Age-Associated Seroprevalence of Coronavirus Antibodies: Population-Based Serosurveys in 2013 and 2020, British Columbia, Canada

Background

Older adults have been disproportionately affected during the SARS-CoV-2 pandemic, including higher risk of severe disease and long-COVID. Prior exposure to endemic human coronaviruses (HCoV) may modulate the response to SARS-CoV-2 infection and contribute to age-related observations. We hypothesized that cross-reactive antibodies to SARS-CoV-2 are associated with antibodies to HCoV and that both increase with age.

Methods

To assess SARS-CoV-2 unexposed individuals, we drew upon archived anonymized residual sero-surveys conducted in British Columbia (BC), Canada, including before SARS-CoV-2 emergence (May, 2013) and before widespread community circulation in BC (May, 2020). Fifty sera, sex-balanced per ten-year age band, were sought among individuals ≤10 to ≥80 years old, supplemented as indicated by sera from March and September 2020. Sera were tested on the Meso Scale Diagnostics (MSD) electrochemiluminescent multiplex immunoassay to quantify IgG antibody against the Spike proteins of HCoV, including alpha (HCoV-229E, HCoV-NL63) and beta (HCoV-HKU1, HCoV-OC43) viruses, and the 2003 epidemic beta coronavirus, SARS-CoV-1. Cross-reactive antibodies to Spike, Nucleocapsid, and the Receptor Binding Domain (RBD) of SARS-CoV-2 were similarly measured, with SARS-CoV-2 sero-positivity overall defined by positivity on ≥2 targets.

Results

Samples included 407 sera from 2013, of which 17 were children ≤10 years. The 2020 samples included 488 sera, of which 88 were children ≤10 years. Anti-Spike antibodies to all four endemic HCoV were acquired by 10 years of age. There were 20/407 (5%) sera in 2013 and 8/488 (2%) in 2020 that were considered sero-positive for SARS-CoV-2 based on MSD testing. Of note, antibody to the single SARS-CoV-2 RBD target was detected in 329/407 (81%) of 2013 sera and 91/488 (19%) of 2020 sera. Among the SARS-CoV-2 overall sero-negative population, age was correlated with anti-HCoV antibody levels and these, notably 229E and HKU1, were correlated with cross-reactive anti-SARS-CoV-2 RBD titres. SARS-CoV-2 overall sero-positive individuals showed higher titres to HCoV more generally.

Conclusion

Most people have an HCoV priming exposure by 10 years of age and IgG levels are stable thereafter. Anti-HCoV antibodies can cross-react with SARS-CoV-2 epitopes. These immunological interactions warrant further investigation with respect to their implications for COVID-19 clinical outcomes.

Importance of separation of the nasopharyngeal and extradural spaces

The extradural dead space must be separated from the nasopharynx to avoid a potentially lethal complication. This can be accomplished by a variety of methods involving vascularized flaps. However, the flap must be large enough to close the defect and it must be well vascularized. A case is presented to illustrate these important features.

Diffusion versus iontophoresis in the transport of gentamicin in the burned rabbit ear model

This experimental study demonstrates that iontophoresis can be used to transport biologically active gentamicin into auricular cartilage. Fifty female New Zealand White rabbits were divided into three groups: live controls with unburned ears, live animals with burn-injured ears (deep or partial-thickness), and euthanized animals with unburned ears. Each group was then divided into subgroups that received gentamicin transported by iontophoresis or diffusion. In ears subjected to iontophoresis, adequate gentamicin activity could be demonstrated only in the cartilage of euthanized animals with unburned ears and live animals with full-thickness burned ears. Diffusion did not transport a detectable level of gentamicin in any instance. Diffusion is ineffective in the transport of gentamicin and should not be used as a primary method of treatment for ear chondritis. Iontophoresis did not transport active gentamicin across partial-thickness burns, presumably because the migrating antibiotic molecules were dispersed throughout the body by the circulation. However, if the circulation is destroyed, as in a full-thickness burn, iontophoresis can move the biologically active gentamicin into the cartilage.

Soft-tissue expansion in lower extremity reconstruction

Soft-tissue expansion in the lower extremities is typically well tolerated. The more proximal one is--that is, the closer to the thigh and buttocks--the easier and less complication prone the expansion will be. It is another valuable technique for resurfacing the lower extremity and for reconstructing defects in contour and in skin character. There are limitations to this technique, which generally is most useful in late reconstructions. Intraoperative expansion has no place in lower extremity reconstruction. Soft-tissue expansion may be limited by an unsuitable geometry or the sheer size of defects. It should not be used next to open wounds. Soft-tissue expansion offers significant advantage in that the coverage of a defect will be replaced with tissue like that lost. Seldom does one see necrosis of advanced flaps, so that there is little risk of tissue loss in using this modality. There is an excellent vascularity to the flaps and an excellent character to the skin. In addition, in this cost-conscious era, soft-tissue expansion is quite cost effective, and in many cases the procedures can be conducted on an outpatient basis with a minimum of hospitalization, if any. With care to select patients properly, design carefully, and conduct expansion in a leisurely fashion, soft-tissue expansion offers a valuable means of reconstructing both large and small lower extremity defects.

Detection of HLA-DRw specificities by mixed agglutination

By means of mixed agglutination test with staphylococcal protein A indicator system, DRw antigens were studied on lymphocytes obtained from tonsils, peripheral blood and thymuses. Monospecific antisera to DRw 1, 2, 3, 6 and 7 which were preadsorbed with pooled platelets gave mixed agglutination titers of 300 or more against B cells of human tonsilar lymphocytes and peripheral blood lymphocytes. The DR phenotypes of human tonsilar lymphocytes and peripheral blood lymphocytes determined by mixed agglutination tests corresponded to those established by lymphocytotoxicity tests. Upon stimulation of thymocytes or T cells of peripheral blood lymphocytes by Con-A, DRw antigens became detectable by mixed agglutination tests. Simultaneous experiments on the stimulated T cells of peripheral blood lymphocytes by membrane fluorescence tests showed that 21-45% of the stimulated T cells possessed DRw antigens at a detectable level, while less than 2% of unstimulated cells were positive. These results indicated that DRw antigens are present in the subpopulation of T cells which may expand in the response to Con-A stimulation.