bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chronic Plasmodium chabaudi Infection Generates CD4 Memory T Cells with Increased T Cell Receptor Sensitivity but Poor Secondary Expansion and Increased Apoptosis
Authors: Opata Michael M. , Stephens Robin 
Published: December 2016

ABSTRACTExposure to blood-stage malaria infection is often persistent, leading to generation of CD4 effector and effector memory T cells that contribute to protection. We showed previously that chronic exposure to blood-stagePlasmodium chabaudioffers the best protection from parasitemia and pathology in reinfection cases, correlating with an increase in Th1 cells. Although much is known about the features of resting or exhausted memory T cells (Tmem), little is known about the functional capacities of chronically stimulated but protective T cells. To determine the functional capacity of CD4 T cells generated by chronic infection upon reexposure to parasite, we compared their responses to known features of classical Tmem. The numbers of cytokine-producing T cells increased following infection in the polyclonal populations, suggesting an increase in pathogen-specific T cells. Malaria antigen-specific B5 T cell receptor (TCR) transgenic (Tg) T cells from chronic infection proliferated on reinfection and were highly sensitive to TCR stimulation without costimulation, as shown for Tmem in acute stimulations. However, B5 Tmem did not accumulate more than naive B5 T cellsin vivoorin vitroand became apoptotic. Failure to accumulate was partly the result of chronic stimulation, since eliminating persistent parasites before reinfection slightly increased the accumulation of B5 Tg T cells upon reinfection. The levels of specific gamma interferon-positive, interleukin-10-positive T cells, which protect animals from pathology, increased after malaria infection. These data demonstrate that although chronic infection generates a protective T cell population with increased TCR sensitivity and cytokine production, they do not reexpand upon reexposure due to increased apoptosis.
Immunization with Pneumocystis Cross-Reactive Antigen 1 (Pca1) Protects Mice against Pneumocystis Pneumonia and Generates Antibody to Pneumocystis jirovecii
Authors: Tesini Brenda L. , Wright Terry W. , Malone Jane E. , Haidaris Constantine G. , Harber Martha , Sant Andrea J. , Nayak Jennifer L. , Gigliotti Francis 
Published: December 2016

ABSTRACT

Pneumocystis
pneumonia (PcP) is a life-threatening infection that affects immunocompromised individuals. Nearly half of all PcP cases occur in those prescribed effective chemoprophylaxis, suggesting that additional preventive methods are needed. To this end, we have identified a unique mouse
Pneumocystis
surface protein, designated
Pneumocystis
cross-reactive antigen 1 (Pca1), as a potential vaccine candidate. Mice were immunized with a recombinant fusion protein containing Pca1. Subsequently, CD4
+
T cells were depleted, and the mice were exposed to
Pneumocystis murina
. Pca1 immunization completely protected nearly all mice, similar to immunization with whole
Pneumocystis
organisms. In contrast, all immunized negative-control mice developed PcP. Unexpectedly, Pca1 immunization generated cross-reactive antibody that recognized
Pneumocystis jirovecii
and
Pneumocystis carinii
. Potential orthologs of Pca1 have been identified in
P. jirovecii
. Such cross-reactivity is rare, and our findings suggest that Pca1 is a conserved antigen and potential vaccine target. The evaluation of Pca1-elicited antibodies in the prevention of PcP in humans deserves further investigation.
Pseudomonas aeruginosa GroEL Stimulates Production of PTX3 by Activating the NF-κB Pathway and Simultaneously Downregulating MicroRNA-9
Authors: Shin Heesung , Jeon Jisu , Lee Jung-Hoon , Jin Shouguang , Ha Un-Hwan 
Published: December 2016

