Effect of Feeding Rate on Survival, Zootechnical Performance of Tilapia Oreochromis niloticus (Linnaeus, 1758) Brazil Strain Larvae Fed on 17-α-methyltestosterone Treated Feed

This study was conducted to evaluate the feeding levels on survival, growth performance and feed utilization in the Brazil strain of Nile tilapia Oreochromis niloticus. Four (4) batches of larvae with mean initial weight 0.012 ± 0.005 g and mean initial total length 9 ± 0.003 mm were formed in triplicate, three per feeding rate. The rationing rates according to fry biomass applied in this trial were: batch 1: 50, 40, 30 and 25%, batch 2: 40, 30, 25 and 20%, batch 3: 30, 25, 20 and 18% and batch 4: 25, 20, 18 and 15% of biomass. The different feeding rates were tested during the 1st, 2nd, 3rd and 4th week of larval rearing respectively. The fish were all fed a commercial feed (48% protein) distributed manually at a frequency of 5 meals per day. After 28 days of rearing, the results show that apart from the survival rate, the other parameters such as final average weight, daily growth and food consumption index were affected by the different rationing rates tested. The larvae of batch 2 rationed at 40, 30, 25 and 20 % of their biomass during the 1st, 2nd, 3rd and 4th week of rearing respectively recorded significantly higher growth parameters (MWF: 1.092±0.027 g and DG: 0.038±0.000 g) and a more interesting food converion ratio (0.88 ) than the other batches of fry. From this study, it is concluded that an optimal feeding rate of 40, 30, 25 and 20% of the larval biomass during the 1st, 2nd, 3rd and 4th week of rearing, respectively, should be applied in order to avoid either wastage or underfeeding of the subjects during hormone treatment with 17 α-methyltestosterone.

Isolation and Molecular Characteristics of a CIAV Isolate From Pigeons, China

Chicken infectious anemia virus (CIAV) mainly infects chickens and causes immunosuppression. In this study, a CIAV isolate, designated as Pigeon-CIAV-1906, was efficiently isolated from two sick pigeons by inoculating the samples into MSB1 cells. The genome of Pigeon-CIAV-1906 was amplified by PCR and analyzed. The genome size of Pigeon-CIAV-1906 was 2,298 bp with the highest homology (99.5%) to Jilin strain (JL14023) and the lowest homology (91.5%) to Brazil strain (KY024579), which phylogenetically clustered into Group A. Notably, several amino acids such as 139K and 394Q related with high virulence were found in the VP1 of Pigeon-CIAV-1906. The isolation of Pigeon-CIAV-1906 and its molecular characteristics provide evidence for the cross-transmission of CIAV from chicken to pigeon and give novel insights into the molecular epidemiology of CIAV.

Epitope Classification and RBD Binding Properties of Neutralizing Antibodies Against SARS-CoV-2 Variants of Concern

Severe acute respiratory syndrome coronavirus-2 (SAR-CoV-2) causes coronavirus disease 2019 (COVID19) that is responsible for short and long-term disease, as well as death, in susceptible hosts. The receptor binding domain (RBD) of the SARS-CoV-2 Spike (S) protein binds to cell surface angiotensin converting enzyme type-II (ACE2) to initiate viral attachment and ultimately viral pathogenesis. The SARS-CoV-2 S RBD is a major target of neutralizing antibodies (NAbs) that block RBD - ACE2 interactions. In this report, NAb-RBD binding epitopes in the protein databank were classified as C1, C1D, C2, C3, or C4, using a RBD binding profile (BP), based on NAb-specific RBD buried surface area and used to predict the binding epitopes of a series of uncharacterized NAbs. Naturally occurring SARS-CoV-2 RBD sequence variation was also quantified to predict NAb binding sensitivities to the RBD-variants. NAb and ACE2 binding studies confirmed the NAb classifications and determined whether the RBD variants enhanced ACE2 binding to promote viral infectivity, and/or disrupted NAb binding to evade the host immune response. Of 9 single RBD mutants evaluated, K417T, E484K, and N501Y disrupted binding of 65% of the NAbs evaluated, consistent with the assignment of the SARS-CoV-2 P.1 Japan/Brazil strain as a variant of concern (VoC). RBD variants E484K and N501Y exhibited ACE2 binding equivalent to a Wuhan-1 reference SARS-CoV-2 RBD. While slightly less disruptive to NAb binding, L452R enhanced ACE2 binding affinity. Thus, the L452R mutant, associated with the SARS-CoV-2 California VoC (B.1.427/B.1.429-California), has evolved to enhance ACE2 binding, while simultaneously disrupting C1 and C2 NAb classes. The analysis also identified a non-overlapping antibody pair (1213H7 and 1215D1) that bound to all SARS-CoV-2 RBD variants evaluated, representing an excellent therapeutic option for treatment of SARS-CoV-2 WT and VoC strains.

