Simplification of sample collection by using eluates from dried blood spots (DBS) obtained by finger prick == The cost per sample of serological assays is an important aspect concerning large-scale public health actions, especially in low-income countries. 95% sensitivity for 11+ days after symptoms onset. We further showed that dried blood spots collected by finger pricking on simple test strips could replace conventional plasma/serum samples. A cost Loganic acid estimate was performed and revealed a final retail price in the range of one US dollar, reflecting the low cost of the ELISA test platform and the elimination of the need for venous blood sampling and refrigerated sample handling in clinical laboratories. The presented workflow can be completed in 4 months from first antigen expression to final test validation. It can be applied to other pathogens and in future pandemics, facilitating reliable and affordable seroepidemiological surveillance also in remote areas and in low-income countries. Keywords:Recombinant antigen production in mammalian cells, Purification of SARS-COV-2 spike protein, Serological test development, Detection of antibodies elicited by contamination or vaccination, Dried blood spot for diagnostic testing, COVID-19 == Graphical Abstract == == 1. Introduction == Several authors have been predicting that this occurrence of epidemics and the emergence of new infectious diseases will become more frequent and harder to control due to several reasons, such as urbanization, climate change, intense travelling, and deficient health systems[26],[7],[9]. In this context, lessons learnt from COVID-19 pandemic should be a starting point to contribute for a better preparedness for future pandemics. One of the challenges in early phases of a pandemic is related to the availability of reliable and cost-effective diagnostic assessments, as it happened for COVID-19. The lack of diagnostic tools hinders epidemiological surveillance and understanding of pandemic dynamics, hampering decisions on public health policies for pandemic control. Loganic acid This holds more pronouncedly true in lower income countries. Serological assessments detect antibodies generated Loganic acid by contamination and vaccination. The most popular assessments detect immunoglobulins of the G class (IgG), which upon primary infection or primary vaccination take approximately 2 weeks since the contact with the pathogen (or with the vaccine antigen) to be produced by the organism. Early on in a pandemic, accurate antibody assessments are essential to study prevalence, to understand the frequency of asymptomatic cases and to monitor pathogen spread. During vaccine development efforts, reliable serological assays are required for SARP2 the analysis of samples from pre-clinical and clinical trials. Furthermore, they are important for investigation of humoral immune response in different segments of the population, evaluation of durability of immunity, investigation of different vaccination schedules in subjects with or without antibodies induced Loganic acid by previous infection, comparison of homologous and heterologous vaccination strategies, among other types of studies that are crucial to provide the seroepidemiological data needed to support public health decisions and immunization policies. The COVID-19 pandemic brought an unprecedented global health crisis, causing approximately 500 million cases and 6 million deaths within approximately 2 years since the declaration of the Covid-19 pandemic by the World Health Organization (WHO) in March 2020[20]. In most regions of the world, the number of infected individuals needing medical treatment exceeded hospitals capacity, and healthcare personnel became overwhelmed by the excess of working hours and by adverse mental health outcomes. In addition to this brutal scenario, the elevated human-to-human contagious rate obliged a severe restriction of social life including, in some cases, complete lockdown except for essential activities. As a Loganic acid result, this situation led to economic disruption in many countries experiencing several months of partial or complete lockdown. In this scenario, public health policies need to be guided by scientifically sound data, and accurate diagnostic testing is one important tool in this regard. The structural spike (S) protein of coronaviruses is known to be a major target for neutralizing antibodies, thus making it a key antigen for the development of specific and sensitive sero-diagnostic assessments. S protein contains the receptor binding domain name in its S1 subunit and is also responsible for fusion to the cell membrane through its S2 subunit[35]..