ABSTRACTAs one of the first lines of host defense, monocytes play important roles in clearing infected microbes. The defensive response is triggered by recognition of diverse microbial moieties, including released factors, which modulate host immune responses to establish a harsh environment for clinically important bacterial pathogens. In this study, we found that the expression of PTX3, a soluble form of pattern recognition receptor, was induced by infection with livePseudomonas aeruginosaor treatment of cells with its supernatant.P. aeruginosaGroEL, a homolog of heat shock protein 60, was identified as one of the factors responsible for inducing the expression ofPTX3in host cells. GroEL inducedPTX3expression by activating the Toll-like receptor 4 (TLR4)-dependent pathway via nuclear factor-kappa B (NF-κB), while simultaneously inhibiting expression of microRNA-9, which targets thePTX3transcript. Finally, by acting as an opsonin, GroEL-induced PTX3 promoted the association and phagocytosis ofStaphylococcus aureusinto macrophages. These data suggest that the host defensive environment is supported by the production of PTX3 in response to GroEL, which thus has therapeutic potential for clearance of bacterial infections.
TonB-Dependent Heme/Hemoglobin Utilization by Caulobacter crescentus HutA
Authors: Balhesteros Heloise , Shipelskiy Yan , Long Noah J. , Majumdar Aritri , Katz Benjamin B. , Santos Naara M. , Leaden Laura , Newton Salete M. , Marques Marilis V. , Klebba Phillip E. 
Published: December 2016

ABSTRACT

Siderophore nutrition tests with
Caulobacter crescentus
strain NA1000 revealed that it utilized a variety of ferric hydroxamate siderophores, including asperchromes, ferrichromes, ferrichrome A, malonichrome, and ferric aerobactin, as well as hemin and hemoglobin.
C. crescentus
did not transport ferrioxamine B or ferric catecholates. Because it did not use ferric enterobactin, the catecholate aposiderophore was an effective agent for iron deprivation. We determined the kinetics and thermodynamics of [
59
Fe]apoferrichrome and
59
Fe-citrate binding and transport by NA1000. Its affinity and uptake rate for ferrichrome (equilibrium dissociation constant [

K
d

], 1 nM; Michaelis-Menten constant [

K
M

], 0.1 nM;
V
max
, 19 pMol/10
9
cells/min) were similar to those of
Escherichia coli
FhuA. Transport properties for
59
Fe-citrate were similar to those of
E. coli
FecA (

K
M

, 5.3 nM;
V
max
, 29 pMol/10
9
cells/min). Bioinformatic analyses implicated Fur-regulated loci
00028
,
00138
,
02277
, and
03023
as TonB-dependent transporters (TBDT) that participate in iron acquisition. We resolved TBDT with elevated expression under high- or low-iron conditions by SDS-PAGE of sodium sarcosinate cell envelope extracts, excised bands of interest, and analyzed them by mass spectrometry. These data identified five TBDT: three were overexpressed during iron deficiency (00028, 02277, and 03023), and 2 were overexpressed during iron repletion (00210 and 01196). CLUSTALW analyses revealed homology of putative TBDT 02277 to
Escherichia coli
FepA and BtuB. A Δ
02277
mutant did not transport hemin or hemoglobin in nutrition tests, leading us to designate the
02277
structural gene as
hutA
(for
h
eme/hemoglobin
u
tilization).

IMPORTANCE
The physiological roles of the 62 putative TBDT of
C. crescentus
are mostly unknown, as are their evolutionary relationships to TBDT of other bacteria. We biochemically studied the iron uptake systems of
C. crescentus
, identified potential iron transporters, and clarified the phylogenetic relationships among its numerous TBDT. Our findings identified the first outer membrane protein involved in iron acquisition by
C. crescentus
, its heme/hemoglobin transporter (HutA).
An Optimized Hepatitis C Virus E2 Glycoprotein Core Adopts a Functional Homodimer That Efficiently Blocks Virus Entry
Authors: McCaffrey Kathleen , Boo Irene , Owczarek Catherine M. , Hardy Matthew P. , Perugini Matthew A. , Fabri Louis , Scotney Pierre , Poumbourios Pantelis , Drummer Heidi E. 
Published: December 2016

