Haemophilus parasuis serovar 5 Nagasaki strain adheres and invades PK-15 cells

Haemophilus parasuis is the agent responsible for causing Glässer's disease, which is characterized by fibrinous polyserositis, polyarthritis and meningitis in pigs. The purpose of this study was to investigate the in vitro ability of two H. parasuis serovars of different virulence (serovar 5, Nagasaki strain, highly virulent, belonging to serovar 5, and SW114 strain, nonvirulent, belonging to serovar 3) to adhere to and invade porcine kidney epithelial cells (PK-15 line). Nagasaki strain was able to attach at high levels from 60 to 180 min of incubation irrespective of the concentrations compared (10(7)-10(10)CFU), and a substantial increase of surface projections could be seen in PK-15 cells by scanning electron microscopy. This virulent strain was also able to invade effectively these epithelial cells, and the highest invasion capacity was reached at 180 min of infection. On the contrary, nonvirulent SW114 strain hardly adhered to PK-15 cells, and it did not invade these cells, thus suggesting that adherence and invasion of porcine kidney epithelial cells could be a virulence mechanism involved in the lesions caused by H. parasuis Nagasaki strain in this organ.

In house ELISA based on recombinant ORF2 protein underline high prevalence of IgG anti-hepatitis E virus amongst blood donors in south Brazil

Hepatitis E Virus (HEV) is a zoonotic pathogen responsible for causing acute hepatitis in human, especially in developing countries. Diagnosis of HEV usually relies on the detection of antibodies mostly by enzyme-linked immunosorbent assay (ELISA). In the present study, we designed a new indirect ELISA (iELISA) based on a short recombinant peptide derived from the capsid protein (ORF2p) and demonstrated its potential for detecting human IgG against HEV genotype 3. The best polystyrene plate (Maxisorp^®), optimal ORF2p coating antigen concentration (0,67μg/well) and primary antibody dilution (1:100) were determined. This iELISA showed a sensitivity of 91.4% and specificity of 95.9%. The comparison of our in house iELISA with a commercial assay (RecomWell, Mikrogen^®) showed 94.25% of agreement and a kappa index of 0.88. The ORF2 recombinant ELISA was used to screen 780 blood donors for anti-HEV IgG and we found that 314 (40,25%) of these donors were IgG positive. This high prevalence of antibodies suggests, for the first time, that the Southern Brazil region might be endemic to Hepatitis E Virus genotype 3.

Bovine leukemia virus DNA associated with breast cancer in women from South Brazil

Breast cancer is a neoplastic condition with a high morbidity and mortality amongst women worldwide. Recent data linking bovine leukemia virus (BLV) with breast cancer has been contested already. Our study investigated the presence of BLV genome in healthy (n = 72) and cancerous (n = 72) paraffin-embedded samples of breast tissues from women in south Brazil. BLV DNA was found most frequently (30.5%) in breast cancer tissue than in healthy breast (13.9%) (Odds ratio = 2.73; confidence interval = 1.18-6.29; p = 0.027). In contrast, antibodies to BLV were found in a very small percentage of healthy blood donors. There was no association between BLV DNA and other tumor prognostic biological markers such as hormonal receptors, HER2 oncoprotein, proliferation index, metastasis in sentinels lymph nodes, and tumor grade and size. Our findings suggest that BLV should be considered a potential predisposing factor to breast cancer in women.

Blood cellular immune response in pigs immunized and challenged with Haemophilus parasuis

The cellular immune response to an experimental infection by Haemophilus parasuis, the etiological agent of Glässer's disease in pigs, was characterized studying changes in peripheral blood mononuclear cells (PBMC) in colostrum-deprived pigs. Five groups were studied, four of those were previously immunized with different formulations and the fifth was maintained as non-immunized control. All groups were challenged with 5 x 10(9) CFU of H. parasuis serotype 5. The non-commercial bacterin conferred a complete protection, while the OMP-vaccine and the exposure to a subletal dose of 10(5) CFU of H. parasuis protected only partially, and the recombinant Tbp B-vaccine induced no protection. PBMC were analyzed using monoclonal antibodies against porcine CD45(+), CD3(+), CD4(+), CD8alpha(+), CD25(+), CD4(+) naïve, alphaIgM(+) and SWC3(+) cells in single-colour fluorescence, and CD4(+)/CD8alpha(+) and CD8alpha(+)/CD8beta(+) combinations in two-colour fluorescence. The different groups showed no significant changes in PBMC subsets following vaccination, and only minor changes were encountered after challenge, consisting mainly of significant increases (P<0.05) in the relative proportions of monocytes and granulocytes (SWC3(+)) and B cells (alphaIgM(+)), as well as a significant reduction in CD3(+) cells (P<0.05). These changes were similar for the five groups compared, except for the significant increase of CD25(+) cells, which was only observed for the bacterin-vaccinated group. These results suggest an increase of trafficking of inflammatory cells and the onset of the adaptive antibody response against H. parasuis infection; in addition, the blood cellular response developed by the different groups was not relevant to protection.

