The role of antigen form and function in the primary and secondary intestinal immune responses to cholera toxin and toxoid in rats.

This report describes studies of the mucosal antitoxic response in rats after enteric administration of several forms of cholera toxin or toxoid, proteins which differ primarily in their ability to bind to cell membranes and activate cellular adenyl cyclase. These two characteristics appeared to markedly enhance the local primary response to these antigens. A single dose of toxoid lacking these features was ineffective in local priming even though it was absorbed and induced a systemic immune response. Single dose mucosal priming occurred only with preparations which bind to cell membranes and was enhanced by those which also activate cellular adenyl cyclase. In contrast, single-dose mucosal boosting was best accomplished by materials with these properties but was also seen with a toxoid lacking both of these functions. The property of membrane binding appears to be most advantageous in mucosal priming, perhaps by increasing effective trapping of absorbed antigen in unprimed mucosal lymphoid tissue, whereas the ability to activate adenyl cyclase appears to enhance primary and secondary type responses about equally. Combinations of crude toxoid and toxin were also more effective in mucosal priming than purified materials, a finding which is unexplained. A single dose of this combination induced mucosal priming which was fully developed in 2 wk, undiminished after 4 too, and only modestly diminished after 8 mo, thus demonstrating relatively prolonged memory in the IgA mucosal immune system. Effective two-dose local immunizing regimens were developed, and it was shown that there was no correlation between the mucosal and systemic secondary antitoxin responses provoked by these regimens.

Differential inhibitory effects of cholera toxoids and ganglioside on the enterotoxins of Vibrio cholerae and Escherichia coli.

Natural cholera toxoid appears to act as a competitive inhibitor of cholera enterotoxin and is thus a useful tool for studying the interaction of cholera enterotoxin with cell membranes. Cholera enterotoxin binds to gut mucosa more rapidly than does its natural toxoid. Once binding occurs, however, it appears to be prolonged for both materials. Formalinized cholera toxoid has no inhibitory effect upon cholera enterotoxin. Enterotoxic activity, ability to bind to gut mucosa, and antitoxigenicity appear to be independent properties of cholera enterotoxin. Natural cholera toxoid does not inhibit Escherichia coli enterotoxin, indicating that although the two enterotoxins activate the same mucosal secretory mechanism they occupy different binding sites in the mucosa. Ganglioside, which may be the mucosal receptor of cholera enterotoxin, is highly efficient in deactivating cholera enterotoxin. By contrast, ganglioside is relatively inefficient in deactivating heat-labile E. coli enterotoxin and is without effect upon the heat-stable component of E. coli enterotoxin. These findings suggest that ganglioside is not likely to be the mucosal receptor for E. coli enterotoxin. Differences in cellular binding of E. coli and cholera enterotoxins may explain, at least in part, the marked differences in the time of onset and duration of their effects upon gut secretion.

Cellular kinetics of the intestinal immune response to cholera toxoid in rats.

The aims of this study were (a) to find a regime of immunization with cholera toxoid in rats which would establish a high density of antitoxin containing cells (ACC) in the lamina propria of the intestine and (b) to determine the origin of the ACC. The best cellular response was achieved by a single i.p. dose of toxoid in FCA followed by an intraintestinal boost 2 wk later. ACC appeared in the thoracic duct lymph 2 days after boosting, reaching a peak of about 200,000 ACC/h at 3--4 days. This was followed by the appearance of large numbers of ACC in the intestine. The i.p. dose of toxoid by itself gave rise to very few ACC in the gut or thoracic duct lymph, but it had clearly primed the gut immune system for a secondary response. Priming was also achieved by the prolonged oral intake of toxoid. The importance of the intestinal route for boosting was shown by the failure of i.p. challenge to give an ACC response in the intestine after i.p. priming and the small response it provoked after oral priming. ACC among thoracic duct lymphocytes (TDL) and in the lamina propria contained predominantly IgA. Two observations indicated that the major source of the lamina propria ACC was from cells that emerged in the thoracic duct lymph after intraintestinal challenge. Firstly, the establishment of a thoracic duct fistula immediately before challenge prevented the appearance of ACC in the intestine. Secondly, many ACC appeared in the intestine of normal rats after the injection of TDL rich in ACC. Although homing of ACC precursors to the gut was not antigen-dependent, the distribution of ACC in the lamina propria was considerably influenced by the site of the intestinal challenge, the density of ACC being greatest at or distal to the site of injection of toxoid into the lumen of the gut.

