Eliciting a single amino acid change by vaccination generates antibody protection against group 1 and group 2 influenza A viruses.

Broadly neutralizing antibodies (bnAbs) targeting the hemagglutinin (HA) stem of influenza A viruses (IAVs) tend to be effective against either group 1 or group 2 viral diversity. In rarer cases, intergroup protective bnAbs can be generated by human antibody paratopes that accommodate the conserved glycan differences between the group 1 and group 2 stems. We applied germline-engaging nanoparticle immunogens to elicit a class of cross-group bnAbs from physiological precursor frequency within a humanized mouse model. Cross-group protection depended on the presence of the human bnAb precursors within the B cell repertoire, and the vaccine-expanded antibodies enriched for an N55T substitution in the CDRH2 loop, a hallmark of the bnAb class. Structurally, this single mutation introduced a flexible fulcrum to accommodate glycosylation differences and could alone enable cross-group protection. Thus, broad IAV immunity can be expanded from the germline repertoire via minimal antigenic input and an exceptionally simple antibody development pathway.

Engaging an HIV vaccine target through the acquisition of low B cell affinity.

Low affinity is common for germline B cell receptors (BCR) seeding development of broadly neutralizing antibodies (bnAbs) that engage hypervariable viruses, including HIV. Antibody affinity selection is also non-homogenizing, insuring the survival of low affinity B cell clones. To explore whether this provides a natural window for expanding human B cell lineages against conserved vaccine targets, we deploy transgenic mice mimicking human antibody diversity and somatic hypermutation (SHM) and immunize with simple monomeric HIV glycoprotein envelope immunogens. We report an immunization regimen that focuses B cell memory upon the conserved CD4 binding site (CD4bs) through both conventional affinity maturation and reproducible expansion of low affinity BCR clones with public patterns in SHM. In the latter instance, SHM facilitates target acquisition by decreasing binding strength. This suggests that permissive B cell selection enables the discovery of antibody epitopes, in this case an HIV bnAb site.

New and safe formulation for scorpion immunotherapy: Comparative study between saponin and FCA adjuvants associated to attenuated venom.

Envenoming by scorpion is a major health problem in Maghreb regions as well as in several regions of the world. Immunotherapy is the only effective treatment for scorpion stings. The immune sera are obtained from hyper-immunized animals with a formulation of venom associated to Freund's Complete Adjuvant (FCA). This formulation seems to protect against several alterations in immunized animals leading to worsening of their health due to added toxicity of native venom and FCA adjuvant. This study aims to provide a more efficient and non-toxic alternative to this formulation. Two formulations of saponin or FCA associated to irradiated venom of Androctonus australis hector (Aah) were used to compare their safety and their efficiency to better enhance the antibody titers against toxic antigens. Both of these formulations were used in immunization schedule of three months. Blood samples were collected every week, cell count, myeloperoxydase (MPO) and eosinophil peroxidase (EPO) activities and specific antibody titers were evaluated. Four months after the last immunization, rabbits were challenged with increased doses of native Aah venom. Results showed that immunization with saponin formulation induced lower inflammatory cell activation as well as reduced MPO and EPO activities compared to that using FCA. The formulation of irradiated venom with saponin seems also to be more efficient in the activation of lymphocytes resulting in higher titers of specific IgG. The immunoprotective effect evaluation showed that the formulation using saponin seems to protected animals until 3 LD50 of native venom compared to that using FCA which protected only until 2 LD50. These results indicate that saponin formulation with irradiated antigen could be more efficient and safe immunizing preparation for the production of sera against scorpion envenomation.

Reactogenicity and safety assessment of an attenuated nanovaccine against scorpion envenomation: Preclinical study.

An attenuated nanovaccine (Nps - V∗) has been developed to protect humans from fatal scorpion envenomation in at-risk regions. This study was conducted to evaluate the toxicity and the local reactogenicity of the Nps - V∗ nanovaccine developed against Androctonus australis hector (Aah) venom. Assessment of the systemic inflammatory response and serum cytokine levels were evaluated in vaccinated mice with 100µg of irradiated Aah venom (V∗) encapsulated or not into polymeric calcium-alginate nanoparticles (Nps) and injected by subcutaneous (s.c) route. The local reactogenicity was evaluated by dermal Draize observations and skin tissue analysis at the injection site of vaccinated rabbits with 250 or 500µg of V∗-loaded into Nps. All animals gained weight and had normal food consumption during the study. Additionally, results showed that the nanoformulation Nps - V∗ did not cause clinical evidence of systemic toxicity in mice or rabbits, a transient edema/erythema at the injection site was only recorded as treatment-related reactogenicity. These results indicated a favorable safety profile for Nps - V∗ and supported its use in superior animal tests, then in a Phase 1 clinical trial.

Development and characterization of a new carrier for vaccine delivery based on calcium-alginate nanoparticles: Safe immunoprotective approach against scorpion envenoming.

To enhance humoral defense against diseases, vaccine formulation is routinely prepared to improve immune response. Studies in nanomaterials as a carrier of vaccine delivery are promising and interesting. In this study, attenuated Androctonus australis hector (Aah) venom and its toxic fraction were encapsulated into different formulations inside calcium-alginate nanoparticles (Ca-Alg Nps), and used as a vaccine delivery system against scorpion envenomation. Ca-Alg Nps were prepared by ionic gelation and characterized. An immunization schedule was undertaken in rabbits in order to study how Aah venom entrapped in Ca-Alg Nps might induce protective immunity. Results showed the influence of different parameters on the suitable nanoparticle formation. They also showed no toxicity of free Ca-Alg Nps and a different inflammatory profile depending on the nanovaccine formulations. More interestingly, evaluation of specific IgG titer and IgG1/IgG2a isotype balance revealed a protective effect with the nanoparticles encapsulating the attenuated antigens. Challenge up to 6 LD 50 of native venom, allowed to an important immunoprotection of all immunized rabbits, with no recorded death. Taken together and with respect to the properties of nanoparticles and high immunogenicity, calcium-alginate nanoparticles could be considered as a new promising adjuvant system and a vaccine delivery against scorpion envenomation.