Molecular serotyping of clinical strains of Haemophilus (Glaesserella) parasuis brings new insights regarding Glässer's disease outbreaks in Brazil

Glässer’s disease (GD) is an important infectious disease of swine caused by Haemophilus (Glaesserella) parasuis. Vaccination with inactivated whole cell vaccines is the major approach for prevention of H. parasuis infection worldwide, but the immunity induced is predominantly against the specific polysaccharide capsule. As a consequence, the available vaccines may not induce adequate protection against the field strains, when the capsules present in the vaccine strains are different from those in strains isolated from the farms. Therefore, it is crucial to map H. parasuis serovars associated with regional outbreaks so that appropriate bacterin vaccines can be developed and distributed for prevention of infection. In this study, 459 H. parasuis field strains isolated from different Glässer’s disease outbreaks that occurred in 10 different Brazilian States were analyzed for serotype using PCR-based approaches. Surprisingly, non-typeable (NT) strains were the second most prevalent group of field strains and along with serovars 4, 5 and 1 comprised more than 70% of the isolates. A PCR-based approach designed to amplify the entire polysaccharide capsule locus revealed 9 different band patterns in the NT strains, and 75% of the NT strains belonged to three clusters, suggesting that a number of new serovars are responsible for a substantial proportion of disease. These results indicate that commercially available vaccines in Brazil do not cover the most prevalent H. parasuis serovars associated with GD.

New insights about functional and cross-reactive properties of antibodies generated against recombinant TbpBs of Haemophilus parasuis

Vaccines have become fundamental in the control and elimination of Glässer Disease, a systemic disease of pigs caused by Haemophilus parasuis. The classic vaccines available for prevention of this infection were developed without a robust knowledge about host immunological mechanisms. In this study, we demonstrated the presence of cross-reactive epitopes on both the N-lobe and C-lobe of variants of transferrin binding protein B (TbpBs) expressed on the surface of 6 virulent serovars of H. parasuis. Antibodies against TbpB-derived antigens were capable of increasing the phagocytic capacity of neutrophils and were also capable of blocking porcine transferrin from binding to TbpB. Surprisingly, none of the pig or mice antisera from animals immunized with TbpB-derived antigens mixed with Montanide IMS 2215 VG PR adjuvant were able to activate the classical complement pathway (CCP). In contrast, antisera from mice immunized with TbpB-derived antigens adjuvanted with Freund’s adjuvants or Montanide Gel 01 were able to activate the CCP and kill H. parasuis. Our results demonstrate that the type of adjuvant can modulate the functional response induced by TbpB-derived antigens. Based on these results, we propose that a properly formulated TbpB-based vaccine may elicit a functional protective antibody response with broad cross-reactivity against heterologous strains of H. parasuis.

Systemic antibody response in colostrum-deprived pigs experimentally infected with Haemophilus parasuis

The serum antibody response to an experimental infection by Haemophilus parasuis, the etiological agent of Glässer's disease in pigs, was characterized by ELISA measuring IgM and IgGt levels against whole-cells and outer-membrane-proteins (OMPs) as antigens. Five groups of pigs were studied, four of those were previously immunized with different formulations, and the fifth was maintained as non-immunized control. All groups were challenged with 5x10(9) CFU of H. parasuis. The non-commercial bacterin induced a full protection against disease, the OMP-vaccine and the exposure to a sublethal dose of 10(5) CFU protected only partially, and the recombinant TbpB-vaccine conferred no protection. The humoral response in the pigs that died after infection (all controls, all those vaccinated with the recombinant TbpB, and two of both those inoculated with OMPs and those exposed to the sublethal dose) could be only measured before it, but it was irrelevant in all cases. However, a specific IgM and IgGt production was observed before challenge in all the surviving pigs, irrespective of the type of immunization received. This antibody response was even greater after H. parasuis infection, especially in those survivors receiving the sublethal dose. These results suggest a role of the antibodies developed after the different immunization protocols in preventing infection and death; therefore, the humoral immunity is protective against experimental Glässer's disease.

