Late Phase Of Infection Research Articles

Activation of the autophagy pathway by Torovirus infection is irrelevant for virus replication.

Autophagy is a conserved eukaryotic process that mediates lysosomal degradation of cytoplasmic macromolecules and damaged organelles, also exerting an important role in the elimination of intracellular pathogens. Despite the antiviral role of autophagy, many studies suggest that some positive-stranded RNA viruses exploit this pathway to facilitate their own replication. In this study, we demonstrate that the equine torovirus Berne virus (BEV), the prototype member of the Torovirus genus (Coronaviridae Family, Nidovirales Order), induces autophagy at late times post-infection. Conversion of microtubule associated protein 1B light chain 3 (LC3) from cytosolic (LC3 I) to the membrane associated form (LC3 II), a canonical marker of autophagosome formation, is enhanced in BEV infected cells. However, neither autophagy induction, via starvation, nor pharmacological blockade significantly affect BEV replication. Similarly, BEV infection is not altered in autophagy deficient cells lacking either Beclin 1 or LC3B protein expression. Unexpectedly, the cargo receptor p62, a selective autophagy receptor, aggregates within the region where the BEV main protease (Mpro) localizes. This finding, coupled with observation that BEV replication also induces ER stress at the time when selective autophagy is taking place, suggests that the autophagy pathway is activated in response to the hefty accumulation of virus-encoded polypeptides during the late phase of BEV infection.

Identification and characterization of a novel group of natural anti-sense transcripts from RNA1.2 gene locus of human cytomegalovirus.

Background:Natural anti-sense transcripts (NATs), which are transcribed from the complementary DNA strand of annotated genes, exert regulatory function of gene expression. Increasing studies recognized anti-sense transcription widespread throughout human cytomegalovirus (HCMV) genome, whereas the anti-sense transcription of RNA1.2 gene locus has never been investigated. In this study, the transcription of the RNA1.2 anti-sense strand was investigated in clinically isolated HCMV strain.Methods:Strand-specific high-through RNA-sequencing (RNA-seq) was performed to find possible anti-sense transcripts (ASTs). For analyzing and visualization of RNA-seq data sets, Integrative Genomics Viewer software was applied. To confirm these possibilities, Northern blotting and rapid amplification of cDNA ends (RACE) were used.Results:Transcription of the opposite strand of RNA1.2 gene locus was detected by RNA-sequencing using RNAs extracted from human embryonic lung fibroblasts infected with HCMV clinical isolate HAN. At least three HCMV NATs, named RNA1.2 AST 1, RNA1.2 AST2, and RNA1.2 AST3, were characterized by Northern blotting and RACE analyses. These RNA1.2 ASTs orientated from the complementary strand of RNA1.2 locus during the late phase of HCMV infection. The 5′- and 3′-termini of these transcripts were located within the opposite sequence of the predicted RNA1.2 gene.Conclusion:A cluster of novel NATs was transcribed from the opposite sequence of the HCMV RNA1.2 gene region.

Membrane metalloprotease TRABD2A restricts HIV-1 progeny production in resting CD4+ T cells by degrading viral Gag polyprotein.

Resting CD4+ T cells are highly resistant to the production of human immunodeficiency virus type 1 (HIV-1). However, the mechanism by which resting CD4+ T cells restrict such production in the late viral replication phase of infection has remained unclear. In this study, we found that the cell membrane metalloprotease TRAB domain-containing protein 2A (TRABD2A) inhibited this production in resting CD4+ T cells by degrading the virion structural precursor polyprotein Gag at the plasma membrane. Depletion or inhibition of metalloprotease activity by TRABD2A profoundly enhanced HIV-1 production in resting CD4+ T cells. TRABD2A expression was much higher in resting CD4+ T cells than in activated CD4+ T cells and was considerably reduced by T cell activation. Moreover, reexpressing TRABD2A reinforced the resistance of activated CD4+ T cells to the production of HIV-1 progeny. Collectively, these results elucidate the molecular mechanism employed by resting CD4+ T cells to potently restrict the assembly and production of HIV-1 progeny.

Crosstalk of PD-1 signaling with the SIRT1/FOXO-1 axis during the progression of visceral leishmaniasis.

