Statistical analysis == Data normality was verified by the Shapiro-Wilk test (P>0.05). as well as by quantification of RNA load using reverse transcriptionquantitative real time polymerase chain reaction. Once viral inactivation was confirmed, cell culture supernatants were concentrated and purified. In addition, an aliquot inactivated by BPL was also subjected to viral protein extraction (VPE). The different antigens were KDU691 prepared using a previously developed microemulsion as adjuvant, and were administered in a four-dose immunization protocol. Antibody production was comparatively evaluated by ELISA and Plaque Reduction Neutralization Assessments (PRNT). All immunogens evaluated showed some level of IgG anti-SARS-CoV-2 antibodies in the ELISA assay, with the highest levels presented by the group immunized with FDE-inactivated viral antigen. In the PRNT results, except for VPE-antigen, all other immunogens evaluated induced some level of neutralizing anti-SARS-CoV-2 antibodies, and the FDE-antigen stood out again with the most expressive values. Taken together, the present work shows that FDE can be an efficient and affordable alternative to BPL for the production of inactivated SARS-CoV-2 viral antigen. Keywords:SARS-CoV-2, Inactivated computer virus, RT-qPCR, ELISA, PRNT50 == Graphical Abstract KDU691 == == 1. Introduction == Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged in December of 2019 in Hubei Province of China and rapidly spread around the world, causing a global pandemic of coronavirus disease 19 (COVID-19) that is still ongoing (Wang et al., 2021). Contamination by SARS-CoV-2 can be asymptomatic, present moderate to moderate cold-like manifestations or can progress to acute respiratory distress syndrome, coagulation disorders and a range of other symptoms that ultimately may lead to death (Tsai et al., 2021). Due to the amazing infectivity of SARS-CoV-2, mass vaccination is usually shown to be the main prophylactic strategy to contain the pandemic (Dai and Gao, 2021). However, there are groups of immunosuppressed individuals unresponsive to active vaccination, such that viral neutralization by passive KDU691 immunization through transferred antibodies (Ledford, 2021), monoclonal preparations (Suryadevara et al., 2021), hyperimmune heterologous plasma (Pan et al., 2020,da Costa Camila et al., 2021,Vanhove et al., 2021), or plasma from convalescent donors (Piechotta et al., 2020,Chai et al., 2020,Focosi and Franchini, 2021) have been seen as a rational complementary therapeutic approach. To address both the induction of antibodies for passive immunization and vaccination, the use of chemically inactivated computer virus is a traditionally used alternative (Delrue et al., 2009,Furuya, 2012). Viral inactivation for antibody induction purposes must be concerned with safety, LPA receptor 1 antibody completely preventing virus infectivity; and with preserving viral immunogenicity, to induce a strong immune response. The optimal conditions for viral inactivation can vary with computer virus type, strain, concentration, incubation time, among other variables, implying that the KDU691 procedure must be carefully defined to achieve a functional product (Delrue et al., 2012,Herrera-Rodriguez et al., 2019). -propiolactone (BPL) is one of the most widely used brokers for viral inactivation and has traditionally been used in several vaccine preparations (Sabbaghi et al., 2019), including Corona Vac/Sinovac Biotech (formerly picovacc), one of the first authorized COVID-19 vaccines for “emergency use” in Brazil, China, and Indonesia (Gao et al., 2020,Fortner and Schumacher, 2021). However, in the rush of a race to obtain vaccines and therapeutics to fight COVID-19, the supply of BPL was compromised in some countries, including Brazil, and its price was inflated to even more prohibitive values, especially for countries in development. On the other hand, fixation of infectious samples using formaldehyde (FDE) is usually a well-established protocol in electron microscopy for transforming active viruses into a non-infectious but structurally intact form in order to allow a proper diagnosis based on morphology (Mller et al., 2015). Although not unanimous for all those viruses, many FDE-inactivated vaccines work well and protect against disease in the challenge (Bell et al., 1994,Furesz et al., 1995,Choi et al., 2003,Samina et al., 2005,Kistner et al., 2007,Heinz et al., 2008). Cellular ultrastructure preservation by glutaraldehyde (GDE) is also well documented since the.
