OBJECTIVETo develop an animal model of minimal persistent inflammation (MPI) in allergic rhinitis guinea pigs and to investigate its significance.

METHODSSixty male Hartley guinea pigs were divided into four groups: group A (positive control group), B (MPI model group), C (negative group) and D (bland group) respectively, with fifteen animals in each group. Guinea pigs from group A, B and C were sensitized intraperitoneally by injection of suspension of ovalbumin (OVA) and aluminum hydroxide in 0.9% physiological saline. Then, repeated local booster sensitization with different concentration of OVA suspension (1% and 0.01%) or physiological saline into the nasal cavity of those guinea pigs were performed. For group D, physiological saline was used only. Symptoms (sneezing) of guinea pigs after antigen challenge were observed and the infiltration of eosinophils (EOS) together with the expression of intercellular adhesion molecule 1 (ICAM-1) in the nasal epithelial cells were also examined.

RESULTSWhen challenged with 1% OVA, the sneezing number of guinea pigs in group B was increased markedly than that in group D (P < 0.05). However, there was no difference between group B, A and C (P > 0.05). When challenged with 0.01% OVA, the symptom of sneezing almost disappeared in group B just like that in group D and there was no difference between the two groups (P > 0.05). Besides, there was still more EOS infiltrated in the nasal mucosa of guinea pigs in group B than that in group D (P < 0.05). There was no expression of ICAM-1 in nasal epithelium of guinea pigs in group D, nevertheless, ICAM-1 was found mildly expressed in group B.

CONCLUSIONSMPI models have been established successfully through long term challenge with lower density of OVA in the sensitized guinea pigs, which will provide us with a new method for further research in the mechanism and treatment of allergic rhinitis.