Detection and gene characteristics of human bocavirus in acute respiratory tract infection cases in Luohe, Henan

  Objective  To understand the detection and genetic characteristics of human bocavirus (HBoV) in acute respiratory infection cases in Luohe, Henan province.

  Methods  Throat swabs collected from 1185 acute respiratory infection cases in Luohe from June 2018 to December 2020 were used for the nucleic acid detections of multiple common respiratory viruses with quantitative real-time polymerase chain reaction (qRT-PCR). Nest PCR amplification and sequencing of VP1 gene were performed in HBoV nucleic acid positive samples, and the viral gene characteristics were analyzed in combination with Chinese HBoV VP1 gene sequences downloaded from Genbank.

  Results  Among 1185 acute respiratory infection cases, 32 (2.70%) were positive for HBoV; 17 (53.13%) were positive for two or more viruses. Most HBoV-positive cases were children under 5 years old (96.88%, 31/32), the detection rate was highest in children aged 12−23 months (5.52%), followed by infants aged 6−11 months (3.39%). HBoV-positive cases mainly occurred in summer, autumn and winter, the differences in positive rate were not significant among three seasons (P>0.05). HBoV can cause upper or lower respiratory tract infections in both single infection cases and co-infection cases, but the difference in case number was not significant (P>0.05). The 21 HBoV sequences obtained in this study belonged to HBoV1. The strains in Ib branch were predominant in Luohe from 2018 to 2020, consistent with other regions in China. The average molecular evolutionary rate of the VP1 gene was approximately 2.5×10⁻⁴ substitutions/site/year, and there were multiple amino acid variations in the main regions of antigen of HBoV.

  Conclusion  HBoV is one of the important viruses detected in acute respiratory infection cases in Luohe. Children under 5 years old, especially infants/young children under 2 years old, are the susceptible population of HBoV infection. The VP1 gene sequence of HBoV1 in China, including Luohe strain, is relatively conservative, but some amino acid variations have occurred in antigen-related sites.