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<B>ABSTRACT</B><P>The objective of the present study was to compare the effects of the modified live porcine reproductive and respiratory syndrome virus (PRRSV) vaccine (Ingelvac PRRS MLV; Boehringer Ingelheim Animal Health, St. Joseph, MO) on European and North American PRRSV shedding in the semen of experimentally infected boars. The boars were randomly divided into six groups. Vaccinated boars shed the North American PRRSV at the rate of 10<SUP>0.1</SUP>to 10<SUP>1.0</SUP>viral genome copies per ml and 3.63 to 10<SUP>1.1</SUP>50% tissue culture infective doses (TCID50)/ml, respectively, in semen, whereas nonvaccinated boars shed the North American PRRSV at the rate of 10<SUP>0.2</SUP>to 10<SUP>4.7</SUP>viral genome copies per ml and 1.14 to 10<SUP>3.07</SUP>TCID50/ml, respectively, in semen. Vaccinated boars shed the European PRRSV at the rate of 10<SUP>0.1</SUP>to 10<SUP>4.57</SUP>viral genome copies per ml and 1.66 to 10<SUP>3.10</SUP>TCID50/ml, respectively, in semen, whereas nonvaccinated boars shed the European PRRSV at the rate of 10<SUP>0.3</SUP>to 10<SUP>5.14</SUP>viral genome copies per ml and 1.69 to 10<SUP>3.17</SUP>TCID50/ml, respectively, in semen. The number of genomic copies of the European PRRSV in semen samples was not significantly different between vaccinated and nonvaccinated challenged European PRRSV boars. The present study demonstrated that boar vaccination using commercial modified live PRRSV vaccine was able to decrease subsequent shedding of North American PRRSV in semen after challenge but was unable to decrease shedding of European PRRSV in semen after challenge.</P>
<B>ABSTRACT</B><P>Pathogenic <I>Yersinia</I> spp. secrete Yops (<I>Yersinia</I> outer proteins) via the type III pathway. The expression of <I>yop</I> genes is regulated in response to environmental cues, which results in a cascade of type III secretion reactions. <I>yscM1</I> and <I>yscM2</I> negatively regulate the expression of <I>Yersinia enterocolitica yop</I> genes. It is demonstrated that <I>yopD</I> and <I>lcrH</I> are required for <I>yscM1</I> and <I>yscM2</I> function and that all four genes act synergistically at the same regulatory step. Further, SycH binding to the protein products of <I>yscM1</I> and <I>yscM2</I> can activate <I>yop</I> gene expression even without promoting type III transport of YscM1 and YscM2. Reverse transcription-PCR analysis of <I>yopQ</I> mRNA as well as <I>yopQ</I> and <I>yopE</I> gene fusion experiments with the <I>npt</I> (neomycin phosphotransferase) reporter suggest that <I>yscM1</I> and <I>yscM2</I> regulate expression at a posttranscriptional step. The 178-nucleotide 5′ untranslated region (UTR) of <I>yopQ</I> mRNA was sufficient to confer <I>yscM1</I> and <I>yscM2</I>-mediated regulation on the fused reporter, as was the 28-nucleotide UTR of <I>yopE</I>. The sequence 5′-AUAAA-3′ is located in the 5′ <I>yop</I> UTRs, and mutations that alter the sequence motif either reduced or abolished <I>yscM1-</I> and <I>yscM2</I>-mediated regulation. A model is proposed whereby YopD, LcrH, YscM1, YscM2, and SycH regulate <I>yop</I> expression in response to specific environmental cues and by a mechanism that may involve binding of some of these factors to a specific target sequence within the UTR of <I>yop</I> mRNAs.</P>
<P>Quorum sensing is a cell-to-cell communication system known to control many bacterial processes. In the present study, the functions of quorum sensing in the pathogenesis of <I>Vibrio vulnificus</I>, a food-borne pathogen, were assessed by evaluating the virulence of a mutant deficient in SmcR, a quorum-sensing regulator and homologue of LuxR. When biofilms were used as an inoculum, the <I>smcR</I> mutant was impaired in virulence and colonization capacity in the infection of mice. The lack of SmcR also resulted in decreased histopathological damage in mouse jejunum tissue. These results indicated that SmcR is essential for <I>V. vulnificus</I> pathogenesis. Moreover, the <I>smcR</I> mutant exhibited significantly reduced biofilm detachment. Upon exposure to INT-407 host cells, the wild type, but not the <I>smcR</I> mutant, revealed accelerated biofilm detachment. The INT-407 