Previously, we documented the role of the programmed death-1 (PD-1, also known as PDCD1) pathway in macrophage apoptosis and the downregulation of this signaling during infection by the intra-macrophage parasite Leishmania donovani However, we also found that, during the late phase of infection, PD-1 expression was significantly increased without activating host cell apoptosis; here we show that inhibition of PD-1 led to markedly decreased parasite survival, along with increased production of TNFα, IL-12, reactive oxygen species (ROS) and nitric oxide (NO). Increased PD-1 led to inactivation of AKT proteins resulting in nuclear sequestration of FOXO-1. Transfecting infected cells with constitutively active FOXO-1 (CA-FOXO) led to increased cell death, thereby suggesting that nuclear FOXO-1 might be inactivated. Infection significantly induced the expression of SIRT1, which inactivated FOXO-1 through deacetylation, and its knockdown led to increased apoptosis. SIRT1 knockdown also significantly decreased parasite survival along with increased production of TNFα, ROS and NO. Administration of the SIRT1 inhibitor sirtinol (10 mg/kg body weight) in infected mice decreased spleen parasite burden and a synergistic effect was found with PD-1 inhibitor. Collectively, our study shows that Leishmania utilizes the SIRT1/FOXO-1 axis for differentially regulating PD-1 signaling and, although they are interconnected, both pathways independently contribute to intracellular parasite survival.This article has an associated First Person interview with the first author of the paper.

UBXN1 interacts with the S1 protein of transmissible gastroenteritis coronavirus and plays a role in viral replication

Transmissible gastroenteritis coronavirus (TGEV) is an enteropathogenic coronavirus that causes diarrhea in pigs and is associated with high morbidity and mortality in sucking piglets. S1 is one of two protein domains in the spike (S) glycoprotein and is responsible for enteric tropism, sialic acid recognition, and host receptor binding. Although there has been extensive research on the S1 protein of TGEV, little is known about the intracellular role of TGEV-S1. In the present study, we used yeast two-hybrid screening of a cDNA library from porcine intestinal cells to identify proteins that interact with TGEV-S1. Among 120 positive clones from the library, 12 intracellular proteins were identified after sequencing and a BLAST search. These intracellular proteins are involved in protein synthesis and degradation, biological signal transduction, and negative control of signaling pathways. Using a glutathione-S-transferase (GST) pulldown assay and Co-IP, we found that UBXN1 interacts with the S1 protein. Here, we observed that TGEV infection led to increased UBXN1 expression levels during the late phase of infection in IPEC-J2 cells. Inhibition of UBXN1 in IPEC-J2 cells via siRNA interference significantly decreased the viral titer and downregulated the expression of S1. UBXN1 overexpression significantly increased the viral copy number. Additionally, we provided data suggesting that UBXN1 negatively regulates IFN-β expression after TGEV infection. Finally, our research indicated that UBXN1 plays a vital role in the process of TGEV infection, making it a candidate target for the development of a novel antiviral method.

Inflammatory and Humoral Immune Response during Ebola Virus Infection in Survivor and Fatal Cases Occurred in Sierra Leone during the 2014⁻2016 Outbreak in West Africa.

Ebola virus (EBOV) infection is characterized by an excessive inflammatory response, a loss of lymphocytes and a general paralysis of the immune system, however pathophysiological mechanisms are not fully understood. In a cohort of 23 fatal and 21 survivors of ebola virus disease (EVD) cases admitted to the Emergency Ebola-Treatment-Center in Goderich (Freetown, Sierra Leone) during the 2014 to 2016 EBOV epidemic in Western Africa, we analyzed the pathway-focused gene expression profile of secreted proteins involved in the immune response and the levels of specific anti-EBOV IgM and IgG from the time of admission till discharge or death. We observed a dysregulated inflammatory response in fatal patients as compared to survivors, mainly consisting of the upregulation of inflammatory mediators, whose extent directly correlated with viremia levels. The upregulation persisted and intensified during the late phase of infection. Relevant differences were also found in humoral immunity, as an earlier and more robust EBOV antibody response was observed in survivor patients.

