Publications

Host-derived proteases can augment or help to clear infections. This dichotomy is exemplified by cathepsin L (CTSL), which helps Hendra virus and SARS coronavirus to invade cells, but is essential for survival in mice with mycoplasma pneumonia. The present study tested the hypothesis that CTSL protects mice from serious consequences of infection by the orthomyxovirus influenza A, which is thought to be activated by host-supplied proteases other than CTSL. Ctsl-/- mice infected with influenza A/Puerto Rico/8/34(H1N1) had larger lung viral loads and higher mortality than infected Ctsl+/+ mice. Lung inflammation in surviving infected mice peaked 14 days after initial infection, accompanied marked focal distal airway bronchiolization and epithelial metaplasia followed by desquamation and fibrotic interstitial remodeling, and persisted for at least 6 weeks. Most deaths occurred during the second week of infection in both groups of mice. In contrast to mycoplasma pneumonia, infiltrating cells were predominantly mononuclear rather than polymorphonuclear. The histopathology of lung inflammation and remodeling in survivors was similar in Ctsl-/- and Ctsl+/+ mice, although Ctsl+/+ mice cleared immunoreactive virus sooner. Furthermore, Ctsl-/- mice had profound deficits in CD4+ lymphocytes before and after infection and weaker production of pathogen-specific IgG. Thus, CTSL appears to support innate as well as adaptive responses, which confer a survival advantage on mice infected with the orthomyxovirus influenza A.

BACKGROUND

In malaria-endemic areas, the first exposure to malaria antigens often occurs in utero when the fetal immune system is poised towards the development of tolerance. Children exposed to placental malaria have an increased risk of clinical malaria in the first few years of life compared to unexposed children. Recent work has suggested the potential of pregnancy-associated malaria to induce immune tolerance in children living in malaria-endemic areas. A study was completed to evaluate the effect of malaria exposure during pregnancy on fetal immune tolerance and effector responses.

METHODS

Using cord blood samples from a cohort of mother-infant pairs followed from early in pregnancy until delivery, flow cytometry analysis was completed to assess the relationship between pregnancy-associated malaria and fetal cord blood CD4 and dendritic cell phenotypes.

RESULTS

Cord blood FoxP3 T counts were higher in infants born to mothers with Plasmodium parasitaemia early in pregnancy (12-20 weeks of gestation; p = 0.048), but there was no association between T counts and the presence of parasites in the placenta at the time of delivery (by loop-mediated isothermal amplification (LAMP); p = 0.810). In contrast, higher frequencies of activated CD4 T cells (CD25FoxP3CD127) were observed in the cord blood of neonates with active placental Plasmodium infection at the time of delivery (p = 0.035). This population exhibited evidence of effector memory differentiation, suggesting priming of effector T cells in utero. Lastly, myeloid dendritic cells were higher in the cord blood of infants with histopathologic evidence of placental malaria (p < 0.0001).

CONCLUSION

Together, these data indicate that in utero exposure to malaria drives expansion of both regulatory and effector T cells in the fetus, and that the timing of this exposure has a pivotal role in determining the polarization of the fetal immune response.

BACKGROUND

Timely reperfusion after ST-elevation myocardial infarction (STEMI) improves survival. Guidelines recommend primary percutaneous coronary intervention (PPCI) within 90 minutes of arrival at a PCI-capable hospital. The alternative is fibrinolysis within 30 minutes for those in those for whom timely transfer to a PCI-capable hospital is not feasible.

METHODS AND RESULTS

We identified STEMI patients receiving reperfusion therapy at 229 hospitals participating in the Get With the Guidelines-Coronary Artery Disease (GWTG-CAD) database (January 1, 2003 through December 31, 2008). Temporal trends in the use of fibrinolysis and PPCI, its timeliness, and in-hospital mortality outcomes were assessed. We also assessed predictors of fibrinolysis versus PPCI and compliance with performance measures. Defect-free care was defined as 100% compliance with all performance measures. We identified 29 190 STEMI patients, of whom 2441 (8.4%) received fibrinolysis; 38.2% of these patients achieved door-to-needle times ≤30 minutes. Median door-to-needle times increased from 36 to 60 minutes (P=0.005) over the study period. Among PPCI patients, median door-to-balloon times decreased from 94 to 64 minutes (P<0.0001) over the same period. In-hospital mortality was higher with fibrinolysis than with PPCI (4.6% vs 3.3%, P=0.001) and did not change significantly over time. Patients receiving fibrinolysis were less likely to receive defect-free care compared with their PPCI counterparts.

CONCLUSIONS

Use of fibrinolysis for STEMI has decreased over time with concomitant worsening of door-to-needle times. Over the same time period, use of PPCI increased with improvement in door-to-balloon times. In-hospital mortality was higher with fibrinolysis than with PPCI. As reperfusion for STEMI continues to shift from fibrinolysis to PPCI, it will be critical to ensure that door-to-needle times and outcomes do not worsen.