Investigating the Effect of Flickering Frequency Pair and Mother Wavelet Selection in Steady-State Visually-Evoked Potentials on Two-Command Brain-Computer Interfaces

IntroductionSteady-state visually evoked potentials (SSVEPs) have become popular in brain-computer interface (BCI) applications in addition to many other applications on clinical neuroscience (neurodegenerative disorders, schizophrenia, epilepsy, etc.), cognitive (visual attention, working memory, brain rhythms, etc.), and use of engineering researches. Among available methods to measure brain activities, SSVEPs have advantages like higher information transfer rate, simplicity in structure, and short training time. SSVEP-based BCIs use flickering stimuli at different frequencies to discriminate distinct commands in real life. Some features are extracted from the SSVEP signals before these commands are classified. The wavelet transform (WT) has attracted researchers among feature extraction methods since it utilizes the non-stationary signals well. In the WT, a sample function (named mother wavelet) represents the SSVEP signal in both time and frequency domains. Unfortunately, there is no universal mother wavelet function that fits all the signals. Therefore, choosing an appropriate mother wavelet function may be a challenge in WT-related studies. Although there are such studies in three- and seven-command SSVEP-based studies, there is no study for two-command systems in our knowledge.Materials and MethodsIn this study, two user commands flickered at the combinations of seven different frequencies were tested to determine which frequency pairs give the highest performance. For this purpose, three well-known wavelet features (energy, entropy, and variance) were calculated for each of derived EEG frequency bands from the discrete WT coefficients of SSVEP signals. The WT was repeated for six different mother wavelet functions (Haar, Db4, Sym4, Coif1, Bior3.5, and Rbior2.8). Then, four feature sets (every three features, and all together) were applied to seven commonly-used machine learning algorithms (Decision Tree, Discriminant Analysis, Logistic Regression, Naive Bayes, Support Vector Machines, Nearest Neighbors, and Ensemble Classifiers).Results and DiscussionWe achieved 100% accuracies among these 3,528 runs (7 classifiers x 4 feature sets x 6 mother wavelets x 21 flickering frequency pairs) using the mother wavelet function of Haar and the Ensemble Learner classifier. The highest classifier performances are 100% when two commands have the flickering frequency pairs of (6.0 and 10 Hz), (6.5 and 8.2 Hz), or (6.5 and 10.0 Hz).ConclusionWe obtained three main outcomes from this study. First, the most representative mother wavelet function was Haar, while the worst one was Symlet 4. Second, the Ensemble Learner classifier gave the maximum classifier performance in a two-command SSVEP-based BCI system. Besides, two user commands from SSVEP should be one of the frequency pairs of (6.0 and 10.0 Hz), (6.5 and 8.2 Hz), and (6.5 and 10.0 Hz) to achieve the maximum accuracy.     

Multi-Variate EEG Analysis as a Novel Tool to Examine Brain Responses to Naturalistic Music Stimuli

Note onsets in music are acoustic landmarks providing auditory cues that underlie the perception of more complex phenomena such as beat, rhythm, and meter. For naturalistic ongoing sounds a detailed view on the neural representation of onset structure is hard to obtain, since, typically, stimulus-related EEG signatures are derived by averaging a high number of identical stimulus presentations. Here, we propose a novel multivariate regression-based method extracting onset-related brain responses from the ongoing EEG. We analyse EEG recordings of nine subjects who passively listened to stimuli from various sound categories encompassing simple tone sequences, full-length romantic piano pieces and natural (non-music) soundscapes. The regression approach reduces the 61-channel EEG to one time course optimally reflecting note onsets. The neural signatures derived by this procedure indeed resemble canonical onset-related ERPs, such as the N1-P2 complex. This EEG projection was then utilized to determine the Cortico-Acoustic Correlation (CACor), a measure of synchronization between EEG signal and stimulus. We demonstrate that a significant CACor (i) can be detected in an individual listener''s EEG of a single presentation of a full-length complex naturalistic music stimulus, and (ii) it co-varies with the stimuli’s average magnitudes of sharpness, spectral centroid, and rhythmic complexity. In particular, the subset of stimuli eliciting a strong CACor also produces strongly coordinated tension ratings obtained from an independent listener group in a separate behavioral experiment. Thus musical features that lead to a marked physiological reflection of tone onsets also contribute to perceived tension in music.     

