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Journal of Virology, June 2000, p. 5495-5501, Vol. 74, No. 12
Department of Microbiology and The
Immunobiology Vaccine Center, University of Alabama at Birmingham,
Birmingham, Alabama 35294-2170
Received 29 September 1999/Accepted 18 March 2000
Heterosubtypic immunity (HSI) is defined as cross-protection
against influenza virus of a different serotype than the virus initially encountered and is thought to be mediated by influenza virus-specific cytotoxic T lymphocytes (CTL). Since gamma interferon (IFN-
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Gamma Interferon Is Not Required for Mucosal
Cytotoxic T-Lymphocyte Responses or Heterosubtypic Immunity to
Influenza A Virus Infection in Mice
) stimulates cytotoxic cells, including antigen-specific CTL
which may control virus replication by secretion of antiviral cytokines
such as tumor necrosis factor alpha and IFN-
, we have investigated
the mechanism of HSI by analyzing the role of IFN-
for HSI in
IFN-
gene-deleted (IFN-
/
) mice. It has been
reported that IFN-
is not required for recovery from primary
infection with influenza virus but is important for HSI. Here, we
conclusively show that IFN-
is not required for induction of
secondary influenza virus-specific CTL responses in mediastinal lymph
nodes and HSI to lethal influenza A virus infection. Although T helper
2 (Th2)-type cytokines were upregulated in the lungs of
IFN-
/
mice after virus challenge, either Th1- or
Th2-biased responses could provide heterosubtypic protection.
Furthermore, titers of serum-neutralizing and cross-reactive antibodies
to conserved nucleoprotein in IFN-
/
mice did not
differ significantly from those in immunocompetent mice. These results
indicate that lack of IFN-
does not impair cross-reactive
virus-specific immune responses and HSI to lethal infection with
influenza virus. Our findings provide new insight for the mechanisms of
HSI and should be valuable in the development of protective mucosal
vaccines against variant virus strains, such as influenza and human
immunodeficiency virus.
*
Corresponding author. Mailing address: Department of
Microbiology, University of Alabama at Birmingham, Birmingham, AL
35294-2170. Phone: (205) 934-1737. Fax: (205) 934-3894. E-mail:
nghuan{at}uab.edu.
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