Serum Complement Activity Research Articles

Tongue sole (Cynoglossus semilaevis) CD59: A complement inhibitor that binds bacterial cells and promotes bacterial escape from the killing of fish serum

CD59 is a complement regulatory protein that inhibits the formation of membrane attack complex of complement. In this study, we examined the expression and activity of tongue sole (Cynoglossus semilaevis) CD59 (CsCD59). CsCD59 possesses the conserved structural features of CD59 and shares 33%–46% sequence identities with other fish CD59. Expression of CsCD59 was high in liver, spleen, and muscle, and was stimulated by infection of bacterial pathogens. Recombinant CsCD59 (rCsCD59) exhibited an apparent inhibition effect on the activation of tongue sole serum complement. ELISA and microscopy detected binding of rCsCD59 to a number of Gram-negative and Gram-positive bacteria. Interaction with rCsCD59 did not affect bacterial viability but significantly enhanced bacterial resistance against the killing effect of fish serum. Together these results indicate that fish CD59 may to some degrees facilitate a general escape of bacteria from complement-mediated immunity.

Can heat-killed Gordonia bronchialis enhance growth and immunity in rainbow trout (Oncorhynchus mykiss )?

In this study, the efficacy of heat-killed Gordonia bronchialis on growth performance, immune system and gastrointestinal structure in rainbow trout (Oncorhynchus mykiss) was evaluated. Fish (mean weight 30 g) were fed basal diet (control), or treatment diets containing 2.48 × 108 (low dose) or 1.24 × 109 (high dose) cells kg−1 feed of heat-killed G. bronchialis on a pulse basis (5 days on treatment diet; 10 days on basal diet) for 95 days. On days 95 and 105, some of the fish were sampled for analysis of mentioned parameters. On days 110 and 120, the remaining fish were injected intraperitoneally with a 20 mL L−1 suspension of chicken red blood cells. Results showed that growth performance was significantly enhanced in both treatment groups compared with the control group. Serum complement and lysozyme activities and hemagglutination antibody titre were higher in both treatment groups compared with the control group. The length of the intestinal and pyloric caeca folds was increased in the high-dose group. Meanwhile, the number of goblet cells was increased in both treatment groups. This study suggests that heat-killed G. bronchialis has the potential to enhance growth, immunological parameters and the gastrointestinal structure in rainbow trout.

Association of C4B copy number variation and serum complement activation in vitro in patients with pediatric–onset inflammatory bowel disease

Association of C4B copy number variation and serum complement activation in vitro in patients with pediatric–onset inflammatory bowel disease

Thrombomodulin enhances complement regulation through strong affinity interactions with factor H and C3b-Factor H complex

IntroductionCoagulation and complement systems are simultaneously activated at sites of tissue injury, leading to thrombin generation and opsonisation with C3b. Thrombomodulin (TM) is a cell-bound regulator of thrombin activation, but can also enhance the regulatory activity of complement factor H (FH), thus accelerating the degradation of C3b into inactive iC3b. ObjectivesThis study sought to determine the biophysical interaction affinities of two recombinant TM analogs with thrombin, FH and C3b in order to analyze their ability to regulate serum complement activity. MethodsSurface plasmon resonance (SPR) analysis was used to determine binding affinities of TM analogs with FH and C3b, and compared to thrombin as positive control. The capacity of the two recombinant TM analogs to regulate complement in serum was tested in standard complement hemolytic activity assays. ResultsSPR analysis showed that both TM analogs bind FH and C3b-Factor H with nanomolar and C3b with micromolar affinity; binding affinity for its natural ligand thrombin was several fold higher than for FH. At a physiological relevant concentration, TM inhibits complement hemolytic activity in serum via FH dependent and independent mechanisms. ConclusionsTM exhibits significant binding affinity for complement protein FH and C3b-FH complex and its soluble form is capable at physiologically relevant concentrations of inhibiting complement activation in serum.

