Becoming an Expert: Investigating vaccines against viral stomach bugs

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Miguel Leon-Rios is a PhD student at the University's Centre for Global Vaccine Research.

Most of us have experienced the unpleasant symptoms of gastroenteritis at some point in our lives, with infections typically triggered by ingesting contaminated food or water. Although gastroenteritis can be caused by non-infectious agents, viruses-associated episodes are one the most recurrent causes and represent a major disease burden across the globe.

My PhD study is focused on two viral tummy bugs: rotavirus and norovirus (aka winter vomiting bug). These two viruses affect people of all ages and can be deadly in young children, older adults and people with compromised immune systems. Norovirus has been recognised as one of the most common causes of foodborne outbreaks of gastroenteritis worldwide, while rotavirus causes hundreds of thousands of deaths each year globally due to diarrhoeal disease. These viruses spread easily in stools and can be transmitted if you share contaminated objects, towels or food with someone who's infected. For this reason, prevention and containment strategies are important against these infections.

While new vaccine candidates against norovirus are currently being studied, two rotavirus vaccines have been widely introduced into routine vaccination programs across the globe. One of these vaccines I am working with is named ‘Rotarix’, which is given orally to babies by applying a few drops to the mouth. Oral vaccination is part of a mucosal vaccine strategy that helps to promote immunological protection directly at the mucosal site of administration (e.g. nasal, oral, ocular, rectal, and vaginal).

Rotavirus vaccine has shown very good signs of protection. In the UK, rotavirus cases have dropped more than 70% since its introduction in 2013. However, previous studies have identified a big difference on vaccine performance in developing countries, where a huge number of gastroenteritis cases are recorded every year. In other words, disease reduction in low-income countries has not been as effective as it should be. Although the basis of this phenomenon is currently not understood, several factors could be associated to poor oral vaccine responses against this tummy bug, such as our nutritional status, genetic, and even our own pre-existing immune defence.

My PhD research aims to identify the mechanism of protection associated to both human rotavirus and norovirus vaccines, by particularly looking at how our body responds to mucosal vaccines, what may be impairing their efficacy and how we can improve their protective response.

To evaluate this I am using a model of oral mucosal immunity, which represents one of the first line of defence that faces the infection and therefore the vaccine itself. This will help me to better understand the immunological mechanism associated with vaccines protection and effectiveness in situ. I hope my PhD research will contribute in the future to improve current/new vaccine strategies to fight against these gastrointestinal viruses.