Umeå University's logo

Enteric adenovirus types F40 and 41 (EAdVs) are a leading cause of diarrhea and diarrhea-associated death in young children and have recently been proposed to cause acute hepatitis in children. EAdVs have a unique capsid architecture and exhibit — unlike other human adenoviruses — a relatively strict tropism for gastrointestinal tissues with, to date, understudied infection mechanism and unknown target cells. In this study, we turn to potentially limiting host factors by comparing EAdV entry in cell lines with respiratory and intestinal origin by cellular perturbation, virus particle tracking, and transmission electron microscopy. Our analyses highlight kinetic advantages for EAdVs in duodenal HuTu80 cell infection and reveal a larger fraction of mobile particles, faster virus uptake, and infectious particle entry in intestinal cells. Moreover, EAdVs display a dependence on clathrin- and dynamin-dependent pathways in intestinal cells. Detailed knowledge of virus entry routes and host factor requirements is essential to understanding pathogenesis and developing new countermeasures. Hence, this study provides novel insights into the entry mechanisms of a medically important virus with emerging tropism in a cell line originating from a relevant tissue. IMPORTANCE Enteric adenoviruses have historically been difficult to grow in cell culture, which has resulted in lack of knowledge of host factors and pathways required for infection of these medically relevant viruses. Previous studies in non-intestinal cell lines showed slow infection kinetics and generated comparatively low virus yields compared to other adenovirus types. We suggest duodenum-derived HuTu80 cells as a superior cell line for studies to complement efforts using complex intestinal tissue models. We show that viral host cell factors required for virus entry differ between cell lines from distinct origins and demonstrate the importance of clathrin-mediated endocytosis.

Background: Men are more severely affected by COVID-19. Testosterone may influence SARS-CoV-2 infection and the immune response.

Objective: To clinically, epidemiologically, and experimentally evaluate the effect of antiandrogens on SARS-CoV-2 infection.

Designs, settings, and participants: A randomized phase 2 clinical trial (COVIDENZA) enrolled 42 hospitalized COVID-19 patients before safety evaluation. We also conducted a population-based retrospective study of 7894 SARS-CoV-2–positive prostate cancer patients and an experimental study using an air-liquid interface three-dimensional culture model of primary lung cells.

Intervention: In COVIDENZA, patients were randomized 2:1 to 5 d of enzalutamide or standard of care.

Outcome measurements: The primary outcomes in COVIDENZA were the time to mechanical ventilation or discharge from hospital. The population-based study investigated risk of hospitalization, intensive care, and death from COVID-19 after androgen inhibition.

Results and limitations: Enzalutamide-treated patients required longer hospitalization (hazard ratio [HR] for discharge from hospital 0.43, 95% confidence interval [CI] 0.20–0.93) and the trial was terminated early. In the epidemiological study, no preventive effects were observed. The frail population of patients treated with androgen deprivation therapy (ADT) in combination with abiraterone acetate or enzalutamide had a higher risk of dying from COVID-19 (HR 2.51, 95% CI 1.52–4.16). In vitro data showed no effect of enzalutamide on virus replication. The epidemiological study has limitations that include residual confounders.

Conclusions: The results do not support a therapeutic effect of enzalutamide or preventive effects of bicalutamide or ADT in COVID-19. Thus, these antiandrogens should not be used for hospitalized COVID-19 patients or as prevention for COVID-19. Further research on these therapeutics in this setting are not warranted.

Patient summary: We studied whether inhibition of testosterone could diminish COVID-19 symptoms. We found no evidence of an effect in a clinical study or in epidemiological or experimental investigations. We conclude that androgen inhibition should not be used for prevention or treatment of COVID-19.

The coronavirus disease 2019, COVID-19, is a complex disease with a wide range of symptoms from asymptomatic infections to severe acute respiratory syndrome with lethal outcome. Individual factors such as age, sex, and comorbidities increase the risk for severe infections, but other aspects, such as genetic variations, are also likely to affect the susceptibility to SARS-CoV-2 infection and disease severity. Here, we used a human 3D lung cell model based on primary cells derived from multiple donors to identity host factors that regulate SARS-CoV-2 infection. With a transcriptomics-based approach, we found that less susceptible donors show a higher expression level of serine protease inhibitors SERPINA1, SERPINE1, and SERPINE2, identifying variation in cellular serpin levels as restricting host factors for SARS-CoV-2 infection. We pinpoint their antiviral mechanism of action to inhibition of the cellular serine protease, TMPRSS2, thereby preventing cleavage of the viral spike protein and TMPRSS2-mediated entry into the target cells. By means of single-cell RNA sequencing, we further locate the expression of the individual serpins to basal, ciliated, club, and goblet cells. Our results add to the importance of genetic variations as determinants for SARS-CoV-2 susceptibility and suggest that genetic deficiencies of cellular serpins might represent risk factors for severe COVID-19. Our study further highlights TMPRSS2 as a promising target for antiviral intervention and opens the door for the usage of locally administered serpins as a treatment against COVID-19.

Clinical data of patients suffering from COVID-19 indicates that statin therapy, used to treat hypercholesterolemia, is associated with a better disease outcome. Whether statins directly affect virus replication or influence the clinical outcome through modulation of immune responses is unknown. We therefore investigated the effect of statins on SARS-CoV-2 infection in human lung cells and found that only fluvastatin inhibited low and high pathogenic coronaviruses in vitro and ex vivo in a dose-dependent manner. Quantitative proteomics revealed that fluvastatin and other tested statins modulated the cholesterol synthesis pathway without altering innate antiviral immune responses in infected lung epithelial cells. However, fluvastatin treatment specifically downregulated proteins that modulate protein translation and viral replication. Collectively, these results support the notion that statin therapy poses no additional risk to individuals exposed to SARS-CoV-2 and that fluvastatin has a moderate beneficial effect on SARS-CoV-2 infection of human lung cells.

Human adenovirus (HAdV)-F40 and -F41 are leading causes of diarrhea and diarrhea-associated mortality in children under the age of five, but the mechanisms by which they infect host cells are poorly understood. HAdVs initiate infection through interactions between the knob domain of the fiber capsid protein and host cell receptors. Unlike most other HAdVs, HAdV-F40 and -F41 possess two different fiber proteins-a long fiber and a short fiber. Whereas the long fiber binds to the Coxsackievirus and adenovirus receptor (CAR), no binding partners have been identified for the short fiber. In this study, we identified heparan sulfate (HS) as an interaction partner for the short fiber of enteric HAdVs. We demonstrate that exposure to acidic pH, which mimics the environment of the stomach, inactivates the interaction of enteric adenovirus with CAR. However, the short fiber:HS interaction is resistant to and even enhanced by acidic pH, which allows attachment to host cells. Our results suggest a switch in receptor usage of enteric HAdVs after exposure to acidic pH and add to the understanding of the function of the short fibers. These results may also be useful for antiviral drug development and the utilization of enteric HAdVs for clinical applications such as vaccine development.