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J Virol, August 1998, p. 6665-6670, Vol. 72, No. 8
Department of Pathology, University of
Massachusetts Medical Center, Worcester, Massachusetts
01655,1 and
Department of Pediatrics,
University of Colorado Health Sciences Center, Denver, Colorado
802622
Received 5 March 1998/Accepted 29 April 1998
Immunoglobulin G (IgG) responses to viruses are generally assumed
to be T-cell dependent (TD). Recently, however, polyomavirus (PyV)
infection of T-cell-deficient (T-cell receptor
0022-538X/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
T-Cell-Independent Immunoglobulin G Responses In
Vivo Are Elicited by Live-Virus Infection but Not by Immunization
with Viral Proteins or Virus-Like Particles
chain [TCR-
]
/
or TCR-
×
/
) mice was shown to elicit a protective,
T-cell-independent (TI) antiviral IgM and IgG response. A repetitive,
highly organized antigenic structure common to many TI antigens is
postulated to be important in the induction of antibody responses in
the absence of helper T cells. To test whether the repetitive structure
of viral antigens is essential and/or sufficient for the induction of
TI antibodies, we compared the abilities of three forms of PyV antigens
to induce IgM and IgG responses in T-cell-deficient mice: soluble
capsid antigens (VP1), repetitive virus-like particles (VLPs), and live
PyV. Immunization with each of the viral antigens resulted in IgM
production. VLPs and PyV elicited 10-fold-higher IgM titers than VP1,
indicating that the highly organized, repetitive antigens are more
efficient in IgM induction. Antigen-specific TI IgG responses, however,
were detected only in mice infected with live PyV, not in VP1- or
VLP-immunized mice. These results suggest that the highly organized,
repetitive nature of the viral antigens is insufficient to account for
their ability to elicit TI IgG response and that signals generated by
live-virus infection may be essential for the switch to IgG production
in the absence of T cells. Germinal centers were not observed in
T-cell-deficient PyV-infected mice, indicating that the germinal center
pathway of B-cell differentiation is TD even in the context of a virus infection.
*
Corresponding author. Mailing address: Department of
Pathology, University of Massachusetts Medical Center, 55 Lake Ave.
North, Worcester, MA 01655. Phone: (508) 856-3039. Fax: (508) 856-5780. E-mail: Eva.Szomolanyi-Tsuda{at}banyan.ummed.edu.
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