The C30 endopeptidase (3C-like protease; 3CL^pro) is essential for the life cycle of SARS-CoV-2 (severe acute respiratory syndrome-coronavirus-2) since it plays a pivotal role in viral replication and transcription and, hence, is a promising drug target. Molecules isolated from animals, insects, plants, or microorganisms can serve as a scaffold for the design of novel biopharmaceutical products. Crotamine, a small cationic peptide from the venom of the rattlesnake Crotalus durissus terrificus, has been the focus of many studies since it exhibits activities such as analgesic, in vitro antibacterial, and hemolytic activities. The crotamine derivative L-peptides (L-CDP) that inhibit the 3CL protease in the low µM range were examined since they are susceptible to proteolytic degradation; we explored the utility of their D-enantiomers form. Comparative uptake inhibition analysis showed D-CDP as a promising prototype for a D-peptide-based drug. We also found that the D-peptides can impair SARS-CoV-2 replication in vivo, probably targeting the viral protease 3CL^pro.

Background: As of today, the effect of coronavirus disease 2019 (COVID-19) on male fertility remains unclear. Studies published so far have partly contradictory results, likely due to very small sample sizes and heterogeneous populations. To gain a deeper understanding of the impact of COVID-19 on male fertility, we performed a prospective case–control study, in which we examined the ejaculate of 37 subjects, including 25 subjects in the acute phase of mild COVID-19 and 12 subjects who did not suffer from COVID-19. Determination of semen parameters, severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) qPCR, and infectivity analysis were performed in the acute phase of the disease and in series. Results: Semen parameter values did not differ significantly between subjects with mild COVID-19 and the control group. The serial examination of semen parameters revealed no significant changes between 4, 18, and 82 days after the onset of symptoms. SARS-CoV-2 RNA or infectious particles could not be detected in any ejaculate. Conclusion: Mild COVID-19 seems to have no detrimental effect on semen parameter values.

Objectives: Currently, there are no approved treatments for early disease stages of COVID-19 and few strategies to prevent disease progression after infection with SARS-CoV-2. The objective of this study is to evaluate the safety and efficacy of convalescent plasma (CP) or camostat mesylate administered within 72 h of diagnosis of SARS-CoV-2 infection in adult individuals with pre-existing risk factors at higher risk of getting seriously ill with COVID-19. Camostat mesylate acts as an inhibitor of the host cell serine protease TMPRSS2 and prevents the virus from entering the cell. CP represents another antiviral strategy in terms of passive immunization. The working hypothesis to be tested in the RES-Q-HR study is that the early use of CP or camostat mesylate reduces the likelihood of disease progression to (modified) WHO stages 4b-8 in SARS-CoV-2-positive adult patients at high risk of moderate or severe COVID-19 progression. Trial design: This study is a 4-arm (parallel group), multicenter, randomized (2:2:1:1 ratio), partly double-blind, controlled trial to evaluate the safety and efficacy of convalescent plasma (CP) or camostat mesylate with control or placebo in adult patients diagnosed with SARS-CoV-2 infection and high risk for progression to moderate/severe COVID-19. Superiority of the intervention arms will be tested. Participants: The trial is conducted at 10–15 tertiary care centers in Germany. Individuals aged 18 years or above with ability to provide written informed consent with SARS-CoV-2 infection, confirmed by PCR within 3 days or less before enrolment and the presence of at least one SARS-CoV-2 symptom (such as fever, cough, shortness of breath, sore throat, headache, fatigue, smell/and or taste disorder, diarrhea, abdominal symptoms, exanthema) and symptom duration of not more than 3 days. Further inclusion criteria comprise: Presence of at least one of the following criteria indicating increased risk for severe COVID-19: Age > 75 years Chronic obstructive pulmonary disease (COPD) and/or pulmonary fibrosis BMI > 40 kg/m² Age > 65 years with at least one other risk factor (BMI > 35 kg/m², coronary artery disease (CAD), chronic kidney disease (CKD) with GFR < 60 ml/min but ≥ 30 ml/min, diabetes mellitus, active tumor disease) BMI > 35 kg/m² with at least one other risk factor (CAD, CKD with GFR < 60 ml/min but ≥ 30 ml/min, diabetes mellitus, active tumor disease) Exclusion criteria: Age < 18 years Unable to give informed consent Pregnant women