Soile Blomqvist

Co-circulation of coxsackieviruses A6 and A10 in hand, foot and mouth disease outbreak in Finland

BACKGROUND A nationwide outbreak of hand, foot and mouth disease (HFMD) occurred in Finland in autumn 2008. The outbreak was untypical since a considerable number of clinically diagnosed patients were adults. Furthermore, many of the patients suffered from onychomadesis several weeks after the acute phase of HFMD. OBJECTIVES Detection, identification and phylogenetic analysis of human enteroviruses (HEV) that caused the outbreak. STUDY DESIGN A total of 420 clinical specimens were obtained from 317 HFMD cases all over the country. The presence of HEV in the specimens was analysed by virus isolation and/or direct real-time RT-PCR; selected HEV strains were further typed by molecular methods. The genetic similarities of HEV strains were assessed by phylogenetic analyses on partial VP1 sequences. RESULTS HEV were detected in 212 HFMD cases, including both children and adults, throughout Finland. Two HEV types, coxsackieviruses A6 (CV-A6) and A10 (CV-A10), were identified as the causative agents of the outbreak. One genetic variant of CV-A6 predominated, but, additionally, three other genetically distinct CV-A6 strains were found. All CV-A10 strains segregated into one genetic cluster distinct from previously reported CV-A10 sequences. CONCLUSIONS The Finnish 2008 HFMD outbreak was caused by two infrequently detected, co-circulating, coxsackie A viruses. Our data suggest endemic circulation of both CV-A types in Northern Europe and that the outbreak was due to the emergence of new genetic variants of these viruses.

Epidemiology of documented viral respiratory infections and acute otitis media in a cohort of children followed from two to twenty-four months of age.

Background. Viral upper respiratory infections (URIs) are considered major risk factors for acute otitis media (AOM) in young children. We studied the epidemiology and relative roles of different viruses in respiratory infections in a cohort of 329 Finnish children followed from 2 months to 2 years of age. Methods. A nasopharyngeal aspirate (NPA) was collected whenever the child had signs and/or symptoms of URI and tested for the presence of common respiratory virus antigens or infectivity/nucleic acid (only rhinoviruses). Possible repeated detections of a given virus during a 30-day period were considered to represent a single designated virus-specific episode. AOM and URI episodes were defined in a similar way. Results. At least one virus was detected in 837 (41.7%) of the 2005 NPA specimens examined. Rates of URI and virus-specific episodes showed expected seasonal variation with major peak occurrences coinciding with or preceding those of AOM. The proportions of rhinoviruses, respiratory syncytial (RS) virus, parainfluenza virus (PIV) type 3, influenza virus A and adenoviruses were 63.1, 14.7, 6.7, 6.7 and 6.2% of the total of 761 virus-specific episodes. Influenza virus B, PIV1 and PIV2 were each responsible for ∼1% of the episodes. AOM was diagnosed in 870 URI cases (43.4%) and in 43.3% of cases associated with a virus-positive NPA. The latter figure was clearly higher (57.7%) for RS virus-positive specimens. Conclusions. The seasonal coincidence of URI and AOM demonstrated the obvious role of URI in the pathogenesis of AOM. The occurrence of rhinoviruses and RS virus in URI was strikingly more common than that of any other virus tested. Although rhinoviruses were definitely the most frequently found viruses in NPA specimens, the association of RS virus with concurrent AOM was relatively higher than that of any other virus.

Human Rhinovirus 87 and Enterovirus 68 Represent a Unique Serotype with Rhinovirus and Enterovirus Features

ABSTRACT It has recently been reported that all but one of the 102 known serotypes of the genus Rhinovirus segregate into two genetic clusters (C. Savolainen, S. Blomqvist, M. N. Mulders, and T. Hovi, J. Gen. Virol. 83:333-340, 2002). The only exception is human rhinovirus 87 (HRV87). Here we demonstrate that HRV87 is genetically and antigenically highly similar to enterovirus 68 (EV68) and is related to EV70, the other member of human enterovirus group D. The partial nucleotide sequences of the 5′ untranslated region, capsid regions VP4/VP2 and VP1, and the 3D RNA polymerase gene of the HRV87 prototype strain F02-3607 Corn showed 97.3, 97.8, 95.2, and 95.9% identity to the corresponding regions of EV68 prototype strain Fermon. The amino acid identities were 100 and 98.1% for the products of the two capsid regions and 97.9% for 3D RNA polymerase. Antigenic cross-reaction between HRV87 and EV68 was indicated by microneutralization with monotypic antisera. Phylogenetic analysis showed definite clustering of HRV87 and EV68 with EV70 for all sequences examined. Both HRV87 and EV68 were shown to be acid sensitive by two different assays, while EV70 was acid resistant, which is typical of enteroviruses. The cytopathic effect induced by HRV87 or EV68 was inhibited by monoclonal antibodies to the decay-accelerating factor known to be the receptor of EV70. We conclude that HRV87 and EV68 are strains of the same picornavirus serotype presenting features of both rhinoviruses and enteroviruses.

