The complex roles of NADPH oxidases in fungal infection

NADPH oxidases play key roles in immunity and inflammation that go beyond the production of microbicidal reactive oxygen species (ROS). The past decade has brought a new appreciation for the diversity of roles played by ROS in signalling associated with inflammation and immunity. NADPH oxidase activity affects disease outcome during infections by human pathogenic fungi, an important group of emerging and opportunistic pathogens that includes Candida, Aspergillus and Cryptococcus species. Here we review how alternative roles of NADPH oxidase activity impact fungal infection and how ROS signalling affects fungal physiology. Particular attention is paid to roles for NADPH oxidase in immune migration, immunoregulation in pulmonary infection, neutrophil extracellular trap formation, autophagy and inflammasome activity. These recent advances highlight the power and versatility of spatiotemporally controlled redox regulation in the context of infection, and point to a need to understand the molecular consequences of NADPH oxidase activity in the cell.     

Threshold conditions for infection persistence in complex host-vectors interactions

As classically defined by Macdonald in the early 1950s, for the case of diseases with one vector and one host, the Basic Reproduction Number, R0, is defined as the number of secondary infections caused by a single infective of the same type (vector or host) during its infectiousness period in an entirely susceptible population. In the case of a disease which has one vector and one host, it is easy to show that R0 coincides with the threshold for the establishment of an endemic state: if R0 > 1 (< 1), the disease can invade (cannot invade) the host population. In this paper we examine various epidemic situations in which there are more than one vector and/or host. We show that in those more complex systems it is not possible to deduce a single R0 but rather a threshold for infection persistence which is a composite of several quantities closely related to the classical expression of R0. Another definition of R0 given by Diekmann, Heesterbeek and Metz, and denoted in this paper R0NGO is discussed and applied as an alternative to calculate the thresholds for infection establishment.     

Genetic dissection of Plasmodium falciparum blood infection levels and other complex traits related to human malaria infection

There is accumulating evidence of host genetic control in malaria infection and, in humans, some genes have been associated with severe malaria. Nevertheless, other important genes controlling blood infection levels, malarial disease and immune responses are likely to be identified. In this paper, we focus on segregation and linkage analyses of blood infection levels in an urban population living in Burkina Faso. We found evidence of a complex genetic control and a linkage to chromosome 5q31-q33. The identification of genes controlling complex traits related to malaria infection should be helpful in understanding protective mechanisms and the relationship between infection, malaria attacks and severe malaria.     

我国尖音库蚊复合组蚊虫的杂交及其与Wolbachia感染的关系

为了了解我国尖音库蚊复合组蚊虫间杂交卵的不孵化现象和明确该现象与共生微生物Wolbachia感染的关系,对该复合组实验室种群4个亚种进行了笼内杂交和抗生素处理后的杂交。试验表明: 在复合组蚊虫中骚扰库蚊Culex pipiens molestus与淡色库蚊Cx. Pipiens pallens、致倦库蚊Cx. Ipiens quinquefasciatus与尖音库蚊Cx. Pipiens pipiens之间存在有单向胞质不融合现象,骚扰库蚊的雄虫与尖音库蚊、致倦库蚊和淡色库蚊的雌虫杂交卵的孵化率分别为0.06%、0.46%和0.19%;该胞质不融合现象可以通过抗生素处理而消除,处理后骚扰库蚊雄虫与其余3个亚种雌虫F₃杂交卵的孵化率均有提高,分别为89.49%（t=3.90×10^-28＜t_0.01=2.704）、23.39%（t=9.15×10^-7＜t_0.01=2.660_）和22.27%（t=5.08×10^-4＜t_0.01=2.750）,并可因抗生素处理而产生新的不融合类型。     

Mislocalization of the MRN complex prevents ATR signaling during adenovirus infection