Neural Responses to Smoking Stimuli Are Influenced by Smokers' Attitudes towards Their Own Smoking Behaviour

An important feature of addiction is the high drug craving that may promote the continuation of consumption. Environmental stimuli classically conditioned to drug-intake have a strong motivational power for addicts and can elicit craving. However, addicts differ in the attitudes towards their own consumption behavior: some are content with drug taking (consonant users) whereas others are discontent (dissonant users). Such differences may be important for clinical practice because the experience of dissonance might enhance the likelihood to consider treatment. This fMRI study investigated in smokers whether these different attitudes influence subjective and neural responses to smoking stimuli. Based on self-characterization, smokers were divided into consonant and dissonant smokers. These two groups were presented smoking stimuli and neutral stimuli. Former studies have suggested differences in the impact of smoking stimuli depending on the temporal stage of the smoking ritual they are associated with. Therefore, we used stimuli associated with the beginning (BEGIN-smoking-stimuli) and stimuli associated with the terminal stage (END-smoking-stimuli) of the smoking ritual as distinct stimulus categories. Stimulus ratings did not differ between both groups. Brain data showed that BEGIN-smoking-stimuli led to enhanced mesolimbic responses (amygdala, hippocampus, insula) in dissonant compared to consonant smokers. In response to END-smoking-stimuli, dissonant smokers showed reduced mesocortical responses (orbitofrontal cortex, subcallosal cortex) compared to consonant smokers. These results suggest that smoking stimuli with a high incentive value (BEGIN-smoking-stimuli) are more appetitive for dissonant than consonant smokers at least on the neural level. To the contrary, smoking stimuli with low incentive value (END-smoking-stimuli) seem to be less appetitive for dissonant smokers than consonant smokers. These differences might be one reason why dissonant smokers experience difficulties in translating their attitudes into an actual behavior change.     

Responses of Neurons of the Extrastriate Area 21b of the Cat Brain Cortex to Changes in Orientation of Moving Visual Stimuli

We studied the responses of neurons of the extrastriate cortical area 21b of the cat to changes in orientation of the movements of visual stimuli within the receptive field (RF) of the neuron under study. Our experiments demonstrated that 24 of 108 cells (22%) responded differentially to a certain extent to orientation of the movements of visual stimuli. As a whole, neurons of the area 21b did not demonstrate fine tuning on the optimum angle of orientation. In many cases, neuronal responses to different orientations of the movement of visual stimulus depended significantly on specific parameters of this stimulus (its shape, dimensions, and contrast). Some directionally sensitive neurons responded to a change in orientation of the movement of visual stimuli by modification of the index of directionality. We also studied spatial organization of the RF of neurons with the presentation of stationary visual stimuli. Comparison of the neuronal responses to a change in orientation of the movements of stimuli and to presentation of stationary stimuli showed that the correlation between the orientation sensitivity of the neuron under study and the stationary functional organization of its RF was insignificant. We hypothesize that inhibitory processes and subthreshold influences from a space surrounding the RF play a special role in the formation of the neuronal responses generated in the associative visual cortical regions to visual stimulation.     

Neural Responses in Parietal and Occipital Areas in Response to Visual Events Are Modulated by Prior Multisensory Stimuli

The effect of multi-modal vs uni-modal prior stimuli on the subsequent processing of a simple flash stimulus was studied in the context of the audio-visual ‘flash-beep’ illusion, in which the number of flashes a person sees is influenced by accompanying beep stimuli. EEG recordings were made while combinations of simple visual and audio-visual stimuli were presented. The experiments found that the electric field strength related to a flash stimulus was stronger when it was preceded by a multi-modal flash/beep stimulus, compared to when it was preceded by another uni-modal flash stimulus. This difference was found to be significant in two distinct timeframes – an early timeframe, from 130–160 ms, and a late timeframe, from 300–320 ms. Source localisation analysis found that the increased activity in the early interval was localised to an area centred on the inferior and superior parietal lobes, whereas the later increase was associated with stronger activity in an area centred on primary and secondary visual cortex, in the occipital lobe. The results suggest that processing of a visual stimulus can be affected by the presence of an immediately prior multisensory event. Relatively long-lasting interactions generated by the initial auditory and visual stimuli altered the processing of a subsequent visual stimulus.     

