DNA prime-protein boost vaccine encoding HLA-A2, HLA-A24 and HLA-DR1 restricted epitopes of CaNA2 against visceral leishmaniasis

The immunogenic potential of an optimized mRNA lipid nanoparticle formulation carrying sequences from virus and protozoan antigens

BACKGROUND

Lipid nanoparticles (LNP) are a safe and effective messenger RNA (mRNA) delivery system for vaccine applications, as shown by the COVID-19 mRNA vaccines. One of the main challenges faced during the development of these vaccines is the production of new and versatile LNP formulations capable of efficient encapsulation and delivery to cells in vivo. This study aimed to develop a new mRNA vaccine formulation that could potentially be used against existing diseases as well as those caused by pathogens that emerge every year.

RESULTS

Using firefly luciferase (Luc) as a reporter mRNA, we evaluated the physical-chemical properties, stability, and biodistribution of an LNP-mRNA formulation produced using a novel lipid composition and a microfluidic organic-aqueous precipitation method. Using mRNAs encoding a dengue virus or a Leishmania infantum antigen, we evaluated the immunogenicity of LNP-mRNA formulations and compared them with the immunization with the corresponding recombinant protein or plasmid-encoded antigens. For all tested LNP-mRNAs, mRNA encapsulation efficiency was higher than 85%, their diameter was around 100 nm, and their polydispersity index was less than 0.3. Following an intramuscular injection of 10 µg of the LNP-Luc formulation in mice, we detected luciferase activity in the injection site, as well as in the liver and spleen, as early as 6 h post-administration. LNPs containing mRNA encoding virus and parasite antigens were highly immunogenic, as shown by levels of antigen-specific IgG antibody as well as IFN-γ production by splenocytes of immunized animals that were similar to the levels that resulted from immunization with the corresponding recombinant protein or plasmid DNA.

CONCLUSIONS

Altogether, these results indicate that these novel LNP-mRNA formulations are highly immunogenic and may be used as novel vaccine candidates for different infectious diseases.

Expression of codon-optimized PDCoV-RBD protein in baculovirus expression system and immunogenicity evaluation in mice

Porcine deltacoronavirus (PDCoV) is a global epidemic enteropathogenic coronavirus that mainly infects piglets, and causes huge losses to the pig industry. However, there are still no commercial vaccines available for PDCoV prevention and controlment. Receptor-binding domain (RBD) is located at the S1 subunit of PDCoV and is the major target for developing viral inhibitor and vaccine. In this study, the characteristics of the RBD were analyzed by bioinformatic tools, and codon optimization was performed to efficiently express the PDCoV-RBD protein in the insect baculovirus expression system. The purified PDCoV-RBD protein was obtained and fully emulsified with CPG2395 adjuvant, aqueous adjuvant and Al(OH)3 adjuvant, respectively, to develop vaccines. The humoral and cellular immune responses were assessed on mice. The results showed that both the RBD/CPG2395 and RBD/aqueous adjuvant could induce stronger immune responses in mice than that of RBD/Al(OH)3. In addition, the PDCoV challenge infection was conducted and the RBD/CPG2395 could provide better protection against PDCoV in mice. Our study showed that the RBD protein has good antigenicity and can be used as a protective antigen, which provided a basis for the development of the PDCoV vaccine.

TLR9 agonist CpG ODN 2395 promotes the immune response against Leishmania donovani in obesity and undernutrition mice

As important immunomodulators, CpG ODNs have broad application prospects in the treatment and prevention of leishmaniasis. In order to explore the immunomodulatory effect of CpG ODNs on mice infected with Leishmania parasites in different nutritional status, TLR9 agonist CpG ODN 2395 or TLR9 antagonist CpG ODN 2088 was injected into normal, obesity and undernutrition BALB/c mice infected with Leishmania donovani, respectively. Subsequently, spleen and liver parasite loads, spleen and liver immune gene expression, spleen T cell subsets proportion and PD-1 expression, serum lipids, serum cytokines, and anti-Leishmania antibodies were measured to assess the immune response of mice with different nutritional status. The results displayed that at the 8th week after infection, the spleen parasite load of obesity and undernutrition mice was significantly higher than that of normal mice, but the liver parasite load showed no statistical difference among the three groups. The treatment of CpG ODN 2395 or CpG ODN 2088 significantly reduced the spleen parasite load of obesity and undernutrition infected mice, but did not reduce that of normal infected mice. In obesity infected mice, CpG ODN 2395 promoted the up-regulation of TCR, ICOS and TLR4 in spleen, promoted the secretion of IFN-γ and anti-Leishmania total IgG and IgG1 antibodies, and increased the content of serum HDL-C. In undernutrition infected mice, CpG ODN 2395 promoted the up-regulation of spleen CD28 and TLR9, increased the proportion of spleen CD3⁺ T cells, and decreased the content of serum IL-10. Our results demonstrated that CpG ODN 2395 enhanced the immune response and clearance of Leishmania parasites in obesity and undernutrition mice, which might be used as a therapeutic agent for obesity and undernutrition leishmaniasis patients in the future.

