The Rickettsia conorii OmpB β-Peptide Contributes to Serum Resistance by Interacting with Human Factor H
The ability to survive in the hematogenous circulation is critical to pathogens that are transmitted to mammalian hosts via arthropod vectors. Riley et al. (p. 2735–2743) demonstrate that the β-peptide or translocon domain of the OmpB autotransporter protein from Rickettsia conorii interacts with human factor H and promotes survival in sera by preventing complement deposition at the outer membrane. Moreover, expression of OmpB β-peptide in Escherichia coli is sufficient to promote resistance to serum killing. The high level of sequence identity among OmpB β-peptides from several rickettsial species indicates that serum resistance may be a newly described virulence attribute for this class of pathogens.
Influence of Environment and Maturity on Neonatal Alveolar Macrophage Response to Pneumocystis murina
The opportunistic fungal pathogen Pneumocystis murina is encountered very early in life. Postnatal developing lungs have high levels of anti-inflammatory cytokine transforming growth factor β (TGF-β) and interleukin-10 (IL-10), which may be conducive to prolonged carriage of Pneumocystis in infants. Kurkjian et al. (p. 2835–2846) used neutralizing antibodies, knockout mice, and adoptive transfers and report that TGF-β and IL-10 contribute to, but are not sufficient for, the suppressed function of alveolar macrophages in response to Pneumocystis. Alveolar macrophages from neonates failed to become activated when stimulated with the cyst form of the organisms, demonstrating that environment and intrinsic defects contribute to delayed clearance of Pneumocystis in infant mice.
Role of PGLYRP2 in Host Response to Salmonella enterica serovar Typhimurium In Vivo
Several Drosophila peptidoglycan recognition proteins (PGRPs) play key roles in host defense by binding and cleaving bacterial peptidoglycan. In contrast, the role of mammalian PGRPs in host defense is less clear. Lee et al. (p. 2645–2654) investigated the role of PGLYRP2, a mammalian homolog of PGRPs, in an in vivo model of enteric infection. They show that PGLYRP2 expression is upregulated in the intestinal mucosa following infection. PGLYRP2 is critical for host defense against Salmonella enterica serovar Typhimurium and acts in a Nod1/Nod2-independent manner to favor the recruitment of polymorphonuclear leukocytes. Thus, like Drosophila PGRPs, mammalian PGLYRP2 controls mucosal innate defense against bacterial pathogens.
Novel Lipoprotein Pilotin Required for Secretin Assembly in Enterotoxigenic Escherichia coli
Secretion of the heat-labile enterotoxin by the type II secretion system (T2SS) is a major virulence factor of the enterotoxigenic Escherichia coli (ETEC) pathotype. Strozen et al. (p. 2608–2622) describe the existence of two T2SSs in ETEC strain H10407, only one of which (designated beta [T2SSβ]) is active under a number of growth conditions. They further demonstrate the function of a novel lipoprotein pilotin (YghG; renamed GspSβ) in the localization and subsequent assembly of the GspDβ secretin in the outer membrane.
Neutrophils Prevent Dissemination of Vibrio cholerae
Cholera, marked by a secretory diarrhea caused by the Gram-negative pathogen Vibrio cholerae, is traditionally considered a noninflammatory disease. Cholera has recently been described as having a low-level proinflammatory phase early during infection. Queen and Satchell (p. 2905–2913) model this proinflammatory phase in an adult mouse model of disease and elucidate a role for neutrophils in controlling systemic infection. In contrast, neutrophils do not effectively reduce local infection within the small intestine, except in the absence of accessory toxins. These findings broaden our understanding of innate immune defenses against V. cholerae infection and, thus, have implications for cholera vaccine design.
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- The Rickettsia conorii OmpB β-Peptide Contributes to Serum Resistance by Interacting with Human Factor H
- Influence of Environment and Maturity on Neonatal Alveolar Macrophage Response to Pneumocystis murina
- Role of PGLYRP2 in Host Response to Salmonella enterica serovar Typhimurium In Vivo
- Novel Lipoprotein Pilotin Required for Secretin Assembly in Enterotoxigenic Escherichia coli
- Neutrophils Prevent Dissemination of Vibrio cholerae
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