Potential prophylactic BCG Potential prophylactic BCG Prime-booster Prime-booster

Gaëlle NoëlKidist Bobosha

Subgroup A2

March 16th, 2011

Enhance and prolong the protective Enhance and prolong the protective immunity induced by BCG immunization immunity induced by BCG immunization

GoalGoal GoalGoal

Live attenuated strain of Mycobacterium bovis Protects children from severe forms of TB (milliary and

meningitis) Safe and inexpensive Over 3 billion people got the vaccination globally

Limitationso BCG protection wanes through timeo Does not prevent against pulmonary disease in adultso Does not protect against re-occurrence or latencyo Repeated BCG vaccination failed in enhancing

immunityo Risk of disseminated BCG in HIV-infected childreno Interferes with Tuberculin-Skin-Test

BCG vaccineBCG vaccine BCG vaccineBCG vaccine

Safe

Cost effective

Long term protection

Prevention of infection: pre exposure

Prevention of reactivation: post exposure

General aims of TB vaccinationGeneral aims of TB vaccination General aims of TB vaccinationGeneral aims of TB vaccination

Best strategies are subunit boosters like:

Protein/ fusion protein

Recombinant viral vector

DNA vaccine

Prophylactic heterologous prime-Prophylactic heterologous prime-boostboost

Prophylactic heterologous prime-Prophylactic heterologous prime-boostboost

Boosting BCG

New vaccine

Fusion proteinFusion protein Fusion proteinFusion protein

SafeReproducibleCan be freeze-driedNot expensiveNot compromised by BCG or environmental

mycobacteria exposure

… But needs adjuvant

…Why notDNA vaccine : delivery system (complex and costy)Live viral vector : previous exposure, expensive

5-10 % of active TB disease

90-95 % of latent TB infection

Multi-stage fusion proteinMulti-stage fusion protein Multi-stage fusion proteinMulti-stage fusion protein

Ag85A protein (Rv3804c)

Ag85A protein (Rv3804c)

Part of the Ag85 complex (Ag85A, Ag85B and Ag85C)

Shared by BCG and Mtb true booster

Mycolyl transferase A: enzyme involved in the cell wall synthesis

Largely expressed

Secreted and also retained in the cell membrane during early stage of infection

Ag85A/B largely used in new vaccine candicates for their immunogenic capacity

Preclinical data demonstrated:

Large proportion of memory CD4 T cells in the lung recognize Ag85A in young mice (Cooper et al., 1997)

Significant Th1-type cytokine production by splenocytes and significant CTL activity against Ag85A and Ag85B in mice (Lozes et al., 1997)

Ag85A protein (Rv3804c)

Ag85A protein (Rv3804c)

Ag85A has the potential to boost existing memory immunity in BCG-vaccinated mice - Lung tissue damage dramatically reduced (Brooks et al., 2001)

Rv2660c proteinRv2660c proteinRv2660c proteinRv2660c protein

Starvation protein Belongs to the Region of Differences RD11 Deleted in BCG

Preclinical/Clinical data demonstrated:

Govender et al., 2010:• Expression shown to be associated with non-replicating persistence in vitro• Persons with latent TB infection preferentially recognize Rv2660 and induced IFN-γ

production in a greater proportion compared with patients with TB disease (ex vivo experiments by using patients’ PBMC)

Betts et al., 2002:• Expression increased in nutrient-starved cultures (300 fold change)

– Effective in the late persistent stage– In the late persistent stage of infection, the effect of adding Rv2660c was

particularly pronounced

Aagaard et al., 2011

• Immune response against Rv2660c increases during persistent stage

• Having Rv2660c in a fusion protein increases protection in late stage

Rv2660c proteinRv2660c proteinRv2660c proteinRv2660c protein

Belongs to the PPE protein family Secreted by the type VII secretion system encodes by

ESAT-6 loci

Romano et al., 2008• PPE44-specific immune responses in acutely, chronically

and latently Mtb infected mice

• PPE44 vaccinated mice showed B and T cell responses with IFN- and IL-2 release

• PPE44 seems to be protective

PPE44 proteinPPE44 protein(Rv2770c)(Rv2770c)

PPE44 proteinPPE44 protein(Rv2770c)(Rv2770c)

IC31IC31®® adjuvant adjuvantIC31IC31®® adjuvant adjuvant

Intercell productCationic particles composed of:

Antimicrobial peptide (KLKL5KLK) TLR-9 ligand Oligonucleotide (ODN1a)

Combined at a molar ratio of 25:1, respectively

Generates a strong Type 1-dominant humoral and cellular immune response with induction of CTL (Schellack et al., 2006)

Able to slowly release antigen: two month depot effect of IC31® may allow single shot protection (Schellack et al., 2006)

Used and seen to be safe Mouse subcutaneous injection (Schellack et al., 2006) Guinea pig intramusculary (Skeiky et al., 2010) Human intramusculary injection (up to 500 nmol KLK +

20 nmol ODN1a) (Dissel et al., 2010)

+ IC31® adjuvant

Ag85A

Rv2660c

PPE44

PFP PFP A multi-stage BCG booster A multi-stage BCG booster

candidatecandidate

PFP PFP A multi-stage BCG booster A multi-stage BCG booster

candidatecandidate

Thank you for your attention…Thank you for your attention…