ABSTRACT

The hepatitis C virus (HCV) envelope glycoprotein E2 is the major target of broadly neutralizing antibodies
in vivo
and is the focus of efforts in the rational design of a universal B cell vaccine against HCV. The E2 glycoprotein exhibits a high degree of amino acid variability which localizes to three discrete regions: hypervariable region 1 (HVR1), hypervariable region 2 (HVR2), and the intergenotypic variable region (igVR). All three variable regions contribute to immune evasion and/or isolate-specific structural variations, both important considerations for vaccine design. A high-resolution structural definition of the intact HCV envelope glycoprotein complex containing E1 and E2 remains to be elucidated, while crystallographic structures of a recombinant E2 ectodomain failed to resolve HVR1, HVR2, and a major neutralization determinant adjacent to HVR1. To obtain further information on E2, we characterized the role of all three variable regions in E2 ectodomain folding and function in the context of a recombinant ectodomain fragment (rE2). We report that removal of the variable regions accelerates binding to the major host cell receptor CD81 and that simultaneous deletion of HVR2 and the igVR is required to maintain wild-type CD81-binding characteristics. The removal of the variable regions also rescued the ability of rE2 to form a functional homodimer. We propose that the rE2 core provides novel insights into the role of the variable motifs in the higher-order assembly of the E2 ectodomain and may have implications for E1E2 structure on the virion surface.

IMPORTANCE
Hepatitis C virus (HCV) infection affects ∼2% of the population globally, and no vaccine is available. HCV is a highly variable virus, and understanding the presentation of key antigenic sites at the virion surface is important for the design of a universal vaccine. This study investigates the role of three surface-exposed variable regions in E2 glycoprotein folding and function in the context of a recombinant soluble ectodomain. Our data demonstrate the variable motifs modulate binding of the E2 ectodomain to the major host cell receptor CD81 and have an impact on the formation of an E2 homodimer with high-affinity binding to CD81.
Interaction of the Small GTPase Cdc42 with Arginine Kinase Restricts White Spot Syndrome Virus in Shrimp
Authors: Xu Ji-Dong , Jiang Hai-Shan , Wei Tian-Di , Zhang Ke-Yi , Wang Xian-Wei , Zhao Xiao-Fan , Wang Jin-Xing 
Published: December 2016

ABSTRACT

Many types of small GTPases are widely expressed in eukaryotes and have different functions. As a crucial member of the Rho GTPase family, Cdc42 serves a number of functions, such as regulating cell growth, migration, and cell movement. Several RNA viruses employ Cdc42-hijacking tactics in their target cell entry processes. However, the function of Cdc42 in shrimp antiviral immunity is not clear. In this study, we identified a Cdc42 protein in the kuruma shrimp (
Marsupenaeus japonicus
) and named it
Mj
Cdc42.
Mj
Cdc42 was upregulated in shrimp challenged by white spot syndrome virus (WSSV). The knockdown of
Mj
Cdc42 and injection of Cdc42 inhibitors increased the proliferation of WSSV. Further experiments determined that
Mj
Cdc42 interacted with an arginine kinase (
Mj
AK). By analyzing the binding activity and enzyme activity of
Mj
AK and its mutant, Δ
Mj
AK, we found that
Mj
AK could enhance the replication of WSSV in shrimp.
Mj
AK interacted with the envelope protein VP26 of WSSV. An inhibitor of AK activity, quercetin, could impair the function of
Mj
AK in WSSV replication. Further study demonstrated that the binding of
Mj
Cdc42 and
Mj
AK depends on Cys
271
of
Mj
AK and suppresses the WSSV replication-promoting effect of
Mj
AK. By interacting with the active site of
Mj
AK and suppressing its enzyme activity,
Mj
Cdc42 inhibits WSSV replication in shrimp. Our results demonstrate a new function of Cdc42 in the cellular defense against viral infection in addition to the regulation of actin and phagocytosis, which has been reported in previous studies.

