The Moraxella catarrhalis ubiquitous surface proteins (UspAs) are autotransporter molecules reported to interact with a variety of different host proteins and to affect processes ranging from serum resistance to cellular adhesion. The role of UspA1 as an adhesin has been confirmed with a number of different human cell types and is mediated by binding to eukaryotic proteins including carcinoembryonic antigen-related cellular adhesion molecules (CEACAMs), fibronectin, and laminin. A distinct difference in the ability of prototypical M. catarrhalis strains to adhere to CEACAM-expressing cell lines prompted us to perform strain-specific structure-function analyses of UspA1 proteins. In this study, we characterized CEACAM binding by a diverse set of UspA1 proteins and showed that 3 out of 10 UspA1 proteins were incapable of binding CEACAM. This difference resulted from the absence of a distinct CEACAM binding motif in nonadhering strains. Our sequence analysis also revealed a single M. catarrhalis isolate that lacked the fibronectin-binding motif and was defective in adherence to Chang conjunctival epithelial cells. These results clearly demonstrate that UspA1-associated adhesive functions are not universally conserved. Instead, UspA1 proteins must be considered as variants with the potential to confer both different cell tropisms and host cell responses.

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Elevation of echocardiography-determined tricuspid regurgitant jet velocity (TRV) predicts high systolic pulmonary artery pressure. The present study tested the hypotheses that elevated tricuspid regurgitant jet velocity is associated with both hemolysis and hypoxia and abnormal 6-min walk test (6MWT) results. This study aims to correlate elevated TRV with different clinical laboratory findings and 6MWT and to find the independent predictors of increased TRV. A prospective study of 80 patients aged 5-25 years old with sickle cell disease (SCD) under basal conditions and 40 matched controls was conducted. Hemolytic analysis was assessed by the levels of lactate dehydrogenase, serum bilirubin, and reticulocyte count. Oxygen saturation determination using pulse oximeter and 6MWT were done. The overall prevalence of elevated TRV (≥2.5 m/s) was 28.75 %. Associated risk factors were older age (r = 0.28, p = 0.01), longer duration of disease (r = 0.25, p = 0.025), higher reticulocytic count (r = 0.344, p = 0.002), lower O2 saturation (r = -0.574, p = 0.0001), and shorter walked distance in 6MWT (r = -0.75, p = 0.0001). By multivariate logistic analysis, only the distance walked during 6MWT was the independent correlate of elevated TRV (odds ratio = 0.85; 95 % CI = 0.74 to 0.98 p = 0.033). The study provides evidence for independent association of TRV with abnormal 6MWT results. The 6-min walk test can be used as noninvasive adjuvant tool for functional capacity assessment of SCD patients with elevated TRV.