Oral Abstract Session 01 - Global HIV Vaccine Enterprise

Topic 12: Vaccine Concepts and Design
P12.09
Development of Chimeric HIV Env Immunogens for
Mucosal Delivery with Attenuated Canine Distemper
Virus (CDV) Vaccine Vectors
X. Zhang 1 , S. Richlak 1 , H.T. Nguyen 1 , O. Wallace 1 , G. Morrow 1 ,
M. Caulfield 1 , C. Parks 1
1 International AIDS Vaccine Initiative, Brooklyn, NY, USA
Background: Our aim is to develop replication-competent viral
vectors for mucosal delivery, which express HIV-Env immunogens
that closely mimic the trimeric glycoprotein spike found on HIV
particles. We have developed attenuated recombinant CDV
(rCDV) expressing SIVmac239-Env and shown that this vector can
be used safely to elicit Env-specific immune responses in ferrets
and non-human primates through intranasal administration.
Methods: To augment the cell surface expression of trimeric
HIV-Env and increase the replicative capacity of rCDV vectors
encoding the HIV glycoprotein, we have constructed chimeric
immunogens in which signal peptide (SP), transmembrane
domain (TM), or cytoplasmic tail (CT) domains in HIV-Env have
been replaced with analogous sequences from the vesicular
stomatitis virus (VSV)-G or CDV-F glycoproteins and compared
cell surface protein expression, antibody binding profiles and Env
function in transient expression assays.
Results: Chimeric glycoprotein based on subtype C Env
proteins were expressed on the surface of transfected cells
in conformations recognized by various broadly neutralizing
antibodies (bnAb) targeting distinct Env regions including VRC01,
b12, and b6 specific for the CD4 binding site, PG9 and PG16 (V1/
V2), 4e10 (gp41) but not by PGT-126 (V3) and 2G12 (glycans).
Moreover, treatment of transfected cells with soluble CD4
induced conformational changes needed to expose epitopes for
CD4 binding-dependent antibodies (17b, 48d and F425-A1g8).
Recombinant CDV vectors encoding two chimeric Envs have
been created. One is expressed most abundantly in transfected
cells and contained the VSV SP and CDV TM-CT. The second is
a highly fusogenic Env that contained the CDV SP and CDV CT.
Both vectors expressed Env and are being further characterized
in vitro and in vivo.
Conclusion: Collectively, we have shown CDV can be used
as a mucosal delivery vector for SIV-Env and that HIV-Env
modifications can be made that improve cell surface expression
of the trimeric glycoprotein containing structural determinants
recognized by bnAbs.
P12.10
AIDS Vaccine 2012
Posters
Stability and Neutralization Capacity of a Novel
Mosaic HIV-1 gp140 Trimer in a Guinea Pig Model
J.P. Nkolola 1 , J.M. Kovacs 2 , B. Korber 3 , B. Chen 2 , M. Seaman 4 ,
D. Barouch 1
1 BIDMC / Ragon Institute of MGH, MIT and Harvard, Boston,
MA, USA; 2 Children’s Hospital Boston, Boston, MA, USA; 3 Los
Alamos National Laboratory, Los Alamos, NM, USA; 4 Beth
Israel Deaconess Medical Center, Boston, MA, USA
Background: The generation of globally relevant HIV-1
immunogens mimicking native, trimeric Envelope (Env) structure,
remains a major challenge for HIV-1 vaccine development. We
identified a mosaic Env sequence, originally designed to optimize
cellular immunologic coverage of global HIV-1 sequence
diversity, which was capable of forming biochemically stable
trimers. We assessed this mosaic Env gp140 trimer in guinea pig
immunogenicity studies compared to our previously reported
biochemically stable C97ZA012 (clade C) trimer.
Methods: Stable Env gp140 trimer derived from a synthetic
mosaic sequence was stabilized with the T4-fibritin C-terminal
trimerization tag and produced in 293T cells via PEI transfection.
Characterization was performed by Western blotting, sizeexclusion
chromatography and surface plasmon resonance
(SPR). Guinea pigs were immunized three times with 100 µg
of mosaic or clade C gp140 protein trimer in CpG/Emulsigen
adjuvants. Antibody responses were determined by ELISA and
TZM.bl neutralizing antibody assays.
Results: Stabilized mosaic gp140 trimer exhibited a single
band by Western blotting, single peak by size-exclusion
chromatography both after production, a freeze-thaw cycle
and 7-day incubation at 4ºC. SPR analyses revealed mosaic
gp140 binding with bNAb VRC01. The trimeric mosaic gp140
immunogen elicited high-titer antibodies in guinea pigs by
ELISA and high-titer, cross-clade neutralization activity against
tier 1 viruses. When compared to clade C gp140 trimer, NAb
responses generated by mosaic gp140 trimer were 8.2- and
3.7-fold higher against clade B viruses (SF162.LS and Bal.26,
respectively) but were 10.3- and 46.7-fold lower against clade
A and C viruses (DJ263.8 and MW965.26, respectively).
Conclusion: A novel, foldon-stabilized mosaic gp140 trimer
elicits high-titer binding antibodies as well as high-titer, crossclade
neutralization of tier 1 viruses. The profile of the NAbs
elicited by the mosaic trimer differed from that elicited by
the clade C trimer. Further exploration and refinement of
this concept may contribute to the development of a globally
relevant Env immunogen.
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POSTERS