Epitope classification and RBD binding properties of neutralizing antibodies against SARS-CoV-2 variants of concern

Severe acute respiratory syndrome coronavirus-2 (SAR-CoV-2) causes coronavirus disease 2019 (COVID19) that is responsible for short and long-term disease, as well as death, in susceptible hosts. The receptor binding domain (RBD) of the SARS-CoV-2 Spike (S) protein binds to cell surface angiotensin converting enzyme type-II (ACE2) to initiate viral attachment and ultimately viral pathogenesis. The SARS-CoV-2 S RBD is a major target of neutralizing antibodies (NAbs) that block RBD - ACE2 interactions. In this report, NAb-RBD binding epitopes in the protein databank were classified as C1, C1D, C2, C3, or C4, using a RBD binding profile (BP), based on NAb-specific RBD buried surface area and used to predict the binding epitopes of a series of uncharacterized NAbs. Naturally occurring SARS-CoV-2 RBD sequence variation was also quantified to predict NAb binding sensitivities to the RBD-variants. NAb and ACE2 binding studies confirmed the NAb classifications and determined whether the RBD variants enhanced ACE2 binding to promote viral infectivity, and/or disrupted NAb binding to evade the host immune response. Of 9 single RBD mutants evaluated, K417T, E484K, and N501Y disrupted binding of 65% of the NAbs evaluated, consistent with the assignment of the SARS-CoV-2 P.1 Japan/Brazil strain as a variant of concern (VoC). RBD variants E484K and N501Y exhibited ACE2 binding equivalent to a Wuhan-1 reference SARS-CoV-2 RBD. While slightly less disruptive to NAb binding, L452R enhanced ACE2 binding affinity. Thus, the L452R mutant, associated with the SARS-CoV-2 California VoC (B.1.427/B.1.429-California), has evolved to enhance ACE2 binding, while simultaneously disrupting C1 and C2 NAb classes. The analysis also identified a non-overlapping antibody pair (1213H7 and 1215D1) that bound to all SARS-CoV-2 RBD variants evaluated, representing an excellent therapeutic option for treatment of SARS-CoV-2 WT and VoC strains.

High-Quality Draft Genome Sequence Resources of Eight Xylella fastidiosa Strains Isolated from Citrus, Coffee, Plum, and Hibiscus in South America

Xylella fastidiosa subsp. pauca, once confined to South America and infecting mainly citrus and coffee plants, has been found to be associated with other hosts and in other geographic regions. We present high-quality draft genome sequences of X. fastidiosa subsp. pauca strains J1a12, B111, U24D, and XRB isolated from citrus plants in Brazil, strain Fb7 isolated from a citrus plant in Argentina and strains 3124, Pr8x, and Hib4 isolated, respectively, from coffee, plum, and hibiscus plants in Brazil. Sequencing was performed using Roche 454-GS FLX, MiSeq-Illumina or Pacific Biosciences platforms. These high-quality genome assemblies will be useful for further studies about the genomic diversity, evolution, and biology of X. fastidiosa.