The protein kinases ataxia‐telangiectasia mutated (ATM) and ATM‐Rad3 related (ATR) are activated in response to DNA damage, genotoxic stress and virus infections. Here we show that during infection with wild‐type adenovirus, ATR and its cofactors RPA32, ATRIP and TopBP1 accumulate at viral replication centres, but there is minimal ATR activation. We show that the Mre11/Rad50/Nbs1 (MRN) complex is recruited to viral centres only during infection with adenoviruses lacking the early region E4 and ATR signaling is activated. This suggests a novel requirement for the MRN complex in ATR activation during virus infection, which is independent of Mre11 nuclease activity and recruitment of RPA/ATR/ATRIP/TopBP1. Unlike other damage scenarios, we found that ATM and ATR signaling are not dependent on each other during infection. We identify a region of the viral E4orf3 protein responsible for immobilization of the MRN complex and show that this prevents ATR signaling during adenovirus infection. We propose that immobilization of the MRN damage sensor by E4orf3 protein prevents recognition of viral genomes and blocks detrimental aspects of checkpoint signaling during virus infection.     

Effects of poliovirus infection on nucleo-cytoplasmic trafficking and nuclear pore complex composition

Infection of eukaryotic cells with lytic RNA viruses results in extensive interactions of viral gene products with macromolecular pathways of the host, ultimately leading to death of the infected cells. We show here that infection of cells with poliovirus results in the cytoplasmic accumulation of a variety of shuttling and non-shuttling nuclear proteins that use multiple nuclear import pathways. In vitro nuclear import assays using semi-permeabilized infected cells confirmed that nuclear import was blocked and demonstrated that docking of nuclear import receptor-cargo complexes at the cytoplasmic face of the nuclear pore complex (NPC) was prevented. Analysis of components of the NPC revealed that two proteins, Nup153 and p62, were proteolyzed during poliovirus infection. These results suggest that the cytoplasmic relocalization of numerous cellular proteins is caused by the inhibition of multiple nuclear import pathways via alterations in NPC composition in poliovirus-infected cells. Blocking of nuclear import points to a novel strategy by which cytoplasmic RNA viruses can evade host immune defenses, by preventing signal transduction to the nucleus.     

Development of a mucosal complex vaccine against oral Salmonella infection in mice

We examined the immunogenicity of a Salmonella enterica complex vaccine (CV), consisting of flagellin and polysome purified from serotype Typhimurium LT2. CV plus cholera toxin (CT), in three oral doses given at 7-day intervals, conferred complete protection on C57BL/6 mice against lethal oral infection with a wild-type strain. It elicited mucosal IgA > IgG2a > IgG1 and systemic IgG2a > IgG1 > IgA antibodies to flagellin and polysome, and delayed footpad response (DFR) to both antigens. In Peyer's patches (PPs) and lamina propria (LP), IgA was produced under a Th1-dominant environment; CD4+T cells from produced interleukin (IL)-2, interferon (IFN)-gamma, and IL-10 by stimulation with salmonella extract. On the same protocol, flagellin plus CT induced flagellin-specific mucosal and systemic IgA and IgG1 antibodies, CD4+T cells producing IL-10 and IFN-gamma in PPs and LP, and only minimal levels of flagellin-specific DFR. Polysome plus CT induced polysome-specific mucosal and systemic IgG2a in addition to IgG1 and IgA antibodies, CD4+T cells producing IFN-gamma and IL-2 in PPs and LP, and polysome-specific DFR. These two vaccines, however, conferred at most 50-60% survival rates. Our results suggest that polysomes in CV provide effective adjuvant activity for the induction of both mucosal and systemic Th1-biased responses toward flagellin.     

Burkholderia cepacia complex infection in a cohort of Italian patients with cystic fibrosis

The aims of this study were to detect Burkholderia cepacia complex (Bcc) strains in a cohort of Cystic Fibrosis patients (n=276) and to characterize Bcc isolates by molecular techniques. The results showed that 11.23% of patients were infected by Bcc. Burkholderia cenocepacia lineage III-A was the most prevalent species (64.3%) and, of these, 10% was cblA positive and 50% esmR positive. Less than half of the strains were sensitive to ceftazidime, meropenem, piperacillin tazobactam, and trimethoprim-sulfamethoxazole. About half of the strains (41%) had homogeneous profiles, suggesting cross-transmission. The infection by B. cenocepacia was associated to a high rate of mortality (p=0.01).     