Acute undifferentiated human diarrhea in the tropics. II. Alterations in intestinal fluid and electrolyte movements.

The nature and magnitude of fluid and electrolyte loss into the small intestine were defined by the marker perfusion technique in patients with acute undifferentiated diarrhea (AUD) in the tropics. The patients were divided into two groups according to their small bowel bacteriologic findings, namely those with a predominant Escherichia coli flora and those with a mixed flora. 11 normal subjects served as controls. Net jejunal fluid secretion occurred into the lumen in four of seven patients with E. coli flora and three of seven with a mixed flora. The magnitude of secretion in the jejunum was greater in the E. coli flora patients than in those with a mixed flora. Four E. coli patients and one mixed flora patient had net fluid secretion in the ileum, although the magnitude of secretion in this area was less than in the jejunum. Intestinal fluid had higher bicarbonate concentration in the ileum than in the jejunum but was isotonic in both regions. It resembled in composition fluid from the same region of intestine in normal individuals. Recovery of normal fluid and electrolyte absorptive function was usually complete in both jejunum and ileum by 6-8 days after onset of the disease. Increase in unidirectional flux rates for H(3)O and (24)Na occurred in acute E. coli flora diarrhea and returned to normal levels in recovery: increase in J(beta) (plasma to lumen flux) primarily accounted for the increase in fluid loss. Intestinal biopsy revealed no alterations in villous architecture.A relationship between small bowel fluid production and the presence of toxigenic strains of E. coli within the small bowel has been found for E. coli flora patients. In many respects this disease resembles acute cholera. The mixed flora group represents a less defined entity which requires further study.

Effect of Escherichia coli on fluid transport across canine small bowel. Mechanism and time-course with enterotoxin and whole bacterial cells.

An Escherichia coli strain isolated from a patient with severe cholera-like diarrhea elaborates a partly heat-labile enterotoxin shown to cause prompt adenyl cyclase stimulation and isotonic fluid secretion by canine jejunum. Both responses disappear upon removal of the enterotoxin. The duration of action of a submaximal dose of this E. coli enterotoxin was brief, despite sustained exposure to the jejunum, suggesting inactivation of the enterotoxin by its interaction with the mucosa. Inoculation of whole bacterial cultures of this E. coli strain into canine duodenum was followed by bacterial survival and induction of net secretion after 4-7 h. The onset of fluid production was associated with increasing gut mucosal adenyl cyclase activity. Washed bacterial cells could also produce fluid secretion. In vivo multiplication of this enterotoxin-producing E. coli was demonstrated 6-12 h after intraduodenal inoculation of approximately 10(6) organisms. This was associated with fluid secretion. Intestinal fluid production occurred without microscopic pathology in the mucosa.

Intestinal fluid and electrolyte transport in human cholera.

The site, nature, magnitude, and duration of fluid and electrolyte loss into the small intestine during the acute and recovery phase of human cholera was defined in 27 Indian patients. 11 subjects without cholera served as controls. The marker perfusion technique employed was shown, in preliminary experiments, to measure accurately jejunal and ileal fluid and electrolyte transmucosal transport rates under conditions of cholera diarrhea. Fluid loss into the lumen occurred from jejunal and ileal mucosa. The fluid was isotonic in both regions. Bicarbonate concentration was significantly higher in ileal than jejunal fluid during all phases of the disease. Bicarbonate concentration in both regions was significantly higher in acute cholera than during convalescence. Fluid loss into the intestinal lumen ranged from 0.07 to 10.9 ml/hr per cm. Losses were significantly greater from jejunum than ileum. Net ileal absorption was recorded in five of 10 acute cholera studies. During the acute phase of the disease, net jejunal fluid transport showed a positive correlation with fasting intestinal flow rate and stool output. Stool output was also positively correlated with jejunal fasting intestinal flow rates. Recovery of normal fluid and electrolyte absorptive function was usually complete in both jejunum and ileum by the sixth day after admission. These findings in human cholera validate the animal models of choleraic diarrhea and suggest that similar measurements of small intestinal secretory function in other nonspecific diarrheal diseases using the marker perfusion technique may be rewarding.

WITHDRAWN: Rice-based oral rehydration solution for treating diarrhoea.

