Skip to main content
Premium Trial:

Request an Annual Quote

Oxford Immunotec Cytomegalovirus Assay on IGRA Platform Has Clinical Utility, Studies Say


NEW YORK – Oxford Immunotec recently said it is a step closer to developing new applications for the interferon gamma release assay (IGRA) technology enabling its T-spot.TB tests.

The technology, which identifies T cells secreting interferon gamma using an enzyme-linked immuno-spot assay, is being evaluated "to enable personalized medicine for transplant recipients," the company's CEO and Founder Peter Wrighton-Smith said during a conference call Monday to discuss the firm's financial results.

Two "significant new pieces of evidence" have been published recently, he said, both in the Journal of Infectious Diseases, that describe the clinical value of the technology in measuring the human immune response to cytomegalovirus (CMV) infections associated with transplants.

In one of the studies ─ a prospective, multicenter clinical trial ─ investigators in Spain reported that monitoring CMV-specific cell-mediated immunity "may guide decision-making regarding the type of CMV preventive strategy in kidney transplantation," and in the second study, researchers associated with several health centers in the US and Europe said measurement of CMV cell-mediated immunity using Oxford Immunotec's Elispot assay "would be useful clinically."

The T-Spot technology platform measures the responses of T cells ─ central components of the human body’s immune system ─ to inform the diagnosis, prognosis, and monitoring of patients with immunologically controlled diseases, according to Oxford Immunotec.

T cells are implicated in the control and progression of many medical conditions, including certain types of infectious diseases, cancers, and autoimmune diseases. The company’s initial product to use the technology platform is its commercially available T-Spot.TB assay used to test for latent tuberculosis infection.

"The big picture implication of the recent publications is that it's a first step toward diversifying the company into having a number of assays based on the same technology platform," Wrighton-Smith said in an interview.

Transplant recipients are at risk of infection because they are given drugs to suppress the immune system and prevent rejection of transplanted stem cells or solid organs.

"Infections are a significant cause of mortality and morbidity among transplant recipients and chief amongst them is CMV," Wrighton-Smith said.

He noted that Oxford Immunotech's CMV assay may have a future role in clinical settings to ascertain the presence and risk of CMV infections in transplant donors and recipients. Further, the test may be used to help physicians decide whether to administer antiviral therapies and for how long.

The investigators in the Spain study identified which kidney transplant patients needed therapy to prevent CMV infection, Wrighton-Smith said, adding, "They did that safely and effectively, enabling the implementation of precision medicine, something that's not currently being done in this context."

Serologic ELISA tests that detect CMV IgM and IgG antibodies are available from commercial laboratories as are PCR tests that determine CMV viral load. Measuring viral load can confirm the presence of an infection, but it is not a predictor of the body's immune response and therefore not predictive of infection, Wrighton-Smith said.

Oriol Bestard, an author of the kidney transplant CMV infection study and head of the kidney transplant unit at Bellvitge University Hospital, Barcelona, said he and his colleagues had not been using tests to predict infections but instead had prescribed an antiviral therapy to prevent infections.

They are now in discussions with administrators within their health system with a view to using the Oxford Immunotec test on an ongoing basis for transplant procedures. Important aspects of implementing the test routinely, such as whether and how much it will be reimbursed, still need to be worked out, he said. 

"Nonetheless, we understand that this is something we need in terms of changing the way we manage our patients," Bestard said. "The prospective, randomized trail demonstrated that the test can be used in such a way that patients can avoid developing infections and avoid unnecessary treatments."

Overall, the most important outcome of the trial is that "we can change the way we manage our patients in the context of preventing infections," he said.

Bestard added that clinicians in his hospital, like clinicians elsewhere doing kidney transplants, have been prescribing the antiviral drug Valganciclovir (Genentech's Valcyte) for all their transplant patients as part of a prophylactic approach because they could not evaluate the risk of infection.

"Now, we can give the antiviral therapy only to those who present with high risk according to the test," he added. "We know that we need to implement this in clinical practice."

In the multicenter clinical trial, investigators assessed the value of monitoring pretransplant CMV-specific cell-mediated immunity (CMI) using the interferon-gamma release assay to predict CMV infection in kidney transplantation.

In all, 160 donor and recipient CMV-seropositive patients, stratified by their baseline CMV–specific CMI risk, were randomized to receive monitoring of viral replication in peripheral blood or antiviral prophylaxis over three months. In the study, patients, deemed to be at high risk for CMV based on pretransplant CMI measurement using the CMV assay, developed CMV infection at higher rates than those deemed to be at low risk, the researchers said. They discovered that the optimal time to apply the assay to predict infection was between 10 and 15 days after the transplant procedure, Bestard added.

In the prospective multicenter study initiated to investigate CMV associated with stem-cell transplantation, the investigators evaluated CMV-CMI every two weeks from the pretransplant period until six months post transplantation in 241 allogeneic hematopoietic cell transplant recipients with positive CMV serostatus. The investigators reported that Oxford Immunotec's test could be used to monitor stem cell transplant recipients and distinguish between patients at risk of developing clinically significant CMV infection who require antiviral prophylaxis or therapy and those who are protected from the infection.

Wrighton-Smith said on the conference call that the CMV test should not be viewed as a revenue driver "for the time being, at least." The firm views the CMV assay as part of a longer-term play to diversify its product portfolio over time.

"We will require regulatory approval in the US and need to establish [a case for] value-based reimbursement," he said. "So, we're in the process of evaluating the market opportunity, building out the business case, and getting some more market feedback before we will apply significant resources to it."

Wrighton-Smith told 360Dx that the Abington, UK-based company is "evaluating which FDA pathway would apply to the CMV assay and what is needed to pursue that pathway."

In the meantime, the firm has a near-term focus on pushing greater adoption for its latent TB tests. Its biggest competitor, Qiagen is in the midst of being acquired by Thermo Fisher Scientific.

Oxford Immunotec sold its US laboratory services business to Quest in November 2018, and the firms entered a strategic agreement that is showing encouraging signs, Wrighton-Smith said this week. T-spot.TB is now available in about 1,400 patient service centers, a segment of the market that Oxford Immunotec had not previously penetrated.