SAN DIEGO – Heart transplant recipients who develop circulating antibodies to human tissues in the first year post transplantation are at heightened risk for poor outcomes and may therefore need closer monitoring, suggests a prospective observational study.
One in seven of the patients studied developed circulating antibodies that specifically targeted human leukocyte antigens on donor tissue, and one in three developed nonspecific antibodies, according to results reported at the annual meeting of the International Society for Heart and Lung Transplantation.
Dr. Jignesh Patel
Relative to their counterparts who did not develop any antibodies, patients who developed either type were more likely to experience both antibody-mediated and cellular rejection. In addition, those developing the donor-specific type were more likely to experience cardiac allograft vasculopathy and to die.
"Patients with donor-specific antibodies or nonspecific antibodies may require more intensive monitoring and augmented immunosuppression to improve their long-term outcomes," commented lead investigator Dr. Jignesh Patel, co–medical director of the heart transplant program at the Cedars-Sinai Heart Institute in Los Angeles. "Further studies are needed to determine the optimum therapy for these patients."
He acknowledged that the issue is complicated, because some patients with donor-specific antibodies (DSA) never experienced rejection, yet others with nonspecific antibodies did. These outcomes suggest that the nature of the antibodies is key. As a result, it is tricky to manage patients who develop antibodies but don’t have any symptoms of rejection.
At his institution, Dr. Patel said, clinicians don’t step up the number of biopsies performed to monitor for rejection in heart transplant recipients who develop antibodies unless they become symptomatic. However, they are cautious about long-term management of immunosuppression. "We will think twice about weaning them off prednisone," he noted. "More likely, we are kind of tending to switch them to a proliferation signaling inhibitor earlier when we see donor-specific antibodies."
Dr. Patel and his coinvestigators studied 144 patients who underwent heart transplantation in 2003-2010 and had serial antibody monitoring by solid-phase assays at baseline (the time of transplantation) and at 1, 3, 6, 9, and 12 months, at minimum.
"More recently introduced methods using solid-phase matrices coated with HLA antigens have demonstrated the ability to detect and identify HLA antibodies with high sensitivity and accuracy," he said.
Because the study period preceded the guidelines that recommended antibody monitoring, these patients were being followed more closely than usual out of concern that they were at heightened risk for antibody development, he said.
On average, the patients had seven antibody measurements during their first year post transplantation.
Study results showed that in the first year after transplantation, 14% of patients developed DSA and 32% developed non–donor-specific antibodies (non-DSA), while the rest did not develop any.
The mean age (approximately 53 years) was similar across groups. Relative to those who did not develop any antibodies, patients who developed non-DSA were more likely to be female (54% vs. 22%). Also, ischemic time was shorter for patients who developed DSA (183 minutes) or non-DSA (195 minutes) than for their counterparts who did not develop any antibodies (230 minutes).
The three groups of patients were generally similar with respect to immunosuppressive therapy at baseline, including receipt of calcineurin inhibitors and antiproliferative agents.
But the group developing DSA was significantly less likely than the group not developing antibodies to be weaned off prednisone (7% vs. 46%), and both the DSA and non-DSA groups were more likely than their counterparts with no antibodies to have received induction therapy (45% and 39% vs. 15%).
The 1-year rate of freedom from antibody-mediated rejection was poorer for patients who developed DSA (65%) or non-DSA (76%), compared with their peers who developed no antibodies (94%). The findings were similar with respect to rates of freedom from acute cellular rejection (80% and 87% vs. 99%, respectively).
The temporal patterns did differ somewhat according to type of rejection, according to Dr. Patel.
"With regard to cellular rejection, it appeared that a lot of events in the patients who developed donor-specific antibodies occurred toward the end of the first year, in comparison to the patients who developed antibody-mediated rejection, where most of the events tended to occur early" post transplant, he observed.
Relative to their counterparts who did not develop antibodies, the patients who developed DSA also had significantly poorer 3-year rates of survival (65% vs. 85%) and freedom from cardiac allograft vasculopathy, which was defined as the development of vascular stenosis exceeding 30% (70% vs. 88%).
Dr. Patel reported that he had no conflicts of interest related to the study.