Evader's Strategy Research Articles

Winning conditions for evading into a circular region with speed advantage

AbstractIn this study, we consider a two‐player pursuit‐evasion game in which an evader attempts to evade into a circular region while a pursuer along the boundary of this region aims at intercepting the evader. The evader is considered to possess a higher speed than that of the pursuer, which makes this study different from the existing ones. Both the players are assumed to have constant speeds and simple motions; that is, they can change their moving directions instantaneously. The sufficient conditions for the evader to win the game against the pursuer with a zero capture radius or a positive capture radius are proposed using geometric methods. In addition, both the evading strategies under the corresponding derived conditions against the pursuer are developed.

Mycobacterium tuberculosis protein PPE15 (Rv1039c) possesses eukaryote-like SH3 domain that interferes with NADPH Oxidase assembly and Reactive Oxygen Species production

Inhibition of Reactive Oxygen Species (ROS) is one of the strategies that Mycobacterium tuberculosis (Mtb) employs as its defence mechanism. In this study, the role of PPE15 (Rv1039c), a late-stage protein, has been investigated in modulating the cellular ROS. We discovered PPE15 to be a secretory protein that downregulates ROS generation in THP1 macrophages. Our in-silico analysis revealed the presence of a eukaryote-like SH3 (SH3e) domain in PPE15. The predicted SH3e-domain of PPE15 was found to interact with cytosolic components of NADPH Oxidase (NOX), p67phox and p47phox through molecular docking. In-vitro experiments using THP1 macrophages showed a diminished NADP/NADPH ratio, indicating reduced NOX activity. We also observed increased levels of p67phox and p47phox in the cytoplasmic fraction of PPE15 treated macrophages as compared to the plasma membrane fraction. To understand the role of the SH3e-domain in ROS modulation, this domain was deleted from the full-length PPE15 (PPE15-/-SH3). We observed an increase in cellular ROS and NADP/NADPH ratio in response to PPE15-/-SH3 protein. The interaction of PPE15-/-SH3 with p67phox or p47phox was also reduced in the cytoplasm, indicating migration of NOX subunits to the plasma membrane. Additionally, M. smegmatis expressing PPE15 was observed to be resistant to oxidative stress with significant intracellular survival in THP1 macrophages as compared to M. smegmatis expressing PPE15-/-SH3. These observations suggest that the SH3e-domain of PPE15 interferes with ROS generation by sequestering NOX components that inhibit NOX assembly at the cell membrane. Therefore, PPE15 acts like a molecular mimic of SH3-domain carrying eukaryotic proteins that can be employed by Mtb at late stages of infection for its survival. These findings give us new insights about the pathogen evading strategy of Mtb which may help in improving the therapeutics for TB treatment.

Bacterial biofilm formation and anti-biofilm strategies

Bacteria are ubiquitous prokaryotes. They are involved in biofilm formation and also have the ability to produce anti-biofilm products for biofilm mitigation. This special issue entitled: “Biofilms- community structure, applications and mitigation” of the journal Research in Microbiology was designed to discuss the flexibility of bacterial biofilms and their products under particular circumstances. Given that quorum sensing (QS) controls biofilm growth in some situations, especially for pathogenic bacteria antibiotic evading strategies. In Gram-negative bacteria, N-acyl homoserine lactones are the major quorum sensing signaling molecules. Another approach to prevent bacterial biofilm formation may be to inhibit the QS-regulated activities using quorum quenching (QQ). In this context, QS inhibitors and QS enzymes are important because they, respectively, interfere with signal creation, perception, or degradation and chemical modification. There have been numerous reports of QQ enzymes from bacteria. Treatment failure and recurrent staphylococcal infections are also brought on by biofilm development, which boosts an organism's ability to withstand antibiotics and is thought to be a virulence factor in patients. However, polyphenol quercetin antibiofilm activity is naturally available against drug-resistant Staphylococcus aureus.

