Assessment of an in-house IgG ELISA targeting SARS-CoV-2 RBD: Applications in infected and vaccinated individuals

The study aimed to assess an in-house Spike Receptor Binding Domain Enzyme-Linked Immunosorbent Assay (RBD-ELISA) for detecting SARS-CoV-2 IgG antibodies in both infected and vaccinated individuals. Using the RBD recombinant protein, the assay demonstrated a sensitivity of 91%, specificity of 99.25%, and accuracy of 95.13%. Precision and reproducibility were highly consistent. The RBD-IgG-ELISA was able to detect 96.25% of Polymerase chain reaction (PCR) -confirmed cases for SARS-CoV-2 infection, demonstrating positive and negative predictive values of 99,18% and 91,69%, respectively. In an epidemiological survey, ELISA, lateral flow immunochromatographic assay (LFIA), and electrochemiluminescence immunoassay (ECLIA) exhibited diagnostic sensitivities of 68.29%, 63.41%, and 70.73%, respectively, along with specificities of 82.93%, 80.49%, and 80.49%, respectively. Agreement between RBD-IgG-ELISA/PCR was moderate (k index 0.512). However, good agreement between different assays (RBD-IgG ELISA/LFIA k index 0.875, RBD-IgG ELISA/ECLIA k index 0.901). Test performance on individuals' samples were inferior due to seroconversion time and chronicity. The IgG-RBD-ELISA assay demonstrated its effectiveness in monitoring antibody levels among healthcare professionals, revealing significant differences both before and after the administration of the third vaccine dose, with heightened protection levels observed following the third dose in five Coronavirus disease (COVID-19) vaccine regimens. In conclusion, the RBD-IgG ELISA exhibits high reproducibility, specificity, and sensitivity, making it a suitable assay for serosurveillance and for obtaining information about COVID-19 infections or vaccinations.

Production of Recombinant Zika Virus Envelope Protein by Airlift Bioreactor as a New Subunit Vaccine Platform

The Zika Virus (ZIKV) is an emerging arbovirus of great public health concern, particularly in the Americas after its last outbreak in 2015. There are still major challenges regarding disease control, and there is no ZIKV vaccine currently approved for human use. Among many different vaccine platforms currently under study, the recombinant envelope protein from Zika Virus (rEZIKV) constitutes an alternative option for vaccine development and has great potential for monitoring ZIKV infection and antibody response. This study describes a method to obtain a bioactive and functional rEZIKV using an E. coli expression system, with the aid of a 5-L airlift bioreactor and following an automated fast protein liquid chromatography (FPLC) protocol, capable of obtaining high yields of approximately 20 mg of recombinant protein per liter of bacterium cultures. The purified rEZIKV presented preserved antigenicity and immunogenicity. Our results show that the use of an airlift bioreactor for the production of rEZIKV is ideal for establishing protocols and further research on ZIKV vaccines bioprocess, representing a promising system for the production of a ZIKV envelope recombinant protein-based vaccine candidate.

RBD and Spike DNA-Based Immunization in Rabbits Elicited IgG Avidity Maturation and High Neutralizing Antibody Responses against SARS-CoV-2

Neutralizing antibodies (nAbs) are a critical part of coronavirus disease 2019 (COVID-19) research as they are used to gain insight into the immune response to severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) infections. Among the technologies available for generating nAbs, DNA-based immunization methods are an alternative to conventional protocols. In this pilot study, we investigated whether DNA-based immunization by needle injection in rabbits was a viable approach to produce a functional antibody response. We demonstrated that three doses of DNA plasmid carrying the gene encoding the full-length spike protein (S) or the receptor binding domain (RBD) of SARS-CoV-2 induced a time-dependent increase in IgG antibody avidity maturation. Moreover, the IgG antibodies displayed high cross neutralization by live SARS-CoV-2 and pseudoviruses neutralization assays. Thus, we established a simple, low cost and feasible DNA-based immunization protocol in rabbits that elicited high IgG avidity maturation and nAbs production against SARS-CoV-2, highlighting the importance of DNA-based platforms for developing new immunization strategies against SARS-CoV-2 and future emerging epidemics.

