Recombinant Lactococcus Lactis Displaying Omp31 Antigen of Brucella melitensis Can Induce an Immunogenic Response in BALB/c Mice

A subunit vaccine based on Brucella rBP26 induces Th1 immune responses and M1 macrophage activation

Brucellosis is a global zoonotic infection caused by Brucella bacteria, which poses a significant burden on society. While transmission prevention is currently the most effective method, the absence of a licenced vaccine for humans necessitates the urgent development of a safe and effective vaccine. Recombinant protein-based subunit vaccines are considered promising options, and in this study, the Brucella BP26 protein is expressed using prokaryotic expression systems. The immune responses are evaluated using the well-established adjuvant CpG-ODN. The results demonstrate that rBP26 supplemented with a CpG adjuvant induces M1 macrophage polarization and stimulates cellular immune responses mediated by Th1 cells and CD8 + T cells. Additionally, it generates high levels of rBP26-specific antibodies in immunized mice. Furthermore, rBP26 immunization activates, proliferates, and produces cytokines in T lymphocytes while also maintaining immune memory for an extended period of time. These findings shed light on the potential biological function of rBP26, which is crucial for understanding brucellosis pathogenesis. Moreover, rBP26 holds promise as an effective subunit vaccine candidate for use in endemic areas.

Mucosal Administration of Lactobacillus casei Surface-Displayed HA1 Induces Protective Immune Responses against Avian Influenza A Virus in Mice

Avian influenza is a serious threat to both public health and the poultry industry worldwide. This respiratory virus can be combated by eliciting robust immune responses at the site of infection through mucosal immunization. Recombinant probiotics, specifically lactic acid bacteria, are safe and effective carriers for mucosal vaccines. In this study, we engineered recombinant fusion protein by fusing the hemagglutinin 1 (HA1) subunit of the A/Aquatic bird/Korea/W81/2005 (H5N2) with the Bacillus subtilis poly γ-glutamic acid synthetase A (pgsA) at the surface of Lactobacillus casei (pgsA-HA1/L. casei). Using subcellular fractionation and flow cytometry we confirmed the surface localization of this fusion protein. Mucosal administration of pgsA-HA1/L. casei in mice resulted in significant levels of HA1-specific serum IgG, mucosal IgA and neutralizing antibodies against the H5N2 virus. Additionally, pgsA-HA1/L. casei-induced systemic and local cell-mediated immune responses specific to HA1, as evidenced by an increased number of IFN-γ and IL-4 secreting cells in the spleens and higher levels of IL-4 in the local lymphocyte supernatants. Finally, mice inoculated with pgsA-HA1/L. casei were protected against a 10LD50 dose of the homologous mouse-adapted H5N2 virus. These results suggest that mucosal immunization with L. casei displaying HA1 on its surface could be a potential strategy for developing a mucosal vaccine against other H5 subtype viruses.

A multi-epitope subunit vaccine based on CU/ZN-SOD, OMP31 and BP26 against Brucella melitensis infection in BALB/C mice

Brucellosis, a zoonosis caused by Brucella, is highly detrimental to both humans and animals. Most existing vaccines are live attenuated vaccines with safety flaws for people and animals. Therefore, it is advantageous to design a multi-epitope subunit vaccine (MEV) to prevent Brucella infection. To this end, we applied a reverse vaccinology approach. Six cytotoxic T cell (CTL) epitopes, seven T helper cell (HTL) epitopes, and four linear B cell epitopes from CU/ZN-SOD, Omp31, and BP26 were obtained. We linked the CTL, HTL, B-cell epitopes, the appropriate CTB molecular adjuvant, and the universal T helper lymphocyte epitope, PADRE, with linkers AAY, GPPGG, and KK, respectively. This yielded a 412-amino acid MEV construct, which we named MEVcob. The immunogenicity, stability, safety, and feasibility of the construct were evaluated by bioinformatics tools (including the AlphaFold2 prediction tool, the AlphaFold2 tool, NetMHC-I pan 4.0 server, IEDB MHC-I server, ABCpred service, and C-ImmSim server); the physicochemical properties, secondary and tertiary structures, and binding ability of MEVocb to toll-like receptor 4 (TLR4) was analyzed. Then, codon adaptation and computer cloning studies were performed. MEVocb is highly immunogenic in immunostimulation experiments, The proteins translated by these sequences were relatively stable, exhibiting a high antigenic index. Furthermore, mouse experiments confirmed that the MEVocb construct could raise IFN-γ, IgG, IgG2a, IgG1, IL-2, TNF-α levels in mice, indicating that induced a specific humoral and cellular immune response in BALB/c mice. This vaccine induced a statistically significant level of protection in BALB/c mice when challenged with Brucella melitensis 043 in Xinjiang. Briefly, we utilized immunoinformatic tools to design a novel multi-epitope subunit candidate vaccine against Brucella. This vaccine aims to induce host immune responses and confer specific protective effects. The study results offer a theoretical foundation for the development of a novel Brucella subunit vaccine.

