Differential susceptibility of different cell lines to swine-origin influenza A H1N1, seasonal human influenza A H1N1, and avian influenza A H5N1 viruses
Received 14 July 2009; received in revised form 27 August 2009; accepted 10 September 2009. published online 05 October 2009.
Abstract
Background
The novel swine-origin influenza A H1N1 virus (S-OIV) causes the current pandemic. Its tissue tropism and replication in different cell lines are not well understood.
Objective
Compare the growth characteristics of cell lines infected by S-OIV, seasonal influenza A H1N1 (sH1N1) and avian influenza A H5N1 (H5N1) viruses and the effect of temperature on viral replication.
Study design
Cytopathic effect (CPE), antigen expression by immunofluorescence (IF) and viral load profile by quantitative RT-PCR in 17 cell lines infected by S-OIV, sH1N1 and H5N1 were examined. Comparison of their replication efficiency in chick embryo was performed. The effect of temperature on viral replication in Madin–Darby canine kidney (MDCK) cells was determined by TCID50 at 33°C, 37°C and 39°C for 5 consecutive days.
Results
S-OIV replicated in cell lines derived from different tissues or organs and host species with comparable viral load to sH1N1. Among 13 human cell lines tested, Caco-2 has the highest viral load for S-OIV. S-OIV showed a low viral load with no CPE or antigen expression in pig kidney cell PK-15, H5N1 demonstrated the most diverse cell tropism by CPE and antigen expression, and the highest viral replication efficiency in both cell lines and allantoic fluid. All three viruses demonstrated best growth at 37°C in MDCK cells.
Conclusion
Cell line growth characteristics of S-OIV, sH1N1 and H5N1 appear to correlate clinically and pathologically with involved anatomical sites and severity. Low replication of S-OIV in PK-15 suggests that this virus is more adapted to human than swine.
aDepartment of Microbiology, Queen Mary Hospital, The University of Hong Kong, Hong Kong, China
bState Key Laboratory of Emerging Infectious Diseases, The University of Hong Kong, Hong Kong, China
Corresponding author at: Carol Yu's Centre for Infection and Division of Infectious Diseases, Department of Microbiology, The University of Hong Kong, Queen Mary Hospital, Pokfulam Road, Pokfulam, Hong Kong, China. Tel.: +852 28553206; fax: +852 28724555.
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