Phase Variants Research Articles

Mycoplasma genitalium Nonadherent Phase Variants Arise by Multiple Mechanisms and Escape Antibody-Dependent Growth Inhibition.

Antigenic variation of the immunodominant MgpB and MgpC proteins has been suggested to be a mechanism of immune evasion of the human pathogen Mycoplasma genitalium, a cause of several reproductive tract disease syndromes. Phase variation resulting in the loss of adherence has also been documented, but the molecular mechanisms underlying this process and its role in pathogenesis are still poorly understood. In this study, we isolated and characterized 40 spontaneous, nonadherent phase variants from in vitro-passaged M. genitalium cultures. In all cases, nonadherence was associated with the loss of MgpBC protein expression, attributable to sequence changes in the mgpBC expression site. Phase variants were grouped into seven classes on the basis of the nature of the mutation. Consistent with the established role of RecA in phase variation, 31 (79.5%) variants arose via recombination with MgPa repeat regions that contain mgpBC variable sequences. The remaining mutants arose via nonsense or frameshift mutations. As expected, revertants were obtained for phase variants that were predicted to be reversible but not for those that arose via an irreversible mechanism. Furthermore, phase variants were enriched in M. genitalium cultures exposed to antibodies reacting to the extracellular, conserved C terminus of MgpB but not in cultures exposed to antibodies reacting to an intracellular domain of MgpB or the cytoplasmic HU protein. Genetic characterization of the antibody-selected phase variants confirmed that they arose via reversible and irreversible recombination and point mutations within mgpBC These phase variants resisted antibody-mediated growth inhibition, suggesting that phase variation promotes immune evasion.

Phenol Oxidase Activity of Azospirillum brasilense Sp245 Mutants with Modified Motility and Azospirillum brasilense Sp7 Phase Variants with Different Plasmid Composition

Herein, we reveal the alteration in phenol oxidase enzymes complex production from Azospirillum brasilense Sp245 omegon mutants with polar and lateral flagella dysfunction and from A. brasilense Sp7 phase variants with different plasmid composition. The enzymatic activities for various laccases, tyrosinases, Mnperoxidases, and lignin peroxidases as well as the isomorphic composition of intracellular laccases and tyrosinases were estimated for the studied variants and the parent strains. It was noted that various genetic events correlating with phenotypic heterogeneity in A. brasilense populations affect their phenol oxidase activity level.

Harmonic Balance developments in OpenFOAM

The Harmonic Balance method for simulating unsteady nonlinear periodic flows is presented in this paper. Its recent, yet rapid development was motivated by the possibility of significant CPU time consumption savings compared to conventional transient methods, while providing sufficient accuracy.Using the Harmonic Balance method, a single time-continuous primary variable is decomposed into a number of steady state snapshots throughout the representative period, depending on the number of resolved harmonics. Decomposition is done following the Fourier series, yielding the mutually coupled equations where time derivation term is replaced by a coupling source term. Therefore, the decomposition relates to temporal evolution and accounts for transient effects.The numerical method is based on the Finite Volume (FV) method for computational fluid dynamics and was implemented in the open-source software foam-extend. Along with the mathematical model, this work presents the additional derivation of temporal coupling over the interface for cases with more than one domain. With proper mathematical procedure, no additional time-interpolation between interfaces is needed, presenting a novelty in the field.The method is validated in two distinct fields: turbomachinery and naval hydrodynamics. Turbomachinery test cases consist of 2D ERCOFTAC centrifugal pump and a 3D Aachen turbine, for which the comparison with conventional transient and steady state results is performed. For the ERCOFTAC case, CPU time comparison is presented as well. Two phase variant of the Harmonic Balance method is validated on regular wave propagation test case, including the comparison with transient results, which is followed by a DTMB ship hull on waves test case. The two-phase variant of Harmonic Balance represents a novelty in the field of method application. The overall results show the approach is both efficient and accurate, while offering versatility in the area of application.