Predation and theft: the standing threats of the scavenging chicken production system

Indigenous Village Chickens (IVCs) obtain most of their feed from a scavenging feed resource base. Free roaming makes IVCs express their instincts at will, which could enhance their welfare. Free-ranging has also endowed IVCs with excellent explorative behavior. However, predators might have also co-evolved, which necessitates special interference from smallholder farmers to reduce the adverse impact of predators. This study identified the main predators of IVCs and the evading strategies adopted by smallholder farmers. This cross-sectional study involved a general interview with 119 smallholder farmers. The prevalence of enset, Ensete ventricosum (Welw.) Cheesman, around the farmer's backyard can impose a significant threat because it shelters terrestrial predators. Smallholder farmers evade predators through patrolling, guarding dogs, fencing, confinement, and, in rare cases, killing. An unplanned conversation made with an informant revealed that men with some clerical ability but no priesthood title incantate on whole grains of black wheat. When the chicken is fed this grain, reportedly, the aerial predator becomes weak and cannot catch the chicken. The agroecological zone has a statistically significant impact on the proportions of predators encountered and the types of evading strategies adopted by smallholder farmers. This association entails the need for developing agroecology-based predator-evading methods. Predators' evading methods, however, need to be refined further to reduce the recurrent losses of chickens. The threats associated with predators' challenges must be thoroughly investigated to advance their evading strategies. Another problem that leads to the significant loss of family poultry is theft. In addition to the strategies used to avoid predators, which may also apply to controlling theft, the legal system must be well-organized to punish such misdeeds.

Upgrading the non-gene-editing, allogeneic ThisCART platform for extending persistence in vivo.

e14569 Background: Lack of in vivo persistence is the major challenge in allogeneic CAR-T field. Various HLA-related gene-editing strategies are being explored to prevent rejection by host T and NK cells (Table 1). This study reports a platform upgrade on ThisCART (TCR and HLA-I intracellular sequestered), represented by ThisCART19C cells. Methods: ThisCART19C cells were produced with a single lentivirus vector, encoding a CD19-targeting CAR, a KDEL-tagged anti-CD3 scFv, and the HCMV US11 protein. The surface expression of CAR19, TCRαβ and HLA-A/B/E was measured by flow cytometer. Specific tumor cytotoxicity was evaluated both in vitro and in vivo. Furthermore, the safety of donor derived ThisCART19C cells were tested in a xenogeneic GvHD model. Results: Similar to our ThisCART19A product currently in multi-center trials, ThisCART19C cells were readily produced to a quantity and quality supporting clinical investigation. ThisCART19C cells demonstrated an anticipated and stable surface immunotype: CAR19+, TCRαβ-, HLA-A-, HLA-B-，HLA-E+，with great potential for simultaneous evasion of both host T and NK cells. Similar to autologous CD19-directed CAR-T, ThisCART19C exhibited potent CD19-specific cytotoxicity in vitro and in vivo. No xenogeneic GvHD reaction was observed in murine model over an extended period. Conclusions: To our knowledge, ThisCART19C represents the first application of viral evading strategy in promoting the clinical persistence of allogeneic CAR-T cells. Its efficient processing, potent cytotoxicity and favored preclinical safety profile warrant clinical investigation. [Table: see text]

Molecular mechanisms of Phytophthora sojae avirulence effectors escaping host recognition.

Phytophthora sojae is a well-known destructive oomycete pathogen, which causes soybean stem and root rot and poses a serious threat to global food security. Growing soybean cultivars with the appropriate resistance to P. sojae (Rps) genes are the primary management strategy to reduce losses. In most Phytophthora pathosystems, host resistance protein encoded by a specific R gene in the plant recognizes corresponding RxLR effector protein, encoded by an avirulence gene. This gene-for-gene relationship has been exploited to help breeders and agronomists deploy soybean cultivars. To date, 6 Rps genes have been incorporated into commercial soybean germplasm and trigger plant immunity in response to 8 P. sojae avirulence effectors. The incorporation of Rps genes in the soybean population creates selection pressure in favor of novel pathotypes of P. sojae. The 8 avirulence genes evolved to evade the host immune system, driven by genetic selection pressures. Understanding the evading strategies has important reference value for the prevention and control of Phytophthora stem and root rot. This investigation primarily highlights the research on the strategies of P. sojae avirulence effector evasion of host recognition, looking forward to creating durable resistance genes and thereby enabling successful disease management.

