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Journal of Virology, February 2001, p. 1507-1515, Vol. 75, No. 3
Unité d'Oncologie Virale, Institut
Pasteur, 75015 Paris,1 and INSERM U74,
Université Louis Pasteur, 67000 Strasbourg,2 France
Received 17 April 2000/Accepted 25 October 2000
Live attenuated simian immunodeficiency virus (SIV) is the most
efficient vaccine yet developed in monkey models of human immunodeficiency virus infection. In all successful vaccine trials, attenuation was achieved by inactivating at least the nef
gene. We investigated some virological and immunological
characteristics of five rhesus macaques immunized with a
nef-inactivated SIVmac251 molecular clone
(SIVmac251
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.3.1507-1515.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Persistence of Pathogenic Challenge Virus in
Macaques Protected by Simian Immunodeficiency Virus
SIVmac
nef
nef) and challenged 15 months later with the
pathogenic SIVmac251 isolate. Three animals were killed 2 weeks
postchallenge (p.c.) to search for the challenge virus and to assess
immunological changes in various organs. The other two animals have
been monitored up for 7 years p.c., with clinical and nef
gene changes being noted. The animals killed showed no increase in
viral load and no sign of a secondary immune response, although the
challenged virus was occasionally detected by PCR. In one of the
monkeys being monitored, the vaccine virus persisted and an additional
deletion occured in nef. In the other monkey that was
monitored, the challenge and the vaccine (
nef) viruses were both detected by PCR until a virus with a hybrid nef
allele was isolated 48 months p.c. This nef hybrid encodes
a 245-amino-acid protein. Thus, our results show (i) that monkeys were
not totally protected against homologous virus challenge but controlled
the challenge very efficiently in the absence of a secondary immune response, and (ii) that the challenge and vaccine viruses may persist
in a replication-competent form for long periods after the challenge,
possibly resulting in recombination between the two viruses.
*
Corresponding author. Mailing address: Unité
d'Oncologie Virale, Département Rétrovirus, Institut
Pasteur, 28 Rue du Dr Roux, 75015 Paris Cedex 15, France. Phone: 33 (1)
40 61 32 65. Fax: 33 (1) 40 61 34 50. E-mail:
ekhatiss{at}pasteur.fr.
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