title: Selected HIV-1 Env trimeric formulations act as potent immunogens in a rabbit vaccination model.
abstract: BACKGROUND
  Ten to 30% of HIV-1 infected subjects develop broadly neutralizing antibodies (bNAbs) during chronic infection. We hypothesized that immunizing rabbits with viral envelope glycoproteins (Envs) from these patients may induce bNAbs, when formulated as a trimeric protein and in the presence of an adjuvant.
  
  
  METHODS
  Based on in vitro neutralizing activity in serum, patients with bNAbs were selected for cloning of their HIV-1 Env. Seven stable soluble trimeric gp140 proteins were generated from sequences derived from four adults and two children infected with either clade A or B HIV-1. From one of the clade A Envs both the monomeric and trimeric Env were produced for comparison. Rabbits were immunized with soluble gp120 or trimeric gp140 proteins in combination with the adjuvant dimethyl dioctadecyl ammonium/trehalose dibehenate (CAF01). Env binding in rabbit immune serum was determined using ELISAs based on gp120-IIIB protein. Neutralizing activity of IgG purified from rabbit immune sera was measured with the pseudovirus-TZMbl assay and a PBMC-based neutralization assay for selected experiments.
  
  
  RESULTS
  It was initially established that gp140 trimers induce better antibody responses over gp120 monomers and that the adjuvant CAF01 was necessary for such strong responses. Gp140 trimers, based on HIV-1 variants from patients with bNAbs, were able to elicit both gp120IIIB specific IgG and NAbs to Tier 1 viruses of different subtypes. Potency of NAbs closely correlated with titers, and an gp120-binding IgG titer above a threshold of 100,000 was predictive of neutralization capability. Finally, peptide inhibition experiments showed that a large fraction of the neutralizing IgG was directed against the gp120 V3 region.
  
  
  CONCLUSIONS
  Our results indicate that the strategy of reverse immunology based on selected Env sequences is promising when immunogens are delivered as stabilized trimers in CAF01 adjuvant and that the rabbit is a valuable model for HIV vaccine studies.
authors.affiliation: Biomedical Department, Virology Unit, Institute of Tropical Medicine, Antwerp, Belgium.
authors.forename: Leo
authors.initials: L
authors.lastname: Heyndrickx
authors.forename: Guillaume
authors.initials: G
authors.lastname: Stewart-Jones
authors.forename: Marianne
authors.initials: M
authors.lastname: Jansson
authors.forename: Hanneke
authors.initials: H
authors.lastname: Schuitemaker
authors.forename: Emma
authors.initials: E
authors.lastname: Bowles
authors.forename: Luigi
authors.initials: L
authors.lastname: Buonaguro
authors.forename: Berit
authors.initials: B
authors.lastname: Grevstad
authors.forename: Lasse
authors.initials: L
authors.lastname: Vinner
authors.forename: Katleen
authors.initials: K
authors.lastname: Vereecken
authors.forename: Joe
authors.initials: J
authors.lastname: Parker
authors.forename: Meghna
authors.initials: M
authors.lastname: Ramaswamy
authors.forename: Priscilla
authors.initials: P
authors.lastname: Biswas
authors.forename: Guido
authors.initials: G
authors.lastname: Vanham
authors.forename: Gabriella
authors.initials: G
authors.lastname: Scarlatti
authors.forename: Anders
authors.initials: A
authors.lastname: Fomsgaard
mesh_terms: D000818:Animals; D057134:Antibodies, Neutralizing / Q000276:immunology; D002626:Chemistry, Pharmaceutical; D005260:Female; D015699:HIV Envelope Protein gp120 / Q000737:chemistry* / Q000276:immunology*; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D007700:Kinetics; D008297:Male; D023421:Models, Animal; D010446:Peptide Fragments / Q000276:immunology; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D011817:Rabbits; D014611:Vaccination; D054299:env Gene Products, Human Immunodeficiency Virus / Q000737:chemistry* / Q000276:immunology*
chemical_list: D057134:Antibodies, Neutralizing; D015699:HIV Envelope Protein gp120; D010446:Peptide Fragments; D054299:env Gene Products, Human Immunodeficiency Virus; C514793:gp120 protein, Human immunodeficiency virus 1; C097729:gp140 envelope protein, Human immunodeficiency virus 1
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