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Biomedical subjects

M M Levine

Publications and source records attributed to M M Levine.

At least 145 records · Page 8Linked to original sources
PubMed1993

Colonization by enteroaggregative Escherichia coli in travelers with and without diarrhea.

Enteroaggregative Escherichia coli (EAggEC) has been found to be associated with pediatric diarrhea in developing countries. In order to determine the role of EAggEC as an agent of traveler's diarrhea, we used a sensitive and specific DNA probe for EAggEC to screen bacterial colony blots from 278 volunteers before and after travel. Colonization with EAggEC was infrequent (2.5%) prior to travel but rose to 27 to 33% after travel in volunteers who took either placebo or trimethoprim-sulfamethoxazole. Travelers who took trimethoprimsulfamethoxazole were colonized with organisms that were uniformly resistant to that antimicrobial agent; when volunteers received ciprofloxacin, colonization with EAggEC was prevented (2.0%). Although colonization rates were high in the placebo and trimethoprim-sulfamethoxazole groups, only a minority of travelers who were colonized with EAggEC experienced diarrhea. On the basis of our data, we suggest that colonization with EAggEC alone is not sufficient to cause traveler's diarrhea.

Adult↗
PubMed1993

Characterization of enterotoxigenic Escherichia coli isolated from U.S. troops deployed to the Middle East.

Enterotoxigenic Escherichia coli (ETEC) was a common cause of traveler's diarrhea in U.S. soldiers in the Middle East in 1989 and 1990. To determine which bacterial components would be useful in a vaccine, potential protective antigens (toxin, colonization factor antigen [CFA], and serotype) from 189 ETEC isolates were examined. Nearly half of the isolates expressed both ETEC toxins, 39% had only heat-stable enterotoxin (ST), and 17% had heat-labile enterotoxin (LT). CFA/I was the least common colonization factor antigen (11%), CFA/II was common (34%), as was CFA/IV (31%), and 24% expressed none of these CFAs. Fifty-seven O:H serotypes were found. Serotype O6:H16 was the most common, occurring in 29% of the ETEC isolates, usually with LT-ST and CFA/II. Generally, CFA/II was associated with expression of both toxins, CFA/IV was associated with expression of ST, and none of the CFAs was routinely found with LT. We conclude that ETEC from soldiers in the Middle East expressed a variety of antigens and that an effective vaccine will require multiple protective antigens.

Antigens, Bacterial↗
PubMed1993

Role of the eaeA gene in experimental enteropathogenic Escherichia coli infection.

Enteropathogenic Escherichia coli (EPEC) infections are a leading cause of infant diarrhea in developing countries. Recently eaeA, a gene necessary for the characteristic intimate attachment of EPEC to epithelial cells in tissue culture, was described. We conducted a randomized, double-blind study to determine the role of the eaeA gene in human EPEC infection. 11 adult volunteers ingested 2 x 10(10) colony-forming units of O127:H6 EPEC strain E2348/69, and an equal number received the same dose of an isogenic eaeA deletion mutant constructed from E2348/69. Volunteers were monitored for the development of diarrhea, fever, and systemic and gastrointestinal complaints. Diarrhea developed in all 11 volunteers who received E2348/69 and in 4 of 11 who received the mutant (P = 0.002). Fever was more common in recipients of the wild-type strain (P = 0.024). Stool volumes were lower in recipients of the mutant. All volunteers seroconverted to E2348/69 LPS, but the geometric mean peak titers of serum IgG and IgA in recipients of the mutant were lower than those of recipients of the wild-type strain. IgA against LPS was detected in the jejunal fluid of six of six recipients of E2348/69 and 5/6 recipients of the mutant. This study unambiguously assigns a role for eaeA as an EPEC virulence gene, but the residual diarrhea seen in recipients of the mutant indicates that other factors are involved.

Adhesins, Bacterial↗
PubMed1993

Vaccines to prevent bacterial enteric infections in children.

Considerable progress has been made in the last decade in developing vaccines against the most important bacterial enteric infections. Two new vaccines against typhoid fever (oral Ty21a and parenteral Vi polysaccharide) have been licensed in many countries. Newer generations of more sophisticated typhoid vaccines are undergoing clinical testing including recombinant attenuated S typhi strains and Vi polysaccharide-carrier protein conjugate vaccines. Two inactivated oral cholera vaccines, consisting of inactivated V cholerae 01 bacteria alone or in combination with the B subunit of cholera toxin, each conferred 50% to 53% protection over 3 years in a field trial in Bangladesh where subjects were immunized with a three-dose regimen. An engineered live oral cholera vaccine, strain CVD 103-HgR, has been shown in extensive clinical trials to be well tolerated by children and adults in developing countries and highly immunogenic following administration of just a single oral dose; a large-scale field trial of the efficacy of this vaccine is underway. Several candidate vaccines against Shigella and enterotoxigenic E coli are in clinical trials.