Wavelet-synchrony of Brain Evoked Responses during Listening to Naturalistic Stimuli in the Prognosis of Consciousness Recovery (Study 1: Wavelet-synchrony during Listening to Instrumental Music)

The features and prognostic value of wavelet-synchrony of evoked responses during the listening to realistic stimuli (music) were revealed in the study. Musical passages were selected according the patients’ preferences by their relations consultation. Wavelet-connections were calculated for each melody in the range from 0 to 1000 ms from stimuli. Total 22 examinees in 12 patients being in unconsciousness state were carried out. Resting state values of wavelet-connectivity were poorer in vegetative patients in comparison to healthy subjects regardless of consciousness recovery degree in future while wavelet-connections in mutism were higher in comparison to healthy subjects. Absolute value of wavelet-synchrony was lower than in norm. In patients with compete consciousness recovery in the future the maximal values of wavelet-synchrony were revealed in the temporal-occipital area while in patients who in the future have been revealed in the lesser degree the maximal values of wavelet-synchrony are shown in frontal-central areas. In chronic unconsciousness patients during the listening to instrumental music the maximal wavelet-connections values were determined in the right frontal area.     

Myeloablative Temozolomide Enhances CD8+ T-Cell Responses to Vaccine and Is Required for Efficacy against Brain Tumors in Mice

Temozolomide (TMZ) is an alkylating agent shown to prolong survival in patients with high grade glioma and is routinely used to treat melanoma brain metastases. A prominent side effect of TMZ is induction of profound lymphopenia, which some suggest may be incompatible with immunotherapy. Conversely, it has been proposed that recovery from chemotherapy-induced lymphopenia may actually be exploited to potentiate T-cell responses. Here, we report the first demonstration of TMZ as an immune host-conditioning regimen in an experimental model of brain tumor and examine its impact on antitumor efficacy of a well-characterized peptide vaccine. Our results show that high-dose, myeloablative (MA) TMZ resulted in markedly reduced CD4⁺, CD8⁺ T-cell and CD4⁺Foxp3⁺ T_Reg counts. Adoptive transfer of naïve CD8⁺ T cells and vaccination in this setting led to an approximately 70-fold expansion of antigen-specific CD8⁺ T cells over controls. Ex vivo analysis of effector functions revealed significantly enhanced levels of pro-inflammatory cytokine secretion from mice receiving MA TMZ when compared to those treated with a lower lymphodepletive, non-myeloablative (NMA) dose. Importantly, MA TMZ, but not NMA TMZ was uniquely associated with an elevation of endogenous IL-2 serum levels, which we also show was required for optimal T-cell expansion. Accordingly, in a murine model of established intracerebral tumor, vaccination-induced immunity in the setting of MA TMZ–but not lymphodepletive, NMA TMZ–led to significantly prolonged survival. Overall, these results may be used to leverage the side-effects of a clinically-approved chemotherapy and should be considered in future study design of immune-based treatments for brain tumors.     

Coordinated Ontogeny of Food Preference and Responses to Chemical Food Stimuli by a Lizard Ctenosaura pectinata (Reptilia: Iguanidae)

When important ecological factors change predictably during the life of an organism, the ontogeny of related behaviors must be timed to maintain appropriate behavioral responsiveness to current ecological conditions. In the brown iguana, Ctenosaura pectinata , hatchlings in natural populations eat primarily insects, consuming little plant matter, whereas adults eat primarily plants, consuming some insects as well. We conducted laboratory experiments on diet preferences and responses to chemical cues that the lizards sampled by tongue-flicking and used to identify food. All hatchlings ate crickets, but only one of six ate romaine lettuce. They responded strongly to chemical cues from prey, as indicated by elevated tongue-flick rates, but not from romaine lettuce. All older individuals ate both crickets and romaine lettuce. They responded much more strongly to chemical cues from both crickets and romaine lettuce than to control chemicals, as indicated by higher proportions of individuals that bit and higher tongue-flick attack scores.
Thus, an ontogenetic change to increased responsiveness to plant chemical stimuli was coordinated with an ontogenetic change to an herbivorous diet. The mechanisms underlying these ontogenetic changes are unknown, but folivory may be unprofitable before juveniles acquire intestinal flora that degrade cellulose by ingestion of feces of adult conspecifics. Possible mechanisms are discussed, including the detection of chemical cues from appropriate food plants during consumption of feces from older individuals. Studies of other squamate reptiles suggest that exposure to these chemicals might affect both future responsiveness to the chemical cues and a tendency to eat the corresponding plants.     

