A COVID-19 vaccine candidate composed of the SARS-CoV-2 RBD dimer and Neisseria meningitidis outer membrane vesicles.

SARS-CoV-2 infection is mediated by the interaction of the spike glycoprotein trimer via its receptor-binding domain (RBD) with the host's cellular receptor. Vaccines seek to block this interaction by eliciting neutralizing antibodies, most of which are directed toward the RBD. Many protein subunit vaccines require powerful adjuvants to generate a potent antibody response. Here, we report on the use of a SARS-CoV-2 dimeric recombinant RBD combined with Neisseria meningitidis outer membrane vesicles (OMVs), adsorbed on alum, as a promising COVID-19 vaccine candidate. This formulation induces a potent and neutralizing immune response in laboratory animals, which is higher than that of the dimeric RBD alone adsorbed on alum. Sera of people vaccinated with this vaccine candidate, named Soberana01, show a high inhibition level of the RBD-ACE2 interaction using RBD mutants corresponding to SARS-CoV-2 variants of concern and wild-type expressed using the phage display technology. To our knowledge, this is the first time that the immunostimulation effect of N. meningitidis OMVs is evaluated in vaccine candidates against SARS-CoV-2.

SARS-CoV-2 RBD-Tetanus Toxoid Conjugate Vaccine Induces a Strong Neutralizing Immunity in Preclinical Studies.

Controlling the global COVID-19 pandemic depends, among other measures, on developing preventive vaccines at an unprecedented pace. Vaccines approved for use and those in development intend to elicit neutralizing antibodies to block viral sites binding to the host's cellular receptors. Virus infection is mediated by the spike glycoprotein trimer on the virion surface via its receptor binding domain (RBD). Antibody response to this domain is an important outcome of immunization and correlates well with viral neutralization. Here, we show that macromolecular constructs with recombinant RBD conjugated to tetanus toxoid (TT) induce a potent immune response in laboratory animals. Some advantages of immunization with RBD-TT conjugates include a predominant IgG immune response due to affinity maturation and long-term specific B-memory cells. These result demonstrate the potential of the conjugate COVID-19 vaccine candidates and enable their advance to clinical evaluation under the name SOBERANA02, paving the way for other antiviral conjugate vaccines.

NMR line-fitting quantification of polysaccharide N-acylurea-based modification in glycoconjugates of Salmonella Typhi Vi polysaccharide.

The polysaccharides modification via carbodiimide reaction is one of the most applied methods for obtaining conjugated vaccines against Salmonella enterica. However, N-acylurea carbodiimide adduct generated in the process is a critical impurity in carbohydrate-based vaccines. A quantitative NMR method was developed for assessing the N-acylurea carbodiimide adduct impurity. The procedure was based on line-fitting facilities for processing the NMR signals on complex spectra. The method showed good linearity, accuracy and precision under inter-operator variation (relative standard deviation <5%). Copyright © 2017 John Wiley & Sons, Ltd.

Quantitative proton nuclear magnetic resonance evaluation and total assignment of the capsular polysaccharide Neisseria meningitidis serogroup X.

Neisseria meningitidis constitutes the main cause of meningococcal disease in infants. Serogroups A, B, C, W135, Y, and X have the higher incidence in young children and teenagers. The use of polyvalent conjugate carbohydrate-based vaccines has decreased the meningococcal infection around the world. Recently, the serogroup X has been found to be responsible of different outbreaks of meningococcal diseases, mainly in "Meningitis Belt" of Africa and the structure of the repetitive unit of the capsular polysaccharide has been confirmed through a monodimensional (13)C NMR study. No further characterization studies have been carried out, especially with the use of other nuclei. In this paper a novel method for quantification of the N. meningitidis serogroup X by proton qNMR is reported. Deep characterization of the serogroup X polysaccharide was also carried out by combination of correlation experiments involving (13)C, (1)H, and (31)P nuclei.

Introducción de un ELISA como ensayo alternativo en la determinación de la potencia de vacunas antitetánicas / Introduction of an ELISA as an alternative assay for potency testing of tetanus toxoid

Por más de medio siglo de uso, la vacunación con eltoxoide tetánico ha mostrado un elevado porcentaje de eficacia en la prevención del tétanos. Este trabajo pretende introducir un ensayo inmunoenzimático en fase sólida (ELISA) como método alternativo a la prueba deseroneutralización in vivo utilizada en la evaluación de la potencia de las vacunas antitetánicas. Se desarrolló un ELISA de tipo indirecto para la cuantificación de antitoxina tetánica en suero de curiel a partir de un estándar con 29 UI/mL, previamente calibrado. Se determinó la precisión, exactitud y linealidad del ensayo. Se analizó la correlación entre el ELISA y la prueba biológica mediante la evaluación de un total de 75 muestras de sueros por ambos métodos. Por último, seestudió la respuesta individual de un grupo de animales contra 15 lotes de toxoide tetánico. El ensayo demostró ser preciso y exacto, con imprecisiones inferiores al 20(por ciento) y valores de recuperación entre el 90–110(por ciento). Las desviaciones del paralelismo mostraron coeficientes de variación alrededor del 10(por ciento). El análisis por regresión lineal mostró una buena correlación entre el ELISA y el ensayo biológico (R2= 0,989). El método alternativo desarrollado probó ser una herramienta útil para la determinación de la potencia de vacunas antitetánicas a partir de la evaluación independiente de la respuesta de cada animal contra el toxoide tetánico. Los niveles de seroprotección alcanzados se encontraron entre el 83–100(por ciento)(AU)