Immunosuppressed Hosts Research Articles

Airborne acquisition of Pneumocystis in bronchoscopy units: a hidden danger to healthcare workers.

The possible presence of Pneumocystis in a bronchoscopy unit of a tertiary-hospital was examined by detecting Pneumocystis-specific DNA by polymerase chain reaction in prospectively obtained samples of oropharyngeal wash from seven healthcare workers (HCWs) and air from three areas of the unit at different time points (baseline, days +15,+30,+60,+90 after initiation of the study). Positive samples were genotyped at two genetic loci: the mitochondrial large subunit ribosomal RNA (mtLSUrRNA) fragment by direct sequencing and the gene for dihydropteroate synthase (DHPS) by restriction fragment-length polymorphism. Pneumocystis DNA was identified in 13/24 samples from HCWs, in 4/14 air samples and also in two patients with Pneumocystis pneumonia (PcP) and another with a Pneumocystis-associated disease subjected to bronchoscopy on days +15 and +60 after initiation of the study. The HCWs harbored a high rate of mtLSU-rRNA genotypes 1 and 3 and samples from air and patients with only genotype 3. DHPS mutations related to sulpha resistance were detected in three samples from HCWs and in one from air; 65% of the positive samples showed genotypic concordance. The study demonstrates that HCWs of bronchoscopy units represent a new dynamic reservoir and a possible source of infection for human Pneumocystis species, including DHPS genotypes related to sulpha resistance that could be transmitted within hospitals to immunosuppressed hosts in whom a PcP can develop. The results provide the first evidence of the risk of Pneumocystis transmission in the bronchoscopy units and arguments to improve prevention and control of this infection in nosocomial setting.

When the Good Becomes the Bad: A Case of Lactobacillus rhamnosus Septicemia Unrelated to Probiotic Use

Introduction:Lactobacilli are gram positive, facultative anaerobic bacilli that live as commensals in the gastrointestinal and genitourinary tracts. They are promoted as probiotics. Although they are considered non-pathogenic, there are case reports of Lactobacillus-related serious infections in immunosuppressed hosts - mostly associated with probiotics use. We present a case of Lactobacillus septicemia unrelated to probiotic use. Case Description: A 64-year old male presented with complaints of jaundice and an unintentional 40 pounds weight loss. Physical exam revealed a cachectic male with whole-body jaundice and scleral icterus with epigastric tenderness. The patient and family denied any probiotic use. Laboratory tests suggested an obstructive jaundice. CT-abdomen revealed a mass in the head of the pancreas with intra and extra hepatic biliary dilatation. He underwent ERCP followed by percutaneous biliary drainage. His post-operative course was further complicated by sepsis due to fungemia. While on Micafungin (and having completed a course of Meropenem and Vancomycin, empirically for cholangitis), his sepsis remained unresolved. Repeat blood cultures grew Lactobacillus Rhamnosus (4 sets) with resistance to Vancomycin (MIC1:256). In view of multiple comorbidities and recent antibiotic use, he was treated with Daptomycin and repeat cultures after 72 hours were negative with improvement in his sepsis.Conclusions:It was hypothesized that the recent instrumentation along with the tumor eroding the vessels and ductal system of the pancreas resulted in the translocation of Lactobacillus into the bloodstream. This case recognizes Lactobacillus as a potential pathogen and that blood cultures with susceptibility testing are important in guiding treatment.

