By Deborah Borfitz
May 19, 2021 | When patients are battling any kind of infection, the focus is invariably more on the bug in their system than their immune response to its presence. Yet overactivation of the body’s infection-fighting processes is what leads to conditions like sepsis—a leading cause of death in hospitals.
That clinical reality is what prompted development of a novel assay able to quickly assess the immune response of patients in the emergency department (ED) so doctors can intervene and prevent full-blown systemic inflammation, according to Professor Jongyoon Han, professor of biological engineering and electrical engineering at Massachusetts Institute of Technology (MIT). He is also principal investigator with the Critical Analytics for Manufacturing Personalized-Medicine (CAMP) group at the Singapore-MIT Alliance for Research and Technology (SMART), MIT’s research enterprise in Singapore, which specializes in practical approaches to immune profiling of individuals to predict their response to treatment.
“We have a relatively poor understanding of how an infection would lead to full-blown systemic inflammation,” says Han, and most of the tests available to frontline healthcare providers to characterize immune response—cytokine profiling or measuring leukocyte gene expression or cell-surface biochemical markers—are time- and labor-intensive. Even for a simple complete blood count, the wait for results can be up to 12 hours. By the time lab reports arrive, findings may no longer be needed or even valid.
As recently described in Small (DOI: 10.1002/smll.202006123), one potential alternative may be a label-free assay that uses unconventional L and inverse-L shaped pillars of deterministic lateral displacement (DLD) microfluidic technology to quantify and profile immune states of white blood cells. In a preliminary clinical study involving 85 donors in the ED in a range of immune response states, the device accurately assessed the biophysical properties of size, deformation, distribution, and cell count.
Notably, the test requires only a drop of blood and produces results in 15 minutes. If proven out in clinical trials, the assay could become as routine as glucose testing in the ED, says Kerwin Kwek, senior postdoctoral associate at SMART CAMP and lead author of the paper.
Theoretically, the test would be applicable to any bacteria-induced infection or even non-infectious systemic inflammation, says Han. Preventing the onset of sepsis is the big clinical concern, and it can result from any kind of infection whether bacterial or viral.
This is the first precision diagnostic method enabling simultaneous sorting and immune response profiling in whole blood based on the four biophysical parameters of size, deformation, distribution, and cell count, says Kwek. The research team translated the DLD sorting method into an assay to quantify and profile the immune states of white blood cells reflecting severity of immune response.
Speed to results is one of the more interesting aspects of the work, says Han. The other is that a strong correlation between immune response and biophysical markers was witnessed in the ED population, which is much more diverse than patients in, say, the intensive care unit (ICU).
Interest in the immune profiling method emerged from the realization that the current approach of identifying and treating a pathogen was far from ideal in terms of predicting how patients will fare, Han says. When used for early diagnosis of infection to detect low-abundance pathogens, the prevailing tests often do not accurately reflect the severity of infection.
“The clinical reality we hear from the ICU is that sometimes patients would have a blood infection and be out of the hospital in two days because their immune system took care of the pathogen in the blood, and in other cases no pathogen would be detected but then two days later they would be seriously sick with their immune system going on the attack and damaging their organs,” says Han. “Once they got into that sepsis-like state, it did not really matter what the original trigger was.”
Current biomarkers are either too upstream, before levels are detectable in the blood, or too downstream, once they can be measured but organ damage had already begun, he says. Changes in immune cell activity seem to be a more relevant modality—particularly that of neutrophils which are the first to arrive on the scene when infection strikes.
But the body’s immune response can often be volatile and may change within a few hours, making it challenging to monitor with conventional assays, say Kwek. An added complexity is that patients may have preexisting conditions such as high blood pressure or diabetes.
The DLD microfluidic technology tackles this issue by quantifying immune cell biophysical signatures in relation to the real-time activation levels of white blood cells, Kwek says. Specifically, the test measures both the extent and direction of these changes as a reflection of a patient's current immune response state.
The biophysical signatures are based on 38 biophysical markers. A support vector machine learning algorithm was used to calculate diagnostic probability values between biophysical properties of white blood cells and host infection, Kwek explains.
Importantly, the technology uses video frame rates of up to 150 fps, meaning it could potentially be developed into a portable unit for point-of-care, blood-sparing assays in the ED and other primary care settings, he adds. The biophysical diagnostic modality could be deployed using low-cost and compact machine vision cameras or smartphone optical sensors.
The speed of patient stratification demonstrated in the study holds promise for acute infection triage, risk management, and resource allocation in the ED, Kwek says. But the immune response device could well have utility in other departments, including the ICU, where clinical manifestation of infection severity may be compounded with comorbidities.
Clinical partners of SMART CAMP may also be interested in investigating if the identified biophysical immune signatures correlate with the condition of patients with other types of diseases such as cancer and the treatment of cancers using CAR T immunotherapy, he adds.
Further out, the assay might also prove useful for outpatient-based immune response profiling, says Kwek, particularly in populations less likely to be trekking to the hospital with any regularity. Most sepsis cases originate in rural areas due to access-to-care barriers.