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The coronavirus disease 2019 (COVID-19) pandemic has reached an unprecedented level. There is a strong demand for diagnostic and serological supplies worldwide, making it necessary for countries to establish their own technologies to produce high-quality biomolecules. The two main viral antigens used for the diagnostics for severe acute respiratory syndrome coronavirus (SARS-CoV-2) are the structural proteins spike (S) protein and nucleocapsid (N) protein. The spike protein of SARS-CoV-2 is cleaved into S1 and S2, in which the S1 subunit has the receptor-binding domain (RBD), which induces the production of neutralizing antibodies, whereas nucleocapsid is an ideal target for viral antigen-based detection. In this study, we designed plasmids, pcDNA3.1/S1 and pcDNA3.1/N, and optimized their expression of the recombinant S1 and N proteins from SARS-CoV-2 in a mammalian system. The RBD was used as a control. The antigens were successfully purified from Expi293 cells, with high yields of the S1, N, and RBD proteins. The immunogenic abilities of these proteins were demonstrated in a mouse model. Further, enzyme-linked immunosorbent assays with human serum samples showed that the SARS-CoV-2 antigens are a suitable alternative for serological assays to identify patients infected with COVID-19.

espanolAntecedentes: varios estudios han evaluado el efecto de las enfermedades infecciosas y los protocolos de vacunacion durante el embarazo sobre los niveles de inmunoglobulina (Ig) de la leche materna, para comprender la proteccion que confiere la lactancia a los recien nacidos. El calostro es la principal fuente de IgA materna para el recien nacido. La IgA participa en los mecanismos de proteccion de la mucosa del recien nacido. En los seres humanos, la IgA tiene dos subclases con distribucion anatomica diferencial entre los compartimentos mucosos. Los niveles de IgA total en la leche materna varian despues de la estimulacion del antigeno y tienen afinidades diferenciales en funcion de la composicion quimica de los antigenos. Estudiamos el efecto de la estimulacion antigenica durante el embarazo sobre las concentraciones de subclases de IgA1 e IgA2 especificas en el calostro humano. Metodos: Analizamos datos de 113 mujeres en la Ciudad de Mexico y comparamos la cantidad de subclases de IgA en el calostro con tres antigenos: dos de protocolos de vacuna (toxoide tetanico y polisacaridos neumococicos) y lipopolisacarido, un antigeno ubicuo en el tracto gastrointestinal. Resultados: De acuerdo con los informes anteriores, mostramos que la IgA1 del calostro reconocia principalmente antigenos proteicos; en marcado contraste, la IgA2 se dirigio principalmente contra antigenos polisacaridos. Estos niveles aumentaron en mujeres que habian tenido contactos previos por vacunacion o infecciones durante el embarazo. Conclusiones: La interaccion de antigenos durante el embarazo aumento la cantidad de subclases de IgA especificas, dependiendo de la composicion quimica del antigeno. EnglishBackground: Several studies have evaluated the effect of infectious diseases and vaccine protocols during pregnancy on ma- ternal milk immunoglobulin (Ig) levels, to understand the protection conferred by lactation on newborns. Colostrum is the primary source of maternal IgA for the newborn. IgA participates in protection mechanisms in the neonate’s mucosa. In humans, IgA has two subclasses with differential anatomical distribution among mucosal compartments. Total IgA levels in maternal milk vary after antigen stimulation and have differential affinities in function of the chemical composition of the antigens. We studied the effect of antigenic stimulation during pregnancy on the concentrations of specific IgA1 and IgA2 subclasses in human colostrum. Methods: We analyzed data from 113 women in Mexico City and compared the amount of IgA subclasses in colostrum against three antigens: two from vaccine protocols (tetanus toxoid and pneumococcal polysaccharides) and lipo- polysaccharide, a ubiquitous antigen in the gastrointestinal tract. Results: In agreement with the previous reports, we showed that IgA1 from colostrum mainly recognized protein antigens; in sharp contrast, IgA2 was mostly directed against polysac- charide antigens. These levels increased in women who had previous contacts through vaccination or infections during preg- nancy. Conclusions: Antigen interaction during pregnancy increased the amount of specific IgA subclasses, depending on the chemical composition of the antigen. (REV INVEST CLIN. 2020;72(2):80-7)