Strongyloides Enteritis and Hyperinfection in an Immunosuppressed Host

Strongyloides Enteritis and Hyperinfection in an Immunosuppressed Host

Strongyloides Infection in Immunocompetent Patient With New Onset Cirrhosis

Infection with Strongyloides is a rarely reported infection in industrialized nations; usually only found in immunocompromised patients. We present a case of a 36 year-old Hispanic male with new onset cirrhosis found to have a Strongyloides infection. He presented with jaundice, abdominal swelling and lower extremity edema. He had moved to Shreveport, LA from Mexico 3 years prior to admission. Patient had no prior medical history. He took no medications, but did drink six beers daily. Patient was found to have a hemoglobin of 4.0 g/dL, WBC of 20,410/uL with eosinophilia, Total Bilirubin 3.3 mg/dL (direct bilirubin 2.1 mg/dL), AST/ALT 66/40 U/L, ALP 402, Iron/TIBC/T-sat 12/243/5%, urine drug screen was cocaine positive, Hepatitis panel, HIV, RPR were negative. Interestingly, ANA and anti-RNP antibodies were positive. IgG was elevated at 1,950 mg/dL. Anti-smooth muscle antibody was elevated at 26 units and anti-mitochondrial antibody was equivocal at 20.4 units. US of the abdomen showed cirrhotic changes of the liver and ascites without biliary dilation. Paracentesis was negative for infection and SAAG >1.1. EGD was performed and showed esophageal and gastric varies. Patient was transfused with packed red blood cells and started on spironolactone, furosemide and propranolol. He clinically improved and was discharged with close follow up for EGD and colonoscopy. After patient was discharged, the result of the serum Strongyloides IgG antibody test returned positive. Strongyloidiasis is more common in tropical regions, but it has an estimated prevalence of up to 1.2-4.9% in the US. Symptoms can range from asymptomatic with mild eosinophilia to disseminated disease in an immunosuppressed host. Most commonly infected individuals live in endemic rural areas and are asymptomatic. Diagnosis can be made either by detecting rhabditiform larvae in the stool or by serologic as in our patient. Treatment includes 2 day course of ivermectin or up to 7 days for disseminated disease. Our patient appears to have an underlying autoimmune disease process, which is unclear. His elevated ALP and elevations in Anti-smooth muscle antibody and Anti-mitochondrial antibody raise concern for autoimmune hepatitis. In literature, AIH shows an inverse relationship with development of Strongyloides infection. However, our patient also consumed alcohol which does correlate with increased incidence of Strongyloides infection.

Changes in the immune system in experimental acanthamoebiasis in immunocompetent and immunosuppressed hosts

BackgroundAcanthamoebiasis is most often found in patients with immune deficiency, with infections facilitated by the intake of immunosuppressive drugs. The host immune response to Acanthamoeba spp. infection is poorly understood. Thus, in this study, we aimed to examine the course of Acanthamoeba spp. infection taking into account the host’s immunological status, including assessment of the hematological parameters, cytokine analysis, immunophenotypic changes in spleen populations, and histological spleen changes, which could help clarify some aspects of the immune response to acanthamoebiasis. In our experimental study, we used Acanthamoeba strain AM 22 isolated from the bronchoaspirate of a patient with acute myeloid leukaemia (AML) and atypical pneumonia symptoms.ResultsAcanthamoeba spp. affected the hematological parameters in immunocompetent and immunosuppressed mice and induced a change in spleen weight during infection. Moreover, analysis of anti-inflammatory (IL-4 and IL-10) and pro-inflammatory (IL-17A and IFN-γ) cytokines produced by splenocytes stimulated with concanavalin A demonstrated that Acanthamoeba spp. induced a selective Th1, Th2 and Th17 response at later stages of the infection in immunocompetent hosts. In the case of hosts with low immunity, Acanthamoeba elicited robust Th1 cell-mediated immunity without the participation of Th17. We observed suppression of CD8+ and CD4+ T lymphocytes and CD3+CD4-CD8- double-negative (DN) T lymphocyte populations in the beginning, and in the case of CD3+/CD4+/CD8+ double-positive (DP) T cells in the final phase of Acanthamoeba spp. infection in hosts with low immunity. Also, CD4+T lymphocytes and CD3+/CD4+ and CD3+/CD8+ lymphocyte counts during each stage of acanthamoebiasis were shown to be upregulated.ConclusionsWe demonstrated that analysis of the immune response and pathogenesis mechanisms of clinical isolates of Acanthamoeba spp. in an animal model not only has purely cognitive significance but above all, may help in the development of effective methods of pharmacological therapy especially in patients with low immunity.

