Impact of Titanium Skull Plate on Transcranial Magnetic Stimulation: Analysis of Induced Electric Fields.

BACKGROUND: Implanted titanium skull plates (TSPs) in cranioplasty are used to replace or reconstruct areas of the skull that have been damaged or removed due to trauma, surgery, or other medical conditions. However, the presence of a TSP in the head may influence the distribution of the electric field induced during transcranial magnetic stimulation (TMS) procedures. The purpose of this study was to determine how the presence of TSP would interfere with TMS-induced cortical electric fields. METHODS: The TMS with a figure-of-eight coil was applied to a realistic head model with TSPs. The distribution of the induced electric field in head tissues was calculated by employing the impedance method, and the results were compared with that of a normal head without TSP. RESULTS: Simulation results show that the distribution of the induced electric field has changed greatly for the head model with TSP. The maximum value of the induced electric field in head tissues was present under one of the circular coil wings rather than in the tissues beneath the junction of the two wings of the Fo8 coil. CONCLUSIONS: The induced electric field in deep brain regions was increased for the head model with TSP, which could potentially lead to deep brain stimulation. Since the presence of metallic TSP can greatly influence the distribution of the induced electric field in TMS applications, it is important to adjust the treatment scheme when considering TMS for individuals with cranial titanium plates.

Electromagnetic exposure analysis of the subway passenger under the civil communication system radiation.

In order to assess the electromagnetic exposure safety of passengers under the civil communication system of the subway, the radio-frequency (RF) electromagnetic environment of subway carriage is established by using COMSOL Multiphysics software, it includes a 1-1/4 " leaky coaxial cable (LCX1) and a 1-5/8" leaky coaxial cable (LCX2), which are designed to be the exposure sources, and twelve passengers at different position. The electromagnetic environment model has been verified through field measurement. The exposure dose distribution of twelve passengers is compared and analyzed, when LCX1 and LCX2 works respectively. The simulated results show that, to compare with LCX2, the electromagnetic dose absorbed by the passengers is reduced by 9.19% and 22.50% at 2100 MHz and 2600 MHz respectively. The specific absorption rate (SAR) of passengers obtains the maximum value of 1.91×10-4 W/Kg and the temperature rise to 0.214 K when the LCX1 works at 3400 MHz. By comparing with the public exposure limitation of the International Commission of Non-Ionizing Radiation Protection (ICNIRP), it demonstrates the electromagnetic exposure safety of the passengers under the civil communication system. More importantly, the proposed LCX1 not only could add the 5G signal cover but also lower the SAR absorbed by the passengers, which indicates that the public electromagnetic exposure dose could be reduced by adjusting the radiation performances of exposure source, which provide a new way for electromagnetic protecting.

Research on the influence of power frequency magnetic field of pantograph on pacemaker wearers' health in high-speed EMU.

When the popular means of transportation-high-speed trains meet the increasing rate of pacemaker implantation year by year, the research on the magnetic field environment on the health of pacemaker wearers in the carriage becomes an urgent problem. In this work, models of an electric multiple unit carriage with a pantograph as well as passengers with pacemakers were built by using COMSOL Multiphysics software. The B, Ein and Jin of human heart and other tissues, and the induced voltage (Vin) at the pacemaker electrode were calculated under the pantograph operating condition, so as to assess the effect of its magnetic field on the health of pacemaker wearers. The results showed that Bmax in the carriage without passengers is 121.246 µT, occurs near the window. In the carriage, the Bmax, Ein max and Jin max of heart and body, Vin at the pacemaker electrode of the passenger next to the window are greater than that in the middle of the carriage. The Bmax, Ein max and Jin max of passengers' heart are 11.301µT, 1.613 mV/m and 139.030 µA/m2, respectively. The Bmax, Ein max and Jin max of passengers' body are 12.597µT, 0.788 mV/m and 75.299 µA/m2, respectively. The maximum value of Vin at the tip of the pacemaker electrode of the passengers' is 0.048 mV. The Bmax, Ein max in all tissues of passengers are much smaller than the basic limits of electromagnetic exposure to the public set by the International Commission on Non-Ionizing Radiation. Vin at the electrode tip of passengers' pacemakers are less than the perception sensitivity set by the International Organization for Standardization. This work illustrated that the magnetic field generated by the pantograph is within the recognized accepted limits for passengers with pacemakers, but we still recommended that passengers wearing pacemakers should stay as far away from windows as possible.

