Transcript Demonstration of Cross-Protective Vaccine Immunity against an

Demonstration of Cross-Protective Vaccine
Immunity against an Emerging Pathogenic
Ebolavirus Species
May 20, 2010
PLoS Pathogens Volume 6 Issue 5
Abstract
A major challenge in developing vaccines for emerging pathogens is their continued
evolution and ability to escape human immunity. Therefore, an important goal of vaccine
research is to advance vaccine candidates with sufficient breadth to respond to new
outbreaks of previously undetected viruses. Ebolavirus (EBOV) vaccines have
demonstrated protection against EBOV infection in nonhuman primates (NHP) and show
promise in human clinical trials but immune protection occurs only with vaccines whose
antigens are matched to the infectious challenge species. A 2007 hemorrhagic fever
outbreak in Uganda demonstrated the existence of a new EBOV species, Bundibugyo
(BEBOV), that differed from viruses covered by current vaccine candidates by up to 43%
in genome sequence. To address the question of whether crossprotective immunity can
be generated against this novel species, cynomolgus macaques were immunized with
DNA/rAd5 vaccines expressing ZEBOV and SEBOV glycoprotein (GP) prior to lethal
challenge with BEBOV. Vaccinated subjects developed robust, antigen-specific humoral
and cellular immune responses against the GP from ZEBOV as well as cellular immunity
against BEBOV GP, and immunized macaques were uniformly protected against lethal
challenge with BEBOV. This report provides the first demonstration of vaccine-induced
protective immunity against challenge with a heterologous EBOV species, and shows
that Ebola vaccines capable of eliciting potent cellular immunity may provide the best
strategy for eliciting cross-protection against newly emerging heterologous EBOV
species.
Methodology
Immunization of
cynomolgus
macaques with two
plasmid vectors
encoding for GP(Z)
and GP(S/G)
Infection with
BEBOV
Determination of liver
enzyme levels for serum
alanine aminotransferase
and aspartate
aminotransferase (Blood
chemistry)
RNA isolation and
quantitative realtime RT-PCR
(qRT-PCR)
T cell intracellular
cytokine secretion
analysis
Anti-Ebola GP IgG
ELISA
Computational
analysis of GP
sequences
Statistical analysis
Immunization and Infection
Biojector IM injection,
bilateral deltoid, of
cynomolgus macaques
(Macaca fascicularis)
and infection with 1,000
TCID50 BEBOV
Blood Chemistry
Determination of liver enzyme
levels for serum alanine
aminotransferase (ALT) and
aspartate aminotransferase
(AST)
Anti-Ebola GP IgG ELISA
Polyvinyl chloride ELISA
plates coated with EBOLA
GP
Incubated with subject sera
or plasma
Bound IgG detected using
goat anti-human IgG
conjugated to horseradish
peroxidase and Sigma Fast
o-phenylenediamine
dihydrochloride
T cell Intracellular Cytokine
Secretion Analysis
PBMC separated from whole
blood samples over Ficoll
Stained with antibodies against
lineage markers and intracellularly
with antibodies against cytokines
Analyzed by flow cytometry
RNA isolation and qRT-PCR
RNA extracted with
RNAqueous kit
Iscript One-step qRTPCR kit
Significance of the Study
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Vaccine development against Ebola viruses =
high priority
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Aggressive nature of Ebola virus hemorrhagic
fever (EHF) symptoms
Rapid spread of infection
High mortality rate
Threat of bioterrorism
Frequency of EBOV outbreaks in Africa has
increased
Significance of the Study
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Four known species:
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Zaire (ZEBOV)
Sudan (SEBOV)
Reston (REBOV)
Cote d’Ivoire (CIEBOV)
Bundibugyo (BEBOV) = fifth
species discovered in late
2007 in Western Uganda
rAd5 vaccines = encode GP
from SEBOV and ZEBOV
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sequences differ from BEBOV
by 38–47% at the amino acid
level
Innovation
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Needle-free injection system (Biojector)
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special technique of forcing liquid medication at high speed through a
tiny orifice that is held against the skin
Innovation
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DNA/rAd prime-boost vaccination
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Targets structural proteins from ZEBOV and
SEBOV
Cross-protective immunity against BEBOV
rAd vectors = boosted antigen-specific immune
response even a year after the final DNA prime
CD4+ and CD8+ T-cell effector immunity
Contribution to the Field of
Virology
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BEBOV
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Conservation of immunogenic regions exists between
different species of Ebola virus
New design for next-generation vaccines
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less pathogenic
more sensitive to host immunity
a mechanistic basis for vaccine-induced immune protection against Ebola virus
infection
Possible protection against Ebola virus species whose
antigens are not present in the vaccine formulation
Eliciting robust T-cell immunity
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greatest potential to protect against other newly emerging pathogenic Ebola virus
species