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Our research interests:
The main objectives of Molecular Immunology and Vaccine Research Laboratory
are to obtain fundamental insights into the immunology of leishmaniasis, as
well as developing novel approaches for vaccines to combat such infectious diseases.
Our research therefore covers investigations of the molecular basis and mechanisms
of pathogenesis, host immune responses, parasite and host genetics, and the
development of vaccines which demands a deep understanding of the molecular
biology of the parasite. Our work covers a wide spectrum from basic laboratory
research to field applications that involve numerous national and international
collaborations which can be further divided into following five main sections:
Section I: Searching for protective
antigens against Leishmaniasis as vaccine candidates
The importance of
Leishmania
cysteine proteinases (CPs) in host–parasite interaction and particularly in
immune evasion highlights their potential both as drug targets and vaccine candidates.
Our research team has shown that the L. major cysteine proteinases native
form is recognized by lymphocytes taken from humans and mice infected with
Leishmania. Immunization experiments have been carried out in the mouse
model using these enzymes. By different approaches, we also showed that recombinant
CPB, in combination with adjuvant, induces long lasting immunity against L. major infection in BALB/c mice, while DNA vaccination is more efficient when a cocktail of
plasmid DNAs encoding cpa
and cpb is applied, indicating the efficiency of using the combination
of these antigens.
The cysteine proteinases
type I and II (CPs) of L. infantum has been also used successfully as
a heterologous prime-boost regime for vaccination against experimental visceral
leishmaniasis in dogs. Furthermore, we showed that cysteine proteinase type
III (CPC) is also among the candidate antigens that could protect BALB/c mice
against L. infantum infection.
Recently, we have also performed that prime-boost vaccination
using C-terminal extension (CTE) of L. infantum cysteine proteinase type
I in BALB/c mice, exhibited both type
1 and 2 immune responses. Thus there is a great need to further investigate
and examine the protective potential of the mentioned cocktail vaccine including
CPB without CTE fragment.
It is crucial to emphasize that although DNA vaccination offers appropriate promises against
experimental leishmaniasis, free plasmid DNA
clinical utility is still faced with a number of significant hurdles. Thus
an appropriate vaccine formulation offers good opportunities
to increase vaccine efficacy. In this view, various colloidal carrier
systems have been extensively studied for the formulation of DNA vaccines. Amongst these, solid lipid nanoparticles
(SLN) are offered to be a promising alternative to the polymeric nanoparticles
and liposomes. In continuation of our vaccine study, we are attempting to prepare
SLN–pDNA
complexes as a vaccine formulation using cysteine proteinases type I, II and
III.
Signal Peptidase (SPase) is
the other antigen of our
interest. SPase is an
essential enzyme in both
prokaryotes and eukaryotes;
which removes signal
sequence from secretory
proteins. Recently, we have
isolated and characterized
SPase type I from L.
major (Lmjsp).
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The Lmjsp potential
protection was also
evaluated in three different
vaccination strategies
(DNA/DNA, Protein/Protein
and DNA/Protein), against
L. major infection. We
demonstrated that
vaccination with SPase
through all three mentioned
strategies induced a
parasite specific Th1
response and conferred
partial protection against
parasite challenge. In order
to further expand this area
and
to test if the gene is
essential for survival of
promastigote L. major,
two sequential rounds of
targeted gene disruption has
been done and different
parameters including both
in vitro and in vivo
evaluation of the ΔSPase
mutants are under study.
The other approach for vaccine development is designing
polytope vaccine.
It is shown that polytope
constructs either as DNA
vaccine or protein could
elicit effective multi-CTL
responses against every
epitope and even provide
good protection. Using
immunoinformatic knowledge,
different leishmanial
antigens have been selected
and are going to be
definitely processed and
presented in the context of
HLA class I to activate CD8+
T cells. Our vaccination
project with humanized
transgenic mice expressing
human HLA class I type as a
preclinical model for
vaccination against L.
major attempts to
confirm the ability of these
selected antigens to
re-stimulate memory CTLs of
the recovered patients
suffered from cutaneous
leishmaniasis.
Section
II:
Searching for virulence
factors in the
non-pathogenic parasite
L. tarentolae
There are more than 20 species that cause leishmaniasis
in humans. However, there
are also other species of
Leishmania genus
including L. tarentolae
that are solely parasites of
reptiles. Recently, in
collaboration with Prof.
Barbara Papadopoulou
(Infectious Diseases
Research Center, CHUL
Research Center, CHUQ, Laval
University, Quebec Canada),
we provide evidences that
the lizard non-pathogenic to
humans L. tarentolae
species expresses an
Amastin-like gene,
cysteine protease B (CPB),
lipophosphoglycan LPG3
and the leishmanolysin
GP63, which are all
well-known for their
potential role in the
parasite virulence. These
genes were expressed at
comparable altitude to those
in L. major and L.
infantum both at the
mRNA and protein level.
Interestingly, the A2
gene, which promotes
visceralization and
expressed specifically by
the L. donovani
complex, was absent in L.
tarentolae. Via A2 gene
transfection into L.
tarentolae, we showed
the ability of the
transfected parasites to
survive in visceral organs
of BALB/c mice as well as
intraperitoneal macrophages
in vitro. Our
immunization studies using
A2-transfected L.
tarentolae revealed a
potent Th1 response
establishment and BALB/c
mice protection against
L. infantum challenge.
Section III: Contribution of
human neutrophils in development
of protective immune responses
during in vitro L. major
infection
Leishmania
interacts with a number of
different cell types, and the
detailed interaction between
specific cells could help and
expand our understanding in
order to manage the disease and
develop new tools to control
leishmaniasis.
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