Clinical trials of an oral inactivated ETEC vaccine (ETVAX) in - - PowerPoint PPT Presentation

Clinical trials of an oral inactivated ETEC vaccine (ETVAX) in children in developing countries and in travelers Ann‐Mari Svennerholm

Department of Microbiology and Immunology The Sahlgrenska Academy University of Gothenburg (UG)

ECMIS , Ghent June 5, 2019

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Enterotoxin‐producing E. coli (ETEC) – important global diarrheal pathogen in humans

ETEC is one of the most common causes of diarrhea in ……… children ≤ 5 years in developing countries

• ETEC causes several hundred million cases and >50.000

diarrheal deaths annually

• Repeated ETEC diarrheas may cause undernutrition,

retarded growth and decreased cognitive functions

‐

ETEC is also the most common cause of diarrhea in travellers

80 M 28 M 12.6 M

20 ‐ 50 % of all diarrheas in travellers are caused by ETEC

Why is no human ETEC vaccine available yet?

Large heterogeneity of diarrheagenic ETEC and lack of robust immunological markers of protection makes vaccine development complicated

Enterotoxins:

LT (~40%), ST (STh and STp; ~30%), LT+ST (~30%)

Colonization factors (CFs):

> 25 CFs; CFA/I and CS1‐CS7, CS14 and CS17 on 50‐80% of all ETEC strains ( Gaastra &Svennerholm 1996)

O‐antigens: >70 in ETEC

Putative protective surface antigens: e.g. EtpA, EatA, flagellin, TibA (Fleckenstein et al)

+ ±

CFA/I CS3

CS6

CS5

LCTBA

The ETEC vaccine, ETVAX, developed at UG in collaboration with Scandinavian Biopharma, Stockholm

1011 recombinant bacteria +1mg toxoid 10 µg dmLT

• verexpressing CFs

(Lebens , Holmgren et al) ( J Clements et al) (Tobias & Svennerholm)

Multivalent ETEC vaccine (ETVAX) dmLT adjuvant

Evaluation of ETVAX in Phase I double‐blind placebo‐ controlled studies in adult Swedes

Four groups with altogether 129 subjects receiving:

• A. Placebo (bicarbonat buffer only); n=34
• B. ETVAX alone; n=35
• C. ETVAX + 10 µg of dmLT; n=30
• D. ETVAX + 25 µg of dmLT; n= 30

Boosting groups A‐C with single dose ETVAX 1‐2 years later

Is ETVAX safe ?

• No significant differences in side‐effects between vaccinees and placebos

Can ETVAX induce?:

• Mucosal immunse responses: SIgA antibody responses fecal extracts and

…intestine ‐ derived circulating antibody secreting cell (ASC/ALS IgA) responses

• Serum antibody responses against the primary vaccine antigens
• Cross‐reactive immune responses against other CFs than those in the vaccine
• Immunologcal memory

Subjects responding to Placebo ETVAX alone ETVAX + 10 µg dmLT ETVAX + 25 µg dmLT

All Vaccinees n=95 ≥ 4 antigens 0% 91% 87% 85% 87% 5 antigens 0% 74% 83% 75% 77%

Frequencies of responders to two oral doses of ETVAX against the five primary vaccine antigens (CFA/I, CS3, CS5, CS6 and LTB)

Mucosal ALS IgA and/or fecal SIgA immune responses against ETVAX antigens in adult Swedes

.

A Lundgren et al, Vaccine 2014

Induction of cross‐reactive mucosal immune responses against CFs not included in the vaccine in adult Swedes

ALS IgA

CFA/I Group CS5 Group Vaccine CFs Non-vaccine CFs Vaccine CFs Non-vaccine CFs

Fecal SIgA

CFA/I CS14 CS1 CS17 50 100 %

21/21 15/21 15/21 15/21

CS14 CS1 CS17

14/14

50 100 %

9/14 11/14 9/14

CFA/I CS5 CS7

17/17

50 100 %

15/17

CS7

14/14

50 100 %

10/14

CS5

S Leach et al, 2017

CFA/I

0 4/5 7 0 4/5 7 0 4/5 7 10 30 3

Group I Group II Group III

Day:

E L IS A u n its (G M + S E M )

CS3

4/5 7 4/5 7 4/5 7 10 30 3 100 Day:

Group I Group II Group III E L IS A u n its (G M + S E M )

CS5

0 4/5 7 0 4/5 7 0 4/5 7 10 3 Day: 5

Group I Group II Group III E L IS A u n its (G M + S E M )

CS6

0 4/5 7 0 4/5 7 0 4/5 7 10 3 Day: 5

Group I Group II Group III E L IS A u n its (G M + S E M )

P=0.06 P=0.03 P=0.004 P=0.006 P=0.01 P=0.006

RF: 13% 63% P=0.003 59% P=0.004 RF: 26% 69% P=0.019 88% P<0.001 RF: 13% 69% P<0.001 59% P=0.004 RF: 13% 56% P=0.009 53% P=0.01

P=0.07 P=0.03

Immunological memory responses:

Higher and earlier appearing ALS responses were induced by a single dose of ETVAX in previously (1‐2 years earlier) vaccinated ( Gr II and III) compared to in naive (Gr I) Swedish adults

Lundgren, Jertborn & Svennerholm, 2016

Phase I/II study of ETVAX in descending age groups in Bangladesh Main Objective : Safety: To identify the highest safe and immunogenic dose of

ETVAX +/‐ dmLT adjuvant

Secondary objective: Immunogenicity: To determine immune responses against the

…………. five primary ETVAX antigens (CFA/I, CS3, CS5, CS6 and LTB)

Mucosal immune responses ‐ IgA antibodies in ALS specimens ‐ SIgA /total SIgA antibodies in fecal extracts Systemic immune responses ‐ IgA and IgG antibodies in plasma Can dmLT adjuvant enhance immune responses?

