Nucleoside Hydrolase NH 36: A Vital Enzyme for the Leishmania Genus in the Development of T-Cell Epitope Cross-Protective Vaccines

NH36 is a vital enzyme of the DNA metabolism and a specific target for anti-Leishmania chemotherapy. We developed second-generation vaccines composed of the FML complex or its main native antigen, the NH36 nucleoside hydrolase of Leishmania (L.) donovani and saponin, and a DNA vaccine containing the NH36 gene. All these vaccines were effective in prophylaxis and treatment of mice and dog visceral leishmaniasis (VL). The FML-saponin vaccine became the first licensed veterinary vaccine against leishmaniasis (Leishmune®) which reduced the incidence of human and canine VL in endemic areas. The NH36, DNA or recombinant protein vaccines induced a Th1 CD4+IFN-γ+ mediated protection in mice. Efficacy against VL was mediated by a CD4+TNF-α T lymphocyte response against the NH36-F3 domain, while against tegumentary leishmaniasis (TL) a CD8+ T lymphocyte response to F1 was also required. These domains were 36–41 % more protective than NH36, and a recombinant F1F3 chimera was 21% stronger than the domains, promoting a 99.8% reduction of the parasite load. We also identified the most immunogenic NH36 domains and epitopes for PBMC of active human VL, cured or asymptomatic and DTH+ patients. Currently, the NH36 subunit recombinant vaccine is turning into a multi-epitope T cell synthetic vaccine against VL and TL

Vaccination with Nucleoside Hydrolase (NH36) of L.(L.) Donovani or its C-terminal Portion (F3) in Formulation with Saponin Prevents the Increase of the Proportions of Spleen Dendritic Cells in Murine Experimental Visceral Leishmaniasis

AbstractVisceral leishmaniasis is a chronicand lethal parasite disease against which no human vaccine is available.Hepato- splenomegaly and a progressive suppression of the cellular immune response are among its most important clinical signs. The characteristic cellular immunosupression was described as being mediated in part, through the spatial segregation of dendritic cells (DCs) and T cell lymphocytes due to altered frequencies and migration capabilities of DCs. In this investigation, we measured the spleen/body relative weight, the spleen parasite load and the total counts of spleen DCs of C57BL6 mice infected with Leishmania chagasi. All the variables achieved their maximum at 30 days after infection. We detected in infected animals a 5.08 fold increase of spleen relative weight, a 19.6 fold increase of parasite load and a 4.55 increase of total DCs counts, when compared to naïve controls. We further analysed the efficacy of the NH36 and F3 vaccines formulated in saponin in prevention of visceral leishmaniasis. When compared to the infected controls, both vaccines determined strong protection. The F3 vaccine induced the highest efficacy showing 95% and 49% reduction the parasite load and splenomegaly, respectively. The NH36 vaccine, on the other hand, developed a slightly lower but still significant protection reducing by 87% the parasite load and by 39% the spleen relative weight. Both vaccines also prevented the increase in total counts of DCs with no significant difference between them (36% by the NH36 and 26% by the F3 vaccine). Our results suggest that vaccination against murine visceral leishmaniasis with the NH36 vaccine can prevent the development of the disease by preventing the DCs dysfunction-related immunosupression. Additionally, they disclose the potential use of the NH36 C-terminal moiety, the F3 peptide for optimization of the vaccine efficacy

Editorial: Epitope Discovery and Synthetic Vaccine Design

Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Fundacao Carlos Chagas de Amparo a Pesquisa do Estado de Rio de Janeiro (FAPERJ)Univ Fed Rio de Janeiro, Lab Biol Bioquim Leishmania Microbiol Geral, Rio De Janeiro, BrazilUniv Sao Paulo, Fac Med, Inst Invest Imunol, Sao Paulo, BrazilUniv Sao Paulo, Dept Clin & Toxicol Anal, Sao Paulo, BrazilUniv Fed Sao Paulo UNIFESP, Dept Microbiol Imunol & Parasitol, Sao Paulo, BrazilUniv Fed Sao Paulo UNIFESP, Dept Microbiol Imunol & Parasitol, Sao Paulo, BrazilCNPq: 310977/2014-2CNPq: 404400/2012-4FAPERJ: E-26-201.583/2014FAPERJ: E-26-102957/2011FAPERJ: E-26/111.682/2013Web of Scienc