Design of D0 <sub>22</sub> Superlattice with Superior Strengthening Effect in High Entropy Alloys

Precipitation strengthening is one of the most promising mechanisms to develop high-performance high entropy alloys (HEAs). However, the design of a reinforcing phase with an excellent strengthening effect is still one of the most pivotal challenges. In the present study, a design strategy based on overall valence electron concentration (OVEC) is developed, and a coherent γ″ phase with superior strengthening effect is designed. The newly developed γ″ phase is systematically characterized using transmission electron microscope and atom probe tomography. Differentiating from the traditional Ni3Nb γ″ phase, the present high-entropy γ″ phase contains ~7.7% Co and follows the (Ni,Co,Cr,Fe)3(Nb,Fe) stoichiometry. Three γ″ phase variants are observed with crystallographic orientation relationships of [001]γ″// γ and (001)γ″//{100}γ. The lenticular γ″ particles with small volume fraction (7%) causes a significant yield strength increase (670 MPa) and ductility retention (40%), resulting in excellent yield strength-ductility combination. The excellent strengthening effect of the γ″ phase is attributed to both ordering strengthening and coherency strengthening. The present study proposes a new design strategy of precipitates and develops a superior reinforcing phase for HEAs. These findings not only promote the development of precipitation-strengthened HEAs but deepen the understanding of precipitates design in HEAs as well.

High-resolution electron microscopy characterization of modulated structure in high Nb-containing lamellar γ-TiAl alloy

The microstructure in a lamellar γ-based Ti-45Al-8.5Nb alloy has been investigated by transmission electron microscopy (TEM). The results show that there exists a nano-scale modulated structure with tweed contrast within α2 laths and the orthorhombic phase as a constituent of the modulated structure has the O1 structure with a random occupancy of Ti and Nb atoms on the Wyckoff sites 8 g and 4c2. The orthorhombic phase has a thin plate-like morphology with orientation relationships of {001}O//{0001}α2 and <110>O//<112¯0>α2. The habit plane for orthorhombic phase variants lies at {350}O//{134¯0}α2, and the O1/α2 interface is not atomic flat. The results further exhibit an enrichment of Nb in the orthorhombic phase in comparison with the α2 parent phase. Based on the TEM evidences, the formation of the orthorhombic phase arises from a phase separation reaction in the α2 parent phase, which is dominated by a diffusion mechanism.

Order parameters for symmetry-breaking structural transitions: The tetragonal-monoclinic transition in ZrO2

Group/subgroup structural phase transitions are exploited in a wide variety of technologies, including those that rely on shape-memory behavior and on transformation toughening. Here, we introduce an approach to identify symmetry-adapted strain and shuffle order parameters for any group/subgroup structural transition between a high-symmetry parent phase and its symmetrically equivalent low-symmetry product phases. We show that symmetry-adapted atomic shuffle order parameters can be determined by the diagonalization of an orbital covariance matrix, formed by taking the covariance among the atomic displacement vectors of all symmetrically equivalent product phase variants. We use this approach to analyze the technologically important tetragonal to monoclinic structural phase transformation of ${\mathrm{ZrO}}_{2}$. We explore the energy landscapes, as calculated with density functional theory, along distinct paths that connect $m{\mathrm{ZrO}}_{2}$ to $t{\mathrm{ZrO}}_{2}$ and to other $m{\mathrm{ZrO}}_{2}$ variants. The calculations indicate favorable pairs of variants and reveal intermediate structures likely to exist at coherent twin boundaries and having relatively low deformation energy. We identify crystallographic features of the monoclinic ${\mathrm{ZrO}}_{2}$ variant that make it very sensitive to shape changing strains.

