Acute Human Infection Research Articles

Campylobacter jejuni transcriptional and genetic adaptation during human infection.

Campylobacter jejuni infections are a leading cause bacterial food-borne diarrheal illness worldwide, and Campylobacter infections in children are associated with stunted growth and therefore long-term deficits into adulthood. Despite this global impact on health and human capital, how zoonotic C. jejuni responds to the human host remains unclear. Unlike other intestinal pathogens, C. jejuni does not harbor pathogen-defining toxins that explicitly contribute to disease in humans. This makes understanding Campylobacter pathogenesis challenging and supports a broad examination of bacterial factors that contribute to C. jejuni infection. Here we use a controlled human infection model to characterize C. jejuni transcriptional and genetic adaptations in vivo, along with a non-human primate infection model to validate our approach. We found variation in 11 genes is associated with either acute or persistent human infections and include products involved in host cell invasion, bile sensing, and flagella modification, plus additional potential therapeutic targets. Particularly, a functional version of the cell invasion protein A (cipA) gene product is strongly associated with persistently infecting bacteria and we went on to identify its biochemical role in flagella modification. These data characterize the adaptive C. jejuni response to primate infections and suggest therapy design should consider the intrinsic differences between acute and persistently infecting bacteria. Additionally, RNA-sequencing revealed conserved responses during natural host commensalism and human infections. 39 genes were differentially regulated in vivo across hosts, lifestyles, and C. jejuni strains. This conserved in vivo response highlights important C. jejuni survival mechanisms such as iron acquisition and evasion of the host mucosal immune response. These advances highlight pathogen adaptability across host species and demonstrate the utility of multidisciplinary collaborations in future clinical trials to study pathogens in vivo.

Transcriptome analysis of a Pseudomonas aeruginosa sn-glycerol-3-phosphate dehydrogenase mutant reveals a disruption in bioenergetics

Pseudomonas aeruginosa causes acute and chronic human infections and is the major cause of morbidity and mortality in cystic fibrosis (CF) patients. We previously determined that the sn-glycerol-3-phosphate dehydrogenase encoded by glpD plays a larger role in P. aeruginosa physiology beyond its role in glycerol metabolism. To better understand the effect of a glpD mutation on P. aeruginosa physiology we compared the transcriptomes of P. aeruginosa strain PAO1 and the PAO1ΔglpD mutant using RNA-seq analysis. We determined that a null mutation of glpD significantly altered amino acid metabolism in P. aeruginosa and affected the production of intermediates that are channelled into the tricarboxylic acid cycle. Moreover, the loss of glpD induced a general stress response mediated by RpoS in P. aeruginosa. Several other phenotypes observed for the P. aeruginosa glpD mutant include increased persister cell formation, reduced extracellular ATP accumulation and increased heat output. Taken together, these findings implicate sn-glycerol-3-phosphate dehydrogenase as a key player in energy metabolism in P. aeruginosa.

Identification and characterization of neutralization epitopes at VP2 and VP1 of enterovirus A71.

Enterovirus A71 (EV-A71) neutralization escape mutants were generated with monoclonal antibody MAB979 (Millipore). The VP2-T141I and VP1-D14N substitutions were identified. Using reverse genetics, infectious clones with these substitutions were constructed and tested by neutralization assay with immune sera from mice and humans. The N-terminus VP1-14 is more important than EF loop VP2-141 in acute human infection, mainly because it recognised IgM present in acute infection. The N-terminus VP1 could be a useful target for diagnostics and therapeutic antibodies in acute infection.

Sub-minimum inhibitory concentrations of ceftazidime inhibit Pseudomonas aeruginosa biofilm formation.

