Protection against lethal simian immunodeficiency virus SIVsmmPBj14 disease by a recombinant Semliki Forest virus gp160 vaccine and by a gp120 subunit vaccine

J Virol. 1996 Mar;70(3):1953-60. doi: 10.1128/JVI.70.3.1953-1960.1996.


Infection of pigtail macaques with SIVsmmPBj14, biological clone 3 (SIV-PBj14-bc13), produces an acute and usually fatal shock-like syndrome 7 to 14 days after infection. We used this simian immunodeficiency virus (SIV) model as a rapid and rigorous challenge to evaluate the efficacy of two SIV Env vaccine strategies. Groups of four pigtail macaques were immunized four times over a 25-week span with either a recombinant Semliki Forest virus expressing the SIV-PBj14 Env gp160 (SFV-SIVgp160) or purified recombinant SIV-PBj14 gp120 (rgp120) in SBN-1 adjuvant. Antibody titers to SIV Env developed in all immunized animals (mean peak titers prior to challenge, 1:1,700 for SFV-SIV gp 160 and 1:10,500 for rgp120), but neither neutralizing antibodies nor SIV-specific T-cell proliferative responses were detectable in any of the vaccinees. All macaques were challenged with a 100% infectious, 75% fatal dose of SIV-PBj14-bc13 at week 26. Three of four control animals died of acute SIV-PBj14 syndrome on days 12 and 13. By contrast, all four SFV-SIVgp160-immunized animals and three of the four rgp120-immunized animals were protected from lethal disease. While all virus-challenged animals became infected, symptoms of the SIV-PBj14 syndrome were more severe in controls than in vaccinees. Mean virus titers in plasma at 13 days postchallenge were approximately 10-fold lower in vaccinated than control animals. However, there was no apparent correlation between survival and levels of peripheral blood mononuclear cell-associated culturable virus, provirus load, or any antiviral immunologic parameter examined. The results indicate that while immunization with SFV-SIVgp160 and rgp120 did not protect against virus infection, these Env vaccines did lower the virus load in plasma and protect against the lethal SIV-PBj14 challenge.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibodies, Viral / immunology
  • Base Sequence
  • CD4 Lymphocyte Count
  • Cell Line
  • Cells, Cultured
  • Cricetinae
  • DNA, Viral
  • Female
  • Gene Products, env / genetics
  • Gene Products, env / immunology*
  • Genetic Vectors / genetics
  • HIV Envelope Protein gp120 / genetics
  • HIV Envelope Protein gp120 / immunology*
  • Humans
  • Immunity, Cellular
  • Macaca nemestrina
  • Membrane Glycoproteins*
  • Mice
  • Molecular Sequence Data
  • SAIDS Vaccines / immunology*
  • Semliki forest virus / genetics
  • Semliki forest virus / immunology*
  • Simian Acquired Immunodeficiency Syndrome / mortality
  • Simian Acquired Immunodeficiency Syndrome / prevention & control*
  • Simian Immunodeficiency Virus / chemistry
  • Simian Immunodeficiency Virus / growth & development
  • Simian Immunodeficiency Virus / immunology*
  • Vaccines, Synthetic / immunology
  • Viral Envelope Proteins*


  • Antibodies, Viral
  • DNA, Viral
  • Gene Products, env
  • HIV Envelope Protein gp120
  • Membrane Glycoproteins
  • SAIDS Vaccines
  • SIV envelope glycoprotein gp160
  • Vaccines, Synthetic
  • Viral Envelope Proteins
  • gp120 protein, Simian immunodeficiency virus