Distinct roles for type I and type III interferons in virulent human metapneumovirus pathogenesis.

Human metapneumovirus (HMPV) is an important cause of acute lower respiratory infection in children and adults worldwide. There are four genetic subgroups of HMPV and both neutralizing antibodies and T cells contribute to protection. However, little is known about mechanisms of pathogenesis and most published work is based on a few extensively passaged, laboratory-adapted strains of HMPV. In this study, we isolated and characterized a panel of low passage HMPV clinical isolates representing all four genetic subgroups. The clinical isolates exhibited lower levels of in vitro replication compared to a lab-adapted strain. We compared disease phenotypes using a well-established mouse model. Several virulent isolates caused severe weight loss, lung pathology, airway dysfunction, and fatal disease in mice, which was confirmed in three inbred mouse strains. Disease severity did not correlate with lung viral titer, as virulent strains exhibited restricted replication in the lower airway. Virulent HMPV isolates were associated with markedly increased proinflammatory cytokine production and neutrophil influx; however, depletion of neutrophils or genetic ablation of inflammasome components did not reverse disease. Virulent clinical isolates induced markedly increased type I and type III interferon (IFN) secretion in vitro and in vivo. STAT1/2-deficient mice lacking both type I and type III IFN signaling showed reduced disease severity and increased lung viral replication. Inhibition of type I IFN signaling using a blocking antibody or genetic ablation of the type I IFN receptor reduced pathology with minimal effect on viral replication. Conversely, blockade of type III IFN signaling with a neutralizing antibody or genetic ablation of the IFN-lambda receptor had no effect on pathogenesis but restored viral replication. Collectively, these results demonstrate distinct roles for type I and type III IFN in HMPV pathogenesis and immunity.

Epidemiology and Risk Factors for Community Associated Clostridioides difficile in Children.

OBJECTIVE: To assess which risk factors are associated with community-associated Clostridioides difficile infection (CDI) in children. STUDY DESIGN: This case control study was a retrospective review of all children 1-17 years of age with stool specimens sent for C difficile testing from January 1, 2012, to December 31, 2016. Cases and controls were children who had C difficile testing performed in the community or first 48 hours of hospital admission and >12 weeks after hospital discharge, with no prior positive C difficile testing in last 8 weeks, without other identified causes of diarrhea, and with clinical symptoms. Cases had positive confirmatory testing for C difficile. Controls had negative testing for C difficile and were matched to cases 1:1 by age and year of specimen collection. RESULTS: The overall incidence rate of community-acquired CDI in this cohort was 13.7 per 100 000 children per year. There was a substantial increase in community-acquired CDI from 9.6 per 100 000 children per year in 2012 to a peak of 16.9 per 100 000 children per year in 2015 (Cochran-Armitage test for trend P = .002). The risk factors for community-acquired CDI included non-Hispanic ethnicity; amoxicillin-clavulanate, cephalosporin, and clindamycin use within the previous 12 weeks; a previous positive C difficile test within 6 months; and increased health care visits in the last year. CONCLUSIONS: As rates of community-acquired CDI are increasing, enhanced antibiotic stewardship and recognition of health care disparities may ease the burden of community-acquired CDI.

Impact of Antecedent Antibiotic Usage on Community-associated Clostridioides difficile Infection in Pediatrics.

Children exposed to antibiotics develop community-associated Clostridioides difficile infections in the 12 weeks following exposure. This secondary analysis was a retrospective review of children with filled prescriptions for commonly prescribed antibiotics between January 1, 2012, and December 31, 2016. Compared with amoxicillin, incident rates of community-associated Clostridioides difficile infections were highest following clindamycin, cephalosporins, and amoxicillin-clavulanate.

Novel HLA-B7-restricted human metapneumovirus epitopes enhance viral clearance in mice and are recognized by human CD8+ T cells.