Screening of protease, cellulase, amylase and xylanase from the salt-tolerant and thermostable marine Bacillus subtilis strain SR60

Background:The marine environment harbours different microorganisms that inhabit niches with adverse conditions, such as temperature variation, pressure and salinity. To survive these particular conditions, marine bacteria use unique metabolic and biochemical features, producing enzymes that may have industrial value.Methods:The aim of this study was to observe the production of multiple thermoenzymes and haloenzymes, including protease, cellulase, amylase and xylanase, from bacterial strains isolated from coral reefs Cabo Branco, Paraiba State, Brazil. Strain SR60 was identified by the phylogenetic analysis to beBacillus subtilisthrough a 16S ribosomal RNA assay. To screening of multiples enzymesB. subtilisSR60 was inoculated in differential media to elicit the production of extracellular enzymes with the addition of a range of salt concentrations (0, 0.25, 0.50, 1.0, 1.25 and 1.5 M NaCl).Results:The screening showed a capacity of production of halotolerant protease, cellulase, amylase and xylanase and thermostable by the isolate (identified asB. subtilisSR60). Protease, cellulase, amylase and xylanase production were limited to 1.5, 1.5, 1.0 and 1.25 M NaCl, respectively.Conclusions:Bacillus subtilisSR60 was shown in this study be capable of producing protease, cellulase, amylase and xylanase when submitted to a high salinity environment. These data demonstrate the halophytic nature of SR60 and its ability to produce multiples enzymes.

Modulation of Autoimmunity by Treatment of an Infectious Disease

ABSTRACT Chagas’ heart disease (CHD), caused by the parasite Trypanosoma cruzi, is the most common form of myocarditis in Central America and South America. Some humans and experimental animals develop both humoral and cell-mediated cardiac-specific autoimmunity during infection. Benznidazole, a trypanocidal drug, is effective at reducing parasite load and decreasing the severity of myocarditis in acutely infected patients. We hypothesized that the magnitude of autoimmunity that develops following T. cruzi infection is directly proportional to the amount of damage caused by the parasite. To test this hypothesis, we used benznidazole to reduce the number of parasites in an experimental model of CHD and determined whether this treatment altered the autoimmune response. Infection of A/J mice with the Brazil strain of T. cruzi leads to the development of severe inflammation, fibrosis, necrosis, and parasitosis in the heart accompanied by vigorous cardiac myosin-specific delayed-type hypersensitivity (DTH) and antibody production at 21 days postinfection. Mice succumbed to infection within a month if left untreated. Treatment of infected mice with benznidazole eliminated mortality and decreased disease severity. Treatment also reduced cardiac myosin-specific DTH and antibody production. Reinfection of treated mice with a heart-derived, virulent strain of T. cruzi or immunization with myosin led to the redevelopment of myosin-specific autoimmune responses and inflammation. These results provide a direct link between the levels of T. cruzi and the presence of autoimmunity and suggest that elimination of the parasite may result in the reduction or elimination of autoimmunity in the chronic phase of infection.

Role of Endothelin 1 in the Pathogenesis of Chronic Chagasic Heart Disease

ABSTRACT On the basis of previous observations, endothelin 1 (ET-1) has been suggested as contributing to the pathogenesis of Chagasic cardiomyopathy. Therefore, ET-1flox/flox;α-MHC-Cre(+) mice in which the ET-1 gene was deleted from cardiac myocytes and ET-1flox/flox;Tie 2 Cre(+) mice in which the ET-1 gene was deleted from endothelial cells were infected with Trypanosoma cruzi. Genetic controls for these cell-specific ET-1 knockout mice were used. Ninety percentage of all mice survived acute infection with the Brazil strain and were evaluated 130 days postinfection. Inflammation and fibrosis were observed in all infected mice; however, fibrosis was reduced in ET-1flox/flox;α-MHC-Cre(+) mice. Cardiac magnetic resonance imaging revealed that infection resulted in a significant increase in right ventricular internal diameter (RVID) in all mice except ET-1flox/flox;α-MHC-Cre(+) mice; i.e., RVID was not changed in infected ET-1flox/flox;α-MHC-Cre(+) mice. Echocardiography of the left ventricle demonstrated increased left ventricular end-diastolic diameter, reduced fractional shortening, and decreased relative wall thickness in infected mice. However, the magnitude of the changes was significantly less in ET-1flox/flox;α-MHC-Cre(+) mice compared to other groups. These data provide further evidence of a role for ET-1, particularly cardiac myocyte-derived ET-1, in the pathogenesis of chronic Chagasic cardiomyopathy.