Ralph S. Baric, PhD Professor: Epidemiology

University of North Carolina at Chapel Hill

No Approved Vaccines or Therapeutics for SARS-CoV or MERS-CoV Midst of an ongoing MERS-CoV Outbreak (950+ cases/40% mortality)

Theme • Impact of GOF Restrictions

– Emerging Coronavirus Vaccine/Therapeutic Research

• Focus: Two Stories

Restrictions will reduce public health preparedness to respond to future SARS-CoV-like outbreaks

Restrictions on animal model development increases the risk of vaccine induced immune pathology and mortality in human populations

• Debunk: Concept

That ethical and safe alternative experimental approaches exist that provide equivalent information as GOF studies

Demonstrate complexity of defining GOF research

Impact: Public Health Preparedness

SARS-CoV

Epidemic

Strains

SARS-CoV Epidemic 2002-2004; ~8,000 cases/~10% mortality Originated pool of related Bat CoV (5-30% sequence variation)

Since 2005, no new cases

Vaccines/Therapeutics: Target SARS-like prepandemic strains

Civet/Raccoon dog

SARS-like Viruses

Group 2b Coronaviruses Original

Vaccine Target

Sheahan T, J Virol 2011

Impact: Public Health Preparedness

SARS-CoV

Epidemic

Strains

SARS-CoV Epidemic 2002-2004 Originated pool of related Bat CoV (5-30% sequence variation)

Since 2004: no new reported cases (extinct?)

Recognition: Vaccines must target SARS-like pre-pandemic strains

Civet/Raccoon dog

SARS-like Viruses

CENTRAL QUESTIONS

Do any other bat SARS-like CoV have pre-

pandemic potential?

YES? Will existing SARS-CoV vaccines

and drugs work

Impact: Public Health Preparedness

SARS-CoV

Epidemic

Strains

SARS-CoV Epidemic 2002-2004 Originated pool of related Bat CoV (5-30% sequence variation)

Since 2004, no new reported cases

Recognition: vaccines must target SARS-like pre-pandemic strains

Civet/Raccoon dog

SARS-like Viruses

CENTRAL QUESTIONS: PREPAREDNESS

Do other bat SARS-like CoV have

pandemic potential?

YES? Will existing SARS-CoV vaccines

and drugs work?

Synthesized spike genes in red Ge et al., Nature 2013, Becker, PNAS 2008, Menachery, unpublished)

SARS MA

WIV-1 S

SHC014-S

HKU3-S

BtCoV 279-S

hACE2-

Expressing

Cells

Pseudotype

INFECT

YES (5/5)

YES (3/5)

NO (0/5)

NO (1/5)

NO (1/5)

hACE2-

Expressing

Cells

Chimeric

INFECT

YES (5/5)

YES (3/5)

YES (0/5)

NO (1/5)

NO (1/5)

Recombinant

Virus

Lethal

ND

ND

Attenuated

Attenuated

Mouse

Virulence

Cross-Neut

SARS hmAB

4/4

2/4

0/4

ND

ND

SARS

Vaccines

Protect

Aged

YES

No

No

No*

No*

Potential

Threats SHC014 and WIV-1 have

same growth phenotype

as wildtype SARS-CoV

PSEUDOTYPES + STRUCTURE-

BASED PREDICTIONS FAILED

TO IDENTIFY SHC014

Different S Pseudotype

CoV S

Conserved virus-ACE2 receptor

contact interface residues Ge et al., Nature 2013 Menachery, unpublished

“Ethical

Alternative”

SARS MA

WIV-1 S

SHC014-S

HKU3-S

BtCoV 279-S

hACE2-

Expressing

Cells

Pseudotype

INFECT

YES

YES

NO

NO

NO

hACE2-

Expressing

Cells

Chimeric

INFECT

YES

YES

YES

NO

NO

Recombinant

Virus

Lethal

Attenuated

Attenuated

Mouse

Virulence

Cross-Neut

SARS hmAB

4/4

2/4

0/4

SARS

Vaccines

Protect

Aged

YES

No

No

Loss of

Virulence

Function

Vaccines

fail in 1 yr

aged mice

hmAB

therapy

fails

Pseudotype

CoV S

Group 2b Coronaviruses

Greatest Pandemic

Threat Potential

No Vaccines or hmAB!

