Oral Abstract Session 01 - Global HIV Vaccine Enterprise

Topic 1: Adjuvants, Immunogens and Inserts
P01.21 LB
Immunogenicity of Native And CD4 Liganded
Monomeric And Trimeric Envelope Glycoproteins
Based on HIV-1 Subtype C Consensus Founder Virus
Sequences
M.A. Killick 1 , A. Capovilla 1 , M.A. Papathanasopoulos 1
1 HIV Pathogenesis Research Laboratory, Johannesburg,
South Africa
Background: The ability to induce a broadly neutralizing antibody
(bNAb) response following vaccination is regarded as a crucial
aspect in developing an effective HIV-1 vaccine. This study
describes the design and construction of a subtype C founder
virus consensus Env immunogen derived from newly transmitted/
founder virus sequences, and its immunogenicity testing in the
presence or absence of liganded CD4, in small animals.
Methods: Monomeric (gp120), dimeric (gp120GCN4) and
trimeric (gp140GCN4 +/-) founder virus conformations were
expressed in mammalian cell culture. Unliganded or 2dCD4S60C liganded Env glycoproteins were purified by lectin affinity
chromatography, followed by conformation and complex
purification using size exclusion chromatography. Immunogens/
immune complexes were evaluated by ELISA, SDS-PAGE, Native
PAGE and Surface Plasmon Resonance. Immunogenicity of each
conformation alone or complexed to 2dCD4S60C was evaluated
in rabbits. Breadth and potency of the rabbit sera was tested
against 12 pseudoviruses (Tiers 1-3), derived from HIV-1 subtype
B and C Env, using the PhenoSense Neutralizing antibody assay
(Monogram Bioscience Inc.).
Results: Minimal neutralizing breadth was obtained from
animals immunized exclusively with Env conformations.
However, animals that received the Env/2dCD4S60C complex
showed extensive neutralizing capacity against all 12 viruses
tested, including the tier 2 and 3 virus strains. End-point ELISA
titre results revealed that the rabbits that were immunized with
Env/2dCD4S60C produced both Env and 2dCD4 specific titres,
but those directed towards 2dCD4 were on average 10x lower
than the 2dCD4 control group. This implies a proportion of the
neutralizing antibody activity is directed towards conserved
epitopes exposed on the Env/2dCD4S60C immunogens.
Conclusion: The ability to induce bNAb activity in previous
immunization studies utilizing Env/CD4 complexes was attributed
to the induction of high anti-CD4 titres. By contrast, in our study
the relatively low anti-CD4 titres compared to anti-Env titres
and neutralization profiles suggest an alternative mechanism of
neutralization other than a response directed to CD4 alone.
P01.22 LB
AIDS Vaccine 2012
Posters
Multivalent Adenoviral Vectors which use an Antigen
Capsid-Incorporation Strategy for HIV Vaccination
L. Gu 1 , Z.C. Li 1 , V. Krendelchtchikova 1 , A. Krendelchtchikov 1 ,
Q.L. Matthews 1
1The Univeristy of Alabama at Birmingham, Birmingham, AL,
USA
Background: Adenoviral (Ad) vectors have been used for a
variety of vaccine applications. Traditionally, Ad-based vaccines
are designed to express antigens through transgene expression.
However, in some cases these conventional Ad-based vaccines
have had sub-optimal clinical results. These sub-optimal
results are attributed in part to pre-existing Ad serotype 5(Ad5)
immunity. To circumvent the need for transgene antigen
expression, the “antigen capsid-incorporation” strategy has
been developed and used for Ad-based vaccine development. In
addition, to increase the magnitude and/or breadth of antigenspecific
antibody response, this strategy can be utilized. The
major capsid protein hexon has been utilized for antigen display
due to hexon’s natural role in the generation of anti-Ad immune
response and its numerical representation within the Ad virion.
Methods: Based on our abilities to manipulate Ad5 HVR2 and
HVR5, we sought to manipulate Ad5 HVR1 in the context of HIV
antigen display. More importantly, peptide incorporation within
HVR1 was utilized in combination with other HVRs. In order to
create a multivalent vaccine vector, we created vectors that
display antigens within HVR1 and HVR2 or HVR1 and HVR5. To
date this is the first report where dual antigens are displayed
within one Ad hexon particle. These vectors utilize HVR1 as
an incorporation site for a seven amino acid region of the HIV
glycoprotein 41; in combination with a six Histidine (His6)
incorporation within HVR2 or HVR5.
Results: Our study, illustrates that these multivalent antigen
vectors are viable, present HIV antigen as well as His6 within one
Ad virion particle. Furthermore, mouse immunization with these
vectors; demonstrate that these vectors can elicit a HIV and His6
epitope-specific humoral immune response.
Conclusion: Our study focuses on generation of proof of
concept vectors that can ultimately result in the development of
multivalent vaccine vectors displaying dual antigens within the
hexon of one Ad virion particle.
105
POSTERS