Transcript Model Comparison Minutes

Models Comparison: Mouse,
Rat, NHP, Human-Protection,
Immunology and Pathology
Bob Sherwood, Terry Wu, Julie
Wilder, Julie Hutt, Michelle
Valderas, Rick Lyons
1
Task for TVDC
Develop a small animal model and a
primate model that will provide the
necessary infrastructure to test
tularemia vaccine candidates
~ 60% of the projected contract activity
Where do we stand???
2
What are the metrics for a
good animal model
• Infection parameters should be
consistent with human disease i.e.
route, sensitivity, immune responses
• Pathological consequences of infection
should be similar
• Vaccine gold standards ( when they
exist) should provide protection
3
Historical Summary of Vaccine Studies
as of the Beginning of Contract
Species
Immunology
tools
Sensitivity to LVS vaccination
LVS vaccination against aerosol or
i.n. challenge
Scarification
(s.c. / i.d.)
Pulmonary
(Aerosol / i.n.)
Scarification
vaccination
Pulmonary
vaccination
Human
Low
Low
>50%
protectionagainst
2.5 x 104 SCHU S4
Protection against
2.5 x 104 SCHU S4
@ 4 or 6 mo
NHP
(Rhesus)
Low
Low
13 of 16 (81%)
against 104
15 or 16 (94%)
against 104
Mice
Rats
Guinea Pigs
Inbred
Excellent
Low
High
Increased time to
death to small
challenge dose
Protected against
small challenge
dose
Outbred
Excellent
Low
???
Increased time to
death to small
challenge dose
???
Inbred
Good
Low
Low
Protected against
105.3 SCHU S4
Protected against
105.3 SCHU S4
Outbred
Good
???
???
Acetone extract of
strain 38 protected
against SCHU
Unvaccinated rats
resistant to 105
SCHU
Some
Low
Low /
moderate
No effect / minimal
increase in time to
death
increase in time to
death
Data limited to 15 d
4
p.i.
Historical Human Studies
• Vaccination by scarification equivalent
– Well tolerated;
– Local lesion within 24 hr of vaccination and papule
within 48-72 hr
– All vaccinees developed antibodies by bacterial
and hemagglutination tests
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Historical Human Vaccinee Studies
(cont)
• Respiratory Challenge
– 3 of 18 vaccinated individuals challenged with 10-52 SCHU
S4 aerosol developed systemic disease Saslaw et al. (1961)
Arch Int Med
– Breakthrough dose > 20,000 SCHU S4 (2 with modified
disease and 1 required treatment) McCrumb (1961) Bacteriol
Rev
– Abrupt symptoms 5-7 days after challenge
– Increased RBC sedimentation rate, CRP positive, culture
negative, increased bacterial and hemagglutinations in 2 of
the more severe patients
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Human Pathology Based on
Postmortem studies
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Historical Human Studies
• Increased RBC sedimentation rate, Creactive protein, agglutination; culture
negative
• C-reactive protein useful indicator of
microbrial activity since it disappeared as the
illness remitted and reappeared promptly with
febrile relapse
8
Historical Human Studies
• Human immune sera demonstrates reactivity
to LVS by ELISA and Western blot
• Reactivity directed against LVS LPS and is
“completely” cross-reactive with SCHU S4
LPS
• Pooled immune sera passively protected
mice against 10,000 LD50 dose of LVS
Drabick et al., Am. J. Med. Sci. 308:83-7, 1994.
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LVS Viability in Humans – (2006)
• Sampled blood and vaccination site of
LVS vaccinated volunteers
• No culture or PCR positive blood
samples on Days 1, 2, 7 or 8, 14 or 15,
or 35
• PCR positive at vaccination site on Days
1 (100%), 2 (98%), 7 or 8 (58%), or
14 or 15 (17%) and 35 (0%)
Hepburn et al., Clin. Infect Dis. 43:711-6, 2006.10
LVS sensitivity
Route
Mouse
Fisher Rat Cyno
Human
Pulmonary
sensitive
resist
resist
resist
Subcutaneous
resist
resist
resist
resist
Intradermal
resist
resist
resist
resist
Novicida sensitivity
Route
Mouse
Fisher Rat Cyno
Human
Pulmonary
Sensitive
Attenuated
Attenuated
Unknown
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Schu 4 sensitivity
Route
Mouse
Fisher Rat Cyno
Human
Pulmonary
<2 org
<200
<10
<2
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LVS induced protection
among species
Endpoint
Mice
Rats
Cynos
Humans
Challenge
threshold
<200
<1 X10 e5
?
<2 X10e4
Organ
Burden
Decreased Decreased Decreased ?
Pathology
Decreased Decreased Decreased ?
Morbidity
Decreased Decreased No change Decreased
Mortality
Decreased Decreased No change Decreased
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Immunology comparisons
post LVS vaccination
Assay
Mice
Rats
Cynos
Humans
ELISA
Positive
Positive
Positive
Positive
Micro agglutination
TBD
TBD
TBD
ELIspot
PositiveIFN
PositiveIFN
PositiveIFN
TBD
PositiveIFN/TNF
TBD
TBD
TBD
PositiveIFN
dependent
Multi functional T cell
FT Growth inhibition
Positive
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Pathology comparisons of
primary infection with Schu S4
Endpoint
Mice
Rats
Cynos
Humans
Lung
Vasculitis
Alveolar/Va
sc
Alveolar/Va Alveolar/Vas
sc
c
Primary lesion
Pyogran
Pyogran
Pyogran
Pyogran
Dissemination
Hemo
Hemo
Hemo
Hemo
Necrosis
Significant
Significant
Significant
Significant
Coagulopathy
NT
NT
Postive
?
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Pathology comparisons of
infection with Schu S4 post
LVS vaccination
Endpoint
Mice
Rats
Cynos
Humans
Lung
Vasculitis
Alveolardecreased
Alveolarminimal
impact
?
Primary lesion
Pyograndecreasd
numbers
Pyogran
Pyogran
Decreased Decreased
numbers
numbers
?
Dissemination
Hemo
Hemo
None
Necrosis
Decreased Decreased Slightly
decreased
?
Coagulopathy
NT
?
NT
Hemo
Postive
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Species Comparison of Responses to
Tularemia
Rats are more similar to Cynos and Humans based
on:
LVS immunization protects via a variety of
vaccination routes
Early lung pathology in naïve rats are c/w
broncho- pneumonia
LVS vaccination protects against broad range
of Schu challenges
Not enough information to comment on
immunology
17
Further questions and
research emphasis for
remaining period
• Role of antibodies in vaccinated animals
• NHP – Need to determine survival benefit
by LVS in cynos
• Functional correlate of protection assay among
species
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