Epitope Discovery and Synthetic Vaccine Design

Since variolation, conventional approaches to vaccine development are based on live-attenuated, inactivated or purified pathogen-derived components. However, effective vaccines against global health threats such as HIV, parasite infections and tumors are difficult to achieve. On the other hand, synthetic vaccines based on immunogenic epitopes offer advantages over traditional vaccines since they are chemically defined antigens free from deleterious effects. Additionally, in contrast to live-attenuated vaccines, they do not revert to virulence in immunocompromised subjects, and different from genetic vaccines, they do not involve ethical questions. Traditional vaccines contain PAMPs and induce strong immune responses, while recombinant vaccines are less potent. In spite of the immunogenic weakness previously attributed to epitope-based vaccines a synthetic vaccine containing a 17 amino acid-epitope of the Pseudomonas aeruginosa Type IV pilus exceeded the protective potential of its cognate protein composed of 115 amino acids. Therefore, the efficacy yield of a synthetic vaccine can be potentiated by using the proper combination of target epitopes. Recent advances in adjuvant development, immunogen platforms for DNA vaccines and viral vectors also contributed to optimize immunogenicity. Another constraint to the use of epitope vaccines was their restriction to some MHC or HLA phenotypes. However, epitopes containing 20 or less amino acids of Plasmodium falciparum and Leishmania donovani bind to multiple HLA-DR and MHC receptors. Thus synthetic epitope vaccines may better meet the requirements of the regulatory agencies since they have lower costs and are easier to produce. The classical experimental approach for the development of an epitope-based vaccine involves the use of recombinant domains or overlapping 15-mer peptides spanning the full length of the target antigen, and the analysis of the induced antibody and/or T cell immune responses in vitro or in vivo. On the other hand, in silico tools can select peptides that are more likely to contain epitopes, reducing the number of sequence candidates. T cell epitope prediction dates back to 1980s, when the first algorithm was developed based on the identification of amphipathic helical regions on protein antigens. Since then, new methods based on MHC peptide-binding motifs or MHC-binding properties have been developed. The recent reverse vaccinology concept uses high-throughput genome sequencing and bioinformatics tools to identify potential targets of immune responses. The feasibility of this approach was shown for the first time in the design of a vaccine against Neisseria meningitides that is now in phase III clinical trials. In addition, different computational tools allow the determination of crucial gene(s) through comparative analyses between different pathogenic strains Alternatively, carbohydrates have been considered as key targets in developing safe and effective vaccines to combat cancer, bacterial and viral infections. Tumor associated carbohydrate antigens can be coupled covalently to protein carriers to target MHC receptors and improve immunogenicity and have reached already pre-clinical and clinical studies. In light of the recent availability of genomic tools, we believe that in the near future an increasing number of vaccine candidates, composed of defined epitopes, will be available for synthetic vaccines showing improved protection

Image_3_NH36 and F3 Antigen-Primed Dendritic Cells Show Preserved Migrating Capabilities and CCR7 Expression and F3 Is Effective in Immunotherapy of Visceral Leishmaniasis.jpg

<p>Physical contact between dendritic cells (DCs) and T cell lymphocytes is necessary to trigger the immune cell response. CCL19 and CCL21 chemokines bind to the CCR7 receptor of mature DCs, and of T cells and regulate DCs migration to the white pulp (wp) of the spleen, where they encounter lymphocytes. In visceral leishmaniasis (VL), cellular immunosuppression is mediated by impaired DC migration due to the decreased chemokine secretion by endothelium and to the reduced DCs CCR7 expression. The Leishmania (L.) donovani nucleoside hydrolase NH36 and its C-terminal domain, the F3 peptide are prominent antigens in the generation of preventive immunity to VL. We assessed whether these vaccines could prevent the migrating defect of DCs by restoring the expression of CCR7 receptors. C57Bl6 mice were vaccinated with NH36 and F3 and challenged with L. (L.) infantum chagasi. The F3 vaccine induced a 100% of survival and a long-lasting immune protection with an earlier CD4⁺Th1 response, with secretion of higher IFN-γ and TNF-α/IL-10 ratios, and higher frequencies of CD4⁺ T cells secreting IL-2⁺, TNF-α⁺, or IFN-γ⁺, or a combination of two or the three cytokines (IL-2⁺TNF-α⁺IFN-γ⁺). The CD8⁺ T cell response was promoted earlier by the NH36-vaccine, and later by the F3-vaccine. Maximal number of F3-primed DCs migrated in vitro in response to CCL19 and showed a high expression of CCR7 receptors (26.06%). Anti-CCR7 antibody treatment inhibited DCs migration in vitro (90%) and increased parasite load in vivo. When transferred into 28-day-infected mice, only 8% of DCs from infected, 59% of DCs from NH36-vaccinated, and 84% of DCs from F3-vaccinated mice migrated to the wp. Consequently, immunotherapy of infected mice with F3-primed DCs only, promoted increases in corporal weight and reductions of spleen and liver parasite loads and relative weights. Our findings indicate that vaccination with F3-vaccine preserves the maturation, migration properties and CCR7 expression of DCs, which are essential processes for the generation of cell-mediated immunity. The F3 vaccine is more potent in reversing the migration defect that occurs in VL and, therefore, more efficient in immunotherapy of VL.</p

A novel vaccine based on SARS-CoV-2 CD4+ and CD8+ T cell conserved epitopes from variants Alpha to Omicron