Worst-Case Scenario Evasive Strategies in a Two-on-One Engagement Between Dubins’ Vehicles With Partial Information

In this letter, we consider the problem of pursuit-evasion between two pursuers against an evader with the agents modelled as Dubins’ vehicle and having partial information regarding each other’s motion. A novel, two-phase, evasive strategy based on worst-case scenario planning and proximity-based maneuvers is proposed. In the first phase, the evader assumes the pursuers to be holonomic and executes a best response strategy. An analytic and geometric approach is used to obtain the evader’s strategy. In the second phase, the evader switches to movement along high-curvature paths to side-step the pursuers when they are in proximity of the evader in an attempt to delay capture. We also propose an approximation to compute the evader strategy in the first phase, which enables it to be applicable against multiple non-holonomic pursuers. Illustrative simulation results are given.

Cooperative guidance laws for interception of active maneuvering target under information symmetric and asymmetric conditions

This paper proposes novel cooperative guidance strategies with dynamic game properties for a group of interceptors to intercept an active intelligent maneuvering target under both information symmetric and asymmetric conditions. A novel differential game guidance law is proposed to intercept the target with an active maneuvering strategy based on relative distances, relative velocities, and remaining flight time under information symmetric conditions. In the case where the team of interceptors has information superiority, a reasonable evading strategy is designed for the target, and a cooperative optimal guidance law is proposed for interceptors taking the target's evading strategy into consideration. When neither side has the knowledge of the opponent's maneuvering strategy, a novel robust adaptive interception guidance law is designed based on the reduction of the surrounding area regarding the target's maneuver as unknown disturbances. Numerical simulations are carried out to illustrate the effectiveness and superiority of proposed cooperative guidance laws.

Min–Max Q-learning for multi-player pursuit-evasion games

In this paper, we address a pursuit-evasion game involving multiple players by utilizing tools and techniques from reinforcement learning and matrix game theory. In particular, we consider the problem of steering an evader to a goal destination while avoiding capture by multiple pursuers, which is a high-dimensional and computationally intractable problem in general. In our proposed approach, we first formulate the multi-agent pursuit-evasion game as a sequence of discrete matrix games. Next, in order to simplify the solution process, we transform the high-dimensional state space into a low-dimensional manifold and the continuous action space into a feature-based space, which is a discrete abstraction of the original space. Based on these transformed state and action spaces, we subsequently employ min–max Q-learning, to generate the entries of the payoff matrix of the game, and subsequently obtain the optimal action for the evader at each stage. Finally, we present extensive numerical simulations to evaluate the performance of the proposed learning-based evading strategy in terms of the evader’s ability to reach the desired target location without being captured, as well as computational efficiency.

Pursuer Coordination in Multi-Player Reach-Avoid Games Through Control Barrier Functions

This letter addresses the problem of coordinating a team of pursuers to capture a fast evader in reach-avoid games. Coordination is achieved through the minimization of a locational cost objective, which results in a coverage control strategy. Coverage control dynamics are equivalently expressed as consensus dynamics. This formulation is used to guarantee optimal coverage of an implicit defense manifold without needing to rely on projection mappings as in previous works. Control barrier functions (CBFs) are used to guarantee the existence of a pursuer-defendable defense manifold for as long as feasible throughout the engagement and guarantee capture. A greedy evader strategy is proposed in terms of the solution to a quadratically constrained quadratic program, and simulation results are presented comparing the performance of an uncoordinated strategy and a pure coverage strategy to the proposed coordinated CBF strategy.

THE COMPLIMENT RESPONSES USED BY MAKASSARESE NATIVE SPEAKER

Compliment responses are one of speech act types in pragmatic study. This study is aimed (1) to investigate the strategies used by the American and Makassarese people in responding to the complim ent, (2) to compare the response tendencies used by American and the Makassarese people based on Gender and age; and (3) to investigate the cultural influences on the American and Makassarese response.The research was a comparative study which and used a descriptive- qualitative approach. The data were collected from youtube.com and DCT questionnaire. The data were analyzed using a number of techniques, namely noting down the utterances, categorizing the responses identified based on Holmes’ semantic formula and explaining the cultural influences based on their responses. Firstly, the research result revealed that both the American and Makassarese people used 3 compliment strategies: accepting, evading and refusing. Americans would use the evading strategy when the speaker and his interlocutor were good friends; while a Makassarese would either use the evading strategy or the refusing strategy in his responses, when the speaker and his interlocutor were of a different kinship hierarchy, such as between the older and the younger brothers or sisters and between husband and wife. Secondly, The comparison of the compliment responses between the American and Makassarese males indicated that an American male had the tendency to evade a compliment in every topic except teenager had tendency to accept the compliment in any topic. While a Makassarese male tend to receive the compliment for all the topics, except for the comp liment for an achievement.on the other hand, an American woman had tendency to accept a compliment for all topics, but an older woman had a tendency to refuse a compliment. a Makassarese woman, had also a tendency to accept a compliment for all topics. Finally, Makassarese people, both men and women had the tendency to accept, evade or refuse compliments when they had kinship.

