Generation of monoclonal antibodies and epitope mapping of ApxIVA of Actinobacillus pleuropneumoniae

A Combinatorial Vaccine Containing Inactivated Bacterin and Subunits Provides Protection Against Actinobacillus pleuropneumoniae Infection in Mice and Pigs

Actinobacillus pleuropneumoniae (APP) is the etiological agent of porcine contagious pleuropneumonia (PCP) that causes great economic losses in the swine industry. Currently, vaccination is still a commonly used strategy for the prevention of the disease. Commercially available vaccines of this disease, including inactivated bacterins and subunit vaccines, have clinical limitations such as side effects and low cross-protection. In this study, a combinatorial vaccine (Bac-sub) was developed, which contained inactivated bacterial cells of a serovar 1 strain and three recombinant protoxins (rApxIA, rApxIIA, and rApxIIIA). Its side effects, immune protection, and cross-protection were evaluated and compared with a commercial subunit vaccine and a commercial trivalent bacterin in a mouse infection model. The results revealed that the Bac-sub vaccine showed no obvious side effects, and induced higher levels of Apx toxin-specific IgG, IgG1, and IgG2a than the commercial vaccines after booster. After a challenge with virulent strains of serovars 1, 5, and 7, the Bac-sub vaccine provided greater protection (91.76%, 100%, and 100%, respectively) than commercial vaccines. Much lower lung bacterial loads (LBLs) and milder lung lesions were observed in the Bac-sub-vaccinated mice than in those vaccinated with the other two vaccines. The protective efficacy of the Bac-sub vaccine was further evaluated in pigs, which showed that vaccinated pigs displayed significantly milder clinical symptoms and lung lesions than the unvaccinated pigs after the challenge. Taken together, Bac-sub is a safe and effective vaccine that could provide high protection against A. pleuropneumoniae infection in both mice and pigs.

The tumor microenvironment: a pitch for multiple players

The cancer microenvironment may be conceptually regarded as a pitch where the main players are resident and non-resident cellular components, each covering a defined role and interconnected by a complex network of soluble mediators. The crosstalk between these cells and the tumor cells within this environment crucially determines the fate of tumor progression. Immune cells that infiltrate the tumor bed are transported there by blood circulation and exert a variety of effects, either counteracting or favoring tumor outgrowth. Here, we review and discuss the multiple populations composing the tumor bed, with special focus on immune cells subsets that positively or negatively dictate neoplastic progression. In this scenario, the contribution of cancer stem cells within the tumor microenvironment will also be discussed. Finally, we illustrate recent advances on new integrated approaches to investigate the tumor microenvironment in vitro.

Magnetic beads-based enzymatic spectrofluorometric assay for rapid and sensitive detection of antibody against ApxIVA of Actinobacillus pleuropneumoniae

In this paper, a simple, easily-operated and enzyme-amplified fluorescence immunoassay method using magnetic particles for the detection of antibody against Actinobacillus pleuropneumoniae (APP) has been presented. The A protein of APP Repeats-in-Toxin IV (ApxIVA) with high specificity to the APP species was immobilized onto the magnetic bead surfaces. Horseradish peroxidase (HRP), which can catalyze the substrate 4-hydroxyphenylacetic acid (p-HPA), generating fluorescent bi-p, p'-hydroxyphenylacetic acid (DBDA), was selected as an enzymatic-amplified tracer. The ApxIVA antibody was detected for the presence of APP infection by measuring the fluorescence intensity of DBDA. Under optimal conditions, the calibration plot obtained for standard positive serum was approximately linear within the dilution range 1:160-1:5120. The limit of detection (LOD) for the assay was 1:10240, considerably lower than that of ApxIVA-ELISA (1:320) (S/N=3). A series of repeatability measurements of using 1:320-fold diluted standard positive serum gave reproducible results with a relative standard deviation (RSD) of 4.8% (n=11). The ability of the immunosensor to analyze clinical samples was tested on porcine sera. The immunosensor yielded an efficiency of 89.7%, sensitivity of 90.9% and specificity of 89.3% compared with ApxIVA-ELISA.

