A key problem with kidney transplantation is the potential for the patient’s immune system to reject the kidney. Hence all transplant patients are given medications to suppress their immune systems. If their immune system is too suppressed, patients are at risk of severe infection; if it is not suppressed enough, they are at risk of rejecting the kidney. Our current methods for monitoring the degree of immune suppression are crude and episodes of both severe infection and organ rejection are common. There is currently no simple and practical blood test which quantifies how suppressed the immune system is. Such a blood test would allow us to get the doses of immunosuppressive drugs just right in each patient, using an individually tailored approach. 

Torque teno virus (TTV) is a recently discovered virus which does not cause disease but is very commonly found in peoples’ blood. Estimates from various countries overseas are that over 75% of people have TTV in their blood, but estimates range from 30% to 100% depending on the country, patient population and viral subtype. There are no data from Australia.

There is preliminary evidence that the amount of this virus in blood (known as the “viral load”) is an indirect measure of immune function: a high viral load means the immune system is too suppressed and a low viral means the immune system is very active. 

However, there are many remaining questions which would need to be answered before we could use this as a clinical test, including: 1) How commonly is this virus found in the blood of Australians?; 2) Is it practical to get this blood test done in Newcastle and feed the results back to doctors in a timely way?; 3) In kidney transplant patients, does the viral load of TTV over time actually relate to the risk of severe infection and rejection episodes?; 4) and finally, if the answer to 3) is yes; Does adjusting kidney transplant patients’ immunosuppressive medication doses according to TTV viral load decrease the risk of both infection and rejection episodes?

Our current proposed research project aims to lay the groundwork to answer these questions, by focussing on the first two of them. Our has two main objectives:

1) To develop a practical and inexpensive blood test to measure the level of Torque teno virus in the virology laboratory at the Hunter Medical Research Institute. This will be done by designing and validating a real-time quantitative test called a PCR (polymerase chain reaction) targeting the TTV. Our laboratory already has the necessary equipment and expertise to run such a test. 

2) To collect blood from 50 kidney dialysis patients. We have chosen this group, as they are representative of patients who undergo kidney transplant, but they are not currently receiving immunosuppressive medications. We will test these patients’ blood to see if we can detect TTV, and what proportion of patients have TTV detectable in the blood.

Project type 
Project Grant
Year of funding 
2017