'Developing new vaccine against TB a daunting task'

Tuberculosis Representational image | AP

Our buses and trains are overcrowded not just in peak hours but almost all the time, making you wonder where all these people are heading to. But so are our malls. And our slums.

Indians seem to be immune to crowdedness, psychologically. Does it take a toll on our health? Our crowded living conditions make it extremely hard to control infectious diseases like tuberculosis (TB), says Dr. Jyothi Rengarajan, an India-born researcher at the Emory University School of Medicine in Atlanta.

Currently, the only licensed vaccine for TB is BCG. It has been almost a century since we have had a new vaccine for TB. In an interview with THE WEEK, Rengarajan, associate professor at the Division of Infectious Diseases and Emory Vaccine Center, explains why developing a vaccine against TB is such a daunting task.

How close are we to a new TB vaccine?

I wouldn't say we are close. But I think we have a lot of tools at our disposal, with which we can make some big strides.

We are trying to understand what's protective against TB. We study both animal models and humans to better understand the factors that go into making a good vaccine.

Some of the basic questions that can be easily answered for other diseases remain obscure in TB. It is a difficult disease. One can have TB multiple times. There's no natural immunity against it. So it's harder to understand how to make a protective immune response against the disease.

We try to figure out the immunological basis for latent TB. People having latent TB control the infection but the organism doesn't get eliminated from their body. It can reactivate if person becomes immuno-compromised. We hope understanding latent TB would give us better insights into what kind of vaccine we need.

We don't know what's a good response to TB. By studying how TB stimulates, subverts or evades the immune system, we are trying to develop strategies to counteract that.

Since BCG, there is only one vaccine that went into trial. That was not successful.

Apparently, MTB, the pathogen that causes TB, is a tough bacterium. So you have to come up with a vaccine that's really smart.

It's like HIV. People have been working on a AIDS vaccine for a long time. The reason why we don't have one is we don't know the properties of an ideal vaccine. TB is more complicated. It's a bacteria. It has a lot of genes and proteins evolved since humans existed. It's an ancient disease. It has been around for a long time. So to eliminate TB is going to be very challenging.

How far has the US succeeded in tackling the TB threat?

We certainly have more TB in the US than people think. In fact, it's quite prevalent. Because of the way the world is, people travel a lot these days. Diseases travel too. Also, drug addiction and HIV make a 'developing country-like' situation within a developed country.

HIV affects a very important part of immune cells called T cells, which are critical for controlling TB. When the T cells go down, the risk of TB goes up.

In the 18th century, there was more TB in Europe than in the developing countries. Now things have changed.

There isn't much TB in the developed world, as there used to be. With increased public health measures, it went away. But it can certainly come back in a bigger way.

There's much more TB in developing countries because of malnutrition and crowded living conditions.