Safety assessment of wireless chargers for electric vehicles considering thermal characteristics.

This study employs the transient finite element method and electromagnetic heat transfer theory to assess the heating generated by high-power wireless chargers during electric vehicle charging. The analysis includes simulating and analyzing the temperature distribution of two different types of shielding plates of the wireless charger and the specific absorption rate (SAR) and head temperature rise of both adults and children in close proximity to the charger. Simulation results show that the maximum temperature rise of the copper shielding plate is 16°C lower than that of the aluminum shielding plate after charging for 1 h. This temperature increase does not affect the chassis' s equipment. Regarding human safety, the induced electric field strength and SAR values in the child's head tissue are higher than those in the adult, meeting the International Commission on Non-Ionizing Radiation Protection (ICNIRP) limits. When the initial temperature is set to 37°C, the temperature rise in the heads of both adults and children is approximately equal after 1 h of charging, reaching a maximum temperature rise of 0.21 and 0.23°C, respectively. These values remain below the thermal limit of ICNIRP (2°C for Type 2 tissues). The findings indicate that the copper shielding plate can provide both electromagnetic shielding and heat dissipation functions, and the electromagnetic exposure absorbed by the human body and head temperature rise within safe ranges.

Comparing China REACH and the Jamaica Home Visiting Program.

OBJECTIVES: Delayed child skill development is a common phenomenon in low- and middle-income countries. Effective and low-cost strategies suitable for application to less-developed countries are needed. We summarize empirical findings from recent papers that study a replication of the Jamaica Reach Up and Learn home visiting program in China, China REACH, and compare child skill growth profiles in the China Reach Up and Jamaica interventions. METHODS: Different interventions often use different measures for assessing early childhood skill development. To estimate the growth of underlying skills across programs, we address the challenge that different programs use different assessments. We use a modified version of the Rasch model to anchor scores on common items to estimate skill development. RESULTS: Language skill growth curves are comparable for both interventions. This pattern is consistent for the treatment and control groups across the interventions. Skill growth curves are not statistically significantly different between China REACH and Jamaican interventions. We find evidence of the importance of early investment. CONCLUSIONS: The China REACH intervention significantly improves the development of multiple skills. At the same ages, treatment effect sizes and skill growth curves are comparable across the Jamaica and China REACH interventions, despite differences in scale and cultural settings. The scale of the program is much greater in China than in Jamaica, showing that the Jamaican curriculum can be effectively expanded to larger populations. Annual costs per child are roughly $500 (2015 US dollars).

EVALUATION OF ELECTROMAGNETIC FIELDS IN HUMAN BODY EXPOSED TO INVERTER OF PURE ELECTRIC VEHICLE.

On the basis of the basic principle of electromagnetic dosimetry, the paper studies the electromagnetic exposure of a passenger's body to a compound electromagnetic field caused by the combined action of DC and AC bus currents of a pure electric vehicle inverter. By building an electromagnetic model of a pure electric vehicle body, adult human body and inverter, the finite element method is used to calculate the magnetic induction intensity(|B|), induced electric field intensity(|E|) and induced current density(|J|) of the compound electromagnetic field to the human trunk and central nervous system in the driver and front seat passenger. The numerical results are compared with the exposure limits defined by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). The fields are well below the safe exposure limits defined by ICNIRP.

[Simulation study of force and temperature field during transcranial magnetic stimulation application working with magnetic resonance imaging simultaneously].

Currently, transcranial magnetic stimulation (TMS) has been widely used in the treatment of depression, Parkinson's disease and other neurological diseases. To be able to monitor the brain's internal activity during TMS in real time and achieve better treatment outcomes, the researchers proposed combining TMS with neuroimaging methods such as magnetic resonance imaging (MRI), both of which use Tesla-level magnetic fields. However, the combination of strong current, large magnetic field and small size is likely to bring physical concerns which can lead to mechanical and thermal instability. In this paper, the MRI static magnetic field, the TMS coil and human head model were built according to the actual situations. Through the coupling of the magnetic field and the heat transfer module in the finite element simulation software COMSOL, the force and temperature of the TMS coil and head were obtained when the TMS was used in combination with MRI (TMS-MRI technology). The results showed that in a 3 T MRI environment, the maximum force density on the coil could reach 2.51 × 109 N/m3. Both the direction of the external magnetic field and the current direction in the coil affected the force distributions. The closer to the boundary of the external magnetic field, the greater the force. The magnetic field generated by the coil during TMS treatment increased the temperature of the brain tissue by about 0.16 °C, and the presence of the MRI static magnetic field did not cause additional thermal effects. The results of this paper can provide a reference for the development of the use guidelines and safety guidelines of TMS-MRI technology.