Immunomodulatory effects of dietary β-glucan in silver catfish (Rhamdia quelen)

ABSTRACT: The immunomodulatory effects of dietary β-glucan were evaluated in silver catfish. β-glucan was added to the diet (0.01%, and 0.1%) and fed to the fish for 21 days, to evaluate effects on blood and some innate immune parameter, or fed for 42 days, to evaluate growth rate and resistance to challenge with pathogenic Aeromonas hydrophila. We found that adding β-glucan to the diet had no effect on fish growth and no effect on blood cells, or serum bacterial agglutination and serum myeloperoxidase activity. However, fish that received β-glucan in the diet had the natural hemolytic activity of complement significantly higher compared to control fish. Furthermore, fish fed with β-glucan and challenged with A. hydrophila had fewer bacteria in blood and presented a significantly higher survival rate compared to control fish. Thus, we concluded that β-glucan might be explored as feed additive aiming to improve silver catfish innate immunity and resistance to specific pathogen.

New insights in cellular immune response in colostrum-deprived pigs after immunization with subunit and commercial vaccines against Glässer's disease

Four groups of colostrum-deprived pigs were immunized with Porcilis Glässer® (PG) or with subunit vaccines developed by us (rTbpA, NPAPT(M) or NPAPT(Cp)) against Glässer's disease, and they were challenged with 3×10(8)CFU of Haemophilus parasuis. A strong reduction in CD3(+)γδTCR(+) cells was seen in non-immunized control and scarcely protected (rTbpA) groups, suggesting that these cells could represent a target of H. parasuis infection. A significant increase in CD172α(+)CD163(+) cells was detected in all groups but PG, while a reduction in SLAIIDR(+) molecules expression was observed after challenge in control animals. Significant increases in CD3ε(+)CD8α(+)CD8β(+) and B cells were detected respectively in control and NPAPT groups, and in scarcely (rTbpA) and well-protected (NPAPT(M) and NPAPT(Cp)) groups. Finally, a greater response in CD4(+)CD8α(-) cells was observed in NPAPT(Cp) compared to NPAPT(M) and PG groups. These results state the potential of NPAPT antigen for developing effective vaccines against Glässer's disease.

Cytokine expression in colostrum-deprived pigs immunized and challenged with Haemophilus parasuis

The expression of several cytokines in spleen, pharyngeal lymph nodes, lung and brain after different immunization procedures and a challenge with 5 x 10(9) CFU of Haemophilus parasuis was compared. Five groups of colostrum-deprived pigs were used: vaccinated with (I) a bacterin, (II) an outer-membrane-protein-vaccine, (III) a recombinant transferring-binding protein B, (IV) exposed to a total dose of 10(5) CFU, and (V) not previously immunized. All pigs in groups III and V died, while all animals in group I, most of group IV and half of group II survived until the end of the experiment. IL-1alpha was found in significantly higher levels (p<0.05) in spleen, lymph nodes and brain of dead pigs, which could be explained by the major severity of lesions in these animals. However, IL-4, IL-10, TNF-alpha and IFN-gamma were expressed in significantly higher levels by survivors (for all the four cytokines in lymph nodes; for IL-4, IL-10 and TNF-alpha in spleen; for IL-4, TNF-alpha and IFN-gamma in lung, and only for TNF-alpha in brain), thus suggesting a role of these four cytokines in the adaptive response, which might contribute to protection against H. parasuis infection.

The amino acid selected for generating mutant TbpB antigens defective in binding transferrin can compromise the in vivo protective capacity

Haemophilus parasuis is the causative agent of the Glässer's disease (GD), one of the most important bacterial diseases that affect young pigs worldwide. GD prevention based on vaccination is a major concern due to the limited cross-protection conferred by the inactivated whole cell vaccines used currently. In this study, vaccines based on two mutant recombinant proteins derived from transferrin binding protein B of H. parasuis (Y167A-TbpB and W176A-TbpB) were formulated and evaluated in terms of protection against lethal challenge using a serovar 7 (SV7) H. parasuis in a high susceptibility pig model. Our results showed that H. parasuis strain 174 (SV7) is highly virulent in conventional and colostrum-deprived pigs. The Y167A-TbpB and W176A-TbpB antigens were immunogenic in pigs, however, differences in terms of antigenicity and functional immune response were observed. In regard to protection, animals immunized with Y167A-TbpB antigen displayed 80% survival whereas the W176A-TbpB protein was not protective. In conjunction with previous studies, our results demonstrate, (a) the importance of testing engineered antigens in an in vivo pig challenge model, and, (b) that the Y167A-TbpB antigen is a promising antigen for developing a broad-spectrum vaccine against H. parasuis infection.

