Characterization of immunoglobulin loci in the gigantic genome of Ambystoma mexicanum

BackgroundThe axolotl, Ambystoma mexicanum is a unique biological model for complete tissue regeneration. Is a neotenic endangered species and is highly susceptible to environmental stress, including infectious disease. In contrast to other amphibians, the axolotl is particularly vulnerable to certain viral infections. Like other salamanders, the axolotl genome is one of the largest (32 Gb) and the impact of genome size on Ig loci architecture is unknown. To better understand the immune response in axolotl, we aimed to characterize the immunoglobulin loci of A. mexicanum and compare it with other model vertebrates.MethodsThe most recently published genome sequence of A. mexicanum (V6) was used for alignment-based annotation and manual curation using previously described axolotl Ig sequences or reference sequences from other vertebrates. Gene models were further curated using A. mexicanum spleen RNA-seq data. Human, Xenopus tropicalis, Danio rerio (zebrafish), and eight tetrapod reference genomes were used for comparison.ResultsCanonical A. mexicanum heavy chain (IGH), lambda (IGL), sigma (IGS), and the putative surrogate light chain (SLC) loci were identified. No kappa locus was found. More than half of the IGHV genes and the IGHF gene are pseudogenes and there is no clan I IGHV genes. Although the IGH locus size is proportional to genome size, we found local size restriction in the IGHM gene and the V gene intergenic distances. In addition, there were V genes with abnormally large V-intron sizes, which correlated with loss of gene functionality.ConclusionThe A. mexicanum immunoglobulin loci share the same general genome architecture as most studied tetrapods. Consistent with its large genome, Ig loci are larger; however, local size restrictions indicate evolutionary constraints likely to be imposed by high transcriptional demand of certain Ig genes, as well as the V(D)J recombination over very long genomic distance ranges. The A. mexicanum has undergone an extensive process of Ig gene loss which partially explains a reduced potential repertoire diversity that may contribute to its impaired antibody response

Infección experimental de hepatobacteria necrotizante (NHPB) en Penaeus vannamei con florfenicol y oxitetraciclina: un estudio experimental comparativo

The present study is aimed to necrotising hepatobacterium (NHPB) infection, development in juvenile of Penaeus vannamei with florfenicol (FF) (1.000g/kg biomass) and oxytetracycline (OTC) (6.070 g/kg biomass). HPLC analysis was used to confirm the antibiotics in food and samples, wet mount analysis, conventional histopathology, PCR and in situ hybridization were used to assess the prevalence, mortality and severity of NHP and to confirm NHPB infection. Wet-mount analysis and histopathological results demonstrated that the Penaeus vannamei fed with OTC had 100% NHPB prevalence disease severity index 1 (10%), 2 (28%), 3 (35%) and 4 (27%); meanwhile, P. vannamei fed with FF had 100% NHPB prevalence at disease severity index 1 (16%), 2 (36%), 3 (20%) and 4 (28%). The positive control had disease severity index 1 (10%), 2 (10%), 3 (80%) and 4 (0%); no disease NHP-B signs were revealed by the negative control. A weak positive signal was shown by the in situ hybridization from the 9th day, and a positive signal from the 15nd day. The results derived by the High-performance liquid chromatography (HPLC) analysis demonstrated that the maximum OTC level was in muscle (on the 6th and 7th day, respectively) and the FF level in hepatopancreas (HP), followed by muscle. It was conclude that FF and OTC used in medicated feed as an effective treatment in the control of NHPB disease in P. vannamei when the medication is supplied in disease severity index 1 and 2.72 - [email protected] presente estudio tuvo como objetivo la infección y desarrollo experimental de la hepatobacteria necrotizante (NHPB) en juveniles de Penaeus vannamei, con florfenicol (FF) (biomasa 1.000g/kg) y oxitetraciclina (OTC) (6,070 g / kg de biomasa). El análisis por HPLC se utilizó para confirmar los antibióticos en alimento y organismos, los análisis de montaje húmedo, histopatología convencional, PCR e hibridación in situ se utilizaron para evaluar la prevalencia, la mortalidad y el grado de severidad de NHP y para confirmar la infección NHPB. Por análisis en fresco e histopatología se observó que los organismos alimentados con OTC tenían 100% de prevalencia de NHP con un índice de severidad de la enfermedad de 1 (32%), 2 (28%), 3 (35%) y 4 (27%) y los organismos alimentados con FF presentaron el 100% de NHPB con un índice de severidad de la enfermedad de 1(16%), 2 (36%), 3 (20%) y 4 (28%). El control positivo presentó un índice de severidad de la enfermedad de 1 (10%), 2 (10%), 3 (80%) y 4 (0%), no se detectó NHPB en ninguna muestra del control negativo. Por hibridación in situ se observó una señal positiva débil al noveno día de infección y una señal intensa después del quinceavo día. Los resultados por cromatografía líquida de alta resolución (HPLC) muestran que el nivel máximo de OTC fue al sexto y séptimo día de tratamiento en músculo y el nivel máximo de FF se detectó en hepatopáncreas, seguido por el músculo al tercer y cuarto día de tratamiento. Los resultados de este trabajo muestran que los dos antibióticos, inhiben el crecimiento de NHPB, cuando la medicación se suministra con un índice de severidad de la enfermedad entre 1 y 2