PART A: 18-45 years, inclusive Cohort ETVAX dmLT N A1 Full dose

• 15

Full dose 10 ug 15 Placebo 15 Total 45 PART B: 24-59 months, inclusive Cohort ETVAX dmLT N B1 ¼ dose

• 15

Placebo

• 10

B2 ½ dose

• 15

Placebo

• 10

B3 Full dose

• 15

Placebo

• 10

B4 ½ dose 2.5 µg 15 Placebo

• 10

B5 ½ dose 5 µg

15

Placebo

• 10

B6 ½ dose 10 µg 15 Placebo

• 10

Total 150 PART C: 12-23 months, inclusive Cohort ETVAX dmLT N C1 ¼ dose

• 15

Placebo

• 10

C2 ½ dose

• 15

Placebo

• 10

C3 ½ dose 2.5 µg 15 Placebo

• 10

C4 ½ dose 5 µg 15 Placebo

• 10

Total 100 PART D: 6- 11 months, inclusive Cohort ETVAX dmLT N D1 1/8 dose

• 15

Placebo

• 10

D2 ¼ dose

• 15

Placebo

• 10

D3 ½ dose

• 15

Placebo

• 10

D4 ¼ dose 2.5 µg 15 Placebo

• 10

D5 ¼ dose 5 µg 15 Placebo

• 10

Total 200

Phase 1/II trial of ETVAX in Bangladesh (495 subjects )

F Qadri, A‐M Svennerholm et al

Meso Scale Discovery (MSD) Sulfo‐tag Carbon based plate with electrodes

Introduction of a new approach to assess ALS responses by an electrochemiluminescence assay

Main benefits of ECL assays compared to ELISA:

• High sensitivity – small sample volumes required (5 µl/analysis), e.g for use in young children
• Wide dynamic range – no sample titration required

Light

Vaccine specific antibody

Lundgren & Svennerholm

0.1 1 10 100 1000 0.1 1 10 100 1000

ELISA (fold rises)

Excellent correlation between ALS IgA responses by ELISA and ECL MSD assay

(Immune responses to CFs and LTB in adult Bangaldeshis given ETVAX d ± dmLT or placebo)

r=0.90 P<0.0001

0.1 1 10 100 1000 0.1 1 10 100 1000

ELISA (fold rises)

CFA/I (day 19) CS3 (day 19)

r=0.91 P<0.0001

ELISA (fold rises) ELISA (fold rises) MSD (fold rises) MSD (fold rises) Akhtar, Lundgren et al Vaccine 2018

CS6 (day 19) LTB (day 19)

MSD (fold rises) r= 0.91 P< 0.0001 r= 0.95 P< 0.0001 MSD (fold rises)

MSD (fold rises) MSD (fold rises) ELISA (fold rises) ELISA (fold rises)

CFA/I

Strong and specific ALS IgA responses against CFs and LTB in adult Bangladeshis given two doses of ETVAX ± dmLT or placebo (determined by the ECL MSD assay)

CS3 LTB

Responder freq: 0% 100% 100% Also strong responses to CS5 Responder freq: 7% 100% 100% Responder freq: 0% 100% 100% Akhtar et al 2018

CS6

Responder freq: 7% 100% 100%

CFA/ I LTB CS6

Pre Day 7 Day 19 Pre Day 7 Day 19 Pre Day 7 Day 19

Placebo Vaccine Vaccine + dmLT

10 100 1000

IgA (ELISA titer) Pre Day 7 Day 19 Pre Day 7 Day 19 Pre Day 7 Day 19

Placebo Vaccine Vaccine + dmLT

10 100 1000 10000

IgA (ELISA titer)

Frequent IgA responses in plasma against CFs and LTB in adult Bangladeshis: given two doses of ETVAX +/‐ dmLT or placebo day 0 and 14

Akhtar et al 2018

A phase 2b trial of ETVAX in Finnish travelers to Benin

(PI Anu Kantele, University of Helsinki)

A double – blind, placebo‐controled study in 800 volunteers to evaluate:

• Safety
• Immunogenicity (serum antibody responses )
• Protection against mild‐moderate ETEC diarrhea with ETEC as
• nly pathogen

Volunteers were given 2 doses of ETVAX or placebo (buffer only) 2 weeks apart in Finland 1‐2 weeks before departure Surveillenc for diarrhea was conducted during stay in Benin for 12 days + one week after return to Finland

Thank you!

ETEC group GU

Stiftelsen för Strategisk forskning

ETEC group icddrb;

F Qadri et al L Bourgeois, R Walker, N Bauer et al B Sjöstrand & N Carlin Jan Holmgren GU, Institute of Biomedicine, Sahlgrenska Academy