Differential V2-directed Antibody Responses in Non-human Primates Infected with SHIVs or Immunized with Diverse HIV Vaccines

V2p and V2i antibodies (Abs) that are specific for epitopes in the V1V2 region of the HIV gp120 envelope (Env) do not effectively neutralize HIV but mediate Fc-dependent anti-viral activities that have been correlated with protection from, or control of HIV, SIV and SHIV infection. Here, we describe a novel molecular toolbox that allows the discrimination of antigenically and functionally distinct polyclonal V2 Ab responses. We identified different patterns of V2 Ab induction by SHIV infection and three separate vaccine regimens that will aid in fine tuning an optimized immunization protocol for inducing V2p and V2i Abs. We observed no, or weak and sporadic V2p and V2i Abs in non-vaccinated Tier 1 and Tier 2 SHIV-infected NHPs, but in contrast, strong V2p and/or V2i Ab responses after immunization with a V2-targeting vaccine protocol using a prime/boost regimen with gp120 DNA and a V1V2-scaffold protein. The V2-targeting vaccine protocol is superior to both natural infection and to immunization with whole Env constructs for inducing functional V2p- and V2i-specific responses. Strikingly, levels of V2-directed Abs correlated inversely with Abs specific for gp120 and peptides of V3 and C5. These data demonstrate that a V1V2-targeting vaccine have advantages over the imprecise targeting of SIV/SHIV infections and of whole Env-based immunization regimens for inducing a more focused functional V2p- and V2i-specific Ab response.

Production of a Plasma Derived Universal Antivenom against All Elapid Neurotoxic Snake Venoms

Snakebite envenoming has killed about 138000 people and maimed 400,000 victims annually. WHO has designated this medical problem as one of the most neglected tropical diseases for which effective, affordable antivenoms (AVs) are urgently needed. Production of potent AV against neurotoxic venoms was difficult and was thought to be due to the low immunogenicity of the postsynaptic neurotoxins (PSNT) which cause death in the victims. However, it was showed that the use of ineffective adjuvant in the immunization of horse was the root cause. The highly effective Freund adjuvant (FA) causes severe local reactions and could not be used. A novel immunization protocol termed ‘low dose low volume multi-site’ was tested and shown to obliterate the local side effect and allow for the safe use of FA in horse. The immunization protocol led to the production of 7 highly potent monovalent AVs, and 2 potent polyvalent AVs, one against 4 neurotoxic venoms and another against 3 hematotoxic venoms. These AVs allow the treatment of snakebite victims without the need to identify the culprit snakes. Furthermore, we have tested a novel immunization strategy using ‘Diverse toxin repertoire’ of 12 Asian elapid toxin fractions. The resulting antiserum effectively neutralized at least 36 elapid venoms of 28 species encompassing 10 genera and from 20 countries on 4 continents, and most likely all the elapid neurotoxic snake venoms. These results indicate that effective universal antivenom against all elapid neurotoxic venoms of the world can be produced and save numerous lives.

A Quest for a Universal Plasma-Derived Antivenom Against All Elapid Neurotoxic Snake Venoms

This review describes the research aimed at the development of universal antivenom against elapid neurotoxic snake venoms. The antivenoms produced in Thailand in the 1980s were of low potency, especially against the elapid venoms. This was thought to be due to the low immunogenicity of the α-neurotoxins, which are the most lethal toxins in these venoms. Comparisons of various α-neurotoxin conjugates and polymers, and also different immunological adjuvants, showed that the adjuvant used is the major determinant in the antibody response in horses. The potent Freund’s adjuvant was not used due to its severe local side-effect in horses. Therefore, a novel immunization protocol termed ‘low dose, low volume multi-site’ was developed for use in horses. This immunization protocol has led to the production of highly potent monospecific antivenoms against several elapid and viperid venoms, and two potent polyspecific antivenoms, one against 4 neurotoxic and another against 3 hematotoxic venoms. The immunization protocol has also led to other improvements in antivenom production including: several fold increases in antiserum potency, a reduction in the time required to reach therapeutically useful antibody titers, a 90% reduction in the amount of venom used, and 100% of the horses responding to the immunization program. This development is partly responsible for significant decrease in the Thailand’s annual snakebite death toll from a few dozens to mostly nil in recent years. Finally, a simple and novel immunization strategy, using a ‘diverse toxin repertoire’ composed of numerous elapid toxin fractions as immunogen, was proposed and tested. This immunization procedure has resulted in the successful production of a widely paraspecific antiserum against at least 36 neurotoxic venoms of 28 species encompassing 10 genera and from 20 countries on four continents, and possibly against all elapid venoms with α-neurotoxins as the lethal toxins. These results indicate that, with optimizations of the composition of the ‘diverse toxin repertoire’, the immunization scheme and antibody fractionation to increase the antivenom neutralizing potency, an effective universal antivenom against the neurotoxic elapid snakes of the world can be produced.