Pseudomonas aeruginosa exhibits the biofilm mode of growth and causes chronic as well as acute infections in humans. Several reports have shown that the treatments with sub-minimum inhibitory concentrations (sub-MICs) of antimicrobial agents influence biofilm formation by P.aeruginosa. The antibiotic ceftazidime (CAZ) is used to treat P.aeruginosa infections, but few studies have examined the effects of β-lactams on biofilm formation by P.aeruginosa. In this study, we investigated the role of sub-MICs of CAZ in the formation of P.aeruginosa biofilms. 1/4×MIC CAZ reduced the biofilm volume of P.aeruginosa PAO1, as quantified by crystal violet staining. The formation of P.aeruginosa PAO1 biofilms treated with 1/4×MIC CAZ were observed by confocal laser scanning microscopy. They were more heterogeneous than the PAO1 biofilms without CAZ treatment. Furthermore, sub-MICs of CAZ inhibited the twitching motility, which played an important role in mature biofilm formation. 1/4×MIC CAZ also reduced the gene expressions of lecA, lecB, pel and psl, which mediate the adhesion and polysaccharide matrix synthesis of P.aeruginosa. These effects suggest that sub-MICs of CAZ may affect a number of stages of biofilm formation. Investigating the effects of sub-MIC antibiotics on targeted bacterial biofilm may lead to the development of future antibiotic treatment modalities.

A one-step multiplex real-time RT-PCR for the universal detection of all currently known CCHFV genotypes

Crimean-Congo hemorrhagic fever (CCHF) is a fatal disease in humans, which is endemic in many countries of Africa, Southern Asia and Southeastern Europe. It is caused by the Crimean-Congo hemorrhagic fever virus (CCHFV), which is an arthropod-borne virus (arbovirus) transmitted by ixodid ticks, mainly of the genus Hyalomma. Animals like hares, hedgehogs, cattle, camels and small ruminants can become infected without developing clinical signs. Seroconversion occurs after a short viremia of up to two weeks, and thus seroprevalence studies in ruminants can be used to reveal risk areas for the human population. Virus detection by real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) is essential to prove an actual circulation of CCHFV in a country and is also used as diagnostic method for acute human CCHFV infections. In this study, a new universal one-step multiplex real-time RT-qPCR for the sensitive and specific detection of CCHFV is presented. For this purpose, 14 new primers and 2 probes were simultaneously used to detect RNAs representing all six CCHFV genotypes. Additionally, a GC-mirrored sequence within the synthetic RNAs enables the discrimination between true positive samples and unintentional laboratory contaminations. CCHFV negative samples from different animal species and ten different members of the order Bunyavirales were eventually tested to reveal the specificity of the new RT-qPCR.

PA5470 Counteracts Antimicrobial Effect of Azithromycin by Releasing Stalled Ribosome in Pseudomonas aeruginosa.

Pseudomonas aeruginosa causes various acute and chronic infections in humans. Treatment with azithromycin (AZM) has been shown to benefit patients with chronic P. aeruginosa infections. By binding to the exit tunnel of the 50S ribosome, AZM causes ribosome stalling and depletion of the intracellular tRNA pool. It has been shown that AZM is able to kill stationary-phase P. aeruginosa cells and repress quorum sensing-regulated virulence factors as well as swarming motility. In P. aeruginosa, the PA5470 gene encodes a putative peptide chain release factor whose expression is highly induced by macrolide antibiotics. However, its function remains unknown. Here, we found that overexpression of PA5470 increased bacterial tolerance against AZM and alleviated the repression of swarming motility. Ribosome pulldown assays revealed that PA5470 contributes to the release of ribosome stalled by AZM. We further demonstrate that overexpression of PA5470 counteracts AZM-mediated repression of the translation of the quorum sensing regulator RhlR. Overall, our results revealed a novel role of PA5470 in the bacterial response to AZM.

The Role of Infected Cell Proliferation in the Clearance of Acute HBV Infection in Humans.

Around 90–95% of hepatitis B virus (HBV) infected adults do not progress to the chronic phase and, instead, recover naturally. The strengths of the cytolytic and non-cytolytic immune responses are key players that decide the fate of acute HBV infection. In addition, it has been hypothesized that proliferation of infected cells resulting in uninfected progeny and/or cytokine-mediated degradation of covalently closed circular DNA (cccDNA) leading to the cure of infected cells are two major mechanisms assisting the adaptive immune response in the clearance of acute HBV infection in humans. We employed fitting of mathematical models to human acute infection data together with physiological constraints to investigate the role of these hypothesized mechanisms in the clearance of infection. Results suggest that cellular proliferation of infected cells resulting in two uninfected cells is required to minimize the destruction of the liver during the clearance of acute HBV infection. In contrast, we find that a cytokine-mediated cure of infected cells alone is insufficient to clear acute HBV infection. In conclusion, our modeling indicates that HBV clearance without lethal loss of liver mass is associated with the production of two uninfected cells upon proliferation of an infected cell.