The dysfunction of platelets in paroxysmal nocturnal hemoglobinuria

IntroductionThrombosis is a dangerous complication of paroxysmal nocturnal hemoglobinuria (PNH) and has a high mortality rate. However, the mechanism underlying the development of thrombosis in PNH remains unclear. To explore this, platelet function and serum complement activity were investigated in 14 patients with classical PNH, 11 with PNH aplastic anemia (AA) and 30 healthy controls. Material and methodsSerum concentrations of the terminal complement complex (sC5b-9) were determined by enzyme-linked immunofluorescence assay (ELISA), and the levels of C5b-9, CD61 and CD62p on platelet membranes were determined by flow cytometry. Clinical parameters were assessed, including D-dimer and platelet aggregation induced by adenosine diphosphate (ADP) and arachidonic acid (ARA). ResultsSerum sC5b-9 concentrations were significantly lower in the PNH/PNH-AA than in the control group (P<0.01). C5b-9 deposition was significantly higher on CD59− platelets than on CD59+ platelets in PNH/PNH-AA patients and healthy controls (P<0.01 for each). D-dimer concentration was significantly higher in PNH/PNH-AA patients – especially those with lactate dehydrogenase (LDH) concentrations>1000U/L – than in controls (P<0.05). CD61 (P<0.05) expression was lower on CD59+ platelets in PNH than in controls and CD5− platelets in PNH. Expression of CD62p (P<0.01) was lower on CD59− and CD59+ platelets (P<0.01) in PNH cases than in controls. Platelet aggregation stimulated by the agonists ADP and ARA in the PNH/PNH-AA patients was significantly lower than that in controls (P<0.05). ConclusionsThe adhesion and aggregation of platelets, especially of CD59+ platelets, were compensatively decreased in PNH/PNH-AA patients without active thrombosis.

Effect of atrazine on immunocompetence of red-eared slider turtle(Trachemys scripta)

The impact of agrichemicals on aquatic vertebrate species has been a matter of increasing concern to researchers and environmentalist. The present study aimed to evaluate the effect of atrazine (ATZ), a worldwide used herbicide, on some immune parameters of red-eared slider (Trachemys scripta). Twenty-four turtles (2 years old) were randomly distributed in four groups. Three groups were intraperitoneally injected once with one of three different doses of atrazine (0.01, 0.1 or 1.0 ng/g body mass), while one was maintained as control (saline injected). Blood samples were taken 1- and 2-week post-treatment. A positive correlation was found between atrazine (high dose) concentration and immunosuppressive effects as evidenced by lowered serum complement and lysozyme activities, reduced leucocyte number as well as their phagocytic activity and increased heterophil/lymphocyte ratio. These data demonstrate that turtles with elevated atrazine exposure exhibit immunomodulation.

Activation of serum complement in Posner-Schlossman syndrome patients

Background Activation of serum complement system is involved in the pathological process of uveitis and open angle glaucoma.Pathogenesis and pathological characteristics of Posner-Schlossman syndrome (PSS) are similar to uveitis and open angle glaucoma.However, etiology of PSS remains unelucidated.The activation complement in PSS patients’ serum is rarely reported. Objective The aim of this study was to investigate the activation of serum complement in PSS patients for PSS pathogenesis. Methods A prospective case-controlled study was designed.The peripheral blood simples of 79 PSS patients were collected from Shenzhen Eye Hospital during December 2013 to December 2015, and the peripheral blood simples were obtained from 83 unrelated healthy blood donors as healthy control group.Immuno-scatter turbidmetry was adopted to detect the common activated components in complement pathway in each group including complement C3 (a vital intersection molecule in the three pathways), C4 (the vital molecule both the complement classical and lectin pathways), split products C3a, soluble membrane attack complex (sC5b-9), C1q (complement classical pathway), L-ficolin (complement lectin pathway), complement factor Bb (complement alternative pathway), IgG, IgA and IgM.The correlation between serum C3a content and sC5b-9 content in PSS group was analyzed.The serum contents of fabric binding protein 2 (FCN2) (a marker of serum classical pathway), factor Bb (a marker of complement alternative pathway), C3a (the common activation products of three complement activation pathways), and sC5b-9 were assayed by ELISA.This research protocal was approved by Shenzhen Eye Hospital and written informed consent was obtained from each PSS patient prior to any medical examination. Results Compared with normal control group, the serum levels of C3, C4, C3a, sC5b-9, C1q, FCN2, IgG, IgA and IgM were significantly higher in PSS group (Z=-4.743, -2.913, -1.985, -2.620, -2.062, -2.500, -7.010, -6.327, -3.652, all at P<0.05). The serum complement factor Bb level was 13.87 (9.24, 32.00)μg/ml in PSS group, which was significantly lower than 20.51 (12.90, 33.50)μg/ml in normal control group (Z=-2.515, P=0.012). Serum C3a content was positively correlated with the serum sC5b-9 content in PSS group (rs=0.832, P<0.001). Conclusions The serum complement system is activated in PSS patients.Complement alternative pathway, classical pathway and lectin pathway might all be involved in the activative process of complement system. Key words: Glaucoma, open-angle; Syndrome; Iridocyclitis; Complement activation/ physiology; Complement pathway, activation /physiology