Nile tilapia TRIM39 recruits I3K413 and I3KL45 as adaptors and is involved in the NF-κB pathway.

Tripartite motif (TRIM) proteins play a regulatory function in cancer, cell apoptosis and innate immunity. To understand the role of TRIM39 in Nile tilapia (Oreochromis niloticus), TRIM39 cDNA was isolated. The total length of TRIM39 cDNA was 5025 bp. The deduced OnTRIM39 protein contains 549 amino acids and has conserved domains of the TRIM family, which are the RING, B-box, coiled-coil and PRY-SPRY domains. OnTRIM39 mRNA was widely expressed in various tissues. After challenge with Streptococcus agalactiae and stimulation with polyinosinic polycytidylic acid [poly (I:C)] and lipopolysaccharides (LPS), the amount of OnTRIM39 transcript was changed in various tested tissues. OnTRIM39 overexpression increased NF-κB activity. OnTRIM39 was present in the cytoplasm. Mass spectrometry of proteins pulled down with recombinant OnTRIM39 showed that 250 proteins potentially interact with OnTRIM39. The authors selected I3K4I3 from the 250 candidate proteins to verify its interaction with TRIM39. They also selected I3KL45, a member of the same 14-3-3 protein family, to verify its interaction with TRIM39. The results of pull-down assays showed that OnTRIM39 interacted with both I3K413 and I3KL45. These results contribute to further study of the innate immune mechanism of tilapia.

Isolation, identification, and pathogenic characteristics of Nocardia seriolae in largemouth bass Micropterus salmoides.

The largemouth bass Micropterus salmoides is an important freshwater aquaculture fish in China. Recently, largemouth bass at a fish farm in Guangdong province experienced an outbreak of a serious ulcer disease. As part of the investigations conducted to identify the aetiology and identify potentially effective control measures, we isolated a pathogenic bacterium (NK-1 strain) from the diseased fish. It was identified as Nocardia seriolae through morphological observation, physiological and biochemical analysis, and molecular identification, and its pathogenicity was verified by experimental infection. Pathological changes in the diseased fish included granulomatous lesions in the liver and spleen, destruction of renal tubules, necrosis of intestinal epithelial cells, infiltration of inflammatory cells in the brain, vacuolation of cells, and swelling and cracking of the mitochondria and endoplasmic reticulum. Bacterial detection using qPCR showed that the spleen and intestine were the main organs targeted by N. seriolae. The mortality of largemouth bass experimentally infected with N. seriolae at 21°C was significantly lower than that in fish infected at higher temperatures between 24 and 33°C; there were no significant differences in the levels of mortality at these higher temperatures. The level of mortality of largemouth bass infected with N. seriolae was lowest at a neutral water pH of 7 but increased significantly at higher and lower pH. Of the tested Chinese herbal medicines, Chinese sumac Galla chinensis and Chinese skullcap Scutellaria baicalensis exhibited the best antibacterial effects. This study lays a foundation for the clinical diagnosis and scientific control of ulcer disease in largemouth bass.

TLR1 in Nile tilapia: The conserved receptor cannot interact with MyD88 and TIRAP but can activate NF-κB in vitro.

Toll-like receptors (TLRs) play a critical role in the innate immune response of fish. In this study, we isolated the cDNA sequence of Nile tilapia TLR1 (OnTLR1). The deduced OnTLR1 protein contains a signal peptide, 7 leucine-rich repeats (LRRs), a C-terminal LRR (LRR-CT), a transmembrane region and a highly conserved TIR domain. In healthy Nile tilapia, the OnTLR1 transcript was broadly expressed in all examined tissues, with the highest expression levels in the spleen. After infection with Streptococcus agalactiae, the OnTLR1 transcripts were upregulated in the gill and kidney. After stimulation with polyinosinic-polycytidylic acid (poly(I:C)), the expression levels of OnTLR1 were significantly downregulated in the intestine, whereas OnTLR1 transcripts were significantly upregulated in the kidney. After challenge with lipopolysaccharide (LPS), the expression levels of OnTLR1 were significantly upregulated in the spleen and kidney. The subcellular localization showed that OnTLR1 was expressed in the cytoplasm. TLR1 significantly increased MyD88-dependent NF-κB activity. However, the results of a pull-down assay showed that OnTLR1 did not interact with MyD88 or TIRAP. Binding assays revealed the specificity of OnTLR1 for pathogen-associated molecular patterns (PAMPs) and bacteria that included S. agalactiae, Aeromonas hydrophila and poly(I:C) and LPS. Taken together, these findings suggest that OnTLR1, as a pattern recognition receptor (PRR), might play an important role in the immune response to pathogen invasion.

