Reducing infectious diseases

Dr Joanna Kirman and her team at the Malaghan Institute of Medical Research in Wellington investigate infectious diseases. Their goal is to reduce the incidence of infectious diseases in New Zealand through the development and implementation of vaccines and other therapies.

Joanna and her team are currently working on developing and/or implementing vaccines and therapies for three different infectious diseases: tuberculosis (TB), rotavirus and respiratory syncytial virus (RSV).

Tuberculosis

Tuberculosis or TB (short for tubercles bacillus) is a nasty lung disease that is caused by pathogenic bacteria. It has been around for a long time – evidence of it has been found in ancient Egyptian mummies.

TB bacteria in the lung

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TB bacteria in the lung. The bacteria have been stained red so they can be seen.

Photographer : Dr Kylie Quinn

Rights: Malaghan Institute of Medical Research (MIMR)

A vaccine called BCG (Bacillus Calmette-Guérin) was developed about 100 years ago, but unfortunately, it doesn’t work very well anymore. The TB bacteria are difficult to treat because they ‘hide’ inside your cells. A TB bacterium also has a thick waxy coat around it, making it difficult to get drugs in to kill it.

Normally, a vaccine encourages the immune system’s B cells to make antibodies that stop bacteria from reproducing and hold them for macrophage cells to destroy. Because the TB bacteria hide inside cells, the antibodies can’t get to them. Joanna realises that there needs to be a different immune response for this particular bacteria. The T cells need to be activated to destroy these bacteria.

Joanna is currently investigating T cell response in the immune system. Her team needs to work out which T cells are able to protect against TB. Then they can make a vaccine that will cause the immune system to make more of those T cells and allow them to persist long term so that a person can be protected from TB for several years.

Rotavirus

Rotavirus is another nasty infectious disease that is very common in New Zealand and throughout the world. Rotavirus causes the hospitalisation of about 1,000 children in New Zealand every year with symptoms of diarrhoea, severe dehydration, fever and vomiting. Vaccines for rotavirus have been developed in other countries.

As the name suggests, rotavirus is caused by a virus. As you can have different strains or types of the same virus, Joanna’s team is investigating what types of the virus we have in New Zealand. Once they know what the virus strains are, they will know whether the vaccines that have already been developed overseas will be effective in New Zealand.

The first year of the investigation showed that there were different strains of the virus between the North Island and the South Island within the same year. The second year showed a different divide – the top of the North Island and the bottom of the South Island had the same strain while the middle section had a different strain. The scientists were surprised by this and don’t know why there was such a geographical divide.

The good thing is that all these strains, wherever they were in New Zealand, are strains that can be protected against by the vaccines currently available overseas.

Joanna is hoping that, as a result of this work, these vaccines might be included on New Zealand’s vaccination schedule in the coming years.

Respiratory syncytial virus (RSV)

RSV (also known as bronchiolitis) is a nasty inflammatory lung disease that infects small children. It is very common – nearly every child will have encountered the disease by the time they are 2 years old, and between 4–6% of infected children will be hospitalised. There is no vaccine for RSV. Joanna’s team have been working on finding out why there is such a high rate of RSV in New Zealand and why more children are hospitalised here than in similar overseas countries (such as Canada, Australia and the USA).

The research has shown that Māori and Pacific Island children are more likely to be hospitalised than New Zealand European children and that RSV tends to occur more in the winter months.

The study has led the scientists to believe that RSV could be a result of vitamin D deficiency. Lack of sunlight (our main source of vitamin D) in the winter months results in low levels of vitamin D. Darker coloured skin also requires longer periods of sun exposure than light coloured skin to make the same amount of vitamin D. This may explain why Māori and Pacific Island children can be more vitamin D deficient and could be why they are more seriously affected by RSV.

An international team of scientists including Joanna’s group are currently investigating whether children with severe RSV (in hospital) are actually more vitamin D deficient than children who are able to fight off the infection in the community.

If the research finds that RSV is a result of vitamin D deficiency, it will be easy to treat (and prevent). Vitamin D can be given as a supplement or added to infant formula or foods that small children are eating.