Safety and immunogenicity of anti-SARS CoV-2 vaccine SOBERANA 02 in homologous or heterologous scheme: Open label phase I and phase IIa clinical trials.

BACKGROUND: SOBERANA 02 is a COVID-19 vaccine based on SARS-CoV-2 recombinant RBD conjugated to tetanus toxoid (TT). SOBERANA Plus antigen is dimeric-RBD. Here we report safety and immunogenicity from phase I and IIa clinical trials using two-doses of SOBERANA 02 and three-doses (homologous) or heterologous (with SOBERANA Plus) protocols. METHOD: We performed an open-label, sequential and adaptive phase I to evaluate safety and explore the immunogenicity of SOBERANA 02 in two formulations (15 or 25 µg RBD-conjugated to 20 µg of TT) in 40 subjects, 19-59-years-old. Phase IIa was open-label including 100 volunteers 19-80-years, receiving two doses of SOBERANA 02-25 µg. In both trials, half of volunteers were selected to receive a third dose of the corresponding SOBERANA 02 and half received a heterologous dose of SOBERANA Plus. Primary outcome was safety. The secondary outcome was immunogenicity evaluated by anti-RBD IgG ELISA, molecular neutralization of RBD:hACE2 interaction, live-virus-neutralization and specific T-cells response. RESULTS: The most frequent adverse event (AE) was local pain, other AEs had frequencies ≤ 5%. No serious related-AEs were reported. Phase IIa confirmed the safety in 60 to 80-years-old subjects. In phase-I SOBERANA 02-25 µg elicited higher immune response than SOBERANA 02-15 µg and progressed to phase IIa. Phase IIa results confirmed the immunogenicity of SOBERANA 02-25 µg even in 60-80-years. Two doses of SOBERANA02-25 µg elicited an immune response similar to that of the Cuban Convalescent Serum Panel and it was higher after the homologous and heterologous third doses. The heterologous scheme showed a higher immunological response. Anti-RBD IgG neutralized the delta variant in molecular assay, with a 2.5-fold reduction compared to D614G neutralization. CONCLUSIONS: SOBERANA 02 was safe and immunogenic in persons aged 19-80 years, eliciting neutralizing antibodies and specific T-cell response. Highest immune responses were obtained in the heterologous three doses protocol. TRIAL REGISTRY: https://rpcec.sld.cu/trials/RPCEC00000340, https://rpcec.sld.cu/trials/RPCEC00000347.

Validación y aplicación de un ELISA para la cuantificación de anticuerpos IgG contra polisacárido capsular Vi de Salmonella Typhi / Validation and application of an ELISA for the quantification of IgG antibodies against Salmonella Typhi Vi capsular polysaccharide

Como parte de las etapas de investigación y desarrollo de un candidato vacunal conjugado contra Salmonella Typhi, se desarrolló un ELISA indirecto para la cuantificación de anticuerpos IgG contra el polisacárido Vi de esta bacteria. En este trabajo se presentan los resultados del proceso de validación, en el que se determinaron el intervalo y linealidad de la curva, la precisión intra e interensayo, la exactitud, la especificidad, el límite de detección y la robustez. La curva de calibración, generada con un suero estándar interno, presentó un buen ajuste a una función polinómica y un intervalo entre las diluciones 1/100 y 1/3200. Los coeficientes de variación en los ensayos de precisión y robustez y los porcentajes de recobrado estuvieron en los intervalos establecidos para cada uno (≤10 por ciento, ≤20 por ciento y 90-110 por ciento respectivamente). El ensayo presentó una especificidad óptima, obteniéndose señales de DO superiores a 1,3 para sueros positivos contra Vi y bajas para sueros contra antígenos no relacionados. Los resultados avalan el empleo de este ELISA cuantitativo en ensayos de inmunogenicidad para la liberación de lotes de conjugados de Vi. Igualmente, sustentan su uso para la evaluación de la inmunogenicidad de formulaciones de polisacárido Vi y conjugados de polisacárido Vi a proteínas en fases de investigación y desarrollo(AU)

An indirect ELISA for the quantification of IgG antibodies against the Vi polysaccharide of this bacteria was developed as a part of the stages of Research and Development of a conjugate vaccinal candidate against Salmonella Typhi. The results of the validation process are presented in this paper, in which the interval and linearity of the curve, the intra- and inter-assay precision, accuracy, specificity, limit of detection and robustness were determined. The calibration curve generated with an internal standard serum provided a good fit to a polynomial function and an interval between 1/100 and 1/3200 dilutions. The coefficients of variation in the precision and robustness tests and the percentages of recovery were in intervals established for each one (≤10 percent, ≤20 percent and 90-110 percent, respectively). The assay presented an optimal specificity, obtaining OD signals above 1.3 for positive sera against Vi and low for sera against unrelated antigens. The results support the use of this quantitative ELISA in immunogenicity assays for batch release of Vi conjugates. Likewise, they support their use for the immunogenicity evaluation of Vi polysaccharide formulations and Vi polysaccharide conjugates to proteins in phases of research and development(AU)