Structural basis for clonal diversity of the human T-cell response to a dominant influenza virus epitope

Influenza A virus (IAV) causes an acute infection in humans that is normally eliminated by CD8+ cytotoxic T lymphocytes. Individuals expressing the MHC class I molecule HLA-A2 produce cytotoxic T lymphocytes bearing T-cell receptors (TCRs) that recognize the immunodominant IAV epitope GILGFVFTL (GIL). Most GIL-specific TCRs utilize α/β chain pairs encoded by the TRAV27/TRBV19 gene combination to recognize this relatively featureless peptide epitope (canonical TCRs). However, ∼40% of GIL-specific TCRs express a wide variety of other TRAV/TRBV combinations (non-canonical TCRs). To investigate the structural underpinnings of this remarkable diversity, we determined the crystal structure of a non-canonical GIL-specific TCR (F50) expressing the TRAV13-1/TRBV27 gene combination bound to GIL-HLA-A2 to 1.7 Å resolution. Comparison of the F50-GIL-HLA-A2 complex with the previously published complex formed by a canonical TCR (JM22) revealed that F50 and JM22 engage GIL-HLA-A2 in markedly different orientations. These orientations are distinguished by crossing angles of TCR to peptide-MHC of 29° for F50 versus 69° for JM22 and by a focus by F50 on the C terminus rather than the center of the MHC α1 helix for JM22. In addition, F50, unlike JM22, uses a tryptophan instead of an arginine to fill a critical notch between GIL and the HLA-A2 α2 helix. The F50-GIL-HLA-A2 complex shows that there are multiple structurally distinct solutions to recognizing an identical peptide-MHC ligand with sufficient affinity to elicit a broad anti-IAV response that protects against viral escape and T-cell clonal loss.

Pseudomonas aeruginosa Magnesium Transporter MgtE Inhibits Type III Secretion System Gene Expression by Stimulating rsmYZ Transcription.

Pseudomonas aeruginosa causes numerous acute and chronic opportunistic infections in humans. One of its most formidable weapons is a type III secretion system (T3SS), which injects powerful toxins directly into host cells. The toxins lead to cell dysfunction and, ultimately, cell death. Identification of regulatory pathways that control T3SS gene expression may lead to the discovery of novel therapeutics to treat P. aeruginosa infections. In a previous study, we found that expression of the magnesium transporter gene mgtE inhibits T3SS gene transcription. MgtE-dependent inhibition appeared to interfere with the synthesis or function of the master T3SS transcriptional activator ExsA, although the exact mechanism was unclear. We now demonstrate that mgtE expression acts through the GacAS two-component system to activate rsmY and rsmZ transcription. This event ultimately leads to inhibition of exsA translation. This inhibitory effect is specific to exsA as translation of other genes in the exsCEBA operon is not inhibited by mgtE Moreover, our data reveal that MgtE acts solely through this pathway to regulate T3SS gene transcription. Our study reveals an important mechanism that may allow P. aeruginosa to fine-tune T3SS activity in response to certain environmental stimuli.IMPORTANCE The type III secretion system (T3SS) is a critical virulence factor utilized by numerous Gram-negative bacteria, including Pseudomonas aeruginosa, to intoxicate and kill host cells. Elucidating T3SS regulatory mechanisms may uncover targets for novel anti-P. aeruginosa therapeutics and provide deeper understanding of bacterial pathogenesis. We previously found that the magnesium transporter MgtE inhibits T3SS gene transcription in P. aeruginosa In this study, we describe the mechanism of MgtE-dependent inhibition of the T3SS. Our report also illustrates how MgtE might respond to environmental cues, such as magnesium levels, to fine-tune T3SS gene expression.