IMPORTANCE
The interaction of Cdc42 with arginine kinase plays a crucial role in the host defense against WSSV infection. This study identifies a new mechanism of Cdc42 in innate immunity and enriches the knowledge of the antiviral innate immunity of invertebrates.
Zika Virus Methyltransferase: Structure and Functions for Drug Design Perspectives
Authors: Coutard Bruno , Barral Karine , Lichière Julie , Selisko Barbara , Martin Baptiste , Aouadi Wahiba , Lombardia Miguel Ortiz , Debart Françoise , Vasseur Jean-Jacques , Guillemot Jean Claude , Canard Bruno , Decroly Etienne 
Published: December 2016

ABSTRACT

The
Flavivirus
Zika virus (ZIKV) is the causal agent of neurological disorders like microcephaly in newborns or Guillain-Barre syndrome. Its NS5 protein embeds a methyltransferase (MTase) domain involved in the formation of the viral mRNA cap. We investigated the structural and functional properties of the ZIKV MTase. We show that the ZIKV MTase can methylate RNA cap structures at the N-7 position of the cap, and at the 2′-O position on the ribose of the first nucleotide, yielding a cap-1 structure. In addition, the ZIKV MTase methylates the ribose 2′-O position of internal adenosines of RNA substrates. The crystal structure of the ZIKV MTase determined at a 2.01-Å resolution reveals a crystallographic homodimer. One chain is bound to the methyl donor (
S
-adenosyl-
l
-methionine [SAM]) and shows a high structural similarity to the dengue virus (DENV) MTase. The second chain lacks SAM and displays conformational changes in the αX α-helix contributing to the SAM and RNA binding. These conformational modifications reveal a possible molecular mechanism of the enzymatic turnover involving a conserved Ser/Arg motif. In the second chain, the SAM binding site accommodates a sulfate close to a glycerol that could serve as a basis for structure-based drug design. In addition, compounds known to inhibit the DENV MTase show similar inhibition potency on the ZIKV MTase. Altogether these results contribute to a better understanding of the ZIKV MTase, a central player in viral replication and host innate immune response, and lay the basis for the development of potential antiviral drugs.

IMPORTANCE
The Zika virus (ZIKV) is associated with microcephaly in newborns, and other neurological disorders such as Guillain-Barre syndrome. It is urgent to develop antiviral strategies inhibiting the viral replication. The ZIKV NS5 embeds a methyltransferase involved in the viral mRNA capping process, which is essential for viral replication and control of virus detection by innate immune mechanisms. We demonstrate that the ZIKV methyltransferase methylates the mRNA cap and adenosines located in RNA sequences. The structure of ZIKV methyltransferase shows high structural similarities to the dengue virus methyltransferase, but conformational specificities highlight the role of a conserved Ser/Arg motif, which participates in RNA and SAM recognition during the reaction turnover. In addition, the SAM binding site accommodates a sulfate and a glycerol, offering structural information to initiate structure-based drug design. Altogether, these results contribute to a better understanding of the
Flavivirus
methyltransferases, which are central players in the virus replication.
The Structural Interface between HIV-1 Vif and Human APOBEC3H
Authors: Ooms Marcel , Letko Michael , Simon Viviana 
Published: December 2016

ABSTRACT
Human APOBEC3H (A3H) is a cytidine deaminase that inhibits HIV-1 replication. To evade this restriction, the HIV-1 Vif protein binds A3H and mediates its proteasomal degradation. To date, little information on the Vif-A3H interface has been available. To decipher how both proteins interact, we first mapped the Vif-binding site on A3H by functionally testing a large set of A3H mutants in single-cycle infectivity and replication assays. Our data show that the two A3H α-helixes α3 and α4 represent the Vif-binding site of A3H. We next used viral adaptation and a set of Vif mutants to identify novel, reciprocal Vif variants that rescued viral infectivity in the presence of two Vif-resistant A3H mutants. These A3H-Vif interaction points were used to generate the first A3H-Vif structure model, which revealed that the A3H helixes α3 and α4 interact with the Vif β-sheet (β2-β5). This model is in good agreement with previously reported Vif and A3H amino acids important for interaction. Based on the predicted A3H-Vif interface, we tested additional points of contact, which validated our model. Moreover, these experiments showed that the A3H and A3G binding sites on HIV-1 Vif are largely distinct, with both host proteins interacting with Vif β-strand 2. Taken together, this virus-host interface model explains previously reported data and will help to identify novel drug targets to combat HIV-1 infection.