Self-Assembled Cationic-Covered Nanoemulsion as A Novel Biocompatible Immunoadjuvant for Antiserum Production Against Tityus serrulatus Scorpion Venom

This study assesses the efficacy of different nanoemulsion formulations as new and innovative adjuvants for improving the in vivo immunization against the Tityus serrulatus scorpion venom. Nanoemulsions were designed testing key-variables such as surfactants, co-solvents, and the influence of the temperature, which would be able to induce the phase transition from a liquid crystal to a stable nanoemulsion, assessed for four months. Additionally, cationic-covered nanoemulsion with hyper-branched poly(ethyleneimine) was prepared and its performance was compared to the non-cationic ones. The physicochemical properties of the selected nanoemulsions and the interactions among their involved formulation compounds were carefully monitored. The cytotoxicity studies in murine macrophages (RAW 264.7) and red blood cells were used to compare different formulations. Moreover, the performance of the nanoemulsion systems as biocompatible adjuvants was evaluated using mice immunization protocol. The FTIR shifts and the zeta potential changes (from −18.3 ± 1.0 to + 8.4 ± 1.4) corroborated with the expected supramolecular anchoring of venom proteins on the surface of the nanoemulsion droplets. Cell culture assays demonstrated the non-toxicity of the formulations at concentrations less than 1.0 mg/mL, which were able to inhibit the hemolytic effect of the scorpion venom. The cationic-covered nanoemulsion has shown superior adjuvant activity, revealing the highest IgG titer in the immunized animals compared to both the non-cationic counterpart and the traditional aluminum adjuvant. In this approach, we demonstrate the incredible potential application of nanoemulsions as adjuvants, using a nanotechnology platform for antigen delivery system on immune cells. Additionally, the functionalization with hyper-branched poly(ethyleneimine) enhances this recognition and improves its action in immunization.

Potent Anti-hepatitis C Virus (HCV) T Cell Immune Responses Induced in Mice Vaccinated with DNA-Launched RNA Replicons and Modified Vaccinia Virus Ankara-HCV

ABSTRACTHepatitis C is a liver disease caused by the hepatitis C virus (HCV) affecting 71 million people worldwide with no licensed vaccines that prevent infection. Here, we have generated four novel alphavirus-based DNA-launched self-amplifying RNA replicon (DREP) vaccines expressing either structural core-E1-E2 or nonstructural p7-NS2-NS3 HCV proteins of genotype 1a placed under the control of an alphavirus promoter, with or without an alphaviral translational enhancer (grouped as DREP-HCV or DREP-e-HCV, respectively). DREP vectors are known to induce cross-priming and further stimulation of immune responses through apoptosis, and here we demonstrate that they efficiently trigger apoptosis-related proteins in transfected cells. Immunization of mice with the DREP vaccines as the priming immunization followed by a heterologous boost with a recombinant modified vaccinia virus Ankara (MVA) vector expressing the nearly full-length genome of HCV (MVA-HCV) induced potent and long-lasting HCV-specific CD4+and CD8+T cell immune responses that were significantly stronger than those of a homologous MVA-HCV prime/boost immunization, with the DREP-e-HCV/MVA-HCV combination the most immunogenic regimen. HCV-specific CD4+and CD8+T cell responses were highly polyfunctional, had an effector memory phenotype, and were mainly directed against E1-E2 and NS2-NS3, respectively. Additionally, DREP/MVA-HCV immunization regimens induced higher antibody levels against HCV E2 protein than homologous MVA-HCV immunization. Collectively, these results provided an immunization protocol against HCV by inducing high levels of HCV-specific T cell responses as well as humoral responses. These findings reinforce the combined use of DREP-based vectors and MVA-HCV as promising prophylactic and therapeutic vaccines against HCV.IMPORTANCEHCV represents a global health problem as more than 71 million people are chronically infected worldwide. Direct-acting antiviral agents can cure HCV infection in most patients, but due to the high cost of these agents and the emergence of resistant mutants, they do not represent a feasible and affordable strategy to eradicate the virus. Therefore, a vaccine is an urgent goal that requires efforts to understand the correlates of protection for HCV clearance. Here, we describe for the first time the generation of novel vaccines against HCV based on alphavirus DNA replicons expressing HCV antigens. We demonstrate that potent T cell immune responses, as well as humoral immune responses, against HCV can be achieved in mice by using a combined heterologous prime/boost immunization protocol consisting of the administration of alphavirus replicon DNA vectors as the priming immunization followed by a boost with a recombinant modified vaccinia virus Ankara vector expressing HCV antigens.

Application of the 3R Concept in the Production of European Antiviperinum on Horses – Multisite, Low Volumes Immunization Protocol and Elisa

During time, both professionals and general public became aware of the importance of animal welfare. This term not only covers endangered wild animal species, animals used in food industry, pets and experimental animals, but also animals used in production of biologics. The implementation of the 3R concept (Replacement, Reduction and Refinement) is especially important in this type of production. In this article, we describe for the first time the low dose, low volume and multi-site immunization protocol, as well as appropriate ELISA we developed for production of European anti-viper (V. ammodytes, long horned) antivenom in horses, which can help to significantly improve the welfare of the used animals.