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.

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.

[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).

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.

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.

[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.

[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.

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.

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.

[A method of concentrating viruses in environmental water sources]

The authors propose an effective and simple method for the collection and concentration of enteroviruses from environmental water bodies, which is based on adsorption properties of macroporous glass (MPG). MPG enveloped in water-permeable coating permits concentration directly in the water. Poliomyelitis viruses were 100-1000-fold concentrated in laboratory trials. The advantages of the new method in comparison with the routine gauze tampon method were demonstrated in experiments with the indicator virus carried out at sewage works and under field conditions.

Electropherotypes and serotypes of human rotavirus in Estonia in 1989-1992

The electropherotypes and serotypes of human rotaviruses circulating in Tallinn (Estonia) in 1989-1992 have been studied. Rotaviruses were found in 372 (25.8%) of 1,442 faecal specimens of pediatric patients with acute diarrhea. Polyacrylamide gel electrophoresis of RNA from 318 isolates has revealed 41 electropherotypes. Frequent genomic alterations, including a shift of predominant electropherotypes, were observed during the study period. The serotype of 158 (50.3%) of 314 tested rotavirus isolates was identified using ELISA with VP7-specific monoclonal antibodies against 4 established human rotavirus serotypes. Serotype G1 was found to be largely predominant and accounted for 70.9% of the typeable specimens, serotypes G4, G2, and G3 accounted for 12%, 9.5%, 7.6%, respectively. A major shift to serotype G4 took place in 1990-1991. Serotype G1 was represented by the largest number of electropherotypes. All G1, G3 and G4 isolates were of "long" and all G2 isolates were of "short" electropherotypes. According to our results the isolates of an identical electropherotype belong to the same serotype.

Analysis of rotaviral gastroenteritis in Tbilisi

Electrophoretypes of 107 rotaviral isolates collected in Tbilisi for 18 months revealed seven patterns from which 4 were "long" and 3 "short". The "long" electrophoretypes represented 74.8% of total number of the isolates analysed. One of the "long" electrophoretypes dominated for the whole investigation period. Differences in the seasonal distribution of the isolates with various electrophoretypes were demonstrated and appearance of rotaviral isolates was registered with a "short" electrophoretype which had never been detected before.