Human monoclonal antibodies neutralizing influenza virus A/H1N1pdm09 and seasonal A/H1N1 strains – Distinct Ig gene repertoires with a similar action mechanism

Influenza virus causes acute respiratory infection in humans, and is a major public health concern globally. Antibodies play a central role in host protection against influenza virus. We isolated human monoclonal antibodies (hMAb) 206-2-4 and 201-6-8 by a human hybridoma protocol that neutralized various but distinct influenza virus (IFV) A/H1N1 strains, including 2009 pandemic strains. The half-inhibitory concentration of 206-2-4 and 201-6-8 against A/H1N1pdm09 strains was 2–100ng/mL and 5–20μg/mL, respectively. Prophylactic and therapeutic potencies of 206-2-4 were demonstrated in a mouse model of IFV infection at i.p. dosages of 0.25 and 2.5mg/kg, respectively, suggesting that 206-2-4 is one of the most potent hnMAbs against IFV reported thus far. The Ig genes of 206-2-4 and 201-6-8 were originated from distinct germ line repertoires, and accompanied by 63 and 23 somatic hypermutations, respectively. The hemagglutination inhibitory activity indicated that the mechanism of neutralization was to interfere the virus-receptor interaction. The binding epitope of the two antibodies was mapped to hemagglutinin 1 (HA1) amino acid residues 111–120. Additional interaction between the antibody and the HA1 globular head was necessary for neutralization. Such hnMAbs bearing distinct binding epitope have been rarely reported. The potency is likely due to the coverage of a wide surface area of HA protein by these hnMABs. IFV is a highly variable. Our knowledge on the mechanisms by which these cross-reactive hnMAbs function should help design a novel immunogen for the development of a vaccine effective against broader spectrum of IFV strains.

The road to a more effective influenza vaccine: Up to date studies and future prospects.

Influenza virus causes an acute respiratory infection in humans. Frequent point mutations in the influenza genome and occasional exchange of genetic segments between virus strains help the virus evade the pre-existing immunity, resulting in epidemics and pandemics. Although vaccination is the most effective intervention, mismatches between circulating viruses and vaccine strains reduce vaccine efficacy. Furthermore, current injectable vaccines induce IgG antibodies in serum (which limit progression of influenza symptoms) but not secretory IgA antibodies in the respiratory mucosa (which prevent virus infection efficiently). Therefore, numerous studies have attempted to improve influenza vaccines. The discovery of broadly neutralizing antibodies has progressed research into antigen design. Studies designed to improve vaccine efficacy by changing the vaccine administration route have also been conducted. A thorough understanding of the mechanisms underlying the action of various vaccines is essential if we are to develop a universal influenza vaccine. Therefore, evaluating the quality and quantity of antibodies induced by vaccines, which determine vaccine efficacy, is critical. However, at present vaccine evaluation relies on hemagglutination inhibition tests, which only measure the quantity of antibody produced. Antibody repertoires comprise a set of antibodies with specific genetic or molecular features that correspond to their functions. Genetically and functionally similar antibodies may be produced by multiple individuals exposed to an identical stimulus. Therefore, it may be possible to evaluate and compare multiple vaccine strategies in terms of the quality and quantity of an antibody response induced by a vaccine by examining antibody repertoires. Recent studies have used single cell expression and high-throughput immunoglobulin sequencing to provide a detailed picture of antibody responses. These novel methods may be critical for detailed characterization of antibody repertoires induced by various vaccination strategies.

Quantifying Vibrio cholerae Enterotoxicity in a Zebrafish Infection Model.

