Early detection of soluble CD27, BTLA, and TIM-3 predicts the development of nosocomial infection in pediatric burn patients

Abstract

Thermal injury induces concurrent inflammatory and immune dysfunction, which is associated with adverse clinical outcomes. However, these effects in the pediatric population are less studied and there is no standard method to identify those at risk for developing infections. Our goal was to better understand immune dysfunction and identify soluble protein markers following pediatric thermal injury. Further we wanted to determine which early inflammatory, soluble, or immune function markers are most predictive of the development of nosocomial infections (NI) after burn injury. We performed a prospective observational study at a single American Burn Association-verified Pediatric Burn Center. A total of 94 pediatric burn subjects were enrolled and twenty-three of those subjects developed a NI with a median time to diagnosis of 8 days. Whole blood samples, collected within the first 72 hours after injury, were used to compare various markers of inflammation, immune function, and soluble proteins between those who recovered without developing an infection and those who developed a NI after burn injury. Within the first three days of burn injury, innate and adaptive immune function markers (ex vivo lipopolysaccharide-induced tumor necrosis factor alpha production capacity, and ex vivo phytohemagglutinin-induced interleukin-10 production capacity, respectively) were decreased for those subjects who developed a subsequent NI. Further analysis of soluble protein targets associated with these pathways displayed significant increases in soluble CD27, BTLA, and TIM-3 for those who developed a NI. Our findings indicate that suppression of both the innate and adaptive immune function occurs concurrently within the first 72 hours following pediatric thermal injury. At the same time, subjects who developed NI have increased soluble protein biomarkers. Soluble CD27, BTLA, and TIM-3 were highly predictive of the development of subsequent infectious complications. This study identifies early soluble protein makers that are predictive of infection in pediatric burn subjects. These findings should inform future immunomodulatory therapeutic studies.

Demographics to Define Pediatric Burn Patients at Risk of Adverse Outcomes

“…Measurements of immunoregulatory checkpoint proteins that regulate T cells (soluble BTLA, TIM-3, and CD27) can also indicate adaptive immune dysfunction. Some researchers have observed that soluble BTLA and TIM-3 are elevated in sepsis patients, whereas our own work has shown similar increases in patients who develop infections after burn injury (10,30,31). Soluble CD27 has been shown to inhibit T cell proliferation and has also been elevated in pediatric burn patients who later develop infections (10,32).…”

“…As such, the adaptive immune system, which is typically thought to follow the innate immune system, also plays a crucial role in determining the risk of an individual developing an infection after pediatric burn injury. Previously, our group and others have shown reductions in CD4 + lymphocytes and PHA-stimulated cytokine production (an important measurement of T cell function) within the first 72 h after burn injury (8,10,12,29). Moreover, both CD4 + lymphocytes and PHA-stimulated cytokine production are shown to be further suppressed in pediatric burn patients who develop infections.…”

“…A total of 132 pediatric burn patients were enrolled, of which 103 subjects had a whole blood sample obtained within the first 72 h of injury. This time point was chosen based on previous findings and infections typically occurring after this time frame (8)(9)(10). In this cohort, the median time to infection was 7 days.…”

“…This is primarily a result of the impairment of the skin's barrier function, leaving patients to rely on their immune system to defend against infectious complications. Previous pediatric burn research has shown an increased release of both pro-inflammatory (e.g., IL-1, -6, -8) and anti-inflammatory (e.g., IL-4, -10) cytokines while simultaneously decreasing innate and adaptive immune cells and function (5)(6)(7)(8)(9)(10)(11). Moreover, studies have shown these immune and cytokine profiles are augmented in patients who develop infections (6)(7)(8)(9).…”

“…Therefore, using objective measurements of immune function, we sought to better identify these cutoff points of patient-defined factors of burn severity for those at high risk for immune suppression and subsequent morbidity in pediatric burn patients. We designed a single-center, prospective, observational study at an American Burn Association-verified pediatric burn center to test the association of burn size, depth, and etiology to established innate and adaptive immune markers in pediatric burn patients (8)(9)(10).…”