Cooperative Pursuit by Multiple Pursuers of a Single Evader

This paper considers pursuit-evasion differential games in the Euclidean plane where an evader is engaged by multiple pursuers and point capture is required. The players have simple motion (i.e., holonomic) in the manner of Isaacs, and the pursuers are faster than the evader. The attention of this paper is confined to the case where the pursuers have the same speed, and so the game’s parameter is that the evader/pursuers speed ratio is . State feedback capture strategies and an evader strategy that yields a lower bound on his/her time-to-capture are devised using a geometric method. It is shown that, in group/swarm pursuit, when the players are in general position, capture is effected by one, two, or three critical pursuers, and this is irrespective of the size of the pursuit pack. Group pursuit devolves into pure pursuit by one of the pursuers or into a pincer movement pursuit by two or three pursuers who isochronously capture the evader. The critical pursuers are identified. However, these geometric method-based pursuit and evasion strategies are optimal only in a part of the state space where a strategic saddle point is obtained and the value of the differential game is established. As such, these strategies are suboptimal. To fully explore the differential game’s high-dimensional state space and get a better understanding of group pursuit, numerical experimentation is undertaken. The state space region where the geometric solution of the group pursuit differential game is the optimal solution becomes larger the smaller the speed ratio parameter is.

Optimal Evading Strategies and Task Allocation in Multi-player Pursuit–Evasion Problems

Pursuit–evasion problems involving multiple pursuers and evaders are studied in this paper. The pursuers and the evaders are all assumed to be identical, and the pursuers are assumed to follow either a constant bearing or a pure pursuit strategy, giving rise to two distinct cases. The problem is simplified by adopting a dynamic divide and conquer approach, where at every time instant each evader is assigned to a set of pursuers based on the instantaneous positions of all the players. In this regard, the corresponding multi-pursuer single-evader problem is analyzed first. Assuming that the evader knows the positions of all the pursuers and their pursuit strategy, the time-optimal evading strategies are derived for both constant bearing and pure pursuit cases for the pursuers using tools from optimal control theory. In the case of a constant bearing strategy, and assuming that the evader can follow any strategy, a dynamic task allocation algorithm is proposed for the pursuers. The algorithm is based on the well-known Apollonius circle and allows the pursuers to allocate their resources in an intelligent manner while guaranteeing the capture of the evader in minimum time. For the case of pure pursuit, the algorithm is modified using the counterpart of the Apollonius circle leading to an “Apollonius closed curve.” Finally, the proposed algorithms are extended to assign pursuers in the case of a problem with multiple pursuers and multiple evaders. Numerical simulations are included to demonstrate the performance of the proposed algorithms.

Evidences of Tenacibaculum maritimum evading strategies against Senegalese sole (Solea senegalensis) primary head-kidney leucocytes

Antimicrobial peptides (AMPs) are an essential component of innate immunity of invertebrates. Anti-lipopolysaccharide factor (ALF), as a main type of AMPs in crustaceans, attends in the disease prevention in general. In this research, a novel Group D ALF was identified and characterized from Penaeus monodon, named PenmonALF8. It was an anionic peptide, with both the full-length peptide and lipopolysaccharide binding domain (LBD) a low isoelectric point. PenmonALF8, composed of a signal peptide of 26 amino acids and a mature peptide of 98 amino acids, probably contained three alpha helixes and four beta sheets. Moreover, PenmonALF8 was detected in all tested tissues of P. monodon, and the expression level in hemocyte and intestine was relatively high. When challenged by Vibrio parahaemolyticus, PenmonALF8 showed 30–100 times higher expression level in all the tissues except in hemocyte and intestine, indicating that PenmonALF8 played a very important role in the immune response of P. monodon. By fusing to a SUMO protein, PenmonALF8 was successfully over-expressed in E. coli and purified by affinity chromatography. Additionally, the reconstituted PenmonALF8 and its LBD region displayed modest antimicrobial activity. This is the first research about the Group D ALF in P. monodon, which provides more information for humoral immunity study of shrimps.

