Persistence of IgG COVID-19 antibodies: A longitudinal analysis.

Background and aim: The kinetics of antibody production in response to coronavirus disease 2019 (COVID-19) infection is not well-defined yet. This study aimed to evaluate the antibody responses to SARS-CoV-2 and its dynamics during 9-months in a cohort of patients infected during the first phase of the pandemic. As a secondary aim, it was intended to evaluate the factors associated with different concentrations of IgG antibodies. Methods: A prospective cohort study was conducted from June 2020 to January 2021. This study recruited a convenience sample of adult individuals who where recently diagnosed with COVID-19 and were living in mainland Portugal. A total of 1,695 blood samples were collected from 585 recovered COVID-19 patients up to 9 months after SARS-CoV-2 acute infection. A blood sample was collected at baseline and three, 6 and 9 months after SARS-CoV-2 acute infection to assess the concentration of IgG antibody against SARS-CoV-2. Results: The positivity rate of IgG reached 77.7% in the first 3 months after symptom onset. The IgG persists at all subsequent follow-up time-points, which was 87.7 and 89.2% in the 6th and 9th months after symptom onset, respectively. Three distinct kinetics of antibody response were found within the 9 months after infection. Kinetic 1 (K1) was characterized by a constant low IgG antibody concentration kinetic (group size: 65.2%); kinetic 2 (K2), composed by constant moderate IgG kinetic (group size: 27.5%) and kinetic 3 (K3) characterized by higher IgG kinetic (group size: 7.3%). People with ≥56 years old (OR: 3.33; CI 95%: [1.64; 6.67]; p-value: 0.001) and symptomatic COVID-19 (OR: 2.08; CI 95%: [1.08; 4.00]; p-value: 0.031) had higher odds of a "Moderate IgG kinetic." No significant association were found regarding the "Higher IgG kinetic." Conclusion: Our results demonstrate a lasting anti-spike (anti-S) IgG antibody response at least 9 months after infection in the majority of patients with COVID-19. Younger participants with asymptomatic disease have lower IgG antibody positivity and possibly more susceptible to reinfection. This information contributes to expanding knowledge of SARS-CoV-2 immune response and has direct implications in the adoption of preventive strategies and public health policies.

Persistence of IgG COVID-19 antibodies: A longitudinal analysis

Background and aim The kinetics of antibody production in response to coronavirus disease 2019 (COVID-19) infection is not well-defined yet. This study aimed to evaluate the antibody responses to SARS-CoV-2 and its dynamics during 9-months in a cohort of patients infected during the first phase of the pandemic. As a secondary aim, it was intended to evaluate the factors associated with different concentrations of IgG antibodies. Methods A prospective cohort study was conducted from June 2020 to January 2021. This study recruited a convenience sample of adult individuals who where recently diagnosed with COVID-19 and were living in mainland Portugal. A total of 1,695 blood samples were collected from 585 recovered COVID-19 patients up to 9 months after SARS-CoV-2 acute infection. A blood sample was collected at baseline and three, 6 and 9 months after SARS-CoV-2 acute infection to assess the concentration of IgG antibody against SARS-CoV-2. Results The positivity rate of IgG reached 77.7% in the first 3 months after symptom onset. The IgG persists at all subsequent follow-up time-points, which was 87.7 and 89.2% in the 6th and 9th months after symptom onset, respectively. Three distinct kinetics of antibody response were found within the 9 months after infection. Kinetic 1 (K1) was characterized by a constant low IgG antibody concentration kinetic (group size: 65.2%);kinetic 2 (K2), composed by constant moderate IgG kinetic (group size: 27.5%) and kinetic 3 (K3) characterized by higher IgG kinetic (group size: 7.3%). People with ≥56 years old (OR: 3.33;CI 95%: [1.64;6.67];p-value: 0.001) and symptomatic COVID-19 (OR: 2.08;CI 95%: [1.08;4.00];p-value: 0.031) had higher odds of a "Moderate IgG kinetic.” No significant association were found regarding the "Higher IgG kinetic.” Conclusion Our results demonstrate a lasting anti-spike (anti-S) IgG antibody response at least 9 months after infection in the majority of patients with COVID-19. Younger participants with asymptomatic disease have lower IgG antibody positivity and possibly more susceptible to reinfection. This information contributes to expanding knowledge of SARS-CoV-2 immune response and has direct implications in the adoption of preventive strategies and public health policies.

SARS-CoV-2 Antibody Prevalence in the Portuguese Municipality of Vila Nova de Gaia after the First Wave of the Pandemic.