Orientational Equidistance Method for Solving Orientation Relationship From Product Variants: Application to Steel

A three-step procedure has been evolved for finding the orientation relationship (OR) between parent austenite and product ferrite phase, from the room temperature microtexture data of ferritic/martensitic steel. In the first step, the frequently occurring misorientations between product ferrite variants are sought from the electron backscatter diffraction (EBSD) dataset. This is carried out by calculating the ‘misorientation angle-rotation axis’ values across all neighboring pair of ferrite pixels, and plotting them in a parametric space to detect the prominent misorientation peaks. Identification of ‘concurrent relative orientation’ of product variants, i.e., the second step, is resolved by comparing the observed misorientation peak positions with the inter-variant relation set of Kurdjumov–Sachs (KS) OR. The final crucial step of solving the OR based on the ‘Orientational Equidistance’ principle of parent phase from all its product phase variants is implemented in the Rodrigues–Frank parametric space. The procedure is illustrated using an large area EBSD dataset of normalized and tempered 9Cr–1Mo–0.1C steel, and the optimum orientation relation is determined to be ~44.0°[0.151 0.137 0.979], which is 2.4° deviated from KS OR.

Phage exposure causes dynamic shifts in the expression states of specific phase-variable genes of Campylobacter jejuni.

Phase variation (PV) creates phenotypic heterogeneity at high frequencies and in a reversible manner. This phenomenon allows bacteria to adapt to a variety of different environments and selective pressures. In Campylobacterjejuni this reversible adaptive process is mediated by mutations in homopolymeric G/C tracts. Many C. jejuni-specific phages are dependent on phase-variable surface structures for successful infection. We previously identified the capsular polysaccharide (CPS) moiety, MeOPN-GalfNAc, as a receptor for phage F336 and showed that phase-variable expression of the transferase for this CPS modification, cj1421, and two other phase-variable CPS genes generated phage resistance in C. jejuni. Here we investigate the population dynamics of C. jejuni NCTC11168 when exposed to phage F336 in vitro using a newly described method - the 28-locus-CJ11168 PV analysis. Dynamic switching was observed in the ON/OFF states of three phase-variable CPS genes, cj1421, cj1422 and cj1426, during phage F336 exposure, with the dominant phage-resistant phasotype differing between cultures. Although loss of the phage receptor was predominately observed, several other PV events also led to phage resistance, a phenomenon that increases the chance of phage-resistant subpopulations being present in any growing culture. No other PV genes were affected and exposure to phage F336 resulted in a highly specific response, only selecting for phase variants of cj1421, cj1422 and cj1426. In summary, C. jejuni may benefit from modification of the surface in multiple ways to inhibit or reduce phage binding, thereby ensuring the survival of the population when exposed to phages.

Microstructural heterogeneity in rate-dependent plasticity of multiphase titanium alloys

Polycrystalline rate-dependent plasticity is found to originate from heterogeneous slip system/phase rate response. Micro-mechanism under low stress and low temperature (T< 0.3Tm) has been shown to be different from conventional rate sensitivity expectations. Hence the constitutive framework developed is dependent on the crystallographic orientation, properly capturing micro-scale anisotropic rate behaviour.The intrinsic rate anisotropy of the HCP α prism and basal and BCC β phase slip systems in Ti-6242, recently determined from micro-pillar and crystal plasticity modelling, have been utilised to investigate the structural strain rate sensitivities of colonies, polycrystals, bimodal and basket weave microstructures.The rate sensitivity of colony structures is dominated by the HCP α phase behaviour, at least for alloys containing up to ∼20% volume fraction β phase, and is largely independent of β-lath orientation. The apparent anisotropy of a1, a2 and a3 basal resolved shear stresses in Ti-6242 colonies is shown to originate from the local crystal stress states established as opposed to the α−β interfaces.Texture and α−β morphology are shown to affect rate dependence and to corroborate that the basal rate sensitivity is stronger than that for prism slip in Ti-6242. Morphological effects are shown to affect rate dependence but not strongly, but the number of HCP α phase variants in basketweave structures is found to have a significant effect with higher numbers of variants leading to lower strain rate sensitivities. This is potentially important in designing alloys to resist cold dwell fatigue.

