A vaccine given to bone marrow donors could protect transplant recipients from life-threatening pneumonia, according to City of Hope Cancer Center researchers. Findings from the study were presented at the American Society of Hematology’s 47th annual meeting in Atlanta in December.
Cytomegalovirus (CMV) can cause life-threatening pneumonia in individuals with severely weakened immune systems, such as stem cell transplant (HCT) patients. City of Hope scientists, led by Don J. Diamond, Ph.D., director, Laboratory of Vaccine Research, are addressing this threat with a pretransplant vaccine intended not for the patient, but rather for the donor.
“Our hope is that by giving the HCT patients’ incoming, new immune system a booster shot before the transplant, they will be better protected,” said Diamond. CMV is present in approximately 50 percent of people but normally does not present a problem for healthy immune systems. HCT patients, however, are severely immunocompromised and vulnerable to infection.
According to Diamond, during the first 40 days following transplant, HCT patients are at high risk of CMV-related pneumonia, because the new immune system is still taking hold. This also makes vaccinating the patient after transplant a poor option.
Antiviral therapies may be administered, but despite advances in formulation and delivery, they can cause complications and extend post-transplant recovery, as well.
To address these challenges, Diamond’s group developed a vaccine to give to bone marrow donors prior to transplant. The vaccine elevates donors’ immune system readiness.
“Because CMV is prevalent, most people’s immune systems are used to it and there is no need to be very aggressive to keep it at bay,” said Diamond. “Unfortunately, this also means the immune system won’t respond to it very vigorously in its new home after transplant.”
The researchers designed the vaccine using an altered form of poxvirus that can coax the body into making large amounts of certain CMV proteins. This activates the donor’s immune system prior to transplant, increasing its readiness. Laboratory results indicate this elevated immunity is maintained following transplant, protecting the patient. Researchers hope to confirm this in clinical trials next year.
Other City of Hope researchers on the study include Zhongde Wang, assistant research scientist, Department of Virology; Corinna la Rosa, assistant research scientist, Department of Virology; Simon F. Lacey; John A. Zaia, M.D., chair, Division of Virology, and Stephen J. Forman, M.D., chair, Division of Hematology & Hematopoietic Cell Transplantation. Zaia and Forman would lead the clinical trials in healthy volunteers and transplant patients.