Metabolic Stress Responses in Drosophila Are Modulated by Brain Neurosecretory Cells That Produce Multiple Neuropeptides

In Drosophila, neurosecretory cells that release peptide hormones play a prominent role in the regulation of development, growth, metabolism, and reproduction. Several types of peptidergic neurosecretory cells have been identified in the brain of Drosophila with release sites in the corpora cardiaca and anterior aorta. We show here that in adult flies the products of three neuropeptide precursors are colocalized in five pairs of large protocerebral neurosecretory cells in two clusters (designated ipc-1 and ipc-2a): Drosophila tachykinin (DTK), short neuropeptide F (sNPF) and ion transport peptide (ITP). These peptides were detected by immunocytochemistry in combination with GFP expression driven by the enhancer trap Gal4 lines c929 and Kurs-6, both of which are expressed in ipc-1 and 2a cells. This mix of colocalized peptides with seemingly unrelated functions is intriguing and prompted us to initiate analysis of the function of the ten neurosecretory cells. We investigated the role of peptide signaling from large ipc-1 and 2a cells in stress responses by monitoring the effect of starvation and desiccation in flies with levels of DTK or sNPF diminished by RNA interference. Using the Gal4-UAS system we targeted the peptide knockdown specifically to ipc-1 and 2a cells with the c929 and Kurs-6 drivers. Flies with reduced DTK or sNPF levels in these cells displayed decreased survival time at desiccation and starvation, as well as increased water loss at desiccation. Our data suggest that homeostasis during metabolic stress requires intact peptide signaling by ipc-1 and 2a neurosecretory cells.     

Characterization of Anamnestic T-cell Responses Induced by Conventional Vaccines against Contagious Bovine Pleuropneumonia

A better understanding of how T1 vaccination confers immunity would facilitate the rational design of improved vaccines against contagious bovine pleuropneumonia (CBPP). We show here that mycoplasmas-induced recall proliferation and IFN-γ responses are detected in cattle that received multiple shots of T1 vaccines. These anamnestic responses were under the strict control of CD4⁺ T lymphocytes. Moreover, CD62L expression indicated that both CD4⁺ effector memory (Tem) and central memory (Tcm) T lymphocytes are elicited in these animals. Comparative analysis with data from cattle that completely recovered from CBPP infection revealed similar anamnestic T-cell responses albeit at a lower magnitude for T1-vaccinated animals, particularly in the Tcm compartment. In conclusion, we discuss how our current understanding of T-cell responses will contribute to ongoing efforts for the improvement of future CBPP vaccines.     

Defense Responses in Rice Induced by Silicon Amendment against Infestation by the Leaf Folder Cnaphalocrocis medinalis

Silicon (Si) amendment to plants can confer enhanced resistance to herbivores. In the present study, the physiological and cytological mechanisms underlying the enhanced resistance of plants with Si addition were investigated for one of the most destructive rice pests in Asian countries, the rice leaf folder, Cnaphalocrocis medinalis (Guenée). Activities of defense-related enzymes, superoxide dismutase, peroxidase, catalase, phenylalanine ammonia-lyase, and polyphenol oxidase, and concentrations of malondialdehyde and soluble protein in leaves were measured in rice plants with or without leaf folder infestation and with or without Si amendment at 0.32 g Si/kg soil. Silicon amendment significantly reduced leaf folder larval survival. Silicon addition alone did not change activities of defense-related enzymes and malondialdehyde concentration in rice leaves. With leaf folder infestation, activities of the defense-related enzymes increased and malondialdehyde concentration decreased in plants amended with Si. Soluble protein content increased with Si addition when the plants were not infested, but was reduced more in the infested plants with Si amendment than in those without Si addition. Regardless of leaf folder infestation, Si amendment significantly increased leaf Si content through increases in the number and width of silica cells. Our results show that Si addition enhances rice resistance to the leaf folder through priming the feeding stress defense system, reduction in soluble protein content and cell silicification of rice leaves.     