Vibrio cholerae is the etiological agent of cholera, an acute intestinal infection in humans characterized by voluminous watery diarrhea. Cholera is spread through ingestion of contaminated food or water, primarily in developing countries that lack the proper infrastructure for proper water and sewage treatment. Vibrio cholerae is an aquatic bacterium that inhabits coastal and estuarine areas, and it is known to have several environmental reservoirs, including fish. Our laboratory has recently described the use of the zebrafish as a new animal model for the study of V. cholerae intestinal colonization, pathogenesis, and transmission. As early as 6 h after exposure to V. cholerae, zebrafish develop diarrhea. Prior work in our laboratory has shown that this is not due to the action of cholera toxin. We hypothesize that accessory toxins produced by V. cholerae are the cause of diarrhea in infected zebrafish. In order to assess the effects of accessory toxins in the zebrafish, it was necessary to develop a method of quantifying diarrheal volume as a measure of pathogenesis. Here, we have adapted cell density, protein, and mucin assays, along with enumeration of V. cholerae in the zebrafish intestinal tract and in the infection water, to achieve this goal. Combined, these assays should help us determine which toxins have the greatest diarrheagenic effect in fish and, consequently, which toxins may play a role in environmental transmission.IMPORTANCE Identification of the accessory toxins that cause diarrhea in zebrafish can help us understand more about the role of fish in the wild as aquatic reservoirs for V. cholerae It is plausible that accessory toxins can act to prolong colonization and subsequent shedding of V. cholerae back into the environment, thus perpetuating and facilitating transmission during an outbreak. It is also possible that accessory toxins help to maintain low levels of intestinal colonization in fish, giving V. cholerae an advantage when environmental conditions are not optimal for survival in the water. Studies such as this one are critical because fish could be an overlooked source of cholera transmission in the environment.

Immunogenicity of mumps virus vaccine candidates matching circulating genotypes in the United States and China

Mumps virus (MuV) causes acute infection in humans with characteristic swelling of the parotid gland. While vaccination has greatly reduced the incidence of MuV infection, there have been multiple large outbreaks of mumps virus (MuV) in highly vaccinated populations. The most common vaccine strain, Jeryl Lynn, belongs to genotype A, which is no longer a circulating genotype. We have developed two vaccine candidates that match the circulating genotypes in the United States (genotype G) and China (genotype F). We found that there was a significant decrease in the ability of the Jeryl Lynn vaccine to produce neutralizing antibody responses to non-matched viruses, when compared to either of our vaccine candidates. Our data suggests that an updated vaccine may allow for better immunity against the circulating MuV genotypes G and F.

Simultaneous development of Kawasaki disease following acute human adenovirus infection in monozygotic twins: A case report

BackgroundThe etiology of Kawasaki disease (KD) remains unknown. However, many studies have suggested that specific genetic factors and/or some infectious agents underlie the onset of KD. Previous studies have suggested that human adenovirus (HAdV) is one of the triggering pathogens of KD. Here, we report monozygotic twin boys who sequentially developed KD in conjunction with acute HAdV type 3 (HAdV-3) infection.Case presentationThe patients were four-year-old monozygotic twin boys. The elder brother developed a high fever and was diagnosed with HAdV infection with an immunochromatographic kit for HAdV (IC-kit). He was transferred to our institute after persistent fever for 7 days. On admission, he already fulfilled all the diagnostic criteria for KD. His laboratory data were as follows: WBC, 9700/μl; CRP, 2.42 mg/dl; IFN-γ, 99.8 pg/ml; and TNF-α, 10.9 pg/ml. He received intravenous immunoglobulin (IVIG) and aspirin and responded well, with no coronary artery abnormalities. The younger brother, who was also IC-kit-positive, was hospitalized on the same day as his elder brother after persistent fever for 3 days. His data on admission were as follows: WBC, 12,600/μl; CRP, 5.54 mg/dl; IFN-γ, 105.0 pg/ml; and TNF-α, 33.6 pg/ml. Although he developed all of the typical KD symptoms by day 4, his fever subsided spontaneously on day 6 without IVIG or aspirin. However, he developed a dilation of the coronary artery in the region of the left circumflex artery bifurcation on day 10. His coronary artery dilation had resolved 3 months after onset. HAdV-3 DNA was detected with PCR in stool samples from both patients, and HAdV3 was isolated from the younger brother’s stool sample. Serum neutralizing antibodies to AdV3 were also significantly elevated in both patients, suggesting seroconversion.ConclusionsThere have been few reports of the simultaneous development of KD in monozygotic twins. Notably, both twins had an acute HAdV-3 infection immediately before they developed KD. These cases strongly suggest that KD was triggered by HAdV-3 infection, and they indicate that specific immune responses to some pathogens (such as HAdV-3), arising from genetic susceptibility, play a critical role in the pathogenesis of KD.

180-Nucleotide Duplication in the G Gene of Human metapneumovirus A2b Subgroup Strains Circulating in Yokohama City, Japan, since 2014.

