Alcohol use disorders affect antimicrobial proteins and anti-pneumococcal activity in epithelial lining fluid obtained via bronchoalveolar lavage

Abstract

Aims: Our overall objective was to examine whether characteristics of epithelial lining fluid (ELF) from subjects with alcohol use disorders (AUDs) obtained via bronchoalveolar lavage (BAL) contribute to their predisposition to pneumococcal pneumonia. We sought to compare the anti-pneumococcal activity of acellular human BAL from subjects with AUDs to matched controls. Further, differences in BAL lysozyme activity and lactoferrin concentrations between these two groups were examined to determine the effect of AUDs on these antimicrobial proteins.

Methods: BAL was performed in subjects with AUDs and matched controls. Acellular BAL was used at varying concentrations in an in vitro killing assay of Streptococcus pneumoniae, type 2, and the percent kill of organisms per microgram per milliliter total BAL protein was ascertained. Lysozyme activity and lactoferrin concentrations were measured in BAL from subjects and controls at measured concentrations of BAL protein.

Results: AUD subjects (n = 15) and controls (n = 10) were enrolled in these investigations who were balanced in terms of smoking history. Using a mixed effect model, across the range of BAL protein concentrations, killing of pneumococcus tended to be less potent with BAL fluid from AUD subjects. Additionally, lysozyme activity and lactoferrin concentrations were significantly lower in the AUD group.

Conclusions: The predisposition for pneumococcal pneumonia among those with AUDs may be in part mediated through effects of alcohol on substances within ELF that include antimicrobial proteins. Clarifying the composition and activity of ELF antimicrobial proteins in the setting of AUDs via investigations with human BAL fluid can help establish their contribution to the susceptibility for pulmonary infections in these individuals.

Fig. 1.

Relationship of percent kill of live S. pneumoniae in culture to acellular bronchoalveolar lavage fluid (BAL) total protein for all subjects (alcohol use disorders and controls). The ability of BAL fluid total protein from subjects and controls was examined for its ability to kill S. pneumoniae over a range of dilutions. A significant association between percent kill and total protein concentration was observed (P < 0.001). The line is the estimate of the mean percent kill as a function of log (protein concentration) for all subjects combined. A one unit increase in log protein concentration associated with a 16.3 (95% CI 10.9–21.6) unit increase in percent kill. n = 66, total observations, average three observations per subject or control.

Fig. 2.

Relationship of percent kill of live S. pneumoniae in culture to acellular bronchoalveolar lavage fluid (BAL) total protein from subjects with AUDs (open circles) and control subjects (solid triangles). The estimate of the mean percent kill as a function of log (protein concentration) for all subjects is provided (solid line) as in Fig. 1. The estimate of the mean percent kill as a function of log (protein concentration) for AUD subjects only (dotted line) and for control subjects only (dashed line) is also illustrated. The slope is significant for the AUD subject group (P < 0.0002) and for the control subject group (P < 0.0001). For a given concentration of BAL fluid protein, killing of S. pneumoniae tended to be less potent in subjects with AUDs. AUD subjects, n = 14; control subjects, n = 7.

Fig. 3.

Lysozyme activity in bronchoalveolar lavage fluid per 25 μg total protein in subjects with alcohol use disorders compared with smoking-matched controls. Data presented as medians (middle line within box) with 25–75% confidence intervals (bottom and top of box, respectively). Lysozyme activity was significantly decreased in subjects with alcohol use disorders.

Fig. 4.

Lactoferrin concentration in bronchoalveolar lavage fluid corrected for total protein in subjects with alcohol use disorders compared with smoking-matched controls. Data presented as medians (middle line within box) with 25–75% confidence intervals (bottom and top of box, respectively). Lactoferrin concentrations were significantly decreased in subjects with alcohol use disorders.