BACKGROUND: Oral rehydration therapy is used to treat dehydration caused by diarrhoea. However the rehydration solution does not reduce stool loss or length of illness. A solution able to do this may lessen the use of ineffective diarrhoea treatments as well as improve morbidity and mortality related to diarrhoea. OBJECTIVES: The objective of this review was to assess the effects of rice-based oral rehydration salts solution compared with glucose-based oral rehydration salts solution on reduction of stool output and duration of diarrhoea in patients with acute watery diarrhoea. SEARCH STRATEGY: We searched the Cochrane Infectious Diseases Group trials register, the Cochrane Controlled Trials Register, Medline, Embase, Lilacs and the reference lists of relevant articles. We also contacted researchers in the field. SELECTION CRITERIA: Randomized trials comparing standard World Health Organization oral rehydration solution with an experimental oral rehydration salts solution in which glucose (20 grams per litre) was replaced by 50-80 grams per litre of rice powder, with the electrolytes remaining unchanged. DATA COLLECTION AND ANALYSIS: Data were extracted independently by a statistician and a clinician. MAIN RESULTS: Twenty-two trials were included. Concealment of allocation was adequate in 15 of these trials. Irrespective of age, people with cholera who were given rice oral rehydration salts solution had substantially lower rates of stool loss than those given oral rehydration salts solution in the first 24 hours. Mean stool outputs in the first 24 hours were lower by 67 millilitres/kg of body weight (weighted mean difference -67.40, 95% confidence interval -94.26 to -41.53) in children, and by 51 millilitres/kg of body weight (weighted mean difference -51.07, 95% confidence interval -65.87 to -36.27) in adults. The rate of stool loss in infants and children with acute non-cholera diarrhoea was reduced by only four millilitres/kg of body weight (weighted mean difference -4.29, 95% confidence interval -9.36 to 0.78). AUTHORS' CONCLUSIONS: Rice-based oral rehydration appears to be effective in reducing stool output in people with cholera. This effect was not apparent in infants and children with non-cholera diarrhoea.

Efficacy of nine-valent pneumococcal conjugate vaccine against pneumonia and invasive pneumococcal disease in The Gambia: randomised, double-blind, placebo-controlled trial.

BACKGROUND: Pneumonia is estimated to cause 2 million deaths every year in children. Streptococcus pneumoniae is the most important cause of severe pneumonia. We aimed to assess the efficacy of a nine-valent pneumococcal conjugate vaccine in children. METHODS: We undertook a randomised, placebo-controlled, double-blind trial in eastern Gambia. Children age 6-51 weeks were randomly allocated three doses of either pneumococcal conjugate vaccine (n=8718) or placebo (8719), with intervals of at least 25 days between doses. Our primary outcome was first episode of radiological pneumonia. Secondary endpoints were clinical or severe clinical pneumonia, invasive pneumococcal disease, and all-cause admissions. Analyses were per protocol and intention to treat. FINDINGS: 529 children assigned vaccine and 568 allocated placebo were not included in the per-protocol analysis. Results of per-protocol and intention-to-treat analyses were similar. By per-protocol analysis, 333 of 8189 children given vaccine had an episode of radiological pneumonia compared with 513 of 8151 who received placebo. Pneumococcal vaccine efficacy was 37% (95% CI 27-45) against first episode of radiological pneumonia. First episodes of clinical pneumonia were reduced overall by 7% (95% CI 1-12). Efficacy of the conjugate vaccine was 77% (51-90) against invasive pneumococcal disease caused by vaccine serotypes, 50% (21-69) against disease caused by all serotypes, and 15% (7-21) against all-cause admissions. We also found an efficacy of 16% (3-28) against mortality. 110 serious adverse events arose in children given the pneumococcal vaccine compared with 131 in those who received placebo. INTERPRETATION: In this rural African setting, pneumococcal conjugate vaccine has high efficacy against radiological pneumonia and invasive pneumococcal disease, and can substantially reduce admissions and improve child survival. Pneumococcal conjugate vaccines should be made available to African infants.

The current status of oral therapy in the treatment of acute diarrheal illness.

PIP: Diarrheal diseases are a primary cause of morbidity and mortality in the developing countries. This is a literature review and evaluation of the new form of oral therapy, surveying field and clinical studies which have been performed. The etiology and effects of diarrheal diseases are discussed. Oral fluid therapy aims at preventing and treating dehydration and facilitating continued dietary intake, not in terminating the diarrhea. The composition of the widely used fluid therapy solution is explained; there are presently some differences of opinion regarding the optimal composition of the solution. Clinical experience with the therapy in hospitals, clinics, and relatively unsupervised home use is cited. This simple, inexpensive therapy seems to be effective for a wide variety of diarrheal diseases and for people in all age groups. The greatest current controversy regarding oral therapy is whether it should be widely used as a home remedy. Further study will be necessary to measure its effectiveness on a home-use basis.^ieng

Conjunctival immunity: compared effects of ocular or intestinal immunization in rats.

