Brugia filariasis differentially modulates persistent Helicobacter pylori gastritis in the gerbil model

Abstract

In select Helicobacter pylori-infected populations with low gastric cancer, nematode coinfections are common and both helicobacter gastritis and filariasis are modeled in gerbils. We evaluated gastritis, worm counts, tissue cytokine gene expression levels and Th1/Th2-associated antibody responses in H. pylori and Brugia pahangi mono- and coinfected gerbils. H. pylori-associated gastritis indices were significantly lower 21 weeks post-infection in coinfected gerbils (p < or = 0.05) and were inversely proportional to worm counts (r(2) = -0.62, p < 0.003). Additionally, IFN-gamma, IL-1 beta, CXCL1, IL-4 and IL-10 mRNA levels in the gastric antrum reflected a significant host response to gastric H. pylori and as well as systemic filariasis (p < or = 0.05). Despite increasing worm burden (p < 0.05), gastritis progressed in coinfected gerbils (p < 0.03) becoming equivalent to H. pylori-infected gerbils at 42 weeks (p = 0.7). Pro- and anti-inflammatory mediator mRNA levels were notably downregulated in B. pahangi infected gerbils below uninfected control values, suggesting hyporesponsiveness to B. pahangi. Consistent with an increasing Th1 response to H. pylori, IgG2a (p < 0.01), IL-1 beta (p = 0.04) and CXCL1 (p = 0.006) responses significantly increased and IL-4 (p = 0.05) and IL-10 (p = 0.04) were decreased in coinfected gerbils at 42 weeks. Initial systemic responses to B. pahangi resulted in attenuated gastritis in coinfected gerbils, but subsequent filarid-associated hyporesponsiveness appears to have promoted H. pylori gastritis.

Fig. 1

Representative H&E images of various groups at 21 WPHPI. Hp monoinfected gerbils had moderate to severe mucosal and submucosal inflammation with occasional distinct lympho-follicular formation (1a, c: 160 µM; b, d: 80 µM), severe glandular and foveolar hyperplasia with prominent villo-papillary epithelial transformation (1a, c) and superficial and basal glandular dysplasia (1, µM and 1c, 160 µM). In HbBp infected gerbils at 21 WPHPI, there was mild to moderate inflammation, mild to moderate glandular hyperplasia and mild glandular dysplasia (1e, 400 µM and 1f, 80 µM). In Sham controls and Bp monoinfected gerbils, the mucosa was mostly within normal limits (1g, h, 80 µM).

Fig. 2

Representative H&E images of various groups at 42 WPHPI. Both the Hp only (2a, b: 160 µM) and Hp Bp infected animals (2c, d: 80 µM) exhibited severe mucosal inflammation with lympho-follicular formation, glandular hyperplasia, glandular mucinous and/or globoid cytoplasmic change and moderate to severe glandular dysplasia with frequent herniation of the dysplastic glands into the submucosal lymphoid aggregates. In sham and Bp only infected controls, the mucosal changes were none to minimal. On Alcian blue/PAS staining, pH 2.5, the stomach of Hp infected gerbils at WPHPI showed predominant cytoplasmic gastric type (neutral) red mucin expression within the hyperplastic and metaplastic/dysplastic foci with loss of intestinal acidic mucin expression (blue staining) in basal glands as usually seen in the controls (2 g, h, 160 µM). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article).

Fig. 3

Effect of HpBp coinfection on select features and total histological activity indices (HAI) of the gastric antrum pathology compared with Hp mono-infection. a) 21 WPHPI, b) 42 WPHPI. p ≤ 0.05 defined as statistically significant.

Fig. 4

Pro-inflammatory (IFN-γ, IL-1β, CXCL1) and anti-inflammatory (IL-4, IL-10) gene expression measured in gastric antrum by RT-PCR at 21 and 42 WPHPI in gerbils. Values measured from uninfected gerbils (not shown) served as the baseline for fold-change in gene expression levels and were normalized against GAPDH.

Fig. 5

Total adult worm burden per gerbil infected with Bp isolated from several lymphoid and lymphatic tissues by mechanical disruption. Worm counts were similar at 21 and 42 WPHPI but increased between 21 and 42 WPHPI in HpBp infected gerbils. *p < 0.05, **p = 0.12.

Fig. 6

Regression analysis of total adult Bp worm counts vs. total gastric histological activity indices (HAI). An inverse linear relationship is evident at 21 WPHPI in the HpBp infected gerbils; as the number of adult worms increased, gastric histopathologic indices decreased in individual coinfected gerbils. This inverse relationship was lost by 42 WPHPI. In Bp monoinfected gerbils, gastric HAI were minimal at 21 and 42 WPHI and thus the data reflects no relationship between Bp worm counts in Bp monoinfected mice and gastric HAI scores.

Fig. 7

Serum Th1-associated IgG2a was compared to Th2-associated IgG1 specific for Hp antigens as a ratio. At 42 WPHPI there was a significant increase in the ratio of IgG2a to IgG1 in the HpBp coinfected gerbils. *p = 0.0003.