Full-state autopilot-guidance design under a linear quadratic differential game formulation

Full-state single-loop and full-state two-loop autopilot-guidance architectures are derived under a linear quadratic differential game formulation. In the full-state single-loop case, the guidance command is injected directly to the actuator, whereas in the full-state two-loop case, it is the input to the autopilot loop. To prevent impractical end-game scenarios, where the states diverge to unacceptable values, a cost function that includes appropriate running cost terms on some of the states is proposed. The conditions for obtaining an equivalence relation between the full-state single-loop and full-state two-loop architectures are derived under a linear quadratic differential game formulation and the proposed cost function. Under such a formulation, the two full-state architectures are identical if and only if the number of guidance commands matches the number of available controllers. The guidance laws performance is illustrated using an interceptor missile having forward and aft controls in linear and nonlinear settings, while considering two types of evasion strategies. The first strategy is a linear controller based on the linear quadratic differential game solution. The second strategy is a “bang–bang” controller based on the optimal evasion solution. It is shown that the linear evasion strategy may not be suitable to represent a realistic evading strategy. In addition, the conditions for the existence of a saddle point solution are analyzed for the two full-state guidance laws.

Classifier ensemble reduction using a modified firefly algorithm: An empirical evaluation

In this research, we propose a variant of the firefly algorithm (FA) for classifier ensemble reduction. It incorporates both accelerated attractiveness and evading strategies to overcome the premature convergence problem of the original FA model. The attractiveness strategy takes not only the neighboring but also global best solutions into account, in order to guide the firefly swarm to reach the optimal regions with fast convergence while the evading action employs both neighboring and global worst solutions to drive the search out of gloomy regions. The proposed algorithm is subsequently used to conduct discriminant base classifier selection for generating optimized ensemble classifiers without compromising classification accuracy. Evaluated with standard, shifted, and composite test functions, as well as the Black-Box Optimization Benchmarking test suite and several high dimensional UCI data sets, the empirical results indicate that, based on statistical tests, the proposed FA model outperforms other state-of-the-art FA variants and classical metaheuristic search methods in solving diverse complex unimodal and multimodal optimization and ensemble reduction problems. Moreover, the resulting ensemble classifiers show superior performance in comparison with those of the original, full-sized ensemble models.

Cooperative Multiple Pursuers against a Single Evader

This paper considers a pursuit-evasion game for non-holonomic systems where a group of pursuers attempts to capture an evader in a bounded connected domain. The problem is challenging because all vehicles have the same maneuvering capability in terms of speed and turn radius constraint. The paper initially discusses a simple approach for holonomic systems that is based on the minimization of the safe-reachable area (the area containing the set of points to where an evader can travel without being caught). This idea is then extended to develop a pursuit-evasion strategy for non-holonomic systems. However, solving such a problem is computationally intractable. Therefore, we propose a computationally efficient algorithm to obtain approximate solutions. This paper also proposes an alternative approach to obtain a simple yet effective solution to the cooperative pursuit problem that is based on missile guidance laws. As there is no analytical proof of capture, we empirically evaluate the performance of the algorithms and perform a comparative study using solutions obtained from umpteen simulations. A total of four different cooperative pursuit strategies and three different evader strategies are taken into account for the comparative study. In the process, an evader strategy which is superior to that based on the optimization of safe-reachable area is also identified.