Anti-leishmanial therapy: Caught between drugs and immune targets

Leishmaniasis is an enigmatic disease that has very restricted options for chemotherapy and none for prophylaxis. As a result, deriving therapeutic principles for curing the disease has been a major objective in Leishmania research for a long time. Leishmania is a protozoan parasite that lives within macrophages by subverting or switching cell signaling to the pathways that ensure its intracellular survival. Therefore, three groups of molecules aimed at blocking or eliminating the parasite, at least, in principle, include blockers of macrophage receptor- Leishmania ligand interaction, macrophage-activating small molecules, peptides and cytokines, and signaling inhibitors or activators. Macrophages also act as an antigen-presenting cell, presenting antigen to the antigen-specific T cells to induce activation and differentiation of the effector T cell subsets that either execute or suppress anti-leishmanial functions. Three groups of therapeutic principles targeting this sphere of Leishmania-macrophage interaction include antibodies that block pro-leishmanial response of T cells, ligands that activate anti-leishmanial T cells and the antigens for therapeutic vaccines. Besides these, prophylactic vaccines have been in clinical trials but none has succeeded so far. Herein, we have attempted to encompass all these principles and compose a comprehensive review to analyze the feasibility and adoptability of different therapeutics for leishmaniasis.

Mutation Characteristics and Phylogenetic Analysis of Five Leishmania Clinical Isolates

Simple Summary

Leishmaniasis, a neglected tropical disease, is caused by infection with the Leishmania species, threatening millions of people in approximately 100 endemic countries. The emergence of antimony-resistant Leishmania strains have brought difficulties to the treatment and elimination of leishmaniasis. This study performed genome-wide resequencing and phylogenetic analysis of five isolates from the Leishmania donovani complex, focusing on finding mutations related to antimony resistance and virulence of the newly isolated Leishmania strain L_HCZ in 2016. By combining whole-genome sequencing and whole-genome phylogenetic analysis, Leishmania isolates L_801, L_9044 and L_Liu were identified as Leishmania donovani, and L_HCZ as Leishmania infantum. By discovering genome-wide single-nucleotide polymorphisms and structural variations, we identified mutations of drug resistance-related genes in the antimony-resistant Leishmania isolate L_HCZ. The new Leishmania isolate L_HCZ has strong virulence and strong drug resistance, which should be taken seriously by the relevant health departments and scientific researchers.

Abstract

Leishmaniasis is a neglected tropical disease threatening millions of people worldwide. The emergence of antimony-resistant Leishmania strains have brought difficulties to the treatment and elimination of leishmaniasis. This study performed genome sequencing, phylogenetic analysis and mutation analysis of five Leishmania clinical isolates, especially the Leishmania strain L_HCZ isolated in 2016, which shows strong virulence and antimony resistance. By phylogenetic analysis, four isolates (L_DD8, L_801, L_Liu and L_9044) were identified as Leishmania donovani, the isolate L_HCZ was identified as Leishmania infantum and the isolate L_DD8 as a standard strain of L.donovani. Genome-wide mutation analysis was applied to identify mutations related to the drug resistance and virulence of the newly isolated L_HCZ. Compared with the other four Leishmania isolates, L_HCZ had the most mutations in genes associated with antimony resistance, including the ABC transporter, ascorbate-dependent peroxidase, gamma–glutamylcysteine synthetase, glucose-6-phosphate 1-dehydrogenase, ATP-binding cassette protein subfamily A and multi-drug resistance protein-like genes. Among the genes associated with virulence, L_HCZ had the most mutations in cysteine peptidase A, cysteine peptidase B, cysteine peptidase C, heat-shock protein 70, gp63, acid phosphatase, kinesin k39, kinesin, phosphoglycan beta 1, amastin-like surface protein and amastin-like proteins. The mutations in L_HCZ might possibly contribute to its antimony resistance and strong virulence in clinical patients. Whole-genome resequencing has exhibited broad application prospects and may be put into clinical use in the future for parasite identifying and epidemiological investigations.

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.

[Construction and Expression of Eukaryotic and Prokaryotic Recombinant Vectors of Pepck and Gp63 Dominant Epitopes of Leishmania infantum]

OBJECTIVE

To construct eukaryotic and prokaryotic recombinant vectors containing Pepck- Gp63 and to achieve protein expression by selecting the dominant epitope genes of Pepck and Gp63 of Leishmania infantum.