Intrinsic Programming of Alveolar Macrophages for Protective Antifungal Innate Immunity Against Pneumocystis Infection.

Invasive fungal infections, including Pneumocystis Pneumonia (PcP), remain frequent life-threatening conditions of patients with adaptive immune defects. While innate immunity helps control pathogen growth early during infection, it is typically not sufficient for complete protection against Pneumocystis and other human fungal pathogens. Alveolar macrophages (AM) possess pattern recognition molecules capable of recognizing antigenic and structural determinants of Pneumocystis. However, this pathogen effectively evades innate immunity to infect both immunocompetent and immunosuppressed hosts, albeit with differing outcomes. During our studies of mouse models of PcP, the FVB/N strain was identified as unique because of its ability to mount a protective innate immune response against Pneumocystis infection. In contrast to other immunocompetent strains, which become transiently infected prior to the onset of adaptive immunity, FVB/N mice rapidly eradicated Pneumocystis before an adaptive immune response was triggered. Furthermore, FVB/N mice remained highly resistant to infection even in the absence of functional T cells. The effector mechanism of innate protection required the action of functional alveolar macrophages, and the adoptive transfer of resistant FVB/N AMs, but not susceptible CB.17 AMs, conferred protection to immunodeficient mice. Macrophage IFNγ receptor signaling was not required for innate resistance, and FVB/N macrophages were found to display markers of alternative activation. IFNγ reprogrammed resistant FVB/N macrophages to a permissive M1 biased phenotype through a mechanism that required direct activation of the macrophage IFNγR. These results demonstrate that appropriately programmed macrophages provide protective innate immunity against this opportunistic fungal pathogen, and suggest that modulating macrophage function may represent a feasible therapeutic strategy to enhance antifungal host defense. The identification of resistant and susceptible macrophages provides a novel platform to study not only the mechanisms of macrophage-mediated antifungal defense, but also the mechanisms by which Pneumocystis evades innate immunity.

Nematobacterial Complexes and Insect Hosts: Different Weapons for the Same War.

Entomopathogenic nematodes (EPNs) are widely used as biological control agents against insect pests, the efficacy of these organisms strongly depends on the balance between the parasitic strategies and the immune response of the host. This review summarizes roles and relationships between insect hosts and two well-known EPN species, Steinernema feltiae and Steinernema carpocapsae and outlines the main mechanisms of immune recognition and defense of insects. Analyzing information and findings about these EPNs, it is clear that these two species use shared immunosuppression strategies, mainly mediated by their symbiotic bacteria, but there are differences in both the mechanism of evasion and interference of the two nematodes with the insect host immune pathways. Based on published data, S. feltiae takes advantage of the cross reaction between its body surface and some host functional proteins, to inhibit defensive processes; otherwise, secretion/excretion products from S. carpocapsae seem to be the main nematode components responsible for the host immunosuppression.

Relationship between antioxidant defense in Acanthamoeba spp. infected lungs and host immunological status

The role of oxidative stress in the pathogenicity of acanthamoebiasis is an important aspect of the intricate and complex host–parasite relationship. The aim of this experimental study was to determine oxidative stress through the assessment of lipid peroxidation product (LPO) levels and antioxidant defense mechanism in Acanthamoeba spp. lung infections in immunocompetent and immunosuppressed hosts. In Acanthamoeba spp. infected immunocompetent mice we noted a significant increase in lung lipid peroxidation products (LPO) at 8 days and 16 days post infection (dpi). There was a significant upregulation in lung LPO in immunocompetent and immunosuppressed mice infected by Acanthamoeba spp. at 16 dpi. The superoxide dismutase activity decreased significantly in lungs in immunosuppressed mice at 8 dpi. The catalase activity was significantly upregulated in lungs in immunocompetent vs. immunosuppressed group and in immunocompetent vs. control mice at 16 dpi. The glutathione reductase activity was significantly lower in immunosuppressed group vs. immunosuppressed control at 24 dpi. We found significant glutathione peroxidase downregulation in immunocompetent and immunosuppressed groups vs. controls at 8 dpi, and in immunosuppressed vs. immunosuppressed control at 16 dpi. The consequence of the inflammatory response in immunocompetent and immunosuppressed hosts in the course of experimental Acanthamoeba spp. infection was the reduction of the antioxidant capacity of the lungs resulting from changes in the activity of antioxidant enzymes. Therefore, the imbalance between oxidant and antioxidant processes may play a major role in pathology associated with Acanthamoeba pneumonia.