Mesomorphism in binary mixtures of 4-((hexylimino)methyl)benzoic acid and 4-alkyloxybenzoic acids

A new non-mesogenic Schiff-based carboxylic acid, viz. 4-((hexylimino)methyl)benzoic acid (HIMB), is synthesized and is used to prepare the binary mixtures with mesogenic 4-n-alkyloxybenzoic acids (nOBAs, where n = 3, 4, 5, 7, 8, 9 and 12) in 1:1 molar ratio. The mesomorphism in HIMB and nOBA mixtures is studied by polarizing optical microscopy and differential scanning calorimetry. The mesomorphic thermal stabilities of these mixtures are found to vary with those of the nOBAs. The results are discussed with the reported mixtures of nOBAs with other Schiff-based pyridyl moieties, which are found to exhibit new phase variants and mesomorphic thermal stabilities. The phase transition temperatures and the enthalpy changes at the phase transitions are discussed in comparison with the other similar binary mixtures. The effects of intermolecular interactions on mesomorphism are discussed.

A novel phase variant of the cholera pathogen shows stress-adaptive cryptic transcriptomic signatures.

BackgroundIn a process known as phase variation, the marine bacterium and cholera pathogen Vibrio cholerae alternately expresses smooth or rugose colonial phenotypes, the latter being associated with advanced biofilm architecture and greater resistance to ecological stress. To define phase variation at the transcriptomic level in pandemic V. cholerae O1 El Tor strain N16961, we compared the RNA-seq-derived transcriptomes among the smooth parent N16961, its rugose derivative (N16961R) and a smooth form obtained directly from the rugose at high frequencies consistent with phase variation (N16961SD).ResultsDifferentially regulated genes which clustered into co-expression groups were identified for specific cellular functions, including acetate metabolism, gluconeogenesis, and anaerobic respiration, suggesting an important link between these processes and biofilm formation in this species. Principal component analysis separated the transcriptome of N16961SD from the other phase variants. Although N16961SD was defective in biofilm formation, transcription of its biofilm-related vps and rbm gene clusters was nevertheless elevated as judged by both RNA-seq and RT-qPCR analyses. This transcriptome signature was shared with N16961R, as were others involving two-component signal transduction, chemotaxis, and c-di-GMP synthesis functions.ConclusionsPrecise turnarounds in gene expression did not accompany reversible phase transitions (i.e., smooth to rugose to smooth) in the cholera pathogen. Transcriptomic signatures consisting of up-regulated genes involved in biofilm formation, environmental sensing and persistence, chemotaxis, and signal transduction, which were shared by N16961R and N16961SD variants, may implicate a stress adaptation in the pathogen that facilitates transition of the N16961SD smooth form back to rugosity should environmental conditions dictate.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3233-x) contains supplementary material, which is available to authorized users.

Phase-Variable Heptose I Glycan Extensions Modulate Efficacy of 2C7 Vaccine Antibody Directed against Neisseria gonorrhoeae Lipooligosaccharide.

Neisseria gonorrhoeae, the causative agent of the sexually transmitted infection, gonorrhea, has developed resistance to most conventional antibiotics. Safe and effective vaccines against gonorrhea are needed urgently. A candidate vaccine that targets a lipooligosaccharide (LOS) epitope recognized mAb 2C7 attenuates gonococcal burden in the mouse vaginal colonization model. Glycan extensions from the LOS core heptoses (HepI and HepII) are controlled by phase-variable LOS glycosyltransferase (lgt) genes; we sought to define how HepI glycan extensions affect mAb 2C7 function. Isogenic gonococcal mutants in which the lgt required for mAb 2C7 reactivity (lgtG) was genetically locked on and the lgt loci required for HepI variation (lgtA, lgtC, and lgtD) were genetically locked on or off in different combinations were created. We observed 100% complement-dependent killing by mAb 2C7 of a mutant that expressed lactose (Gal-Glc) from HepI, whereas a mutant that expressed Gal-Gal-Glc-HepI fully resisted killing (>100% survival). Mutants that elaborated 4- (Gal-GlcNAc-Gal-Glc-HepI) and 5-glycan (GalNAc-Gal-GlcNAc-Gal-Glc-HepI) structures displayed intermediate phenotypes (<50% killing with 2 μg/ml and >95% killing with 4 μg/ml mAb 2C7). The contrasting phenotypes of the lactose-HepI and the Gal-Gal-Glc-HepI LOS structures were recapitulated with phase variants of a recently isolated clinical strain. Despite lack of killing of the Gal-Gal-Glc-HepI mutants, mAb 2C7 deposited sufficient C3 on these bacteria for opsonophagocytic killing by human neutrophils. In conclusion, mAb 2C7 showed functional activity against all gonococcal HepI LOS structures defined by various lgtA/C/D on/off combinations, thereby providing further impetus for use of the 2C7 epitope in a gonococcal vaccine.

