Differential Response of Human Nasal and Bronchial Epithelial Cells Upon Exposure to Size-Fractionated Dairy Dust

<div><p>Exposure to organic dusts is associated with increased respiratory morbidity and mortality in agricultural workers. Organic dusts in dairy farm environments are complex, polydisperse mixtures of toxic and immunogenic compounds. Previous toxicological studies focused primarily on exposures to the respirable size fraction; however, organic dusts in dairy farm environments are known to contain larger particles. Given the size distribution of dusts from dairy farm environments, the nasal and bronchial epithelia represent targets of agricultural dust exposures. In this study, well-differentiated normal human bronchial epithelial cells and human nasal epithelial cells were exposed to two different size fractions (PM₁₀ and PM_>10) of dairy parlor dust using a novel aerosol-to-cell exposure system. Levels of proinflammatory transcripts (interleukin [IL]-8, IL-6, and tumor necrosis factor [TNF]-α) were measured 2 h after exposure. Lactate dehydrogenase (LDH) release was also measured as an indicator of cytotoxicity. Cell exposure to dust was measured in each size fraction as a function of mass, endotoxin, and muramic acid levels. To our knowledge, this is the first study to evaluate the effects of distinct size fractions of agricultural dust on human airway epithelial cells. Our results suggest that both PM₁₀ and PM_>10 size fractions elicit a proinflammatory response in airway epithelial cells and that the entire inhalable size fraction needs to be considered when assessing potential risks from exposure to agricultural dusts. Further, data suggest that human bronchial cells respond differently to these dusts than human nasal cells, and therefore that the two cell types need to be considered separately in airway cell models of agricultural dust toxicity.</p></div

Additional file 1: Figure S1. of MyD88 in lung resident cells governs airway inflammatory and pulmonary function responses to organic dust treatment

Lung parenchymal histopathology of experimental MyD88 bone marrow chimera (donor → recipient) mice treated once with saline or ODE. A representative murine lung section (hematoxylin and eosin stain, x10 magnification) is shown. Note that there is an absence of non-specific inflammation in saline-treated chimeric mice, and there is evidence of slight peribronchiolar and perivascular cellular cuffing following ODE treatment. Line scale is 100 μm. (PDF 699 kb

Day 19 HAI titers.

Cross-reactive antibody responses on day 19 post-vaccination. HAI titers are shown for each vaccine group against the four influenza viruses used in the vaccine. Serum from each mouse was obtained on day 19 post-vaccination. Dotted lines indicate 1:40 HAI titers. Statistical significance was determined by one-way ANOVA (p<0.05).</p

Mouse neutralization titers.

Influenza viruses cause epidemics and can cause pandemics with substantial morbidity with some mortality every year. Seasonal influenza vaccines have incomplete effectiveness and elicit a narrow antibody response that often does not protect against mutations occurring in influenza viruses. Thus, various vaccine approaches have been investigated to improve safety and efficacy. Here, we evaluate an mRNA influenza vaccine encoding hemagglutinin (HA) proteins in a BALB/c mouse model. The results show that mRNA vaccination elicits neutralizing and serum antibodies to each influenza virus strain contained in the current quadrivalent vaccine that is designed to protect against four different influenza viruses including two influenza A viruses (IAV) and two influenza B (IBV), as well as several antigenically distinct influenza virus strains in both hemagglutination inhibition assay (HAI) and virus neutralization assays. The quadrivalent mRNA vaccines had antibody titers comparable to the antibodies elicited by the monovalent vaccines to each tested virus regardless of dosage following an mRNA booster vaccine. Mice vaccinated with mRNA encoding an H1 HA had decreased weight loss and decreased lung viral titers compared to mice not vaccinated with an mRNA encoding an H1 HA. Overall, this study demonstrates the efficacy of mRNA-based seasonal influenza vaccines are their potential to replace both the currently available split-inactivated, and live-attenuated seasonal influenza vaccines.</div

Vaccination outline.