Viral Anti-CRISPR Tactics: No Success without Sacrifice

Co-evolution with their bacterial hosts has led to viral countermeasures against CRISPR-mediated immunity. In a recent issue of Cell, Landsberger etal. (2018) and Borges etal. (2018) report that cooperation among bacteriophages and multiple infection events are necessary to overcome CRISPR immune responses.

Suppressor of Cytokine Signaling 1 (SOCS1) and SOCS3 Are Stimulated within the Eye during Experimental Murine Cytomegalovirus Retinitis in Mice with Retrovirus-Induced Immunosuppression.

AIDS-related human cytomegalovirus retinitis remains the leading cause of blindness among untreated HIV/AIDS patients worldwide. To study mechanisms of this disease, we used a clinically relevant animal model of murine cytomegalovirus (MCMV) retinitis with retrovirus-induced murine AIDS (MAIDS) that mimics the progression of AIDS in humans. We found in this model that MCMV infection significantly stimulates ocular suppressor of cytokine signaling 1 (SOCS1) and SOCS3, host proteins which hinder immune-related signaling by cytokines, including antiviral type I and type II interferons. The present study demonstrates that in the absence of retinal disease, systemic MCMV infection of mice without MAIDS, but not in mice with MAIDS, leads to mild stimulation of splenic SOCS1 mRNA. In sharp contrast, when MCMV is directly inoculated into the eyes of retinitis-susceptible MAIDS mice, high levels of intraocular SOCS1 and SOCS3 mRNA and protein are produced which are associated with significant intraocular upregulation of gamma interferon (IFN-γ) and interleukin-6 (IL-6) mRNA expression. We also show that infiltrating macrophages, granulocytes, and resident retinal cells are sources of intraocular SOCS1 and SOCS3 protein production during development of MAIDS-related MCMV retinitis, and SOCS1 and SOCS3 mRNA transcripts are detected in retinal areas histologically characteristic of MCMV retinitis. Furthermore, SOCS1 and SOCS3 are found in both MCMV-infected cells and uninfected cells, suggesting that these SOCS proteins are stimulated via a bystander mechanism during MCMV retinitis. Taken together, our findings suggest a role for MCMV-related stimulation of SOCS1 and SOCS3 in the progression of retinal disease during ocular, but not systemic, MCMV infection.IMPORTANCE Cytomegalovirus infection frequently causes blindness in untreated HIV/AIDS patients. This virus manipulates host cells to dysregulate immune functions and drive disease. Here, we use an animal model of this disease to demonstrate that cytomegalovirus infection within eyes during retinitis causes massive upregulation of immunosuppressive host proteins called SOCS. As viral overexpression of SOCS proteins exacerbates infection with other viruses, they may also enhance cytomegalovirus infection. Alternatively, the immunosuppressive effect of SOCS proteins may be protective against immunopathology during cytomegalovirus retinitis, and in such a case SOCS mimetics or overexpression treatment strategies might be used to combat this disease. The results of this work therefore provide crucial basic knowledge that contributes to our understanding of the mechanisms of AIDS-related cytomegalovirus retinitis and, together with future studies, may contribute to the development of novel therapeutic targets that could improve the treatment or management of this sight-threatening disease.

