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Journal of Virology, January 2002, p. 688-696, Vol. 76, No. 2
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.76.2.688-696.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.
nef Vaccine, after Application to the Tonsils of Rhesus Macaques, Replicates Primarily within CD4+ T Cells and Elicits a Local Perforin-Positive CD8+ T-Cell Response
German Primate Center, 37077 Göttingen, Germany,1 Laboratory of Cellular Physiology and Immunology, The Rockefeller University, New York, New York 10021-6399,2 Department of Virology, Biomedical Primate Research Centre, 2288 GJ Rijswijk, The Netherlands,3 Department of Molecular and Medical Virology, Ruhr University, Bochum 44780, Germany,4 Laboratory for Immunological Research, Schering-Plough, 69571 Dardilly, France,5 Department of Pathology and Körber Laboratory for AIDS Research, Bernhard Nocht Institute for Tropical Medicine, 20359 Hamburg, Germany6
Received 2 August 2001/ Accepted 9 October 2001
Deletion of the nef gene from simian immunodeficiency virus (SIV) strain SIVmac239 yields a virus that undergoes attenuated growth in rhesus macaques and offers substantial protection against a subsequent challenge with some SIV wild-type viruses. We used a recently described model to identify sites in which the SIV
nef vaccine strain replicates and elicits immunity in vivo. A high dose of SIV
nef was applied to the palatine and lingual tonsils, where it replicated vigorously in this portal of entry at 7 days. Within 2 weeks, the virus had spread and was replicating actively in axillary lymph nodes, primarily in extrafollicular T-cell-rich regions but also in germinal centers. At this time, large numbers of perforin-positive cells, both CD8+ T cells and CD3-negative presumptive natural killer cells, were found in the tonsil and axillary lymph nodes. The number of infected cells and perforin-positive cells then fell. When autopsy studies were carried out at 26 weeks, only 1 to 3 cells hybridized for viral RNA per section of lymphoid tissue. Nevertheless, infected cells were detected chronically in most lymphoid organs, where the titers of infectious virus could exceed by a log or more the titers in blood. Immunocytochemical labeling at the early active stages of infection showed that cells expressing SIV
nef RNA were CD4+ T lymphocytes. A majority of infected cells were not in the active cell cycle, since 60 to 70% of the RNA-positive cells in tissue sections lacked the Ki-67 cell cycle antigen, and both Ki-67-positive and -negative cells had similar grain counts for viral RNA. Macrophages and dendritic cells, identified with a panel of monoclonal antibodies to these cells, were rarely infected. We conclude that the attenuated growth and protection observed with the SIV
nef vaccine strain does not require that the virus shift its characteristic site of replication, the CD4+ T lymphocyte. In fact, this immunodeficiency virus can replicate actively in CD4+ T cells prior to being contained by the host, at least in part by a strong killer cell response that is generated acutely in the infected lymph nodes.
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