Design of an oral vaccine using Lactococcus lactis against brucellosis: an in vitro and in vivo study

Brucellosis is regarded as one of the world's most severe zoonotic diseases. This study aimed to investigate the possibility of using recombinant Lactococcus lactis (L. lactis) as a live vector to produce recombinant Brucella abortus (B. abortus) Omp10. The gene sequences were obtained from GenBank. The proteins' immunogenicity was assessed using Vaxijen. After confirming the cloning of the Omp10 gene in the pNZ8148 vector by enzymatic digestion and PCR, transformation into L. lactis was done. SDS-PAGE and western blot methods evaluated omp10 protein expression. Mice received oral recombinant L. lactis vaccines. IgG antibodies against Omp10 were tested using ELISA. Real-time PCR and ELISA were used to analyze cytokine responses. Survival rate and histopathological changes were evaluated after the challenge. Omp10 was chosen for its 1.5524 antigenicity score. Enzymatic digestion and PCR identified a 381-bp gene fragment. A 10 kDa band indicated the success of L. lactis transformation. Mice administered the L. lactis-pNZ8148-Omp10-Usp45 vaccination 14 days after priming showed significantly higher Omp10-specific total IgG and IgG1 (P < 0.001) than the PBS control group. The mice who received the L. lactis-pNZ8148-Omp10-Usp45 and IRBA vaccines had significantly elevated levels of IFN-γ, TNFα, IL-4, and IL-10 in samples collected on days 14 and 28 (P < 0.001). Inflammatory response, morphological damage, alveolar edema, and lymphocyte infiltration were reduced in the target group. A recombinant L. lactis expressing the Omp10 protein was constructed as an oral Lactococcus-based vaccine and compared to live attenuated vaccines for future brucellosis investigations.

Immunization of BALB/c mice with BAB1-0278: An initial investigation of a novel potential vaccine for brucellosis based on Lactococcus Lactis vector

The gram-negative intracellular bacterium Brucella abortus causes bovine brucellosis, a zoonotic disease that costs a lot of money. This work developed a vector vaccine against brucellosis utilizing recombinant L. lactis expressing Brucella outer membrane protein BAB1-0278. Gene sequences were obtained from GenBank. The proteins' immunogenicity was tested with Vaxijen. The target vector was converted into L. lactis after enzymatic digestion and PCR validated the BAB1-0278 gene cloning in the pNZ8148 vector. The target protein was extracted using a Ni-NTA column and confirmed using SDS-PAGE and western blot. After vaccination with the target vaccine, the expression of IgG subclasses was evaluated by the ELISA method. Cytokine production was also measured by the qPCR method in the small intestine and spleen. Lymphocyte proliferation and innate immune response (NLR, CRP, and PLR) were also assessed. Finally, after the challenge test, the spleen tissue was examined by H&E staining. BAB1-0278 was chosen because of its antigenicity score of 0.5614. A 237-bp gene fragment was discovered using enzymatic digestion and PCR. The presence of a 13 kDa protein band was confirmed by SDS-PAGE and western blot. In comparison to the PBS group, mice given the L. lactis-pNZ8148-BAB1-0278-Usp45 vaccine 14 days after priming had substantially greater levels of total IgG, IgG1, and IgG2a (P < 0.001). Also, the production of cytokines (IFN-γ, TNFα, IL-4, and IL-10) indicating cellular immunity increased compared to the control group (P < 0.001). The target group had a lower inflammatory response, morphological impairment, alveolar edema, and lymphocyte infiltration. An efficient probiotic-based oral brucellosis vaccination was created. These studies have proven that the recommended immunization gives the best protection, which supports its promotion.

