Maintenance of neutralizing antibodies over ten months in convalescent SARS-CoV-2 afflicted patients.

Knowledge of the level and duration of protective immunity against SARS-CoV-2 after primary infection is of crucial importance for preventive approaches. Currently, there is a lack of evidence on the persistence of specific antibodies. We investigated the generation and maintenance of neutralizing antibodies of convalescent SARS-CoV-2-afflicted patients over a ten-month period post-primary infection using an immunofluorescence assay, a commercial chemiluminescent immunoassay and an in-house enzyme-linked neutralization assay. We present the successful application of an improved version of the plaque-reduction neutralization assay which can be analysed optometrically to simplify data interpretation. Based on the results of the enzyme-linked neutralization assay, neutralizing antibodies were maintained in 77.4% of convalescent individuals without relevant decay over ten months. Furthermore, a positive correlation between severity of infection and antibody titre was observed. In conclusion, SARS-CoV-2-afflicted individuals have been proven to be able to develop and maintain neutralizing antibodies over a period of ten months after primary infection. Findings suggest long-lasting presumably protective humoral immune responses after wild-type infection.

An in vitro model for assessment of SARS-CoV-2 infectivity by defining the correlation between virus isolation and quantitative PCR value: isolation success of SARS-CoV-2 from oropharyngeal swabs correlates negatively with Cq value.

BACKGROUND: At the beginning of the pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), little was known about its actual rate of infectivity and any COVID-19 patient positive in laboratory testing was supposed to be highly infective and a public health risk factor. METHODS: One hundred oropharyngeal samples were obtained during routine work flow of testing symptomatic persons by quantitative polymerase chain reaction (qPCR) and were inoculated onto cell culture of VeroB4 cells to study the degree of infectivity of SARS-CoV-2 in vitro. Quantification by virus titration and an external standard using synthetic RNA gave the breaking point of infectivity in SARS-CoV-2 in vitro. RESULTS: A clear negative correlation (r = - 0.76; p < 0.05) could be asserted between the viral load in quantitative polymerase chain reaction (qPCR) and the probability of a successful isolation in serial isolation experiments of specific oropharyngeal samples positive in qPCR. Quantification by virus titration and an external standard using synthetic RNA indicate a Cq between 27 and 30 in E-gene screening PCR as a breaking point in vitro, where infectivity decreases significantly and isolations become less probable. CONCLUSIONS: This study showed that only the 21% of samples with the highest viral load were infectious enough to transmit the virus in vitro and determined that the dispersion rate in vitro is surprisingly close to those calculated in large retrospective epidemiological studies for SARS-CoV-2. This raises the question of whether this simple in vitro model is suitable to give first insights in dispersion characters of novel or neglected viral pathogens. The statement that SARS-CoV-2 needs at least 40,000 copies to reliably induce infection in vitro is an indication of its transmissibility in Public Health decisions. Applying quantitative PCR systems in diagnosis of SARS-CoV2 can distinguish between patients providing a high risk of transmission and those, where the risk of transmission is probably limited to close and long-lasting contacts.

Home quarantine in COVID-19: A study on 50 consecutive patients in Austria.

A cohort of the first 50 COVID-19 patients in East Tyrol, a region in the southwest of Austria, were monitored in home quarantine. Specific viral ribonucleic acid was detected in throat swabs and stool samples. Analysis indicated a median virus shedding duration of 13 days; however, statistical outliers highlight the importance of consequent testing. This underlines the need of negative throat swabs prior to removing quarantine. We monitored the disease's characteristics via an in-house score called Corona Severity Index, in order to predict an aggravation of the disease. Special attention was paid to early symptoms, such as headache, which appeared to be significantly more common in younger patients (p=0.019). Anosmia and ageusia showed a predominance in female patients (p=0.028). Investigation revealed seven relapses and viral shedding fluctuation in four cases. A follow-up examination shed light on seroconversion which could be observed in 35 of 40 participants. This further clarifies the necessity of establishing discharge standards and follow-up management for COVID-19 patients.

Smell and Taste Disorders in COVID-19 Patients: Objective Testing and Magnetic Resonance Imaging in Five Cases.

Smell and taste disorders are acknowledged as characteristic symptoms for SARS-CoV-2 infection by now. These symptoms have been linked to a neuroinvasive course of disease. In this study, we investigated five consecutive COVID-19 patients with a prolonged course of dysosmia and dysgeusia. Those with objectifiable alteration in taste or smell were subjected to MRI with contrast agent to investigate possible involvement of the central nervous system. We found dysosmia and dysgeusia to be mostly objectifiable, but no evidence for neuroinvasiveness could be detected by MRI in the late stage of the disease. Alterations in taste and smell could be objectified in most patients. Nevertheless, no evidence for a neuroinvasive potential could be identified by MRI, at least in the late stage of disease. We encourage medical professionals to conduct specialized examinations and MRIs in the acute stage of disease, which guarantees an optimum patient care.