Infographic: TB Vaccines in the Pipeline Take Varied Approaches
Infographic: TB Vaccines in the Pipeline Take Varied Approaches

Infographic: TB Vaccines in the Pipeline Take Varied Approaches

More than a dozen vaccines for tuberculosis are currently being tested in clinical trials. Some use whole bacteria as BCG does, while others deliver protein subunits or genetic material carried by viral vectors.  

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Anthony King

Anthony King is a freelance science journalist based in Dublin, Ireland, who contributes to The Scientist. He reports on a variety of topics in chemical and biological sciences, as...

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Jul 1, 2021

ABOVE: © MESA SCHUMACHER

BCG, or the Bacille Calmette-Guérin vaccine, elicits a multipronged immune response that effectively fends off tuberculosis in children in developing countries, where the disease is still common. But the vaccine’s protection wanes with age, and the pathogen can infect adolescents and adults, causing a lung disease characterized by a persistent, sometimes bloody cough. Researchers aren’t sure which parts of the immune response are most critical for protection to be effective, and are taking varied approaches to improve on BCG with next-generation tuberculosis (TB) vaccines. One leading candidate shown here involves the same microbe as BCG, but with a few genetic tweaks that researchers hope will provide better protection. Another takes an entirely different approach with manipulated antigens from the BCG bacterium. Still other TB vaccines in the pipeline include live and killed whole mycobacteria of various species—including Mycobacterium tuberculosis, which causes tuberculosis—and viral delivery of the genetic recipe for mycobacterial antigens.

BCG

© Mesa Schumacher

This 100-old vaccine is a live but weakened form of a cattle bacterium that is related to Mycobacterium tuberculosis (Mtb)Inoculation attracts frontline immune cells to the site of the injection. Dendritic cells and other antigen-presenting cells display parts of the BCG microbe on their surface to drive a response by T cells, which fight future infection with the pathogen and train B cells to produce antibodies. Both BCG and Mtb go into vesicles called phagosomes, where they interfere and stop their own destruction. BCG however is eventually degraded, whereas Mtb survives for a long period of time within cells.


VPM1002 Whole-Cell Vaccine

© Mesa Schumacher

A genetically modified version of BCG is injected. Macrophages take up the bacterium into a phagosome, where it produces an enzyme that causes pores to form in the phagosome membrane. This allows antigens to leak out into the cytosol and trigger an inflammasome activation, in a similar way to Mtb, which BCG does not do.


M72 Protein Subunit Vaccine

© Mesa Schumacher

Two recombinant proteins from the Mycobacterium bacteria that constitute the BCG vaccine are fused together and injected. Fusion proteins are taken up by immune cells that then display them on their surfaces to trigger an immune response against the antigens. A proprietary GlaxoSmithKline adjuvant (AS01) boosts that immune response.

The Frontrunners

In addition to the vaccines pictured above, there are several others in late-stage trials, plus additional candidates in Phase 1 and in preclinical studies (not shown).

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Live vaccines

VPM1002: A live, attenuated BCG vaccine with a pore-forming protein from another bacterium that allows the flow of antigens and mycobacterial DNA out from the phagosome into the cytosol (see graphic)

BCG Revaccination: A booster shot of BCG

MTBVAC: A live, genetically weakened M. tuberculosis (first and only such vaccine to enter clinical trials) with mutations in virulence genes

Protein subunit vaccines

M72 + ASO1: A recombinant fusion protein consisting of two M. tuberculosis antigens and an adjuvant (see graphic above)

H56:IC31: A protein vaccine consisting of two early secretory proteins and a latency protein, together with an adjuvant

ID93/GLA-SE: Fusion of four M. tuberculosis virulence antigens, combined with an adjuvant

GamTBVac: A subunit vaccine that fuses two M. tuberculosis antigens with an adjuvant

Whole cell vaccines

DAR-901: An inactivated preparation of the related species Mycobacterium obuense, which does not cause disease (see graphic above)

MIP: An inactivated vaccine that consists of M. indicus pranii, a rapidly growing mycobacterium that does not cause disease

Vector-based vaccines

TB/Flu04L: A intranasally delivered live attenuated flu virus carrying two antigens from M. tuberculosis

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