Overexpression of Extracellular Superoxide Dismutase Protects against Brain Injury Induced by Chronic Hypoxia

Extracellular superoxide dismutase (EC-SOD) is an isoform of SOD normally found both intra- and extra-cellularly and accounting for most SOD activity in blood vessels. Here we explored the role of EC-SOD in protecting against brain damage induced by chronic hypoxia. EC-SOD Transgenic mice, were exposed to hypoxia (FiO2.1%) for 10 days (H-KI) and compared to transgenic animals housed in room air (RA-KI), wild type animals exposed to hypoxia (H-WT or wild type mice housed in room air (RA-WT). Overall brain metabolism evaluated by positron emission tomography (PET) showed that H-WT mice had significantly higher uptake of ¹⁸FDG in the brain particularly the hippocampus, hypothalamus, and cerebellum. H-KI mice had comparable uptake to the RA-KI and RA-WT groups. To investigate the functional state of the hippocampus, electrophysiological techniques in ex vivo hippocampal slices were performed and showed that H-KI had normal synaptic plasticity, whereas H-WT were severely affected. Markers of oxidative stress, GFAP, IBA1, MIF, and pAMPK showed similar values in the H-KI and RA-WT groups, but were significantly increased in the H-WT group. Caspase-3 assay and histopathological studies showed significant apoptosis/cell damage in the H-WT group, but no significant difference in the H-KI group compared to the RA groups. The data suggest that EC-SOD has potential prophylactic and therapeutic roles in diseases with compromised brain oxygenation.     

Molecular Hydrogen in Drinking Water Protects against Neurodegenerative Changes Induced by Traumatic Brain Injury

Traumatic brain injury (TBI) in its various forms has emerged as a major problem for modern society. Acute TBI can transform into a chronic condition and be a risk factor for neurodegenerative diseases such as Alzheimer’s and Parkinson’s diseases, probably through induction of oxidative stress and neuroinflammation. Here, we examined the ability of the antioxidant molecular hydrogen given in drinking water (molecular hydrogen water; mHW) to alter the acute changes induced by controlled cortical impact (CCI), a commonly used experimental model of TBI. We found that mHW reversed CCI-induced edema by about half, completely blocked pathological tau expression, accentuated an early increase seen in several cytokines but attenuated that increase by day 7, reversed changes seen in the protein levels of aquaporin-4, HIF-1, MMP-2, and MMP-9, but not for amyloid beta peptide 1–40 or 1–42. Treatment with mHW also reversed the increase seen 4 h after CCI in gene expression related to oxidation/carbohydrate metabolism, cytokine release, leukocyte or cell migration, cytokine transport, ATP and nucleotide binding. Finally, we found that mHW preserved or increased ATP levels and propose a new mechanism for mHW, that of ATP production through the Jagendorf reaction. These results show that molecular hydrogen given in drinking water reverses many of the sequelae of CCI and suggests that it could be an easily administered, highly effective treatment for TBI.     

Reduction of the Inflammatory Responses against Alginate-Poly-L-Lysine Microcapsules by Anti-Biofouling Surfaces of PEG-b-PLL Diblock Copolymers

Large-scale application of alginate-poly-L-lysine (alginate-PLL) capsules used for microencapsulation of living cells is hampered by varying degrees of success, caused by tissue responses against the capsules in the host. A major cause is proinflammatory PLL which is applied at the surface to provide semipermeable properties and immunoprotection. In this study, we investigated whether application of poly(ethylene glycol)-block-poly(L-lysine hydrochloride) diblock copolymers (PEG-b-PLL) can reduce the responses against PLL on alginate-matrices. The application of PEG-b-PLL was studied in two manners: (i) as a substitute for PLL or (ii) as an anti-biofouling layer on top of a proinflammatory, but immunoprotective, semipermeable alginate-PLL₁₀₀ membrane. Transmission FTIR was applied to monitor the binding of PEG-b-PLL. When applied as a substitute for PLL, strong host responses in mice were observed. These responses were caused by insufficient binding of the PLL block of the diblock copolymers confirmed by FTIR. When PEG-b-PLL was applied as an anti-biofouling layer on top of PLL₁₀₀ the responses in mice were severely reduced. Building an effective anti-biofouling layer required 50 hours as confirmed by FTIR, immunocytochemistry and XPS. Our study provides new insight in the binding requirements of polyamino acids necessary to provide an immunoprotective membrane. Furthermore, we present a relatively simple method to mask proinflammatory components on the surface of microcapsules to reduce host responses. Finally, but most importantly, our study illustrates the importance of combining physicochemical and biological methods to understand the complex interactions at the capsules'' surface that determine the success or failure of microcapsules applicable for cell-encapsulation.     

