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zika virus

Neuroimaging essential for Zika cases

zika virus

About three years ago, Zika virus emerged as a newly recognized congenital infection, and a growing body of research indicates the damage it causes differs from other infections that occur in utero.

Seventy-one of 110 Brazilian infants at the highest risk for experiencing problems due to exposure to the Zika virus in the womb experienced a wide spectrum of brain abnormalities, including calcifications and malformations in cortical development, according to a study published July 31, 2019 in JAMA Network Open.

The infants were born at the height of Brazil’s Zika epidemic, a few months after the nation declared a national public health emergency. Already, many of the infants had been classified as having the severe form of congenital Zika syndrome, and many had microcephaly, fetal brain disruption sequence, arthrogryposis and abnormal neurologic exams at birth.

These 110 infants “represented a group of ZIKV-exposed infants who would be expected to have a high burden of neuroimaging abnormalities, which is a difference from other reported cohorts,” Sarah B. Mulkey, M.D., Ph.D., writes in an invited commentary published in JAMA Network Open that accompanies the Rio de Janeiro study. “Fortunately, many ZIKV-exposed infants do not have abnormal brain findings or a clinical phenotype associated with congenital Zika syndrome,” adds Dr. Mulkey, a fetal–neonatal neurologist in the Division of Fetal and Transitional Medicine at Children’s National in Washington, D.C.

Indeed, a retrospective cohort of 82 women exposed to Zika during their pregnancies led by a research team at Children’s National found only three pregnancies were complicated by severe fetal brain abnormalities. Compared with the 65% abnormal computed tomography (CT) or magnetic resonance imaging (MRI) findings in the new Brazilian study, about 1 in 10 (10%) of babies born to women living in the continental U.S. with confirmed Zika infections during pregnancy had Zika-associated birth defects, according to the Centers for Disease Control and Prevention.

“There appears to be a spectrum of brain imaging abnormalities in ZIKV-exposed infants, including mild, nonspecific changes seen at cranial US [ultrasound], such as lenticulostriate vasculopathy and germinolytic cysts, to more significant brain abnormalities, such as subcortical calcifications, ventriculomegaly and, in its most severe form, thin cortical mantle and fetal brain disruption sequence,” Dr. Mulkey writes.

About three years ago, Zika virus emerged as a newly recognized congenital infection, and a growing body of research indicates the damage it causes differs from other infections that occur in utero. Unlike congenital cytomegalovirus infection, cerebral calcifications associated with Zika are typically subcortical, Dr. Mulkey indicates. What’s more, fetal brain disruption sequence seen in Zika-exposed infants is unusual for other infections that can cause microcephaly.

“Centered on the findings of Pool, et al, and others, early neuroimaging remains one of the most valuable investigations of the Zika-exposed infant,” Dr. Mulkey writes, including infants who are not diagnosed with congenital Zika syndrome.  She recommends:

  • Cranial ultrasound as the first-line imaging option for infants, if available, combined with neurologic and ophthalmologic exams, and brainstem auditory evoked potentials
  • Zika-exposed infants with normal cranial ultrasounds do not need additional imaging unless they experience a developmental disturbance
  • Zika-exposed infants with abnormal cranial ultrasounds should undergo further neuroimaging with low-dose cranial CT or brain MRI.
Kirsten-M.-Williams

Helpful, hopeful news for bone marrow transplant patients

Kirsten-M.-Williams

Research published online Dec. 13, 2017, by The Lancet Haematology and co-led by Kirsten M. Williams, M.D., suggests that a new imaging agent can safely show engraftment as early as days after transplant – giving a helpful and hopeful preview to patients and their doctors.

Leukemia can be a terrifying diagnosis for the more than 60,000 U.S. patients who are told they have this blood cancer every year. But the treatment for this disease can be just as frightening. For patients with certain forms of leukemia, the only chance they have for a cure is to receive a massive dose of radiation and chemotherapy that kills their hematopoietic stem cells (HSCs), the cells responsible for making new blood, and then receive new HSCs from a healthy donor.

While patients are waiting for these new cells to go to the bone marrow factory and begin churning out new blood cells, patients are left without an immune system. Devoid of working HSCs for two to four weeks – or longer, if a first transplant doesn’t take – patients are vulnerable to infections that can be just as deadly as their original cancer diagnosis.