Structure-Guided Drug Design of 6-Substituted Adenosine Analogues as Potent Inhibitors of Mycobacterium tuberculosis Adenosine Kinase.

Mycobacterium tuberculosis adenosine kinase (MtbAdoK) is an essential enzyme of Mtb and forms part of the purine salvage pathway within mycobacteria. Evidence suggests that the purine salvage pathway might play a crucial role in Mtb survival and persistence during its latent phase of infection. In these studies, we adopted a structural approach to the discovery, structure-guided design, and synthesis of a series of adenosine analogues that displayed inhibition constants ranging from 5 to 120 nM against the enzyme. Two of these compounds exhibited low micromolar activity against Mtb with half maximal effective inhibitory concentrations of 1.7 and 4.0 μM. Our selectivity and preliminary pharmacokinetic studies showed that the compounds possess a higher degree of specificity against MtbAdoK when compared with the human counterpart and are well tolerated in rodents, respectively. Finally, crystallographic studies showed the molecular basis of inhibition, potency, and selectivity and revealed the presence of a potentially therapeutically relevant cavity unique to the MtbAdoK homodimer.

Upregulation of CHOP participates in caspase activation and virus release in human astrovirus-infected cells.

Human astroviruses (HAstVs), non-enveloped RNA viruses with positive-sense RNA genomes, are an important cause of acute gastroenteritis in young children, although the processes that produce infectious virions are not clearly defined. To track the viral replication complex (RC) upon HAstV1 infection, the subcellular distribution of double-stranded (ds) RNA and of ORF1b, a viral RNA polymerase, was examined by immunocytochemistry. Foci that were positive for dsRNA and for ORF1b were co-localized, and both foci were also co-localized with resident proteins of the endoplasmic reticulum (ER). Focusing on the association between the HAstV RC and ER, we examined the expression of unfolded protein response (UPR) markers and found that targets of eukaryotic translation initiation factor 2α (eIF2α)-activating transcription factor 4 (ATF4), including CCAAT/enhancer-binding protein homologous protein (CHOP), a proapoptotic transcription factor, were upregulated at the late phase in HAstV-infected cells. Consistently, eIF2α was phosphorylated at the late phase of HAstV infection. The formation of foci resembling stress granules, another known downstream response to eIF2α phosphorylation, was also observed at the same period. Phosphorylation of eIF2α was attenuated in protein kinase R (PKR)-knockdown cells, suggesting that, unlike the canonical ER stress response, PKR was involved in eIF2α phosphorylation in response to HAstV infection. Studies have indicated that immature HAstV capsid protein is processed by caspases, and caspase cleavage is integral to particle release. Inhibition of CHOP upregulation reduced caspase activation and the release of HAstV RNA from cells during HAstV infection. Our results suggest that the eIF2α-ATF4-CHOP pathway participates in HAstV propagation.

Showering with the Driveline Exit Site Exposed to Well Water Does Not Increase Rates of Driveline Exit Site Infection

Purpose Determine the effects of showering on rates of driveline exit site infections (DLESI). Methods Prospective analysis of all durable left ventricular assist device (LVAD) patient implants at a single academic center from June 2011 to June 2018. All patients who were provided instructions for showering were included in this analysis (n=164). Exclusion criteria included patients that expired before 90 days of support and those not discharged prior to transplant (n=30). Patients were instructed to shower without a dressing covering their DLES, to use antibacterial soap and then immediately apply a sterile dressing using a standard kit of supplies. Infections were diagnosed with positive exit site cultures. Self-reported household water sources, well water vs municipal water, were used to compare the rates of DLESI. Our overall DLESI infection rates were compared to STS INTERMACS data. SPSS was used to analyze statistics. Results Overall at our center, 77% of the patients were free of DLESI. Demographics, duration of support, indication for LVAD and payer source for the well water and municipal water groups were similar except the well water group was older (p=0.003). Freedom from DLESI was 83% (n=38/46) & 74% (n=65/88) of patients who showered with well & municipal water respectively (p=0.254). Kaplan Meier curves are similar (p=0.151). The mean time to DLESI is 90 days and 87 days in the well and municipal water groups respectively (p=0.153). The late phase infection rate (after the first three months) per 100 pt months at our center is 1.16 compared to STS INTERMACS at 1.38. Conclusion At a single center, LVAD patients showering with different water sources have comparable rates of freedom from DLESIs. LVAD patients who follow a DLES management protocol that includes showering have comparable rates of DLESI when compared to STS INTERMACS data.