IL-2 complex treatment can protect naive mice from bacterial and viral infection

IL-2 complexes have substantial effects on the cellular immune system, and this approach is being explored for therapeutic application in infection and cancer. However, the impact of such treatments on subsequent encounter with pathogens has not been investigated. In this study, we report that naive mice treated with a short course of IL-2 complexes show enhanced protection from newly encountered bacterial and viral infections. IL-2 complex treatment expands both the NK and CD8 memory cell pool, including a recently described population of preexisting memory-phenotype T cells responsive to previously unencountered foreign Ags. Surprisingly, prolonged IL-2 complex treatment decreased CD8 T cell function and protective immunity. These data reveal the impact of cytokine complex treatment on the primary response to infection.     

Splenic macrophage function in early syphilitic infection is complex. Stimulation versus down-regulation

Macrophages are important regulatory cells that can both stimulate and down-regulate various immune functions. During syphilitic infection, these cells phagocytize, kill, and lyse Treponema pallidum. They also modulate early T cell activation by decreasing IL-2 production through secretion of PG. This report focuses on additional complexities of macrophage regulation. Non-adherent splenic cells were stimulated with Con A to induce IFN-gamma synthesis. High levels were detected in preparations from normal rabbits and much lower levels in preparations from infected rabbits. The organisms also readily stimulated IL-1 synthesis by adherent spleen preparations from normal but not from infected rabbits. When indomethacin was added to these latter preparations, this IL-1 defect was reversed, implicating PG in this down-regulation. Spleen cells were obtained from normal rabbits and from rabbits infected testicularly for 9 to 12 days. Infection elevated basal levels of class II Ia Ag on adherent cells. In addition, macrophage Ia expression was increased during 4 days of in vitro incubation with treponemes. Non-adherent spleen cells from infected animals inhibited two different macrophage functions. First, culture filtrates obtained after 48 h of incubation contained a soluble factor that subsequently decreased LPS-induced IL-1 synthesis. Second, when macrophages were co-incubated with non-adherent cells, treponemal stimulation of macrophage Ia expression was inhibited; this inhibition was reversed by indomethacin implicating prostaglandins in this down-regulation. In further experiments an exogenous source of IFN-gamma was incubated with adherent cells from infected rabbits. This stimulated macrophage function as shown by increased IL-1 synthesis and Ia expression and decreased PGE2 secretion. Results are discussed in terms of the complexities of immunoregulation by macrophages during syphilitic infection.     

Wolbachia infection in the Loxoblemmus complex (Orthoptera: Gryllidae) in Korea

The Wolbachia bacterium is one of the most prevalent intracellular symbionts of invertebrates, particularly insects. This bacterium induces four distinct reproductive anomalies such as cytoplasmic incompatibility, feminization, male killing, and parthenogenesis of its hosts. Here we report that three closely related cricket species, Loxoblemmus doenitzi, L. campestris, and L. equestris can become infected with Wolbachia. Based on the 16s rRNA sequences, all three species were single infections. However, Wolbachia infecting L. campestris showed diverse Wolbachia surface protein gene sequences resembling multiple infections. In addition, all Wolbachia strains in the three host species harbored the Wolbachia specific bacteriophage.     

Parasite survey of a Daphnia hybrid complex: host-specificity and environment determine infection