The ability to induce a conjunctival antitoxin response by conjunctival or enteric administration of cholera toxin antigen was studied in rats. Repeated enteric immunization caused a vigorous jejunal antitoxin response, but none in the conjunctiva. Enteric immunization did, however, prime for a conjunctival antitoxin response to locally applied antigen, as did direct ocular administration of cholera toxin. Vigorous conjunctival antitoxin responses occurred only after ocular challenge, and were localized to the challenged eye. These results agree with the notions that (1) specific memory cells migrate to the conjunctiva after enteric immunization, or arise locally after ocular immunization; and (2) specific antibody-producing plasma cells arise almost entirely within the immunized conjunctiva, and few if any migrate to the conjunctiva from distant mucosae or from the conjunctiva of the immunized eye to that of the nonimmunized eye.

Management of acute diarrhea in children: lessons learned.

PIP: Each year diarrheal disease causes an estimated 3.2 million deaths worldwide in children under 5 years of age. Reported attack rates in developing countries range from 1 to 12 episodes per child per year, with a global average of 3 episodes per child per year. Diarrhea is associated with 1/4 of all deaths in children under 5 years in developing countries. Oral rehydration therapy (ORT) is the cornerstone of global efforts to reduce mortality from acute diarrhea. The World Health Organization (WHO)/UNICEF ORS formula contains glucose and sodium in a molar ratio of 1.2:1. Potassium chloride is added to replace potassium lost in the stool. Trisodium citrate dihydrate (or sodium bicarbonate) corrects metabolic acidosis caused by fecal loss of bicarbonate. The WHO case management strategy for children with diarrhea consists of: prevention of dehydration through early administration of appropriate fluids available in the home; treatment of dehydration with ORS solution; treatment of severe dehydration with an intravenous electrolyte solution; continued feeding during, and increased feeding after the diarrheal episode; and selective use of antibiotics and nonuse of antidiarrheal drugs. The WHO/UNICEF formula is also suitable as a maintenance fluid when given with equal amounts of water, breast milk, or low carbohydrate juice. Despite the unquestioned success of ORT in developing countries, physicians in the United States, the United Kingdom, and other industrialized countries have been slow to adopt ORT. Guidelines for case management call for patient assessment. The physician evaluating a child with diarrhea should inquire about clinical features including its duration and the presence of blood in the stool. Thus, a reliable treatment plan can be made without need of laboratory tests. Most diarrheal episodes are self-limited and do not benefit from antimicrobial therapy. Children with bloody diarrhea should be treated for suspected shigellosis with an oral antibiotic.^ieng

Rice-based oral rehydration solution for treating diarrhoea.

BACKGROUND: Oral rehydration therapy is used to treat dehydration caused by diarrhoea. However the rehydration solution does not reduce stool loss or length of illness. A solution able to do this may lessen the use of ineffective diarrhoea treatments as well as improve morbidity and mortality related to diarrhoea. OBJECTIVES: The objective of this review was to assess the effects of rice-based oral rehydration salts solution compared with glucose-based oral rehydration salts solution on reduction of stool output and duration of diarrhoea in patients with acute watery diarrhoea. SEARCH STRATEGY: We searched the Cochrane Infectious Diseases Group trials register, the Cochrane Controlled Trials Register, Medline, Embase, Lilacs and the reference lists of relevant articles. We also contacted researchers in the field. SELECTION CRITERIA: Randomized trials comparing standard World Health Organization oral rehydration solution with an experimental oral rehydration salts solution in which glucose (20 grams per litre) was replaced by 50-80 grams per litre of rice powder, with the electrolytes remaining unchanged. DATA COLLECTION AND ANALYSIS: Data were extracted independently by a statistician and a clinician. MAIN RESULTS: Twenty-two trials were included. Concealment of allocation was adequate in 15 of these trials. Irrespective of age, people with cholera who were given rice oral rehydration salts solution had substantially lower rates of stool loss than those given oral rehydration salts solution in the first 24 hours. Mean stool outputs in the first 24 hours were lower by 67 millilitres/kg of body weight (weighted mean difference -67.4, 95% confidence interval -94.3 to -41.0) in children, and by 51 millilitres/kg of body weight (weighted mean difference -51.1, 95% confidence interval -65.9 to -36.3) in adults. The rate of stool loss in infants and children with acute non-cholera diarrhoea was reduced by only four millilitres/kg of body weight (weighted mean difference -4.3, 95% confidence interval -9.3 to 0.8). REVIEWER'S CONCLUSIONS: Rice-based oral rehydration appears to be effective in reducing stool output in people with cholera. This effect was not apparent in infants and children with non-cholera diarrhoea.