Microencapsulated adult porcine islets transplanted intraperitoneally in streptozotocin‐diabetic non‐human primates

Xenogeneic donors would provide an unlimited source of islets for the treatment of type 1 diabetes (T1D). The goal of this study was to assess the function of microencapsulated adult porcine islets (APIs) transplanted ip in streptozotocin (STZ)-diabetic non-human primates (NHPs) given targeted immunosuppression. APIs were encapsulated in: (a) single barium-gelled alginate capsules or (b) double alginate capsules with an inner, islet-containing compartment and a durable, biocompatible outer alginate layer. Immunosuppressed, streptozotocin-diabetic NHPs were transplanted ip with encapsulated APIs, and graft function was monitored by measuring blood glucose, %HbA1c, and porcine C-peptide. At graft failure, explanted capsules were assessed for biocompatibility and durability plus islet viability and functionality. Host immune responses were evaluated by phenotyping peritoneal cell populations, quantitation of peritoneal cytokines and chemokines, and measurement of anti-porcine IgG and IgM plus anti-Gal IgG. NHP recipients had reduced hyperglycemia, decreased exogenous insulin requirements, and lower percent hemoglobin A1c (%HbA1c) levels. Porcine C-peptide was detected in plasma of all recipients, but these levels diminished with time. However, relatively high levels of porcine C-peptide were detected locally in the peritoneal graft site of some recipients at sacrifice. IV glucose tolerance tests demonstrated metabolic function, but the grafts eventually failed in all diabetic NHPs regardless of the type of encapsulation or the host immunosuppression regimen. Explanted microcapsules were intact, "clean," and free-floating without evidence of fibrosis at graft failure, and some reversed diabetes when re-implanted ip in diabetic immunoincompetent mice. Histology of explanted capsules showed scant evidence of a host cellular response, and viable islets could be found. Flow cytometric analyses of peritoneal cells and peripheral blood showed similarly minimal evidence of a host immune response. Preformed anti-porcine IgG and IgM antibodies were present in recipient plasma, but these levels did not rise post-transplant. Peritoneal graft site cytokine or chemokine levels were equivalent to normal controls, with the exception of minimal elevation observed for IL-6 or IL-1β, GRO-α, I-309, IP-10, and MCP-1. However, we found central necrosis in many of the encapsulated islets after graft failure, and explanted islets expressed endogenous markers of hypoxia (HIF-1α, osteopontin, and GLUT-1), suggesting a role for non-immunologic factors, likely hypoxia, in graft failure. With donor xenoislet microencapsulation and host immunosuppression, APIs corrected hyperglycemia after ip transplantation in STZ-diabetic NHPs in the short term. The islet xenografts lost efficacy gradually, but at graft failure, some viable islets remained, substantial porcine C-peptide was detected in the peritoneal graft site, and there was very little evidence of a host immune response. We postulate that chronic effects of non-immunologic factors, such as in vivo hypoxic and hyperglycemic conditions, damaged the encapsulated islet xenografts. To achieve long-term function, new approaches must be developed to prevent this damage, for example, by increasing the oxygen supply to microencapsulated islets in the ip space.

Eicosanoid mediation of immune responses at early bacterial infection stage and its inhibition by Photorhabdus temperata subsp. temperata, an entomopathogenic bacterium

An entomopathogenic bacterium Photorhabdus temperata subsp. temperata (Ptt) infects insect hemocoel by the vectoring activity of its symbiotic nematode, Heterorhabditis megidis. The bacterium induces host immunosuppression by inhibiting eicosanoid biosynthesis. This study investigated the role of eicosanoids in immune responses of the beet armyworm, Spodoptera exigua, in the early bacterial infection stage (first 3 hr postinfection [PI]). After infection with the nonpathogenic Escherichia coli (Ec), the bacterium maintained its population for the first 3 hr PI, then rapidly decreased in numbers. During the 3 hr PI of Ptt, this pathogenic bacterium also did not show any significant change in bacterial population. However, Ptt rapidly increased its population size after the initial lag phase, inducing fatal septicemia. This study further analyzed cellular and humoral immune responses of the beet armyworm during the initial 3 hr PI. During this early stage, challenge with Ec stimulated hemocyte-spreading behavior along with extensive F-actin growth. However, Ptt infection suppressed hemocyte spreading. Expression levels of three antimicrobial peptides (lysozyme, gloverin, and gallerimycin) were significantly inhibited during Ptt infection. Phospholipase A2 activity was significantly induced during the early infection stage of Ec, but not during Ptt infection. Addition of eicosanoid biosynthesis inhibitors significantly reversed the initial immunosuppression. These results suggest that, during the early infection stage, Ptt can shutdown eicosanoid biosynthesis which can prevent acute immune responses of host insects.

