Acute-phase protein (APPs) serum levels have been studied in many human diseases, and their components contribute to host defense during the evolution of infectious diseases by acting as part of the innate immune system. Based on the importance of establishing new experimental models, the present investigation evaluated the modulation of APPs following inflammatory stimulus by the inoculation of Aeromonas hydrophila in tilapias. Fish were sampled 6 and 24 hours post-infection. Tilapias presented increase of positive APPs such as ceruloplasmin, haptoglobin, alpha-2-macroglobulin and complement C3, as well as decrease of negative APPs such as albumin and transferrin. The protein response of tilapias during the course of bacterial infection showed correlation with the kinetics of cellular accumulation in the inflamed focus with significant increase of granulocytes, thrombocytes, lymphocytes and macrophages. However, granulocytes were the predominant cells, associated with increment in the reactive oxygen species (ROS) production. Showing responses similar to those observed in humans, the modulation of APPs and the kinetics of cellular accumulation in the exudate demonstrate the feasibility of this alternative experimental model for advances and studies to understand changes in pathophysiological mechanisms of acute inflammatory reaction due to bacterial infection.

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Streptococcus agalactiae (Sta), which belongs to Lancefield group B, causes sepsis, endocarditis and bacterial meningitis in human neonates and Nile tilapia. Because the pathophysiology of Sta infection is partially similar in both species, the identification of biomarkers for the diagnosis and study of this disease is of importance for human and animal health. Therefore, in the present study, we produced an immunoglobulin Y (IgY) by immunizing laying hens with Sta proteins and evaluated its ability to detect Sta in paraffinized tilapia brain and cardiac tissue by direct immunofluorescence (IMF) and indirect immunohistochemistry (IHC). The IgY produced was effective in the diagnosis of Sta infection in Nile tilapia, justifying the use of this species as a biomodel for the study of this disease.

Understanding the functional mechanisms of the humoral and cellular immune responses among teleost broadens the possibilities for intervention and improvement of vaccination methods. The aim of this study was to evaluate the dynamics of the humoral immune response, hematological biochemical changes, and electrophoretic profile of proteins in Oreochromis niloticus, when submitted to antigen stimulation using sheep erythrocytes in a single dose and with booster doses. Seventy O. niloticus were distributed in two groups (n=35): one received a single dose and the other received two doses of antigen. Evaluations were made at the following predetermined times: zero (pre-immune, i.e., before inoculation with the first injection of sheep erythrocytes, negative control) and on 7th, 14th, 21st, and 28th days after the first immunization to evaluate the hemogram, biochemistry, and electrophoresis of proteins and direct hemagglutination. Twenty-eight days after antigen inoculation, it was observed that there had been an increase in the serum antibody titer and fractions gamma globulins after second antigen stimulation. The results suggest that teleost fish have the capacity to produce antibodies from a single stimulation, and a second antibody production wave after second stimulation.

Parasitic diseases are a neglected and serious problem, especially in underdeveloped countries. Among the major parasitic diseases, Leishmaniasis figures as an urgent challenge due to its high incidence and severity. At the same time, the indiscriminate use of antibiotics by the population is increasing together with resistance to medicines. To address this problem, new antibiotic-like molecules that directly kill or inhibit the growth of microorganisms are necessary, where antimicrobial peptides (AMPs) can be of great help. In this work, the ferrocene molecule, one active compound with low levels of in vivo toxicity, was coupled to the N-terminus of the RP1 peptide (derived from the human chemokine CXCL4), aiming to evaluate how this change modifies the structure, biological activity, and toxicity of the peptide. The peptide and the conjugate were synthesized using the solid phase peptide synthesis (SPPS). Circular dichroism assays in PBS showed that the RP1 peptide and its conjugate had a typical spectrum for disordered structures. The Fc-RP1 presented antiamastigote activity against Leishmania amazonensis (IC 50 = 0.25 μmol L -1 ). In comparison with amphotericin B, a second-line drug approved for leishmaniasis treatment, (IC 50 = 0.63 μmol L -1 ), Fc-RP1 was more active and showed a 2.5-fold higher selectivity index. The RP1 peptide presented a MIC of 4.3 μmol L -1 against S. agalactiae, whilst Fc-RP1 was four times more active (MIC = 0.96 μmol L -1 ), indicating that ferrocene improved the antimicrobial activity against Gram-positive bacteria. The Fc-RP1 peptide also decreased the minimum inhibitory concentration (MIC) in the assays against E. faecalis (MIC = 7.9 μmol L -1 ), E. coli (MIC = 3.9 μmol L -1 ) and S. aureus (MIC = 3.9 μmol L -1 ). The cytotoxicity of the compounds was tested against HaCaT cells, and no significant activity at the highest concentration tested (500 μg. mL -1 ) was observed, showing the high potential of this new compound as a possible new drug. The coupling of ferrocene also increased the vesicle permeabilization of the peptide, showing a direct relation between high peptide concentration and high carboxyfluorescein release, which indicates the action mechanism by pore formation on the vesicles. Several studies have shown that ferrocene destabilizes cell membranes through lipid peroxidation, leading to cell lysis. It is noteworthy that the Fc-RP1 peptide synthesized here PLOS ONE

Uncaria tomentosa is a medicinal plant used in folk medicine by Amazon tribes. In this study the constituents of aqueous extract of U. tomentosa bark were quantified by chromatographic technique and its lethal concentration 50 (48 h) in Hyphessobrycon eques was determined. The chromatography showed high levels of oxindole alkaloids, quinovic acid glycosides, and low molecular weight polyphenols. The CL50 48 h was 1816 mg/L. Fish showed behavior changes at concentrations above 2000 mg/L, accompanied by a significant decrease of dissolved oxygen. At the highest concentration 100% mortality was observed attributed to oxygen reduction by the amount of oxindole alkaloids, polyphenols accumulation of the extract in the gills, and the interaction of these compounds with dopamine. In conclusion, the aqueous extract of U. tomentosa did not alter the chemical components and it was shown that U. tomentosa has low toxicity to H. eques; therefore, it can be used safely in this species.