Cyclophosphamide modulated the foreign body inflammatory reaction in tilapia (Oreochromis niloticus).

In order to understand events and mechanisms present in the pathophysiology of tilapia's chronic inflammation and based on the immunomodulatory activity attributed to cyclophosphamide which is widely used to suppress immune responses in human medicine, the present study investigated the effects of cyclophosphamide (CYP) treatment on the modulation of foreign body inflammatory reaction in Nile tilapia (Oreochromis niloticus) with round glass coverslip implanted in the subcutaneous tissue (9 mm of diameter). Forty tilapia (151 ± 10,2 g) were randomly distributed in 5 aquariums (n = 8) with a capacity of 250 L of water each, to compose two treatments (sampled 3 and 6 days post-implantation): implanted/untreated (control) and implanted/treated with 200 mg of CYP kg-1 of b.w., through i.p. route. A fifth group (n = 8) was sampled without any stimulus (naive) to obtain reference values. CYP-treated tilapia showed decrease in macrophage accumulation, giant cell formation and Langhans cells on the glass coverslip when compared to control fish. The treatment with CYP resulted in decrease of leukocyte and thrombocyte counts. Decrease in alpha-2-macroglobulin, ceruloplasmin, albumin and transferrin levels, as well as increase in haptoglobin, complement C3 and apolipoprotein A1 were observed in tilapias during foreign body inflammation. Blood levels of complement C3, alpha-2-macroglobulin, ceruloplasmin and transferrin were modulated by treatment with CYP. Therefore, the treatment with 200 mg of CYP kg-1 of b.w. in tilapia resulted in an anti-inflammatory effect by suppressing the dynamics between leukocytes in the bloodstream and macrophage accumulation with giant cell formation in the inflamed focus, as well as by modulating APPs during foreign body reaction.

Immune responses induced by inactivated vaccine against Aeromonas hydrophila in pacu, Piaractus mesopotamicus.

Aeromonas hydrophila is responsible for outbreaks of a severe infectious disease in fish farms around the world and is one of the major causes of economic losses to the neotropical fish farmers. This study assessed the induction of immune responses and protection against A. hydrophila in pacu, Piaractus mesopotamicus, vaccinated through intraperitoneal and immersion route with inactivated virulent strain. Fish were randomly distributed in three vaccinated groups: intraperitoneal (i.p.) route; immersion; and immersion + booster; and control group (unvaccinated). All vaccination protocols used the concentration of 1.7 × 108 CFU mL-1 of inactivated A. hydrophila., and an oil adjuvant was used for vaccine prepararion for i.p. route vaccination. Blood and skin mucus from 9 fishes per treatment were collected at 14, 28, 42 and 84 days post-vaccination (DPV) for determination of lysozyme concentration in skin mucus, as well as antibodies anti-A. hydrophila in blood serum and skin mucus. Fish were challenged at 84 DPV with homologous and virulent strain of A. hydrophila for evaluation of resistance against bacterial infection. The results demonstrated that vaccination with inactivated A. hydrophila suspension by i.p. or immersion resulted in significant increase of skin mucus lysozyme and specific antibody levels in serum and skin mucus, at 28 and 42 DPV, and this increase in innate and adaptive immunity remained significant in pacu vaccinated through i.p. route up to 84 DPV. Although no significant differences were observed in the survival study, pacu vaccinated through i.p. route presented 31,33% of relative percentage survival (RPS) in LD50-96h when compared unvaccinated fish challenged at 84 DPV. The results observed in this study indicate that vaccination programs with inactivated A. hydrophila, including booster doses by i.p. or immersion routes, could result in more effective protection in pacu against this bacteriosis, by increasing innate and adaptive mucosal and systemic immune responses.

Spleen melanomacrophage centers response of Nile tilapia during Aeromanas hydrophila and Mycobacterium marinum infections.

In order to understand the pathophysiology of melanomcrophage centers (MMCs) formation during the tilapia defense response to bacterial infections, the present study evaluated the response, in terms of area, number and pigment constitution, of splenic MMCs of Oreochromis niloticus subjected to intraperitoneal (i.p.) infection with Aeromonas hydrophila and Mycobacterium marinum. Eighty-four fish (396.9 ±â€¯21.0 g) were randomly distributed into twelve plastic tanks (300 L), to constitute three treatments with 28 animals each: control group (inoculated with PBS); Infected with A. hydrophila (1 × 107 UFC mL-1); Infected with M. marinum (1 × 106 UFC mL-1). The spleen was collected in seven fish per treatment on the 3rd, 7th, 14th and 21st day post-infection (DPI). The results revealed the participation of MMCs in the defense response of tilapia during bacterial infection by A. hydrophila and M. marinum, since there was an increase in the number and size of these cell aggregates. Variation of pigment accumulation with significant increase of hemosiderin, in infected tilapias by A. hydrophila, bacteria responsible for causing hemolytic anemia in fish was also found. On the other hand, M. marinum-infected tilapia had high amount of melanin in MMCs. In general, mycobacterial infections are notoriously difficult to treat, being characterized as a chronic disease. These findings demonstrate different strategies of fish response during the evolution of these bacterial diseases.