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J. Virol., May 1996, 3084-3092, Vol 70, No. 5
C Lapham, B Golding, J Inman, R Blackburn, J Manischewitz, P Highet and H Golding
We have previously shown that immunization of mice with human
immunodeficiency virus (HIV)-derived proteins or peptides conjugated to
inactivated Brucella abortus induces the secretion of virus- neutralizing
antibodies, predominantly of the immunoglobulin G2a (IgG2a) isotype. In
addition, B. abortus activates human CD4+ and CD8+ cells to secrete gamma
interferon. Since these are both characteristics of a Th1-type immune
response, which is associated with the development of cell-mediated
immunity, it was important to determine if B. abortus conjugates would also
act as a carrier to induce a cytotoxic T- lymphocyte (CTL) response. To
test this hypothesis, we conjugated an 18- amino-acid peptide from the V3
loop of the MN strain of HIV-1 gp120 that contains both B- and cytotoxic
T-cell epitopes to B. abortus (B. abortus-MN 18-mer). A 10-amino-acid
fragment of this peptide has been shown to be the minimal CTL determinant
presented by murine H-2Dd. It was found that two in vivo immunizations with
10(8) organisms of B. abortus-MN 18-mer followed by in vitro stimulation
with peptide induced a virus-specific CTL response. Conjugation to B.
abortus was required for in vivo priming, since there was no induction of
memory CTLs when B. abortus was only mixed with peptide. Targets pulsed
with peptide as well as those infected with a vaccinia virus encoding HIV
gp160 were killed, demonstrating recognition of naturally processed
envelope. Also, major histocompatibility complex-incompatible L cells which
were infected with vaccinia viruses that encoded H-2Dd, but not H-2Kd, and
pulsed with peptide were lysed. This demonstrated the appropriate major
histocompatibility complex class I restriction. Treatment of the mice with
anti-L3T4 prior to immunization caused a severe depletion of CD4+
lymphocytes, yet it did not decrease the CTL priming. Thus, inactivated B.
abortus can induce non-CD4+ cells to produce the cytokines required for CTL
induction. We conclude that B. abortus stimulates a cellular as well as a
humoral immune response, even in the relative absence of CD4+ helper cells.
It may be a particularly useful vaccine carrier in HIV-1- infected
individuals or others with impaired CD4+ T-cell function.
Copyright © 1996, American Society for Microbiology
Brucella abortus conjugated with a peptide derived from the V3 loop of human immunodeficiency virus (HIV) type 1 induces HIV-specific cytotoxic T-cell responses in normal and in CD4+ cell-depleted BALB/c mice
Laboratory of Retrovirus Research, Division of Viral Products, Center for Biologics Evaluation and Research, U.S. Food and Drug Administration, Bethesda, Maryland 20892, USA.
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