No abstract

Possession of a properly functioning innate immune system in the lung is vital to prevent infections due to the ongoing exposure of the lung to pathogens. While mechanisms of pulmonary innate immunity have been well studied, our knowledge of how these systems are altered in disease states, leading to increased susceptibility to infections, is limited. One innate immune protein in the lung, the pulmonary collectin SP-D, has been shown to be important in innate immune defense, as well as clearance of allergens and apoptotic cells. MMP-9 is a protease with a wide variety of substrates, and has been found to be dysregulated in a myriad of lung diseases ranging from asthma to cystic fibrosis; in many of these conditions, there are decreased levels of SP-D. Our results indicate that MMP-9 is able to cleave SP-D in vitro and this cleavage leads to loss of its innate immune functions, including its abilities to aggregate bacteria and increase phagocytosis by mouse alveolar macrophages. However, MMP-9-cleaved SP-D was still detected in a solid-phase E. coli LPS-binding assay, while NE-cleaved SP-D was not. In addition, MMP-9 seems to cleave SP-D much more efficiently than NE at physiological levels of calcium. Previous studies have shown that in several diseases, including cystic fibrosis and asthma, patients have increased expression of MMP-9 in the lungs as well as decreased levels of intact SP-D. As patients suffering from many of the diseases in which MMP-9 is over-expressed can be more susceptible to pulmonary infections, it is possible that MMP-9 cleavage of SP-D may contribute to this phenotype.

Loss of NADPH oxidase activity leads to altered phagocyte responses and exaggerated inflammation in Chronic Granulomatous Disease (CGD). We sought to assess the effects of Nox2 absence on monocyte-derived macrophages (MoMacs) in gp91phox-/y mice during zymosan-induced peritonitis. MoMacs from CGD and wild type (WT) peritonea were characterized over time after zymosan injection. Though numbers lavaged from both genotypes were virtually identical, there were marked differences in maturation: newly recruited WT MoMacs rapidly enlarged and matured, losing Ly6C and gaining MHCII, CD206 and CD36, while CGD MoMacs remained small and were mostly Ly6C+MHCII-. RNAseq analyses showed few intrinsic differences between genotypes in newly recruited MoMacs but significant differences with time. WT MoMacs demonstrated changes in metabolism, adhesion and reparative functions, while CGD MoMacs remained inflammatory. PKH dye labeling demonstrated that while WT MoMacs were mostly recruited within the first 24h and remained in the peritoneum while maturing and enlarging, CGD monocytes streamed into the peritoneum for days with many migrating to the diaphragm where they were found in fibrin(ogen) clots surrounding clusters of neutrophils in nascent pyogranulomata. Importantly, these observations appeared to be driven by milieu: adoptive transfer of CGD MoMacs into inflamed peritonea of WT mice resulted in immunophenotypic maturation and normal behavior, whereas altered maturation/behavior of WT MoMacs resulted from transfer into inflamed peritonea of CGD mice. Additionally, Nox2-deficient MoMacs behaved similarly to their Nox2-sufficient counterparts within the largely WT milieu of mixed bone marrow chimeras. These data demonstrate persistent recruitment with fundamental failure of MoMac maturation in CGD.

e The Gram-negative intracellular bacterium Salmonella enterica serovar Typhimurium causes persistent systemic inflammatory disease in immunocompetent mice. Following oral inoculation with S. Typhimurium, mice develop a hematopathological syndrome akin to typhoid fever with splenomegaly, microcytic anemia, extramedullary erythropoiesis, and increased hemophagocytic macrophages in the bone marrow, liver, and spleen. Additionally, there is marked loss of iron from the spleen, an unanticipated result, given the iron sequestration reported in anemia of inflammatory disease. To establish why tissue iron does not accumulate, we evaluated multiple measures of pathology for 4 weeks following oral infection in mice. We demonstrate a quantitative decrease in splenic iron following infection despite increased numbers of splenic phagocytes. Infected mice have increased duodenal expression of the iron exporter ferroportin-1, consistent with increased uptake of dietary iron. Liver and splenic macrophages also express high levels of ferroportin-1. These observations indicate that splenic and hepatic macrophages export iron during S. Typhimurium infection, in contrast to macrophage iron sequestration observed in anemia of inflammatory disease. Tissue macrophage export of iron occurs concurrent with high serum concentrations of interferon gamma (IFN-␥) and interleukin 12 (IL-12). In individual mice, high concentrations of both proinflammatory (tumor necrosis factor alpha [TNF-␣])and anti-inflammatory (IL-10) cytokines in serum correlate with increased tissue bacterial loads throughout 4 weeks of infection. These in vivo observations are consistent with previous cell culture studies and suggest that the relocation of iron from tissue macrophages during infection may contribute to anemia and also to host survival of acute S. Typhimurium infection.T yphoid fever is acquired upon oral ingestion of food or water contaminated with Salmonella enterica serovar Typhi or Paratyphi and remains a serious threat to public health, especially in developing countries (1). Human typhoid fever causes a broad range of clinical signs, including splenomegaly, neuropathy, and hematopathology, such as cytopenias (2), that have been modeled in laboratory mice infected with Salmonella enterica serovar Typhimurium (3). Inbred mouse strains with differing genetic backgrounds are characterized as either sensitive or resistant to S. Typhimurium. Sensitivity to the intracellular bacterial infection is caused by genetic deficiencies in the innate or adaptive immune system (4, 5). For instance, mice lacking the cation transporter Nramp1 (Slc11a1), a regulator of cellular iron metabolism, are extremely sensitive to infection. Nramp1 ϩ mice are considered resistant to S. Typhimurium, because infection is generally nonfatal (6-8). Resistant mice infected by natural oral inoculation develop systemic infection with an acute hematopathological syndrome similar to that of humans with typhoid fever, including fever, anemia, inflammatory disease characterized by periph...

Breast milk is a vehicle of infection and source of protection in post-natal mother-to-child HIV-1 transmission (MTCT). Understanding the mechanism by which breast milk limits vertical transmission will provide critical insight into the design of preventive and therapeutic approaches to interrupt HIV-1 mucosal transmission. However, characterization of the inhibitory activity of breast milk in human intestinal mucosa, the portal of entry in postnatal MTCT, has been constrained by the limited availability of primary mucosal target cells and tissues to recapitulate mucosal transmission ex vivo. Here, we characterized the impact of skimmed breast milk, breast milk antibodies (Igs) and non-Ig components from HIV-1-infected Ugandan women on the major events of HIV-1 mucosal transmission using primary human intestinal cells and tissues. HIV-1-specific IgG antibodies and non-Ig components in breast milk inhibited the uptake of Ugandan HIV-1 isolates by primary human intestinal epithelial cells, viral replication in and transport of HIV-1- bearing dendritic cells through the human intestinal mucosa. Breast milk HIV-1-specific IgG and IgA, as well as innate factors, blocked the uptake and transport of HIV-1 through intestinal mucosa. Thus, breast milk components have distinct and complementary effects in reducing HIV-1 uptake, transport through and replication in the intestinal mucosa and, therefore, likely contribute to preventing postnatal HIV-1 transmission. Our data suggests that a successful preventive or therapeutic approach would require multiple immune factors acting at multiple steps in the HIV-1 mucosal transmission process.