Effect of bacterial flora on postimmunization gastritis following oral vaccination of mice with Helicobacter pylori heat shock protein 60

Abstract

In order to assess the efficacy of oral Helicobacter pylori heat shock protein 60 (HSP60) as a vaccine, protection against H. pylori infection in specific-pathogen-free (SPF) C57BL/6 and germfree (GF) IQI mice was examined. Prophylactic oral vaccination of these two strains of mice with either H. pylori HSP60 or Escherichia coli GroEL inhibited H. pylori colonization by 90 to 95% at 3 weeks postinfection (p.i.). However, these mice were only partially protected because bacterial loads increased in all animals at 10 weeks p.i. Anti-H. pylori HSP60 immunoglobulin G was detected in serum at 3 weeks p.i. in mice vaccinated with either H. pylori HSP60 or GroEL. Significant increases in the gastritis scores were observed only in SPF mice immunized with H. pylori HSP60. These results indicate that oral vaccination with H. pylori HSP60 has partial protective effects on subsequent H. pylori infection but also induces postimmunization gastritis. However, GF mice immunized with H. pylori HSP60 did not suffer from severe gastritis. Therefore, the presence of bacterial flora appears to contribute to the induction of postimmunization gastritis.

FIG. 1.

Profiles of fusion protein on SDS-PAGE (left panel) and Western blot analysis with H9 MAb (right panel). A 1-μg portion of rGal (lane 1), rGalHpGroEL (lane 2), or rGalEcGroEL (lane 3) was loaded in each lane.

FIG. 2.

Effect of vaccination on bacterial colonization in SPF and GF mice at 3 weeks p.i. The number of bacteria per stomach was determined by a bacterial culturing system as described in the text. The data represent the means plus the standard deviations for 10 (SPF) or 7 (GF) mice. ✽, P < 0.05 (i.e., significantly different from the control CT group [Non-vaccinated/infection]).

FIG. 3.

Gastritis scores in vaccinated SPF and GF mice at 3 (A) and 10 (B) weeks p.i. Hematoxylin-eosin-stained gastric sections were scored for grade of inflammation (grades 0 to 3) as described in the text. The data represent the means plus the standard deviations for 10 (SPF) or 7 (GF) mice. ✽, P < 0.05 (i.e., significantly different from the control CT group [Nonvaccinated with infection]).

FIG. 4.

Photomicrographs of hematoxylin-eosin-stained gastric tissues of SPF (A, B, and C) and GF (D, E, and F) mice prevaccinated with H. pylori HSP60 at 10 weeks p.i. Cardia mucosa of SPF mice frequently showed severe gastritis with disruption of the gland structure, severe inflammatory cell infiltration, and erosion (A). GF mice did not show these symptoms (D). Severe inflammatory cell infiltration was observed in mucosa in SPF mice (B) but not in GF mice (E). Antral mucosa of SPF mice also showed severe inflammatory cell infiltration (C), but GF mice did not (F). Arrows indicate inflammatory cell infiltration, and arrowheads indicate erosion. Magnification, ×200.