Download David Liu`s Stittelaar slides

Antiviral Treatment Is More
Effective Than Smallpox
Vaccination Upon Lethal
Monkeypox Virus Infection
David Liu
Smallpox: Gone
but not
forgotten
Stittelaar, et al.
Nature. 2006 Feb 9;439(7077):745-8
0
History: Vaccination and Eradication
 Variola Major
 The fir st vaccine in histor y was
developed for smallpox by Edward
Jenner in 1796.
 By the 1960s, smallpox was
limited to developing countries —
completely eradicated from the
West. Vaccinia vaccine.
 1967 WHO global vaccination
campaign
 Last natural case in 1977
 In 1978, all known stocks were
transferred to either the CDC in
Atlanta or the VECTOR Institute in
the USSR.
1
Possible: bioterrorism
 Smallpox is:




Easily transmissible
High mortality rate
Disfiguring
Vaccination has stopped
virgin population
 Pox Americana
 Hypothetical illicit sources .
 Known weaponization of
smallpox in the former
Soviet Union
 Flat-type smallpox:
Mortality rate > 96%
 Hemorrhagic-type smallpox:
Mortality rate > 98%
2
CDC response plan
 Overall plan:
 1) Identify and isolate smallpox cases to prevent further
disease spread,
 2) Identify, vaccinate, and monitor contacts of cases and
household contacts of contacts, to prevent secondary cases.
 Stance on post-exposure: “if [the vaccine is] administered
within 3 days after exposure to smallpox virus , it may prevent
disease, or decrease the severity of disease and risk of
death.”
 Newest version 3.0: The CDC Smallpox Response Plan and
Guidelines were last updated on September 23, 2002.
3
Antiviral treatment: nucleotide
analogues (De Clerq, 2004)
Acyclic nucleotide phosphonates
4
Research Question
What would be the efficacy of post-exposure
vaccination versus antiviral treatment in the
event of poxvirus re-emergence, e.g. a
bioterrorist attack?
Proof of concept study
5
Overview of methods
 Infect monkeys with a lethal respiratory dose of
monkeypox virus
 Why not smallpox?
 Determine treatment efficacy in drug -treated, vaccinated,
and control groups
 Five parameters (independent variables): survival, O 2
profile, lesions, viral load, immune response
(antibodies/T-cells)
 Measurements made on days 1, 3, 5, 7, 10, 13, 18, 21,
26
 Throat swabs, plasma samples, O 2 readings, observation
6
Setting up.
 Infection of monkeys with 10 7 pfu of MPXV
 Segregation into experimental groups:






I : Control (n=17) (n=6)
II: Elstree-RIVM (vaccinia-virus vaccine) (n=6)
III: Cidofovir (5 doses): Days 1, 3, 7, 10, 13 (n=6)
IV: Cidofovir (6 doses): Days 1, 3, 5, 7, 10, 13 (n=6)
V: HPMPO-DAPy (5 doses) (n=4)
VI: HPMPO-DAPy (6 doses) (n=6)
 Already proven that pre -exposure vaccination is ef fective
against smallpox infection ( Stittelaar 2005)
 Drugs given in dosages of 5 mg kg -1
 Monkeys in group III — VI were also given probenecid
7
Methods for Parameter 1: Survival
 Kaplan-Meier Plot
 Commonly used in epidemiological studies
 Accounts for “lost” subjects
 Depicts the probability of survival at time t

 Approximate true survival curve
 Plasma creatinine levels
8
Results for Parameter 1: Survival
Figure 1.
9
Methods for Parameter 2/3: Blood O 2
levels and lesions
 Complications of smallpox most commonly arise in
the respiratory system, usually around day 8
 Dyspnea/anorexia
 Blood O 2 levels measured using pulse oximeter
 Lesions are an obvious sign of the severity of the
virus
10
Results for Parameter 2/3: Blood O 2
levels and lesions
Figure 2.
11
Methods for Parameter 4: Viral Load
 Real-time PCR with monkey plasma/throat swabs for
MXPV DNA (dsDNA virus)
 Simultaneous amplification and quantification
 Fluorescent nucleotides
 HA gene primer
 The golden standard of viral studies
12
Results for Parameter 4: Viral Load
Figure 3.
13
Methods for Parameter 5: Immune
Response
ELISA with RK13
cells as a reference
 MPXV- specific IgG
Antibodies
Interferon-γ ELISPOT
assay
 MPXV-specific T-Cells
 80% of peripheral
blood is T-cells
14
Results for Parameter 5: Immune
Response
Supplementary
Figure 1.
15
Summary of Results
1. Post-exposure vaccination not effective
2. Cidofovir and HPMPO-DAPy can protect
macaques against MXPV when administered
early
• 6 doses better than 5
• HPMPO-DAPy performed better than Cidofovir
3. Drug treatment allows for development of
antibody resistance
16
Possible Limitations
 Better smallpox vaccines
 Possible toxicity (monkey 23)
 Small sample sizes
 Proof of concept
 Monkey model
17
Implications
1. Need to rethink efficacy of post-exposure
vaccination strategies
2. Integration of antiviral drugs into CDC
emergency response plan
18
Future Research
1. In vitro experimentation with antiviral drugs
in Variola Major
2. Combining vaccine and drug therapy
3. Changing dosage schedules
19
Debate
 Proposed destruction in 1986 .
 Destruction postponed to 1993, and has been a resurfacing
issue ever since.
 Last visitation was in 2011
 Will be revisited again in 2014
20
REFERENCES
 http://www.emergency.cdc.gov/agent/smallpox/response plan/files/exec-sections-i-vi.pdf
 http://www.vassarstats.net/ sur vival.html
 http://www.ncbi.nlm.nih.gov/pubmed/ 16341204
 http://en.wikipedia.org/wiki/ Smallpox
 http://en.wikipedia.org/wiki/ Vaccinia
 http://www.cdc.gov/ncidod/monkeypox/factsheet2. htm
 http://www.nature.com/nature/journal/v439/n7077/extref/natu
re04295-s2.pdf
 http://en.wikipedia.org/wiki/ Dyspnea
 http://en.wikipedia.org/wiki/Real time_polymerase_chain_reaction
 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC130682/pdf/038
6.pdf
21