Human parechovirus types 1, 2 and 3 infections in Canada

Abstract

A new reverse transcription-polymerase chain reaction assay was developed for identification of 28 Canadian human parechovirus (HPeV) isolates, including 20 HPeV-1, 3 HPeV-2, and 5 HPeV-3, recovered from 1985 to 2004. All HPeV-1 isolates but 1 were genetically distinct from the Harris reference strain. One HPeV-2 isolate was related to the Williamson strain; the other 2 were related to the Connecticut strain. HPeV-3 isolates clustered together. Seventy-five percent of isolates were recovered during the typical enterovirus season. All patients but 1 were children with a mean age of 14.6 months, 6.3 months, and 0.7 months for HPeV-1, HPeV-2, and HPeV-3 patients, respectively. All HPeV-2- and HPeV-3-infected children were hospitalized with a diagnosis of viremia or sepsis. HPeV-1- infected children had bronchiolitis diagnosed in 50% of the cases, with few cases of pneumonia and enteritis. Two infected patients (1 child with leukemia and a 78-year-old woman) died of septic shock and severe pneumonia, respectively.

Figure 1

Cytopathic effects (CPEs) observed 3 days after infection of HT-29 cells with an enterovirus or a human parechovirus (HPeV)-1 isolate after 1 passage on this cell line (A); CPE observed 1 day after infection of LLC-MK2 cells with a HPeV-3 isolate after 3 passages on this cell line (B).

Figure 2

Phylogenetic analysis of Canadian human parechovirus (HPeV) isolates and HPeV-1 (Harris, GenBank accession no. S45208), HPeV-2 (Williamson, AJ005695, and Connecticut, AF055846), and HPeV-3 (A308-99, AB084913) reference strains based on the ClustalW alignment of the VP3 amino acid sequences. Japanese HPeV-1 (A1087-99, accession no. AB112485; A942-99, AB112486; and A10987-00, AB112487) and HPeV-3 (A628-99, accession no. AB112484; A317-99, AB112482, and A354-99, AB112483) isolates were also included in the analysis. The tree was constructed by using the neighbor-joining method with the MEGA 2 program. Bootstrap probabilities for 550 replicas are shown at the branch nodes. Only values of 70% to 100% are indicated. Boldface indicates HPeV reference strains.

Figure 3

Comparison of the predicted VP0-VP3 capsid protein region of Canadian isolates with that of Harris (human parechovirus [HPeV]-1), Williamson and Connecticut (HPeV-2), and A308-99 (HPeV-3) strains. The aligned region contains 284 amino acids. corresponding to residues 244 to 521 in the Harris polyprotein sequence (accession no. S45208). The VP3 N-terminal extension, which is specific to parechoviruses (21), is shaded. The cleavage site between VP0 and VP3 is underlined. Asterisks denote conserved residues. Boldface indicates HPeV reference strains.