[Construction, Identification, and Expression of Lactococcus lactis-Based Recombinant Vaccine for Echinococcus granulosus]

Objective

To construct Lactococcus lactis (LL)-based recombinant LL-Eg95 (rLL-Eg95) vaccine for Echinococcus granulosus (Eg) and to examine its expression efficiency.

Methods

Eg95 gene was obtained by PCR from the template of pCD-Eg95. Then, pMG36e was inserted in the Eg95 gene after double cleaving with restriction endonucleases XbaⅠ and HindⅢ to construct recombinant plasmid pMG36e-Eg95, which was transformed into E.coli BL2 (DE3) competent cells. The recombinant plasmid was extracted and identified by double restriction endonuclease digestion and was then electroporated into LL MG1363 to construct rLL-Eg95 vaccine. Then, the plamid was extracted and identified by PCR.

Results

Examination of the recombinant plasmid by double restriction endonuclease digestion showed that the segment was of the expected length. PCR showed that 471 base pairs of Eg95 gene were amplified when the plasmid extracted from roxithromycin-resistant recombinant LL was used as the template. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the relative molecular mass of the Eg95 protein expressed was approximately 16.5×103 and that the amount of the expressed protein was 17% of the total bacterial proteins. Western blot findings suggested that the expressed protein could be recognized by mice serum infected with hydatid cyst.

Conclusion

The rLL-Eg95 vaccine was successfully constructed, expressing Eg95 protein that has specific antigenicity.

Study on antigenic protein Omp2b in combination with Omp31 and BP26 for serological detection of human brucellosis

BACKGROUND

Brucellosis is a very common zoonosis in certain localized areas worldwide, with a high prevalence in most developing countries. The detection of brucellosis still faces many challenges such as the need for more sensitive and specific diagnostic antigens.

METHODS

To evaluate the efficacy of Brucella outer membrane proteins (Omps) Omp2b in combination with omp31 and BP26 as diagnostic antigens for the serological detection of human brucellosis, these proteins were prepared by a prokaryotic expression system. Human brucellosis-positive and-negative sera were collected, and the detection effects of the diagnostic antigens were evaluated using an established indirect ELISA (iELISA) method. Receiver operating characteristic (ROC) curves and the area under the ROC curve (AUC), true positives, true negatives, false positives, false negatives, accuracy, positive predictive value, negative predictive value, analytical specificity, and sensitivity were obtained to evaluate the effectiveness of Omp2b and antigen combinations.

RESULTS

The iELISA results showed that the AUC of the antigenic proteins was 0.9100, 0.9387, 0.9343, and 0.9448, respectively, and that the combination of Omp31 and BP26 improved the accuracy and was superior to that of Omp2b alone. Analysis at the determined cut-off values showed that the analytical sensitivity of the assay was 0.8739 (95% CI:0.7974-0.9293) and the analytical specificity was 0.8539 (95% CI:0.7632-0.9199) when using Omp2b alone and 0.8649 when using the combination of Omp2b + BP26 (95% CI:0.7869-0.9223) with an analytical specificity of 0.9213 (95% CI:0.8446-0.9678) and 0.8468 (95% CI:0.7662-0.9082) and an analytical sensitivity of 0.9101 (95% CI:0.8305-0.9604). When Omp2b + Omp31 + BP26 was combined, the analytical sensitivity and specificity were 0.8559 (95% CI:0.7765-0.9153) and 0.9326 (95% CI:0.8590-0.9749), respectively. Protein antigens, including antigen combinations, did not cross-react with Yersinia enterocolitica O9 and E. coli O157: H7, indicating that their specificity was better than that of lipopolysaccharide (LPS).