Chitosan based nanoparticles as protein carriers for efficient oral antigen delivery

This study aimed to investigate the efficacy of nanoparticles based on chitosan as a vehicle for oral antigen delivery in fish vaccination. Carboxymethyl chitosan/chitosan nanoparticles (CMCS/CS-NPs) loaded extracellular products (ECPs) of Vibrio anguillarum were successfully developed by ionic gelation method. The prepared ECPs-loaded CMCS/CS-NPs were characterized for various parameters including morphology, particle size (312±7.18nm), zeta potential (+17.4±0.38mV), loading efficiency (57.8±2.54%) and stability under the simulated gastrointestinal (GI) tract conditions in turbot. The in vitro profile showed that the cumulative release of ECPs from nanoparticles was higher in pH 7.4 (58%) than in pH 2.0 (37%) and pH 4.5 (29%) after 48h. Fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) was used as model protein antigen and encapsulated in CMCS/CS-NPs for investigating the biodistribution of antigen after oral delivery to turbot in 24h. Oral immunization of ECPs-loaded CMCS/CS-NPs group in turbot showed elevated specific antibody and higher concentrations of lysozyme activity and complement activity in fish serum than ECPs solution. CMCS/CS-NPs loaded with ECPs could enhance both adaptive and innate immune responses than the group treated with ECPs solution and suggested to be a potential antigen delivery system.

Repeated Administration of Hyaluronic Acid Coated Liposomes with Improved Pharmacokinetics and Reduced Immune Response.

PEGylated liposomes (PEG-Lip) have been widely used as a drug carrier for their good stealth property in blood circulation. However, the second injection of PEG-Lip was reported to result in the accelerated blood clearance (ABC) phenomenon and trigger hypersensitivity reactions in sensitive individuals for its complement activation effect. To avoid adverse immune responses, HA was selected to modify liposomes to afford HA modified liposomes (HA-Lip). Repeated administrations of PEG-Lip and HA-Lip were performed in rats. Our results showed that PEG-Lip induced the ABC phenomenon accompanied by a greatly increased accumulation of PEG-Lip in the liver. In contrast, HA-Lip showed good stealth property without inducing either the ABC phenomenon or an increase in liver uptake. Moreover, HA-Lip did not trigger complement activation in human serum in vitro and in rat blood in vivo. Consequently, HA modification represents a viable strategy to prolong the blood circulation time of liposomes without inducing the ABC phenomenon and adverse immune responses.

Studies of Pig Complement: Measurement of Pig CH50, ACH50, and Components

BackgroundOn the basis of a comparison of the hemolytic complement titer in pigs with that in humans, the complement system of pigs was investigated. The response of innate immunity, such as the natural antibodies, against humans was also examined. MethodsHemolytic complement activity of pig serum was measured with the use of a microtitration technique. CH50 was determined according to the method of Mayer. ACH50 was assayed according to the methods of Platts-Milles and Ishizaka. Hemolytic activities of C1, C4, C2, C3, C5, C8, and C9 were estimated through the use of intermediate cells and reagents, as described previously. In addition, the pig natural anti-human antibody was studied with the use of human peripheral blood mononuclear cells (PBMCs). Human PBMCs were stained with 5% pig serum, followed by staining with fluorescein isothiocyanate–labeled goat anti-pig IgG and IgM. The resulting stained cells were quantified by use of a FACScalibur system. The alternative pathway of pig complement was also measured with the use of human erythrocytes and normal pooled pig serum with or without Mg++EGTA. ResultsBoth the CH50 and ACH50 titers were lower than those of humans. Concerning the components, except for C3, each component, that is, C1, C4, C2, C5, C8, and C9, was also lower than that of humans, based on measured values for human complement components. Pig serum clearly contains natural antibodies, IgG and IgM, to human PBMCs. The alternative pathway of pig complement reacted with human erythrocytes. ConclusionsAs a whole, pig innate immunity, the complement system and natural antibody, recognizes the surfaces of human cells.

Complement-Mediated Death of Ciliate Tetrahymena pyriformis Caused by Human Blood Serum.