[Study on the thermal field distribution of cholangiocarcinoma model by magnetic fluid hyperthermia].

Cholangiocarcinoma is a highly malignant tumor. It is not sensitive to radiotherapy and chemotherapy and has a poor prognosis. At present, there is no effective treatment. As a new method for treating cancer, magnetic fluid hyperthermia has been clinically applied to a variety of cancers in recent years. This article introduces it to the cholangiocarcinoma model and systematically studies the effect of magnetic fluid hyperthermia on cholangiocarcinoma. Starting from the theory of magnetic fluid heating, the electromagnetic and heat transfer models were constructed in the finite element simulation software COMSOL using the Pennes biological heat transfer equation. The Helmholtz coil was used as an alternating magnetic field generating device. The relationship between the magnetic fluid-related properties and the heating power was analyzed according to Rosensweig's theory. After the multiphysics coupling simulation was performed, the electromagnetic field and thermal field distribution in the hyperthermia region were obtained. The results showed that the magnetic field distribution in the treatment area was uniform, and the thermal field distribution met the requirements of hyperthermia. After the magnetic fluid injection, the cholangiocarcinoma tissue warmed up rapidly, and the temperature of tumor tissues could reach above 42 °C, but the surrounding healthy tissues did not heat up significantly. At the same time, it was verified that the large blood vessels around the bile duct, the overflow of the magnetic fluid, and the eddy current heat had little effect on thermotherapy. The results of this article can provide a reference for the clinical application of magnetic fluid hyperthermia for cholangiocarcinoma.

Structurally diverse genes encode TLR13 in Nile tilapia: The two receptors can recognize Streptococcus 23S RNA and conduct signal transduction through MyD88.

Toll-like receptors (TLRs) play a crucial role in the innate immune system, which is the first line of defence against pathogens and pathogenic products in fish. In the present study, we cloned the full-length cDNA and genome sequences of two TLR13 s (OnTLR13a, OnTLR13b) from Nile tilapia (Oreochromis niloticus). TLR family motifs, i.e., the leucine-rich repeat (LRR) domains and Toll/interleukin (IL)-1 receptor (TIR) domains, were conserved in the putative proteins OnTLR13a and OnTLR13b, with fifteen LRR domains and one TIR domain. Four exons and three introns were identified in the OnTLR13a genome sequence, and three exons and two introns were identified in the OnTLR13b genome sequence. In healthy Nile tilapia tissues, OnTLR13a and OnTLR13b were ubiquitously expressed in all 11 tested tissues/organs. The highest expression levels were observed in the spleen (OnTLR13a) and blood (OnTLR13b), and the lowest expression levels were observed in the liver (OnTLR13a) and stomach (OnTLR13b). The expression level of OnTLR13b at 5.5 days postfertilization (dpf) was significantly higher than that at the other 8 time points (2.5, 3.5, 4.5, 5, 6, 6.5, 7.5 and 8.5 dpf). Upon stimulation with an intraperitoneal injection of 200 µL (107 CFU/mL) Streptococcus agalactiae, the expression levels of OnTLR13a and OnTLR13b were significantly upregulated in the intestine and gill. After cotransfection with MyD88, OnTLR13a significantly increased MyD88-dependent NF-κB activation in 293 T cells. However, OnTLR13b significantly impaired MyD88-dependent NF-κB activation. In addition, TLR13a slightly increased MyD88-dependent AP-1 activation, and TLR13b significantly increased MyD88-dependent AP-1 activation. TLR13a significantly increased MyD88-dependent interferon-ß (IFN-ß) activation, and TLR13b had no effect on MyD88-dependent IFN-ß activation. These findings suggest that although the deduced protein structure of OnTLR13 is evolutionarily conserved between OnTLR13 and other TLR members, its signal transduction function is markedly different. Co-immunoprecipitation (Co-IP) assays showed that both OnTLR13a and OnTLR13b could interact with OnMyD88. RNA pulldown assays showed that TLR13a and TLR13b could combine with the 23S rRNA of S. agalactiae. These results indicate that TLR13a and TLR13b play important roles in the innate immune response against bacterial infection in Nile tilapia.

