Guidelines for Preventing Opportunistic Infections Among Hematopoietic Stem Cell Transplant Recipients

Discovered: A Potential Vaccine To Prevent Tuberculosis In People Of All Ages

TB remains the leading cause of death by infectious disease globally, with South Africa having one of the highest incidence rates in the world.

While the BCG vaccine used to prevent TB is widely available for infants, no vaccine has shown lasting protection. The BCG is also the only existing effective vaccine.

"South Africa committed to the Sustainable Development Goal of ending the TB epidemic by 2030. While we are doing relatively well as a country – TB deaths have come down since 2015 – we need to do a lot better to reach the milestones," says Professor Bavesh Kana.

Kana, the Head of the School of Pathology and former director of the Centre of Excellence for Biomedical TB Research at Wits University, contributed to the groundbreaking study.

Researchers sought to modify the BCG vaccine to make it more effective at controlling the growth of M. Tuberculosis.

Mice injected with the edited BCG vaccine had less M. Tuberculosis growth in their lungs than mice that received the original vaccine.

"We can now offer a new candidate vaccine in the fight against this deadly disease," says Kana. "The work also demonstrates that gene editing is a powerful way to develop vaccines. This is particularly important for researchers working on vaccine development."

About the tuberculosis vaccine

The BCG vaccine is given to children around the time of birth and is effective at preventing TB disease.

However, BCG does not protect teenagers and adults and has not been effective at eradicating TB.

This has spurred the need to develop novel TB vaccine candidates to replace or boost BCG.

"We also see that the BCG can evade the immune system and that this reduces its efficacy as a vaccine," says Kana.

He noted that the importance of vaccines cannot be overstated.

When humans get sick, their body's defence system spots particular signs, called PAMPs (pathogen-associated molecular patterns), on the outside of bacteria, viruses, or other harmful germs.

This helps the body tell the difference between invaders and its own cells and then starts fighting the infection.

Vaccines work by looking like germs, so that they can start the first defence without making a person sick.

Kana has lamented the funding gap in developing tools to eliminate TB – a disease which dates back over 9000 years.

"Until recently, our diagnostic approaches were a century old. With some novel vaccine candidates in the pipeline, we can finally begin to adequately address this devastating illness."

Method of Research

Observational study

Subject of Research

Animals

Article Title

A modified BCG with depletion of enzymes associated with peptidoglycan amidation induces enhanced protection against tuberculosis in mice

Article Publication Date

19-Apr-2024

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IISc Researchers Find Better Way To Take On TB Bacteria

ByGarima PrasherGarima Prasher / Updated: Jun 26, 2024, 06:00 IST

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3D hydrogel culture system will track, study TB infection in lungs & help improve treatment efficacy

In an effort to improve the treatment of tuberculosis (TB), researchers from the Indian Institute of Science (IISc) have come up with a 3D hydrogel culture system that provides a platform to track and study how tuberculosis bacteria infect lung cells. This technique will also help researchers test the efficacy of available treatments for the disease. "It is a very old bug, and it has evolved with us quite a bit," said Rachit Agarwal, associate professor at the Department of Bioengineering (BE), IISc, and corresponding author of the study published in Advanced Healthcare Materials. Agarwal added that they have already filed an Indian patent for their 3D culture, which can be scaled up by industries and used for drug testing and discovery. "The idea was to keep it quite simple so that other researchers can replicate this," he said.

Researchers say Mycobacterium tuberculosis (Mtb) is a dangerous pathogen that primarily infects the lungs. In 2022, it affected 10.6 million people and caused 1.3 million deaths, according to the World Health Organization. However, the current culture models used to study Mtb infection have several limitations. They do not accurately mimic the 3D microenvironment inside the lungs. The 2D culture plates are also extremely hard compared to the soft lung tissues. "The microenvironment experienced by the cells in such 2D culture is vastly different from the actual extracellular matrix (ECM) surrounding lung tissue. In the currently available culture model to study Mtb, tissue culture plate, there are no ECM molecules, and even if a very thin layer of ECM is coated on these plates, the lung cells 'see' the ECM on one side at best," explained Vishal Gupta, PhD student at BE and first author.

The 3D hydrogel culture system, on the other hand, allows researchers to track how the bacteria infect lung tissues. The team tracked the infection's progress over two to three weeks and found that the mammalian lung cells stayed viable for three weeks in the hydrogel, while current cultures are only able to sustain them for four to seven days.