We are Vulnerable!

Emerging CoV Pandemic Preparedness

Low Risk

High Risk

Many Chimeric Viruses: the definition implied in GOF is much too broad and must be redefined

GOF: Public Health Implications SARS Extinct? No

• Unequivocally established that some natural SARS-

like CoV bat strains:

– Pre-pandemic potential

• Results are generalizable to other zoonotic viruses

– Like Bat MERS-like CoV

– Framework: to establish risk and prioritize basic and

applied research

• Information to policy makers:

– SARS-like outbreaks are likely in the future

– Existing therapeutics and vaccines may fail (unprepared)

– Reagents exist to devise effective interventions

Importance of Animal Model Development

to Vaccine Development SARS-CoV replicates poorly in mice (~106)

No weight loss or clinical disease

Little if any pathology

Every vaccine developed works in the model

Development of Mouse Adapted Strains: 6-10 changes

Poor engagement

of mouse ACE2

receptor

More S Gene Mutations More in vivo

passages mACE2 usage

Captures many SARS human disease phenotypes

ARDS

2 logs increased titer

Phenocopy human in vivo tropism

Age-related disease severity

Theme: In vivo correlates of protection vary depending on model Frieman M, J Virol 2012; Roberts, A., Plos Pathogens 2007

Importance of Animal Model Development

to Vaccine Development SARS-CoV replicates poorly in mice (~106)

No weight loss or clinical disease

Little if any pathology

Every vaccine developed works in the model

Development of Mouse Adapted Strains: 6-10 changes

Poor engagement

of mouse ACE2

receptor

More S Gene Mutations More in vivo

passages mACE2 usage

Captures many SARS human disease phenotypes

ARDS

2 logs increased titer

Phenocopy human in vivo tropisms

Age-related disease severity

Insights into pathogenic mechanisms

Theme: In vivo correlates of protection vary depending on model

DIV SARS Vaccine

Protects in young mice inoculated with wildtype SARS-CoV

(replication model)

What happens after SARS MA Challenge?

Vaccine fails to protect, especially in elderly

Induces a Th2 Immune Pathology: BAD

Eosinophils

Deming, Plos Med 2006; Yasui, J. Immunol 2008; Bolles, J Virol. 2011; Tseng, Plos One 2012

DIV Performs: Models of Outbred Humans

Collaborative Cross Mice (musculus, castaneous, domesticus)

8 Founder Lines→64 F1 diallel combinations

Age: 1 year, vaccinate half with DIV, challenge with virus (~1860 mice)

Mock-vaccinated controls co-housed with challenged animals

No evidence of

transmission In

vulnerable inbred and

outbred populations

Models of Outbred Human Populations

Collaborative Cross Mouse Resource 8 Founder Lines→64 F1 diallel combinations

Age: 1 year, vaccinate half with DIV, challenge with virus (~1860 mice)

Mock-vaccinated controls co-housed with challenged animals

No evidence of

transmission In

vulnerable inbred and

outbred populations

SARS DIV

Seen with other vaccine formulations

Other CoV → Vaccine Complications

Robust animal models are essential

for vaccine/drug development, safety

testing and performance outcomes

Schaefer et al., unpublished

MERS-CoV Animal Model Development

MERS-CoV does not replicate in mice/small animals!

In vivo passage also fails

Transgenic mice developed: hDPP4 receptor

Replication model, very limited clinical disease

Passage is required to isolate mouse adapted strains that

reproduce human disease phenotypes

HALTED: In the midst of an ongoing epidemic!

Public Health vaccine development has been

compromised! No robust small animal models exist: testing of vaccines/drugs--delayed

Critical: MERS-CoV restrictions be lifted immediately

Summary Dangerous Times:

Human populations are being sampled by four

highly pathogenic viruses

H5N1, H7N9, MERS-CoV, Ebola Virus

International Travel: Allows for immediate worldwide dissemination of

newly emerged viruses

Only going to get faster--more frequent

Response Times: Compressed Strategies exist to develop broadly effective

interventions prior to future disease outbreaks

GOF is a crucial tool for public health

preparedness