Treatment of Helicobacter pylori infection in rhesus monkeys using a novel antiadhesion compound.

BACKGROUND & AIMS: Helicobacter pylori can be eradicated by administration of antimicrobials, but resistant strains have emerged, and there is a need for novel therapeutic approaches against this infection. This study aimed to determine the safety and efficacy of 3'-sialyllactose sodium salt (3'SL), an oligosaccharide that occurs naturally in human and bovine milk and that can inhibit the adhesion of H. pylori to human epithelial cells in vitro. METHODS: Twelve H. pylori-positive rhesus monkeys were given 3'SL, either alone (regimens 1 and 2; n = 6) or in combination with omeprazole (regimen 3; n = 4), or bismuth subsalicylate (regimen 4; n = 6). Videogastroscopies were performed before, during, and after treatment, and gastric biopsy specimens were obtained for quantitative cultures and histology. The H. pylori strains colonizing the animals were genotyped. RESULTS: After regimen 1 or 2, 2 of 6 animals were cured permanently, and a third animal was transiently cleared. The 3 other animals remained persistently colonized and did not respond to regimen 3. Regimen 4 resulted in transient decreases in colony counts in 3 of 6 other animals. Gastritis was suppressed only in the 2 animals who became persistently H. pylori negative. There was no apparent relation between 3'SL efficacy and any of the H. pylori tested genotypes. No side effects were observed in any of the animals receiving 3'SL. CONCLUSIONS: Antiadhesive therapy is safe; it can cure or decrease H. pylori colonization in some rhesus monkeys, but the addition of a proton pump inhibitor or bismuth subsalicylate does not increase cure rate.

Host specificity of Helicobacter pylori strains and host responses in experimentally challenged nonhuman primates.

BACKGROUND & AIMS: The specificity of colonization by Helicobacter pylori and complex host-bacterium interactions cannot be readily examined in humans. The aim of this study was to perform such analyses in rhesus monkeys. METHODS: Four animals that had been cured of natural H. pylori colonization were challenged with a mixture of 7 strains of human origin, and bacteria recovered during periodic videogastroscopy were DNA fingerprinted. RESULTS: Three animals carried mixtures of several strains for 4 months, after which strain J166 predominated. In the fourth animal, only strain J238 was isolated from the earliest phase of colonization through 7 months, but strain J166 again became predominant by 10 months after the challenge. Gastritis scores and plasma gastrin and anti-H. pylori immunoglobulin G titers reached levels observed in naturally colonized animals by 4 months after the challenge; however, no plasma immunoglobulin A response was observed up to 10 months. CONCLUSIONS: These results show that (1) natural colonization does not elicit protective immunity against subsequent H. pylori challenge; (2) individuals differ in susceptibility to different H. pylori strains during initial stages of colonization; and (3) certain strains are better suited than others for long-term survival in different hosts. These observations show the complexity of H. pylori-host interactions.

Cure of Helicobacter pylori infection by omeprazole-clarithromycin-based therapy in non-human primates.

Rhesus monkeys raised in colonies tend to become naturally infected by Helicobacter pylori early in life. Earlier attempts to cure H. pylori infection with a 10-day triple therapy (metronidazole, amoxicillin, and peptobismol) were only partially (60%) successful, probably because of preexisting metronidazole resistance. This study was carried out to determine the efficacy of an alternative clarithromycin-omeprazole-based therapy for curing H. pylori infection in Rhesus monkeys (Macaca mulatta), and to examine histologic and serologic correlates of curing. Five monkeys were endoscoped under ketamine anesthesia. Histology and culture of gastric biopsies and serologic tests demonstrated that they were H. pylori-positive. Two animals had not received prior anti-H. pylori treatment, while three other animals had failed triple therapy and carried metronidazole-resistant H. pylori strains. Quadruple therapy with omeprazole, clarithromycin, amoxicillin, and bismuth subsalicylate was given for 10 days to these five animals. All five animals were cured of the infection, and remained H. pylori-free, based on histology and culture at regular intervals for the 5 months posttherapy during which they were followed. Gastritis scores and anti-H. pylori IgG levels decreased in each animal during this period to levels characteristic of uninfected animals. These results indicate that an omeprazole-clarithromycin-based regimen can cure H. pylori infection in Rhesus monkeys, with resolution of abnormal histology and serologic responses. They suggest that this preclinical animal model is useful for testing new anti-H. pylori therapies.

Transient and persistent experimental infection of nonhuman primates with Helicobacter pylori: implications for human disease.

Helicobacter pylori can establish chronic infection in the human gastric mucosa, and it is a major cause of peptic ulcer disease and a principal risk factor for gastric cancer. This creates a need for H. pylori infection models that mimic the human condition. To test the suitability of rhesus monkeys as infection models, H. pylori-free animals were inoculated intragastrically with mixtures of H. pylori strains, bacteria recovered from colonized animals were typed by arbitrarily primed PCR, and host inflammatory and immunologic responses were monitored. Among five H. pylori-free animals inoculated with a mixture of two human strains plus one monkey strain, one became persistently infected and one became only transiently infected. The recovered bacteria matched the monkey input strain in DNA fingerprint. A subsequent trial using two new human isolates and three animals that had resisted colonization by the monkey strain resulted in persistent infection in one animal and transient infection in two others. Antral gastritis, anti-H. pylori serum immunoglobulin G, and atrophy all increased, but with patterns that differed among animals. We conclude that (i) rhesus monkeys can be infected experimentally with H. pylori, (ii) individuals differ in susceptibility to particular bacterial strains, (iii) infections may be transient, and (iv) the fitness of a particular strain for a given host helps determine the consequences of exposure to that strain.