Carbohydrate metabolism of the phase variants of purple photosynthetic bacteria

The R and M phase variants of Rhodobacter sphaeroides and Rhodobacter capsulatus were isolated. The growth rates in the dark and in the light in glucose-containing media were much higher for the Rba. sphaeroides R variant than for the M variant. For the Rba. capsulatus R and M variants, growth rates in the dark and in the light in fructose- or glucose-containing media differed insignificantly. The cells of Rba. sphaeroides and Rba. capsulatus phase variants growing in media with glucose and fructose exhibited differences in activity of the key enzymes of the Embden–Meyerhof–Parnas (EMP) and Entner–Doudoroff (ED) pathways. The oxidative pentose phosphate pathway (PPP) does not participate in glucose and fructose metabolism in the studied bacteria. Specific activity of the ED pathway enzymes was higher in dark-grown R and M variants of both Rba. sphaeroides and Rba. capsulatus than in the cells grown under light. Specific activity of the EMP enzymes was higher for the R and M variants of both cultures grown in the light than for those grown in the dark. Activities of the 2-keto-3-deoxy-6-phosphogluconate and fructose bisphosphate aldolases, the key enzymes of the ED and EMP pathways in Rba. sphaeroides M variant grown in the medium with glucose in the light or in the dark, were approximately twice those of the R variant. In the medium with fructose activities of these enzymes in both R and M variants did not change significantly depending on growth conditions. Activities of the enzymes of the EMP and ED pathways in the extracts of the Rba. capsulatus R and M cells grown with glucose or fructose did not change significantly. Cultivation of Rba. sphaeroides and Rba. capsulatus phase variants in the medium with fructose resulted in a considerably increased synthesis of 1-phosphofructokinase. Induction of 1-phosphofructokinase synthesis in Rba. sphaeroides occurred only in the light, while in Rba. capsulatus induction of this enzyme in the medium with fructose was observed both in the dark and in the light. Thus, under aerobic conditions in the dark the phase variants of both bacteria probably assimilated glucose and fructose via the ED pathway, while in the light the EMP pathway was active.

The scratch and abrasive wear behaviour of a tempered martensitic construction steel and its dual phase variants

An experimental investigation of the scratch and abrasive wear behaviour of a lean C–Mn construction steel in its tempered fully martensitic (TM) state is presented. The scratch resistance and the corresponding failure mechanisms as a function of the tempering temperature (200–500°C) were evaluated using a multi-pass dual-indenter (MPDI) scratch test applying different loading conditions. Results show that the scratch resistance depends not only on the tempering temperature, but also on the load applied during scratching. The optimal tempering temperature depends on the applied load. For both low and high loading conditions, the dual phase (ferrite–martensite) variant with an optimised martensite volume fraction and morphology yields an even better combination of scratch/abrasion resistance and hardness. The scratch resistance at different loading conditions is linked to the strength coefficient K in the Hollomon equation (σ=Kεn). The scratch behaviour in the MPDI scratch test at a low load correlates quite well with the standard ASTM G65 multi-particle abrasion test.