cells increased <I>smcR</I> expression by activating the expression of LuxS, an autoinducer-2 synthase, indicating that host cells manipulate the cellular level of SmcR through the quorum-sensing signaling of <I>V. vulnificus</I>. A whole-genome microarray analysis revealed that the genes primarily involved in biofilm detachment and formation are up- and downregulated by SmcR, respectively. Among the SmcR-regulated genes, <I>vvpE</I> encoding an elastolytic protease was the most upregulated, and the purified VvpE appeared to dissolve established biofilms directly in a concentration-dependent manner <I>in vitro</I>. These results suggest that the host cell-induced SmcR enhances the detachment of <I>V. vulnificus</I> biofilms entering the host intestine and thereby may promote the dispersal of the pathogen to new colonization loci, which is crucial for pathogenesis.</P>
<P><I>Brucella abortus</I> is an intracellular pathogen that uses a crafty strategy to invade and proliferate within host cells, but the distinct signaling pathways associated with phagocytic mechanisms of <I>B. abortus</I> remain unclear. The present study was performed to test the hypothesis that Toll-like receptor 4 (TLR4)-linked signaling interacting with Janus kinase 2 (JAK2) plays an essential role in <I>B. abortus</I> phagocytosis by macrophages. The effects of TLR4-JAK2 signaling on <I>B. abortus</I> phagocytosis in murine macrophage RAW 264.7 cells were observed through an infection assay and confocal microscopy. We determined that the uptake of <I>B. abortus</I> was negatively affected by the dysfunction of TLR4 and JAK2. F-actin polymerization detected by flow cytometry and F-actin assay was amplified for <I>B. abortus</I> entry, whereas that event was attenuated by the disruption of TLR4 and JAK2. Importantly, JAK2 phosphorylation and actin skeleton reorganization were suppressed immediately after <I>B. abortus</I> infection in bone marrow-derived macrophages (BMDMs) from TLR4<SUP>−/−</SUP> mice, showing the cooperation of JAK2 with TLR4. Furthermore, small GTPase Cdc42 participated in the intermediate pathway of TLR4-JAK2 signaling on <I>B. abortus</I> phagocytosis. Consequently, TLR4-associated JAK2 activation in the early cellular signaling events plays a pivotal role in <I>B. abortus</I>-induced phagocytic processes in macrophages, implying the pathogenic significance of JAK2-mediated entry. Here, we elucidate that this specific phagocytic mechanism of <I>B. abortus</I> might provide achievable strategies for inhibiting <I>B. abortus</I> invasion.</P>
Cheng, Yang,Wang, Yue,Ito, Daisuke,Kong, Deok-Hoon,Ha, Kwon-Soo,Chen, Jun-Hu,Lu, Feng,Li, Jian,Wang, Bo,Takashima, Eizo,Sattabongkot, Jetsumon,Tsuboi, Takafumi,Han, Eun-Taek American Society for Microbiology 2013 Infection and immunity Vol.81 No.5
<P>Merozoite surface protein 1 of <I>Plasmodium vivax</I> (PvMSP1), a glycosylphosphatidylinositol-anchored protein (GPI-AP), is a malaria vaccine candidate for <I>P. vivax</I>. The paralog of PvMSP1, named <I>P. vivax</I> merozoite surface protein 1 paralog (PvMSP1P; PlasmoDB PVX_099975), was recently identified and predicted as a GPI-AP. The similarities in genetic structural characteristics between PvMSP1 and PvMSP1P (e.g., size of open reading frames, two epidermal growth factor-like domains, and GPI anchor motif in the C terminus) led us to study this protein. In the present study, different regions of the PvMSP1P protein, demarcated based on the processed forms of PvMSP1, were expressed successfully as recombinant proteins [i.e., 83 (A, B, and C), 30, 38, 42, 33, and 19 fragments]. We studied the naturally acquired immune response against each fragment of recombinant PvMSP1P and the potential ability of each fragment to bind erythrocytes. The N-terminal fragment (83A) and two C-terminal fragments (33 and 19) reacted strongly with sera from <I>P. vivax</I>-infected patients, with 50 to 68% sensitivity and 95 to 96% specificity, respectively. Due to colocalization of PvMSP1P with PvMSP1, we supposed that PvMSP1P plays a similar role as PvMSP1 during erythrocyte invasion. An <I>in vitro</I> cytoadherence assay showed that PvMSP1P, especially the 19-kDa C-terminal region, could bind to erythrocytes. We also found that human sera from populations naturally exposed to vivax malaria and antisera obtained by immunization using the recombinant molecule PvMSP1P-19 inhibited <I>in vitro</I> binding of human erythrocytes to PvMSP1P-19. These results provide further evidence that the PvMSP1P might be an essential parasite adhesion molecule in the <I>P. vivax</I> merozoite and is a potential vaccine candidate against <I>P. vivax</I>.</P>
