AIDS RESEARCH AND HUMAN RETROVIRUSES Volume 8, Number 8, 1992 Mary Ann Liebert, Inc., Publishers
Immune
Responses to SYVmne Envelope Glycoproteins Protect Macaques from Homologous SIV Infection
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SHIU-LOK HU,1 2 BRUCE M. TRAVIS,1 VIRGINIA STALLARD,2 KRAIG ABRAMS,2 LYNDA MISHER,2 PATRICIA MORAN,1 JOYCE M. ZARLING,1 ALPHONSE J. LANGLOIS,3 LARENE KULLER,2 WILLIAM R. MORTON,2 and RAOUL E. BENVENISTE4
INTRODUCTION
SIMIAN
IMMUNODEFICIENCY
VIRUS
Immunization
(SIV) infection of
macaques has been studied extensively as a model for the development of vaccines against AIDS in humans. To date, only
inactivated whole virus vaccines have been shown to elicit in this model.' The protective immunogen(s) have not been clearly defined. Previous studies indicate that at least partial protection can be achieved by immunization with partially purified viral envelope glycoproteins2 or with fusion proteins containing env sequences.3 Recently, Stott et al.4 and Langlois et al.3 reported that protection appears to correlate with antibodies against cellular antigens present in the vaccine preparations, rather than antiviral antibodies. In this study, we sought to demonstrate that immunization with recombinant vaccines of SIV envelope glycoproteins could protect macaques against homologous SIV infection.
protective immunity
of animals
Four macaques (Macaca fascicularis) of juvenile age were immunized at 0 and 12 weeks with recombinant vaccinia virus V-SE5. The inoculum for the recombinant virus immunizations was a crude lysate of v-SE5-infected BSC-40 cells, containing 1 x 10x plaque-forming units of v-SE5 and the homogenate of approximately 105 infected BSC-40 cells. Inoculations were done by skin scarification at 2 or 3 sites on the midline of the back. At weeks 62 and 70, animals received booster immunizations with SIVm„(, gpl60 produced by insect cells (Spodoptera frugiperda) infected with a recombinant baculovirus (G.N. Barber and S.-L.H., in preparation). The envelope glycoproteins were enriched from detergent lysates of infected cells by lentil lectin chromatography.9 The inoculum contained 0.5 mg of total protein per dose (25-30% of gpl60) and was formulated either in alum (Resoptar, Rorer; final concentration 0.2%) or in Freund's incomplete adjuvant (Difco; 1:1). Inoculations of gpl60 were done by intramuscular injections.
MATERIAL AND METHODS
Construction
of recombinant
Measurement
vaccinia virus
A 2,685 base-pair fragment (from the Xbal site at nucleotide number 5907 to the Bglll site at 8592) of an infectious molecular clone of SIVm„(. (CL 8) (6; R.E.B. and G. Heidecker, in preparation) was inserted between the BamHI and the EcoRI sites of vaccinia recombination plasmid pGS62 [a derivative of pGS207 with a unique EcoRI site downstream from the vaccinia virus 7.5K promoter]. The insert contained the entire coding sequence of the SIV env gene as well as 164 and 318 base-pairs of 5' and 3' untranslated sequences, respectively. The chimeric gene with the vaccinia virus 7.5K promoter and the SIV env sequence was inserted into the thymidine kinase gene of vaccinia virus v-NYK by in vivo homologous recombination as described.7 The recombinant virus (v-SE5) was plaque-purified and propagated on African green monkey kidney (BSC-40) cells.
'Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, "University of Washington, Seattle, WA. 'Duke University Medical Center, Durham, NC.
of immune
responses
against SIV
Methods for measuring lymphoproliferative response and enzyme-linked immunosorbent assays (ELISA) were as previously described,10 with the exception that gradient-purified S'Y,,,,,,. (CL El IS) was used as the antigen. Methods for Western blot analysis was described by Benveniste et al.6 Serum neutralizing assays were performed as described by Langlois " et al., using SIV„I(1