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Viruses 2009, 1(1), 57-71; doi:10.3390/v1010057

More and More Coronaviruses: Human Coronavirus HKU1

1,2,3,†,* , 1,2,3,†,* , 3, 3 and 1,2,3
1 State Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong, China 2 Research Centre of Infection and Immunology, The University of Hong Kong, Hong Kong, China 3 Department of Microbiology, The University of Hong Kong, Hong Kong, China These authors contributed equally to the manuscript
* Authors to whom correspondence should be addressed.
Received: 7 May 2009 / Revised: 6 June 2009 / Accepted: 11 June 2009 / Published: 11 June 2009
(This article belongs to the Special Issue Newly Identified Respiratory Viruses)
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After human coronaviruses OC43, 229E and NL63, human coronavirus HKU1 (HCoV-HKU1) is the fourth human coronavirus discovered. HCoV-HKU1 is a group 2a coronavirus that is still not cultivable. The G + C contents of HCoV-HKU1 genomes are 32%, the lowest among all known coronaviruses with complete genome sequences available. Among all coronaviruses, HCoV-HKU1 shows the most extreme codon usage bias, attributed most importantly to severe cytosine deamination. All HCoV-HKU1 genomes contain unique tandem copies of a 30-base acidic tandem repeat of unknown function at the N-terminus of nsp3 inside the acidic domain upstream of papain-like protease 1. Three genotypes, A, B and C, of HCoV-HKU1 and homologous recombination among their genomes, are observed. The incidence of HCoV-HKU1 infections is the highest in winter. Similar to other human coronaviruses, HCoV-HKU1 infections have been reported globally, with a median (range) incidence of 0.9 (0 – 4.4) %. HCoV-HKU1 is associated with both upper and lower respiratory tract infections that are mostly self-limiting. The most common method for diagnosing HCoV-HKU1 infection is RT-PCR or real-time RT-PCR using RNA extracted from respiratory tract samples such as nasopharyngeal aspirates (NPA). Both the pol and nucleocapsid genes have been used as the targets for amplification. Monoclonal antibodies have been generated for direct antigen detection in NPA. For antibody detection, Escherichia coli BL21 and baculovirus-expressed recombinant nucleocapsid of HCoV-HKU1 have been used for IgG and IgM detection in sera of patients and normal individuals, using Western blot and enzyme-linked immunoassay.
Keywords: coronavirus; human; HKU1; novel coronavirus; human; HKU1; novel
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Woo, P.C.Y.; Lau, S.K.P.; Yip, C.C.Y.; Huang, Y.; Yuen, K.-Y. More and More Coronaviruses: Human Coronavirus HKU1. Viruses 2009, 1, 57-71.

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