Toxicity of human blood serum for ciliate Tetrahymena pyriformis is determined by the complement system. When ciliate are dying after being exposed to blood serum, cell membrane permeability for low-molecular-weight compounds significantly increases, probably due to pore formation. Serine protease inhibitors or exposure to physical factors inducing complement inactivation (e.g., heating up to 56°C) completely prevented ciliate death under the effect of human serum. Activation of serum complement upon interaction with Tetrahymena cells occurred by the classical or lectin pathway, while the contribution of the alternative activation pathway was negligible.

The mechanisms of complement activation in normal bovine serum and normal horse serum against Yersinia enterocolitica O:9 strains with different outer membrane proteins content.

Yersinia enterocolitica is a common zoonotic pathogen and facultative intracellular bacterium which can survive within blood cells. Cattle and horses are considered a reservoir of Y. enterocolitica which often causes several serious syndromes associated with yersiniosis such as abortions, premature births or infertility. The aim of our investigation was to determine the vitality of Y. enterocolitica O:9 strains (Ye9) in bovine and horse sera (NBS and NHrS) and explain the role of outer membrane proteins (OMPs) in serum resistance of these bacteria. Our previous studies demonstrated moderate human serum (NHS) resistance of the wild type Ye9 strain, whereas mutants lacking YadA, Ail or OmpC remained sensitive to the bactericidal activity of NHS. The present study showed that the wild type of Ye9 strain was resistant to the bactericidal activity of both NHrS and NBS, while Ye9 mutants lacking the YadA, Ail and OmpC proteins were sensitive to NHrS and NBS as well as to NHS. The mechanisms of complement activation against Ye9 strains lacking Ail and YadA were distinguished, i.e. activation of the classical/lectin pathways decisive in the bactericidal mechanism of complement activation of NBS, parallel activation of the classical/lectin and alternative pathways of NHrS. In this research the mechanism of independent activation of the classical/lectin or the alternative pathway of NBS and NHrS against Ye9 lacking OmpC porin was also established. The results indicate that serum resistance of Ye9 is multifactorial, in which extracellular structures, i.e. outer membrane proteins (OMPs) such as Ail, OmpC or YadA, play the main role.

Direct evidence of complement activation in HELLP syndrome: A link to atypical hemolytic uremic syndrome.

HELLP syndrome (hemolysis, elevated liver enzymes, and low platelets) is a severe variant of pre-eclampsia whose pathogenesis remains unclear. Recent evidence and clinical similarities suggest a link to atypical hemolytic uremic syndrome, a disease of excessive activation of the alternative complement pathway effectively treated with a complement inhibitor, eculizumab. Therefore, we used a functional complement assay, the modified Ham test, to analyze sera of women with classic or atypical HELLP syndrome, pre-eclampsia with severe features, normal pregnancies, and healthy nonpregnant women. Sera were also evaluated using levels of the terminal product of complement activation (C5b-9). We tested the in vitro ability of eculizumab to inhibit complement activation in HELLP serum. Increased complement activation was observed in participants with classic or atypical HELLP compared with those with normal pregnancies and nonpregnant controls. Mixing HELLP serum with eculizumab-containing serum resulted in a significant decrease in cell killing compared with HELLP serum alone. We found that HELLP syndrome is associated with increased complement activation as assessed with the modified Ham test. This assay may aid in the diagnosis of HELLP syndrome and could confirm that its pathophysiology is related to that of atypical hemolytic uremic syndrome.

Typical Hus: Evidence of Acute Phase Complement Activation from a Daycare Outbreak.

The clinical manifestations of typical hemolytic uremic syndrome (HUS) encompass a wide spectrum. Despite the potentially severe sequelae from this syndrome, treatment approaches remain supportive. We present the clinical course of a child who contracted Shiga toxin-positive E. coli (STEC) from a daycare center during an outbreak. Utilizing the modified Ham test which is a rapid, serum-based functional assay used to detect activation of the alternative pathway of complement as observed in atypical HUS, patient sera revealed evidence of increased complement activation in the acute phase of the syndrome but not after resolution. Further, this complement activation was attenuated by eculizumab in vitro, an effect that was replicated in vitro utilizing Shiga toxin as a stimulus of complement activation in normal serum. Our report suggests that complement blockade may be effective in the treatment of STEC-HUS when initiated early in the disease. Given the epidemic nature of the disease that limits the feasibility of randomized clinical trials, further studies are needed to determine the value of early eculizumab treatment in STEC-HUS.

Increased stocking density causes changes in expression of selected stress- and immune-related genes, humoral innate immune parameters and stress responses of rainbow trout (Oncorhynchus mykiss).

