Comparison of the quantity and antimicrobial activity of host defence peptides in ear canals between healthy and atopic dogs: A preliminary study

Background: Host defence peptides (HDPs) are involved in cutaneous immune defence. The secretion of HDPs in the ears of healthy normal and non infected atopic dogs has not been measured. Hypotheses/Objectives: The aim of this study was to quantify the concentrations of beta- defensins (cBD3)- like and cathelicidin (cCath) HDPs in ears of healthy and atopic dogs without infectious otitis, additionally to evaluate the antimicrobial effect of the HDPs obtained. Animals: Ten healthy and 20 atopic dogs with mild inflammatory, noninfectious otitis were included.Materials and Methods: Absence of infection was determined by cytological evaluation, and the severity of clinical signs, if present, was assessed by a previously validated score (Otitis Externa Scoring System for Clinical Study, OTIS- 3). The left ear canal of each dog was rinsed with 2 mL of sodium phosphate buffer. The solution obtained was analysed by enzyme-linked immunosorbent assay to quantify HDPs. Additionally, aural secretions were incubated with two concentrations (5 x 105 and 5 x104 colony-forming units/ mL) of Staphylococcus pseudintermedius and the bacterial density measured after 24 h of incubation. Data were statistically analysed. Significance was set as p= 0.05. Results: There was a significantly lower concentration of HDPs from atopic ears when compared with those from normal healthy dogs (cBD3- like: p= 0.0007; cCath: p = 0.049). There was minimal to variable antimicrobial activity in the aural secretions of both groups. Conclusions and Clinical Relevance: This study showed, for the first time, that the ear canals of atopic dogs with mild noninfectious otitis contain a lower concentration of cBD3- like and cCath HDPs than those of healthy dogs with normal ears. A consistent antimicrobial activity was not present in the aural secretions from either group.

Automated summary

This study aimed to measure the concentrations of beta-defensins (cBD3)-like and cathelicidin (cCath) host defence peptides (HDPs) in the ears of healthy and atopic dogs, and to evaluate the antimicrobial effect of the obtained HDPs. The results showed a significantly lower concentration of cBD3-like and cCath HDPs in the ears of atopic dogs compared to healthy dogs. The antimicrobial activity of the aural secretions was minimal to variable in both groups. These findings are important for understanding the changes in defence peptides in the ears of atopic dogs and developing new treatment strategies.