Arch Virol (1998) 143: 2371–2380
Spontaneous release of stable viral double-stranded RNA
into the extracellular medium by inﬂuenza virus-infected MDCK
epithelial cells: implications for the viral acute phase response
J. A. Majde
, N. Guha-Thakurta
, Z. Chen
,and J. M. Krueger
Ofﬁce of Naval Research, Arlington, Virginia, U.S.A.
Department of Physiology and Biophysics, University of Tennessee School of Medicine,
Memphis, Tennessee, U.S.A.
Department VCAPP, College of Veterinary Medicine, Washington State University,
Pullman, Washington, U.S.A.
Center for Molecular Imaging Research, Massachusetts General Hospital,
Charlestown, Massachusetts, U.S.A.
Accepted June 21, 1998
Summary. The viral factor responsible for triggering the acute phase response,
or ‘ﬂu’ syndrome, associated with many acute viral infections is not deﬁned. One
candidate viral factor is double-stranded RNA (dsRNA) generated during viral
replication. In this report we demonstrate by reverse-transcriptase polymerase-
MDCK epithelial cells at the time of cell lysis. Removal of virion-associated
RNA by ultracentrifugation left equal amounts of positive-and negative-strand
viral RNA in the medium that resisted degradation by endogenous RNase in the
medium and by exogenous RNase added prior to phenol extraction. These data
are the ﬁrst demonstration that viral RNA with characteristics of dsRNA is spon-
taneously released from dying inﬂuenza virus-infected cells, and thus is available
to amplify cytokine induction and contribute to systemic disease.
Many acute viral infections are characterized by marked toxic symptoms (the
‘ﬂu’) despite highly localized viral replication. A soluble viral toxin was inten-
sively sought early in the history of virology , but none could be dissociated
from the live virus. Then it was observed in the late 1960s that treatment with
nuclease-stable double-stranded RNA (dsRNA) to induce the antiviral cytokine
interferon (IFN) resulted in a ﬂu-like syndrome . These and other observa-
tions led to the hypothesis  that viruses cause systemic disease by producing