INTRODUCTION: Assessment of SARS-CoV-2 seroprevalence may detect the real spread of the virus because antibody data can provide a long-lasting measure of infection. Existing serological studies in Portugal have tested new serology methods, albeit with small sample sizes and a lack the focus on geographical regions with a high rate of infection cases. The aim of this study was to estimate the serological prevalence of SARS-CoV-2 in Vila Nova de Gaia, the most populous municipality in the north of Portugal and one of those most affected during the first pandemic wave. MATERIAL AND METHODS: A cross-sectional observational study was conducted between June 23rd and July 17th, 2020. Included in the cohort were 18- to 74-year-old men and women living in the municipality of Vila Nova de Gaia, who were sampled through a nonprobabilistic quota-based approach. Cases with a previous RT-PCR diagnosis of COVID-19 were excluded. Sociodemographic and clinical information was collected using a self-administered, written questionnaire. Blood samples were collected for serological laboratory analysis to detect and quantify SARS-CoV-2 anti-IgG antibodies. RESULTS: We tested 2754 participants. Our results show a SARS-CoV-2 seroprevalence of 3.03% (95% confidence interval: 2.37% - 3.87%). Being a smoker (odds ratio: 0.382, 95% confidence interval: 0.147 - 0.99) and having symptoms of COVID-19 (odds ratio: 2.480, 95% confidence interval: 1.360 - 4.522) were consistently associated with lower and higher odds of SARS-CoV-2 antibody presence, respectively, regardless of the analytic design. Moreover, without adjusting for any variables, having had contact with an infected person within the household was associated with increased odds of a positive test (odds ratio: 9.684, 95% confidence interval: 4.06 - 23.101); after adjusting, having self-reported chronic diseases (odds ratio: 0.448, 95% confidence interval: 0.213 - 0.941) was associated with decreased odds. CONCLUSION: This was the first study to estimate the serological prevalence of SARS-CoV-2 in one of the most populous municipalities in Portugal, representing the first step in the development of an epidemiological surveillance system in Portugal, which can help to improve the diagnosis of COVID-19.

ZnO Transducers for Photoluminescence-Based Biosensors: A Review

Zinc oxide (ZnO) is a wide bandgap semiconductor material that has been widely explored for countless applications, including in biosensing. Among its interesting properties, its remarkable photoluminescence (PL), which typically exhibits an intense signal at room temperature (RT), arises as an extremely appealing alternative transduction approach due to the high sensitivity of its surface properties, providing high sensitivity and selectivity to the sensors relying on luminescence output. Therefore, even though not widely explored, in recent years some studies have been devoted to the use of the PL features of ZnO as an optical transducer for detection and quantification of specific analytes. Hence, in the present paper, we revised the works that have been published in the last few years concerning the use of ZnO nanostructures as the transducer element in different types of PL-based biosensors, namely enzymatic and immunosensors, towards the detection of analytes relevant for health and environment, like antibiotics, glucose, bacteria, virus or even tumor biomarkers. A comprehensive discussion on the possible physical mechanisms that rule the optical sensing response is also provided, as well as a warning regarding the effect that the buffer solution may play on the sensing experiments, as it was seen that the use of phosphate-containing solutions significantly affects the stability of the ZnO nanostructures, which may conduct to misleading interpretations of the sensing results and unreliable conclusions.

Novel Biorecognition Elements against Pathogens in the Design of State-of-the-Art Diagnostics.

Infectious agents, especially bacteria and viruses, account for a vast number of hospitalisations and mortality worldwide. Providing effective and timely diagnostics for the multiplicity of infectious diseases is challenging. Conventional diagnostic solutions, although technologically advanced, are highly complex and often inaccessible in resource-limited settings. An alternative strategy involves convenient rapid diagnostics which can be easily administered at the point-of-care (POC) and at low cost without sacrificing reliability. Biosensors and other rapid POC diagnostic tools which require biorecognition elements to precisely identify the causative pathogen are being developed. The effectiveness of these devices is highly dependent on their biorecognition capabilities. Naturally occurring biorecognition elements include antibodies, bacteriophages and enzymes. Recently, modified molecules such as DNAzymes, peptide nucleic acids and molecules which suffer a selective screening like aptamers and peptides are gaining interest for their biorecognition capabilities and other advantages over purely natural ones, such as robustness and lower production costs. Antimicrobials with a broad-spectrum activity against pathogens, such as antibiotics, are also used in dual diagnostic and therapeutic strategies. Other successful pathogen identification strategies use chemical ligands, molecularly imprinted polymers and Clustered Regularly Interspaced Short Palindromic Repeats-associated nuclease. Herein, the latest developments regarding biorecognition elements and strategies to use them in the design of new biosensors for pathogens detection are reviewed.

Emotional labor of nurses in the front line against the COVID-19 pandemic.

OBJECTIVE: To analyze nurses' experiences in the front line of the fight against the COVID-19 pandemic regarding the performance of emotional labor (EL), aiming at its characterization and identification of support strategies and development opportunities of nurses and practices. METHODS: Qualitative, descriptive, and exploratory study, with content analysis of eleven written narratives and reports from a focus group composed of nurses with experience in caring for patients with COVID-19 from different Hospital Centers in Lisbon, Portugal. RESULTS: Five themes were extracted: 1) Challenges experienced by nurses in the frontline; 2) Emotions experienced by nurses in service care; 3) Emotional responses of nurses and patients: impact on care; 4) EL of nurses in the patient care process; 5) Opportunities for development in the face of the emotional challenge required of nurses in combating COVID-19. FINAL CONSIDERATIONS: The nurses demonstrated the ability to transform this profoundly emotional experience positively.