063 - Decreased peripheral regulatory T cells are associated with the hyperinflammation seen in neonatal capillary leak syndrome

Publication Number: 63.4469

Timothy J. Boly, University of Iowa Stead Family Children's Hospital, Iowa City, IA, United States; Jennifer Bermick, University of Iowa Stead Family Children's Hospital, Iowa City, IA, United States

Background: Neonatal capillary leak syndrome (CLS) is a rare, but life-threatening, complication following an inflammatory event, such as sepsis, isolated intestinal perforation, or necrotizing enterocolitis, in extremely premature infants. To date, no work has examined the serum inflammatory profile in infants with CLS.

Objective: Determine the immune profile leading to the development of neonatal CLS

Design/Methods: Infants of interest were those born 22 0/7-26 6/7 weeks’ gestation with a diagnosis of neonatal CLS. The comparison group was infants born 22 0/7-26 6/7 weeks’ gestation with culture-positive bacterial sepsis without the diagnosis of capillary leak syndrome. Residual clinical whole blood and serum samples were collected. Peripheral blood mononuclear cells were isolated using Ficoll-Paque separation and were stored at -80C until use. Serum samples were stored at -80C until use. Serum concentrations of IL-1b, sIL2Ra, IL6, IL8, IL10, IP10, MCP1, MIP1a, TNF, TGFb1, TGFb2, and TGFb3 were measured using multiplex protein assay. C-reactive protein (CRP) concentration was determined from the medical record. Flow cytometry was used to evaluate peripheral abundance of CD3, CD4, CD8, CD25, Foxp3, CD16, CD19, and CD14. 2 way ANOVA with multiple comparisons was used to evaluate the serum cytokine and flow cytometry data.

Results: 6 infants with CLS were included and compared to 8 infants with blood culture-positive infections. Serum analysis demonstrated significant elevations of IL6 (13442 pg/mL vs 745 pg/mL, p< 0.0001) and IL8 (9026 pg/mL vs 802 pg/mL, p=0.004) in infants with CLS on the initial day of illness (Figure 1). Flow cytometry demonstrated a significant, persistent decrease in the regulatory T cell (CD4+CD25+Foxp3+) population in infants with CLS that was present prior to and during the CLS period. This alteration in the regulatory T cell population was noted to persist after resolution of CLS (Figure 2). No significant differences were noted in the other cell populations.

Conclusion(s): Significant decreases in the regulatory T cell population are seen in infants that develop neonatal CLS. This is likely associated with the release of significant higher concentrations of pro-inflammatory IL6 and IL8 during periods of inflammation. Further work is ongoing to assess the underlying regulatory T cell deficiency.

Figure 1
Serum cytokine concentrations at (A) 7 days prior to illness, (B) the day of illness onset, and (C) 28 days post-illness onset.

Figure 2
CD8+, CD4+, and CD4+CD25+Foxp3+ populations presented as percentage of total peripheral CD3+ cells at (A) 7 days prior to illness, (B) the day of illness onset, and (C) 28 days post-illness onset.