Serological discrimination of dogs infected with gastric Helicobacter spp.and uninfected dogs

Characterization of the humoral immune responses of people to Helicobacter pylori infection has facilitated the investigation of the host response to bacterial virulence factors and the development of sensitive and specific d iagnostic tests. Dogs are commonly infected with gastric Helicobacter spp., but the presence of multiple Helicobacter spp. and possible coinfection in individual dogs have complicated serological evaluation Evaluation of the antigenic homology of Helicobacter spp. revealed that the major protein ban ds of Helicobacter felis and Helicobacter bizzozeronii, two Helicobacter sp p. that infect dogs, were very similar to UreA (29 to 31 kDa), UreB (63 to 66 kDa), and HSP (58 to 60 kDa) of H. pylori, and sera from infected and un infected dogs bound in a similar way to each antigen. Immunoblotting and an enzyme-linked immunosorbent assay (ELISA) with H. felis ATCC 49179 antigen H-ere performed with 101 serum samples (from 78 infected dogs and 23 uninf ected dogs). Samples from uninfected dogs (median = 8) had fever bands on i mmunoblotting than samples from infected dogs (median = 16) (P < 0.05). Com binations of the presence of any two of the low-molecular-mass bands (19, 2 5, 30, 32, and 37 kDa) or the high-molecular-mass bands (86 and 94 kDa) wer e found almost solely in samples from infected dogs (P < 0.0001). Kinetic E LISA results were significantly higher for samples from infected dogs (medi an = 0.0802 optical density unit [OD]/min) than for samples from uninfected dogs (median = 0.01428 OD/min). The combination of ELISA and immunoblottin g results gave a specificity of 95.6% and a sensitivity of 79.8%. No correl ation between ELISA results, colonization density., degree of inflammation, and presence of lymphoid follicles was observed. The results indicate subs tantial antigenic homolog between H. felis, II. pylori, and H. bizzozeronii . The combination of ELISA and immunoblotting H as a highly specific and mo derately sensitive indicator of infection. The degree of seropositivity ass essed by ELISA was not related to bacterial colonization density, the degre e of gastric inflammation or the presence of lymphoid follicles.