Natural gastric infection with Helicobacter pylori in monkeys: a model for spiral bacteria infection in humans.

BACKGROUND/AIMS: There is no generally accepted model for Helicobacter pylori infection in humans. The aim of this study was to examine the natural history and effect of treatment in rhesus monkeys and sequentially define the immune response to H. pylori in relation to treatment. METHODS: Infection and gastritis were graded blindly by histological analysis and culture of biopsy specimens harvested during gastroduodenoscopies in 26 anesthetized colony-bred monkeys. Plasma H. pylori-specific immunoglobulin (Ig) G levels were determined by enzyme-linked immunosorbent assay. RESULTS: H. pylori and Gastrospirilum hominis-like organisms were present in 13 and 9 monkeys, respectively; 3 animals harbored both organisms, whereas 4 monkeys were not infected. Gastritis score was < or = 1.5 in animals uninfected or infected only with G. hominis-like organisms and > or = 2.0 in all H. pylori-infected animals. IgG ratios were > or = 0.5 in 12 of 13 H. pylori-infected animals and in 2 of 13 H. pylori-negative animals (P < 0.001). One monkey became infected with H. pylori during the observation period, with concurrent increase of gastritis and plasma IgG levels. In untreated animals, infection, gastritis, and plasma IgG levels remained unchanged over 7-15 months. Triple therapy eradicated H. pylori at 6 months in 4 of 6 animals while suppressing gastritis and plasma IgG levels. CONCLUSIONS: Rhesus monkeys harboring H. pylori are persistently infected and have gastritis and elevated specific IgG levels, all of which may respond to appropriate therapy, whereas G. hominis infection is associated with little inflammation.

Comparative intestinal and testes toxicity of four aminothiols in irradiated and nonirradiated mice.

Intestinal and testicular toxicity in groups of nonirradiated and irradiated mice were investigated after intraperitoneal injection of aminothiol compounds or saline. Four aminothiols were studied. Three were prodrugs: WR-2721, WR-3689, and WR-151327 and one was the active form of WR-2721: WR-1065. Thirty minutes after injection, the mice were sham-irradiated or bilaterally exposed (whole body) to 60Co gamma-irradiation at a dose rate of 1 Gy per min to a total dose of 15 Gy. Four days after injection, mice were euthanised, and the intestines and testes were removed and histologically examined. The intestinal crypt cell number was increased in all the irradiated mice given WR-compounds compared to controls (P < 0.05). Interestingly, the crypt cell number in nonirradiated mice given WR-1065 was also greater than control or WR-2721 (P < 0.05) treated mice. Germinal cell numbers from testes of mice administered aminothiols prior to radiation decreased or did not change. Some swelling of the seminiferous tubules was also observed. The germinal cell numbers in sham-irradiated mice were also less than the controls. Thus, aminothiol addition can provide limited protection to intestinal crypt cells but not to germinal cells of the testes in response to gamma-irradiation. There is also evidence that aminothiols are toxic to the germinal cell layer of the seminiferous tubules when given to sham-irradiated mice.

Gastric injury and invasion of parietal cells by spiral bacteria in rhesus monkeys. Are gastritis and hyperchlorhydria infectious diseases?

The possibility of using the rhesus monkey as a model for studying gastric function in the presence of infection with spiral bacteria was studied. Endoscopic evaluation of the gastric mucosa was performed under general anesthesia in 29 colony-bred rhesus monkeys, and gastric pinch biopsy specimens were obtained from each animal. On a separate day, gastric emptying and acid output were determined using a 99mTc dilution technique. Biopsy samples were fixed for light microscopy (H&E, Gram, and Warthin-Starry stains) and for transmission electron microscopy. The presence of spiral bacteria and gastritis was assessed and rated on coded slides. In 8 of 29 monkeys, Helicobacter pylori-like organisms were observed in close proximity to the mucosal epithelial cells or in the lumen of the gastric pits. In 14 other monkeys, "Gastrospirillum hominis"-like organisms were observed in the mucus covering the surface of epithelial cells, in the lumina of the gastric glands, and overlying parietal cells. Gastritis was present in 8 of 8 animals positive for H. pylori-like organisms, in 2 of 14 animals positive for "G. hominis"-like organisms, and in none of the uninfected monkeys, and the mean gastritis index was significantly greater in animals positive for H. pylori-like organisms. Moreover, acid output was significantly higher in monkeys positive for "G. hominis"-like organisms than in controls or animals positive for H. pylori-like organisms. Gastric emptying was not significantly different in the three groups. In conclusion, (a) H. pylori-like, but not "G. hominis"-like, organisms cause gastritis while not modifying acid output; (b) "G. hominis"-like, but not H. pylori-like organisms, invade and on occasion damage parietal cells while apparently causing hyperchlorhydria; and (c) the rhesus monkey appears to be a good model for the study of gastric infection with spiral bacteria.