Safety Assessment of Electromagnetic Exposure in High-Speed Train Carriage with Full Passengers.

The objective of this work is to evaluate the safety of the electromagnetic environment in the carriage of high-speed trains exposed to power cables when the train is full of passengers. The electromagnetic model of a real carriage, two sets of power cables and the 84 passengers were set up by using COMSOL Multiphysics software based on CRH5. The distributions of induced electric and magnetic fields in the carriage, inside and on the surface of passengers were investigated. The results show that the induced electric and magnetic fields on the windows are greater than on the passengers and the max value of induced magnetic field is 2627.10 µT, and the max value of induced electric field is 2.0 × 105 mV m-1. The maximum values of the induced electric and magnetic fields in 84 passengers' brain tissues were obtained, and it was found that the maximum values occurred in the third row passengers. The distribution of induced electric and magnetic fields at the cross-section of passengers' heads in the third row was also obtained, and we found that the passengers at the window side were greater than those of aisle passengers. In the third row, the maximum values of the induced electric and magnetic fields in the head of two passengers near the window were 94.6 mV m-1, 90.9 µT, 96.3 mV m-1, and 90.4 µT, respectively. We also found the all data were below the ICNIRP Reference Levels, which indicates the electromagnetic exposure caused by power cables when the train is full of passengers will not threat passengers' health.

Group-level analysis of induced electric field in deep brain regions by different TMS coils.

Deep transcranial magnetic stimulation (dTMS) is a non-invasive technique used for the treatment of depression and obsessive compulsive disorder. In this study, we computationally evaluated group-level dosage for dTMS to characterize the targeted deep brain regions to overcome the limitations of using individualized head models to characterize coil performance in a population. We used an inter-subject registration method adapted to the deep brain regions that enable projection of computed electric fields (EFs) from individual realistic head models (n = 18) to the average space of deep brain regions. The computational results showed consistent group-level hotspots of the EF in the deep brain regions. The halo circular assembly coils induced the highest EFs in deep brain regions (up to 50% of the maximum EF in the cortex) for optimized positioning. In terms of the trade-off between field spread and penetration, the performance of the H7 coil was the best. The computational model allowed the optimization of generalized dTMS-induced EF on deep region targets despite inter-individual differences while informing and possibly minimizing unintended stimulation of superficial regions and possible mixed stimulation effects from deep and cortical areas. These results will facilitate the decision process during dTMS interventions in clinical practice.

Digital gene expression analysis in the liver of ScpB-vaccinated and Streptococcus agalactiae-challenged Nile tilapia.

In recent years, streptococcal diseases have severely threatened the development of tilapia aquaculture, but effective prevention and control methods have not yet been established. To understand the immune responses of vaccinated Nile tilapia (Oreochromis niloticus), digital gene expression (DGE) technology was applied in this study to detect the gene expression profile of the Nile tilapia (O. niloticus) liver in response to ScpB (Streptococcal C5a peptidase from group B Streptococcus, ScpB) vaccination and a Streptococcus agalactiae-challenge. The control and the ScpB-vaccinated Nile tilapia yielded a total of 25,788,734 and 27,088,598 clean reads, respectively. A total of 1234 significant differentially expressed unigenes were detected (P < 0.05), of which 236 were significantly up-regulated, and 269 were significantly down-regulated (P < 0.05, |fold|>2, FDR<0.05). Of the differentially expressed gene, the identified genes which were enriched using databases of GO and KEGG could be categorized into a total of 67 functional groups and were mapped to 153 signaling pathways including 15 immune-related pathways. The differentially expressed genes (TLR1, TLR2, TLR3, TLR5, TLR9, MyD88, C3, IL-1ß, IL-10) were detected in the expression profiles, and this was subsequently verified via quantitative real-time PCR (qPCR). The results of this study can serve as a basis for future research not only on the molecular mechanism of S. agalactiae invasion, but also on the anti-S. agalactiae mechanism in targeted tissues of Nile tilapia.