CONCLUSIONS

Compared with individual Omp2b, antigen combinations improved the effectiveness in detecting brucellosis, but were still not as effective as LPS antigen. Omp2b, combined with Omp31 and BP26 as diagnostic antigens, can be used to detect human brucellosis.

Immunomodulatory action of Lactococcuslactis

Fermented foods are gaining popularity due to health-promoting properties with high levels of nutrients, phytochemicals, bioactive compounds, and probiotic microorganisms. Due to its unique fermentation process, Lactococcus lactis plays a key role in the food business, notably in the manufacturing of dairy products. The superior biological activities of L. lactis in these functional foods include anti-inflammatory and immunomodulatory capabilities. L. lactis boosted growth performance, controlled amino acid profiles, intestinal immunology, and microbiota. Besides that, the administration of L. lactis increased the rate of infection clearance. Innate and acquired immune responses would be upregulated in both local and systemic compartments, resulting in these consequences. L. lactis is often employed in the food sector and is currently being exploited as a delivery vehicle for biological research. These bacteria are being eyed as potential candidates for biotechnological applications. With this in mind, we reviewed the immunomodulatory effects of different L. lactis strains.

Recombinant vaccines in 2022: a perspective from the cell factory

The last big outbreaks of Ebola fever in Africa, the thousands of avian influenza outbreaks across Europe, Asia, North America and Africa, the emergence of monkeypox virus in Europe and specially the COVID-19 pandemics have globally stressed the need for efficient, cost-effective vaccines against infectious diseases. Ideally, they should be based on transversal technologies of wide applicability. In this context, and pushed by the above-mentioned epidemiological needs, new and highly sophisticated DNA-or RNA-based vaccination strategies have been recently developed and applied at large-scale. Being very promising and effective, they still need to be assessed regarding the level of conferred long-term protection. Despite these fast-developing approaches, subunit vaccines, based on recombinant proteins obtained by conventional genetic engineering, still show a wide spectrum of interesting potentialities and an important margin for further development. In the 80’s, the first vaccination attempts with recombinant vaccines consisted in single structural proteins from viral pathogens, administered as soluble plain versions. In contrast, more complex formulations of recombinant antigens with particular geometries are progressively generated and explored in an attempt to mimic the multifaceted set of stimuli offered to the immune system by replicating pathogens. The diversity of recombinant antimicrobial vaccines and vaccine prototypes is revised here considering the cell factory types, through relevant examples of prototypes under development as well as already approved products.

Immunological Effects of Recombinant Lactobacillus casei Expressing IHNV G Protein and Rainbow Trout (Oncorhynchus mykiss) Chemokine CK6 as an Oral Vaccine

IHNV is a virus that infects salmonids and causes serious economic damage to the salmonid farming industry. There is no specific treatment for the disease caused by this pathogen and the main preventive measure is vaccination, but this is only possible for small groups of individuals. Therefore, it is important to investigate new oral vaccines to prevent IHNV. In this study, the CK6 chemokine protein of rainbow trout and the truncated G protein of IHNV were used to construct a secretory expression recombinant L.casei vaccine for rainbow trout. The results showed that the levels of IgM and IgT antibodies in rainbow trout reached the highest level on the 15th day after the secondary immunization, and the antibodies exhibited high inhibitory activity against viral infection. Furthermore, the expression of relevant cytokines in different tissues was detected and found to be significantly higher in the oral vaccine group than in the control group. It was also found that pPG-612-CK6-G/L.casei 393 could stimulate splenic lymphocyte proliferation and improve mucosal immunity with significant differences between the immunized and control groups. When infected with IHNV, the protection rate of pPG-612-CK6-G/L.casei 393 was 66.67% higher than that of the control group. We found that pPG-612-CK6-G/L.casei 393 expressed and secreted the rainbow trout chemokine CK6 protein and IHNV truncated G protein, retaining the original immunogenicity of rainbow trout while enhancing their survival rate. This indicates that recombinant L.casei provides a theoretical basis and rationale for the development of an oral vaccine against IHNV and has important practical implications for the protection of rainbow trout from IHNV infection.