Appetitive Responses to Computer-Generated Visual Stimuli by Female Rhombodera basalis, Deroplatys lobata, Hierodula membranacea, and Miomantis sp. (Insecta: Mantodea)

We used computer-generated stimuli to assess the stimulus parameters eliciting prey-directed behaviors in four mantis species: Rhombodera basalis (60 mm body length), Deroplatys lobata (70 mm), Hierodula membranacea (80 mm), Miomantis sp (38 mm). All responded appetitively to erratically moving disks subtending 10° or more. R. basalis responded more consistently to checkered (versus solid black) disks; only D. lobata displayed a size preference (14–23 deg disks); Miomantis sp. struck at disks as large as did the largest species; only Miomantis sp. displayed approaching behavior. H. membranacea and R. basalis preferred black disks on a white background (versus the reverse), and red disks (versus blue or green) on a brightness-matched grey background. All preferred elongated stimuli moving parallel (versus perpendicular) to their long axes.     

Activation of Cyclic AMP-Generating Systems in Brain Membranes and Slices by the Diterpene Forskolin: Augmentation of Receptor-Mediated Responses

The diterpene forskolin markedly activates adenylate cyclase in membranes from various rat brain regions and elicits marked accumulations of radioactive cyclic AMP in adenine-labeled slices from cerebral cortex, cerebellum, hippocampus, striatum, superior colliculi, hypothalamus, thalamus, and medulla-pons. In cerebral cortical slices, forskolin has half-maximal effects at 20-30 microM on cyclic AMP levels, both alone and in the presence of the phosphodiesterase inhibitor ZK 62771. The presence of a very low dose of forskolin (1 microM) can augment the response of brain cyclic AMP-generating systems to norepinephrine, isoproterenol, histamine, serotonin, dopamine, adenosine, prostaglandin E2, and vasoactive intestinal peptide. Forskolin does not augment responses to combinations of histamine-norepinephrine adenosine-norepinephrine, or histamine-adenosine. For norepinephrine and isoproterenol in rat cerebral cortical slices and for histamine in guinea pig cerebral cortical slices, the presence of 1 microM-forskolin augments the apparent efficacy of the amine, whereas for adenosine, prostaglandin E2, and vasoactive intestinal peptide, the major effect of 1 microM-forskolin is to increase the apparent potency of the stimulatory agent. In rat striatal slices, forskolin reveals a significant response of cyclic AMP systems to dopamine and augments the dopamine-elicited activation of adenylate cyclase in rat striatal membranes. The activation of cyclic AMP systems by forskolin is rapid and reversible, and appears to involve both direct activation of adenylate cyclase and facilitation and/or enhancement of receptor-mediated activation of the enzyme.     

Investigating the therapeutic potential of herbal leads against drug resistant Listeria monocytogenes by computational virtual screening and in vitro assays

Listeria monocytogenes, a Gram-positive opportunistic food-borne pathogen, naturally resistant to many antibiotics and acquired resistance may be a concern in the nearer future. Hence, there is a scope for screening of novel therapeutic agents and drug targets, toward the treatment of fatal listeria infections. The SecA homologs, SecA1 and SecA2 are the essential components of the general secretion (Sec) pathway, a specialised protein export system, present in L. monocytogenes. This study evaluates the use of botanicals against L. monocytogenes MTCC 1143 by considering SecA proteins as probable drug targets by high-throughput screening approaches. The 3D structure of SecA proteins with good stereochemical validity was generated by comparative modelling. The druglikeness and pharmacokinetic properties of 97 phytoligands identified through the extensive literature survey were predicted for druglikeness and ADMET properties. The inhibitory properties of best candidates were studied by molecular docking. The effect of the selected candidate molecules were further analysed in vitro well diffusion and cell aggregation assays. The antibiotic sensitivity profiling applied to L. monocytogenes MTCC 1143 using clinically relevant antibiotics showed that the bacteria became drug resistant to many tested antibiotics. The virtual screening suggested that .05 M cinnamic aldehyde from Cinnamomum camphora and 1, 2-Epoxycyclododecane from Cassia auriculata were identified as potential SecA inhibitors. The well diffusion assays suggested that the selected herbal substances have antibacterial activities. Further, preliminary validation suggested that incorporation of cinnamic aldehyde and methanolic or ethyl acetate extract of C. auriculata in broth medium shows growth reduction, misassembly and cell aggregation. This indicates the inhibition of SecA targets.     

