Cutting Edge: CCR9 Promotes CD8+ T Cell Recruitment to the Brain during Congenital Cytomegalovirus Infection.

CD8+ T lymphocytes infiltrate the brain during congenital CMV infection and promote viral clearance. However, the mechanisms by which CD8+ T cells are recruited to the brain remain unclear. Using a mouse model of congenital CMV, we found a gut-homing chemokine receptor (CCR9) was preferentially expressed in CD8+ T cells localized in the brain postinfection. In the absence of CCR9 or CCL25 (CCR9's ligand) expression, CD8+ T cells failed to migrate to key sites of infection in the brain and protect the host from severe forms of disease. Interestingly, we found that expression of CCR9 on CD8+ T cells was also responsible for spatial temporal positioning of T cells in the brain. Collectively, our data demonstrate that the CMV-infected brain uses a similar mechanism for CD8+ T cell homing as the small intestine.

Tamoxifen administration alters gastrointestinal motility in mice.

BACKGROUND: Tamoxifen is widely used for Cre-estrogen receptor-mediated genomic recombination in transgenic mouse models to mark cells for lineage tracing and to study gene function. However, recent studies have highlighted off-target effects of tamoxifen in various tissues and cell types when used for induction of Cre recombination. Despite the widespread use of these transgenic Cre models to assess gastrointestinal (GI) function, the effect of tamoxifen exposure on GI motility has not been described. METHODS: We examined the effects of tamoxifen on GI motility by measuring total GI transit, gastric emptying, small intestinal transit, and colonic contractility in wild-type adult mice. KEY RESULTS: We observed a significant delay in total GI transit in tamoxifen-treated mice, with unaltered gastric emptying, accelerated small intestinal transit, and abnormal colonic motility. CONCLUSION: Our findings highlight the importance of considering GI motility alterations induced by tamoxifen when designing protocols that utilize tamoxifen as a Cre-driver for studying GI function.

Hypoganglionosis in the gastric antrum causes delayed gastric emptying.

BACKGROUND: Enteric nervous system (ENS) abnormalities have been implicated in delayed gastric emptying but studies exploring potential treatment options are limited by the lack of an experimental animal model. We examined the ENS abnormalities in the mouse stomach associated with aging, developed a novel model of gastroparesis, and established a new approach to measure gastric emptying. METHODS: A modified gastric emptying assay was developed, validated in nNOS -/- mice, and tested in mice at multiple ages. Age-related changes in ENS structure were analyzed by immunohistochemistry. Gastric aganglionosis was generated in Wnt1-iDTR mice using focal administration of diphtheria toxin (DT) into the anterior antral wall. KEY RESULTS: Older mice (>5 months) exhibit hypoganglionosis in the gastric antrum and a decreased proportion of nNOS neurons as compared to younger mice (age 5-7 weeks). This was associated with a significant age-dependent decrease in liquid and solid gastric emptying. A novel model of gastric antrum hypoganglionosis was established using neural crest-specific expression of diphtheria toxin receptor. In this model, a significant reduction in liquid and solid gastric emptying is observed. CONCLUSIONS & INFERENCES: Older mice exhibit delayed gastric emptying associated with hypoganglionosis and a reduction in nNOS-expressing neurons in the antrum. The causal relationship between antral hypoganglionosis and delayed gastric emptying was verified using a novel experimental model of ENS ablation. This study provides new information regarding the pathogenesis of delayed gastric emptying and provides a robust model system to study this disease and develop novel treatments.

The Estimated Verbal GCS Subscore in Intubated Traumatic Brain Injury Patients: Is it Really Better?

The Glasgow Coma Scale (GCS) has limited utility in intubated patients due to the inability to assign verbal subscores. The verbal subscore can be derived from the eye and motor subscores using a mathematical model, but the advantage of this method and its use in outcome prognostication in traumatic brain injury (TBI) patients remains unknown. We compared the validated "Core+CT"-IMPACT-model performance in 251 intubated TBI patients prospectively enrolled in the longitudinal OPTIMISM study between November 2009 and May 2015 when substituting the original motor GCS (mGCS) with the total estimated GCS (teGCS; with estimated verbal subscore). We hypothesized that model performance would improve with teGCS. Glasgow Outcome Scale (GOS) scores were assessed at 3 and 12 months by trained interviewers. In the complete case analysis, there was no statistically or clinically significant difference in the discrimination (C-statistic) at either time-point using the mGCS versus the teGCS (3 months: 0.893 vs. 0.871;12 months: 0.926 vs. 0.92). At 3 months, IMPACT-model calibration was excellent with mGCS and teGCS (Hosmer-Lemeshow "goodness-of-fit" chi square p value 0.9293 and 0.9934, respectively); it was adequate at 12 months with teGCS (0.5893) but low with mGCS (0.0158), possibly related to diminished power at 12 months. At both time-points, motor GCS contributed more to the variability of outcome (Nagelkerke ΔR2) than teGCS (3 months: 5.8% vs. 0.4%; 12 months: 5% vs. 2.6%). The sensitivity analysis with imputed missing outcomes yielded similar results, with improved calibration for both GCS variants. In our cohort of intubated TBI patients, there was no statistically or clinically meaningful improvement in the IMPACT-model performance by substituting the original mGCS with teGCS.