IMPORTANCE
HIV-1 needs to overcome several intracellular restriction factors in order to replicate efficiently. The human APOBEC3 locus encodes seven proteins, of which A3D, A3F, A3G, and A3H restrict HIV-1. HIV encodes the Vif protein, which binds to the APOBEC3 proteins and leads to their proteasomal degradation. No HIV-1 Vif-APOBEC3 costructure exists to date despite extensive research. We and others previously generated HIV-1 Vif costructure models with A3G and A3F by mapping specific contact points between both proteins. Here, we applied a similar approach to HIV-1 Vif and A3H and successfully generated a Vif-A3H interaction model. Importantly, we find that the HIV-1 Vif-A3H interface is distinct from the Vif-A3G and Vif-A3F interfaces, with a small Vif region being important for recognition of both A3G and A3H. Our Vif-A3H structure model informs on how both proteins interact and could guide toward approaches to block the Vif-A3H interface to target HIV replication.
Herpes Simplex Virus 1 Ubiquitin-Specific Protease UL36 Abrogates NF-κB Activation in DNA Sensing Signal Pathway
Authors: Ye Ruijie , Su Chenhe , Xu Haiyan , Zheng Chunfu 
Published: December 2016

ABSTRACT
The DNA sensing pathway triggers innate immune responses against DNA virus infection, and NF-κB signaling plays a critical role in establishing innate immunity. We report here that the herpes simplex virus 1 (HSV-1) ubiquitin-specific protease (UL36USP), which is a deubiquitinase (DUB), antagonizes NF-κB activation, depending on its DUB activity. In this study, ectopically expressed UL36USP blocked promoter activation of beta interferon (IFN-β) and NF-κB induced by cyclic GMP-AMP synthase (cGAS) and stimulator of interferon genes (STING). UL36USP restricted NF-κB activation mediated by overexpression of STING, TANK-binding kinase 1, IκB kinase α (IKKα), and IKKβ, but not p65. UL36USP was also shown to inhibit IFN-stimulatory DNA-induced IFN-β and NF-κB activation under conditions of HSV-1 infection. Furthermore, UL36USP was demonstrated to deubiquitinate IκBα and restrict its degradation and, finally, abrogate NF-κB activation. More importantly, the recombinant HSV-1 lacking UL36USP DUB activity, denoted as C40A mutant HSV-1, failed to cleave polyubiquitin chains on IκBα. For the first time, UL36USP was shown to dampen NF-κB activation in the DNA sensing signal pathway to evade host antiviral innate immunity.

IMPORTANCE
It has been reported that double-stranded-DNA-mediated NF-κB activation is critical for host antiviral responses. Viruses have established various strategies to evade the innate immune system. The N terminus of the HSV-1 UL36 gene-encoded protein contains the DUB domain and is conserved across all herpesviruses. This study demonstrates that UL36USP abrogates NF-κB activation by cleaving polyubiquitin chains from IκBα and therefore restricts proteasome-dependent degradation of IκBα and that DUB activity is indispensable for this process. This study expands our understanding of the mechanisms utilized by HSV-1 to evade the host antiviral innate immune defense induced by NF-κB signaling.
MRI appearance does not change in the first 7 days after acute hamstring injury—a prospective study
Authors: Wangensteen Arnlaug , Bahr Roald , Van Linschoten Robbart , Almusa Emad , Whiteley Rodney , Witvrouw Erik , Tol Johannes L 
Published: December 2016

