Periodic Evaluation of Anti-SARS-CoV-2 Antibody Levels and Determination of Surrogate Virus Neutralization in Healthcare Workers with COVID-19

Since its first detection in Wuhan, China, in December 2019, coronavirus disease-2019 (COVID-19) has turned into a pandemic, causing high rate of death and economic losses worldwide. Severe acut respiratory syndrome coronavirus-2 (SARS-CoV-2) is a zoonotic, positive-polar RNA virus and initiates an immune response that targets proteins involved in viral infection and replication and includes the production of neutralizing antibodies. Antibodies remain detectable in the plasma for months, binding to virus antigens quickly and strongly and they block infiltration and replication. The detection of total antibody and virus neutralization provides clues about the severity of the disease and the risk of reinfection, as well as being used in epidemiological studies such as virus exposure and determination of infection rate in the population. In this study, it was aimed to determine the disappearance time of total antibodies from the plasma by periodically monitoring the healthcare workers who have been documented as symptomatically or asymptomatically infected with COVID-19 and also to predict the risk of re-infection and the need for vaccination by measuring surrogate virus neutralization. After 30-45 days from the diagnosis of COVID-19 disease (in the acute period), in the 3rd, 6th and 9th months peripheral blood samples were taken from 123 healthcare professionals working in different areas of our hospital in terms of transmission risk and total antibody levels were measured against the SARS-CoV-2 N antigen and surrogate virus neutralization by serological methods. After the first reverse transcriptase polymerase chain reaction (RT-PCR) positivity, SARS-CoV-2-specific anti-nucleocapsid total antibody concentrations were reached to a peak value between 30-45 days (80.37 COI + 37.26) and persisted as positive in most of the participants (111/123, 90.2%) up to six months. Higher peak anti-nucleocapsid antibody titers were associated with longer detection of the antibody (r=0.745, p<0.02). The higher antibody titers were also found to be associated with increased age, more symptomatic disease, higher risk of recurrent virus exposure and lower RT-PCR Ct values and the time for these antibodies to disappear from the blood was also longer (p<0.02). Surrogate virus neutralization were over 70% in 97.8% (90/92) of the participants in the acute period of infection. The SARS-CoV-2 anti-nucleocapsid total antibody level is dynamic and disappears from the plasma within months, this period is shorter in young people, those with asymptomatic patients, those with lower antibody titer and low frequency of virus exposure and also the neutralization of the virus is much more lower. Monitoring of the antibody levels will guide about the immune response against SARS-CoV-2 and these results will give information about re-infection

Real-life experience: sensitivity and specificity of nasal and saliva samples for COVID-19 diagnosis

Background COVID-19 (coronavirus disease 2019) outbreak has spread rapidly around the world, continues to show its effect, and it is not clear how long it will continue. For the diagnosis of COVID-19, it is important to ensure the comfort of the patients and to protect the healthcare workers (HCWs) by reducing the use of protective equipment. Aims To evaluate or assess whether the samples taken by the patient for COVID-19 testing during this pandemic period can be used in real-life experience. Methods Three different samples (nasopharyngeal taken by the healthcare worker, nasopharyngeal, and saliva taken by the patient) from 132 patients were evaluated for the diagnosis of COVID-19. The sensitivity and specificity of the samples in the diagnosis of COVID-19 were compared with real-life experience. Results Paired analyzes were performed by comparing each sample taken by the healthcare worker with the sample taken by the patient. The sensitivity of the three samples (nasopharyngeal taken by the healthcare worker, nasopharyngeal, and saliva taken by the patient) in the diagnosis of the COVID-19 was (100%, 98.7%, and 96.1%, respectively) accepted to be accurate. Conclusions The sample taken by the paramedic was compatible compared to the real-life experience for the samples taken by the patient in the COVID-19 pandemic period. During the pandemic that is unknown when it will end, this study demonstrated that taking the sample of the patient alone for the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) test is a beneficial approach to the protection of the healthcare worker, reducing the need for protective equipment, increasing the patient's comfort and rapid sampling

Detection of SARS-CoV-2 RNA in Upper Respiratory Swap Samples by Pooling Method

Background: Widespread and effective use of molecular diagnostic tests is indispensable for protecting public health and containing the severe respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. More than 1 year into the pandemic, as resources have reached a point of depiction, grouping samples in pools of certain sizes appears to be a reasonable method to reduce both the costs and the processing time without necessitating additional training, equipment, or materials

Dynamic localization of a helper NLR at the plant–pathogen interface underpins pathogen recognition

Plants employ sensor–helper pairs of NLR immune receptors to recognize pathogen effectors and activate immune responses. Yet, the subcellular localization of NLRs pre- and postactivation during pathogen infection remains poorly understood. Here, we show that NRC4, from the “NRC” solanaceous helper NLR family, undergoes dynamic changes in subcellular localization by shuttling to and from the plant–pathogen haustorium interface established during infection by the Irish potato famine pathogen Phytophthora infestans. Specifically, prior to activation, NRC4 accumulates at the extrahaustorial membrane (EHM), presumably to mediate response to perihaustorial effectors that are recognized by NRC4-dependent sensor NLRs. However, not all NLRs accumulate at the EHM, as the closely related helper NRC2 and the distantly related ZAR1 did not accumulate at the EHM. NRC4 required an intact N-terminal coiled-coil domain to accumulate at the EHM, whereas the functionally conserved MADA motif implicated in cell death activation and membrane insertion was dispensable for this process. Strikingly, a constitutively autoactive NRC4 mutant did not accumulate at the EHM and showed punctate distribution that mainly associated with the plasma membrane, suggesting that postactivation, NRC4 may undergo a conformation switch to form clusters that do not preferentially associate with the EHM. When NRC4 is activated by a sensor NLR during infection, however, NRC4 forms puncta mainly at the EHM and, to a lesser extent, at the plasma membrane. We conclude that following activation at the EHM, NRC4 may spread to other cellular membranes from its primary site of activation to trigger immune responses