[Immunological analysis of piperaquine-resistant murine model of Plasmodium berghei ANKA strain].

OBJECTIVE: To analyze the immunological characteristics of murine model of piperaquine sensitive (PQS) line and resistant (PQR) line of Plasmodium berghei (Pb) ANKA strain. METHODS: 64 Kunming mice were divided into three groups, 16 in each of groups A and C, 32 in group B (16 of 32 were used for observing survival days). Each mouse in groups A and B was infected with 1 x 10(7) erythrocytic stage parasites of PbPQS and PbPQR, respectively. Mice in group C were injected with the same volume of normal saline. On days 4, 8, 12 and 16 after inoculation, 4 mice from each group were sacrificed. Blood samples were collected for thin blood smear examination, and parasitemia rate calculated. Spleens were removed and spleen lymphocytes suspension prepared. Spleen lymphocytes were stimulated with ConA, and cell proliferation was measured by Cell Counting Kit-8 (CCK-8) assay. Nitrogen oxide (NO) and IFN-gamma level of spleen cell culture supernatants were detected by the Griess reagent and ELISA methods, respectively. Another 10 mice were each inoculated with 1 x 10(7) parasites of PbPQR line, and the mice were then challenged with lethal PQS line when the parasites turned into blue stained cells. The parasitemia and survival days were recorded. RESULTS: The average survival time of group A was (9.0 +/- 3.0) d, the parasitemia rate was over 50% at 6-12 days post- infection with severe anemia. On 16th day post-infection, no death was recorded in group B with a parasitemia rate of (2666 +/- 254) %. After ConA stimulation, the proliferation of spleen lymphocytes in groups A (0.65 +/- 0.08) and B (0.86 +/- 0.20) at 12 days after infection was significantly higher than that of group C (0.18 +/- 0.03) (P < 00.01). NO level in spleen cell culture supernatant increased with prolonged infection time. On 12th day post-infection, NO level of groups A [(48.80 +/- 3.49) micromol/L] and B [(54.80 +/- 2.17) micromol/L] was higher than that of group C [(7.80 +/- 0.71) micromol/L] (P < 0.01). IFN-gamma concentration in spleen lymphocytes culture supernatant increased with prolonged infection time. The highest IFN-gamma level of group A was (752.20 +/- 39.49) pg/ml on 12th day post-infection, while in group B it was (855.80 +/- 33.65) pg/ml on 8th day after infection, then decreased on 12th day [(620.20 +/- 27.11) pg/ml]. IFN-gamma level showed a significant difference between groups A and B (P < 0.01). In 10 days after challenge, the parasitemia rate in PQR group was up to (2.44 +/- 2.07)%, and gradually disappeared. No parasite was detected on 40th day after challenge and no mice died. CONCLUSION: The proliferation of spleen cells, NO and IFN-gamma levels of spleen lymphocytes culture supernatant in PbANKA strain PQR line are significantly higher than that of PQS line. PbPQR line can induce certain protective immunoreaction.

The role of luminal factors in the recovery of gastric function and behavioral changes after chronic Helicobacter pylori infection.

The role of chronic infections, such as Helicobacter pylori (Hp), to produce sustained changes in host physiology remains controversial. In this study, we investigate whether the antigenic or bacterial content of the gut, after Hp eradication, influences the changes in gut function induced by chronic Hp infection. Mice were infected with Hp for 4 mo and then treated with antibiotics or placebo for 2 wk. Gastric emptying was measured using videofluoroscopy, feeding behavior using a 24-h feeding system, and intestinal permeability using an isolated jejunal segment arterially perfused with an artificial oxygen carrier, hemoglobin vesicles. Immune responses were assessed by CD3(+) cell counts and anti-Hp antibodies using ELISA. To determine the role of luminal factors in host physiology posteradication, groups of mice received the probiotics containing Lactobacillus rhamnosus R0011 and L. helveticus R0052 or placebo for 2 wk or crude Hp antigen weekly for 2 mo. Chronic Hp infection was associated with delayed gastric emptying, increased intestinal permeability, and increased gastric CD3(+) cell counts. Hp-induced altered feeding patterns did not reverse after eradication. Probiotics accelerated the recovery of paracellular permeability and delayed gastric emptying, improved the CD3(+) cell counts, and normalized altered feeding patterns posteradication. Hp antigen resulted in increased anti-Hp antibodies and increased CD3(+) cell counts in the stomach and delayed recovery of gastric function. Our results suggest that the bacterial content of the gut, as well as the presence of relevant antigens, influences the rate of recovery of host pathophysiology induced by chronic Hp infection. These changes do not seem to occur in association with modulation of intestinal permeability.

Lactobacillus paracasei normalizes muscle hypercontractility in a murine model of postinfective gut dysfunction.

BACKGROUND & AIMS: The effects of probiotics on gut dysfunction in postinfective irritable bowel syndrome are unknown. We tested whether probiotics influence persistent muscle hypercontractility in mice after recovery from infection with Trichinella spiralis and analyzed the underlying mechanisms. METHODS: Mice were gavaged with Lactobacillus paracasei, Lactobacillus johnsonii, Bifidobacterium longum, or Bifidobacterium lactis in spent culture medium from days 10 to 21 after infection. Additional mice received heat-inactivated Lactobacillus paracasei, Lactobacillus paracasei -free spent culture medium, or heat-inactivated Lactobacillus paracasei -free spent culture medium. Lactobacilli enumeration, immunohistochemistry, and cytokine detection (enzyme-linked immunosorbent assay) were performed. Mice were also treated with Lactobacillus paracasei or Lactobacillus paracasei -free spent culture medium from days 18 to 28 after infection. Contractility was measured on days 21 and 28 after infection. RESULTS: Lactobacillus paracasei, but not Lactobacillus johnsonii, Bifidobacterium lactis, or Bifidobacterium longum, attenuated muscle hypercontractility. This was associated with a reduction in the Trichinella spiralis -associated T-helper 2 response and a reduction in transforming growth factor-beta1, cyclooxygenase-2, and prostaglandin E 2 levels in muscle. Attenuation of muscle hypercontractility by Lactobacillus paracasei -free spent culture medium was abolished after heat treatment. Improvement of muscle hypercontractility at day 28 after infection was also observed after the administration of Lactobacillus paracasei or Lactobacillus paracasei -free spent culture medium from day 18 after infection. CONCLUSIONS: Probiotics show strain-dependent attenuation of muscle hypercontractility in an animal model of postinfective irritable bowel syndrome. This likely occurs via both a modulation of the immunologic response to infection and a direct effect of Lactobacillus paracasei or a heat-labile metabolite on postinfective muscle hypercontractility. Lactobacillus paracasei may be useful in the treatment of postinfective irritable bowel syndrome.