The present study investigated the effects of various stocking densities on the health status (stress and immune responses) of rainbow trout (Onchorhynchus mykiss). Juvenile rainbow trout were acclimated, placed in circular tanks under stocking densities of 10, 40 and 80kgm(-3) and reared for 30 days. The relative expression of genes involved in stress and immunity such as HSP70, LyzII, TNF-1α, IL-1β, IL-8 and IFN-γ1 in the head kidney was determined. Serum cortisol, ACTH, total antioxidant capacity, osmolality and lactate were measured after 30 days of culture at different stocking densities (D1:10kgm(-3), D2: 40kgm(-3) and D3: 80kgm(-3)) as indices of stress responses. In addition, the effects of stocking densities on serum complement, bactericidal activity, agglutinating antibody titers, serum IgM, anti-protease activity, serum total protein and alkaline phosphatase of the fish were measured. HSP70 gene expression was significantly density-dependent upregulated in D2 and D3 densities compared to D1 (P<0.05). Also, there was significant downregulation in expression of LyzII, TNF-1α, IL-1β, IL-8 and IFN-γ1 in fish reared at density of either D2 or D3 (P<0.05). In terms of stress responses, serum ACTH, cortisol and lactate level showed significant density-dependent increase (P<0.05) while serum osmolality and total antioxidant capacity showed significant decline (P<0.05) in fish reared at higher densities (D2 and D3) compared to fish reared at lower density (D1) (P<0.05). Concordant with the expression of the immune-related genes, the serum complement and bactericidal activity as well as specific antibody titer against Aeromonas hydrophila, IgM and anti-protease activity decreased along with elevation of stocking density from D1 to D3 (P<0.05). However, different stocking densities had no significant effect on serum total protein level and alkaline phosphatase activity. These results suggested that elevation of stocking densities and crowding resulted in the increase in HSP70 gene expression and the levels of selected stress responses in the serum. However, there was down-regulation of immune genes expression and decreased innate immune responses in the fish. The mRNA expression of the genes and immune parameters that were measured in this study could be helpful in monitoring the health status and welfare of the fish in aquaculture systems particularly in relation to increased stocking densities.

A NEW METHOD TO ASSESS FUNCTIONAL ACTIVITY OF SERUM COMPLEMENT SYSTEM

Complement system is an important component of innate immunity, providing primary protection against pathogens invading the body. In addition, it was shown that the complement system is associated with many diseases, not only autoimmune and infectious, but also mental disorders. In this regard, it is necessary to develop affordable and fast method of measuring activity of the complement system in real-time mode. We present a new semi-automated method for assessment of serum complement activity. The assay is based on cytolytic action of complement system upon the ciliate organism Tetrahymena pyriformis. This method consists in repeated counting of live Tetrahymena motile cells by means of specially developed Biolat device, which consists of two video cameras, light sources, and movable round plate. The plate has two rows of holes. The device also includes microprocessor control unit based on AutoCiliata software, intended for control of operation module and counting the surviving cell. The calculations are based on fixation of two sequential video-frames, with subsequent software image processing. Cell death events were observed upon incubation in triethanolamine (TEA) buffer containing 5% of blood serum. We have also compared complement activity in different buffers, i.e., standard medium for culturing of ciliates, Veronal-Medinalum buffer, and the TEA buffer. TEA buffer was found superior to the Veronal buffer when applied in the test system. The time of cell death in the TEA-buffered medium containing 5% serum was < 15 minutes for all the sera studied. The parameters denoting serum complement activity were as follows: a half-life time for the moving cells (TLD50), and a similar value for 100% cell inactivation (1/TLD50, functional activity of the complement system, ACS). The sensitivity of this assay was calculated from dependencies between TLD50 and ACS, and actual serum concentrations. We have suggested an opportunity for evaluation of an integral complement activity, and interrelations between the intensity of synthesis and consumption of its major effector proteins. In the course of this study, we have tested different concentrations of Ca++ and Mg++ ions in the incubation buffer, with optimal physiological concentrations of2.5 mMand1.5 mM, respectively. We have also estimated statistical precision characteristics for pre-analytical and analytical steps of the method. The average coefficients of variation (CV) were 3.9% and 2.7%, respectively, thus satisfying the reliability criteria in research. A short performance time of the study suggests its potential application in clinical practice, including online examination regimens. A method for semi-automatic measurement of serum complement activity could be applicable in daily clinical practice, including the online performance.

Mammalian Host-Versus-Phage immune response determines phage fate in vivo.