Researchers Vijaya V Vaishnavi (left) and Vishal K Gupta (right)

The researchers then carried out RNA sequencing of the lung cells that grew in the hydrogel and found that they were more similar to actual human samples compared to those in traditional culture systems. The team also tested the effect of pyrazinamide (one of the four most common drugs given to TB patients). They found that even a small amount (10 µg/ml) of the drug was quite effective in clearing out Mtb in the hydrogel culture. Previously, scientists have had to use large doses of the drug to show that it is effective in tissue culture.

Moving forward, the researchers plan to mimic granulomas—clusters of infected white blood cells—in their study to explore why some people have latent TB while others show aggressive symptoms. Gupta says that the team is also interested in understanding the mechanism of action of pyrazinamide, which may help discover new drugs that are more or just as efficient.

New 3D Model Speeds Up TB Drug Testing

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Researchers from the Department of Bioengineering (BE), Indian Institute of Science (IISc), have designed a novel 3D hydrogel culture system that mimics the mammalian lung environment. It provides a powerful platform to track and study how tuberculosis bacteria infect lung cells and test the efficacy of therapeutics used to treat TB.

Mycobacterium tuberculosis (Mtb) is a dangerous pathogen. In 2022, it affected 10.6 million people and caused 1.3 million deaths, according to the WHO. "It is a very old bug, and it has evolved with us quite a bit," says Rachit Agarwal, Associate Professor at BE and corresponding author of the study published in Advanced Healthcare Materials. Mtb primarily infects the lungs.

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Current culture models used to study Mtb infection have several limitations. They are typically culture plates that are monolayered and do not accurately mimic the 3D microenvironment inside the lungs. The microenvironment experienced by the cells in such 2D culture is vastly different from the actual extracellular matrix (ECM) surrounding lung tissue. "In a tissue culture plate, there are no ECM molecules, and even if a very thin layer of ECM is coated on these plates, the lung cells 'see' the ECM on one side at best," explains Vishal Gupta, PhD student at BE and first author.

The 2D culture plates are also extremely hard compared to the soft lung tissues. "You are looking at a rock versus a pillow," explains Agarwal.

He and his team have now designed a novel 3D hydrogel culture made of collagen, a key molecule present in the ECM of lung cells. Collagen is soluble in water at a slightly acidic pH. As the pH is increased, the collagen forms fibrils which cross-link to form a gel-like 3D structure. At the time of gelling, the researchers added human macrophages – immune cells involved in fighting infection – along with Mtb. This entrapped both the macrophages and the bacteria in the collagen and allowed the researchers to track how the bacteria infect the macrophages.

The team tracked how the infection progressed over 2-3 weeks. What was surprising was that the mammalian cells stayed viable for three weeks in the hydrogel – current cultures are only able to sustain them for 4-7 days. "This makes it more attractive because Mtb is a very slow-growing pathogen inside the body," says Agarwal.

Next, the researchers carried out RNA sequencing of the lung cells that grew in the hydrogel, and found that they were more similar to actual human samples, compared to those in traditional culture systems.

The team also tested the effect of pyrazinamide – one of the four most common drugs given to TB patients. They found that even a small amount (10 µg/ml) of the drug was quite effective in clearing out Mtb in the hydrogel culture. Previously, scientists have had to use large doses of the drug – much higher compared to concentrations achieved in patients – to show that it is effective in tissue culture.

"Nobody has shown that this drug works in clinically relevant doses in any culture systems … Our setup reinforces the fact that the 3D hydrogel mimics the infection better," explains Agarwal.

Agarwal adds that they have already filed an Indian patent for their 3D culture, which can be scaled up by industries and used for drug testing and discovery. "The idea was to keep it quite simple so that other researchers can replicate this," he adds.

Moving forward, the researchers plan to mimic granulomas – clusters of infected white blood cells – in their 3D hydrogel culture to explore why some people have latent TB, while others show aggressive symptoms. Gupta says that the team is also interested in understanding the mechanism of action of pyrazinamide, which may help discover new drugs that are more or just as efficient.

Reference: Gupta VK, Vaishnavi VV, Arrieta‐Ortiz ML, et al. 3D hydrogel culture system recapitulates key tuberculosis phenotypes and demonstrates pyrazinamide efficacy. Adv Healthcare Materials. 2024:2304299. Doi: 10.1002/adhm.202304299

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