Characterization of monoclonal antibodies against goat interleukin-18 and their application in the measurement of goat interleukin-18 in LPS-stimulated peripheral blood mononuclear cells by sandwich ELISA

In order to develop a specific assay for the measurement of goat IL-18 level, two stable hybridoma cell lines were established which secreted IgG1 monoclonal antibodies (mAbs) against goat IL-18. Specific binding of two mAbs named 2E8 and 4C4 to recombinant goat IL-18 expressed in Escherichia coli was demonstrated in an ELISA and Western blotting. Results also showed that mAbs 2E8 and 4C4 bound to distinct epitopes in the ELISA additivity test. These two mAbs were applied in IFA analysis for the detection of goat IL-18 expressed in 293FT cells and in the sandwich ELISA for the measurement of goat IL-18 levels in LPS-stimulated PBMC. Results from this study demonstrated that mAbs against goat IL-18 recognize bovine and human IL-18 and could be used to measure IL-18 levels in different inflammations or immune responses in future studies.

Immunogenicity of recombinant protective antigen and efficacy against intranasal challenge with Bordetella bronchiseptica

Bordetella bronchiseptica is a Gram-negative respiratory pathogen that causes substantial disease in a variety of animals. Filamentous hemagglutinin (FHA) and pertactin are important attachment factors and protective immunogens, which serve as protective antigens in several animal models of infection with B. bronchiseptica. Here, we showed the efficacy of subcutaneous immunization of mice with a recombinant protein rF1P2, which consisted of the important immunodominant protective type I domain (F1) of FHA and the highly immunogenic region II domain (P2) of pertactin. Groups of mice tested, when challenged with different strains of B. bronchiseptica were fully protected, with long-lasting immunity to lethal B.bronchiseptica challenge, whereas mice immunized with Freund's adjuvant alone or PBS were not. In rF1P2-immunized mice, specific antibodies lasted for more than 120 days, and the IgG1/IgG2a ratio remained at a constant level till the end of the study. This suggests that rF1P2-induced a long-lasting balanced humoral immune responses and immunological memory in mice. rF1P2-specific antisera inhibited hemagglutination associated with full-length mature FHA. Furthermore, passive antiserum transfer from immunized animals completely protected naive mice from subsequent B. bronchiseptica challenge. These data may have implications for the development of safe and efficacious subunit vaccines for the prevention of bordetellosis, and may contribute to future acellular whooping cough vaccines.

Subcutaneous vaccination with attenuated Salmonella enterica serovar Choleraesuis C500 expressing recombinant filamentous hemagglutinin and pertactin antigens protects mice against fatal infections with both S. enterica serovar Choleraesuis and Bordetella bronchiseptica

Salmonella enterica serovar Choleraesuis strain C500 is a live, attenuated vaccine that has been used in China for over 40 years to prevent piglet paratyphoid. We compared the protective efficacies of subcutaneous (s.c.) and oral vaccination of BALB/c mice with C500 expressing the recombinant filamentous hemagglutinin type I domain and pertactin region 2 domain antigen (rF1P2) of Bordetella bronchiseptica. Protective efficacy against both S. enterica serovar Choleraesuis infection in an oral fatal challenge model and B. bronchiseptica infection in a model of fatal acute pneumonia was evaluated. Both the s.c. and oral vaccines conferred complete protection against fatal infection with the virulent parent S. enterica serovar Choleraesuis strain (C78-1). All 20 mice vaccinated s.c. survived intranasal challenge with four times the 50% lethal dose of virulent B. bronchiseptica (HH0809) compared with 4 of 20 vector-treated controls and 1 of 18 phosphate-buffered saline-treated controls that survived, but no significant protection against HH0809 was observed in orally vaccinated animals. Both the s.c. and oral vaccines elicited rF1P2-specific serum immunoglobulin G (IgG) and IgA antibodies. However, lung homogenates from s.c. vaccinated animals had detectably high levels of rF1P2-specific IgG and IgA; a much lower level of rF1P2-specific IgG was detected in samples from orally vaccinated mice, and the latter showed no evidence of local IgA. Furthermore, a more abundant and longer persistence of vaccine organisms was observed in the lungs of mice immunized s.c. than in those of mice immunized orally. Our results suggest that s.c. rather than oral vaccination is more efficacious in protecting mice from fatal challenge with B. bronchiseptica.