Dielectric properties of a highly polar liquid crystalline material showing various types of layered structures

ABSTRACTLiquid crystal compound N-(4-n-pentyloxybenzalidene) 4′-n-pentylaniline is very interesting because of its rich phase variant, i.e. nematic, smectic A, smectic C, smectic F and smectic G phases. In the present work, temperature- and frequency-dependent dielectric studies on this compound in the homeotropic and planar orientation of molecules have been carried out in the frequency range of 1 Hz–10 MHz. The compound shows negative dielectric anisotropy (i.e.Δε < 0). Dielectric studies have shown three relaxation modes of different origin in various phases of the material. Relaxation frequencies of the observed modes follow Arrhenius behaviour. The relaxation due to interfacial polarisation, i.e. Maxwell–Wagner–Sillars effect has been observed in the nematic and isotropic phases. A relaxation mode due to the fluctuation of molecular tilt resembling the soft mode has been detected in the smectic A phase with pre- and post-transitional effects. Another mode due to the fluctuation of molecules about their short axes has been detected in the nematic and smectic A, C, F and G phases. Activation energies and ionic conductivity of these phases have also been determined.

Pitfalls of haplotype phasing from amplicon-based long-read sequencing.

The long-read sequencers from Pacific Bioscience (PacBio) and Oxford Nanopore Technologies (ONT) offer the opportunity to phase mutations multiple kilobases apart directly from sequencing reads. In this study, we used long-range PCR with ONT and PacBio sequencing to phase two variants 9 kb apart in the RET gene. We also re-analysed data from a recent paper which had apparently successfully used ONT to phase clinically important haplotypes at the CYP2D6 and HLA loci. From these analyses, we demonstrate PCR-chimera formation during PCR amplification and reference alignment bias are pitfalls that need to be considered when attempting to phase variants using amplicon-based long-read sequencing technologies. These methodological pitfalls need to be avoided if the opportunities provided by long-read sequencers are to be fully exploited.

Galectin-3 Plays an Important Role in Innate Immunity to Gastric Infection by Helicobacter pylori.

We studied the role of galectin-3 (Gal3) in gastric infection by Helicobacter pylori We first demonstrated that Gal3 was selectively expressed by gastric surface epithelial cells and abundantly secreted into the surface mucus layer. We next inoculated H. pylori Sydney strain 1 into wild-type (WT) and Gal3-deficient mice using a stomach tube. At 2 weeks postinoculation, the bacterial cells were mostly trapped within the surface mucus layer in WT mice. In sharp contrast, they infiltrated deep into the gastric glands in Gal3-deficient mice. Bacterial loads in the gastric tissues were also much higher in Gal3-deficient mice than in WT mice. At 6 months postinoculation,H. pylori had successfully colonized within the gastric glands of both WT and Gal3-deficient mice, although the bacterial loads were still higher in the latter. Furthermore, large lymphoid clusters mostly consisting of B cells were frequently observed in the gastric submucosa of Gal3-deficient mice.In vitro, peritoneal macrophages from Gal3-deficient mice were inefficient in killing engulfed H. pylori Furthermore, recombinant Gal3 not only induced rapid aggregation of H. pylori but also exerted a potent bactericidal effect on H. pylori as revealed by propidium iodide uptake and a morphological shift from spiral to coccoid form. However, a minor fraction of bacterial cells, probably transient phase variants of Gal3-binding sugar moieties, escaped killing by Gal3. Collectively, our data demonstrate that Gal3 plays an important role in innate immunity to infection and colonization of H. pylori.

The Regulation of Secondary Metabolism in Photorhabdus.

A general definition of secondary metabolism is that it consists of the metabolic pathways and the products of metabolism that are not absolutely required for the survival of the organism. Using this definition, it is now well established that Photorhabdus elaborate an extensive secondary metabolism during the post-exponential phase of bacterial growth. This secondary metabolism includes, but is not limited to, the production of light, a stilbene antibiotic and an anthraquinone pigment. In this chapter, the role of secondary metabolism during the life cycle of Photorhabdus will be discussed. Recent work has shown that secondary metabolism in Photorhabdus is required for the mutualistic association between the bacteria and its nematode partner, in particular bacterial secondary metabolism is required to support normal nematode growth and development. An isogenic population of Photorhabdus is phenotypically heterogenous and this facilitates functional partitioning within the population. The relationship between secondary metabolism and the various phenotypic and phase variants that exist in populations of Photorhabdus will also be discussed. Finally, this chapter will also describe the various regulatory nodes that have been identified as being part of the complex regulatory network that is used to control the temporal expression of secondary metabolism in Photorhabdus.

