Infectious agent and immune response characteristics of chronic enterocolitis in captive rhesus macaques

Abstract

Chronic enterocolitis is the leading cause of morbidity in colonies of captive rhesus macaques (Macaca mulatta). This study's aim was to identify the common enteric pathogens frequently associated with chronic enterocolitis in normal, immunocompetent rhesus monkeys and to elucidate the influence of this clinical syndrome on the host immune system. We analyzed the fecal specimens from 100 rhesus macaques with or without clinical symptoms of chronic diarrhea. Retrospective analysis revealed an increased incidence of Campylobacter spp. (Campylobacter coli and Campylobacter jejuni), Shigella flexneri, Yersinia enterocolitica, adenovirus, and Strongyloides fulleborni in samples collected from animals with chronic diarrhea (P < 0.05). The presence of additional enteric pathogens, such as Escherichia coli, carrying the eaeA intimin or Stx2c Shiga toxin virulence genes, Balantidium coli, Giardia lamblia, Enterocytozoon bieneusi, and Trichuris trichiura was found in all animals regardless of whether diarrhea was present. In addition, the upregulation of interleukin-1 alpha (IL-1 alpha), IL-3, and tumor necrosis factor alpha cytokine genes, accompanied by an increased presence of activated (CD4(+) CD69(+)) T lymphocytes was found in gut-associated lymphoid tissues collected from animals with chronic enterocolitis and diarrhea in comparison with clinically healthy controls (P < 0.05). These data indicate that chronic enterocolitis and diarrhea are associated, in part, with a variety of enteric pathogens and highlight the importance of defining the microbiological status of nonhuman primates used for infectious disease studies. The data also suggest that chronic colitis in rhesus macaques may have potential as a model of inflammatory bowel disease in humans.

FIG. 1.

H&E-stained tissue sections of small and large intestine tissues from selected animals with symptoms of chronic diarrhea (J079, CJ41, and CJ51) and a clinically normal control (T080). (A) Normal colon (T080) with straight crypts, the presence of goblet cells, and lamina propria with a few mononuclear cells. (B) Chronic colitis (J079). The lamina propria is densely infiltrated by mononuclear cells. (C) Chronic colitis (CJ51). The loss of goblet cells from mucosal epithelium and the presence of Balantidium coli (BC) is shown. (d) Active chronic colitis (CJ51). Moderately dense infiltration of lamina propria by mononuclear cells, crypt dilatation, and crypt abscess with accumulation of granulocytes and necrotic debris in the lumen of the gland can be seen. (E) Duodenum, chronic enteritis (CJ51). Inflammatory cells are present in the lamina propria with inflammation confined to the mucosa. (F) Ileocecal junction, severe chronic ulcerative ileocolitis (CJ41). Both acute and chronic inflammatory cells are present. Numerous neutrophils are present in the ulcer. Lymphocytes, neutrophils, plasma cells and fibroblasts are present in the lamina propria.

FIG. 2.

Percentages of infectious agents detected from stools of 100 rhesus macaques either with (□, n = 50) or without (▪, n = 50) symptoms of chronic diarrhea. A statistically significant difference (P < 0.05) between the two groups is indicated by an asterisk.

FIG. 3.

Flow cytometry histograms of mononuclear cells isolated from lymphoid tissues of an animal with chronic diarrhea (J079) and a clinically healthy control (T080). Gating was performed on population of bright CD3⁺ T lymphocytes as determined by a single-color-stained sample. Major differences between the two animals can be seen between the percentages of activated (CD69) and naive (CD45RA⁺) CD4⁺ and CD8⁺ lymphocyte subsets in both mesenteric lymph nodes and spleens.

FIG. 4.

The relative abundance of mRNA transcripts specific for IL-1α, IL-3, IL-10, IL-16, and TNF-α cytokine genes is shown and compared between the animals with chronic diarrhea (▧, n = 3) and clinically healthy controls ( , n = 3) in mesenteric lymph nodes (A) and spleens (B). The means ± the standard deviations are shown for cytokine genes that were found to be significantly different (a P value of <0.05 is indicated by an asterisk for IL-1α, IL-3, and TNF-α), along with the two genes (IL-10 and IL-16), for which no significant difference was observed. The IL-1α, IL-3, and TNF-α gene expression in mesenteric lymph nodes was significantly higher in animals with chronic diarrhea (P < 0.02, 0.03, and 0.02, respectively). Similarly, IL-1α, IL-3, and TNF-α gene expression in the spleen was significantly higher in animals with chronic diarrhea at P < 0.05, 0.03, and 0.05, respectively.