Coronavirus and Chronic Lung Allograft Dysfunction: Hiding in Plain Sight?

Coronavirus and Chronic Lung Allograft Dysfunction: Hiding in Plain Sight?

The Murine Polyomavirus MicroRNA Locus Is Required To Promote Viruria during the Acute Phase of Infection.

Polyomaviruses (PyVs) can cause serious disease in immunosuppressed hosts. Several pathogenic PyVs encode microRNAs (miRNAs), small RNAs that regulate gene expression via RNA silencing. Despite recent advances in understanding the activities of PyV miRNAs, the biological functions of PyV miRNAs during in vivo infections are mostly unknown. The studies presented here used murine polyomavirus (MuPyV) as a model to assess the roles of the PyV miRNAs in a natural host. This analysis revealed that a MuPyV mutant that is unable to express miRNAs has enhanced viral DNA loads in select tissues at late times after infection. This is consistent with the PyV miRNAs functioning to reduce viral replication during the persistent phase of infection in a natural host. Additionally, the MuPyV miRNA locus promotes viruria during the acute phase of infection as evidenced by a defect in shedding during infection with the miRNA mutant virus. The viruria defect of the miRNA mutant virus could be rescued by infecting Rag2-/- mice. These findings implicate the miRNA locus as functioning in both the persistent and acute phases of infection and suggest a role for MuPyV miRNA in evading the adaptive immune response.IMPORTANCE MicroRNAs are expressed by diverse viruses, but for only a few is there any understanding of their in vivo function. PyVs can cause serious disease in immunocompromised hosts. Therefore, increased knowledge of how these viruses interact with the immune response is of clinical relevance. Here we show a novel activity for a viral miRNA locus in promoting virus shedding. This work indicates that in addition to any role for the PyV miRNA locus in long-term persistence, it also has biological activity during the acute phase. As this mutant phenotype is alleviated by infection of mice lacking an adaptive immune response, our work also connects the in vivo activity of the PyV miRNA locus to the immune response. Given that PyV-associated disease is associated with alterations in the immune response, our findings help to better understand how the balance between PyVs and the immune response becomes altered in pathogenic states.

Greater wax moth Galleria mellonella (Lepidoptera: Pyralidae) as a resistant model host for Nosema pyrausta (Microsporidia: Nosematidae).

Galleria mellonella fed 3 million Nosema pyrausta spores per larva showed 0 and 5% infestation rate at 30 °C and 24 °C, respectively. N. pyrausta virulence did not increase after passage through G. mellonella for three generations. When larvae were pretreated with phenylthiourea, Bacillus thuringiensis or combination of both, infection rates were 11%, 15% and 22%, respectively. Injection of untreated and potassium hydroxide-primed spores resulted in approximately 10% and 50% infection, respectively. G. mellonella is resistant to high dosages of N. pyrausta spores, serving as a prospective model of insect resistance to microsporidia, while host immunosuppression and/or spore activation increases success of the pathogen.

Imipenem and normal saline with cyclophosphamide have positive effects on the intestinal barrier in rats with sepsis.

