Influenza-A mediated pre-existing immunity levels to SARS-CoV-2 could predict early COVID-19 outbreak dynamics.

Susceptibility to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections is highly variable and could be mediated by a cross-protective pre-immunity. We identified 14 cross-reactive peptides between SARS-CoV-2 and influenza A H1N1, H3N2, and human herpesvirus (HHV)-6A/B with potential relevance. The H1N1 peptide NGVEGF was identical to a peptide in the most critical receptor binding motif in SARS-CoV-2 spike protein that interacts with the angiotensin converting enzyme 2 receptor. About 62%-73% of COVID-19-negative blood donors in Stockholm had antibodies to this peptide in the early pre-vaccination phase of the pandemic. Seasonal flu vaccination enhanced neutralizing capacity to SARS-CoV-2 and T cell immunity to this peptide. Mathematical modeling taking the estimated pre-immunity levels to flu into account could fully predict pre-Omicron SARS-CoV-2 outbreaks in Stockholm and India. This cross-immunity provides mechanistic explanations to the epidemiological observation that influenza vaccination protected people against early SARS-CoV-2 infections and implies that flu-mediated cross-protective immunity significantly dampened the first SARS-CoV-2 outbreaks.

Anticoagulant treatment and COVID-19 mortality among older adults living in nursing homes in Sweden.

Background: Anticoagulants (AC) were introduced in March 2020 as standard of care in nursing home (NH) residents affected with COVID-19 in the Stockholm region, Sweden. ACs are proven to reduce the risk of complications and mortality from COVID-19 among patients of other ages and settings, but there is limited scientific evidence underpinning this practice in the NH setting. Methods: This matched cohort study included 182 NH residents in the Stockholm Region diagnosed with COVID-19 in March-May 2020. The main exposure was any AC treatment. Exposed (n = 91), 49% prevalent (pre-COVID-19 diagnosis) AC and 51% incident AC were compared with unexposed controls (n = 91). The outcome was 28-days all-cause mortality after COVID-19 infection. The mortality odds ratios (OR) were assessed using logistic regression, adjusted for age, sex, multimorbidity, and mobility, also stratified by incident or prevalent AC-type, age group, and sex. Results: Of the 182 individuals diagnosed with COVID-19 (median age 88 years, 68% women), 39% died within 28 days after diagnosis. Use of either incident or prevalent AC was associated with a reduced, adjusted 28-day mortality (OR[95% CI]: 0.31[0.16-0.62]). In stratified analyses, the association was significant in both age groups: 70-89 (OR: 0.37 [0.15-0.89]) and 90-99 years of age (OR: 0.22 [0.07-0.65]. In sex-stratified analysis, the AC-lowering effect was significant in women only (OR: 0.28[0.11-0.67]). In the analyses stratified by AC type, the mortality-lowering effect was observed for both prevalent AC (OR: 0.35[0.12-0.99]) and incident AC (OR: 0.29[0.11-0.76]). Conclusions: Both prevalent and incident use of ACs in prophylactic dosing was associated with reduced 28-day mortality among older individuals with COVID-19 in a NH setting. The effect was seen across age-strata and in women. The findings present new insight in best practice for individuals diagnosed with COVID-19 in the NH setting.

Vaccine-induced correlate of protection against fatal COVID-19 in older and frail adults during waves of neutralization-resistant variants of concern: an observational study.

Background: To inform future preventive measures including repeated vaccinations, we have searched for a clinically useful immune correlate of protection against fatal COVID-19 among nursing homes residents. Methods: We performed repeated capillary blood sampling with analysis of S-binding IgG in an open cohort of nursing home residents in Sweden. We analyzed immunological and registry data from 16 September 2021 to 31 August 2022 with follow-up of deaths to 30 September 2022. The study period included implementation of the 3rd and 4th mRNA monovalent vaccine doses and Omicron virus waves. Findings: A total of 3012 nursing home residents with median age 86 were enrolled. The 3rd mRNA dose elicited a 99-fold relative increase of S-binding IgG in blood and corresponding increase of neutralizing antibodies. The 4th mRNA vaccine dose boosted levels 3.8-fold. Half-life of S-binding IgG was 72 days. A total 528 residents acquired their first SARS-CoV-2 infection after the 3rd or the 4th vaccine dose and the associated 30-day mortality was 9.1%. We found no indication that levels of vaccine-induced antibodies protected against infection with Omicron VOCs. In contrast, the risk of death was inversely correlated to levels of S-directed IgG below the 20th percentile. The death risk plateaued at population average above the lower 35th percentile of S-binding IgG. Interpretation: In the absence of neutralizing antibodies that protect from infection, quantification of S-binding IgG post vaccination may be useful to identify the most vulnerable for fatal COVID-19 among the oldest and frailest. This information is of importance for future strategies to protect vulnerable populations against neutralization resistant variants of concern. Funding: Swedish Research Council, SciLifeLab via Knut and Alice Wallenberg Foundation, VINNOVA. Swedish Healthcare Regions, and Erling Persson Foundation.