A Novel Interaction between Complement Inhibitor C4b-binding Protein and Plasminogen That Enhances Plasminogen Activation

The complement, coagulation, and fibrinolytic systems are crucial for the maintenance of tissue homeostasis. To date numerous interactions and cross-talks have been identified between these cascades. In line with this, here we propose a novel, hitherto unknown interaction between the complement inhibitor C4b-binding protein (C4BP) and plasminogen of the fibrinolytic pathway. Binding of C4BP to Streptococcus pneumoniae is a known virulence mechanism of this pathogen and it was increased in the presence of plasminogen. Interestingly, the acute phase variant of C4BP lacking the β-chain and protein S binds plasminogen much stronger than the main isoform containing the β-chain and protein S. Indeed, the complement control protein (CCP) 8 domain of C4BP, which would otherwise be sterically hindered by the β-chain, primarily mediates this interaction. Moreover, the lysine-binding sites in plasminogen kringle domains facilitate the C4BP-plasminogen interaction. Furthermore, C4BP readily forms complexes with plasminogen in fluid phase and such complexes are present in human serum and plasma. Importantly, whereas the presence of plasminogen did not affect the factor I cofactor activity of C4BP, the activation of plasminogen by urokinase-type plasminogen activator to active plasmin was significantly augmented in the presence of C4BP. Taken together, our data demonstrate a novel interaction between two proteins of the complement and fibrinolytic system. Most complexes might be formed during the acute phase of inflammation and have an effect on the homeostasis at the site of injury or acute inflammation.

Bioinformatic Analysis of Chlamydia trachomatis Polymorphic Membrane Proteins PmpE, PmpF, PmpG and PmpH as Potential Vaccine Antigens.

Chlamydia trachomatis is the most important infectious cause of infertility in women with important implications in public health and for which a vaccine is urgently needed. Recent immunoproteomic vaccine studies found that four polymorphic membrane proteins (PmpE, PmpF, PmpG and PmpH) are immunodominant, recognized by various MHC class II haplotypes and protective in mouse models. In the present study, we aimed to evaluate genetic and protein features of Pmps (focusing on the N-terminal 600 amino acids where MHC class II epitopes were mapped) in order to understand antigen variation that may emerge following vaccine induced immune selection. We used several bioinformatics platforms to study: i) Pmps’ phylogeny and genetic polymorphism; ii) the location and distribution of protein features (GGA(I, L)/FxxN motifs and cysteine residues) that may impact pathogen-host interactions and protein conformation; and iii) the existence of phase variation mechanisms that may impact Pmps’ expression. We used a well-characterized collection of 53 fully-sequenced strains that represent the C. trachomatis serovars associated with the three disease groups: ocular (N=8), epithelial-genital (N=25) and lymphogranuloma venereum (LGV) (N=20). We observed that PmpF and PmpE are highly polymorphic between LGV and epithelial-genital strains, and also within populations of the latter. We also found heterogeneous representation among strains for GGA(I, L)/FxxN motifs and cysteine residues, suggesting possible alterations in adhesion properties, tissue specificity and immunogenicity. PmpG and, to a lesser extent, PmpH revealed low polymorphism and high conservation of protein features among the genital strains (including the LGV group). Uniquely among the four Pmps, pmpG has regulatory sequences suggestive of phase variation. In aggregate, the results suggest that PmpG may be the lead vaccine candidate because of sequence conservation but may need to be paired with another protective antigen (like PmpH) in order to prevent immune selection of phase variants.