Blocking the IL-1β signalling pathway prevents chronic viral myocarditis and cardiac remodeling

Coxsackieviruses of group B (CVB) are well-known causes of acute and chronic myocarditis. Chronic myocarditis can evolve into dilated cardiomyopathy (DCM) characterized by fibrosis and cardiac remodeling. Interleukin-1β (IL-1β) plays a decisive role in the induction of the inflammatory response as a consequence of viral replication. In this study, we analyzed the effects of IL-1β neutralization on the transition of acute to chronic myocarditis in a mouse model of CVB3 myocarditis. Mice were treated with an anti-murine IL-1β antibody as a surrogate for Canakinumab at different time points post CVB3 infection. Treatment was performed in the early phase (day 1-14 pi, day 3-14 pi) or at a later stage of myocarditis (day 14-28 pi). Subsequently, the hearts were examined histologically, immunohistochemically and by molecular biology. A significant reduction of viral replication, cardiac damage and inflammation was found after administration of the antibody in the early phase and in the later phase of infection. Furthermore, less collagen I deposition and a considerable reduction of fibrosis were found in antibody-treated mice. Using microarray analysis, a significant upregulation of various extracellular matrix and fibrosis-associated molecules was found in CVB3-infected mice, including TGF-β, TIMP-1 and MMP12, as well as diverse matricellular proteins, whereas, these molecules were significantly downregulated in all IL-1β antibody-treated infected mice. Neutralization of IL-1β at different stages of enteroviral infection prevents the development of chronic viral myocarditis by reducing inflammation, interstitial fibrosis and adverse cardiac remodeling. These findings are relevant for the treatment of patients with acute and chronic myocarditis.

Host microRNA analysis in cyprinid Herpesvirus-3 (CyHV-3) infected common carp

BackgroundThe mechanism of latency and the ability of the cyprinid herpesvirus 3 (CyHV-3) to establish life-long infections in carp remains poorly understood. To explain the role of miRNAs in this process we applied a range of molecular tools including high-throughput sequencing of RNA libraries constructed from the blood samples of infected fish followed by bioinformatic and functional analyses which show that CyHV-3 profoundly influences the expression of host miRNAs in vivo.ResultsWe demonstrated the changed expression of 27 miRNAs in the clinical phase and 5 in the latent phase of infection. We also identified 23 novel, not previously reported sequences, from which 8 showed altered expressions in control phase, 10 in clinical phase and 5 in latent phase of infection.ConclusionsThe results of our analysis expand the knowledge of common carp microRNAs engaged during CyHV-3 infection and provide a useful basis for the further study of the mechanism of CyHV-3 induced pathology.

In vitro growth kinetics and gene expression analysis of the turkey adenovirus 3, a siadenovirus

Turkey adenovirus 3 (TAdV-3) belongs to the genus Siadenovirus, family Adenoviridae. Previously, nucleotide sequencing and annotation of the Virginia avirulent strain (VAS) of TAdV-3 genome, isolated in our laboratory, indicated the presence of a total of 23 genes and open reading frames (ORFs). The goals of this study were 1) to delineate the growth kinetics of the virus using a qPCR-based infectivity assay, and 2) to determine the virus gene expression profile during the early and late phases of infection in target B lymphocytes. The one-step growth curve experiment demonstrated 3 phases of virus replication cycle: a lag phase lasted for 12–18 h post-infection (h.p.i.), in which the virus titer declined; a log phase from 18 to 120 h.p.i., in which the number of infectious virus particles increased over 20,000 folds, and a brief decline phase thereafter. Southern blot analysis indicated that the synthesis of new viral DNA started by 8 h.p.i. Gene-specific RT-PCR analysis revealed the expression of mRNAs from the 23 TAdV-3 genes/ORFs. According to the temporal transcriptional profiling of TAdV-3 genome, genes could be divided into 3 groups based on the time of transcription initiation: group 1 showed detectable levels of transcription at 2 h.p.i and included 7 genes, i.e., hyd, III, pX, pVI, II, 100 K, and 33 K; group 2 included 12 genes whose mRNAs were detected for the first time at 4 h.p.i., i.e., ORF1, IVa2, pol, pTP, pIIIa, EP, DBP, E3, U exon, IV, ORF7, and ORF8; group 3 of transcripts were detectable starting 8 h.p.i. and included only 4 genes, i.e., 52 K, 22 K, pVII, and pVIII. Our data suggest that the transcriptional kinetics of genus Siadenovirus differ from that observed in other adenoviral genera; however, a few TAdV-3 genes showed similar expression patterns to their adenoviral homologs.

