Respiratory Infection with Enterovirus Genotype C117, China and Mongolia

To the Editor: Enteroviruses (EVs) are small, nonenveloped viruses of the family Picornaviridae (1). EVs are classified into 12 species according to the molecular and antigenic properties of their viral capsid protein (VP1). To date, 7 species are known to infect humans, including EV-A to EV-D and rhinovirus A, B, and C (http://www.picornastudygroup.com/taxa/species/species.htm)


Respiratory Infection with Enterovirus Genotype C117, China and Mongolia
To the Editor: Enteroviruses (EVs) are small, nonenveloped viruses of the family Picornaviridae (1). EVs are classified into 12 species according to the molecular and antigenic properties of their viral capsid protein (VP1). To date, 7 species are known to infect humans, including EV-A to EV-D and rhinovirus A, B, and C (www.picornastudygroup.com/taxa/ species/species.htm) EV-C117 was a newly found EV-C genotype. It was identified in a nasopharyngeal sample from a hospitalized child, 3 years and 9 months of age, with community-acquired pneumonia in Lithuania in 2012 (2,3). However, aside from this case, little is known about the prevalence and clinical significance of EV-C117. Here, we report the detection of EV-C117 in children in China and Mongolia with respiratory tract infections (RTIs).
During March 2007-March 2013, we screened for EV-C117 in respiratory samples from patients with RTIs in China and Mongolia, including nasopharyngeal aspirates collected from 3,108 children in China who had lower respiratory tract infections when they were admitted to Beijing Children's Hospital (4) and swab samples from 2,516 patients in Mongolia with influenza-like illness (online Technical Appendix Table 1, wwwnc. cdc.gov/EID/article/20/6/13-1596-Techapp1.pdf). Respiratory viruses in samples from China were screened by using multiplex PCR and single PCR assays as described (4). Samples from Mongolia were screened by using the FTD Respiratory Pathogens Multiplex Assay Kit (Fast-track Diagnostics, Luxembourg City, Luxembourg). EVpositive samples were further genotyped by using reverse transcription PCR (RT-PCR) and primers sequentially targeting the VP1 region (5), the 5′-untranslated region (5′-UTR)/VP4/ VP2 region (6) and the 5′-UTR (7). A 394-nt amplicon corresponding to the 5′-UTR of EVs was obtained from 10 children in China; a 598-nt amplicon corresponding to the 5′-UTR/ VP4/VP2 region was obtained by RT-PCR from 5 children in Mongolia. Blastn analysis (www.blast.ncbi. nlm.nih.gov/Blast.cgi) of PCR amplicons showed that only amplicons detected in 2 children from China (patients BCH096A and BCH104A) and 2 children from Mongolia (patients MGL126 and MGL208) had the highest similarity (95%-98%) to the EV-C117 prototype strain LIT22.
Virus isolation for EV-C117 by using Vero and H1-HeLa cells was unsuccessful. Through blastn and phylogenetic analyses, we also found that the previously identified EV-C strain HC90835 (EU697831, from Nepal) (8), EV-C104 strain CL-C22 (EU840734, EU840744, and EU840749, from Switzerland) (9) and a rhinovirus strain SE-10-028 (JQ417886, from South Korea), also belong to EV-C117 ( Figure, panel  A), indicating that EV-C117 is widely distributed geographically. Because a large proportion of EV infections are subclinical or mild (1), the prevalence of EV-C117 should be further estimated by using serologic investigations in general populations.
The VP1 sequences of the EV-C117 strains isolated in China and Mongolia were 89.9%-95.6% (nt) and 95.2%-98.3% (aa) identical to the EV-C117 prototype strain LIT22 (patient JX262382). Alignment analysis of amino acid sequences showed differences between strains isolated in this study and LIT22, i.e., Ser 15 (strains in this study) versus Asn 15 (LIT22). In addition, we found that the strains from patients in China contain Lys 63 and Ala 90 , and those from Mongolia have Thr 93 , Asn 97 , and Ser 276 . The biological significance of these mutations is unknown.
The co-detection of viruses in 2 of the EV-C117-positive patients raises the question of what role EV-C117 plays in RTIs. However, it is notable that EV-C117 was the only virus detected in the other 2 patients. This finding indicates that, at least in patients with low resistance (patient BCH104A had severe bacterial infection before EV-C117 was detected and patient MGL126 had congenital heart disease), EV-C117 might be associated with RTIs. In addition, the strain isolated in Nepal and the strain isolated in Switzerland, EV-C117, were both detected in specimens collected from patients with RTIs (8,9). Collectively, these data indicate the respiratory tropism of EV-C117. Additional epidemiologic and virologic studies on EV-C117 may be warranted to establish its role in RTIs.

Acknowledgments
We thank Lan Chen, Jing Zhang, and Chuluunbaataryn Maitsetseg for their excellent technical assistance. We also thank Caroline Tapparel for helpful suggestions for the PCR detection of EV-C117 strains. We thank the clinicians from Beijing Children's Hospital and General Hospitals in Khan-Uul District, Ulaanbaatar City, Mongolia and Erdenet City, Mongolia for sample collection.