Human metapneumovirus (HMPV), a member of the family Paramyxoviridae, was first isolated in 2001. Seroepidemiological studies have shown that HMPV has been a major etiological agent of acute respiratory infections in humans for more than 50 years. Molecular epidemiological, genetic, and antigenetic evolutionary studies of HMPV will strengthen our understanding of the epidemic behavior of the virus and provide valuable insight for the control of HMPV and the development of vaccines and antiviral drugs against HMPV infection. In this study, the nucleotide sequence of and genetic variations in the G gene were analyzed in HMPV strains prevalent in Yokohama City, in the Kanto area, Japan, between January 2013 and June 2016. As a part of the National Epidemiological Surveillance of Infectious Diseases, Japan, 1308 clinical specimens (throat swabs, nasal swabs, nasal secretions, and nasal aspirate fluids) collected at 24 hospitals or clinics in Yokohama City were screened for 15 major respiratory viruses with a multiplex reverse transcription–PCR assay. HMPV was detected in 91 specimens, accounting for 7.0% of the total specimens, and the nucleotide sequences of the G genes of 84 HMPV strains were determined. Among these 84 strains, 6, 43, 10, and 25 strains were classified into subgroups A2a, A2b, B1, and B2, respectively. Approximately half the HMPV A2b subgroup strains detected since 2014 had a 180-nucleotide duplication (180nt-dup) in the G gene and clustered on a phylogenic tree with four classical 180nt-dup-lacking HMPV A2b strains prevalent between 2014 and 2015. The 180nt-dup causes a 60-amino-acid duplication (60aa-dup) in the G protein, creating 23–25 additional potential acceptor sites for O-linked sugars. Our data suggest that 180nt-dup occurred between 2011 and 2013 and that HMPV A2b strains with 180nt-dup (A2b180nt-dup HMPV) became major epidemic strains within 3 years. The detailed mechanism by which the A2b180nt-dup HMPV strains gained an advantage that allowed their efficient spread in the community and the effects of 60aa-dup on HMPV virulence must be clarified.

Early type I Interferon response induces upregulation of human β-defensin 1 during acute HIV-1 infection.

HIV-1 is able to evade innate antiviral responses during acute infection to establish a chronic systemic infection which, in the absence of antiretroviral therapy (ART), typically progresses to severe immunodeficiency. Understanding these early innate immune responses against HIV-1 and their mechanisms of failure is relevant to the development of interventions to better prevent HIV-1 transmission. Human beta defensins (HBDs) are antibacterial peptides but have recently also been associated with control of viral replication. HBD1 and 2 are expressed in PBMCs as well as intestinal tissue, but their expression in vivo during HIV-1 infection has not been characterized. We demonstrate that during acute HIV-1 infection, HBD1 but not HBD2 is highly upregulated in circulating monocytes but returns to baseline levels during chronic infection. HBD1 expression in monocytes can be induced by HIV-1 in vitro, although direct infection may not entirely account for the increase in HBD1 during acute infection. We provide evidence that HIV-1 triggers antiviral IFN-α responses, which act as a potent inducer of HBD1. Our results show the first characterization of induction of an HBD during acute and chronic viral infection in humans. HBD1 has been reported to have low activity against HIV-1 compared to other defensins, suggesting that in vivo induced defensins may not significantly contribute to the robust early antiviral response against HIV-1. These data provide important insight into the in vivo kinetics of HBD expression, the mechanism of HBD1 induction by HIV-1, and the role of HBDs in the early innate response to HIV-1 during acute infection.

Campylobacter concisus as the etiologic agent of gastrointestinal diseases.

A number of reports on the pathogenic influence of Campylobacter concisus on the human body and its role in many diseases of the gastrointestinal system, including gastroesophageal reflux disease, Barrett's esophagus and inflammatory bowel disease, have appeared lately. Campylobacter concisus is a Gram negative bacteria which requires an anaerobic environment or microaerophilic environment with hydrogen for growth and is therefore difficult to culture. Due to this difficulty, the rate of infections in epidemiological data are underestimated. There are reports that C. concisus was the only pathogen isolated from the stool of patients with acute diarrhea, which could indicate that it is an etiologic factor of acute gastrointestinal infections in humans. Moreover, the results of some studies suggest that infection with C. concisus is a factor predisposing to the development of gastroesophageal reflux disease and Barrett's esophagus, conditions which may be present before the development of cancer. There are also studies which indicate C. concisus infection as a trigger of inflammatory bowel disease, since it has been demonstrated that C. concisus is present more frequently in patients with newly diagnosed Crohn's disease than in a control group.