Ultrasonographic abdominal findings in patients with severe yellow fever and liver evaluation with elastosonography in convalescence

Purpose To evaluate the abdominal ultrasound (US) findings in patients in the severe acute phase of YF, correlating with clinical and laboratory data, and to estimate the degree of hepatic fibrosis using shear-wave elastography with ultrasonography. Methods This is a combined retrospective description and follow-up study. First, bedside US examinations in all patients admitted with YF between January and April 2018. B-mode and Doppler were done, within 48h of patient admission. Liver and kidney echogenicity were compared to the spleen. All images were revised by a second radiologist. In a second stage, patients were submitted to a new US, 6 months after onset of symptoms, with the elastography technique (SWE). Exclusion criteria: patients with US features of previous chronic hepatic disease and/or portal hypertension. Results 46 patients were evaluated with bedside US. Six (13.0%) were female; median age was 44.8 (34.8-62.3). 26 (56.5%) patients died within 30 days of admission. The abdominal US findings were: gallbladder wall thickening (80.4%), increased renal cortex echogenicity (71.7%), increased liver parenchyma echogenicity (65.2%), perirrenal fluid (52.2%) and intraperitoneal free fluid (30.4%). Increased renal echogenicity was associated with higher median serum creatinine levels (5.1 (2.7-6.5) mg/dL versus 3.1 (1.0-2.4) mg/dL; p = 0.02) and higher rates of death within 30 days of admission (66.7% versus 30.8%; p = 0.03). There were no correlations between other clinical or laboratory data and US findings. Seventeen patients were evaluated with SWE 6 months after of onset of symptoms. Mean shear wave velocity was 1,4 ( ± 0,2) m/s; mean elasticity was 5,3 ( ± 1,7) kPa. Sixteen (94%) patients were classified in the F0/F1 Metavir category. One patient had mild increased stiffness and was classified as F2 Metavir. Conclusion This is the first study to describe the abdominal imaging findings in patients with YF using US. We found consistent findings related to direct effects of viral infection (pattern of diffuse liver fatty deposition and nephropathy) and secondary to inflammatory changes and/or hemorrhagic diathesis (gallbladder wall thickening and fluid collections). Increased renal echogenicity was associated with higher serum creatinine levels and death rates and thus should be considered a prognostic variable. After 6 months, 01 patient showed mild increased liver stiffness in the elastography evaluation. The results may shine a light upon the natural history of the infection, helping clarify the initial disease mechanisms and refute the hypothesis that fibrosis plays a role in the late phases of infection.

Metformin Promotes the Protection of Mice Infected With Plasmodium yoelii Independently of γδ T Cell Expansion.

Adaptive immune responses are critical for protection against infection with Plasmodium parasites. The metabolic state dramatically changes in T cells during activation and the memory phase. Recent findings suggest that metformin, a medication for treating type-II diabetes, enhances T-cell immune responses by modulating lymphocyte metabolism. In this study, we investigated whether metformin could enhance anti-malaria immunity. Mice were infected with Plasmodium yoelii and administered metformin. Levels of parasitemia were reduced in treated mice compared with those in untreated mice, starting at ~2 weeks post-infection. The number of γδ T cells dramatically increased in the spleens of treated mice compared with that in untreated mice during the later phase of infection, while that of αβ T cells did not. The proportions of Vγ1+ and Vγ2+ γδ T cells increased, suggesting that activated cells were selectively expanded. However, these γδ T cells expressed inhibitory receptors and had severe defects in cytokine production, suggesting that they were in a state of exhaustion. Metformin was unable to rescue the cells from exhaustion at this stage. Depletion of γδ T cells with antibody treatment did not affect the reduction of parasitemia in metformin-treated mice, suggesting that the effect of metformin on the reduction of parasitemia was independent of γδ T cells.