Hepatitis C virus hijacks host microRNAs to dampen antiviral interferon signaling

Abstract Hepatitis C virus (HCV) is a hepatotrophic ssRNA virus that infects over 160 million people worldwide and 60–80% of HCV cases will persist to a chronic infection, a serious risk factor for liver diseases. We recently discovered that HCV infection of hepatocytes induces expression of two microRNAs (miRNAs), miR-208b and miR-499a-5p. We found that these miRNA are capable of decreasing IFNL2 and IFNL3 expression to aid viral replication. Here we show that miR-208b and miR-499a-5p block type I IFN signaling in HCV-infected hepatocytes by directly targeting and down regulating the interferon (alpha, beta and omega) receptor 1 (IFNAR1) mRNA. Inhibition of these miRNAs during HCV infection of hepatoma cells rescued expression of IFNAR1 and improved the antiviral response to exogenous type I IFN. Interestingly, prolonged treatment of HCV-infected hepatocytes with type I IFNs led to a synergistic induction of miR-208b and miR-499a-5p, suggesting a critical role for type I IFN in the regulation of these miRNAs. As miR-208b and miR-499a-5p can target and suppress the IFNL3 risk allele, it is possible that increased miRNA expression following IFN treatment may partly explain why this genotype associates with poor response to IFN based therapies. Collectively these data define a new role for miR-208b and miR-499a-5p as HCV-induced suppressors of type I IFN signaling and add to our understanding of HCV immune evading strategies.

D-Alanylation of Teichoic Acids and Loss of Poly-N-Acetyl Glucosamine in Staphylococcus aureus during Exponential Growth Phase Enhance IL-12 Production in Murine Dendritic Cells.

Staphylococcus aureus is a major human pathogen that has evolved very efficient immune evading strategies leading to persistent colonization. During different stages of growth, S. aureus express various surface molecules, which may affect the immune stimulating properties, but very little is known about their role in immune stimulation and evasion. Depending on the growth phase, S. aureus may affect antigen presenting cells differently. Here, the impact of growth phases and the surface molecules lipoteichoic acid, peptidoglycan and poly-N-acetyl glucosamine on the induction of IL-12 imperative for an efficient clearance of S. aureus was studied in dendritic cells (DCs). Exponential phase (EP) S. aureus was superior to stationary phase (SP) bacteria in induction of IL-12, which required actin-mediated endocytosis and endosomal acidification. Moreover, addition of staphylococcal cell wall derived peptidoglycan to EP S. aureus stimulated cells increased bacterial uptake but abrogated IL-12 induction, while addition of lipoteichoic acid increased IL-12 production but had no effect on the bacterial uptake. Depletion of the capability to produce poly-N-acetyl glucosamine increased the IL-12 inducing activity of EP bacteria. Furthermore, the mutant dltA unable to produce D-alanylated teichoic acids failed to induce IL-12 but like peptidoglycan and the toll-like receptor (TLR) ligands LPS and Pam3CSK4 the mutant stimulated increased macropinocytosis. In conclusion, the IL-12 response by DCs against S. aureus is highly growth phase dependent, relies on cell wall D-alanylation, endocytosis and subsequent endosomal degradation, and is abrogated by receptor induced macropinocytosis.

Partial characterization of a novel anti-inflammatory protein from salivary gland extract of Hyalomma anatolicum anatolicum 77Acari: Ixodidae) ticks.

Aim:Hyalomma anatolicum anatolicum ticks transmit Theileria annulata, causative agent of tropical theileriosis to cattle and buffaloes causing a major economic loss in terms of production and mortality in tropical countries. Ticks have evolved several immune evading strategies to circumvent hosts’ rejection and achieve engorgement. Successful feeding of ticks relies on a pharmacy of chemicals located in their complex salivary glands and secreted saliva. These chemicals in saliva could inhibit host inflammatory responses through modulating cytokine secretion and detoxifying reactive oxygen species. Therefore, the present study was aimed to characterize anti-inflammatory peptides from salivary gland extract (SGE) of H. a. anatolicum ticks with a view that this information could be utilized in raising vaccines, designing synthetic peptides or peptidomimetics which can further be developed as novel therapeutics.Materials and Methods:Salivary glands were dissected out from partially fed adult female H. a. anatolicum ticks and homogenized under the ice to prepare SGE. Gel filtration chromatography was performed using Sephadex G-50 column to fractionate the crude extract. Protein was estimated in each fraction and analyzed for identification of anti-inflammatory activity. Sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE) was run for further characterization of protein in desired fractions.Results:A novel 28 kDa protein was identified in H. a. anatolicum SGE with pronounced anti-inflammatory activity.Conclusion:Purification and partial characterization of H. a. anatolicum SGE by size-exclusion chromatography and SDS-PAGE depicted a 28 kDa protein with prominent anti-inflammatory activity.