Thursday, March 30, 2023

Pediatric Bocavirus


Human bocavirus (a member of the Parvoviridae virus family) is a newly described human pathogen that has been associated with lower respiratory tract and gastrointestinal infections, predominantly in children.
It is a very small (approximately 20 nm), nonenveloped virus with a single-stranded negative-sense DNA genome (see following images).

The genome of human bocavirus. The 4 genes are lab

The genome of human bocavirus. The 4 genes are labeled based on their presumed function, according to homologous genes in other parvoviruses. Nonstructural protein 1 (NS1) is a DNA-binding protein involved in gene transcription. NP1 is also nonstructural and is a highly conserved protein of unknown function. The capsid proteins are viral protein 1 (VP1) and viral protein 2 (VP2).

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An electron micrograph of canine parvovirus, which

An electron micrograph of canine parvovirus, which is closely related to human bocavirus.

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It is one of only 2 known human parvovirus pathogens; the other is parvovirus B19, which causes erythema infectiosum (fifth disease or slapped-cheek disease), papular purpuric glove and stocking syndrome (PPGSS), and more serious illnesses such as hydrops fetalis and aplastic crises in people with sickle cell disease. In general, parvoviruses are more important as veterinary pathogens. The Dependovirus adeno-associated virus (AAV) is a small parvovirus that requires a helper co-infection to replicate (either adenovirus or herpes simplex virus) and is not directly associated with a disease in its own right.

There are 4 genetically distinct, but related human bocaviruses. Using advanced molecular techniques, human bocavirus (HBoV) was first isolated in 2005 in upper respiratory secretions of acutely ill children in Sweden.
Analysis of samples from children hospitalized with lower respiratory tract infections and children with acute wheezing episodes has provided infection rates of 2-20% from various areas of the world. The high rate of infection, along with the codetection of other viral pathogens (or simply not ruling out other common virus infections in some studies), has caused some researchers to question whether human bocavirus is a primary cause of disease, a contributor to more severe disease, or simply a passenger virus that is coincidentally found with other infections.

Human bocaviruses 2 and 3 (HBoV2 and HBoV3) were reported in stool specimens from children in 2009 from the United States and Australia.
HBoV2 has been implicated in some cases of acute gastroenteritis
, whereas HBoV3, although detected in stool at low frequencies, has an uncertain role in disease. HBoV4 has also been reported from stool. HBoV1 appears to be a primarily respiratory infection.

Bocavirus was putatively linked to the bovine parvovirus and canine minutevirus by genetic and amino acid sequence similarities. “Bovine” and “canine” lead to the “boca” in bocavirus. One recent report of a culture system using differentiated human epithelial cells has permitted more detailed research of its replication.
A real-time multiplex PCR has been developed.

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