COVID-19 caused, as of September, 1rst, 2022, 599,825,400 confirmed cases, including 6,469,458 deaths. Currently used vaccines reduced severity and mortality but not virus transmission or reinfection by different strains. They are based on the Spike protein of the Wuhan reference virus, which although highly antigenic suffered many mutations in SARS-CoV-2 variants, escaping vaccine-generated immune responses. Multiepitope vaccines based on 100% conserved epitopes of multiple proteins of all SARS-CoV-2 variants, rather than a single highly mutating antigen, could offer more long-lasting protection. In this study, a multiepitope multivariant vaccine was designed using immunoinformatics and in silico approaches. It is composed of highly promiscuous and strong HLA binding CD4+ and CD8+ T cell epitopes of the S, M, N, E, ORF1ab, ORF 6 and ORF8 proteins. Based on the analysis of one genome per WHO clade, the epitopes were 100% conserved among the Wuhan-Hu1, Alpha, Beta, Gamma, Delta, Omicron, Mµ, Zeta, Lambda and R1 variants. An extended epitope-conservancy analysis performed using GISAID metadata of 3,630,666 SARS-CoV-2 genomes of these variants and the additional genomes of the Epsilon, Lota, Theta, Eta, Kappa and GH490 R clades, confirmed the high conservancy of the epitopes. All but one of the CD4 peptides showed a level of conservation greater than 97% among all genomes. All but one of the CD8 epitopes showed a level of conservation greater than 96% among all genomes, with the vast majority greater than 99%. A multiepitope and multivariant recombinant vaccine was designed and it was stable, mildly hydrophobic and non-toxic. The vaccine has good molecular docking with TLR4 and promoted, without adjuvant, strong B and Th1 memory immune responses and secretion of high levels of IL-2, IFN-γ, lower levels of IL-12, TGF-β and IL-10, and no IL-6. Experimental in vivo studies should validate the vaccine's further use as preventive tool with cross-protective properties

The adjuvanticity of Chiococca alba saponins increases with the length and hydrophilicity of their sugar chains

The saponins of Chiococca alba are triterpene bidesmosides that contain glycidic moieties attached to the C-3 and C-28 carbon of their aglycone. We describe that their adjuvant potential increases in direct relationship to the length and hydrophilicity of the C-28 attached sugar chain which contains: arabinose-rhamnose in the CA2, arabinose-rhamnose-xylose in the CA3X; arabinose-rhamnose-apiose in the CA3 and arabinose-rhamnose-apiose-apiose in the CA4 saponin. the hydrophile/lipophile balance calculated for CA2 was 12.7, for CA3 and CA3X was 15.8 and for CA4 19.9. All saponins were formulated with the FML antigen for mice prophylaxis against visceral leishmaniasis. the immune response was studied using an ELISA-antibody assay and monitoring of the intradermal response (IDR) to Leishmania antigens, the cytokine expression in supernatants and the intracellular staining of in vitro cultured splenocytes. After challenge, significant increases of IgG and IgG2a antibodies were noted only in the CA4 vaccinated mice that showed extended IDR, higher IFN-gamma production by CD8+ and TNF-alpha production by CD4+ T cells, higher TNF-alpha secretion and the highest reduction of the parasite load (78%). the increases in IDR, CD4-TNF-alpha,CD8-IFN-gamma and CD8-TNF-alpha by the CA4 vaccine were strong correlates of protection and were significantly correlated to the decrease of parasite load (p=-0.007). Protection generated by the CA4 vaccine was mainly mediated by a CD4+ T cell and a TNF-alpha driven response with a lower contribution of CD8+ T cells, as confirmed by an in vivo depletion with monoclonal antibodies and by vaccination assays in TNF-alpha-receptor knock-out mice. Our results confirm that the superiority of the CA4 saponin is related to the higher hydrophilicity of its longer carbohydrate chain. C. alba saponins were non-toxic and only the xylose-containing saponin CA3X was hemolytic (HD50 = 87 mu g/ml). the increase in sugar units of the saponins is positively correlated to the increase of IDR and to the decrease of parasite load. (C) 2012 Elsevier B.V. All rights reserved.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)Univ Fed Rio de Janeiro, Inst Microbiol Paulo Goes, CCS, Ilha Fundao,Dept Microbiol Geral, BR-21941902 Rio de Janeiro, BrazilUniv Fed Rio de Janeiro, Nucleo Pesquisas Prod Nat, BR-21941902 Rio de Janeiro, BrazilUFRJ, Hosp Univ Clementino Fraga Filho, Fac Med, BR-21941913 Rio de Janeiro, BrazilUniversidade Federal de São Paulo UNIFESP, Ctr Interdisciplinar Terapia Genica, BR-04044010 São Paulo, BrazilUniversidade Federal de São Paulo UNIFESP, Ctr Interdisciplinar Terapia Genica, BR-04044010 São Paulo, BrazilCNPq: 500992/2008-8FAPERJ: E-26/110305/2007FAPERJ: E-26/110132/2007FAPERJ: E-26/100416/2007FAPERJ: E-22/102733/2008Web of Scienc