New Avenues for Vaccine Development

David Wallace

ARC-Onderstepoort Veterinary Institute, South Africa

S

M

L

Nc NSs

G2/Gn G1/Gc

L

NSm

Virus structure and genomic layout

(Van Regenmortel et al., 2000)

(Freiberg et al.,

2008)

Experimental vaccines:

(Clone 13) NSs-defective clone (IFN antagonist)

MV P12 (ZH548) – mutagen-induced changes (segments M & L)

R566 (Clone 13 + MV P12 – reassortment)S segment Clone 13 and L & M of MV P12

- Safer, much less chance for reversion via reassortment with virulent

strains in the field

Experimental vaccines - alternatives :

- Subunit

- DNA

- Reverse Genetics

- Virus-vectored

Experimental vaccines (continued) :

Subunit (Schmaljohn et al., 1989, Wallace et al., 2006)

- baculovirus : Gn & Gc - good protection in mice

- E. coli : tGn - good protection in miceNC - partial protection in mice

DNA (Spik et al., 2006; Wallace et al., 2006; Lorenzo et al.,

2008)

- GPs +NSm - poor antibody response & protection- GPs -NSm - good antibody responses & protection- NC - good and long-lasting antibodies (but,

low neutralising)

Experimental vaccines (continued) :

Reverse genetics

(Gerrard et al., 2007; Bird et al., 2007; Won et al., 2007;

Bird et al., 2008)

RVFV genome

L - 6404

M - 3885

S - 1690

RVFV genomes

amplified and

sequenced using

Roche’ GS technology

(ARC-OVI)

(Dr Christiaan Potgieter)

The Terry Dermody reverse genetics strategy for

reovirus

The Terry Dermody reverse genetics strategy for

reovirus (continued)

Experimental vaccines (continued) :

Reverse genetics (Bird et al., 2008)

Deleted NSs gene alone or with NSm (EGFP-tagged)

– fully protected rats

– good DIVA properties (lack of NSm antibodies)

Experimental vaccines (continued) :

Virus-vectored:

Sindbis-replicon vectored (Heise et al., 2009)

(Express GP genes : 100% protection in mice, good Nab levels in sheep)

Pox-vectored: VV (Collett et al., 1987) &

LSDV (Wallace & Viljoen, 2005;

Wallace et al., 2006)

Advantages of LSDV-vectored vaccines :

Vector: live, attenuated, stable, immunity

Dual potential: LSDV, SPV, GPV

Marker vaccine - DIVA

Potential human vaccine? (e.g. rLSDV-RVFV)

Lumpy skin disease virus-vectored

RVFV experimental vaccine

TKL TKR

RVFVGnGcp7.5K p7.5K

E.coli

gpt p11K

EGFP

X 40

X 100

0

10

20

30

40

50

60

70

80

90

100

#1 #2 #3 #4

Day 0

Day 21

Day 31

RVFV IgG ELISA and mouse challenge studies

RVFV

SB vaccine

Ave

rag

e P

P v

alu

es*

rLSDV

-RVFV

rLSDV

-BEFV

Saline

control

POST-CHALLENGE

SURVIVAL RATE

* percentage positive

of SB positivecontrol

5/5 5/5 1/5 1/5

rLSDV-RVFV challenge trial in sheep –

Temperature reactions

38.5

39.0

39.5

40.0

40.5

41.0

41.5

-2 -1 0 1 2 3 4 5 6 7 8 9

TIME (Days post challenge)

TE

MP

ER

AT

UR

E (

° C

)

#760 (rLSDV - 7 log) #680 (rLSDV - 7log) #841 (rLSDV - 7log)#662 (PBS) #959 (OBP RVFV vac) #957 (OBP RVFV vac)#674 (PBS) #677 (rLSDV - 6log) #667 (rLSDV - 6log)

-20.00

0.00

20.00

40.00

60.00

80.00

100.00

0 7 14 21 28 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49

TIME (days post-vaccination)

PP

valu

es

#667 ( rLSDV - 6log) #677 (rLSDV -6log) #760 (rLSDV - 7log)

#680 (rLSDV - 7log) #841 (rLSDV - 7log) #674 (PBS)

#662 (PBS) #959 (OBP RVFV vac) #957 (OBP RVFV vac)

rLSDV-RVFV challenge trial in sheep –

RVFV-specific antibodies

Current work :

- Removal of selection marker genes (GALVmed funded)

- Removal of putative immunomodulatorygenes (ourselves and CIRAD)

- Planning combined animal trials

Conclusion :

- Many different types of new “vaccines”and delivery systems (e.g. plants, VEE, canarypox)

- New technologies (e.g. nanoparticles)

- New generation adjuvants

- Likely that more than one will require full development due to differing needs (e.g. governmental policies etc.)

FIN!

Acknowledgements:

Dr Bjorn Reininghaus – for photo in opening slide

Dr Christiaan Potgieter – slides and helpful discussions

ARC-OVI Directorate – funding for attendance at this meeting

POX-VECTORED VACCINES?

Use of a poxvirus (e.g. LSDV) as a vehicle for the expression of immunogenic proteinsof a pathogen in specific target animals to confer protection against the pathogen.

LSDV expressing the F and HA genes of RPV – dual protection

(Romero et al., 2003)

Important considerations :

- Efficacy (saftey in animals/humans, recombinantion/revertence)

- Type and duration of immunity

- DIVA (marker vaccine)

- Geographical region (indigenous vsexotic)

3.2 million cattle with LSD in Egypt in 2006.

400 000 deaths.

A solution:

• LSDV – developed as vaccine vector

• SA OBP vaccine strain proven track-record.

• Good results in animal trials (e.g. rLSDV-

RVFV)

Construct description:

• LSDV SA OBP vaccine

• Vaccinia virus p7.5K promoter

• Positive selectable marker gene: gpt

• Visual marker gene: EGFP

Next stage:

• Remove of putative immunomodulatory genes (for improving immune responses – antibody levels, duration etc.)

S

M

L

NC NSs

G2/Gn G1/Gc

L

NSm

RVFV genomic layout