Sepsis is a life-threatening organ dysfunction caused the dysregulation of host inflammatory response and immunosuppression to infection Early recognition and intervention are hence of paramount importance. In this respect the "sepsis bundle" was proposed in 2004 to be instituted in cases of suspected sepsis. We hypothesised that a combination treatment of the sepsis bundle with cyclophosphamide would improve the function of the intestinal mucosa and enhance survival in rats with induced sepsis. Sprague-Dawley rats were divided into 5 different groups: sham, cecal ligation and puncture (CLP), cyclophosphamide (CTX), imipenem+normal saline (NS) and imipenem+NS+CTX. Cecal ligation and puncture were used for inducing the polymicrobial sepsis. Western-blot was used to measure the occludin protein, and ELISA for examining the plasma level of cytokines IL-6, IL-10 and TNF-α. TUNEL assay for testing the intestinal mucosal apoptosis, and hematoxylin-eosin staining for observing the intestinal mucosal changes. The permeability of intestinal mucosa was determined by the plasma level of FD-70. The results showed that the combination treatment of the sepsis bundle with cyclophosphamide attenuated cytokine levels, inhibited epithelial cell apoptosis and improved the function of the intestinal barrier. The survival rate of the group treated with the combined therapy was significantly higher than that of the other groups. The combination treatment of sepsis bundle with cyclophosphamide improves the function of the intestinal barrier and enhances survival in septic rats.

Oncolytic Reovirus Inhibits Immunosuppressive Activity of Myeloid-Derived Suppressor Cells in a TLR3-Dependent Manner.

Oncolytic reovirus, which possesses 10 segments of dsRNA genome, mediates antitumor effects via not only virus replication in a tumor cell-specific manner, but also activation of antitumor immunity; however, the mechanism(s) of reovirus-induced activation of antitumor immunity have not been fully elucidated. Recent studies have demonstrated that overcoming an immunosuppressive environment in tumor-bearing hosts is important to achieve efficient activation of antitumor immunity. Among the various types of cells involved in immunosuppression, it has been revealed that myeloid-derived suppressor cells (MDSCs) are significantly increased in tumor-bearing hosts and play crucial roles in the immunosuppression in tumor-bearing hosts. In this study, we examined whether reovirus inhibits the immunosuppressive activity of MDSCs, resulting in efficient activation of immune cells after in vivo administration. The results showed that splenic MDSCs recovered from PBS-treated tumor-bearing mice significantly suppressed the Ag-specific proliferation of CD8+ T cells. In contrast, the suppressive activity of MDSCs on T cell proliferation was significantly reduced after reovirus administration. Reovirus also inhibited the immunosuppressive activity of MDSCs in IFN-β promoter stimulator-1 knockout (KO) mice and in wild-type mice. In contrast, the immunosuppressive activity of MDSCs in TLR-3 KO mice was not significantly altered by reovirus treatment. The activation levels of CD4+ and CD8+ T cells were significantly lower in TLR3 KO mice than in wild-type mice after reovirus administration. These results indicate that reovirus inhibits the immunosuppressive activity of MDSCs in a TLR3, but not IFN-β promoter stimulator-1, signaling-dependent manner.

Coccidioidomycosis in selected immunosuppressed hosts.

After contracting coccidioidomycosis, persons with impaired cellular immunity are more likely than healthy persons to have severe infection, disseminated infection, and higher mortality rates. In this brief review, we summarize the clinical manifestations, diagnosis, treatment, and prevention of coccidioidomycosis in persons infected with human immunodeficiency virus (HIV), recipients of solid organ or hematopoietic stem cell transplants, and recipients of biologic response modifiers. Among individuals infected with HIV, a diagnosis of acquired immunodeficiency syndrome (AIDS) and a CD4 T-lymphocyte count <250 cells/μl were associated with more severe coccidioidomycosis, whereas less severe disease occurred among those with undetectable HIV-RNA and higher CD4 T-lymphocyte counts, indicating that controlled HIV viremia and improved cellular immune status are important in limiting disease. For transplant recipients whose immunosuppression typically peaks in the first 3 to 6 months and tapers thereafter, the greatest risk of acute coccidioidomycosis occurs 6 to 12 months after transplantation. Relapses of recent coccidioidomycosis may occur during ongoing immunosuppression when patients are not taking suppressive antifungal medication. Recipients of biologic agents, especially those that impair tumor necrosis factor α (TNF-α), may be at increased risk for poorly controlled coccidioidomycosis; however, the best way to prevent and treat such infections has yet to be defined.

