Oral Abstract Session 01 - Global HIV Vaccine Enterprise

Topic 1: Adjuvants, Immunogens and Inserts
P01.17 LB
Neutralizing Antibodies Elicited In Rabbits By Patient-
Derived Env Trimer Immunization
L. Heyndrickx 1 , G. Stewart-Jones 2 , H. Schuitemaker 3 ,
E. Bowles 2 , L. Buonaguro 4 , M. Jansson 5 , B. Grevstad 6 ,
L. Vinner 6 , M. Ramaswamy 7 , P. Biswas 8 , G. Scarlatti 8 ,
G. Vanham 1 , A. Fomsgaard 6
1 Institute of Tropical Medicine, Antwerp, Belgium; 2 Human
Immunology Unit, Weatherall Institute of Molecular Medicine,
Oxford, United Kingdom (Great Britain); 3 Academic Medical
Center, University of Amsterdam, Amsterdam, Netherlands;
4 Istituto Nazionale Tumori “Fond. G. Pascale”, Naples,
Italy; 5 Department of Laboratory Medicine, University of
Lund, Lund, Sweden; 6 Statens Serum Institut, Copenhagen,
Denmark; 7 National Institute for Biological Standards and
Control, Hertfordshire, United Kingdom (Great Britain); 8 DIBIT
- San Raffaele Scientific Institute, Milan, Italy
Background: Eliciting broad cross neutralizing antibodies
(bNAb) remains the primary and most challenging goal in HIV-1
vaccine development. So far no vaccine candidate has induced
such bNAb. Selecting Env vaccine candidates will require both
antigenic and immunogenic optimization and testing in relevant
animal models.
Methods: Based on in-vitro neutralizing activity in serum,
patients (n=6, subtype A and B infected) were selected
and Env sequences of early HIV-1 variants, still sensitive to
autologous neutralization, were used to generate soluble Env
as immunogens. Gp140 trimeric proteins were expressed (293T
cells) and purified. Rabbits (4/group) were immunized s.c. at
weeks 0, 2, 4, 8 with 100µg trimer adjuvanted with cationic
CAF01. Control groups received 20µg and 100µg trimer plus/
minus CAF01 respectively. Sera collected at weeks 0, 2, 4, 8, 12
and 14 were screened in gp120-IIIB ELISA and IgG was analyzed
in the TZMbl neutralization assay.
Results: All rabbits generated a gp120-IIIB specific IgG response 2
weeks after the first immunization and titers were boosted after
each subsequent immunization. IgG titers measured 4 weeks
after the last immunization clearly differed between groups (n=5)
receiving 100µg/immunization (Geometric mean titer (GMT)
: 152.601) and the group receiving 20µg/immunization (GMT :
13.262) or the group omitting CAF01 (GMT : 27.262). Only IgG
from rabbits receiving the highest dose and in the presence of
CAF01 were able to neutralize Tier 1 pseudoviruses of different
subtypes.
Neutralizing activity was detected after the 2nd immunization
and was boosted after each immunization. No significant
differences were observed between the different trimers.
Conclusion: Gp140 trimers based on HIV-1 variants of patients
with bNAb in serum elicited gp120-IIIB specific IgG and NAb given
that enough immunogen was administrated in the presence of
CAF01. These results indicate that the development of HIV-1 Env
specific NAb is dose dependent and strengthen the rabbit model
for HIV vaccine studies.
P01.18 LB
AIDS Vaccine 2012
Posters
Rationally Designed HIV Envelope Glycoproteins
Delivered in a Novel Adjuvant Elicited More Broadly
Reactive Antigen-Specific Antibody Responses
A.K. Dey 1 , A. Kassa 1 , A. Nandi 1 , Y. Sun 1 , C. Labranche 2 , K. Hartog 1 ,
D. Montefiori 2 , A. Carfi 1 , I. Srivastava 1 , S.W. Barnett 1
1 Novarits Vaccines & Diagnostics, Cambridge, MA, USA;
2 Department of Surgery, Duke University Medical Center,
Durham, NC, USA
Background: The identification of optimal antigen(s) and
adjuvant combination(s) to elicit potent, protective, and longlasting
immunity has been a major challenge for the development
of effective vaccines against HIV-1.
Methods: Here, we designed disulfide-stabilized recombinant
HIV-1 subtype B (SF162) envelope glycoproteins (Env), gp120
and gp140, by insertion of site-specific cysteine pairs between
two layers (layer 1 and 2) in inner domain of gp120. In addition,
we identified a novel adjuvant approach using Carbopol 971P,
a cross-linked polyanionic carbomer, in combination with the
Novartis proprietary oil-in water adjuvant, MF59, to augment
humoral immune responses to the Env glycoprotein. We
performed thorough in vitro analysis of the disulfide-stabilized
Env glycoprotein followed by in vivo evaluations of the
adjuvanted-Env glycoprotein boost in rabbits.
Results: Intramuscular immunization of rabbits with disulfidestabilized
Env glycoproteins formulated in Carbopol 971P
plus MF59 gave significantly higher titers of binding and virus
neutralizing antibodies as compared to immunization using
Env glycoprotein with either MF59 or Carbopol 971P alone.
In addition, the antibodies generated were of higher avidity.
Mapping of serum antibodies to determine epitope specificities
showed that the disulfide-stabilized gp140 proteins elicited
broader Env glycoprotein-specific antibody responses directed
against epitopes that included the CD4-binding site, CD4-induced
site and V1V2-loop. Importantly, the use of the novel adjuvant,
Carbopol plus MF59, did not appear to present any obvious
tolerability issues in animals upon intramuscular administration.
Conclusion: Hence, the use of rationally stabilized Env-antigens
in potent Carbopol 971P plus MF59 adjuvant may provide a
benefit for evaluations of future vaccine against HIV-1.
103
POSTERS