Differences in Haemophilus parasuis adherence to and invasion of AOC-45 porcine aorta endothelial cells

Background

The pathogenesis of Haemophilus parasuis depends on the bacterium’s ability to interact with endothelial cells and invade adjacent tissues. In this study, we investigated the abilities of eight H. parasuis reference strains belonging to serovars 1, 2, 4, 5, 7, 9, 10 and 13 to adhere to and invade porcine aortic endothelial cells (AOC-45 cell line).

Results

The strains belonging to serovars 1, 2 and 5 were able to attach at high rates between 60 and 240 min of incubation, and serovars 4, 7 and 13 had moderate attachment rates; however, the strains belonging to serovars 9 and 10 had low adherence at all time points. Strong adherence was observed by scanning electron microscopy for the strains of serovars 5 and 4, which had high and moderate numbers, respectively, of H. parasuis cells attached to AOC-45 cells after 240 min of incubation. The highest invasiveness was reached at 180 min by the serovar 4 strain, followed by the serovar 5 strain at 240 min. The invasion results differed substantially depending on the strain.

Conclusion

The reference strains of H. parasuis serovars 1, 2, 4 and 5 exhibited high adhesion and invasion levels to AOC-45 porcine aorta endothelial cells, and these findings could aid to better explain the pathogenesis of the disease caused by these serovars.

New Pathological Lesions Developed in Pigs by a "Non-virulent" Strain of Glaesserella parasuis

Glaesserella parasuis is a Gram-negative bacterium that causes Glässer's disease, a common pathology found in young pigs characterized by polyarthritis, polyserositis, and meningitis. The bacterium has 15 known serovars that have been classified by virulence. Serovars 1, 4, 5, and 12 are considered highly virulent and used in most studies. Serovars 3, 6, 7, 9, and 11 are considered avirulent. Recent reports that serovar 7 is an emerging problem in the pig industry indicate that the association of virulence and serovar may not always be reliable. This led us to infect colostrum-deprived piglets with the reference serovar 7 strain (SV7 strain 174) that had been passaged through pigs and characterize the clinical and pathological signs. We observed that SV7 strain 174 caused clinical signs consistent with Glässer's disease in all infected piglets that succumbed to infection for up to day 5 post-infection. Macroscopic and microscopic lesions were consistent with those found in piglets infected with conventional virulent serovars. In addition, we describe novel microscopic lesions associated with Glässer's disease such as endophthalmitis and thymic depletion. Thus, our findings indicate that SV7 strain 174 causes classical signs of Glässer's disease in colostrum-deprived piglets and some caution should be used in employing vaccine strategies based on association between capsular serovar and virulence.

A vaccine based on a mutant transferrin binding protein B of Haemophilus parasuis induces a strong T-helper 2 response and bacterial clearance after experimental infection

This study aimed to characterize the type of immune response induced by an experimental vaccine based on a mutant Haemophilus parasuis transferrin binding protein (Tbp) B (Y167A) defective in its ability to bind porcine transferrin. Clinical and pathological signs, bacterial clearance, antibody response and the cytokine profile in alveolar macrophages and spleen after the vaccination and challenge of twenty-two colostrum-deprived pigs with 10(8) CFU of H. parasuis were analysed. Pigs vaccinated with Y167A were compared to those vaccinated with native TbpB (nTbpB), those treated with a commercial bacterin (CB) against Glässer's disease, those unvaccinated challenged (CH) and those unvaccinated unchallenged (UNCH) pigs. The rectal temperatures of Y167A pigs resembled those of UNCH pigs and were significantly lower than those of the nTbpB, CB and CH animals. A major reduction in pathological changes of the challenged pigs was observed in the Y167A group. H. parasuis was cleared from 88.9% of the samples from Y167A pigs versus 60.0% and 55.6% from those of the CB and nTbpB groups, respectively. The antibody response elicited by Y167A by ELISA was notably higher than that observed for nTbpB and CB pigs and was capable of preventing the expression and secretion of IL-8. The expression of IL-4 and IL-5, which were associated with the specific antibody levels, suggests that the main mechanism of protection conferred by Y167A vaccine is based on a strong T-helper 2 response.

