Publications

The molecular processes underlying epidemic waves of methicillin-resistant Staphylococcus aureus (MRSA) infection are poorly understood(1). Although a major role has been attributed to the acquisition of virulence determinants by horizontal gene transfer(2), there are insufficient epidemiological and functional data supporting that concept. We here report the spread of clones containing a previously extremely rare(3,4) mobile genetic element–encoded gene, sasX. We demonstrate that sasX has a key role in MRSA colonization and pathogenesis, substantially enhancing nasal colonization, lung disease and abscess formation and promoting mechanisms of immune evasion. Moreover, we observed the recent spread of sasX from sequence type 239 (ST239) to invasive clones belonging to other sequence types. Our study identifies sasX as a quickly spreading crucial determinant of MRSA pathogenic success and a promising target for therapeutic interference. Our results provide proof of principle that horizontal gene transfer of key virulence determinants drives MRSA epidemic waves.

BACKGROUND

Among patients with asthma, the clinical effect and relative contribution of maternal smoking during pregnancy (in utero smoking) and current secondhand smoke (SHS) exposure on asthma control is poorly documented, and there is a paucity of research involving minority populations.

OBJECTIVES

We sought to examine the association between poor asthma control and in utero smoking and current SHS exposure among Latino and black children with asthma.

METHODS

We performed a case-only analysis of 2 multicenter case-control studies conducted from 2008-2010 with similar protocols. We recruited 2481 Latino and black subjects with asthma (ages 8-17 years) from the mainland United States and Puerto Rico. Ordinal logistic regression was used to estimate the effect of in utero smoking and current SHS exposures on National Heart, Lung, and Blood Institute-defined asthma control.

RESULTS

Poor asthma control among children 8 to 17 years of age was independently associated with in utero smoking (odds ratio [OR], 1.5; 95% CI, 1.1-2.0). In utero smoking through the mother was also associated with secondary asthma outcomes, including early-onset asthma (OR, 1.7; 95% CI, 1.1-2.4), daytime symptoms (OR, 1.6; 95% CI, 1.1-2.1), and asthma-related limitation of activities (OR, 1.6; 95% CI, 1.2-2.2).

CONCLUSIONS

Maternal smoking while in utero is associated with poor asthma control in black and Latino subjects assessed at 8-17 years of age.

Vitamin D deficiency is adversely associated with diseases characterized by inflammation. The combination of the high incidence of vitamin D deficiency in patients undergoing allogeneic stem cell transplants (SCT) and the potential role of vitamin D deficiency in influencing graft-versus-host disease led us to further characterize the expression of VDR on alloreactive T cells. We hypothesized that vitamin D receptor expression may directly regulate alloreactive T cell responses. To overcome existing limitations in measuring VDR in bulk cellular populations, we developed a flow cytometric assay to measure cytoplasmic VDR in human T cells. Upon stimulation, VDR was expressed extremely early and exhibited sustained upregulation with chronic stimulation. VDR expression was also coupled to cytokine production, proliferation, and ERK1/2 phosphorylation. In addition, VDR exhibited a maturation stage-specific pattern of expression, with greatest expression on cells known to mediate GVHD, naïve and early memory T cells. Alloreactive T cells upregulated VDR, whereas the nonreactive T cells did not. Finally, repletion of vitamin D in vitro was sufficient to significantly reduce alloreactive T cell responses. These data suggest that vitamin D effects on T cells may be important in reducing graft versus host disease (GVHD) in the allogeneic stem cell transplant setting.