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.

Background: Several studies have evaluated the effect of infectious diseases and vaccine protocols during pregnancy on maternal 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 lipopolysaccharide, 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 polysaccharide antigens. These levels increased in women who had previous contacts through vaccination or infections during pregnancy. Conclusions: Antigen interaction during pregnancy increased the amount of specific IgA subclasses, depending on the chemical composition of the antigen.

It is known that levels of the anti-apoptotic protein survivin are reduced during Murine norovirus MNV-1 and Feline calicivirus (FCV) infection as part of the apoptosis establishment required for virus release and propagation in the host. Recently, our group has reported that overexpression of survivin causes a reduction of FCV protein synthesis and viral progeny production, suggesting that survivin may affect early steps of the replicative cycle. Using immunofluorescence assays, we observed that overexpression of survivin, resulted in the reduction of FCV infection not only in transfected but also in the neighboring nontransfected CrFK cells, thus suggesting autocrine and paracrine protective effects. Cells treated with the supernatants collected from CrFK cells overexpressing survivin showed a reduction in FCV but not MNV-1 protein production and viral yield, suggesting that FCV binding and/or entry were specifically altered. The reduced ability of FCV to bind to the surface of the cells overexpressing survivin, or treated with the supernatants collected from these cells, correlate with the reduction in the cell surface of the FCV receptor, the feline junctional adhesion molecule (fJAM) 1, while no effect was observed in the cells transfected with the pAm-Cyan vector or in cells treated with the corresponding supernatants. Moreover, the overexpression of survivin affects neither Vaccinia virus (VACV) production in CrFK cells nor MNV-1 virus production in RAW 267.4 cells, indicating that the effect is specific for FCV. All of these results taken together indicate that cells that overexpress survivin, or cell treatment with the conditioned medium from these cells, results in the reduction of the fJAM-1 molecule and, therefore, a specific reduction in FCV entry and infection.

NK cells are contained in the ILC1 group; they are recognized for their antiviral and antitumor cytotoxic capacity; NK cells also participate in other immune response processes through cytokines secretion. However, the mechanisms that regulate these functions are poorly understood since NK cells are not as abundant as other lymphocytes, which has made them difficult to study. Using public databases, we identified that NK cells express mRNA encoding class I myosins, among which Myosin 1g and Myosin 1f are prominent. Therefore, this mini-review aims to generate a model of the probable participation of Myosin 1g and 1f in NK cells, based on information reported about the function of these myosins in other leukocytes.