The spinal cord injury-induced immune deficiency syndrome: results of the SCIentinel study.

Infections are prevalent after spinal cord injury (SCI), constitute the main cause of death and are a rehabilitation confounder associated with impaired recovery. We hypothesize that SCI causes an acquired lesion-dependent (neurogenic) immune suppression as an underlying mechanism to facilitate infections. The international prospective multicentre cohort study (SCIentinel; protocol registration DRKS00000122; n = 111 patients) was designed to distinguish neurogenic from general trauma-related effects on the immune system. Therefore, SCI patient groups differing by neurological level, i.e. high SCI [thoracic (Th)4 or higher]; low SCI (Th5 or lower) and severity (complete SCI; incomplete SCI), were compared with a reference group of vertebral fracture (VF) patients without SCI. The primary outcome was quantitative monocytic Human Leukocyte Antigen-DR expression (mHLA-DR, synonym MHC II), a validated marker for immune suppression in critically ill patients associated with infection susceptibility. mHLA-DR was assessed from Day 1 to 10 weeks after injury by applying standardized flow cytometry procedures. Secondary outcomes were leucocyte subpopulation counts, serum immunoglobulin levels and clinically defined infections. Linear mixed models with multiple imputation were applied to evaluate group differences of logarithmic-transformed parameters. Mean quantitative mHLA-DR [ln (antibodies/cell)] levels at the primary end point 84 h after injury indicated an immune suppressive state below the normative values of 9.62 in all groups, which further differed in its dimension by neurological level: high SCI [8.95 (98.3% confidence interval, CI: 8.63; 9.26), n = 41], low SCI [9.05 (98.3% CI: 8.73; 9.36), n = 29], and VF without SCI [9.25 (98.3% CI: 8.97; 9.53), n = 41, P = 0.003]. Post hoc analysis accounting for SCI severity revealed the strongest mHLA-DR decrease [8.79 (95% CI: 8.50; 9.08)] in the complete, high SCI group, further demonstrating delayed mHLA-DR recovery [9.08 (95% CI: 8.82; 9.38)] and showing a difference from the VF controls of -0.43 (95% CI: -0.66; -0.20) at 14 days. Complete, high SCI patients also revealed constantly lower serum immunoglobulin G [-0.27 (95% CI: -0.45; -0.10)] and immunoglobulin A [-0.25 (95% CI: -0.49; -0.01)] levels [ln (g/l × 1000)] up to 10 weeks after injury. Low mHLA-DR levels in the range of borderline immunoparalysis (below 9.21) were positively associated with the occurrence and earlier onset of infections, which is consistent with results from studies on stroke or major surgery. Spinal cord injured patients can acquire a secondary, neurogenic immune deficiency syndrome characterized by reduced mHLA-DR expression and relative hypogammaglobulinaemia (combined cellular and humoral immune deficiency). mHLA-DR expression provides a basis to stratify infection-risk in patients with SCI.

The SCIentinel study--prospective multicenter study to define the spinal cord injury-induced immune depression syndrome (SCI-IDS)--study protocol and interim feasibility data.

BACKGROUND: Infections are the leading cause of death in the acute phase following spinal cord injury and qualify as independent risk factor for poor neurological outcome ("disease modifying factor"). The enhanced susceptibility for infections is not stringently explained by the increased risk of aspiration in tetraplegic patients, neurogenic bladder dysfunction, or by high-dose methylprednisolone treatment. Experimental and clinical pilot data suggest that spinal cord injury disrupts the balanced interplay between the central nervous system and the immune system. The primary hypothesis is that the Spinal Cord Injury-induced Immune Depression Syndrome (SCI-IDS) is 'neurogenic' including deactivation of adaptive and innate immunity with decreased HLA-DR expression on monocytes as a key surrogate parameter. Secondary hypotheses are that the Immune Depression Syndrome is i) injury level- and ii) severity-dependent, iii) triggers transient lymphopenia, and iv) causes qualitative functional leukocyte deficits, which may endure the post-acute phase after spinal cord injury. METHODS/DESIGN: SCIentinel is a prospective, international, multicenter study aiming to recruit about 118 patients with acute spinal cord injury or control patients with acute vertebral fracture without neurological deficits scheduled for spinal surgery. The assessment points are: i) <31 hours, ii) 31-55 hours, iii) 7 days, iv) 14 days, and v) 10 weeks post-trauma. Assessment includes infections, concomitant injury, medication and neurological classification using American Spinal Injury Association impairment scale (AIS) and neurological level. Laboratory analyses comprise haematological profiling, immunophenotyping, including HLA-DR expression on monocytes, cytokines and gene expression of immune modulators. We provide an administrative interim analysis of the recruitment schedule of the trial. DISCUSSION: The objectives are to characterize the dysfunction of the innate and adaptive immune system after spinal cord injury and to explore its proposed 'neurogenic' origin by analyzing its correlation with lesion height and severity. The trial protocol considers difficulties of enrolment in an acute setting, and loss to follow up. The administrative interim analysis confirmed the feasibility of the protocol. Better understanding of the SCI-IDS is crucial to reduce co-morbidities and thereby to attenuate the impact of disease modifying factors to protect neurological "outcome at risk". This putatively results in improved spinal cord injury medical care. TRIAL REGISTRATION DRKS-ID: DRKS00000122 (German Clinical Trials Registry).