Transcript - ISpatula

DEFINITION
 Ebola
virus is a pathogenic virus that has
an epidemic outbreak throughout Africa
and worldwide in 2014- 2016 with high
mortality rate reaches 40-90% near the
outbreak onset.
SIGN & SYMPTOM
There is no specific sign and symptoms for
EVD , mainly characterized by :
Fatigue , myalgia , arthralgia, headache
then after days patients show
hemorrhagic fever
Anorexia , nausea , vomiting , diarrhea
Multiorgan dysfunction .
Uncontrolled bleeding and persistent
elevated temperature are the main cause
of death.
TRANSMISSION
 The
incubation time is 2-21 days , during
this period Ebola is not contagious and
pateint are asymptomatic.
 This viruse is transmitted via contact
with body fluids such as blood , breast
milk, saliva , feces and tears .
 Direct contact is not sufficient for
transmission .
INTERVENTION
 By
isolation of infected patients and offer
supportive care to reduce symptoms
associated with this disease involves
rehydration and pain management.
 Using
PPE to prevent transmission.
Although some patient may undergo
spontaneous remission with no
explanation.
And some of them who survive may
exhibit Post-Ebola syndrome
characterized by :
1-Mental health and cognitive
sequelae
2-Chronic headache
3-Auditory disturbances and ocular
effect
Scientists have poor prognosis for
ebola virus disease because we
lack the proper understanding of
the basic biology for this virus and
all drugs and vaccines that may
treat or prevent this virus are still
under development.
Clinical manifestation
&Treatment
Treatment
• No Standard treatment available,
however, several experimental strategies
have shown promise in treating Ebola
disease.
• Patients receive supportive therapy:
• treating of secondary bacterial
infections and pre-existing
comorbidities.
• balancing electrolytes (body salts)and
maintaining oxygen level and blood
pressure status.
• balancing patient’s fluids
EXPERIMENTAL
Nucleic-acid
based inhibitors
DRUG THERAPY
Immunotherapeu
tic
Nucleoside/nucleotide viral polymerase inhibitors
Immunotherapeutic:
ZMapp is a cocktail of monoclonal antibodies
and is being able to revert advanced Ebola
disease when administered up to five days
post
The structure of antibodies bound to the
Ebola virus glycoprotein and inhibit entry of
the virus
into cells .
 Mortality
in the ZMapp treated
participants was 40 percent lower than
the mortality in participants receiving
standard of care alone ZMapp treated
participants also had a more rapid
elimination of virus from the bloodstream.
Nucleoside/nucleotide viral
polymerase inhibitors
Only the nucleoside analogue favipiravir has
been tested extensively in humans.. Besides
activity against influenza virus infection,
this drug also has documented activity
against a wide variety of RNA viruses
including Ebolaviruses.
Favipiravir prevented death in mice infected
with EBOV when treatment was started six
days post infection.
Nucleic-acid based inhibitors
Such as small-interfering RNAs (siRNAs ) .
 Four
siRNAs targeting the polymerase (L)
gene of the Zaire species of EBOV
(ZEBOV) were either complexed with
polyethylenimine (PEI) or formulated in
stable nucleic acid–lipid particles (SNALPs).
Guinea pigs were treated with these siRNAs
either before or after lethal ZEBOV
challenge.
REPLICATING EBOLA VIRUS
VACCINES
1. RECOMBINANT VESICULAR STOMATITIS
VIRUS-BASED VACCINES
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The first replicating Ebola virus vaccine
shown to be protective in NHPs .
It was identified by the WHO expert panel
as one of the most advanced candidates for
use in the West Africa outbreak.
In this vaccine, the VSV GP was replaced
with ZEBOV (Zaire Ebola virus) GP.
A transient rVSV viremia may occur in
vaccinated animals and humans .
 The
recombinant virus was tested in NHPs
infected with SHIV and it did not cause any
clinical illness and the vaccine was able to
protect 4 out of 6 NHPs.
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This study is of particular importance
because of the high prevalence of HIV in
areas with ebolavirus outbreaks
A blended formulation of three rVSV
encoding GP from ZEBOV , SEBOV ( Sudan
Ebola virus) , and Marburg virus was able to
protect against challenge with all of those
viruses and also against challenge with
CIEBOV (Cote d'Ivoire Ebola virus).
2. RECOMBINANT PARAMYXOVIRUSBASED VACCINES
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HPIV3 is a negative-sense RNA virus.
A transcription unit encoding the ZEBOV
GP and/or ZEBOV-NP gene was introduced
between the P and M genes of HPIV3.
this vaccine was given intranasally to
Guinea pigs and it was 100%protective after
a single vaccination . In rhesus macaques ,
two vaccine doses were required to achieve
100%protection.
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One of the problems that may affect the efficacy
of this vaccine is the pre-existing immunity .
So this vaccine was improved by deleting the
HPIV3 F and HN genes, which are the main
targets for the HPIV3-specific humoral immune
response.
Bukreyev and colleague developed a new vector
based on Newcastle disease virus (NDV) which is
an avian paramyxovirus with no detectable preexisting immunity in humans and a new
recombinant vector expressing ZEBOV-GP was
generated (rNDV/ZEBOV-GP).
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2.
3.
First data suggest that the rNDV/ZEBOV-GP
vector might be less immunogenic than the
HPIV3-based vaccine.
The main advantages of the HPIV3-based vector
are :
The potential for needle-free administration.
It is easy to be produced in large quantities
It induces a systemic and local immunity in the
lungs which is beneficial against aerosol
infection.
