ALLERGENIC POTENTIAL OF THREE AIRBORNE ALGAE AND CYANOBACTERIA ISOLATED FROM AN OFFICE BUILDING IN KUALA LUMPUR

Abstract

Airborne algae and cyanobacteria (AAC) have received much attention as their occurrence have been documented in several studies, including indoor environment. There has been concern whether AAC can trigger allergic response and thus, they may have ill health effects, especially in relation to sick building syndrome (SBS). There have been very few studies reported on the allergenicity of AAC. The main objective of this study was to assess the allergenic potential of three AAC, namely Scenedesmus sp., Cylindrospermum sp. and Hapalosiphon sp.1, which were isolated from an office building in Kuala Lumpur. The study was based on a mouse model, with the suspension of AAC powder in phosphate buffered saline (PBS) administered via nasal route. Naïve mice were sensitised to 1 mg/mL of AAC for 10 consecutive days during Phase I immunisation. In Phase II immunisation which was given after five resting weeks, the mice were re-challenged with 20 μL of AAC at two concentrations (0.01 and 1 mg/mL) for three consecutive days before they were sacrificed. The immune response was assessed based on white blood cell profiles, quantification of humoural and intracellular expression of IgE, TH2 predominant and inflammatory cytokines and histopathological examination. In general, the three AAC elicited greater immune response in mice challenged with high (1 mg/mL) concentration of AAC than with low (0.01 mg/mL) concentration. In mice challenged with Scenedesmus sp. at both low and high concentrations, there were elevated peripheral eosinophil and monocyte counts. Significantly higher levels of serum IgE (P<0.05) and IFN-γ (P<0.05) compared to negative control were also observed. The data collected 48 h after the last dose of immunisation also indicated possible cause of allergic airway inflammation, a chronic manifestation of respiratory allergy upon nasal exposure to the algal particles. On the other hand, Cylindrospermum sp. and Hapalosiphon sp.1 did not elicit type-1 hypersensitivity as both eosinophil counts and serum IgE levels were not elevated in the sensitised mice. The results suggest that the two airborne cyanobacteria provoked immune response differently. In mice challenged with Cylindrospermum sp. (1 mg/mL), there were elevated serum IL-4 (22.1 pg/mL, P<0.05). However, the increase in peripheral neutrophil counts (9.2%) against Cylindrospermum sp. (1 mg/mL) was not significant when negative control was compared. In comparison, in mice challenged with Hapalosiphon sp.1, there were elevations of serum IL-6 (4.8 pg/mL, P<0.05) yet the observed increase of peripheral lymphocyte counts (9.2%) was not statistically significant. In addition, the elevations in serum IFN-γ levels were highest in mice nasal challenged with Cylindrospermum sp. (71.9 pg/mL, P<0.05), followed by Hapalosiphon sp.1 (50.6 pg/mL, P<0.05). Taken together, the results suggest that nasal exposure to Cylindrospermum sp. and Hapalosiphon sp.1 may provoke inflammatory immune responses in the airway. Further studies are warranted to assess the potential health impact due to the allergenic potential of the AAC, especially with regards to the effect of continual exposure to low concentration of the algal particles over extended period of time.