Enhancement of antibody responses to an HIV-2 DNA envelope vaccine using an expression vector containing a constitutive transport element.
Because immune responses to DNA vaccines in humans remains suboptimal, strategies need to be devised to facilitate expression of the vaccine in vivo. One method to improve response to a DNA vaccine is to construct plasmid vectors with leader sequences and post-transcriptional elements that facilitate export of transcribed RNA. In this study, we sought to determine if a mammalian expression vector (pND-14) containing a tissue plasminogen activator (TPA) leader sequence and a constitutive transport element (CTE) from simian retrovirus was superior to other mammalian expression vectors containing a post-transcriptional regulatory element (PRE) from hepatitis B virus (pCMV-link) or a minimal mammalian expression vector (pVAX1). Toward this objective, we evaluated protein expression of the HIV-2 envelope gene (gp140) in vitro and immune responses in immunized mice. We found that pVAX1 produced three- to fourfold lower levels of gp140 in vitro (5 ng/ml) in contrast to the pCMV-link and pND-14 vectors. When we immunized groups of mice intradermally with two of the HIV-2 gp140 DNA vaccine constructs, we found that pND-14 induced higher levels of envelope-specific systemic and mucosal antibodies than pCMV-link. We conclude that expression vectors for DNA vaccines should contain TPA and CTE sequences to facilitate immune responses.
Locher
Christopher P
CP
Department of Medicine, Division of Hematology and Oncology, University of California, San Francisco, USA. Christopher.locher@maxygen.com
Witt
Stephanie A
SA
Ashlock
Brittany M
BM
Levy
Jay A
JA
D016915:AIDS Vaccines / Q000235:genetics* / Q000276:immunology*; D000818:Animals; D000914:Antibodies, Viral / Q000096:biosynthesis*; D000956:Antigens, Viral / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D001692:Biological Transport; D002460:Cell Line; D005260:Female; D015686:Gene Products, env / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D005822:Genetic Vectors; D015498:HIV-2 / Q000276:immunology*; D018928:Immunity, Mucosal; D051379:Mice; D008807:Mice, Inbred BALB C; D011498:Protein Precursors / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D019444:Vaccines, DNA / Q000235:genetics / Q000276:immunology; D054299:env Gene Products, Human Immunodeficiency Virus
D016915:AIDS Vaccines; D000914:Antibodies, Viral; D000956:Antigens, Viral; D015686:Gene Products, env; D011498:Protein Precursors; D019444:Vaccines, DNA; D054299:env Gene Products, Human Immunodeficiency Virus; C066315:gp140 envelope protein, Human immunodeficiency virus 2