Susceptibility of Primary Human Choroid Plexus Epithelial Cells and Meningeal Cells to Infection by JC Virus.

JC polyomavirus (JCPyV) establishes a lifelong persistence in roughly half the human population worldwide. The cells and tissues that harbor persistent virus in vivo are not known, but renal tubules and other urogenital epithelial cells are likely candidates as virus is shed in the urine of healthy individuals. In an immunosuppressed host, JCPyV can become reactivated and cause progressive multifocal leukoencephalopathy (PML), a fatal demyelinating disease of the central nervous system. Recent observations indicate that JCPyV may productively interact with cells in the choroid plexus and leptomeninges. To further study JCPyV infection in these cells, primary human choroid plexus epithelial cells and meningeal cells were challenged with virus, and their susceptibility to infection was compared to the human glial cell line, SVG-A. We found that JCPyV productively infects both choroid plexus epithelial cells and meningeal cells in vitro Competition with the soluble receptor fragment LSTc reduced virus infection in these cells. Treatment of cells with neuraminidase also inhibited both viral infection and binding. Treatment with the serotonin receptor antagonist, ritanserin, reduced infection in SVG-A and meningeal cells. We also compared the ability of wild-type and sialic acid-binding mutant pseudoviruses to transduce these cells. Wild-type pseudovirus readily transduced all three cell types, but pseudoviruses harboring mutations in the sialic acid-binding pocket of the virus failed to transduce the cells. These data establish a novel role for choroid plexus and meninges in harboring virus that likely contributes not only to meningoencephalopathies but also to PML.IMPORTANCE JCPyV infects greater than half the human population worldwide and causes central nervous system disease in patients with weakened immune systems. Several recent reports have found JCPyV in the choroid plexus and leptomeninges of patients with encephalitis. Due to their role in forming the blood-cerebrospinal fluid barrier, the choroid plexus and leptomeninges are also poised to play roles in virus invasion of brain parenchyma, where infection of macroglial cells leads to the development of progressive multifocal leukoencephalopathy, a severely debilitating and often fatal infection. In this paper we show for the first time that primary choroid plexus epithelial cells and meningeal cells are infected by JCPyV, lending support to the association of JCPyV with meningoencephalopathies. These data also suggest that JCPyV could use these cells as reservoirs for the subsequent invasion of brain parenchyma.

Functional and Expression Analyses of the Pneumocystis MAT Genes Suggest Obligate Sexuality through Primary Homothallism within Host Lungs.

ABSTRACTFungi of the genus Pneumocystis are obligate parasites that colonize mammals’ lungs and are host species specific. Pneumocystis jirovecii and Pneumocystis carinii infect, respectively, humans and rats. They can turn into opportunistic pathogens in immunosuppressed hosts, causing severe pneumonia. Their cell cycle is poorly known, mainly because of the absence of an established method of culture in vitro. It is thought to include both asexual and sexual phases. Comparative genomic analysis suggested that their mode of sexual reproduction is primary homothallism involving a single mating type (MAT) locus encompassing plus and minus genes (matMc, matMi, and matPi; Almeida et al., mBio 6:e02250-14, 2015). Thus, each strain would be capable of sexual reproduction alone (self-fertility). However, this is a working hypothesis derived from computational analyses that is, in addition, based on the genome sequences of single isolates. Here, we tested this hypothesis in the wet laboratory. The function of the P. jirovecii and P. carinii matMc genes was ascertained by restoration of sporulation in the corresponding mutant of fission yeast. Using PCR, we found the same single MAT locus in all P. jirovecii isolates and showed that all three MAT genes are often concomitantly expressed during pneumonia. Extensive homology searches did not identify other types of MAT transcription factors in the genomes or cis-acting motifs flanking the MAT locus that could have been involved in MAT switching or silencing. Our observations suggest that Pneumocystis sexuality through primary homothallism is obligate within host lungs to complete the cell cycle, i.e., produce asci necessary for airborne transmission to new hosts.