Characterization of an IgM-like immunoglobulin from silver catfish (Rhamdia quelen) serum and its use for the production of polyclonal antibodies and development of immunoassays

Abstract: Knowledge on fish immunoglobulin (Ig) characteristics and the availability of monoclonal or polyclonal antibodies to fish Igs are essential to evaluate the humoral immune response and the Ig distribution on leukocyte cells. We demonstrated that silver catfish serum Ig is composed of one immunodominant H chain with approximately 75k Da and one L chain with approximately 28 kDa, similar to human IgM. Rabbit polyclonal antibodies to the catfish IgM-like Ig recognized both the H and L chain and were useful in developing an indirect ELISA to measure the production of antibodies in fish immunized with bovine serum albumin. Dot blot and western blot cross-reactivity studies indicated a wide degree of epitope sharing amongst Ig from several Siluriformes and Characiformes fish indigenous to Brazilian rivers. In these fish species, polyclonal antibodies reacted mostly with the H chain. The results presented here are central to the development of tools and strategies to investigate the antibody production to inoculated antigens and tissue distribution of Ig molecules in native fish species. Furthermore, because of the wide range of cross-reactivity, polyclonal antibodies to silver catfish IgM-like Ig might be used to develop immunoassays to measure the humoral immune response in other fish species.

Development of an indirect ELISA based on recombinant capsid protein to detect antibodies to bovine leukemia virus

Serological testing and culling infected animals are key management practices aiming eradication of bovine leukemia virus infection. Here, we report the development of an indirect ELISA based on BLV recombinant capsid protein (BLVp24r) to detect anti-BLV antibodies in cattle serum. The BLVp24r was expressed in Escherichia coli and purified by affinity chromatography, and then used to set up the ELISA parameters. The Polysorp® plate coated with 50ng of antigen/well and bovine serum diluted 1:100 gave the best results during standardization. Using sera from infected and non-infected cattle we set up the cutoff point at 0.320 (OD450nm) with a sensitivity of 98.5% and specificity of 100.0%. Then, we tested 1.187 serum samples from dairy (736 samples) and beef cattle (451 samples) with unknown status to BLV. We found that 31.1% (229/736) and 9.5% (43/451) of samples amongst dairy and beef cattle, respectively, had IgGs to BLV. The rate of agreement with a commercial competitive ELISA was 84.3% with a κ value of 0.68. Thus, our BLVp24r iELISA is suitable to detect BLV infected animals and should be a useful tool to control BLV infection in cattle.

Backyard pigs are a reservoir of zoonotic hepatitis E virus in southern Brazil

Background

Hepatitis E virus (HEV) is the causative agent of acute hepatitis worldwide. There is no seroprevalence study in backyard farms, which are characterized by suboptimal hygienic conditions in Brazil. We aimed to determine the seroprevalence and genetic diversity of HEV in backyard pigs in Brazil.

Methods

Swine serum samples collected in 2012 (n=731) and 2014 (n=713) were analysed. The presence of anti-HEV immunoglobulin G in pig serum was evaluated by indirect enzyme-linked immunosorbent assay. Reverse transcription polymerase chain reaction was performed and phylogenetic analyses were carried out based on the partial ORF1 and ORF2 coding regions.

Results

Anti-HEV antibodies were detected in 77.6% (567/731; 95% confidence interval [CI] 74.5 to 90.6%) of serum samples in 2012 and 65.5% (467/713; 95% CI 62.0 to 69.0%) in 2014. The herd seroprevalence was 91.7% (187/204; 95% CI 91% to 99%) in 2012 and 83.7% (164/196; 95% CI 78% to 89%) in 2014. Further, HEV RNA was detected in 0.8% (6/713) of samples from 2014. Phylogenetic analysis showed three different genotype 3 subtypes with high similarity to human HEV strains.

Conclusions

This study showed that backyard pigs are a reservoir of HEV and alerts us to the need to control infection and spillover from backyard farms.

GenBank accession numbers

MF438128-MF438135.

