The necessity for single harvests control is discussed.

Poliomyelitis in Russia in 1998-1999

After introducing surveillance for poliomyelitis and AFP cases in the Russian Federation in 1998, 740 AFP cases have been registered in 1998-1999, and 18 of that number were considered as vaccine-associated paralytic poliomyelitis (VAPP). Of 18 cases 11 were classified as VAPP of vaccine recipients and confirmed by virus isolation; from two of the vaccine recipients virus was not isolated, and five were poliomyelitis cases in contact non-vaccinated children. In all the cases the disease was characterised with the typical clinical picture with residual pareses and paralyses. One case was fatal. Vaccine virus type 3 has been isolated from all the vaccine recipients. The MAPREC test has shown that the quality of monovaccine type 3 bulks used for vaccinating these children did not differ from the quality of other bulk vaccines produced by the Chumakov Institute of Poliomyelitis. Patients surveyed for gammaglobulin were positive. Polioviruses type 1 isolated from two of the contact cases had changed antigenic properties and were recombinants of types 1 and 2.

Outbreak of paralytic poliomyelitis in the Chechen Republic in 1995

An outbreak of poliomyelitis with 146 cases among children of whom six died occurred in the Chechen Republic in 1995. Sporadic cases of poliomyelitis have been reported in the neighbouring Ingush Republic. The outbreak lasted for five months (from May to September) and the maximum number of cases was registered in July. The age of the patients did not exceed 11 years, and more than 90% of the patients were children aged from one month to four years. The overwhelming majority of the patients had not been vaccinated in the routine OPV immunization programme. The outbreak was due to wild poliovirus type 1 belonging to genotype T previously known to circulate in the territory of the former Soviet Union (FSU). Chechen and Ingush isolates were very closely related to each other and to isolates from Central Asia, Tajikistan, 1994. Only a very distant relatedness of the Chechen and Ingush isolates was found with the strains isolated at about the same time outside the FSU (China 1994, Pakistan 1995). The presence of high numbers of non-vaccinated/poorly vaccinated persons and the poor sanitary and hygienic conditions for civilians due to the military conflict were factors that had a role in the outbreak.

Long-term circulation of vaccine-derived poliovirus that causes paralytic disease

Successful implementation of the global poliomyelitis eradication program raises the problem of vaccination against poliomyelitis in the posteradication era. One of the options under consideration envisions completely stopping worldwide the use of the Sabin vaccine. This strategy is based on the assumption that the natural circulation of attenuated strains and their derivatives is strictly limited. Here, we report the characterization of a highly evolved derivative of the Sabin vaccine strain isolated in a case of paralytic poliomyelitis from a 7-month-old immunocompetent baby in an apparently adequately immunized population. Analysis of the genome of this isolate showed that it is a double (type 1-type 2-type 1) vaccine-derived recombinant. The number of mutations accumulated in both the type 1-derived and type 2-derived portions of the recombinant genome suggests that both had diverged from their vaccine predecessors approximately 2 years before the onset of the illness. This fact, along with other recent observations, points to the possibility of long-term circulation of Sabin vaccine strain derivatives associated with an increase in their neurovirulence. Comparison of genomic sequences of this and other evolved vaccine-derived isolates reveals some general features of natural poliovirus evolution. They include a very high preponderance and nonrandom distribution of synonymous substitutions, conservation of secondary structures of important cis-acting elements of the genome, and an apparently adaptive character of most of the amino acid mutations, with only a few of them occurring in the antigenic determinants. Another interesting feature is a frequent occurrence of tripartite intertypic recombinants with either type 1 or type 3 homotypic genomic ends.

[Geotyping of wild poliovirus strains on the territory of Russia and CIS countries in 1987-1995]

33 wild poliovirus strains isolated on the territory of the former USSR were subjected to the comparative sequence analysis of the 150 bp genome fragment VP1/2A on the junction of the genome regions coding basic capsid protein VP1 and viral protease 2A. The dendrograms characterizing the similarity of nucleotide sequences revealed the existence of 3 geographical genotypes (geotypes) of wild poliovirus strains of type 1 (A, G, T) and broad geotype (C) of wild poliovirus strains of type 3. The comparison of the analyzed strains with strains circulating in the neighboring countries at the same period provided information on their genetic relationship. The data thus obtained made it possible to establish the pathways of the transmission of wild poliovirus strains in the common epidemic area of the Russia u CIS.

[Detection of poliomyelitis viral strains in natural isolates and identification of them by polymerase chain reaction]

One hundred and fifty nucleotide-long VP1/2A junction regions were sequenced in the RNAs of 19 strains isolated in 1990-1991 from patients with paralytic poliomyelitis in different regions of the former USSR. On the basis of the alignments of these sequenced RNAs, four pairs of 19-25 base-long oligodeoxynucleotide PCR primers were designed capable of detecting polio RNAs in isolated strains and of discriminating between polio genotypes. PCR with 520 polio virus strains isolated from patients, normal subjects, and environmental objects showed 428 of these strains to be related to Sabin's vaccine strains, whereas the rest were referred to A (30), T (24), and G (1) genotypes of serotype 1 and to C-genotype (37) of serotype 3. The designed primers were highly specific and did not cross-react between themselves and with primers specific for Sabin's vaccine strains in PCR.