Development of multi-parametric measurements of the circulating immune response to Feline Tuberculosis to improve the understanding and diagnosis of t

Tuberculosis (Tb) is a major global concern in humans and animals. In the UK, Tb is an increasing problem in cattle, badger and other domestic and wildlife species, including pet cats. We have shown that cats in the UK are significantly at risk of Tb, as ~1% of all routine feline tissue biopsies have histopathological changes consistent with mycobacteriosis (Gunn-Moore et al. 2013); at least 15% of these are due to M. bovis, and 19% M. microti (the vole/rodent bacillus) (Gunn-Moore et al. 2011). Some M. bovis infections in cats progress extremely rapidly, with large numbers of organisms present within the affected tissues and exudates; this poses a major concern given the recently recognised cat to human zoonotic risk (Roberts et al. 2014). We hypothesise that the outcome of exposure of domestic cats to M. bovis or M. microti, and the likelihood of zoonotic transmission, is determined by the nature of the pathogen and the host's immune response.
Rapid, accurate, diagnosis is the key to determining zoonotic risk and management options. Currently, Tb in cats is confirmed by culture, IFN-gamma (IFN gamma) release assay (IGRA) or PCR tests. However, there are major limitations with all three methodologies: infected samples fail to culture in up to 50% of cases (despite having ZN+ mycobacteria present); the IGRA cannot always differentiate M. bovis from M. microti; and PCR tests, where available, are very costly.
This study aims to improve diagnostic tests for feline Tb that will impact significantly on determining the zoonotic and inter- and intra-species risk of M. bovis and M. microti infections in cats. It will also inform management options, predict survival (likelihood of clearance or latency), and so impact on the long term health of infected cats, their owners, and in-contact domestic and wildlife species. An important output will be a greater understanding of the immune response of domestic cats to infection with M. bovis or M. microti.
The project builds upon ongoing studies of the immune response of cats infected with Tb. We have in place a significant bank of samples of serum, plasma and formalin fixed paraffin-embedded tissues (>300) from Tb cats and we will continue to expand this collection. Using these samples we have recently defined the cytokine profile of cats infected with M. bovis or M. microti and shown significant differences between infected and healthy cats, and between M. bovis and M. microti infection. In parallel studies we have also shown significant differences in macrophage responses and granulomatous inflammation in infected cats which are important determinants in the outcome of infectious exposure (MS in preparation). With our industrial partner Biobest we are continuing to evaluate the sensitivity and specificity of the IGRA test.
This new PhD project will expand these studies with four major objectives:
1) Continue to collect samples from tuberculous cats and healthy controls to expand our biobank and provide additional samples for analysis within this project.
2) Measure serum/plasma cytokines using a multiplex cytokine assay to determine whether measurement of additional cytokines (alongside IFN gamma) can improve diagnostic sensitivity and specificity. This will also inform on the immune response to infection with M. bovis and M. microti.
3) Develop, in collaboration with industrial partners, a multiplex antibody detection system that will elucidate the role of the host's humoral immune response to infection.
4) Correlate the outcome of (2) and (3) with clinical histories, outcomes and responses to treatment to identify signature profiles that can predict the degree of pathogenicity, the risk of transmission, and the likely response to treatment (where appropriate).
The project will enable the student to gain expertise in a wide range of skills and will involve extensive collaboration with Biobest who will be the industrial partner for this work.