Pathogenic factors of Pseudomonas aeruginosa - the role of biofilm in pathogenicity and as a target for phage therapy.

Pseudomonas aeruginosa is an opportunistic pathogen that can cause several acute and chronic infections in humans, and it has become an important cause of nosocomial infections and antibiotic resistance. Biofilm represents an important virulence factor for these bacteria, plays a role in P. aeruginosa infections and avoidance of immune defence mechanisms, and has the ability to protect the bacteria from antibiotics. Alginate, Psl and Pel, three exopolysaccharides, are the main components in biofilm matrix, with many biological functions attributed to them, especially with respect to the protection of the bacterial cell from antibiotics and the immune system. Pseudomonas infections, biofilm formation and development of resistance to antibiotics all require better understanding to achieve the best results using alternative treatment with phage therapy. This review describes the P. aeruginosa pathogenicity and virulence factors with a special focus on the biofilm and its role in infection and resistance to antibiotics and summarizes phage therapy as an alternative approach in treatment of P. aeruginosa infections.

Influenza A Viruses Replicate Productively in Mouse Mastocytoma Cells (P815) and Trigger Pro-inflammatory Cytokine and Chemokine Production through TLR3 Signaling Pathway.

The influenza A viruses (IAVs) cause acute respiratory infection in both humans and animals. As a member of the initial lines of host defense system, the role of mast cells during IAV infection has been poorly understood. Here, we characterized for the first time that both avian-like (α-2, 3-linked) and human-like (α-2, 6- linked) sialic acid (SA) receptors were expressed by the mouse mastocytoma cell line (P815). The P815 cells did support the productive replication of H1N1 (A/WSN/33), H5N1 (A/chicken/ Henan/1/04) and H7N2 (A/chicken/Hebei/2/02) in vitro while the in vivo infection of H5N1 in mast cells was confirmed by the specific staining of nasal mucosa and lung tissue from mice. All the three viruses triggered the infected P815 cells to produce pro-inflammatory cytokines and chemokines including IL-6, IFN-γ, TNF-α, CCL-2, CCL-5, and IP-10, but not the antiviral type I interferon. It was further confirmed that TLR3 pathway was involved in P815 cell response to IAV-infection. Our findings highlight the remarkable tropism and infectivity of IAV to P815 cells, indicating that mast cells may be unneglectable player in the development of IAV infection.

A study on the efficacy of the recombinant Yersinia adhesin A vaccine against yersiniosis in the early phase.

Yersinia pseudotuberculosis (Y. ptb) is a zoonotic pathogenic bacterial species of the family Enterobacteriaceae and causes yersiniosis, an acute intestinal infection in humans and animals. Y. ptb is often implicated in lethal epidemics in zoo animals and reductions in the breeding population, but a valid prevention method has not been established. Therefore, this study aimed to develop a vaccine for yersiniosis control. The immunogenicity of one of the adhesion factors involved in pathogenic mechanisms of Y. ptb, Yersinia adhesin A (YadA), was investigated. BALB/c mice were divided into 3 groups: in group 1, mice received insoluble recombinant YadA (rYadA) produced in genetically engineered Escherichia coli (100 µg/dose); in group 2, mice received inactivated Y. ptb with strong expression of YadA (20 mg/dose);and in group 3, mice received phosphate-buffered saline (0.2 ml/dose). All interventions were administered subcutaneously twice at an interval of 1 week. One week after the second administration, Y. ptb (107 cells/mouse) was inoculated orally. As a result, the survival rate was 100% in group 1, 60% in group 2, and 0% in group 3. The anti-YadA antibody titer increased in a stepwise fashion in groups 1 and 2. The present study results suggest that rYadA shows promise as a protective antigen against yersiniosis. This study concluded that vaccination against Y. ptb may become available as a new method to prevent lethal epidemics in animals.