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Journal of Virology, July 2009, p. 6900-6908, Vol. 83, No. 13
0022-538X/09/$08.00+0 doi:10.1128/JVI.00475-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Human Parainfluenza Virus Infection of the Airway Epithelium: Viral Hemagglutinin-Neuraminidase Regulates Fusion Protein Activation and Modulates Infectivity 
Laura M. Palermo,1,
Matteo Porotto,1,
Christine C. Yokoyama,1
Samantha G. Palmer,1
Bruce A. Mungall,1,2
Olga Greengard,1,4
Stefan Niewiesk,3 and
Anne Moscona1*
Department of Pediatrics and of Microbiology and Immunology, Weill Medical College of Cornell University, New York, New York 10021,1 Australian Animal Health Laboratory, CSIRO Livestock Industries, 5 Portarlington Road, Geelong 3220, Australia,2 Department of Veterinary Biosciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio 43210,3 Department of Pediatrics, Mount Sinai School of Medicine, New York, New York4
Received 6 March 2009/ Accepted 14 April 2009
Three discrete activities of the paramyxovirus hemagglutinin-neuraminidase (HN) protein, receptor binding, receptor cleaving (neuraminidase), and triggering of the fusion protein, each affect the promotion of viral fusion and entry. For human parainfluenza virus type 3 (HPIV3), the effects of specific mutations that alter these functions of the receptor-binding protein have been well characterized using cultured monolayer cells, which have identified steps that are potentially relevant to pathogenesis. In the present study, proposed mechanisms that are relevant to pathogenesis were tested in natural host cell cultures, a model of the human airway epithelium (HAE) in which primary HAE cells are cultured at an air-liquid interface and retain functional properties. Infection of HAE cells with wild-type HPIV3 and variant viruses closely reflects that seen in an animal model, the cotton rat, suggesting that HAE cells provide an ideal system for assessing the interplay of host cell and viral factors in pathogenesis and for screening for inhibitory molecules that would be effective in vivo. Both HN's receptor avidity and the function and timing of F activation by HN require a critical balance for the establishment of ongoing infection in the HAE, and these HN functions independently modulate the production of active virions. Alterations in HN's F-triggering function lead to the release of noninfectious viral particles and a failure of the virus to spread. The finding that the dysregulation of F triggering prohibits successful infection in HAE cells suggests that antiviral strategies targeted to HN's F-triggering activity may have promise in vivo.
* Corresponding author. Mailing address: Department of Pediatrics and of Microbiology and Immunology, Weill Medical College of Cornell University, 515 East 71st Street, 6th Floor, New York, NY 10021. Phone: (212) 746-4523. Fax: (212) 746-8117. E-mail: anm2047{at}med.cornell.edu
Published ahead of print on 22 April 2009.
L.M.P. and M.P. contributed equally.
Journal of Virology, July 2009, p. 6900-6908, Vol. 83, No. 13
0022-538X/09/$08.00+0 doi:10.1128/JVI.00475-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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