Chitosan: Applications in Drug Delivery System

Chitin and chitosan have unique structures with significant functional groups carrying useful chemical capabilities. Chitin and chitosan are acknowledged as novel biomaterials with advantageous biocompatibility and biodegradability. Chitosan is a polysaccharide that is made from chitin. There have been several attempts to employ this biopolymer in the biomedical area. This material's application in the production of artificial skin, drug targeting, and other areas is explored. The most prevalent strategies for recovering chitin from sea organisms are described and various pharmacological and biological uses are discussed. This review article targets drug delivery with the help of chitosan derived nanomaterial. The drug delivery system applications through nonmaterial have encountered a considerable role in the pharmaceutical, medical, biological, and other sectors in recent years. Nanomaterials have advanced applications as novel drug delivery systems in many fields, especially in industry, biology, and medicine. In the biomedical and pharmaceutical arena, the natural polymer-based nanoparticulate method has now been widely studied as particulate vehicles. By mixing alginate with other biopolymers, by immobilizing specific molecules such as sugar molecules and peptides by chemical or physical cross-linking, different properties and structures such as biodegradability, gelling properties, mechanical strength, and cell affinity can be obtained. Owing to their inherent ability to deliver both hydrophilic and hydrophobic drug molecules, increase stability, decrease toxicity, and enhance commonly formulated medications, these particles are now widely used in imaging and molecular diagnostics, cosmetics, household chemicals, sunscreens, radiation safety, and novel drug delivery.

Assessment of avidity related to IgG subclasses in SARS-CoV-2 Brazilian infected patients

SARS-CoV-2 is considered a global emergency, resulting in an exacerbated crisis in the health public in the world. Although there are advances in vaccine development, it is still limited for many countries. On the other hand, an immunological response that mediates protective immunity or indicates that predict disease outcome in SARS-CoV-2 infection remains undefined. This work aimed to assess the antibody levels, avidity, and subclasses of IgG to RBD protein, in symptomatic patients with severe and mild forms of COVID-19 in Brazil using an adapted in-house RBD-IgG ELISA. The RBD IgG-ELISA showed 100% of specificity and 94.3% of sensibility on detecting antibodies in the sera of hospitalized patients. Patients who presented severe COVID-19 had higher anti-RBD IgG levels compared to patients with mild disease. Additionally, most patients analyzed displayed low antibody avidity, with 64.4% of the samples of patients who recovered from the disease and 84.6% of those who died in this avidity range. Our data also reveals an increase of IgG1 and IgG3 levels since the 8th day after symptoms onset, while IgG4 levels maintained less detectable during the study period. Surprisingly, patients who died during 8–14 and 15–21 days also showed higher anti-RBD IgG4 levels in comparison with the recovered (P < 0.05), suggesting that some life-threatening patients can elicit IgG4 to RBD antibody response in the first weeks of symptoms onset. Our findings constitute the effort to clarify IgG antibodies' kinetics, avidity, and subclasses against SARS-CoV-2 RBD in symptomatic patients with COVID-19 in Brazil, highlighting the importance of IgG antibody avidity in association with IgG4 detection as tool laboratory in the follow-up of hospitalized patients with more significant potential for life-threatening.

Protective efficacy of bacterial membranes containing surface-exposed BM95 antigenic peptides for the control of cattle tick infestations

The Rhipicephalus (Boophilus) microplus BM86 and BM95 glycoproteins are homologous proteins that protect cattle against tick infestations. In this study, we demonstrated that the recombinant chimeric protein comprising tick BM95 immunogenic peptides fused to the A. marginale MSP1a N-terminal region for presentation on the Escherichia coli membrane was protective against R. microplus infestations in rabbits. This system provides a novel and simple approach for the production of tick protective antigens by surface display of antigenic protein chimera on live E. coli and suggests the possibility of using recombinant bacterial membrane fractions for vaccination against cattle tick infestations.