Peter L. Collins, PhD National Institute of Allergy and Infectious Diseases

National Institutes of Health, USA

Live attenuated pediatric RSV vaccines

(NIAID program)

Immunostained RSV filaments on

the surface of a syncytium

Infant with RSV disease

NIAID

Two live RSV vaccine approaches

Live-attenuated strains of RSV (in part with MedImmune)

Live-attenuated HPIV1, 2, and 3 as vectors to express RSV

antigen from an added gene

Can rational design (reverse genetics) provide improved candidates?

Live RSV vaccines to be given to RSV-naïve infants

- Based on RSV strain A2 (subgroup A)

- Intranasal administration

Objective

Disadvantage

• Infectious agent: must attenuate but retain immunogenicity

• Free of RSV disease enhancement seen with inactivated and subunit RSV vaccines

- Formalin-inactivated RSV: 80% hospitalization rate, 9% mortality

- Also observed with purified RSV subunits in experimental animals

- Not observed with live-attenuated and live-vectored vaccines

• IN administration, needle-free, direct stimulation of local as well as systemic immunity

- E.g., secretory antibodies; lung-resident memory T cells

- Greater restriction of transmission

• Adjuvant-free; a single dose is substantially immunogenic

More amenable to achieving rapid protection early in life

• Broad stimulation of innate, cellular, humoral immunity

• Live vaccines give broader, more effective immunity in virus-naïve recipients

Advantages

Live-attenuated and live-vectored RSV vaccines

Three attenuated RSV strains in clinical studies

P G F M L NS1 NS2 SH M2 N ∆M2-2

• Deletion of RNA regulatory protein yields increased gene transcription, decreased genome

replication

• Expect gene deletion to be highly stable

• Increased antigen expression may increase immunogenicity

SH cp cp cp cp

P G F M L NS1 NS2 SH M2 N

cp

404 248

stabilized 1030

cps2

• Highly temperature sensitive, provides increased restriction in LRT

• Attenuation mainly involves temperature sensitivity point mutations

• Increased genetic/phenotypic stability, but still an issue

(“stabilized” version of rA2cp248/404/1030∆SH, of Karron et al, 2005)

P G F M L NS1 NS2 SH M2 N ∆NS2∆1313

NS2 ∆1313

• Deletion of IFN antagonist may provide increased immunogenicity

• Deletion of L residue 1313 confers a moderate ts phenotype

• Deletions yield increased stability

I1314L

• NS2 also appears to be a virulence factor Liesman et al, J Clin Invest 2014

HPIV1, 2, and 3 as vectors for RSV-F protein

N P M F HN L

RSV F

Provides bivalent HPIV + RSV vaccine; increase breadth of protection against RT disease

HPIVs replicate in vitro to titers 10- to 100-fold greater than RSV

Avoids the physical instability of RSV

Can express forms of RSV F designed for greater immunogenicity but are

non-functional (i.e., stabilized pre-fusion F; post-fusion F)

Provided better boosts in rodents than re-dosing with an attenuated RSV

Attenuated HPIVs may be less reactogenic than attenuated RSV

Disadvantage: provides only 1 RSV antigen

Advantages compared to attenuated RSV strains

e.g. B/HPIV3

Bovine backbone with human F and HN genes

Modified versions of RSV F (into B/HPIV3)

(all GeneArt-codon-optimized, HEK)

DS (pre-fusion)

DS-Cav1 (pre-fusion)

RSV F protein

∆FP

Post-fusion

CT

CT TM TM, CT from BPIV3 F protein CT

TM CT

Jason McLellan Barney Graham Peter Kwong

S155C S290C

S155C S290C S190F V270L

CT

CT TM DS-Cav1 CT

DS CT

TM CT DS TM CT

S155C S290C

S155C S290C S190F V270L

DS-Cav1 TM CT

∆TM, ∆CT

Rhesus study

DS (pre-fusion)

DS-Cav1 (pre-fusion)

RSV F protein

∆FP

Post-fusion

CT

CT TM

CT

TM CT

S155C S290C

S155C S290C S190F V270L

CT

CT TM DS-Cav1 CT

DS CT

TM CT DS TM CT

S155C S290C

S155C S290C S190F V270L

DS-Cav1 TM CT

∆TM, ∆CT

N=5

N=4

Plus: unmodified F protein control

N=5

The epidemiology of the HPIVs suggest optimal times of vector use

0 1 2 3 4 5 6 7 8 9 10 11 12

RSV

HPIV1, 2

HPIV3

15 18 21 age

(months)

24

Attenuated RSV strain

HPIV3-based

vector

HPIV1-, 2-based

vectors

Seasonal?

Ulla Buchholz

Cindy Luongo

Shirin Munir

Bo Liang

Lijuan Yang

Tom McCarty

Sonja Surman

Emerito Amaro-

Carambot

Brian Murphy

Steve Whitehead

LID/NIAID

Contributors to the present clinical studies:

MedImmune

Center for Immunization

Research, Johns Hopkins

Ruth Karron

Betty Schappell

Bhavin Thumar

Karen Loehr

Et al.

IMPAACT

(International Maternal,

Pediatric, Adolescent,

AIDS Clinical Trials Group)

Coleen Cunningham

Betsy McFarland

George Siberry

Devasena

Gnanashanmugam

Et al.

LID alumni

NIAID RCHSPB (DCR)

NIAID Comparative Medicine Branch

Clinical study participants and their families

VRC/NIAID

Jason McLellan

Barney Graham

Peter Kwong

Seattle Children’s Hospital

Janet Englund