Bacterial Infections↗
PubMed1993

Production of monoclonal antibodies to Vi polysaccharide antigen of Salmonella typhi.

Twenty-four Vi antigen-specific monoclonal antibodies were produced in this study. The MAbs were found to be highly specific to Vi possessing bacteria. Selected MAbs were used in a direct agglutination assay for rapid identification of S. typhi in primary bacterial culture and also used to develop an assay to detect Vi antigen in clinical specimens. The result showed that they could not detect the antigen in urine and serum from acute patients even they could detect as low as 0.02 micrograms/ml of Vi antigen added in normal urine. The study has shown that these MAbs are very useful for rapid identification of S. typhi in primary bacterial culture and they can replace polyclonal anti-Vi antibodies which have been used routinely in bacteriological laboratories.

Agglutination Tests↗
PubMed1992

Impact of Haemophilus influenzae type b polysaccharide-tetanus protein conjugate vaccine on responses to concurrently administered diphtheria-tetanus-pertussis vaccine.

OBJECTIVE: To assess whether serum antibody responses to diphtheria-tetanus-pertussis (DTP) vaccine were affected by coadministration of Haemophilus influenzae type b capsular polyribosylribitol phosphate polysaccharide-tetanus protein (PRP-T) conjugate vaccine when given to patients at 2, 4, and 6 months of age. DESIGN: Randomized, double-blind clinical trial. SETTING: Urban Santiago, Chile. PATIENTS: Healthy infants assembled from health centers. Two hundred seventy-eight (74%) of 375 eligible infants participated; 222, who complied with the complete protocol, constituted the primary group under analysis. INTERVENTIONS: One of three vaccine regimens was given to study participants at 2, 4, and 6 months of age, either DTP mixed in the same syringe as PRP-T (group 1); DTP and PRP-T given at separate injection sites (group 2); or DTP without PRP-T (group 3). PRIMARY OUTCOME MEASURES: Titers of serum antidiphtheria toxoid, antitetanus toxoid, and pertussis agglutinin antibodies were measured in blood samples taken from patients 2 months after each dose. RESULTS: Serum antidiphtheria toxoid and antitetanus toxoid responses showed no important depressions in the patients receiving PRP-T. In contrast, geometric mean titers (GMTs) of pertussis agglutinins, expressed as reciprocal serum dilutions, after both the second and third doses (GMT2, GMT3) were lowest in group 1 (GMT2 = 89; GMT3 = 1230), intermediate in group 2 (GMT2 = 123; GMT3 = 1995), and highest in group 3 (GMT2 = 210; GMT3 = 3090; P less than .05 for trend group 1 less than group 2 less than group 3 after each dose). Antipertussis toxin and antipertussis filamentous hemagglutinin antibody titers also were depressed in patients who received PRP-T. Follow-up of a subset at 18 months revealed an expected decline of pertussis agglutinin titers to near baseline levels in each group. CONCLUSIONS: Concurrent administration of PRP-T vaccine with DTP vaccine, either in the same syringe or at different sites, interfered with antipertussis responses to a primary series of immunizations. Although the clinical significance of this antagonism is uncertain, these data underscore the caution required in decisions to add new vaccines to existing immunization regimens.

Antibodies, Bacterial↗
PubMed1992

Plasmodium falciparum: in vitro characterization and human infectivity of a cloned line.

The culture-adapted NF54 isolate of Plasmodium falciparum was subjected in vitro to three sequential limiting dilution titrations and the resulting clone was given the designation CVD1. DNA sequence analysis of the gene encoding the circumsporozoite (CS) protein revealed differences between CVD1 and the published NF54 CS gene. CVD1 had 1191 bp, 397 amino acids, and 42 repeat units while NF54 had 1218 bp, 405 amino acids, and 44 repeat units. The CVD1 clone was more sensitive to chloroquine than was the parental line, in vitro. Anopheles stephensi mosquitoes were infected equally by the cloned and uncloned parasites. Volunteers were readily infected by NF54 and CVD1 following infectious mosquito bites. The availability of a well-characterized, chloroquine-sensitive clone which safety infects humans should facilitate performance of experimental challenge studies to assess vaccine efficacy.

