Tuberculosis Flashcards
Human TB history
- killed ~1billion people in the last two centuries
- BCG vaccine developed in 1921
- reoccurrence of TB mainly because of HIV/AIDS and resistances
- ~¹/₃ of world population is infected with Mtb
Pathology of TB
- Mtb in macrophage
- formation of granuloma -> latency
- old granuloma can become calcified (eradication) or necrotic
- necrotic granuloma can burst open -> caseous granuloma -> spread of Mtb
Mtb
- obligate human pathogen
- acid fast bacteria
- intra- & extracellular
- granuloma induction by Mtb in Mincle-/- mice
What is TDM (Trehalose-6,6-dimycolate)?
- TDM is most abundant lipid in cell wall & cord factor -> only virulent Mtb
- TDM is important for granuloma induction (Mincle is needed as factor for inflammation)
- Mincle recognises TDM
- no granuloma induced by TDM in Mincle-/- mice
Name the three animal models of TB and challenges
- mouse
- non.human primate
- zebrafish
challenge: many different stages -> no model mimics all stages
Name (dis-)advantages and routes of infection of the mouse model
advantages:
- many genetically altered strains
- easy to manipulate
- easy to handle
- drug & vaccine research
disadvantages:
- no latent infection
- death due to progressive primary TB
- no real granulomas
routes of infection:
- intraperitoneal
- intratracheal
- intravenous (high inoculation, systemic)
- aerosolization (delivery into lungs, more physiologically appropriate)
What murine parameters are analysed?
- bacterial replication in different organs
- lung pathology
- immunophenotyping using flow cytometry
- gene/protein expression
What role plays TNF in TB protection (mouse model)?
- key factor
- increases TB progression risk when receiving anti-TNF therapy (bedside observation)
- TNF is involved in maintenance and integrity of granulomas
- TNF can be soluble (sTNF) and membrane bound (memTNF)
- TNF and TNFRp55 important for early iNOS production
- granuloma necrosis only in TNF-/- or TNFRp55-/- mice
Where does a TNF antagonist play a role?
- treatment of inflammatory/autoimmune diseases (Crohn, arthritis,…)
- TNF-ABs with different variable regions
- chimeric AB -> murine vRegion and human Fc part
- humanized mAB -> human constant and variable region
- 2 extracellular domains of human TNFR2 fused to Fc part
- TNF-targeted treatment worsens TB in mice
Name (dis-)advantages of the non-human primate model
advantages:
- most useful model for latent TB
- wide range of pathology
- low dose infection 50/50 active/latent cases -> reactivation, more chronic course in active TB
disadvantages:
- costly
- lack of host genetic variants
- few tools to study immune response
Which role does TNF play in the non-human primate TB model?
- early infection -> TNF-neutralisation results in excessive, disseminated disease
- latent TB -> TNF-neutralisation causes reactivation
- similar granuloma in anti-TNF treated and non treated monkeys
- TNF-neutralisation results in dysregulation of critical cytokines
-> TNF might play a role in cellular integrity and localisation within the granuloma
Name (dis-)advantages of the zebrafish TB model
advantages:
- natural pathogen (m. marinum)
- sequenced genome
- short generation time
- easy generation of mutations (random & targeted)
- dissection of innate (embryo model) and adaptive (adult model) immunity
disadvantages:
- M. marinum not part of Mtb complex
- M. marinum doesn‘t induce pulmonary TB in humans
How to infect zebrafish embryos?
- injection in hindbrain ventricle -> recruitment of macrophages
- injection in caudal vein -> blood stream infection
- systemic infection
- multiple infection outcomes- bacteria per macrophage
- granuloma
- drug efficacy
What is the morpholino technique and how does it work?
main antisense knockdown technology in zebrafish
- splice blocking: binding to splice donor/acceptor site prevents splicosome assembly -> decay of immature mRNA
- translation blocking: binding to AUG or 5‘ UTR hinders scanning of 40S ribosome -> blocks translational initiation and elongation
What role does TNF play in the zebrafish TB model?
TNF maintains granuloma integrity indirect by restricting mycobacteria’s growth within macrophages and prevents their necrosis
