Imagine a day when a urine test could inform a health care provider precisely why a kidney transplant patient was experiencing organ rejection and suggest one of the best medication for specifically addressing the issue.

That day took a leap closer to reality because of a remarkable set of single-cell analyses which have identified probably the most specific cellular signatures so far for kidney transplant rejection. The findings were detailed May 25, 2023, in JCI The Journal of Clinical Investigation.

The study results reflect eight years of teamwork led by experts at Cincinnati Kid’s and the University of Cincinnati College of Medicine with contributions from researchers on the University of Notre Dame and Novartis.

Tiffany Shi, an MD/PhD student with the Immunology Graduate Program and Medical Scientist Training Program at Cincinnati Kid’s was first writer. Senior co-authors were David Hildeman, PhD, interim director of the Division of Immunobiology at Cincinnati Kid’s, and E. Steve Woodle, MD, professor of surgery and William A. Altemeier Chair in Research Surgery on the UC College of Medicine. Hildeman and Woodle co-direct the Center for Transplant Immunology at Cincinnati Kid’s.

“The available treatments for stopping a rejection event haven’t modified much in many years. These cellular signatures open the door to establishing a whole recent set of anti-rejection therapies,” Hildeman says.

Having a precision-medicine approach to treating organ rejection has the potential to markedly reduce the threat rejection poses to transplanted organs. More follow-up research will likely be needed, but these findings have implications that stretch beyond kidney transplantation to potentially apply to liver, lung transplantation and more.”

E. Steve Woodle, MD, Professor of Surgery and William A. Altemeier Chair in Research Surgery on the UC College of Medicine

Organ rejection affects 10% of recipients

Kidney transplantation is probably the most common type of organ transplant; provided after organ failure from diabetes, infections, injuries, and other aspects. In 2022, surgeons performed 25,498 kidney transplants across the US, in keeping with the United Network for Organ Sharing (UNOS).

Over the past 30 years, gradual improvements have allowed kidney transplants to last more in order that now the “half-life” for living-donor kidneys exceeds 20 years and approaches 12 years for deceased-donor organs.

“For an older person, these survival rates reflect a fairly very long time,” Hildeman says. “But for younger adults and kids, the possibilities of needing a second transplant remain high.”

Nevertheless, once a kidney transplant recipient experiences acute rejection, many go on to lose their transplant and return to dialysis inside 1-3 years. As well as, once a patient’s immune system rejects one organ, it’s way more prone to reject a second transplant.

Unfortunately, the tools available to effectively treat rejection–corticosteroids and antilymphocyte globulins–have remained largely unchanged for over 60 years. Evidence collected over a few years has indicated that these treatments inadequately or incompletely treat rejection.

Discovering clues one cell at a time

In the brand new study, researchers used powerful single-cell genomic evaluation technologies to painstakingly compare biopsy samples from transplanted kidneys that encountered acute cellular rejection. The studies also compared rejections occurring under the commonly used maintenance immunosuppressive agent (tacrolimus) and two newer alternative medications (belatacept and iscalimab).

The evaluation was so detailed that the team was capable of track how gene expression modified inside specific populations of cells that drive rejection damage, which the authors termed allospecific CD8 expanded T cell clones (CD8EXP).

The researchers say this study is the primary to use a mixture of single-cell RNA evaluation with single-cell T cell receptor (TCR) evaluation to explore acute kidney transplantation rejection.

“The ability of what we’re doing comes from having the ability to have a look at cells on a single-cell level. We will look specifically at those which are answerable for rejection and we are able to have a look at how rejection changes over time because the T cells are shifting their response to different drugs,” Shi says.

Woodle describes CD8EXP cells because the “tip of the spear” in rejection.

The work revealed three key findings:

First, even when an acute rejection event was stopped, the research revealed that treatments often will not be thorough enough to eliminate all of the T cells that had cloned themselves to attack the transplant. In some cases, hostile T cells endured for months after anti-rejection treatment.

This means that multiple rejection events, previously believed to be entirely separate, may very well be one, longer, smoldering rejection event. Addressing lurking cloned T cells that eluded initial treatment will likely require improved testing techniques and adopting more consistent practice standards.

Second, the team found roughly 20 “clonotypes” of CD8EXP T cells–from a possible of thousands–that reproduced themselves to mount attacks against a transplanted organ. The categories differed in keeping with the receptors the T cells carried. The relatively low variety of clonotypes excited the researchers because it should make it easier to go looking for potential recent treatments to stop transplant rejection.

By studying these rare, but efficient cells, the team found distinct cellular signatures occurring during a rejection event that varied depending upon which maintenance immune-suppression drug was used. The various genes involved raise the potential of using other medications not typically related to treating organ rejection as recent weapons for specific situations.

For instance, this team also recently reported success at using an mTOR inhibitor called everolimus to assist patients that didn’t profit from belatacept treatment But that very same drug appears to supply no similar profit when tacrolimus treatment is involved. This work led to a currently ongoing clinical trial led by Woodle to treat patients with belatacept and everolimus for maintenance immunosuppression.

Third, the identical T cell types causing rejection events also will be detected in urine samples.

Why a urine test matters

Currently, obtaining the crucial details underlying rejection of a transplanted kidney requires collecting a tissue biopsy, a surgical operation that requires visiting a hospital. Conducting multiple biopsies over time to trace treatment outcomes is dear and potentially dangerous for patients.

Nevertheless, urine tests might be collected more continuously in a non-invasive manner and potentially without the inconvenience of visiting a hospital. Along with directly supporting patient care, a viable urine test would help speed up the research work required to guage recent anti-rejection treatment protocols. The research also demonstrated that CD8EXP T cells that were present in the rejecting organ were also present within the urine.

“This finding indicates that a straightforward urine test could substitute for a more invasive kidney transplant biopsy and thereby make it much safer and easier for patients to have their rejection treatment monitored for effectiveness,” Hildeman says.

The critical challenge for achieving a practical clinical urine test will likely be to ascertain a process that may produce test ends in 48 hours somewhat than the research-focused process utilized in this study, which took several months to finish.

Award-winning presentation

As first writer, Shi presented the outcomes from this study at ATC2023, the annual scientific meeting of the American Transplant Congress, held June 3-7 in San Diego. Shi’s presentation received the “People’s Selection Award,” which implies it was chosen by the 5,000-plus attendees as one of the best plenary presentation of the meeting.

Shi also received a Young Investigator Award and a number of other other Cincinnati Kid’s and UC researchers were honored on the event.

Next steps

Additional research work is required to explore treatment possibilities related to the T cell signatures revealed on this study. Work led by co-authors has already shown that tacrolimus was a excellent treatment for some patients with resistant rejection cases.

Long run, the advantages could reach beyond expanding the “half-life” of donated kidneys.

For instance, finding alternatives to tacrolimus could help individuals with liver transplants and other organ transplants avoid kidney complications from their anti-rejection regimens.

And eventually, recent understanding of the important thing cellular mechanisms involved in transplant rejection may lead to methods to scale back the risks of xenotransplantation (using gene-modified animal organs in humans).

“Most individuals who need an organ transplant never receive one because the availability of donated organs stays so limited,” Woodle says. “Because of insights like these, we may have the opportunity to substantially reduce lack of transplanted organs to rejection, thereby freeing up donated organs for brand spanking new transplant recipients.”

Source:

Cincinnati Kid’s Hospital Medical Center

Journal reference:

Shi, T., et al. (2023) Single cell transcriptomic evaluation of renal allograft rejection reveals insights into intragraft TCR clonality. Journal of Clinical Investigation. doi.org/10.1172/JCI170191.