Emerging bacterial antibiotic resistance draws attention to bacteriophages as a therapeutic alternative to treat bacterial infection. Examples of phage that combat bacteria abound. However, despite careful testing of antibacterial activity in vitro, failures nevertheless commonly occur. We investigated immunological response of phage antibacterial potency in vivo. Anti-phage activity of phagocytes, antibodies, and serum complement were identified by direct testing and by high-resolution fluorescent microscopy. We accommodated the experimental data into a mathematical model. We propose a universal schema of innate and adaptive immunity impact on phage pharmacokinetics, based on the results of our numerical simulations. We found that the mammalian-host response to infecting bacteria causes the concomitant removal of phage from the system. We propose the notion that this effect as an indirect pathway of phage inhibition by bacteria with significant relevance for the clinical outcome of phage therapy.

Effect of dietary supplementation with zinc enriched yeast (Saccharomyces cerevisiae) on immunity of rainbow trout (Oncorhynchus mykiss).

Zinc (Zn) is an essential trace element in all living organisms, and the first eukaryotic Zn uptake transporter was discovered in the yeast, Saccharomyces cerevisiae. Zinc-enriched yeast is a currently available Zn supplement. The purpose of the investigation was to compare and evaluate the effect of Zn enriched yeast in rainbow trout. The fish (mean body weight 10 ± 0.5 g) were fed a commercial diet supplemented with 0 (control), 1 × 10(6), 1 × 10(7) and 1 × 10(8) CFU/g of Zn-enriched yeast for 60-days. Results showed that significant increase in serum lysozyme activity, complement activity and total immunoglobulin were seen in all treatment groups during feeding trial when compared to the control group. On the basis of our findings, Zn-enriched improved rainbow trout growth, some immune parameters and disease resistance.

THE DEVELOPMENT OF TOTAL COMPLEMENT ACTIVITY ASSAY BASED ON COMPLEMENT-DEPENDENT IMMUNE LIPOSOME LYSIS

Background: The purpose of work was development of a fast and reproduced procedure for measurement of the total complement activity (ТСА) in human or animal blood serum. Materials and methods: Steady at storage liposomes preparations, which surface sensitized 2,4-DNP haptens, and the internal volume contains calceine or sulforhodamine 101 are obtained. Complement-dependent immune lysis of liposomes at presence of the anti-2,4-DNP immunoglobulines and complement preparations from animals are investigated. Results: It is shown that the degree of liposomes immune lysis depends on complement concentration in a wide range that can be used for definition of TCA level. Research of blood sera from patients has revealed correlation (r =0,793) between data received with the help of liposome immunolytic systems, and the data of nephelometric analysis with application of suspension sheep erythrocytes. Conclusion: The method allows to define total complement activity in blood serum in 15 minutes without separation of reaction components. This might be useful for measurement ТСА level at patients with various diseases and realization of scientific researches.

Probiotic effects of Lactobacillus plantarum and L. delbrueckii ssp. bulguricus on some immune-related parameters in Barbus grypus

Two main probiotics (Lactobacillus plantarum and L. delbrueckii ssp. bulguricus) were isolated from the intestine of Barbus grypus and their characteristics were determined using biochemical, molecular and probiotical tests (bacterial antagonistic effects and lack of pathogenicity to fish). The effect that these lactic acid bacteria (LAB) had on the immune response of juveniles B. grypus and their resistance to Aeromonas hydrophila when fed as a dietary supplement was examined in the present study. The fish were randomly divided into four groups of 120 fish and were fed with diet containing 5 × 107 CFU g−1 of each isolated LAB, Lactobacillus casei PTCC 1608 or a control diet with no bacteria for 60 days, after which half of the fish from each group were challenged with A. hydrophila, while the remaining fish were fed with the control diets for a further 15 days. Various immune parameters were examined at 30 and 60 days post-feeding (dpf), and also 15 days after stopping feeding the probiotic. The results showed that dietary administration of L. plantarum significantly increased serum lysozyme, complement and respiratory burst activities in the serum of B. grypus by 30 dpf. The highest bactericidal activity was observed in the serum of fish fed the diet containing L. delbruecki ssp. bulguricus. Fish fed with diet containing L. delbruecki and L. plantarum had significantly higher survival rates than those fed the control diet after challenge with A. hydrophila. The results suggest that dietary supplementation with L. plantarum and L. delbrueck, isolated from B. grypus, can stimulate selected immune parameters in B. grypus infected with A. hydrophila and increase their survival against this bacterium. These appear to be potential probiotic species for use in aquaculture to improve the health status and disease resistance of juveniles’ B. grypus.