Influenza viruses cause epidemics and can cause pandemics with substantial morbidity with some mortality every year. Seasonal influenza vaccines have incomplete effectiveness and elicit a narrow antibody response that often does not protect against mutations occurring in influenza viruses. Thus, various vaccine approaches have been investigated to improve safety and efficacy. Here, we evaluate an mRNA influenza vaccine encoding hemagglutinin (HA) proteins in a BALB/c mouse model. The results show that mRNA vaccination elicits neutralizing and serum antibodies to each influenza virus strain contained in the current quadrivalent vaccine that is designed to protect against four different influenza viruses including two influenza A viruses (IAV) and two influenza B (IBV), as well as several antigenically distinct influenza virus strains in both hemagglutination inhibition assay (HAI) and virus neutralization assays. The quadrivalent mRNA vaccines had antibody titers comparable to the antibodies elicited by the monovalent vaccines to each tested virus regardless of dosage following an mRNA booster vaccine. Mice vaccinated with mRNA encoding an H1 HA had decreased weight loss and decreased lung viral titers compared to mice not vaccinated with an mRNA encoding an H1 HA. Overall, this study demonstrates the efficacy of mRNA-based seasonal influenza vaccines are their potential to replace both the currently available split-inactivated, and live-attenuated seasonal influenza vaccines.</div

Day 42 HAI titers.

Cross-reactive antibody responses on day 42 post-vaccination. HAI titers are shown for each vaccine group against the four influenza viruses used in the vaccine as well as antigenic variants for each influenza virus subtype. Panels a, e, i and l are H1N1 viruses. Panels b, f, j and m are H3N2 viruses. Panels c, g and k are B/Victoria influenza viruses while panels d and h are B/Yamagata viruses. Serum from each mouse was obtained on day 42 post-vaccination. Dotted lines indicate 1:40 HAI titers. Error bars represent standard mean errors. Statistical significance was determined by one-way ANOVA (p<0.05).</p

Lung viral titers.

Viral titers in lungs of vaccinated mice. Mice were infected with A/California/04/2009 i.n. with 104 PFU/mouse. Mice from each group (n = 3) were sacrificed on day 3 pi and lungs were harvested using plaque assays as described. Statistical significance was determined by one-way ANOVA (p<0.05).</p

A/California/04/2009 weight loss.

Weight loss of A/California/04/2009 challenged BALB/c mice (n = 6 mice/group). BALB/c mice were challenged intranasally with 104 PFU/mouse. Weight loss was recorded for five days post-infection. Asterisks (*) represent statistical significance based on two-way ANOVA (p<0.05).</p

Size, Composition, and Source Profiles of Inhalable Bioaerosols from Colorado Dairies

Particulate matter emissions from agricultural livestock operations contain both chemical and biological constituents that represent a potential human health hazard. The size and composition of these dusts, however, have not been well described. We evaluated the full size distribution (from 0 to 100 μm in aerodynamic diameter) and chemical/biological composition of inhalable dusts inside several Colorado dairy parlors. Four aerodynamic size fractions (<3, 3–10, 10–30, and >30 μm) were collected and analyzed using a combination of physiochemical techniques to understand the structure of bacterial communities and chemical constituents. Airborne particulate mass followed a bimodal size distribution (one mode at 3 μm and a second above 30 μm), which also correlated with the relative concentrations of the following microbiological markers: bacterial endotoxin, 3-hydroxy fatty acids, and muramic acid. Sequencing of the 16S-rRNA components of this aerosol revealed a microbiome derived predominantly from animal sources. Bacterial genera included <i>Staphlyococcus</i>, <i>Pseudomonas</i>, and <i>Streptococcus</i>, all of which have proinflammatory and pathogenic capacity. Our results suggest that the size distribution of bioaerosols emitted by dairy operations extends well above 10 μm in diameter and contains a diverse mixture of potentially hazardous constituents and opportunistic pathogens. These findings should inform the development of more effective emissions control strategies