Abstract and Introduction
We isolated six viruses from patients diagnosed with aseptic meningitis or hand, foot, and mouth disease. The cytopathic effect of these viruses on cultured cells was like that of enteroviruses. However, viral neutralization tests against standard antisera were negative. Phylogenetic analysis with the complete VP4 nucleotide sequences of these 6 viruses and 29 serotypes of enteroviruses classified 3 of the viruses as serotype echovirus type 18 (EV18) and 3 as serotype human enterovirus 71 (HEV71). These results were confirmed by remicroneutralization tests with HEV-monospecific antisera or an additional phylogenetic analysis with the complete VP4 nucleotide sequences. Phylogenetic analysis with complete VP4 genes is more useful than neutralization tests with enterovirus serotype-specific antisera in identifying enterovirus serotypes.
The human enterovirus (HEV) genus of the family Picornaviridae includes the human pathogens that cause a wide spectrum of acute disease, including hand, foot, and mouth disease[1], aseptic meningitis[2,3], encephalitis[3,4,5,6], and neonatal sepsislike disease[7,8]. Sixty-four serotypes of HEV have been recognized antigenically by neutralization tests with anti-HEV antibodies[9]. HEVs have long been classified on the basis of serotype-specific antisera in virus neutralization tests[1,10], the only method available for serotyping HEVs. However, virus neutralization is both labor- and time-intensive, and antigenic variants in many serotypes of HEV can affect test results[1].
The HEV genome comprises a 5' nontranslated region (NTR), a long open reading frame that encodes a protein of approximately 2,100 amino acid residues, a short 3' NTR, and a polyadenylated tail. The polyprotein is co- and post-translationally cleaved to yield four structural proteins: VP4, VP2, VP3, and VP1[1]. Recently, attempts have been made to classify the HEV serotypes by using the partial nucleotide sequences of the HEV genomes (i.e., the 5' NTR[11,12,13], the VP4-VP2 junction[14,15,16], and VP1[17,18,19,20]). Methods for molecular classification of HEVs should not only identify the serotypes rapidly but also detect antigenic variant strains or new serotypes. A new serotype of HEV has recently been identified by comparing the complete VP1 nucleotide sequences; its proposed name is HEV73[19].
To investigate the HEV serotypes of six HEV-like viruses that were not neutralized by standard HEV typing sera, we determined the complete VP4 nucleotide sequences of these 6 viruses and 21 HEV antigenically defined serotypes, then performed phylogenetic analysis with another 8 HEV serotypes available from GenBank. The classifications of the untypeable viruses were confirmed by using HEV-monospecific antisera or an additional phylogenetic analysis with the VP4 sequences. The molecular classification of HEV with the complete VP4 sequences is useful for identifying the HEV serotypes.
Emerging Infectious Diseases. 2002;8(3) © 2002 Centers for Disease Control and Prevention (CDC)
Cite this: Molecular Classification of Enteroviruses Not Identified by Neutralization Tests - Medscape - Mar 01, 2002.