Immunization with a combination of recombinant Brucella abortus proteins induces T helper immune response and confers protection against wild-type challenge in BALB/c mice

Protective efficiency of a combination of four recombinant Brucella abortus (B. abortus) proteins, namely, ribosomal protein L7/L12, outer membrane protein (OMP) 22, OMP25 and OMP31, was evaluated as a combined subunit vaccine (CSV) against B. abortus infection in RAW 264.7 cell line and murine model. Four proteins were cloned, expressed and purified, and their immunocompetence was analysed. BALB/c mice were immunized subcutaneously with single subunit vaccines (SSVs) or CSV. Cellular and humoral immune responses were determined by ELISA. Results of immunoreactivity showed that these four recombinant proteins reacted with Brucella‐positive serum individually but not with Brucella‐negative serum. A massive production of IFN‐γ and IL‐2 but low degree of IL‐10 was observed in mice immunized with SSVs or CSV. In addition, the titres of IgG2a were heightened compared with IgG1 in SSV‐ or CSV‐immunized mice, which indicated that SSVs and CSV induced a typical T‐helper‐1‐dominated immune response in vivo. Further investigation of the CSV showed a superior protective effect in mice against brucellosis. The protection level induced by CSV was significantly higher than that induced by SSVs, which was not significantly different compared with a group immunized with RB51. Collectively, these antigens of Brucella could be potential candidates to develop subunit vaccines, and the CSV used in this study could be a potential candidate therapy for the prevention of brucellosis.

Peptide-Based Vaccines for Tuberculosis

Tuberculosis (TB) is an infectious disease caused by Mycobacterium tuberculosis. As a result of the coronavirus disease 2019 (COVID-19) pandemic, the global TB mortality rate in 2020 is rising, making TB prevention and control more challenging. Vaccination has been considered the best approach to reduce the TB burden. Unfortunately, BCG, the only TB vaccine currently approved for use, offers some protection against childhood TB but is less effective in adults. Therefore, it is urgent to develop new TB vaccines that are more effective than BCG. Accumulating data indicated that peptides or epitopes play essential roles in bridging innate and adaptive immunity and triggering adaptive immunity. Furthermore, innovations in bioinformatics, immunoinformatics, synthetic technologies, new materials, and transgenic animal models have put wings on the research of peptide-based vaccines for TB. Hence, this review seeks to give an overview of current tools that can be used to design a peptide-based vaccine, the research status of peptide-based vaccines for TB, protein-based bacterial vaccine delivery systems, and animal models for the peptide-based vaccines. These explorations will provide approaches and strategies for developing safer and more effective peptide-based vaccines and contribute to achieving the WHO’s End TB Strategy.

Prophylactic vaccine delivery systems against epidemic infectious diseases

Prophylactic vaccines have evolved from traditional whole-cell vaccines to safer subunit vaccines. However, subunit vaccines still face problems, such as poor immunogenicity and low efficiency, while traditional adjuvants are usually unable to meet specific response needs. Advanced delivery vectors are important to overcome these barriers; they have favorable safety and effectiveness, tunable properties, precise location, and immunomodulatory capabilities. Nevertheless, there has been no systematic summary of the delivery systems to cover a wide range of infectious pathogens. We herein summarized and compared the delivery systems for major or epidemic infectious diseases caused by bacteria, viruses, fungi, and parasites. We also included the newly licensed vaccines (e.g., COVID-19 vaccines) and those close to licensure. Furthermore, we highlighted advanced delivery systems with high efficiency, cross-protection, or long-term protection against epidemic pathogens, and we put forward prospects and thoughts on the development of future prophylactic vaccines.

Hybrid recombinant Omp 22, 25, and 31 immunodominant epitopes can be used for serodiagnosis of brucellosis

