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Journal of Virology, October 2007, p. 10869-10878, Vol. 81, No. 20
0022-538X/07/$08.00+0     doi:10.1128/JVI.00542-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Incorporation of High Levels of Chimeric Human Immunodeficiency Virus Envelope Glycoproteins into Virus-Like Particles

Department of Microbiology and Immunology and Emory Vaccine Center, Emory University School of Medicine, 1510 Clifton Road, Atlanta, Georgia 30322,¹ Departments of Medicine and Microbiology, University of Alabama at Birmingham, 1530 3rd Ave. South, Birmingham, Alabama 35294,² Duke Human Vaccine Institute, Duke University School of Medicine, Durham, North Carolina 27710,³ Novavax, Inc., 9920 Belward Campus Drive, Rockville, Maryland 20850⁴

Received 14 March 2007/ Accepted 21 July 2007

The human immunodeficiency virus (HIV) envelope (Env) protein is incorporated into HIV virions or virus-like particles (VLPs) at very low levels compared to the glycoproteins of most other enveloped viruses. To test factors that influence HIV Env particle incorporation, we generated a series of chimeric gene constructs in which the coding sequences for the signal peptide (SP), transmembrane (TM), and cytoplasmic tail (CT) domains of HIV-1 Env were replaced with those of other viral or cellular proteins individually or in combination. All constructs tested were derived from HIV type 1 (HIV-1) Con-S CFI gp145, which itself was found to be incorporated into VLPs much more efficiently than full-length Con-S Env. Substitution of the SP from the honeybee protein mellitin resulted in threefold-higher chimeric HIV-1 Env expression levels on insect cell surfaces and an increase of Env incorporation into VLPs. Substitution of the HIV TM-CT with sequences derived from the mouse mammary tumor virus (MMTV) envelope glycoprotein, influenza virus hemagglutinin, or baculovirus (BV) gp64, but not from Lassa fever virus glycoprotein, was found to enhance Env incorporation into VLPs. The highest level of Env incorporation into VLPs was observed in chimeric constructs containing the MMTV and BV gp64 TM-CT domains in which the Gag/Env molar ratios were estimated to be 4:1 and 5:1, respectively, compared to a 56:1 ratio for full-length Con-S gp160. Electron microscopy revealed that VLPs with chimeric HIV Env were similar to HIV-1 virions in morphology and size and contained a prominent layer of Env spikes on their surfaces. HIV Env specific monoclonal antibody binding results showed that chimeric Env-containing VLPs retained conserved epitopes and underwent conformational changes upon CD4 binding.

Published ahead of print on 1 August 2007.