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BackgroundOne of the most questioned issues about SARS-CoV2 immunity is how long does it last. Whether lasting differences exist between infection and vaccination boosted immunity is yet to be known. The answer to this question will determine key issues such as the reliability of individual and herd immunity or the need of sanitary restrictions or periodical revaccination. The aim of this study was to determine how long total anti SARS-CoV2 antibodies due to past infection persist in peripheral blood and whether sex, age or haematological features can influence their lasting. Material and MethodsA total of 2432 donations SARS-CoV-2 from 662 repeat donors from April 2020 to February 2021 were analysed. Donors were 69.7% males and their average age was 46. An automated chemilumiscence immunoassay for total antibodies recognizing N protein of SARS-CoV-2 in human serum and plasma was performed. Results and discussionIn 97.6% donors with follow-up, anti SARS-CoV-2 protein N total antibodies remained positive up to 46 weeks after first positive determination. Blood group was not related to antibody waning. Lower lymphocyte counts and higher neutrophils and as well higher seric IgA would help predict future negativization of antibodies. The vast majority of donors keep their total immunoglobulins anti SARS-CoV-2 positive for longer than 10 months. Ageing might have a protective effect against antibody waning but, given the small number of cases that become negative, more studies, or larger cohorts would be needed to confirm these facts.
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Background and objectivesCOVID-19 can either cause death or go unnoticed but antibodies will remain protecting us of SARS-CoV-2 reinfection for an uncertain time and to an uncertain extent. Our aim was to describe seroprevalence evolution from summer 2019 to autumn 2020 in Spain and to describe its relationship with age, blood group and haematological parameters. Materials and methodsSera and plasma from historical donation archives excluding convalescent were randomized and a total of 12,313 donations tested by a Chemiluminiscent analysis for anti SARS-CoV-2 N protein total immunoglobulins. Blood donors were 60.9% males, average age 46+/-13. Sex, age, blood group, blood cell counts and percentages and immunoglobulin concentrations were extracted from electronic recordings. ResultsA seroprevalence of 6.7% in blood donors was found by the end of the first wave. No differences by sex, age or blood group were found regarding antibodies. Leukocyte count (p=0.026), haematocrit (p<0.001) and haemoglobin (p<0.001) were lower in positive donations than in negative ones. Sex differences were present in neutrophils, leukocytes, haemoglobin and haematocrit as related to SARS-CoV-2 antibodies. ConclusionsSeroprevalence due to asymptomatic cases would resemble that of global population. Sex and age would not affect COVID-19 susceptibility but its severity. Gender differences related to COVID-19 in leukocytes, haemoglobin and haematocrit would be present in asymptomatic individuals. Further studies are needed to confirm these gender differences as they can help better understand the immune response to COVID-19, its pathogenesis and prognosis.
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BACKGROUND: The beta-galactosidase from Kluyveromyces lactis is a protein of outstanding biotechnological interest in the food industry and milk whey reutilization. However, due to its intracellular nature, its industrial production is limited by the high cost associated to extraction and downstream processing. The yeast-system is an attractive method for producing many heterologous proteins. The addition of a secretory signal in the recombinant protein is the method of choice to sort it out of the cell, although biotechnological success is not guaranteed. The cell wall acting as a molecular sieve to large molecules, culture conditions and structural determinants present in the protein, all have a decisive role in the overall process. Protein engineering, combining domains of related proteins, is an alternative to take into account when the task is difficult. In this work, we have constructed and analyzed two hybrid proteins from the beta-galactosidase of K. lactis, intracellular, and its Aspergillus niger homologue that is extracellular. In both, a heterologous signal peptide for secretion was also included at the N-terminus of the recombinant proteins. One of the hybrid proteins obtained has interesting properties for its biotechnological utilization. RESULTS: The highest levels of intracellular and extracellular beta-galactosidase were obtained when the segment corresponding to the five domain of K. lactis beta-galactosidase was replaced by the corresponding five domain of the A. niger beta-galactosidase. Taking into account that this replacement may affect other parameters related to the activity or the stability of the hybrid protein, a thoroughly study was performed. Both pH (6.5) and temperature (40 degrees C) for optimum activity differ from values obtained with the native proteins. The stability was higher than the corresponding to the beta-galactosidase of K. lactis and, unlike this, the activity of the hybrid protein was increased by the presence of Ni2+. The affinity for synthetic (ONPG) or natural (lactose) substrates was higher in the hybrid than in the native K. lactis beta-galactosidase. Finally, a structural-model of the hybrid protein was obtained by homology modelling and the experimentally determined properties of the protein were discussed in relation to it. CONCLUSION: A hybrid protein between K. lactis and A. niger beta-galactosidases was constructed that increases the yield of the protein released to the growth medium. Modifications introduced in the construction, besides to improve secretion, conferred to the protein biochemical characteristics of biotechnological interest.