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Journal of Virology, July 2000, p. 6278-6286, Vol. 74, No. 14
Department of Molecular and Cellular Biology,
Centro Nacional de Biotecnología, CSIC, Campus Universidad
Autónoma, E-28049 Madrid, Spain
Received 13 March 2000/Accepted 17 April 2000
We previously demonstrated that codelivery of interleukin-12
(IL-12) with the human immunodeficiency virus type 1 (HIV-1) Env
antigen from a recombinant vaccinia virus (rVV) can enhance the
specific anti-Env cell-mediated immune (CMI) response. In the present
study, we have investigated the effects of IL-12 in mice when it is
expressed in a DNA prime/VV boost vaccine regimen. The delivery of
IL-12 and Env product during priming with a DNA vector, followed by a
booster with VV expressing the Env gene (rVVenv), was found to trigger
the optimal CMI response compared with other immunization schedules
studied. Significantly, if IL-12 is also delivered as a booster from
the viral vector, an impairment of the effects of IL-12 was observed
involving nitric oxide (NO), since it was overcome by specific
inhibitors of inducible NO synthase. NO caused transient
immunosuppression rather than impairment of viral replication.
Moreover, at certain viral doses, coadministration of the NO inhibitor
during the booster resulted in IL-12-mediated enhancement of the
specific CD8+ T-cell response. In addition, the dose of the
IL-12-encoding plasmid (pIL-12) and the route of administration of both
vectors were relevant factors for optimal CMI responses. Maximal
numbers of Env-specific CD8+ gamma interferon-secreting
cells were obtained when 50 µg of pIL-12 was administered
intramuscularly at priming, followed by an intravenous rVVenv boost.
Our results demonstrate, in a murine model, critical parameters
affecting the success of vaccination schedules based on a combination
of DNA and VV vectors in conjunction with immunomodulators.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Interleukin-12 (IL-12) Enhancement of the Cellular
Immune Response against Human Immunodeficiency Virus Type 1 Env
Antigen in a DNA Prime/Vaccinia Virus Boost Vaccine Regimen Is Time and
Dose Dependent: Suppressive Effects of IL-12 Boost Are Mediated by
Nitric Oxide

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Corresponding author. Mailing address: Centro Nacional
Biotecnologia (CSIC), Campus Cantoblanco, 28049 Madrid, Spain. Phone: 34-91-585-4503. Fax: 34-91-585-4506. E-mail:
mesteban{at}cnb.uam.es.
Present address: Department of Applied Microbiology, Centro de
Estudios Farmacológicos y Botánicos (CEFYBO-CONICET),
Buenos Aires, Argentina.
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