Construction of recombinant Mip-FlaA dominant epitope vaccine against Legionella pneumophila and evaluation of the immunogenicity and protective immunity

Identification and characterization of a PL35 GAGs lyase with 4-O-sulfated N-acetylgalactosamine (A-type)-rich structures producing property

Glycosaminoglycan (GAG) lyases are important tools for investigating the structure of GAGs and preparing low-molecular-weight GAGs. The PL35 family, a recently established polysaccharide lyase family, should be further investigated. In this study, we discovered a new GAG lyase, CHa1, which belongs to the PL35 family. When expressed heterologously in Escherichia coli (BL21), CHa1 exhibited high expression levels and solubility. The optimal activity was observed in Tris-HCl buffer (pH 7.0) or sodium phosphate buffer (pH 8.0) at 30 °C. The specific activities towards HA, CSA, CSC, CSD, CSE, and HS were 3.81, 13.03, 36.47, 18.46, 6.46, and 0.50 U/mg protein, respectively. CHa1 digests substrate chains randomly that acting as an endolytic lyase and shows a significant preference for GlcA-containing structures, prefers larger oligosaccharides (≥UDP8) and can generate a series of oligosaccharides composed mainly of the A unit when digesting CSA. These oligosaccharides include ΔC-A, ΔC-A-A, ΔC-A-A-A, ΔC-A-A-A-A, and ΔC-A-A-A-A-A. The residues Tyr257 and His421 play crucial roles in the catalytic process, and Ser211, Asn212, Asn213, Trp214, Gln216, Lys360, Arg460 and Gln462 may participate in the binding process of CHa1. This study on CHa1 contributes to our understanding of the PL35 family and provides valuable tools for investigating the structure of GAGs.

Development of dominant epitope-based vaccines encoding Gp63, Kmp-11 and Amastin against visceral leishmaniasis

The most dangerous form of leishmaniasis is Visceral leishmaniasis (VL). The elimination of VL depends not only on agent treatments but also on effective vaccines against Leishmania parasites. Epitope-based vaccines composed of alternative short antigenic epitopes have the advantages of MHC epitope easy designing, which has broad application prospects. In a previous study, we analyzed Leishmania Gp63, Kmp-11 and Amastin protein sequence in silico, and found that the amino acid fragments of Gp63 (138-360aa), Kmp-11 (1-91aa) and Amastin (1-72aa) were rich in dominant epitopes. In this study, we used the three amino acid fragments as multi-epitope vaccine candidates to construct DNA and protein vaccines. BALB/c mice were vaccinated with the DNA and protein vaccines by DNA prime-protein boost strategy and challenged with Leishmania promastigotes. To evaluate vaccine immunogenicity and immunoprotection, serum specific antibody titers and cytokines were detected using ELISA, splenic CD3⁺, CD4⁺ and CD8⁺ cells were analyzed by flow cytometry, livers were made into pathological sections to observe pathological changes, and splenic parasitic loads were quantified using qPCR. The results showed that the increased specific IgG titers from vaccinated mice supported the vaccine immunogenicity. The increased cytokines (IFN-γ, IL-12 and TNF-α), splenic CD3⁺, CD4⁺ and CD8⁺ T cells and hepatic granulomas, and the decreased splenic parasitic loads (parasite reduction rates of Gp63, Kmp-11 and Amatin groups were 89%, 86% and 79%, respectively) from immunized mice post-infection were suggested the good immunoprotection of the vaccines. Our study demonstrated that vaccines based on the dominant epitopes of Gp63, Kmp-11 and Amastin with DNA prime-protein boost vaccination strategy showed significant immune effects against Leishmania, especially the Gp63 group showed a nearly 90% parasites reduction rate. This study will provide references for visceral leishmaniasis epitope vaccine design and immune strategy selection.

Recombinant PAL/PilE/FlaA DNA vaccine provides protective immunity against Legionella pneumophila in BALB/c mice

Background

Legionella pneumophila (L.pneumophila), a Gram-negative small microorganism, causes hospital-acquired pneumonia especially in immunocompromised patients. Vaccination may be an effective method for preventing L.pneumophila infection. Therefore, it is necessary to develop a better vaccine against this disease. In this study, we developed a recombinant peptidoglycan-associated lipoprotein (PAL)/type IV pilin (PilE)/lagellin (FlaA) DNA vaccine and evaluated its immunogenicity and efficacy to protect against L.pneumophila infection.

Results

According to the results, the expression of PAL, PilE, FlaA proteins and PAL/PilE/FlaA fusion protein in 293 cells was confirmed. Immunization with PAL/PilE/FlaA DNA vaccine resulted in highest IgG titer and strongest cytotoxic T-lymphocyte (CTL) response. Furthermore, the histopathological changes in lung tissues of mice challenged with a lethal dose of L.pneumophila were alleviated by PAL/PilE/FlaA DNA vaccine immunization. The production of T-helper-1 (Th1) cytokines (IFNγ, TGF-α, and IL-12), and Th2 cytokines (IL-4 and IL-10) were promoted in PAL/PilE/FlaA DNA vaccine group. Finally, immunization with PAL/PilE/FlaA vaccine raised the survival rate of mice to 100% after challenging with a lethal dose of L.pneumophila for 10 consecutive days.

Conclusions

Our study suggests that the newly developed PAL/PilE/FlaA DNA vaccine stimulates strong humoral and cellular immune responses and may be a potential intervention on L.pneumophila infection.

The immunogenicity and protective immunity of multi-epitopes DNA prime-protein boost vaccines encoding Amastin-Kmp-11, Kmp11-Gp63 and Amastin-Gp63 against visceral leishmaniasis

Visceral leishmaniasis (VL) is the most fatal form of leishmaniasis if left untreated and 50,000 to 90,000 new cases of VL occur worldwide each year. Although various vaccines had been studied in animal models, none of them was eligible to prevent human from infections. In this study, according to the silico analysis of Leishmania Amastin, Kmp-11 and Gp63 protein, dominant epitope sequences of these proteins were selected and linked to construct dominant multi-epitopes DNA and protein vaccines (Amastin-Kmp-11, Amastin-Gp63 and Kmp-11-Gp63) against VL. BALB/c mice were immunized with a DNA prime-protein boost immunization strategy and challenged with a new Leishmania parasite strain isolated from a VL patient. After immunization, the results including specific antibody titers, IL-4 and TNF-α levels, and CD4 and CD8 T cell proportion suggested the potent immunogenicity of the three vaccines. After infection, the results of spleen parasite burdens in the three vaccine groups were significantly lower than those of control groups, and the parasite reduction rates of Amastin-Kmp-11, Amastin-Gp63 and Kmp-11-Gp63 groups were 89.38%, 91.01% and 88.42%, respectively. Spleen smear observation and liver histopathological changes showed that all vaccine groups could produce significant immunoprotection against VL and Amastin-Gp63 vaccine was the best. In conclusion, our work demonstrated that the three dominant multi-epitopes Amastin-Kmp-11, Amastin-Gp63 and Kmp-11-Gp63 DNA prime-protein boost vaccines might be new vaccine candidates for VL, and the Amastin-Gp63 vaccine have best efficacy.