A Role for Immune Responses against Non-CS Components in the Cross-Species Protection Induced by Immunization with Irradiated Malaria Sporozoites

Immunization with irradiated Plasmodium sporozoites induces sterile immunity in rodents, monkeys and humans. The major surface component of the sporozoite the circumsporozoite protein (CS) long considered as the antigen predominantly responsible for this immunity, thus remains the leading candidate antigen for vaccines targeting the parasite''s pre-erythrocytic (PE) stages. However, this role for CS was questioned when we recently showed that immunization with irradiated sporozoites (IrrSpz) of a P. berghei line whose endogenous CS was replaced by that of P. falciparum still conferred sterile protection against challenge with wild type P. berghei sporozoites. In order to investigate the involvement of CS in the cross-species protection recently observed between the two rodent parasites P. berghei and P. yoelii, we adopted our gene replacement approach for the P. yoelii CS and exploited the ability to conduct reciprocal challenges. Overall, we found that immunization led to sterile immunity irrespective of the origin of the CS in the immunizing or challenge sporozoites. However, for some combinations, immune responses to CS contributed to the acquisition of protective immunity and were dependent on the immunizing IrrSpz dose. Nonetheless, when data from all the cross-species immunization/challenges were considered, the immune responses directed against non-CS parasite antigens shared by the two parasite species played a major role in the sterile protection induced by immunization with IrrSpz. This opens the perspective to develop a single vaccine formulation that could protect against multiple parasite species.     

Broadly Neutralizing Immune Responses against Hepatitis C Virus Induced by Vectored Measles Viruses and a Recombinant Envelope Protein Booster

Hepatitis C virus (HCV) infection remains a serious public health problem worldwide. Treatments are limited, and no preventive vaccine is available. Toward developing an HCV vaccine, we engineered two recombinant measles viruses (MVs) expressing structural proteins from the prototypic HCV subtype 1a strain H77. One virus directs the synthesis of the HCV capsid (C) protein and envelope glycoproteins (E1 and E2), which fold properly and form a heterodimer. The other virus expresses the E1 and E2 glycoproteins separately, with each one fused to the cytoplasmic tail of the MV fusion protein. Although these hybrid glycoproteins were transported to the plasma membrane, they were not incorporated into MV particles. Immunization of MV-susceptible, genetically modified mice with either vector induced neutralizing antibodies to MV and HCV. A boost with soluble E2 protein enhanced titers of neutralizing antibody against the homologous HCV envelope. In animals primed with MV expressing properly folded HCV C-E1-E2, boosting also induced cross-neutralizating antibodies against two heterologous HCV strains. These results show that recombinant MVs retain the ability to induce MV-specific humoral immunity while also eliciting HCV neutralizing antibodies, and that anti-HCV immunity can be boosted with a single dose of purified E2 protein. The use of MV vectors could have advantages for pediatric HCV vaccination.     

Enhancement of Defence Responses against Bayoud Disease by Treatment of Date Palm Seedlings with an Hypoaggressive Fusarium oxysporum Isolate

Pretreatment of date palm seedlings with an hypoaggressive Fusarium isolate (AHD) protected them partially from further infection by Fusarium oxysporum f.sp. albedinis (Foa), the Bayoud disease pathogen. No mortality occurred during 2–3 months of incubation in plants pretreated with AHD, as opposed to aggressive isolate (ZAG) inoculated controls where up to 100% mortality was observed 15–30 days after inoculation. Such protection involved biochemical interactions between the host plant and AHD since no direct competition or antagonism was revealed between AHD and ZAG. The examination of the accumulation of phenolics and peroxidase activity, two parameters previously reported to be involved in date palm resistance to Foa, indicated that the response to AHD was correlated with the ability of pretreated date palm tissues to establish a faster defence response in the roots of both susceptible and resistant cultivars. Plants pretreated with AHD accumulated higher amounts of phenolics, mainly non‐constitutive hydroxycinnamic acid derivatives, which play a crucial role in date palm defence against Foa, as previously described by our group. These compounds were accumulated along with the constitutive caffeoylshikimic acids. A faster induction of peroxidase activity in response to Foa was also recorded in plants pretreated with AHD. Given the multi‐component nature of these induced responses, AHD could be part of integrated disease management strategies for a sustainable control of the palm tree Bayoud disease.