Brucellosis is a well-known infectious disease in most parts of the world, especially in developing countries, common between humans and animals. Brucellosis is diagnosed by serological tests based on lipopolysaccharides (LPSs), which are bacterial cell wall antigens, and due to the similarities between LPSs antigens of some gram-negative bacterias, false-positive responses are inevitable. Alternatively, Outer membrane proteins (Omps), as antigenic conserved membrane proteins, can be used to diagnose brucellosis instead of LPS antigens. In this study, by using bioinformatics tools, linear B-cell epitopes were selected from Omp22, Omp25, and Omp31 antigens and fused with the rigid KP linker (K = Lysine, P=Proline). Designed gene cassette was cloned into pET-28a (+) vector and expressed recombinant protein was purified using Ni-NTA chromatography column and was confirmed with Poly-Histidine-HRP antibody. Finally, recombinant protein's seroreactivity with serum samples from 37 patients and 27 healthy individuals was evaluated by western blotting and enzyme-linked immunosorbent assay (ELISA) methods. Western blotting results showed high reactivity of the recombinant protein with serum samples of Brucella infected patients. ELISA results were analyzed using the receiver operating curve (ROC). Optical density cut-off point, accuracy, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and Youden index J for recombinant protein were > 0.809, 84.37%,83.78%,88.89%,88.57%, 79.31% and 0.72 respectively. Western blotting and ELISA results showed that our recombinant protein has good sensitivity and specificity for the diagnosis of brucellosis.

Plasmid Replicons for the Production of Pharmaceutical-Grade pDNA, Proteins and Antigens by Lactococcus lactis Cell Factories

The Lactococcus lactis bacterium found in different natural environments is traditionally associated with the fermented food industry. But recently, its applications have been spreading to the pharmaceutical industry, which has exploited its probiotic characteristics and is moving towards its use as cell factories for the production of added-value recombinant proteins and plasmid DNA (pDNA) for DNA vaccination, as a safer and industrially profitable alternative to the traditional Escherichia coli host. Additionally, due to its food-grade and generally recognized safe status, there have been an increasing number of studies about its use in live mucosal vaccination. In this review, we critically systematize the plasmid replicons available for the production of pharmaceutical-grade pDNA and recombinant proteins by L. lactis. A plasmid vector is an easily customized component when the goal is to engineer bacteria in order to produce a heterologous compound in industrially significant amounts, as an alternative to genomic DNA modifications. The additional burden to the cell depends on plasmid copy number and on the expression level, targeting location and type of protein expressed. For live mucosal vaccination applications, besides the presence of the necessary regulatory sequences, it is imperative that cells produce the antigen of interest in sufficient yields. The cell wall anchored antigens had shown more promising results in live mucosal vaccination studies, when compared with intracellular or secreted antigens. On the other side, engineering L. lactis to express membrane proteins, especially if they have a eukaryotic background, increases the overall cellular burden. The different alternative replicons for live mucosal vaccination, using L. lactis as the DNA vaccine carrier or the antigen producer, are critically reviewed, as a starting platform to choose or engineer the best vector for each application.

Salmonella Vaccine Vector System for Foot-and-Mouth Disease Virus and Evaluation of Its Efficacy with Virus-Like Particles

Foot-and-mouth disease virus (FMDV) causes a highly contagious and devastating disease in livestock animals and has a great potential to cause severe economic loss worldwide. The major antigen of FMDV capsid protein, VP1, contains the major B-cell epitope responsible for effectively eliciting protective humoral immunity. In this study, irradiated Salmonella Typhimurium (KST0666) were used as transgenic vectors containing stress-inducible plasmid pRECN-VP1 to deliver the VP1 protein from FMDV-type A/WH/CHA/09. Mice were orally inoculated with ATOMASal-L3 harboring pRECN-VP1, and FMDV virus-like particles, where (VLP_FMDV)-specific humoral, mucosal, and cellular immune responses were evaluated. Mice vaccinated with attenuated Salmonella (KST0666) expressing VP1 (named KST0669) showed high levels of VLP-specific IgA in feces and IgG in serum, with high FMDV neutralization titer. Moreover, KST0669-vaccinated mice showed increased population of IFN-γ (type 1 T helper cells; Th1 cells)-, IL-5 (Th2 cells)-, and IL-17A (Th17 cells)-expressing CD4⁺ as well as activated CD8⁺ T cells (IFN-γ⁺CD8⁺ cells), detected by stimulating VLP_FMDV. All data indicate that our Salmonella vector system successfully delivered FMDV VP1 to immune cells and that the humoral and cellular efficacy of the vaccine can be easily evaluated using VLP_FMDV in a Biosafety Level I (BSL1) laboratory.