New Insights into the Mechanism of Action of PirAB from Vibrio Parahaemolyticus

PirAB toxins secreted by Vibrio parahaemolyticus (Vp) harbor the pVA1 virulence plasmid, which causes acute hepatopancreatic necrosis disease (AHPND), an emerging disease in Penaeid shrimp that can cause 70–100% mortality and that has resulted in great economic losses since its first appearance. The cytotoxic effect of PirABVp on the epithelial cells of the shrimp hepatopancreas (Hp) has been extensively documented. New insights into the biological role of the PirBVp subunit show that it has lectin-like activity and recognizes mucin-like O-glycosidic structures in the shrimp Hp. The search for toxin receptors can lead to a better understanding of the infection mechanisms of the pathogen and the prevention of the host disease by blocking toxin–receptor interactions using a mimetic antagonist. There is also evidence that Vp AHPND changes the community structure of the microbiota in the surrounding water, resulting in a significant reduction of several bacterial taxa, especially Neptuniibacter spp. Considering these findings, the PirABvp toxin could exhibit a dual role of damaging the shrimp Hp while killing the surrounding bacteria

New Insights into the Mechanism of Action of PirAB from Vibrio Parahaemolyticus

PirAB toxins secreted by Vibrio parahaemolyticus (Vp) harbor the pVA1 virulence plasmid, which causes acute hepatopancreatic necrosis disease (AHPND), an emerging disease in Penaeid shrimp that can cause 70–100% mortality and that has resulted in great economic losses since its first appearance. The cytotoxic effect of PirABVp on the epithelial cells of the shrimp hepatopancreas (Hp) has been extensively documented. New insights into the biological role of the PirBVp subunit show that it has lectin-like activity and recognizes mucin-like O-glycosidic structures in the shrimp Hp. The search for toxin receptors can lead to a better understanding of the infection mechanisms of the pathogen and the prevention of the host disease by blocking toxin–receptor interactions using a mimetic antagonist. There is also evidence that Vp AHPND changes the community structure of the microbiota in the surrounding water, resulting in a significant reduction of several bacterial taxa, especially Neptuniibacter spp. Considering these findings, the PirABvp toxin could exhibit a dual role of damaging the shrimp Hp while killing the surrounding bacteria

Histological effects of Cu2+ to white shrimp Litopenaeus vannamei (Crustacea: Decapoda) juveniles at low salinities

Juveniles of the white shrimp Litopenaeus vannamei were exposed during 25 days to the Cu2+ concentration commonly used in Mexican shrimp farms, at salinities of 1, 5, and 10 psu, in order to observe possible histological alterations to the antennal glands, midgut, gills and hepatopancreas. Survival was 100% in controls and treatments, and no histopathologies were observed in gills, midgut and antennal glands. Sloughing of epithelial cells (< 75%), infiltration of hemocytes (< 75%) and reduction in R and B cells (100%) were observed after 10 days in the hepatopancreas of shrimps exposed to Cu2+ at the lowest salinity and, to a lower degree, at salinities of 5 and 10 psu. This should be taken into consideration to establish criteria of acceptable water quality for inland aquaculture, because the interaction metal-salinity may induce adverse shrimp responses.Juveniles del camarón blanco Litopenaeus vannamei fueron expuestos durante 25 días a salinidades de 1, 5, y 10 ups y a la concentración de Cu2+ que se usa comúnmente en las granjas camaronícolas de México, con el propósito de observar posibles alteraciones histológicas en la glándula antenal, intestino medio, branquias y hepatopáncreas. La supervivencia fue de 100% en controles y tratamientos y no se observaron histopatologías en branquias, intestino y glándula antenal. Después de 10 días de exposición al Cu2+ a la salinidad más baja, se observaron en el hepatopáncreas desprendimiento de las células epiteliales (< 75%), infiltración de hemocitos (< 75%), y una reducción de las células R y B (100%). Las mismas alteraciones se presentaron, aunque en menor grado, a las salinidades de 5 y 10 ups. Estos efectos deberían ser considerados para establecer criterios de calidad de agua para el cultivo de camarón en agua continentales, debido a que la interacción metal-salinidad puede inducir respuestas adversas en los camarones