Production and characterization of a Brazilian candidate antigen for Hepatitis E Virus genotype 3 diagnosis

Hepatitis E, caused by hepatitis E virus (HEV), is a viral infectious pathology of great importance in the public health. Hepatitis E outbreaks were registered in developing countries with poor or no sanitation, where drinking water was contaminated with fecal material, but also in many industrialized countries probably due to consumption of HEV-positive swine meat. In this study, we present the development and characterization of a recombinant antigen from ORF2 HEV genotype 3. Viral RNA was extracted from swine feces infected with the native virus. A total of 267 residues from the C-terminal ORF2((394-661)) coding sequence were cloned into the pET20a vector and expressed in Escherichia coli ER2566. Recombinant protein was purified by liquid chromatography and the fragment obtained a 98% homology against other human or swine HEV genotype 3 ORF2 sequences. Wistar rats were inoculated with ORF2p, developing antibodies able to recognize both the homologous antigen and the native HEV genotype 3 ORF2 present in infected stool. In parallel, HEV-negative swine were experimentally challenged with HEV genotype 3. ORF2 was detected by PCR 14 days post-inoculation in three-fourth piglets' feces and one week later by dot blot. In conclusion, this study proved the immunogenic and antigenic properties of the recombinant protein ORF2p.

β-Glucan improves wound healing in silver catfish (Rhamdia quelen)

The immune modulating activity of β-glucan on aquatic species has been a matter of intense investigation. Here, we aimed to investigate the effect of β-glucan on wound healing of silver catfish, a Neotropical South American scale-free fish. Small sections of skin and muscle (3 mm in diameter) were removed and fish were bathed daily with β-glucan (0.1% and 0.5%) up to 28 days when cicatrization was complete. A group of fish similarly injured and non-exposed to β-glucan was used as control. Wound closure and healing was monitored visually and by histopathological analysis. In fish bathed with 0.5% β-glucan we found reduced blood cortisol levels at day one post-wounding and, by day 7 post wounding, the deposition of granulation tissue was higher compared to non-exposed fish. In addition, from day 7 forward, wound size was significantly lower in fish bathed with 0.5% β-glucan. Histopathological analysis of the wounded site indicated a thin layer of immature epidermal cells at day one post wounding. A discrete inflammation with mixed inflammatory cell infiltrate was observed on wounded muscle and was lower by day 7 post wounding on fish bathed with 0.5% β-glucan. By day 14 post wounding, the deposition of collagen fibers and the presence of fibroblast and new muscle fibers were higher in fish exposed to 0.5% β-glucan, and dermis restoration was complete. Thus, our results indicate that in silver catfish wound healing occurs rapidly and improves greatly by daily bathing with β-glucan.

Reduced expression of selective immune-related genes in silver catfish (Rhamdia quelen) monocytes exposed to atrazine

The effect of atrazine (ATZ) and its metabolites on aquatic vertebrate species has been a matter of concern to researchers and environmentalist. In this study we exposed head kidney monocytes to sublethal concentrations of atrazine (1 and 10 μg/ml^-1), corresponding to 1% and 10% of the LC_50-96h, to evaluate the expression of immune-related genes central to immune stimulation. The mRNA levels of TNF-α, Mieloperoxidase and Mx genes were significantly reduced following 24 h exposure to both concentrations of ATZ. The mRNA levels of iRAK4 were reduced only at the higher ATZ concentration and the mRNA levels of IL-1β were not affected. The results reported here support our previous findings on the immunosuppressive effect of ATZ indicating its potential to interfere with the expression of immune-related genes, and strengthen the need to regulate ATZ usage aiming to preserve animal and human health.

Antibody response in silver catfish (Rhamdia quelen) immunized with a model antigen associated with different adjuvants

Adjuvants are essential to boost the immune response to inoculated antigen and play a central role in vaccine development. In this study, we investigated the efficacy of several adjuvants in the production of anti-bovine serum albumin (BSA) antibodies in silver catfish. Two hundred and seventy juvenile silver catfish (60–80 g) of both sexes were intraperitoneally vaccinated with BSA (200 µg/fish) alone or mixed to the following adjuvants: Freund’s complete adjuvant (FCA), Freund’s incomplete adjuvant (FIA), aluminum hydroxide (AlOH), Montanide, four types of cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs) and three concentrations of β-glucan, and the immune enhancing property was evaluated by measuring anti-BSA antibodies in blood samples at biweekly intervals. Our results demonstrated that CpGs ODNs and β-glucan were as effective as classical adjuvants (FCA, FIA, AlOH and Montanide) in promoting anti-BSA antibodies and that the kinetics of antibody production induced by all adjuvants used in our study had a similar trend to that observed in other fish species, with a peak at 28 days post-vaccination. These results may be useful for the selection of adjuvants for vaccine formulation intended for silver catfish and for the development of vaccine and vaccination strategies to other fish species.