VECTORS IN VACCINE DELIVERY
• To transfer the desired
gene into a target cell,
a carrier is required.
Such vehicles of gene
delivery are known
as vectors.
• 2 main classes
– Viral vectors
– Non viral vectors
Cancer Vaccines
CD4 T Cell
Activated
Dendritic
Cell
TCR
Class II MHC
Cytokines = HELP
TCR
Tumor Antigen
Class I MHC
CD8 T Cell
Activated CD8 T Cells Traffic to
Tumor and Lysis Cells
Burch et al, 2000; Small et al 2000; Fong et al, 1997.
Viral Vaccines – Same Idea: But Starting At A Different Step
Co-Stimulatory
Molecules
PSA
ProstVac VF
LFA-3 ICAM-1 B7-1
Target Antigen
Vaccinia Virus
Fowlpox Virus
Plasmid DNA
Packaging Cell Line
rV-PSA-TRICOM
rF-PSA-TRICOM
PSA= prostate-specific antigen.
Madan et al, 2009; Sonpavde et al, 2011; Drake, 2010.
Vaccine
ProstVac VF
CD4 T Cell
TCR
Class II MHC
TCR
Class I MHC
Epithelial Cells
CD8 T Cell
ACTIVATED
CD8 T Cell
Madan et al, 2009; Sonpavde et al, 2011.
1. he
antigen prostatic
acid
phosphatase (PAP),
which is present in
95% of prostate
cancer cells, and
2. an immune
signaling
factor granulocytemacrophage
colony stimulating
factor (GM-CSF)
that helps the
APCs to mature.
The only cell-based therapy currently approved for the treatment of prostate
cancer.
APPLICATIONS
Basic research
Gene therapy
vaccines
MOST COMMON VIRAL VECTORS
Retroviruses
can create double-stranded DNA copies of their RNA genomes. Can
integrate into genome. HIV, MuLV, Rous sarcoma virus
Adenoviruses
dsDNA viruses that cause respiratory, intestinal, and eye infections
in humans. Virus for common cold
Adeno-associated viruses
ssDNA viruses that can insert their genetic material
at a specific site on chromosome 19
Herpes simplex viruses
dsDNA viruses that infect a neurons. Cold sores virus
Coxsackievirus and adenovirus receptor (CAR)
1.
their basic biology has been studied extensively
2.
they have previously been shown to be relatively safe for use in humans.
ADENOVIRUSES: vaccines
The first gene therapy licensed product, Gendicine,
is based upon an adenovector encoding tumor
suppressor p53 and was approved in 2003 in China for use
in the treatment of squamous cell head and neck cancer
adenovectors are being developed in efforts to make
vaccines for infectious diseases, including HIV malaria,38 SARS,39,40
and Ebola. Further, a nasal
application of an adenovirus expressing an influenza gene
has demonstrated safety and immunogenicity in humans
Adenovectors are also being evaluated as vaccines for animal diseases
such as rabies, and foot and mouth disease
•are used in not only single-modality vaccine regimens but
also mixed-modality prime-boost strategies, for instance,
following a prime with plasmid DNA vaccines.
ADENO-ASSOCIATED VIRUSES
1. the virus is dependent on the co-infection and
helper functions of other viruses such as adenovirus
and herpesvirus for efficient replication.
2. No human disease has been associated with AAV;
instead, it was shown to have beneficial effects for
the host as it inhibits the activity of oncogenic
viruses such as papilloma virus and adenovirus.
3. AAV exists in several serotypes; type 2 has been
most explored as a vector for delivering foreign
genetic material.
Viral Entry. The cell tropism of AAV varies between the different
serotypes, thus making a specific serotype more suited for a
particular application depending on the target tissue.
AAV-2 is able to infect a variety of cells, including liver, lung, muscle,
and central nervous system, and is believed to enter cells primarily
by binding to heparin sulfate proteoglycans, expressed throughout
the body. Upon binding to the target cell receptor, the AAV is
internalized by endocytosis, is released in the cytosol upon
acidification of the late endosome, and subsequently travels to the
nucleus
Poxviruses
Orthopox: smallpox virus(variola), v
acciniavirus, cowpox virus, monkeyp
ox virus
The poxviruses comprise a family of complex double-stranded DNA
viruses. They belong to the largest family of virus infectious for
humans.
Canarypox and fowlpox have been utilized, because they infect but
do not replicate in human cells. There is thus no concern about
preexisting immune responses to these vectors.
Variants of avipox members have been used in several preclinical
and clinical studies
HERPEX SIMPLEX VIRUS VECTOR
VIRAL VECTORS
1) RETROVIRUS VECTOR SYSTEM
•
The recombinant retroviruses have the ability to
integrate into the host genome in a stable fashion.
•
Can carry a DNA of
size – less than 3.4kb
•
Target cell - dividing
Retro virus:
IDEAL FEATURES OF A VECTOR:
☻High concentration of virus allowing many cells to be infected
or transduced
☻Convenience and reproducibility of production
☻Ability to transduce dividing and non-dividing cells
☻Ability to integrate into a site-specific location in the host
chromosome, or to be successfully maintained as stable
episomes.
☻A transcriptional unit that can respond to manipulation of its
regulatory elements
☻Ability to target the desired type of cell
☻No components that elicit an immune response
VACCINE TRIALS USING VIRAL VECTORS: AN EXAMPLE
Two groups of 9 animals each (3 controls and 6 vaccinees)
Group 1 (fowlpox group) =
genes)
Ad5-SIV comprised:
Gag/ Pol-
primed with an adenovirus-derived vector (expressing SIV
boost with a fowlpox virus-derived vector.
Group 2 (Adeno group) =
primed with fowlpox virus-derived vector
boost with adenovirus-derived vector
Control
“immunized” with empty vectors.
=
Experimental Plan/ Time line of blood withdrawal for quantification of specified genes
PI= preimmunization, FP= final priming, DOI= day of
infection/challenge
29
ex vivo evaluation of FAM26F expression upon SIV-infection
Exp-1 included 24 animals
Exp-2 included 18 animals
Challenged with repeatedly with low dose of SIVmac251
Experimental Plan/ Time line of blood (PBMCs) withdrawal for quantification of specified genes
Exp-1
Pre inf
1wpi
2wpi
12wpi
24wpi
12wpi
24wpi
48wpi
Exp-2
Pre inf
Wpi= weeks post infection Pre inf= pre infection
30
RNA copies/ml plasma
Controls
Vaccinees Grp 1
Vaccinees Grp 2
10 7
10 6
10 5
10 4
10 3
10 2
0
1
2
3 4 6 8 12 16 20 24 32 40
weeks post infection