Inhibition of the anti-apoptotic protein MCL-1 severely suppresses human hematopoiesis

BH3-mimetics inhibiting anti-apoptotic BCL-2 proteins represent a novel and promising class of antitumor drugs. While the BCL-2 inhibitor venetoclax is already FDA-approved, BCL-XL and MCL-1 inhibitors are currently in early clinical trials. To predict side effects of therapeutic MCL-1 inhibition on the human hematopoietic system, we used RNAi and the small molecule inhibitor S63845 on cord blood-derived CD34+ cells. Both approaches resulted in almost complete depletion of human hematopoietic stem and progenitor cells. As a consequence, maturation into the different hematopoietic lineages was severely restricted and CD34+ cells expressing MCL-1 shRNA showed a very limited engraftment potential upon xenotransplantation. In contrast, mature blood cells survived normally in the absence of MCL-1. Combined inhibition of MCL-1 and BCL-XL resulted in synergistic effects with relevant loss of colony-forming HSPCs already at inhibitor concentrations of 0.1 µM each, indicating "synthetic lethality" of the two BH3-mimetics in the hematopoietic system.

High seroprevalence of SARS-CoV-2 in elderly care employees in Sweden.

The COVID-19 pandemic is growing and spread in the Swedish elderly care system during April 2020. The increasing number of employees on sick-leave due to COVID-19 created severe logistic problems. Some elderly care homes therefore started to screen their personnel to secure the safety of the elderly and to avoid unnecessary quarantine of potentially immune employees. Secondary data from a screening with a COVID-19 rapid test for detection of SARS-CoV-2-specific IgM and IgG of 1,005 employees in 22 elderly care homes in Stockholm, Sweden, were analyzed. Seropositive employees were found in 21 out of the 22 care homes. In total, 23% (231/1,005) of the employees tested positive for antibodies against SARS-CoV-2, and 14.3% (144/1,005) were found positive for IgM (either alone or combined with IgG), indicating recent or present infection. Of those that tested seropositive, 46.5% did not report any clinical symptoms, indicating pre- or asymptomatic infections. Reported symptoms with the highest correlation with seropositivity were fever and loss of smell and taste. These results suggest that antibody testing of employees in elderly care homes is valuable for surveillance of disease development and a crucial screening tool in the effort to decrease the death toll in this pandemic.

[Almost two-thirds of the elderly with covid-19 surviving in nursing homes]. / Närmare två tredjedelar av covid-sjuka på SÄBO överlever.

A large proportion of deaths worldwide have occurred among elderly living in nursing homes. Sweden is no exception with a comparable proportion making up around half of all deaths. The elderly, frail individuals living in nursing homes are among the most vulnerable and with the highest risk to die of covid-19. In spite of that we see almost two-thirds of the infected are still alive with a majority recovering fully after receiving treatment at the nursing home. Of 8 057 residents living in nursing homes in Stockholm, 1 464 (18 %) individuals have so far been diagnosed  with covid-19 and 532 have died (6 % of all residents). Importantly, this means that a great majority of the residents are still alive including almost two-thirds (932/1 464) of the infected individuals.

miR-149 Suppresses Breast Cancer Metastasis by Blocking Paracrine Interactions with Macrophages.

Paracrine activation of cells contained in the tumor microenvironment promotes tumor progression and metastasis. In breast cancer, malignant cells recruit and educate macrophages into a M2 tumor-promoting phenotype that supports the metastatic spread of cancer cells. Here, we show that miR-149 functions as a metastasis-suppressing microRNA in breast cancer cells by limiting colony-stimulating factor-1 (CSF1)-dependent recruitment and M2 polarization of macrophages. In lymph node-positive, triple-negative breast cancer (TNBC) tissues, low miR-149 expression correlated with macrophage infiltration and reduced patient survival. By directly targeting CSF1, miR-149 expression in TNBC cell lines (MDA-MB-231 and BT-549) inhibited the recruitment of human monocytic THP-1 cells and primary human macrophages. Furthermore, in macrophages cocultured with MDA-MB-231 cells expressing miR-149, epidermal growth factor (EGF) and amphiregulin expression levels were strongly reduced, resulting in reduced EGF receptor activation in the cancer cells. In vivo, lung metastases developing from orthotopic MDA-MB-231 tumors were reduced by 75% by miR-149 expression, and this was associated with impaired M2 macrophage infiltration of the primary tumors. These data suggest that miR-149 downregulation functionally contributes to breast tumor progression by recruiting macrophages to the tumor and facilitating CSF1 and EGF receptor cross-talk between cancer cells and macrophages. SIGNIFICANCE: These findings contribute to the understanding of tumor-stroma interactions by showing that miR-149 downregulation in TNBC enhances reciprocal growth factor signaling between macrophages and cancer cells, which promotes tumor progression and metastasis. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/6/1330/F1.large.jpg.