or breastfeeding mothers Previous transfusion reaction or other contraindication to a plasma transfusion Known hypersensitivity to camostat mesylate and/or severe pancreatitis Volume stress due to CP administration would be intolerable Known IgA deficiency Life expectancy < 6 months Duration SARS-CoV-2 typical symptoms > 3 days SARS-CoV-2 PCR detection older than 3 days SARS-CoV-2 associated clinical condition ≥ WHO stage 3 (patients hospitalized for other reasons than COVID-19 may be included if they fulfill all inclusion and none of the exclusion criteria) Previously or currently hospitalized due to SARS-CoV-2 Previous antiviral therapy for SARS-CoV-2 ALT or AST > 5 x ULN at screening Liver cirrhosis > Child A (patients with Child B/C cirrhosis are excluded from the trial) Chronic kidney disease with GFR < 30 ml/min Concurrent or planned anticancer treatment during trial period Accommodation in an institution due to legal orders (§40(4) AMG). Any psycho-social condition hampering compliance with the study protocol. Evidence of current drug or alcohol abuse Use of other investigational treatment within 5 half-lives of enrolment is prohibited Previous use of convalescent plasma for COVID-19 Concomitant proven influenza A infection Patients with organ or bone marrow transplant in the three months prior to screening visit Intervention and comparator: Participants will be randomized to the following 4 groups: Convalescent plasma (CP), 2 units at screening/baseline visit (day 0) or day 1; CP is defined by the presence of neutralizing anti-SARS-CoV-2 antibodies with titers ≥ 1:160; individuals with body weight ≥ 150 kg will receive a third unit of plasma on day 3 Camostat mesylate (200 mg per capsule, one capsule taken each in the morning, afternoon and evening on days 1–7) Standard of care (SOC, control for CP) Placebo (identical in appearance to camostat mesylate capsules, one capsule taken each morning, afternoon and evening on days 1–7; for camostat mesylate control group) Participants will be monitored after screening/baseline on day 3, day 5, day 8, and day 14. On day 28 and day 56, telephone visits and on day 90, another outpatient visit are scheduled. Adverse events and serious adverse events will be monitored and reported until the end of the study. An independent data safety monitoring committee will review trial progression and safety. Main outcomes: The primary endpoint of the study is the cumulative number of individuals who progress to or beyond category 4b on the modified WHO COVID-19 ordinal scale (defined as hospitalization with COVID-19 pneumonia and additional oxygen demand via nasal cannula or mask) within 28 days after randomization. Randomization: Participants will be randomized using the Alea-Tool (aleaclinical.com) in a 2:2:1:1 ratio to the treatment arms (1) CP, (2) camostat mesylate, (3) standard of care (SoC), and (4) placebo matching camostat mesylate. Randomization will be stratified by study center. Blinding (masking): The camostat mesylate treatment arm and the respective placebo will be blinded for participants, caregivers, and those assessing outcomes. The treatment arms convalescent plasma and standard of care will not be blinded and thus are open-labeled, unblinded. Numbers to be randomized (sample size): Overall, n = 994 participants will be randomized to the following groups: n = 331 to convalescent plasma (CP), n = 331 to camostat mesylate, n = 166 to standard of care (SoC), and n = 166 to placebo matching camostat mesylate. Trial status: The RES-Q-HR protocol (V04F) was approved on the 18 December 2020 by the local ethics committee and by the regulatory institutions PEI/BfARM on the 2 December 2020. The trial was opened for recruitment on 26 December 2020; the first patient was enrolled on 7 January 2021 and randomized on 8 January 2021. Recruitment shall be completed by June 2021. The current protocol version RES-Q HR V05F is from 4 January 2021, which was approved on the 18 January 2021. Trial registration: EudraCT Number 2020-004695-18. Registered on September 29, 2020. ClinicalTrial.gov NCT04681430. Registered on December 23, 2020, prior to the start of the enrollment (which was opened on December 26, 2020). Full protocol: The full protocol (V05F) is attached as an additional file, accessible from the Trials website (Additional file 1). In the interest in expediting dissemination of this material, the familiar formatting has been eliminated; this letter serves as a summary of the key elements of the full protocol. The study protocol has been reported in accordance with the Standard Protocol Items: Recommendations for Clinical Interventional Trials (SPIRIT) guidelines (Additional file 2).

