Adjustment of sensitisation and challenge protocols restores functional and inflammatory responses to ovalbumin in guinea-pigs

Abstract

IntroductionInhalation of antigen in atopic asthma induces early (EAR) and late asthmatic responses (LARs), inflammatory cell infiltration and airways hyperresponsiveness (AHR). Previously, we have established a protocol of sensitisation and subsequent ovalbumin (Ova) inhalation challenge in guinea-pigs which induced these 4 features (Smith & Broadley, 2007). However, the responses of guinea-pigs to Ova challenge have recently declined, producing no LAR or AHR and diminished EAR and cells. By making cumulative modifications to the protocol, we sought to restore these features.MethodsGuinea-pigs were sensitised with Ova (i.p. 100 or 150 μg) on days 1 and 5 or days 1, 4 and 7 and challenged with nebulised Ova (100 or 300 μg/ml, 1 h) on day 15. Airway function was measured in conscious guinea-pigs by whole-body plethysmography to record specific airway conductance (sGaw). Airway responsiveness to aerosolized histamine (0.3 mM) was determined before and 24 h after Ova challenge. Bronchoalveolar lavage was performed for total and differential inflammatory cell counts. Lung sections were stained for counting of eosinophils.ResultsLack of AHR and LAR with the original protocol was confirmed. Increasing the Ova challenge concentration from 100 to 300 μg/ml restored AHR and eosinophils and increased the peak of the EAR. Increasing the number of sensitisation injections from 2 to 3 did not alter the responses. Increasing the Ova sensitisation concentration from 100 to 150 μg significantly increased total cells, particularly eosinophils. A LAR was revealed and lymphocytes and eosinophils increased when either the Al(OH)3 concentration was increased or the duration between the final sensitisation injection and Ova challenge was extended from 15 to 21 days.DiscussionThis study has shown that declining allergic responses to Ova in guinea-pigs could be restored by increasing the sensitisation and challenge conditions. It has also demonstrated an important dissociation between EAR, LAR, AHR and inflammation.

Back to the future: re-establishing guinea pigin vivoasthma models

“…However, several studies have also described that allergic guinea pigs have no noticeable LAR [39,106,117]. Indeed, bronchoconstriction induced by allergen provocation is variable in guinea pigs [118,119], similar to asthmatic humans [120,121]. It is possible that the outbred nature of the guinea pigs influence reproducibility and that seasonal oscillation occur, but to our knowledge this has not been verified.…”

Mucoadhesive Cationic Bromelain Laden Nanocarriers Restore Patency of Airway Hyperresponsive Remodeling via Nasal Route

“…Bronchoalveolar lavage was carried out five times by injecting normal saline (2 mL) into lungs via cannulated trachea and drawing out after gentle massage. [ 30 ] The collected samples were amalgamated to estimate total number of cells/mL, level of oxidative stress markers, and pro‐inflammatory cytokines like TNF‐α, IL‐5 and IgG level, respectively.…”