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Silver Spring, MD, United States

Guerry P.,Naval Medical Research Center Silver Spring
Frontiers in cellular and infection microbiology

Campylobacter jejuni remains a major cause of bacterial diarrhea worldwide and is associated with numerous sequelae, including Guillain Barré Syndrome, inflammatory bowel disease, reactive arthritis, and irritable bowel syndrome. C. jejuni is unusual for an intestinal pathogen in its ability to coat its surface with a polysaccharide capsule (CPS). These capsular polysaccharides vary in sugar composition and linkage, especially those involving heptoses of unusual configuration and O-methyl phosphoramidate linkages. This structural diversity is consistent with CPS being the major serodeterminant of the Penner scheme, of which there are 47 C. jejuni serotypes. Both CPS expression and expression of modifications are subject to phase variation by slip strand mismatch repair. Although capsules are virulence factors for other pathogens, the role of CPS in C. jejuni disease has not been well defined beyond descriptive studies demonstrating a role in serum resistance and for diarrhea in a ferret model of disease. However, perhaps the most compelling evidence for a role in pathogenesis are data that CPS conjugate vaccines protect against diarrheal disease in non-human primates. A CPS conjugate vaccine approach against this pathogen is intriguing, but several questions need to be addressed, including the valency of CPS types required for an effective vaccine. There have been numerous studies of prevalence of CPS serotypes in the developed world, but few studies from developing countries where the disease incidence is higher. The complexity and cost of Penner serotyping has limited its usefulness, and a recently developed multiplex PCR method for determination of capsule type offers the potential of a more rapid and affordable method. Comparative studies have shown a strong correlation of the two methods and studies are beginning to ascertain CPS-type distribution worldwide, as well as examination of correlation of severity of illness with specific CPS types. Source

Campo J.J.,Naval Medical Research Center Silver Spring | Campo J.J.,University of Barcelona | Whitman T.J.,National Naval Medical Center | Freilich D.,Naval Medical Research Center Silver Spring | And 7 more authors.

Background: Biomarkers of exposure to Plasmodium falciparum would be a useful tool for the assessment of malaria burden and analysis of intervention and epidemiological studies. Antibodies to pre-erythrocytic antigens represent potential surrogates of exposure. Methods and Findings: In an outbreak cohort of U.S. Marines deployed to Liberia, we modeled pre- and post-deployment IgG against P. falciparum sporozoites by immunofluorescence antibody test, and both IgG and IgM against the P. falciparum circumsporozoite protein by enzyme-linked immunosorbant assay. Modeling seroconversion thresholds by a fixed ratio, linear regression or nonlinear regression produced sensitivity for identification of exposed U.S. Marines between 58-70% and specificities between 87-97%, compared with malaria-naïve U.S. volunteers. Exposure was predicted in 30-45% of the cohort. Conclusion: Each of the three models tested has merits in different studies, but further development and validation in endemic populations is required. Overall, these models provide support for an antibody-based surrogate marker of exposure to malaria. Source

Zins S.R.,Naval Medical Research Center Silver Spring | Amare M.F.,Naval Medical Research Center Silver Spring | Anam K.,Naval Medical Research Center Silver Spring | Elster E.A.,Naval Medical Research Center Silver Spring | And 2 more authors.
Journal of Inflammation

Background. Severe trauma can induce pathophysiological responses that have marked inflammatory components. The development of systemic inflammation following severe thermal injury has been implicated in immune dysfunction, delayed wound healing, multi-system organ failure and increased mortality. Methods. In this study, we examined the impact of thermal injury-induced systemic inflammation on the healing response of a secondary wound in the MRL/MpJ mouse model, which was anatomically remote from the primary site of trauma, a wound that typically undergoes scarless healing in this specific strain. Ear-hole wounds in MRL/MpJ mice have previously displayed accelerated healing and tissue regeneration in the absence of a secondary insult. Results. Severe thermal injury in addition to distal ear-hole wounds induced marked local and systemic inflammatory responses in the lungs and significantly augmented the expression of inflammatory mediators in the ear tissue. By day 14, 61% of the ear-hole wounds from thermally injured mice demonstrated extensive inflammation with marked inflammatory cell infiltration, extensive ulceration, and various level of necrosis to the point where a large percentage (38%) had to be euthanized early during the study due to extensive necrosis, inflammation and ear deformation. By day 35, ear-hole wounds in mice not subjected to thermal injury were completely closed, while the ear-hole wounds in thermally injured mice exhibited less inflammation and necrosis and only closed partially (62%). Thermal injury resulted in marked increases in serum levels of IL-6, TNF, KC (CXCL1), and MIP-2 (CXCL2). Interestingly, attenuated early ear wound healing in the thermally injured mouse resulted in incomplete tissue regeneration in addition to a marked inflammatory response, as evidenced by the histological appearance of the wound and increased transcription of potent inflammatory mediators. Conclusion. These findings suggest that the observed systemic inflammatory response of a severe thermal injury undoubtedly has an adverse effect on wound healing and tissue regeneration. © 2010 Zins et al; licensee BioMed Central Ltd. Source

Abeykoon A.H.,Georgetown University | Chao C.-C.,Naval Medical Research Center Silver Spring | Wang G.,U.S. National Institutes of Health | Gucek M.,U.S. National Institutes of Health | And 2 more authors.
Journal of Bacteriology

Rickettsia prowazekii, the etiologic agent of epidemic typhus, is a potential biological threat agent. Its outer membrane protein B (OmpB) is an immunodominant antigen and plays roles as protective envelope and as adhesins. The observation of the correlation between methylation of lysine residues in rickettsial OmpB and bacterial virulence has suggested the importance of an enzymatic system for the methylation of OmpB. However, no rickettsial lysine methyltransferase has been characterized. Bioinformatic analysis of genomic DNA sequences of Rickettsia identified putative lysine methyltransferases. The genes of the potential methyltransferases were synthesized, cloned, and expressed in Escherichia coli, and expressed proteins were purified by nickelnitrilotriacetic acid (Ni-NTA) affinity chromatography. The methyltransferase activities of the purified proteins were analyzed by methyl incorporation of radioactively labeled S-adenosylmethionine into recombinant fragments of OmpB. Two putative recombinant methyltransferases (rRP789 and rRP027-028) methylated recombinant OmpB fragments. The specific activity of rRP789 is 10-to 30-fold higher than that of rRP027-028. Western blot analysis using specific antibodies against trimethyl lysine showed that both rRP789 and rRP027-028 catalyzed trimethylation of recombinant OmpB fragments. Liquid chromatographytandem mass spectrometry (LC/MS-MS) analysis showed that rRP789 catalyzed mono-, di-, and trimethylation of lysine, while rRP027-028 catalyzed exclusively trimethylation. To our knowledge, rRP789 and rRP027-028 are the first biochemically characterized lysine methyltransferases of outer membrane proteins from Gram-negative bacteria. The production and characterization of rickettsial lysine methyltransferases provide new tools to investigate the mechanism of methylation of OmpB, effects of methylation on the structure and function of OmpB, and development of methylated OmpB-based diagnostic assays and vaccine candidates. © 2012, American Society for Microbiology. Source

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