title: Heterologous prime-boost-boost immunisation of Chinese cynomolgus macaques using DNA and recombinant poxvirus vectors expressing HIV-1 virus-like particles.
abstract: BACKGROUND
  There is renewed interest in the development of poxvirus vector-based HIV vaccines due to the protective effect observed with repeated recombinant canarypox priming with gp120 boosting in the recent Thai placebo-controlled trial. This study sought to investigate whether a heterologous prime-boost-boost vaccine regimen in Chinese cynomolgus macaques with a DNA vaccine and recombinant poxviral vectors expressing HIV virus-like particles bearing envelopes derived from the most prevalent clades circulating in sub-Saharan Africa, focused the antibody response to shared neutralising epitopes.
  
  
  METHODS
  Three Chinese cynomolgus macaques were immunised via intramuscular injections using a regimen composed of a prime with two DNA vaccines expressing clade A Env/clade B Gag followed by boosting with recombinant fowlpox virus expressing HIV-1 clade D Gag, Env and cholera toxin B subunit followed by the final boost with recombinant modified vaccinia virus Ankara expressing HIV-1 clade C Env, Gag and human complement protein C3d. We measured the macaque serum antibody responses by ELISA, enumerated T cell responses by IFN-γ ELISpot and assessed seroneutralisation of HIV-1 using the TZM-bl β-galactosidase assay with primary isolates of HIV-1.
  
  
  RESULTS
  This study shows that large and complex synthetic DNA sequences can be successfully cloned in a single step into two poxvirus vectors: MVA and FPV and the recombinant poxviruses could be grown to high titres. The vaccine candidates showed appropriate expression of recombinant proteins with the formation of authentic HIV virus-like particles seen on transmission electron microscopy. In addition the b12 epitope was shown to be held in common by the vaccine candidates using confocal immunofluorescent microscopy. The vaccine candidates were safely administered to Chinese cynomolgus macaques which elicited modest T cell responses at the end of the study but only one out of the three macaques elicited an HIV-specific antibody response. However, the antibodies did not neutralise primary isolates of HIV-1 or the V3-sensitive isolate SF162 using the TZM-bl β-galactosidase assay.
  
  
  CONCLUSIONS
  MVA and FP9 are ideal replication-deficient viral vectors for HIV-1 vaccines due to their excellent safety profile for use in humans. This study shows this novel prime-boost-boost regimen was poorly immunogenic in Chinese cynomolgus macaques.
authors: Clinical Research Group, Liverpool School of Tropical Medicine, Liverpool, UK.
authors: Simon H
authors: SH
authors: Bridge
authors: Sally A
authors: SA
authors: Sharpe
authors: Mike J
authors: MJ
authors: Dennis
authors: Stuart D
authors: SD
authors: Dowall
authors: Brian
authors: B
authors: Getty
authors: Donald S
authors: DS
authors: Anson
authors: Michael A
authors: MA
authors: Skinner
authors: James P
authors: JP
authors: Stewart
authors: Tom J
authors: TJ
authors: Blanchard
mesh_terms: D016915:AIDS Vaccines / Q000008:administration & dosage* / Q000737:chemistry / Q000235:genetics; D000818:Animals; D015478:Antigens, Heterophile / Q000008:administration & dosage; D004247:DNA; D005587:Fowlpox virus / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D015683:Gene Products, gag / Q000235:genetics / Q000276:immunology; D005822:Genetic Vectors / Q000008:administration & dosage / Q000737:chemistry / Q000276:immunology; D015483:HIV Antibodies / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology; D015699:HIV Envelope Protein gp120 / Q000235:genetics / Q000276:immunology; D015658:HIV Infections / Q000235:genetics / Q000276:immunology / Q000517:prevention & control*; D015497:HIV-1 / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D006801:Humans; D007117:Immunization, Secondary; D007273:Injections, Intramuscular; D008252:Macaca fascicularis / Q000276:immunology* / Q000821:virology; D008297:Male; D016865:Reassortant Viruses / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D014611:Vaccination; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000737:chemistry / Q000235:genetics; D058425:Vaccines, Virus-Like Particle / Q000008:administration & dosage / Q000737:chemistry / Q000235:genetics; D014616:Vaccinia virus / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D001616:beta-Galactosidase / Q000032:analysis; D054299:env Gene Products, Human Immunodeficiency Virus / Q000235:genetics / Q000276:immunology
chemical_list: D016915:AIDS Vaccines; D015478:Antigens, Heterophile; D015683:Gene Products, gag; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120; D019444:Vaccines, DNA; D058425:Vaccines, Virus-Like Particle; D054299:env Gene Products, Human Immunodeficiency Virus; D004247:DNA; D001616:beta-Galactosidase