Characterization of the interaction between outer-fiber protein VP55 of genotype III grass carp reovirus and Fibulin-4 of grass carp

Genotype III grass carp reovirus (GCRV; representative strain, GCRV-104) belongs to the subfamily Spinareovirinae and encodes an outer-fiber protein, VP55, responsible for mediating the infection of target tissues by the virus and assisting the virus into cells. Fibulin-4/EFEMP2 protein was previously identified as a putative binding partner for VP55 in a yeast two-hybrid screening. Here, we have further characterized the association between Fibulin-4 and VP55 by using protein interaction assays. An intracellular co-localization assay showed that RFP-Fibulin-4 co-localized with GFP-VP55 in grass carp ovary (GCO) cells. Bacterially expressed GST-tagged Fibulin-4 was shown to associate with baculovirus-expressed His-tagged VP55 in a dot-blot overlay assay; moreover, baculovirus-expressed His-tagged VP55 was able to pull down GFP-Fibulin-4 expressed in the GCO cells. We performed real-time PCR and immunoblotting analysis and showed that endogenous Fibulin-4, although suppressed to a lower level in the late infection phase, is present throughout the infection course of GCRV-104 in CIK cells. In conclusion, our results indicate that grass carp Fibulin-4 interacts with VP55. The presence of Fibulin-4, a well-known secreted protein, during the infection course of GCRV-104 in grass carp cells implies its potential role during viral egression through interaction with VP55.

Bombyx mori nucleopolyhedrovirus protein Bm11 is involved in occlusion body production and occlusion-derived virus embedding

Bombyx mori nucleopolyhedrovirus (BmNPV) orf11 (bm11) is a highly conserved gene with unknown function. It is homologous to AcMNPV orf19. In this study, a bm11 knockout virus was constructed and its role was investigated. Expression analysis indicated that bm11 is a late gene and confocal microscopy analysis demonstrated that Bm11 localizes predominantly in the nuclear ring zone at the late phase of infection. The bm11 deletion did not affect budded virus (BV) production or viral genome replication, but markedly reduced the production of occlusion bodies (OBs) and the embedding of occlusion-derived viruses (ODVs). Bio-assays showed that Bm11 was involved in BmNPV infectivity in vivo by direct injection. In conclusion, our results demonstrated that although Bm11 is not essential for BV production or mature ODV formation, it affects OB production and ODV occlusion.

A new model for chronic and reactivation tuberculosis: Infection with genetically attenuated Mycobacterium tuberculosis in mice with polar susceptibility

TB infection in mice develops relatively rapidly which interferes with experimental dissection of immune responses and lung pathology features that differ between genetically susceptible and resistant hosts. Earlier we have shown that the M. tuberculosis strain lacking four of five Rpf genes (ΔACDE) is seriously attenuated for growth in vivo. Using this strain, we assessed key parameters of lung pathology, immune and inflammatory responses in chronic and reactivation TB infections in highly susceptible I/St and more resistant B6 mice. ΔACDE mycobacteria progressively multiplied only in I/St lungs, whilst in B6 lung CFU counts decreased with time. Condensed TB foci apeared in B6 lungs at week 4 of infection, whilst in I/St their formation was delayed. At the late phase of infection, in I/St lungs TB foci fused resulting in extensive pneumonia, whereas in B6 lungs pathology was limited to condensed foci. Macrophage and neutrophil populations characteristically differed between I/St and B6 mice at early and late stages of infection: more neutrophils accumulated in I/St and more macrophages in B6 lungs. The expression level of chemokine genes involved in neutrophil influx was higher in I/St compared to B6 lungs. B6 lung cells produced more IFN-γ, IL-6 and IL-11 at the early and late phases of infection. Overall, using a new mouse model of slow TB progression, we demonstrate two important features of ineffective infection control underlined by shifts in lung inflammation: delay in early granuloma formation and fusion of granulomas resulting in consolidated pneumonia late in the infectious course.