Human metapneumovirus (HMPV) is a leading cause of acute lower respiratory tract illness in children and adults. Repeated infections are common and can be severe in young, elderly, and immunocompromised persons due to short-lived protective humoral immunity. In turn, few protective T cell epitopes have been identified in humans. Thus, we infected transgenic mice expressing the common human HLA MHC-I allele B*07:02 (HLA-B7) with HMPV and screened a robust library of overlapping and computationally predicted HLA-B7 binding peptides. Six HLA-B7-restricted CD8+ T cell epitopes were identified using ELISPOT screening in the F, M, and N proteins, with M195-203 (M195) eliciting the strongest responses. MHC-tetramer flow cytometric staining confirmed HLA-B7 epitope-specific CD8+ T cells migrated to lungs and spleen of HMPV-immune mice. Immunization with pooled HLA-B7-restricted peptides reduced viral titer and protected mice from virulent infection. Finally, we confirmed that CD8+ T cells from HLA-B7 positive humans also recognize the identified epitopes. These results enable identification of HMPV-specific CD8+ T cells in humans and help to inform future HMPV vaccine design.

STAT2 Limits Host Species Specificity of Human Metapneumovirus.

The host tropism of viral infection is determined by a variety of factors, from cell surface receptors to innate immune signaling. Many viruses encode proteins that interfere with host innate immune recognition in order to promote infection. STAT2 is divergent between species and therefore has a role in species restriction of some viruses. To understand the role of STAT2 in human metapneumovirus (HMPV) infection of human and murine tissues, we first infected STAT2-/- mice and found that HMPV could be serially passaged in STAT2-/-, but not WT, mice. We then used in vitro methods to show that HMPV inhibits expression of both STAT1 and STAT2 in human and primate cells, but not in mouse cells. Transfection of the murine form of STAT2 into STAT2-deficient human cells conferred resistance to STAT2 inhibition. Finally, we sought to understand the in vivo role of STAT2 by infecting hSTAT2 knock-in mice with HMPV, and found that mice had increased weight loss, inhibition of type I interferon signaling, and a Th2-polarized cytokine profile compared to WT mice. These results indicate that STAT2 is a target of HMPV in human infection, while the murine version of STAT2 restricts tropism of HMPV for murine cells and tissue.

Use of face coverings in public during the COVID-19 pandemic: an observational study.

Public health agencies have recommended that the public wear face coverings, including face masks, to mitigate COVID-19 transmission. However, the extent to which the public has adopted this recommendation is unknown. An observational study of 3,271 members of the public in May and June 2020 examined face covering use at grocery stores across Wisconsin. We found that only 41.2% used face coverings. Individuals who appeared to be female or older adults had higher odds of using face coverings. Additionally, location-specific variables such as expensiveness of store, county-level population and county-level COVID-19 case prevalence were associated with increased odds of using face coverings. To our knowledge, this is the first direct observational study examining face covering behavior by the public in the U.S., and our findings have implications for public health agencies during the COVID-19 pandemic.

Risk Factors for Recurrent Community-associated Clostridiodes Difficile Infection in Children.

BACKGROUND: Recurrence of community-associated (CA) Clostridiodes difficile infection (CDI) approaches 30%. Studies on risk factors and treatment of choice for pediatric CA-CDI are scarce with variable recommendations. METHODS: This was a retrospective cohort study of the electronic health records of children 1-17 years with stool specimens sent for C. difficile at Kaiser Permanente Northern California from January 01, 2012 to December 31, 2016. Children with (1) CA disease, (2) confirmatory C. difficile laboratory testing with no other identified causes of diarrhea and (3) clinical symptoms consistent with CDI were defined as cases. Recurrent CA-CDI was defined using the above-described case criteria and onset of diarrhea within 8 weeks of primary CA-CDI. RESULTS: Of the 7350 children with stool samples sent for C. difficile testing, 408 had primary CA-CDI. Forty-five (11%) experienced a recurrence. Using multivariable logistic regression, inflammatory bowel disease [odds ratio (OR) 7.5; 95% confidence interval (CI): 2.6-21.1] and cancer (OR 6.3; 95% CI: 1.6-24.1) diagnoses were risk factors for recurrent disease. Compared with children of Caucasian race, those with multi/other/unknown race had an OR of 3.03 (95% CI: 1.04-8.82) of recurrence. There was no statistically significant difference in the type or duration of therapy as a predictor for recurrent CA CDI. Six percent of children who received metronidazole were switched to vancomycin due to subjective metronidazole allergy or intolerance or metronidazole treatment failure. CONCLUSIONS: Recurrent CA-CDI in children in our population is less common than previously reported. This study supports first-line treatment with the standard, short course metronidazole in most cases of primary CA-CDI.