3. RECOMBINANT RABIES-VIRUS BASED
VACCINE
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Rabies virus is a negative-sense RNA virus
of the Rhabdoviridae family.
It causes more than 24,000 deaths per year
in Africa so an effective bivalent
RABV/ebolavirus vaccine would be a
valuable vaccine in that region .
o
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1.
2.
SAD B19 rabies virus is the vaccine that is
already used for rabies wildlife vaccination in
Europe .
This strain was further attenuated by
introducing a point mutation in the rabies
glycoprotein G gene(particularly at amino acid
333) to reduce neurovirulence.
ZEBOV GP was introduced as an additional
transcriptional unit between the N and P genes ,
and two varients were generated:
BNSP333-GP which retains rabies G .
A replication-deficient derivative , the
BNSPΔG-GP, in which rabies G gene was
deleted .
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The BNSPΔG-GP did not cause any clinical signs
or lethality after intramuscular, intranasal or
intraperitoneal infection of mice, even after
intracerebral inoculation of sucking mice.
Recently this vaccine have been evaluated in the
rhesus macaque model in which one dose of the
vaccine was 100%protective .
The BNSP333-GP remained neurovirulent in the
sucking mice model which is considered a very
stringent model.
4.RECOMBINANT CYTOMEGALOVIRUS-BASED
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It is a DNA virus. It was genetically
engineered to express a CTL epitope located
on ZEBOV-NP.
This vaccine can be used as a disseminating
vaccine to target wildlife involved in the
initial transmission of Ebola virus to humans
because of its unique potential to re-infect
and disseminate through target populations
regardless of prior CMV immunity.
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Mice were vaccinated with two doses of
recombinant murine CMV/ZEBOV-NP and
challenged with a lethal dose of MA-ZEBOV.
the vaccinated mice survived the challenge
but were not protected from MA-ZEBOV
replication.
but clearly the protective efficacy of CMVbased vaccines should be evaluated in
larger animal models such as NHPs.
NON-REPLICATING EBOLA VIRUS
VACCINE
1.Inactivated vaccine:
Ebola virus inactivated by heat , formalin or gamma
irradiation
 Not effective due to:
[1] the potential risk of reversion to virulence of conventional
inactivated vaccine
[2] ineffectiveness ot this vaccine in protecting NHPs
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2.VLPs:
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subunits based vaccine produced from mammalian cell
transfected with plasmid encoding matrix protein of
filoviruse , VP40 , GP and NP.
Efficacy studies represent VLPs as a promising filoviruse
vaccine for the use in human ,100% protection Against
ZEBOV with VLPs consisting of VP40 and GP.
researchers switch (293T) mammalian cell to bacloviruse
based expression system using insect cell , in order to
increase VLPs production.
3.Recombinant adeno-virus:
Highly promising and the most studied approach
 developed by GP or NP antigen of EBOV or ZEBOV introduction
into the rAd5 plasmid which has the ability to generate robust T
and B cell responses to viral antigenes
 safe and immunogenic in phase  clinical trail using 1010 IFU rAd5
based vector expressing ZEBOV-GP as an antigen against ZEBOV.
 Problems:
[1] High vaccination dose required
[2] preexisting Immunity to Ad5 which may represent (60-90)% of a
population.
 In order to overcome these problems researchs find that
delivering of the vaccine via the oral , nasal or intratracheal rout
circumvent pre-existing immunity without affecting efficacy
against lethal challenge and improve T cell response , and
changing the rAd5 vector to a different serotype
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4.DNA VACCINS
DNA vaccination was discover in last years to
treat many viruses including Ebola virus,
Particularly in regard to emerging and reemerging pathogens.
ADVANTAGES OF USING DNA VACCINE
 RAPIDLY ADAPTED AS PATHOGENS.
 The plasmids are
Noninfectious.
 Easy to produce in large
quantities.
DNA vaccine induce cellular and humeral
immune responses, but this require
administration of several doses to
achieve the desired immunity.
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For ZEBOV, the first successful immunization
strategy using DNA was described in 1998 .
RESULTS :
 100% of the vaccinated mice can be protected
from lethal disease when given four doses of
plasmid DNA encoding either ZEBOV-GP or
ZEBOV-NP .
 Partial protective efficacy with three doses of
plasmid DNA
 But 50% of the surviving animals developed
viremia.
 Clinical trial phase 1 showing that three doses of
a DNA vaccine-encoding ZEBOV-GP, -NP and
SEBOV-GP are immunogenic in humans.
5.ALPHAVIRUS REPLICONS
Venezuelan equine encephalitis virus (VEEV) is an
alphavirus and was used early on in the EBOV
vaccine development as a potential platform .
5.Alphaviruses
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VEE replicon was achieved by replacing the
structural genes of an attenuated VEEV strain
with ZEBOV-GP, -NP, -VP24, -VP30, -VP35 or VP40 and expressed from an RNA expression
vector; then coverting to particle by providing
the structural VEEV genes in trans.
All the vectors were immunogenic in mice, only
the one expressing ZEBOV-NP conferred 100%
protection in the mouse model.
Combination of the vectors expressing ZEBOVGP and ZEBOV-NP resulted in 100% survival in
mice.
Protective efficacy of these two promising
VEEV/ZEBOV vaccine vectors was further
investigated using strain 13 guinea pigs.
The result (differed from the data obtained in mice )
The VEEV/ZEBOV-GP vector alone or in combination with
the vector-expressing ZEBOV-NP showed 100% protection.
Passive transfer of serum from vaccinated animals
into naïve strain 13 guinea pigs resulted in no
protection from lethal infection.