Airway exposure to hypochlorite prior to ovalbumin induces airway hyperreactivity without evidence for allergic sensitization

Background: Some epidemiologic studies have indicated that attendance to chlorinated swimming pools is associated with airway hyperreactivity (AHR), allergies and asthma.

Aim: To investigate the effects of sodium hypochlorite (NaClO), the main pool disinfectant, on allergic sensitization and airway inflammation in mice.

Methods: In a first series of experiments, mice were sensitized to ovalbumin (OVA), followed by OVA aerosols with or without prior nasal instillation of NaClO (3ppm active chlorine). In a second series, naïve mice received 1-7 nasal instillations of OVA, 10min after instillations of NaClO or water. After 1, 3, 5 and 7 exposures airway reactivity to methacholine, cellular inflammation in bronchoalveolar lavage (BAL), serum OVA-specific IgEs and lung Th2 cytokines were measured.

Results: In the first mouse model, airway allergy parameters were not significantly altered upon NaClO administration. However in the second model, NaClO exposure prior to OVA did induce AHR, already after 1 combined application. Combined NaClO+OVA exposure did not lead to an influx of inflammatory cells in BAL fluid or production of anti-OVA IgEs. No AHR developed when OVA was heat-denatured, pre-chlorinated, or replaced by bovine serum albumin or lipopolysaccharide.

Conclusion: Nasal instillation of NaClO prior to OVA induces AHR without allergic sensitization. This response is OVA-specific.