Characterization of a Highly Evolved Vaccine-Derived Poliovirus Type 3 Isolated from Sewage in Estonia

ABSTRACT Two types of vaccine-derived polioviruses have been recently designated to emphasize the different origins of the evolved viruses: circulating vaccine-derived polioviruses (cVDPV) associated with outbreaks of paralytic disease and strains isolated from chronically infected immunodeficient individuals (iVDPV). We describe here a type 3 VDPV (PV3/EST/02/E252; later E252) isolated from sewage collected in Tallinn, Estonia, in October 2002. Due to aberrant properties in subtyping, the virus was subjected to detailed characterization. Partial genomic sequencing suggested that the closest relative was the oral vaccine strain PV3/Sabin, but the two virus strains shared only 86.7% of the 900 nucleotides (nt) coding for the capsid protein VP1. Phylogenetic analysis of the nearly complete genome [nt 19 to poly(A)] revealed multiple nucleotide substitutions throughout the genome and a possible Sabin 3/Sabin 1-recombination junction site in the 2C coding region. A calculation based on the estimated mutation frequency of the P1 region of polioviruses suggested that the E252 virus might have replicated in one or more individuals for approximately 10 years. No persons chronically excreting poliovirus are known in Estonia. Amino acid substitutions were seen in all known antigenic sites, which was consistent with the observed aberrant antigenic properties of the virus demonstrated by both monoclonal antibodies and human sera from vaccinated children. In spite of the apparent transmission potential, no evidence was obtained for circulation of the virus in the Estonian population.

Presence of specific viruses in the middle ear fluids and respiratory secretions of young children with acute otitis media.

The purpose of the study was to investigate the presence of different viruses in middle ear fluids and nasopharyngeal aspirates in young children with acute otitis media. Two cohorts of children (N = 329 and 611) were followed from 2 to 24 months of age in Finland in two prospective studies (Finnish Otitis Media Cohort Study and Finnish Otitis Media Vaccine Trial). During the study period, nasopharyngeal and middle ear fluid specimens for each acute otitis media event were examined for eight (Cohort Study) or ten (Vaccine Trial) common respiratory viruses; adenoviruses, influenza viruses A and B, parainfluenza viruses 1, 2, and 3, respiratory syncytial virus (RSV), enteroviruses, parechoviruses, and rhinoviruses. Picornaviruses (rhinoviruses, enteroviruses, and parechoviruses) were determined by reverse transcription PCR while antigen detection was used for the other viruses. A virus was present in either nasopharyngeal or middle ear specimen in 54% of events in the first cohort and in 67% of events in the second. Rhinoviruses formed the most common virus group detected (41–32%), followed by enteroviruses (25%, sought in the second cohort only) and respiratory syncytial virus (RSV) (10%). All the other viruses represented jointly 8–10% of the events. In conclusion, using the methods described in this study, a specific virus infection was diagnosed in two thirds of all acute otitis media events in young children. Picornavirus RNA was detected in association with more than a half of all acute otitis media events. The use of PCR‐based methods for the other respiratory viruses might have increased further the overall virus detection rate in acute otitis media. J. Med. Virol. 72:241–248, 2004.

Eight Years of Experience with Molecular Identification of Human Enteroviruses

ABSTRACT We have successfully typed 1,121 human enterovirus (HEV) isolates during the last 8 years by adapting partial VP1 sequencing to routine identification of HEV isolated from diverse clinical and environmental specimens. The isolates include 48 of the 59 traditional nonpoliovirus HEV serotypes and members of 8 newly discovered types, which would have remained untypeable by neutralization using the conventional cross-sectional pools of antisera.

Mechanisms of genetic variation in polioviruses

Polioviruses, as with all RNA viruses, are in a constant process of evolution driven by different mechanisms. With multiple mechanisms for genetic variability, they are successful conformists, adapting to changes in their habitat. The evolution of polioviruses may occur with generation of point mutations followed by genetic drift and selection. The mutation rate of polioviruses based on several studies is approximately 3 × 10−2 mutations/synonymous site/year in the gene encoding viral protein 1. Genetic variation in polioviruses may also be increased by sharing of genetic data of two different poliovirus lineages by means of homologous recombination. According to the current view, recombination is considered usually to occur by strand‐switching, but a non‐replicative model has also been described. In recombination, polioviruses may either gain a set of advantageous mutations selected and fixed in previous generations of the parental viruses or get rid of deleterious ones. The prerequisites and constraints of the evolution mechanisms will be discussed. Furthermore, consequences of poliovirus evolution will be reviewed in the light of observations made on currently circulating polioviruses. We will also describe how polioviruses strike back: as wild type polioviruses approach eradication, vaccine derived strains increase their occurrence and genetic variability. Copyright

