Neutrophil infiltration of the airways is a common finding in respiratory syncytial virus (RSV) bronchiolitis. Neutrophil-derived chemokines and neutrophil granule contents can cause further inflammation, hyperresponsiveness, and damage of the airways. In this study, peripheral blood neutrophils incubated with RSV (multiplicity of infection (MOI) = 10) induced IL-8, macrophage inflammatory protein (MIP)-1α, MIP-1β, and myeloperoxidase (MPO) release. In contrast, LPS induced only chemokine but not MPO release. RSV-induced chemokine and MPO release was noncytotoxic as assessed by trypan blue exclusion. The mechanism of RSV-induced chemokine release was shown to be transcription dependent since cytokine mRNA synthesis was increased with RSV stimulation and the process was inhibited by actinomycin-D. In addition, the effect of dexamethasone (dex) on mediator release was also studied. Dex significantly inhibited chemokine release but did not inhibit MPO release. The mechanism of inhibition of the release of these chemokines is probably posttranscriptional since the mRNA synthesis was not inhibited by dex. We conclude that the release of chemokines (IL-8, MIP-1α, MIP-1β) and granule enzymes (MPO) by RSV-stimulated neutrophils may contribute to the pulmonary pathology in RSV bronchiolitis. These in vitro findings showing that dex failed to consistently inhibit all the RSV-induced release of neutrophil inflammatory mediators may explain the variable efficacy of corticosteroids in the treatment of RSV bronchiolitis.

The Pfizer/BioNTech (BNT162b2) SARS-CoV-2 mRNA vaccine demonstrated 95% efficacy after 2 doses during clinical trials.¹ There are reports that individuals with previous SARS-CoV-2 infection elicit stronger antibody responses after 1 dose compared with individuals without prior infection.^2-4 Consequently, individuals with a documented prior COVID-19 infection may be sufficiently protected from reinfection after a single mRNA vaccine dose, which could free up availability of millions of additional doses. We evaluated the SARS-CoV-2 spike immunoglobin (Ig) G antibody levels after 1 and 2 BNT162b2 doses in previously infected individuals compared with those without previous infection.

Respiratory syncytial virus (RSV) infection of airway epithelial cells stimulates the expression and secretion of a variety of cytokines including the chemotactic cytokines interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1), and RANTES (regulated upon activation, normal T cell expressed and secreted). Chemokines are important chemoattractants for the recruitment of distinct sets of leukocytes to airway sites of inflammation. We have shown previously that chemokine expression is regulated in airway epithelial cells (A549) in a stimulus-specific manner in part through the redox-responsive transcription factors AP-1 and NF-κB. In this study, we examined the NF-κB-mediated effects of RSV and the proinflammatory cytokine TNFα on the induction of IL-8, MCP-1 and RANTES chemokine gene expression in A549 epithelial cells. The results demonstrate that RSV induces chemokine expression with distinct kinetics that is associated with a specific pattern of NF-κB binding activity. This distinction was further demonstrated by the differential effects of the NF-κB inhibitors dexamethasone (DEX) and N-acetyl-L-cysteine (NAC). NAC preferentially inhibited RSV induced chemokine expression, whereas DEX preferentially inhibited TNFα induced chemokine expression. DNA binding studies using NF-κB subunit specific binding ELISA demonstrated that RSV and TNFα induced different NF-κB binding complexes containing Rel A (p65) and NF-κB1 (p50). Both TNFα and RSV strongly induced Rel A the activation subunit of NF-κB, whereas only TNFα was able to substantially induce the p50 subunit. Consistent with the expression studies, RSV but not TNFα induction of Rel A and p50 were markedly inhibited by NAC, providing a mechanism by which TNFα and RSV can differentially activate chemokine gene expression via NF-κB. These data suggest that RSV induction of chemokine gene expression, in contrast to TNFα, involves redox-sensitive NF-κB complexes containing predominantly Rel A.

In vaccine clinical trials, both binding antibody (bAb) levels and neutralization antibody (nAb) titers have been shown to be correlates of SARS-CoV-2 vaccine efficacy. We report a strong correlation bAb and nAb responses against the SARS-CoV-2 Omicron (BA.1) variant in infection-naïve and previously infected (convalescent) individuals after one and two doses of BNT162b2 vaccination. The vaccine-induced bAb levels against Omicron were significantly lower compared to previous variants of concern in both infection-naive and convalescent individuals, with the convalescent individuals showing significantly higher bAb compared to the naïve individuals at all timepoints. The finding that bAb highly correlated with nAb provides evidence for utilizing binding antibody assays as a surrogate for neutralizing antibody assays. Our data also revealed that after full vaccination, a higher percentage of individuals had undetectable Omicron nAb (58.6% in naive individuals, 7.4% in convalescent individuals) compared to the percentage of individuals who had negative Omicron bAb (0% in naive individuals, 0% in convalescent individuals). The discordance between bAb and nAb activities and the high degree of immune escape by Omicron may explain the high frequency of Omicron infections after vaccination.

Background: Long-term studies of vaccine recipients are necessary to understand severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody durability and assess the impact of booster doses on antibody levels and protection from infection. The identification of vaccine breakthrough infections among fully vaccinated populations will be important in understanding vaccine efficacy and SARS-CoV-2 vaccine escape capacity. Methods: SARS-CoV-2 spike (S) receptor-binding domain and nucleocapsid (N) immunoglobulin (Ig) G levels were measured in a longitudinal study of 1000 Chicago healthcare workers who were infection naive or previously infected and then vaccinated. Changes in S and N IgG were followed up through 14 months, and vaccine breakthrough infections were identified by increasing levels of N IgG. Results: SARS-CoV-2 S IgG antibody levels among previously infected and previously noninfected individuals decreased steadily for 11 months after vaccination. Administration of a booster 8–11 months after vaccination increased S IgG levels >2-fold beyond those observed after 2 doses, resulting in S IgG levels that were indistinguishable between previously infected and uninfected individuals. Increases in N IgG identified vaccine breakthrough infections and showed >15% breakthrough infection rates during the Omicron wave starting in December 2021. Conclusions: These results demonstrate SARS-CoV-2 antibody changes after vaccination and breakthrough infections and identify high levels of vaccine breakthrough infections during the Omicron wave, based on N IgG increases.

Previous reports demonstrated that severe acute respiratory syndrome coronavirus (SARS-CoV-2) binding immunoglobulin G levels did not increase significantly between the first and second doses of the BNT162b2 vaccine in previously infected individuals. We tested neutralizing antibodies (nAbs) against SARS-CoV-2 Delta and Omicron variants after the first and second doses of this vaccine in infection-naive and previously infected individuals. Delta, but not Omicron, nAb titers significantly increased from the first to the second dose in both groups of individuals. Importantly, we found that Omicron nAb titers were much lower than Delta nAb titers and that even after 2 doses of vaccine, 17 of 29 individuals in the infection-naive group and 2 of 27 in the previously infected group did not have detectable Omicron nAb titers. Infection history alone did not adequately predict whether a second dose resulted in adequate nAb. For future variants of concern, the discussion on the optimal number of vaccine doses should be based on studies testing for nAb against the specific variant.