Oral maintenance of water-electrolyte and acid-base balance in cholera: a preliminary report.

PIP: A study was undertaken to determine whether the absorption of glucose from the normal small bowel also involves increased absorption of sodium and water. 9 adult males suffering from severe cholera were studied. They were divided into 2 groups, each of which received a different oral electrolyte solution, on an alternating schedule with control periods of intravenous fluid therapy. The solution formulae are tabulated. Balance data and study results are tabulated. The study shows that water and electrolytes were absorbed from both the glucose-electrolyte solutions studied. Increased content of glucose in the solution reduced the amount of fluid necessary to maintain the fluid balance. This study leads to a conclusion that orally-administered glucose-electrolyte solutions can be valuable in cholera management, especially in situations where intravenous fluids are insufficient or inappropriate or where personnel skilled in their administration are lacking.^ieng

Disseminated Curvularia infection. Additional therapeutic and clinical considerations with evidence of medical cure.

A previously reported case of cerebral infection due to Curvularia lunata is more fully described. Medical cure was apparently achieved after 30 months' treatment with amphotericin B. Success was achieved only when the drug was given in a dose of 40 mg, three times per week, and was continued for six months after enhanced computed tomographic scans no longer showed cerebral lesions. Immunologic studies suggested the infection was accompanied by an unexplained defect in cell-mediated immunity.

Impact of rice based oral rehydration solution on stool output and duration of diarrhoea: meta-analysis of 13 clinical trials.

OBJECTIVE: To define the benefit of rice oral rehydration salts solution in relation to the glucose based World Health Organisation oral rehydration salts solution for treating and preventing dehydration in patients with severe dehydrating diarrhoea. DESIGN: Meta-analysis using data from 13 available randomised trials that compared these two formulations. SUBJECTS: The studies compared 1367 patients with cholera, severe cholera-like diarrhoea, or acute non-cholera diarrhoea. 668 received the standard WHO solution and 699 the rice based solution. INTERVENTION: Each trial report was reviewed to determine patient eligibility, the number of patients who were randomised and the number of these excluded from analysis, details of the randomisation procedure, and the precise timing of the outcome measurements. MAIN OUTCOME MEASURES: Stool output during the first 24 hours; weighted estimates of the difference in mean stool output between treatments. RESULTS: The rice solution significantly reduced the rate of stool output during the first 24 hours by 36% (95% confidence interval 28 to 44%) in adults with cholera and by 32% (19 to 45%) in children with cholera. The rate of stool loss in infants and children with acute non-cholera diarrhoea was reduced by only 18% (6 to 30%). CONCLUSIONS: The benefit of rice oral rehydration salts solution for patients with cholera is sufficiently great to warrant its use in such patients. The benefit is considerably smaller for children with acute, noncholera diarrhoea and should be more precisely defined before its practical value can be judged.

PIP: This meta-analysis used data from 13 available randomized trials to compare 2 rehydration salts solutions. Specifically, it sought to define the benefit of rice oral rehydration salts in relation to the glucose-based WHO oral rehydration salts solution for treating and preventing dehydration in patients with severe dehydrating diarrhea. The studies compared 1367 patients with cholera, severe cholera-like diarrhea, or acute noncholera diarrhea; 668 received the standard WHO solution and 699 the rice based one. Each report was reviewed to determine patient eligibility, the number of patients who were randomized, and the number of these excluded from the analysis, details of the randomization procedure, and the precise timing of the outcome measurements. Stool output during the 1st 24 hours was measured and there were weighted estimates of the differences in mean stool output between treatments. The rice solution significantly reduced the rate of stool output during the 1st 24 hours by 36% (95% confidence interval 28-44%) in adults with cholera and by 32% (19-45%) in children with cholera. The rate of stool loss in infants and children with acute noncholera diarrhea was reduced by only 18% (6-30%). The benefit of rice oral rehydration salts solution for patients with cholera is sufficiently great to warrant its use in these patients. The benefit is considerably less for children with acute, noncholera diarrhea and should be more precisely defined before its practical value can be judge.