BackgroundThe optimal timing of MRI following acute hamstring injury is not known and is mainly based on expert opinions.AimsTo describe the day-to-day changes in the extent of oedema and investigate the optimal timing for detection of fibre disruption on MRI following acute hamstring injuries.Study designProspective, descriptive study.MethodsWe performed standardised MRI (1.5T) ≤1 day after injury in male athletes with acute hamstring injury. If initial MRI revealed positive signs of injury (increased signal intensity on fluid sensitive sequences), consecutive MRIs were obtained daily throughout the subsequent week (ie, 7 times). The MRI parameters (day 1–7) were scored by a single radiologist using a standardised scoring form. The day-to-day changes in the extent of oedema (distance from tuber, craniocaudal length, mediolateral width and anteroposterior depth) and the presence and extent of fibre disruption (tear) were assessed with descriptive statistics and repeated measures using analysis of variance of log-transformed data. The overall main effect for time was reported with a significance level set at p<0.05.Results13 out of 132 male athletes assessed for eligibility between January 2014 and December 2015 were included. 1 dropped out, while 12 (31 years, range 20–49) completed the study; 11 had 7 MRI scans each and one had 5 MRI scans performed. There were no significant day-to-day changes for any of the extent of oedema measures (p values ranging from 0.12 to 0.81). Fibre disruption (tear), present in 5 of the athletes, was detectable from day 1, with small and insignificant day-to-day changes (p values ranging from 0.45 to 0.95).ConclusionsWe observed insignificant day-to-day changes in the extent of oedema throughout the first week following acute hamstring injury. Fibre disruption (tear) was detectable from the first day after injury. These findings indicate that MRI can be performed on any day during the first week following an acute (hamstring) muscle injury.
Undiagnosed diabetes and impaired fasting glucose inHFEC282Y homozygotes andHFEwild-type controls in the HEIRS Study
Authors: Barton James C , Barton J Clayborn , Adams Paul C , Acton Ronald T 
Published: December 2016

ObjectiveTo determine prevalences and predictors of undiagnosed diabetes mellitus (UDM) and impaired fasting glucose (IFG) in non-Hispanic whites withHFEp.C282Y homozygosity and controls without commonHFEmutations identified in population screening.Research design and methodsWe analyzed these observations in a postscreening examination: age; sex; body mass index; systolic/diastolic blood pressure; metacarpophalangeal joint hypertrophy; hepatomegaly; blood neutrophils; alanine and aspartate aminotransferase; elevated C reactive protein; transferrin saturation; serum ferritin; and Field Center.ResultsThere were 223 p.C282Y homozygotes and 449 controls without diagnosed diabetes (43.9% men). Mean age of p.C282Y homozygotes was 52±13 years (controls 57±14 years; p<0.0001). Mean transferrin saturation in p.C282Y homozygotes was 67±26% (controls 34±14%; p<0.0001). Mean serum ferritin in p.C282Y homozygotes was 607 pmol/L (95% CI 497 to 517; controls 274 pmol/L (247 to 301); p<0.0001). Overall prevalences of UDM (4.0% vs 4.2%) and IFG (23.8% vs 25.6%) did not differ significantly between p.C282Y homozygotes and wt/wt controls, respectively. In logistic regressions, male sex, body mass index, and alanine aminotransferase were significantly associated with UDM. ORs were 2.7 (1.2 to 2.8); 1.0 (1.0 to 1.1); and 1.0 (1.0 to 1.0), respectively. Age, male sex, and body mass index were significantly associated with IFG. ORs were 1.0 (1.0 to 1.1); 2.8 (1.9 to 4.2); and 1.0 (1.0 to 1.1), respectively.ConclusionsPrevalences of UDM and IFG were similar in p.C282Y homozygotes and controls in a postpopulation screening examination. Male sex was the strongest predictor of UDM and IFG.