Sequence and Structure of Human Rhinoviruses Reveal the Basis of Receptor Discrimination

ABSTRACT The sequences of the capsid protein VP1 of all minor receptor group human rhinoviruses were determined. A phylogenetic analysis revealed that minor group HRVs were not more related to each other than to the nine major group HRVs whose sequences are known. Examination of the surface exposed amino acid residues of HRV1A and HRV2, whose X-ray structures are available, and that of three-dimensional models computed for the remaining eight minor group HRVs indicated a pattern of positively charged residues within the region, which, in HRV2, was shown to be the binding site of the very-low-density lipoprotein (VLDL) receptor. A lysine in the HI loop of VP1 (K224 in HRV2) is strictly conserved within the minor group. It lies in the middle of the footprint of a single repeat of the VLDL receptor on HRV2. Major group virus serotypes exhibit mostly negative charges at the corresponding positions and do not bind the negatively charged VLDL receptor, presumably because of charge repulsion.

Novel species of human rhinoviruses in acute otitis media.

We have studied human rhinovirus (HRV) recovered from nasopharyngeal aspirates and middle ear fluids collected during acute otitis media with RT-PCR sequencing followed by phylogenetic analysis. In addition to a great diversity of traditional HRV types we found genetic relatives of the novel HRV species, suggested HRV-C, in both sample types. Our results indicate the presence of HRV-C in the middle ear for the first time.

5' noncoding region alone does not unequivocally determine genetic type of human rhinovirus strains.

During the last couple of years there has been a delightful increase in interest in genetic typing of human rhinoviruses. This is to a large extent due to the discovery of a proposed novel clade, human rhinovirus C (HRV-C). As a consequence, new methods have been reported aiming at unequivocal distinction of traditional HRV prototype strains as well as the newly found uncultivable HRV-C strains. We read with interest the article by Kiang and coworkers (2) describing reverse transcription-PCR-sequencing applications for genetic typing of human rhinoviruses targeting the 5′noncoding region (5′ NCR). A similar approach with largely similar results was published earlier (6). Relatively conserved areas within this region enable broad-spectrum primer design for sensitive methods. However, there are several issues to consider when using the 5′ NCR for genetic typing of HRV. Current taxonomy and classification of picornaviruses are based on capsid region coding sequences. On the basis of this region, a group of previously characterized novel HRV strains form one distinct clade (5, 7) (Fig. ​(Fig.1A),1A), a fact that has also been the basis of the proposal of the Picornavirus Study Group to form a new species, HRV-C, within the Enterovirus genus (4). However, in the article by Kiang et al., on the basis of the partial 5′ NCR sequences, the designated HRV-C strains clustered within the HRV-A clade (2). In contrast, the strains labeled HRV-C in this article formed a clade of their own. As a consequence, because 5′ NCR sequences do not segregate the designated HRV-C from HRV-A (Fig. ​(Fig.1B),1B), they should not be used for typing of new strains. Nevertheless, this region is quite suitable for selected topics of molecular epidemiology, such as analysis of short-term transmission routes (1, 8) or tentative prediction of genetic type as in human enteroviruses (HEV) (9). The sequences nominated as HRV-C by Kiang et al. (2) and by Lee et al. (6) form a new clade in the 5′ NCR. The exact taxonomic position of this clade should be determined according to the clustering of these strains in the capsid region. Clearly, it is divergent from all known HRV and HEV clades in the 5′ NCR, but the decision on whether the strains represent HRV-C or some other picornavirus group cannot be made on the basis of the 5′ NCR alone. FIG. 1. Phylogenetic trees in the VP4/VP2 capsid coding region (A) and in the 5′ NCR (B) of different species of the enterovirus genus showing different clustering of the species in the two regions. Trees were constructed with MEGA4 using the neighbor-joining ... The area close to the beginning of the open reading frame in the 5′ NCR is known to be a recombination hot spot in HEV. Although frequent recombination has not yet been shown for HRV, the analysis of the complete genome sequence data of all HRV prototype strains has not yet been published. Furthermore, the number of completely sequenced genomes of circulating HRV strains has remained low and is too low to conclude that the evolution in the 5′ NCR is always congruent with that of the capsid. Therefore, we would see phylogenetic analysis of the 5′ NCR of HRV as a welcome addition to HRV research, but not a surrogate of capsid coding sequence-based typing.