METHODS

The secondary structure and HLA epitopes of phosphoenolpyruvate carboxylase (PEPCK) were predicted by in silico analysis, and the dominant epitopes were picked out. According to the analysis results of glycoprotein of 63×10 3(GP63) epitopes identified by the same method in our laboratory, the dominant epitope genes of Pepck and Gp63 were used to construct pET32a- Pepck- Gp63 and pVAX1- Pepck- Gp63 by overlapping PCR and enzyme reaction. Then, for protein expression, the prokaryotic vectors were transfected into E.coil while the eukaryotic vectors were transfected into NIH3T3 cells by liposome transfection.

RESULTS

There were multiple dominant epitopes in Pepckand there were Pepck-Gp63 sequences in the polyclonal site of expression vector. The expression of Pepck-Gp63 in E.coil appeared in inclusion form and led to 74 kDa band in SDS-PAGE. The immunofluorescence results of NIH3T3 cells transfected by pVAX1- Pepck-Gp63 were positive.

CONCLUSION

The recombinant prokaryotic expression plasmids pET32a- Pepck-Gp63 and eukaryotic expression plasmids pVAX1- P epck -Gp63 were successfully constructed, and it was shown that the recombinant plasmids were able to express the corresponding target proteins in E. coli and NIH3T3 cells, respectively, providing a preliminary experimental basis for the subsequent study of immunization strategies.

Excavating SARS-coronavirus 2 genome for epitope-based subunit vaccine synthesis using immunoinformatics approach

Since the outbreak of severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) in December 2019 in China, there has been an upsurge in the number of deaths and infected individuals throughout the world, thereby leading to the World Health Organization declaration of a pandemic. Since no specific therapy is currently available for the same, the present study was aimed to explore the SARS-CoV-2 genome for the identification of immunogenic regions using immunoinformatics approach. A series of computational tools were applied in a systematic way to identify the epitopes that could be utilized in vaccine development. The screened-out epitopes were passed through several immune filters, such as promiscuousity, conservancy, antigenicity, nonallergenicity, population coverage, nonhomologous to human proteins, and affinity with human leukocyte antigen alleles, to screen out the best possible ones. Further, a construct comprising 11 CD4, 12 CD8, 3 B cell, and 3 interferon-γ epitopes, along with an adjuvant β-defensin, was designed in silico, resulting in the formation of a multiepitope vaccine. The in silico immune simulation and population coverage analysis of the vaccine sequence showed its capacity to elicit cellular, humoral, and innate immune cells and to cover up a worldwide population of more than 97%. Further, the interaction analysis of the vaccine construct with Toll-like receptor 3 (immune receptor) was carried out by docking and dynamics simulations, revealing high affinity, constancy, and pliability between the two. The overall findings suggest that the vaccine may be highly effective, and is therefore required to be tested in the lab settings to evaluate its efficacy.

Leishmania eukaryotic elongation Factor-1 beta protein is immunogenic and induces parasitological protection in mice against Leishmania infantum infection

Treatment for visceral leishmaniasis (VL) is hampered mainly by the toxicity and/or high cost of antileishmanial drugs. What is more, variability on sensitivity and/or specificity of diagnostic tests hinders effective disease management. In this context, prophylactic vaccination should be considered as a strategy to prevent disease. In the present study, immunogenicity of the Leishmania eukaryotic Elongation Factor-1 beta (EF1b) protein, classified as a Leishmania virulence factor, was evaluated in vitro and in vivo and tested, for the first time, as a vaccine candidate against Leishmania infantum infection. The antigen was administered as DNA vaccine or as recombinant protein (rEF1b) delivered in saponin. BALB/c mice immunization with a DNA plasmid and recombinant protein plus saponin induced development of specific Th1-type immunity, characterized by high levels of IFN-γ, IL-12, GM-CSF, both T cell subtypes and antileishmanial IgG2a isotype antibodies, before and after infection. This immunological response to the vaccines was corroborated further by parasitological analysis of the vaccinated and then challenged mice, which showed significant reductions in the parasite load in their liver, spleen, bone marrow and draining lymph nodes, when compared to the controls. Vaccination using rEF1b/saponin induced a more robust Th1 response and parasitological protection when compared to the DNA vaccine. Furthermore, in vitro analysis of lymphoproliferation, IFN-γ and IL-10 levels in human PBMC cultures showed as well development of a specific Th1-type response. In conclusion, data suggest that EF1b could be a promising vaccine candidate to protect against L. infantum infection.

Integrative genomic, proteomic and phenotypic studies of Leishmania donovani strains revealed genetic features associated with virulence and antimony-resistance

Background

Leishmaniasis is a neglected tropical disease affecting millions of people worldwide. Emerging drug resistance of Leishmania species poses threaten to the effective control and elimination programme of this neglected tropical disease.

Methods

In this work, we conducted drug-resistance testing, whole genome resequencing and proteome profiling for a recently reported clinical isolate with supposed drug resistance (HCZ), and two reference sensitive strains (DD8 and 9044) of Leishmania donovani, to explore molecular mechanisms underlying drug resistance in this parasite.