As they wait in the protected confines of a hospital, patients who undergo HSC transplants receive blood tests every day to gauge successful engraftment, searching for the presence of immune cells called neutrophils, explains Kirsten M. Williams, M.D., blood and bone marrow transplant specialist at Children’s National Health System.

“As you head into week three post-transplant and a patient’s cell counts remain at zero, everyone starts to get nervous,” Dr. Williams says. The longer a patient goes without an immune system, the higher the chance that they’ll develop a life-threatening infection. Until recently, Dr. Williams says, there has been no way beyond those daily blood tests to assess whether the newly infused cells have survived and started to grow early healthy cells in the bone marrow, a process called engraftment.

A new study could change that paradigm. Research published online Dec. 13, 2017, by The Lancet Haematology and co-led by Dr. Williams suggests that a new imaging agent can safely show engraftment as early as days after transplant – giving a helpful and hopeful preview to patients and their doctors.

The study evaluated an investigational imaging test called 18F-fluorothymidine (18F-FLT). It’s a radio-labeled analogue of thymidine, a natural component of DNA. Studies have shown that this compound is incorporated into just three white blood cell types, including HSCs. Because it’s radioactive, it can be seen on various types of common clinical imaging exams, such as positron emission tomography (PET) and computed tomography (CT) scans. Thus, after infusion, the newly infused developing immune system and marrow is readily visible.

To see whether this compound can readily and safely visualize transplanted HSCs, Dr. Williams and colleagues tested it on 23 patients with various forms of high-risk leukemia.

After these patients received total-body irradiation to destroy their own HSCs, they received donor HSCs from relatives or strangers. One day before they were infused with these donor cells, and then at five or nine days, 28 days, and one year after transplantation, the patients underwent imaging with the novel PET/and CT scan imaging platform.

Each of these patients had successful engraftment, reflected in blood tests two to four weeks after their HSC transplants. However, the results of the imaging exams revealed a far more complicated and robust story.

With 18F-FLT clearly visible in the scans, the researchers saw that the cells took a complex journey as they engrafted. First, they migrated to the patients’ livers and spleens. Next, they went to the thoracic spine, the axial spine, the sternum, and the arms and legs. By one year, most of the new HSCs were concentrated in the bones that make up the trunk of the body, including the hip, where most biopsies to assess marrow function take place.

Interestingly, notes Dr. Williams, this pathway is the same one that HSCs take in the fetus when they first form. Although experimental model research had previously suggested that transplanted HSCs travel the same route, little was known about whether HSCs in human patients followed suit.

The study also demonstrated that the radiation in 18F-FLT did not adversely affect engraftment. Additionally, images could identify success of their engraftments potentially weeks faster than they would have through traditional blood tests – a definite advantage to this technique.

“Through the images we took, these patients could see the new cells growing in their bodies,” Dr. Williams says. “They loved that.”

Besides providing an early heads up about engraftment status, she adds, this technique also could help patients avoid painful bone marrow biopsies to make sure donor cells have taken residence in the bones or at the very least help target those biopsies. It also could be helpful for taking stock of HSCs in other conditions, such as aplastic anemia, in which the body’s own HSCs fade away. And importantly, if the new healthy cells don’t grow, this test could signal this failure to doctors, enabling rapid mobilization of new cells to avert life-threatening infections and help us save lives after transplants at high risk of graft failure.

“What happens with HSCs always has been a mystery,” Dr. Williams says. “Now we can start to open that black box.”

Dr. Williams’ co-authors include co-lead author Jennifer Holter-Chakrabarty, M.D., Quyen Duong, M.S., Sara K. Vesely, Ph.D., Chuong T. Nguyen, Ph.D., Joseph P. Havlicek, Ph.D., George Selby, M.D., Shibo Li, M.D., and Teresa Scordino, M.D., University of Oklahoma; Liza Lindenberg, M.D., Karen Kurdziel, M.D., Frank I. Lin, M.D., Daniele N. Avila, N.P., Christopher G. Kanakry, M.D., Stephen Adler, Ph.D., Peter Choyke, M.D., and senior author Ronald E. Gress, M.D., National Cancer Institute; Juan Gea-Banacloche, M.D., Mayo Clinic Arizona; and Catherine “Cath” M. Bollard, M.D., MB.Ch.B., Children’s National.

Research reported in this story was supported by the National Institutes of Health, Ben’s Run/Ben’s Gift, Albert and Elizabeth Tucker Foundation, Mex Frates Leukemia Fund, Jones Family fund and Oklahoma Center for Adult Stem Cell Research.