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Infection and Immunity, December 2006, p. 6513, Vol. 74, No. 12
0019-9567/06/$08.00+0     doi:10.1128/IAI.01653-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

SPOTLIGHT

Articles of Significant Interest Selected from This Issue by the Editors

Antimicrobial peptides are considered to be our own endogenous antibiotics. Bergman et al. (p. 6982-6991) investigated whether these peptides are involved in the chemical defense of the blood-brain barrier (BBB) and meninges. By infecting mice with Neisseria meningitidis, they demonstrated a pronounced induction of the antimicrobial peptide CRAMP (cathelin-related antimicrobial peptide) in endothelial cells of the BBB and in cells of the meninges. In functional studies CRAMP knockout mice were more susceptible to meningococcal sepsis than wild-type mice, although CRAMP per se did not appear to protect the brain from invasion of meningococci. These results indicate a role for CRAMP in the defense against meningococcal disease and suggest a novel paradigm of antimicrobial peptides as constituents of brain host defense.

Alveolar Neutrophils Aggregate with Aspergillus Conidia and Inhibit Germination

Neutropenia is a risk factor for invasive pulmonary aspergillosis, which is usually caused by Aspergillus fumigatus. Findings by Bonnett et al. (p. 6528-6539) challenge a common view that alveolar macrophages attack conidia and that neutrophils primarily attack hyphae. They show instead that following pulmonary instillation of conidia, recruited neutrophils form NADPH oxidase-active aggregates with conidia and inhibit their germination. The rate of neutrophil recruitment is important since in strains of mice where recruitment is slower, significantly more conidial germination occurs.

The Atypical Chemokine CXCL16 Regulates Cell-Mediated Immunity to Salmonella enterica Serovar Enteritidis via Promotion of Gamma Interferon Production

Chemokines, or chemotactic cytokines, play a crucial role in leukocyte trafficking. CXCL16 is a recently discovered chemokine that regulates migration of activated T lymphocytes and plays a direct role in the binding and phagocytosis of bacteria by professional antigen-presenting cells. However, its precise role in the immune response to bacteria is not well understood. Using a mouse model of infection, Fahy et al. (p. 6885-6894) show that CXCL16 plays a crucial role in the control of Salmonella enterica serovar Enteritidis colonization of target organs and, more specifically, in the regulation of the cell-mediated arm of the primary immune response to serovar Enteritidis.

Simple Peptide Vaccines for a Complex Parasite?

Over 40% of the world's population is at risk of malaria and vaccines are needed to prevent the 300- to 500-million infections and 1- to 2-million deaths caused by the Plasmodium parasite each year. Calvo-Calle et al. (p. 6929-6939) show that a 48-mer linear peptide vaccine, containing epitopes derived from a Plasmodium falciparum sporozoite immunodominant surface antigen, can elicit antibodies that protect immunized mice against sporozoites injected by malaria-infected mosquitoes. These findings suggest that simple synthetic peptides may provide inexpensive and readily produced malaria vaccines that can neutralize sporozoite infectivity and prevent development of blood-stage parasites that cause clinical disease.

Did Acid Fermentation Lead to the Global Elimination of the Classical Biotype of Vibrio cholerae?

Within a decade of the invasion of the El Tor biotype into South Asia, the classical biotype of Vibrio cholerae was eliminated as a cause of cholera in the region. Yoon and Mekalanos (p. 6547-6556) present data that suggest that a defect in metabolism of sugars present in classical strains may have been responsible for their global elimination by El Tor strains. Growth on environmental polysaccharides such as chitin is predicted to have generated lethal levels of acid for classical strains but not for El Tor strains, thus leading to a competitive edge for the latter. The metabolism of sugars in the human host may also favor the El Tor biotype.

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