A safety study of 500 µA cathodal transcranial direct current stimulation in rat.

BACKGROUND: Transcranial direct current stimulation (tDCS) is a noninvasive neural control technology that has become a research hotspot. To facilitate further research of tDCS, the biosafety of 500 µA cathodal tDCS, a controversial parameter in rats was evaluated. RESULTS: 24 animals were randomly divided into two groups: a cathodal tDCS group (tDCS, n = 12) and control group (control, n = 12). Animals in the tDCS group received 5 consecutive days of cathodal tDCS (500 µA, 15 min, once per day) followed by a tDCS-free interval of 2 days and 5 additional days of stimulation, totally two treatments of tDCS for a total of 10 days. Computational 3D rat model was adopted to calculate the current density distributions in brain during tDCS treatment. Essential brain functions including motor function and learning and memory ability were evaluated. Additionally, to estimate the neurotoxicity of tDCS, the brain morphology, neurotransmitter levels and cerebral temperature were investigated. Our results showed that the current density inside the brain was less than 20 A/m2 during tDCS treatment in computational model. tDCS did not affect motor functions and learning and memory ability after tDCS treatment. In addition, no significant differences were found for the tDCS group in hematology, serum biochemical markers or the morphology of major organs. Moreover, tDCS treatment had no effect on the brain morphology, neural structures, neurotransmitter levels or cerebral temperature. CONCLUSION: 500 µA cathodal tDCS as performed in the present study was safe for rodents.

MHC Class IIB gene polymorphisms associated with resistance/susceptibility to Streptococcus agalactiae in Nile tilapia Oreochromis niloticus.

Genetic variation in the major histocompatibility complex (MHC) Class IIB was tested in Nile tilapia Oreochromis niloticus, and the association between the MHC IIB alleles and disease resistance was also studied. F3 fry offspring (n = 1200) from 12 full-sib families were challenged with Streptococcus agalactiae, which caused significantly different mortalities in different Nile tilapia families (11.00-81.10%). Twenty fry (F1) from each of the 12 families were selected to study the polymorphisms of the MHC Class IIB gene using PCR followed by cloning and sequencing methods. The results showed that the size of the amplified fragment was 770-797 bp. Thirty-seven sequences from 240 individuals revealed 22 different alleles, which belonged to 9 major allele types. Up to 63.58% of nucleotide positions were variable, while the proportion of the amino acid variable positions was up to 68.73%. According to the survival rate of offspring (F3) from 12 full-sib families, we deduced that the alleles Orni-DAB*0107, Orni-DAB*0201 and Orni-DAB*0302 were highly associated with resistance to S. agalactiae, while the allele Orni-DAB*0701 was associated with susceptibility to S. agalactiae. In addition, our previous study found that the allele Orni-DAB*0201 was more frequently distributed in the disease-resistant groups. Therefore, the allele Orni-DAB*0201 could be used as an S. agalactiae resistance-related MHC marker in molecular marker-assisted selective breeding programs for S. agalactiae-resistant Nile tilapia.

[Simulation of the relationship between magnetic medium parameters and heating temperature in magnetic fluid hyperthermia].

In this paper, we established magnetic fluid hyperthermia (MFH) model for rat tumor using the finite element software COMSOL based on the linear response theory. By analyzing four kinds of magnetic medium within relaxation mechanism, such as Fe 3O 4、FeCo、fccFePt and L1 0FePt, we studied the influence of the change of magnetic medium radius on dissipation power and temperature field, respectively. At the same time, the optimization method for the parameters of several magnetic medium is proposed, and the applications of four kinds of magnetic medium are given as well. By increasing the dissipation power of the magnetic medium as much as possible, the dose of magnetic medium used in the treatment can be reduced, meanwhile, the adverse effects on health tissue surrounding the tumor will be minimized. The conclusions of this paper can provide reference for magnetic medium preparation applied to MFH.

MHC class IIA polymorphisms and their association with resistance-susceptibility to Streptococcus agalactiae in Nile tilapia, Oreochromis niloticus.