Transient apoptosis inhibition in donor stem cells improves hematopoietic stem cell transplantation.

During hematopoietic stem cell transplantation, a substantial number of donor cells are lost because of apoptotic cell death. Transplantation-associated apoptosis is mediated mainly by the proapoptotic BCL-2 family proteins BIM and BMF, and their proapoptotic function is conserved between mouse and human stem and progenitor cells. Permanent inhibition of apoptosis in donor cells caused by the loss of these BH3-only proteins improves transplantation outcome, but recipients might be exposed to increased risk of lymphomagenesis or autoimmunity. Here, we address whether transient inhibition of apoptosis can serve as a safe but efficient alternative to improve the outcome of stem cell transplantation. We show that transient apoptosis inhibition by short-term overexpression of prosurvival BCL-XL, known to block BIM and BMF, is not only sufficient to increase the viability of hematopoietic stem and progenitor cells during engraftment but also improves transplantation outcome without signs of adverse pathologies. Hence, this strategy represents a promising and novel therapeutic approach, particularly under conditions of limited donor stem cell availability.

Islet engraftment and revascularization in clinical and experimental transplantation.

Proper revascularization after transplantation is assumed to be crucial for appropriate islet graft function. We developed a novel noninvasive imaging method, based on adenoviral transduction of islets with a hypoxia responsive reporter gene, for continuous in vivo monitoring of hypoxia in islet grafts in a mouse model. In addition, morphological data were obtained from a deceased patient previously subject to intraportal transplantation. We detected only transient hypoxia in a minority of the animals transplanted. Importantly, a clear response to hypoxia was observed in vitro after removal of the islet grafts on day 28 after transplantation. Also, the morphological data from the deceased patient demonstrated an extensive revascularization of the transplanted islets. In fact, no differences could be seen between native islets, in pancreas biopsies taken prior to islet isolation, and transplanted islets regarding the number, distribution, and shape of the blood vessels. However, fewer small islets (diameter <39 µm) were found in the liver compared to those found in native pancreases. Notably, an absolute majority of the transplanted islets were found remaining within the venous lumen, in direct contact with the vessel wall. In conclusion, the results presented show less pronounced islet graft hypoxia after subcapsular transplantation than previously reported using more invasive methods. Also, formation of an extensive intraislet capillary network, similar to that seen in native islets in the pancreas, was seen after clinical islet transplantation.

Standardized experimental brain death model for studies of intracranial dynamics, organ preservation, and organ transplantation in the pig.

OBJECTIVES: Brain death impairs organ function and outcome after transplantation. There is a need for a brain death model to allow studies of organ viability and preservation. For neurointensive care research, it is also of interest to have a relevant brain death model for studies of intracranial dynamics and evaluation of cerebral monitoring devices. Therefore, the objective was to develop a standardized clinically relevant brain death model. METHODS: Six pigs of both sexes (10-12 wks old; mean weight, 24.5±1.4 kg) were included. Mean arterial blood pressure, heart rate, intracranial pressure, intracranial compliance, cerebral perfusion pressure, and brain tissue oxygenation (BtiPo2) were recorded during stepwise elevation of intracranial pressure by inflation of an epidural balloon catheter with saline (1 mL/20 mins). Brain death criteria were decided to be reached when cerebral perfusion pressure was <0 mm Hg for 60 mins and at least 10 mL saline was inflated epidurally. BtiPo2 and arterial injections of microspheres were used for confirmation of brain death. RESULTS: A gradual volume-dependent elevation of intracranial pressure was observed. After 10 mL of balloon infusion, mean intracranial pressure was 89.8±9.7 (sd) mm Hg. Intracranial compliance decreased from 0.137±0.069 mL/mm Hg to 0.007±0.001 mL/mm Hg. The mean arterial pressure decreased and the heart rate increased when the intracranial volume was increased to between 5 and 6 mL. All animals showed cerebral perfusion pressure≤0 after 7 to 10 mL of infusion. In all animals, the criteria for brain death with negative cerebral perfusion pressure and BtiPo2 ∼0 mm Hg were achieved. Only a negligible amount of microspheres were found in the cerebrum, confirming brain death. The kidneys showed small foci of acute tubular necrosis. CONCLUSIONS: The standardized brain death model designed in pigs simulates the clinical development of brain death in humans with a classic pressure-volume response and systemic cardiovascular reactions. Brain death was convincingly confirmed.