Friend retrovirus infection induces the development of memory-like natural killer cells

Traditionally, NK cells belong to the innate immune system and eliminate virus-infected cells through their germline-encoded receptors. However, NK cells were recently reported to possess memory-like functions that were predominantly provided by hepatic NK cells. Memory properties were mainly documented in contact hypersensitivity models or during cytomegalovirus infections. However, the precise role and the physiologic importance of memory-like NK cells during retroviral infections are still under investigation. Here, we show that Friend retrovirus (FV) infection of mice induced a population of phenotypically memory-like NK cells at 28 days post infection. Upon secondary antigen encounter, these NK cells showed an increased production of the pro-inflammatory cytokines IFNγ and TNFα as well as the death ligand FasL in comparison to naïve NK cells. Furthermore, we found an augmented elimination of antigen-matched but not antigen-mismatched target cells by these memory-like NK cells. In adoptive cell transfer experiments, equal antiviral activities of splenic and hepatic memory-like NK cells during the late phase of acute FV infection were found. Our results strongly imply the existence and antiviral activity of spleen and liver memory-like NK cells in FV infection, which efficiently respond upon secondary exposure to retroviral antigens.

Autocrine IL-10 Signaling Promotes Dendritic Cell Type-2 Activation and Persistence of Murine Cryptococcal Lung Infection.

The substantial morbidity and mortality caused by invasive fungal pathogens, including Cryptococcus neoformans, necessitates increased understanding of protective immune responses against these infections. Our previous work using murine models of cryptococcal lung infection demonstrated that dendritic cells (DCs) orchestrate critical transitions from innate to adaptive immunity and that IL-10 signaling blockade improves fungal clearance. To further understand interrelationships among IL-10 production, fungal clearance, and the effect of IL-10 on lung DCs, we performed a comparative temporal analysis of cryptococcal lung infection in wild type C57BL/6J mice (designated IL-10+/+) and IL-10-/- mice inoculated intratracheally with C. neoformans (strain 52D). Early and sustained IL-10 production by lung leukocytes was associated with persistent infection in IL-10+/+ mice, whereas fungal clearance was improved in IL-10-/- mice during the late adaptive phase of infection. Numbers of monocyte-derived DCs, T cells, and alveolar and exudate macrophages were increased in lungs of IL-10-/- versus IL-10+/+ mice concurrent with evidence of enhanced DC type-1, Th1/Th17 CD4 cell, and classical macrophage activation. Bone marrow-derived DCs stimulated with cryptococcal mannoproteins, a component of the fungal capsule, upregulated expression of IL-10 and IL-10R, which promoted DC type-2 activation in an autocrine manner. Thus, our findings implicate fungus-triggered autocrine IL-10 signaling and DC type-2 activation as important contributors to the development of nonprotective immune effector responses, which characterize persistent cryptococcal lung infection. Collectively, this study informs and strengthens the rationale for IL-10 signaling blockade as a novel treatment for fungal infections.

γδ T cells modulate humoral immunity against Plasmodium berghei infection.

It is unclear whether γδ T cells are involved in humoral immunity against Plasmodium infection. Here, we show that B-cell-immunodeficient mice and γδ T-cell-deficient mice were incapable of protecting against Plasmodium berghei XAT parasites. γδ T-cell-deficient mice developed reduced levels of antigen-specific antibodies during the late phase of infection. The numbers of follicular helper T cells and germinal centre B cells in γδ T-cell-deficient mice were lower than in wild-type mice during the late phase of infection. Expression profiling of humoral immunity-related cytokines in γδ T cells showed that interleukin-21 (IL-21) and interferon-γ (IFN-γ) are increased during the early stage of infection. Furthermore, blockade of IL-21 and IFN-γ signalling during the early stage of infection led to reduction in follicular helper T cells and germinal centre B cells. γδ T-cell production of IL-21 and IFN-γ is crucial for the development and maintenance of follicular helper T cells and germinal centre B cells during the late phase of infection. Our data suggest that γδ T cells modulate humoral immunity against Plasmodium infection.