The association between major histocompatibility complex (MHC) class IIA polymorphisms and the severity of infection by Streptococcus agalactiae was investigated using 40 susceptible and 40 resistant individuals of Nile tilapia Oreochromis niloticus. Twenty-five alleles were identified from 80 individuals, which belong to 22 major allele types. High polymorphism of mhcIIa gene and at least two loci were discovered in O. niloticus. In peptide-binding region (PBR) and non-PBR, the ratio of nonsynonymous substitution (dN) to synonymous substitution (dS) was 1.294 (>1) and 1.240 (>1), suggesting that the loci are evolving under positive balancing selection. Association analysis showed that the allele, orni-daa*0501, was significantly associated with resistance to S. agalactiae, while the alleles, orni-daa*1101, orni-daa*1301, orni-daa*1401 and orni-daa*1201, were associated with susceptibility to S. agalactiae. To confirm these correlations, another independent challenge experiment was performed in the Huizhou population of the O. niloticus. The frequency distribution showed that the orni-daa*1101 allele was significantly more frequent in the Huizhou-Susceptible group (HZ-SG) than in the Huizhou-Resistant group (HZ-RG) (P < 0.05), which was consistent with the first challenge. However, orni-daa*0501 did not present in HZ-SG and HZ-RG and the distribution frequencies of the orni-daa*1201, orni-daa*1301 and orni-daa*1401 alleles were not significantly more frequent in HZ-SG than in HZ-RG. These results indicate that the orni-daa*1101 allele confers susceptibility to S. agalactia infection. These results suggest that the diversity of exon 2 of mcaIIa alleles could be used to explore the association between disease susceptibility or resistance and the multiformity of mcaIIa and to achieve the molecular-assisted selection of O. niloticus with enhanced disease resistance.

Molecular characterization and function analysis of three RIG-I-like receptor signaling pathway genes (MDA5, LGP2 and MAVS) in Oreochromis niloticus.

The recognition of microbial pathogens, which is mediated by pattern recognition receptors (PRRs), is critical to the initiation of innate immune responses. In the present study, we isolated the full-length cDNA and genomic DNA sequences of the MDA5, LGP2 and MAVS genes in Nile tilapia, termed OnMDA5, OnLGP2 and OnMAVS. The OnMDA5 gene encodes 974 amino acids and contains two caspase-associated recruitment domains (CARDs), a DExDc domain (DExD/H box-containing domain), a HELICc (helicase superfamily C-terminal) domain and a C-terminal regulatory domain (RD). The OnLGP2 gene encodes 679 amino acids and contains a DExDc, a HELICc and an RD. The OnMAVS gene encodes 556 amino acids and contains a CARD, a proline-rich domain, a transmembrane helix domain and a putative TRAF2-binding motif (269PVQDT273). Phylogenetic analyses showed that all three genes from Nile tilapia were clustered together with their counterparts from other teleost fishes. Real-time PCR analyses showed that all three genes were constitutively expressed in all examined tissues in Nile tilapia. OnMDA5 presented the highest expression level in the blood and the lowest expression level in the liver, while OnMAVS presented the highest expression level in the kidney. The highest expression level of OnLGP2 was detected in the liver. An examination of the expression patterns of these RIG-I-like receptors (RLRs) during embryonic development showed that the highest expression levels of OnMDA5 occurred at 2 days postfertilization (dpf), and the expression significantly decreased from 3 to 8 dpf. The expression levels of OnLGP2 significantly increased from 4 to 8 dpf. The expression levels of OnMAVS mRNA were stable from 2 to 8 dpf. Upon stimulation by intraperitoneal injection of Streptococcus agalactiae, the expression levels of OnMDA5 were first downregulated and then upregulated in the blood, gill and spleen. In the intestine and kidney, the expression of OnMDA5 was first upregulated, then downregulated, and then upregulated again. The expression of OnLGP2 was upregulated in the kidney and intestine, and the expression of OnMAVS was upregulated in the spleen. Overexpression of OnMAVS increased NF-κB activation in 293 T cells (p < 0.05), and after cotransfection with OnMDA5, the OnMAVS-dependent NF-κB activation was slightly increased (p > 0.05), after cotransfection with OnLGP2, the OnMAVS-dependent NF-κB activation was significantly decreased (p < 0.05). These findings suggest that, although the deduced protein structure of OnMDA5 is evolutionarily conserved with the structures of other RLR members, its signal transduction function is markedly different. The results also suggest that OnLGP2 has a negative regulatory effect on the OnMAVS gene. OnMDA5 and OnMAVS were uniformly distributed throughout the cytoplasm in 293 T cells, whereas OnLGP2 was distributed throughout the cytoplasm and nucleus. These results are helpful for clarifying the innate immune response against bacterial infection in Nile tilapia.