COVID-19 among University of Otago students living in North Dunedin households in the first half of 2022: was the prevalence underestimated?

AIMS: To estimate the prevalence of COVID-19 among occupants of North Dunedin student flats between Flat Orientation Week (Flo-Week, week starting 14 February 2022) and the end of Semester 1 (week starting 30 May 2022); to investigate the potential under-reporting of cases to the University of Otago and under-recording of positive rapid antigen test (RAT) results in My Covid Record; to explore the COVID-related experiences of students during the above period. METHODS: Randomly selected households in the North Dunedin area were visited at the end of Semester 1 and oral consent was sought for a short interview comprising closed- and open-ended questions. Households were eligible for inclusion if at least one resident was a University of Otago student. RESULTS: One hundred and thirty-five (96.4%) of 140 eligible households participated, and in 94.1% of these households at least one resident tested positive for COVID-19 between the start of Flo-Week and the date of the interview (a mean period of 109 days [standard deviation 3.6]). In total, 73.6% of the occupants in the participating households tested positive. Of the cases who were University of Otago students, 60.4% reported their positive status to the University. Of all cases diagnosed via a RAT, 66.9% uploaded their result to My Covid Record. Students reported various academic, financial and mental health stresses associated with the general COVID-19 situation during the study period. CONCLUSIONS: These findings suggest that the number of COVID-19 cases reported to the University of Otago between Flo-Week and the end of Semester 1 was a substantial underestimate of the true number, as was the number of cases recorded in My Covid Record. The findings also highlight the considerable impact that COVID-19 had on students during Semester 1.

Retromer is involved in epithelial Na+ channel trafficking.

The epithelial Na+ channel (ENaC) located at the apical membrane in many epithelia is the rate-limiting step for Na+ reabsorption. Tight regulation of the plasma membrane population of ENaC is required, as hypertension or hypotension may result if too many or too few ENaCs are present. Endocytosed ENaC travels to the early endosome and is then either trafficked to the lysosome for degradation or recycled back to the plasma membrane. Recently, the retromer recycling complex, located at the early endosome, has been implicated in plasma membrane protein recycling pathways. We hypothesized that the retromer is required for recycling of ENaC. Stabilization of retromer function with the retromer stabilizing chaperone R55 increased ENaC current, whereas knockdown or overexpression of individual retromer and associated proteins altered ENaC current and cell surface population of ENaC. KIBRA was identified as an ENaC-binding protein allowing ENaC to link to sorting nexin 4 to alter ENaC trafficking. Knockdown of the retromer-associated cargo-binding sorting nexin 27 protein did not alter ENaC current, whereas CCDC22, a CCC-complex protein, coimmunoprecipitated with ENaC, and CCDC22 knockdown decreased ENaC current and population at the cell surface. Together, our results confirm that retromer and the CCC complex play a role in recycling of ENaC to the plasma membrane.