Purpose: We describe a diagnostic procedure suitable for scheduling (re-)vaccination against severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) according to individual state of humoral immunization. Methods: To clarify the relation between quantitative antibody measurements and humoral ex vivo immune responsiveness, we monitored 124 individuals before, during and six months after vaccination with Spikevax (Moderna, Cambridge, MA, USA). Antibodies against SARS-CoV-2 spike (S1) protein receptor-binding domain (S1-AB) and against nucleocapsid antigens were measured by chemiluminescent immunoassay (Roche). Virus-neutralizing activities were determined by surrogate assays (NeutraLISA, Euroimmune; cPass, GenScript). Neutralization of SARS-CoV-2 in cell culture (full virus NT) served as an ex vivo correlate for humoral immune responsiveness. Results: Vaccination responses varied considerably. Six months after the second vaccination, participants still positive for the full virus NT were safely determined by S1-AB levels ≥1000 U/mL. The full virus NT-positive fraction of participants with S1-AB levels 70% as determined by surrogate assays (NeutraLISA or cPas). Participants that were full virus NT-negative and presumably insufficiently protected could thus be identified by a sensitivity of >83% and a specificity of >95%. Conclusion: The described diagnostic strategy possibly supports individualized (re-)vaccination schedules based on simple and rapid measurement of serum-based SARS-CoV-2 antibody levels. Our data apply only to WUHAN-type SARS-CoV-2 virus and the current version of the mRNA vaccine from Moderna (Cambridge, MA, USA). Adaptation to other vaccines and more recent SARS-CoV-2 strains will require modification of cut-offs and re-evaluation of sensitivity/specificity.

Concerns of possible transmission of SARS-CoV-2 from donors to patients by corneal transplantation have caused a decline in corneal transplantations. Graft culture media are routinely tested for infectious risks, but it is unclear whether this constitutes a viable means to avoid transmitting SARS-CoV-2 via keratoplasty. We found that SARS-CoV-2 RNA was not present in the medium after seven days of organ culture of corneas from donors (n = 4), who were SARS-CoV-2-positive upon tissue procurement. These medium samples showed no presence of viral RNA. To pursue this question under controlled conditions and further exclude the possibility of productive infection in corneal grafts, we inoculated corneoscleral discs from healthy donors (n = 8) with infectious SARS-CoV-2 and performed PCR testing of the culture medium at various time points. After seven days of culture, we also tested for SARS-CoV-2 RNA within the inoculated corneal tissue. The medium from tissue samples inoculated with SARS-CoV-2 showed no increase in viral RNA, which may indicate lack of viral replication in these corneal grafts. SARS-CoV-2-RNA was, however, detected on or in corneal tissue seven days after inoculation. Our data suggest that corneal grafts may not be permissive for replication of SARS-CoV-2 and demonstrates that PCR testing of culture media cannot safely exclude that tissue has been exposed to SARS-CoV-2. It also demonstrates the difficulty to differentiate between virus adherence and virus replication by PCR testing in SARS-CoV-2 exposed tissue.