Results

With reference to DD8 and 9044 strains, HCZ isolate showed higher-level virulence and clear resistance to antimonials in promastigote culture, infected macrophages and animal experiment. Pairwise genomic comparisons revealed genetic variations (86 copy number variations, 271 frameshift mutations in protein-coding genes and two site mutations in non-coding genes) in HCZ isolate that were absent from the reference sensitive strains. Proteomic analysis indicated different protein expression between HCZ isolate and reference strains, including 69 exclusively detected proteins and 82 consistently down-/upregulated molecules in the HCZ isolate. Integrative analysis showed linkage of 12 genomic variations (gene duplication, insertion and deletion) and their protein expression changes in HCZ isolate, which might be associated with pathogenic and antimony-resistant phenotype. Functional annotation analyses further indicated that molecules involved in nucleotide-binding, fatty acid metabolism, oxidation-reduction and transport might play a role in host-parasite interaction and drug-resistance.

Conclusions

This comprehensive integrative work provided novel insights into the genetic basis underlying virulence and resistance, suggesting new aspects to be investigated for a better intervention against L. donovani and associated diseases.

Pulmonary mucosal immunity mediated through CpG provides adequate protection against pulmonary Mycobacterium tuberculosis infection in the mouse model. A role for type I interferon

Toll-Like Receptor (TLR) 9 stimulation is required for induction of potent immune responses against pathogen invasion. The use of unmethylated CpG as adjuvants in vaccines provides an excellent means of stimulating adaptive immunity. Our data demonstrate that CpG-C provided prolonged immune responses in the mouse model of tuberculosis when formulated with liposomes and the Mycobacterium tuberculosis antigen ESAT-6. A reduction in the mycobacterial burden was best achieved when administered as an intranasal vaccine and was dependent on type I interferon (IFN). There was a significant difference between CpG-C inoculated wild type and IFN-αR1^-/- mice, indicating that type I IFN plays a role in the immune response following CpG-C inoculation. Further analysis showed that early NK cell presence was not an absolute requirement, although elevated IFN-γ levels were detected in the lungs of mice within 48 h. The reduction in mycobacterial burden was MyD88-independent as CpG-C inoculated MyD88^-/- mice showed comparable mycobacterial burdens to wild type mice with no detriment due to the lack of MyD88. Together our data show that pulmonary stimulation of TLR9 bearing antigen presenting cells resulted in the induction of protective immunity against M. tuberculosis infection that was dependent on type I IFN signaling.

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.

Leishmania infantum amastin protein incorporated in distinct adjuvant systems induces protection against visceral leishmaniasis

The control measures against visceral leishmaniasis (VL) include a precise diagnosis of disease, the treatment of human cases, and reservoir and vector controls. However, these are insufficient to avoid the spread of the disease in specific countries worldwide. As a consequence, prophylactic vaccination could be interesting, although no effective candidate against human disease is available. In the present study, the Leishmania infantum amastin protein was evaluated regarding its immunogenicity and protective efficacy against experimental VL. BALB/c mice immunized with subcutaneous injections of the recombinant protein with or without liposome/saponin (Lip/Sap) as an adjuvant. After immunization, half of the animals per group were euthanized and immunological evaluations were performed, while the others were challenged with L. infantum promastigotes. Forty-five days after infection, the animals were euthanized and parasitological and immunological evaluations were performed. Results showed the development of a Th1-type immune response in rAmastin-Lip and rAmastin-Sap/vaccinated mice, before and after infection, which was based on the production of protein and parasite-specific IFN-γ, IL-12, GM-CSF, and nitrite, as well as the IgG2a isotype antibody. CD4⁺ T cells were mainly responsible for IFN-γ production in vaccinated mice, which also presented significant reductions in parasitism in their liver, spleen, draining lymph nodes, and bone marrow. In addition, PBMC cultures of treated VL patients and healthy subjects stimulated with rAmastin showed lymphoproliferation and higher IFN-γ production. In conclusion, the present study shows the first case of an L. infantum amastin protein associated with distinct delivery systems inducing protection against L. infantum infection and demonstrates an immunogenic effect of this protein in human cells.

Sophisticated specificity in the innate immune response

Immunologists are sometimes guilty of describing the innate immune response as 'non-specific'. What we really mean is that the pattern recognition receptors of innate immune cells are not able to recombine and mutate to bind the spectacular range of molecular patterns that can be recognised by B and T cells. So, while it may be accurate to describe the innate immune response as less specific than adaptive immunity, even this belies the emerging complexity of the receptors and receptor complexes that control inflammatory responses. This complexity is necessary to recognise danger, and therefore successfully initiate proportionate inflammatory responses to cellular damage or against potential pathogens.