<P>Intestinal epithelial activation of nuclear factor kappa B (NF-κB) exerts both detrimental and beneficial functions in response to various luminal insults, including ones associated with mucosa-associated pathogens. Gastrointestinal infection with enteropathogenic <I>Escherichia coli</I> (EPEC) causes severe injuries in epithelial integrity and leads to watery diarrhea. The present study was conducted to investigate the prolonged epithelial responses to persistent EPEC infection via NF-κB activation. EPEC infection led to sustained activation of NF-κB signal in mouse intestinal epithelial cells <I>in vivo</I> and <I>in vitro</I>, which was positively associated with a type III secretion system, whereas early NF-κB is regulated. Moreover, prolonged NF-κB activation was found to be a part of macrophage inhibitory cytokine 1 (MIC-1)-mediated signaling activation, a novel link between NF-κB signaling and infection-associated epithelial stress. EPEC infection induced gene expression of MIC-1, a member of the transforming growth factor β (TGF-β) superfamily, which then activated TGF-β-activated kinase 1 and consequently led to NF-κB activation. Functionally, both EPEC-induced MIC-1 and NF-κB signaling mediated epithelial survival by enhancing the expression of cyclin D1, a target of NF-κB. In summary, the results of the present study suggest that MIC-1 serves as a mediator of prolonged NF-κB activation, which is critical in maintaining gut epithelial integrity in response to infection-induced injuries.</P>
<P>In the gammaproteobacteria, the FeoA, FeoB, and FeoC proteins constitute the Feo system, which mediates ferrous iron [Fe(II)] import. Of these Feo proteins, FeoB is an inner membrane Fe(II) transporter that is aided by the small protein FeoA. However, the role of another small protein, FeoC, has remained unknown. Here we report that the FeoC protein is necessary for FeoB protein-mediated Fe(II) uptake in <I>Salmonella</I> experiencing low levels of oxygen and iron. The FeoC protein was found to directly bind to the FeoB transporter, leading to high cellular levels of FeoB. Depletion of the FtsH protease enabled high levels of FeoB in the absence of FeoC, suggesting that the FeoC protein protects the FeoB transporter from FtsH-mediated proteolysis. Our present study provides a singular example of bacteria that can control expression of iron uptake systems posttranslationally by employing a small iron transporter-binding protein.</P>
<P><I>Deinococcus radiodurans</I> R1 exposed to a lethal dose of cadmium shows differential expression of a large number of genes, including <I>frnE</I> (dr<I>frnE</I>) and some of those involved in DNA repair and oxidative stress tolerance. The dr<I>frnE</I>::<I>nptII</I> mutant of <I>D. radiodurans</I> showed growth similar to that of the wild type, but its tolerance to 10 mM cadmium and 10 mM diamide decreased by ∼15- and ∼3-fold, respectively. These cells also showed nearly 6 times less resistance to gamma radiation at 12 kGy and ∼2-fold-higher sensitivity to 40 mM hydrogen peroxide than the wild type. In <I>trans</I> expression of drFrnE increased cytotoxicity of dithiothreitol (DTT) in the <I>dsbA</I> mutant of <I>Escherichia coli</I>. Recombinant drFrnE showed disulfide isomerase activity and could maintain insulin in its reduced form in the presence of DTT. While an equimolar ratio of wild-type protein could protect malate dehydrogenase completely from thermal denaturation at 42°C, the C22S mutant of drFrnE provided reduced protection to malate dehydrogenase from thermal inactivation. These results suggested that drFrnE is a protein disulfide isomerase <I>in vitro</I> and has a role in oxidative stress tolerance of <I>D. radiodurans</I> possibly by protecting the damaged cellular proteins from inactivation.</P>