1. Hybridization between species is a common phenomenon in plants and animals. If parasite prevalence differs for hybrids and parental species (i.e. taxa) there may be considerable consequences for relative hybrid fitness. Some studies have investigated hybrid complexes for infection, and complex-specific differences in parasite prevalence have been detected. 2. Based on the results of a field study on a hybridizing Daphnia population from a single lake, it has been hypothesized that permanently over- or under-infected hybrids do not exist. The observed field-patterns can only be temporal because taxa, in addition to single genotypes, might be the subject of parasite driven host frequency-dependent selection. Thus, parasites will track any common taxon within a hybrid complex. 3. In the present study, hybridizing Daphnia populations from 43 lakes were screened for parasite infections to obtain indirect evidence for coevolutionary cycles. It was hypothesized that, due to time lags between the evolution of resistance in host populations and the evolution of the parasite towards tracking of a common host taxon, the same Daphnia taxon will be over-infected in some lakes, while being under-infected in others. 4. Two of the four parasite species were specialists: their prevalence differed among coexisting Daphnia taxa. The varying infection patterns detected across spatially segregated hybridizing Daphnia populations are consistent with theoretical predictions for coevolutionary cycles. Thus the infection patterns, as observed under natural conditions, are temporal and unstable. 5. Additionally, the spatial distribution of the four parasite species was analysed with respect to habitat differences. The results show that the presence of a particular parasite on a host taxon was determined not only by the host-specificity of the parasite, but also by host-habitat relations.     

NK gene complex and chromosome 19 loci enhance MHC resistance to murine cytomegalovirus infection

An H-2^k MHC locus is critical for murine cytomegalovirus (MCMV) resistance in MA/My mice and virus control is abolished if H-2^k is replaced with H-2^b MHC genes from MCMV-susceptible C57L mice. Yet, H-2^k resistance varies with genetic background; thus, modifiers of virus resistance must exist. To identify non-MHC resistance loci, spleen and liver MCMV levels and genome-wide genotypes were assessed in (C57L × MA/My) and (MA/My × C57L) F₂ offspring (representing 550 meioses). Significantly, a non-Mendelian frequency of MHC genotypes was observed for offspring of the latter cross. Quantitative trait loci (QTL) and their interaction potential in MCMV resistance were assessed in R/qtl; QTL on chromosomes 17, 6, and 19 affected MCMV levels in infected animals. A chromosome 6 QTL was linked with the NK gene complex and acted in an additive fashion with an H-2^k MHC QTL to mitigate spleen MCMV levels. We provide biological confirmation that this chromosome 6 QTL provided MCMV control independent of H-2^k via NK cells. Importantly, both chromosome 6 and 19 QTLs contribute to virus control independent of H-2^k. Altogether, MHC and non-MHC MCMV-resistance QTL contribute in early resistance to MCMV infection in this genetic system.     

Chlamydia pneumoniae infection alters the junctional complex proteins of human brain microvascular endothelial cells

Chlamydia pneumoniae has been identified and associated with multiple sclerosis (MS) and Alzheimer's disease (AD) pathogenesis, although the relationship of this organism in these diseases remains controversial. We have hypothesized that one potential avenue of infection is through the junctional complexes between the blood-brain barrier (BBB) endothelia. C. pneumoniae is characteristically a respiratory pathogen, but has been implicated in atherosclerosis, coronary artery disease, and neuroinflammatory conditions. C. pneumoniae infection may lead to endothelial damage, junctional alterations, and BBB breakdown. Therefore, in this study, C. pneumoniae infection of human brain microvascular endothelial cells (HBMECs) resulted in increased expression of the zonula adherens proteins beta-catenin, N-cadherin, and VE-cadherin, and decreased expression of the tight junctional protein occludin, as determined by immunocytochemistry and Western blot analyses. These events may underlie a mechanism for the regulation of paracellular permeability while maintaining barrier integrity during C. pneumoniae infection associated with neuropathologies such as MS and AD.     

Influence of H-2 complex on susceptibility to infection by murine leukemia virus.

Titers of infectious ecotropic MuLV in mouse spleen were examined after deliberate infection. In congenic mice differing only in H-2 haplotype, a gene (or genes) within the H-2 complex determined either a high virus titer (H-2k, H-2d, H-2a) or a low titer (H-2b, H-2q). Susceptibility to high virus titers was inherited as a dominant trait. Kinetic studies revealed similar initial patterns of infection in both groups, with a fall in titer in the "resistant" strain occurring from week 6 through 10 after infection. Anti-VEA antibody titers differed significantly between the groups, but no mechanistic role for antibody in eliminating virus was apparent. Genes outside the H-2 complex were shown to influence MuLV titers after infection as well.