World-first live hookworm vaccine for humans could be first step to eradication

A Queensland scientist has developed the first ever live vaccine against hookworm, a parasitic disease that causes anaemia in children and pregnant women in many developing countries.

Fifteen Queenslanders are taking part in the world-first human trial of the live hookworm vaccine, which is underway in Q-Pharm Pty Ltd at QIMR Berghofer Medical Research Institute.

Researcher and infectious disease clinician Dr Paul Chapman said the vaccine consisted of microscopic hookworm larvae exposed to UV light, which would trigger the immune system to respond.

Dr Chapman said he would then test whether the immune response protected against further hookworm infections by giving participants a dose of hookworm larvae that had not been exposed to UV light.

He said the trial participants would then be monitored for a further 10 weeks.

“Humans don’t produce a meaningful immune response to hookworms,” Dr Chapman said.

“We’re optimistic that by exposing hookworm larvae to UV light they will be impaired, which will make it possible for the human immune system to recognise the infection and develop a lasting immune response.”

Dr Chapman said it took around 20 days for a hookworm to penetrate the skin, enter the bloodstream and travel through the lungs to the small intestine.

He said adult hookworms grew to about one centimetre in length, with hookworm eggs being expelled from the body in the faeces. He said larvae hatched from the eggs in warm soil and could remain infectious within the soil for up to six weeks.

Dr Chapman said the clinical trial would compare the response of people who received the vaccine with people who received a placebo vaccine, made using tabasco sauce.

“Tabasco sauce held against the skin for an hour produces a similar prickling sensation as the hookworm larvae penetrating the skin,” he said.

“This means that our participants don’t know whether they are getting the vaccine or the placebo, which is important when you are doing a study like this.

“Ultimately, we will know if the vaccine is successful if we see fewer hookworm eggs in the faeces of participants who are vaccinated.”

Dr Chapman, who is part of Professor James McCarthy’s Clinical Tropical Medicine laboratory, said the next step would be to do a larger study in a developing country where hookworm was endemic, such as the Pacific Islands.

He said hookworm was a global problem, which occurred in tropical environments where poverty and poor sanitation co-existed, and was commonly treated with mass drug campaigns.

He said that was problematic because most communities simply became reinfected, and because it risked other significant problems like drug resistance.

“There are around 400 million people across the world who are infected with hookworm and it significantly reduces quality of life,” he said.

“The sickness caused by hookworm infection mainly affects pregnant and lactating women, and school-aged children, who are at risk of low iron stores or more likely to be seriously affected by iron loss.

“Developing a vaccine that makes people immune to hookworm infection would potentially improve child mortality, developmental outcomes and maternal health in many parts of the world.

“It’s estimated more than US$1 billion is lost every year due to the impact of hookworm infection on global development.

“Developing a model for safely testing hookworm immunity would be a significant step forward in solving this neglected tropical disease.”

Dr Chapman said he was working closely with a James Cook University researcher, Dr Paul Giacomin, who was trialling hookworm infection to treat coeliac disease.

He said the trial could also have implications for Dr Giacomin’s research, and would establish QIMR Berghofer as a safe facility for growing, testing and harvesting hookworm for human trials.

He said developing a model of experimental immunity to human hookworm infection was vital.

“While our primary goal is to create immunity for humans to hookworm infection in poor and malnourished environments, being able to create a model of immunity will help us to further understand exactly how these parasites produce that immune regulation,” Dr Chapman said.