Amino Acid Sequence↗
PubMed1992

Safety and immunogenicity in volunteers of a recombinant Plasmodium falciparum circumsporozoite protein malaria vaccine produced in Lepidopteran cells.

A recombinant Plasmodium falciparum circumsporozoite (CS) antigen (rPfCSA) was produced in insect cells using a baculovirus expression vector containing the entire CS gene. This near full-length CS antigen was adsorbed onto aluminium phosphate for use as a malaria vaccine. In a study of safety and immunogenicity, 20 volunteers were divided into four groups of five each and inoculated intramuscularly with 10, 100, 500 or 1000 micrograms of vaccine. Primary vaccinations were followed by two booster immunizations at 2 and 6 months. Three volunteers developed prominent local reactions manifested as tenderness, redness and swelling at the injection site following the second or third vaccination. All symptoms resolved spontaneously within 72 h. Postimmunization sera from six of 20 volunteers showed seroconversions as measured by Western blot, using rPfCSA as antigen. However, specific anti-CS protein antibody could not be detected by indirect immunoflourescence against intact sporozoites or by ELISA using rPfCSA or peptide to the repeat region. In addition, 18 of 20 volunteers developed antibody to baculovirus proteins as determined by ELISA and/or Western blot. Antigen-driven replication studies using peripheral blood mononuclear cells from vaccinees failed to detect proliferative responses specific to CS protein. This recombinant CS protein vaccine, as formulated, was minimally immunogenic in humans.

Adult↗
PubMed1992

Initial safety and immunogenicity studies of an oral recombinant adenohepatitis B vaccine.

Orally administered adenovirus may be a useful vaccine carrier of cloned antigens of other pathogens. A recombinant adenohepatitis vaccine Wy-Ad7HZ6-1, which expressed hepatitis B surface antigen and contained a large deletion in early region 3 (E3), was constructed and studied in humans. Volunteers received Wy-Ad7HZ6-1 (n = 3), adenovirus type 7 vaccine (n = 3) or placebo (n = 3). Recipients of Wy-Ad7HZ6-1 shed less vaccine virus in the stool for a shorter period and had a lower titre of anti-adenovirus type 7 antibodies than recipients of the adenovirus 7 vaccine. None of the three Wy-Ad7HZ6-1 vaccinees developed antibody to hepatitis B surface antigen after this one dose primary immunization regimen. The E3 region may be required for optimal enteric growth of adenovirus-vectored vaccines.

Adenoviruses, Human↗
PubMed1992

Clinical acceptability and immunogenicity of CVD 908 Salmonella typhi vaccine strain.

An attenuated Salmonella typhi strain has been sought as an improved oral typhoid vaccine and as a carrier of protective antigens of other pathogens to make hybrid vaccines. Ideally, such a strain would be safe and induce protective immune responses after a single oral dose. CVD 908 is a mutant of S. typhi wild-type strain Ty2 with recombinant deletions in two genes, aroC and aroD. In phase 1 testing to date, this strain has not produced febrile responses or other significant adverse reactions in adult volunteers given doses of 5 x 10(4) to 5 x 10(7) organisms with sodium bicarbonate. In addition, after just a single oral dose of 5 x 10(7) colony-forming units, this strain induced IgG seroconversion to S. typhi lipopolysaccharide in 83% of vaccinees and stimulated specific IgA-secreting gut-derived lymphocytes in 100% of vaccinees. CVD 908 is a new oral typhoid vaccine that should be further investigated as a carrier for expressing foreign antigens in recombinant vaccine constructs.

Administration, Oral↗
PubMed1992

Tissue culture-adherent Escherichia coli in infantile diarrhea.

To determine the association of tissue culture-adherent Escherichia coli with diarrhea, serotyped E. coli strains isolated in a yearlong case-control study of infantile diarrhea in Bangkok, Thailand, were examined for adherence to HeLa cells and for hybridization with the enteropathogenic E. coli adherence factor, the F1845, and the enteroaggregative E. coli (EAggEC) DNA probes. E. coli that adhered to HeLa cells in a localized adherence (LA) pattern (LA E. coli) was isolated from 26 of 509 infants with diarrhea (cases) and 9 of 509 age-matched controls (P = .006); E. coli with diffuse or aggregative adherence (DA or AA) to HeLa cells or that hybridized with the F1845 or EAggEC probes was not associated with infantile diarrhea. LA E. coli of classical enteropathogenic E. coli (EPEC) serotypes was isolated from 11 cases and 1 control (P = .003). EPEC O44:H18 that adhered to HeLa cells in a DA pattern and hybridized with the F1845 DNA probe was the predominant E. coli (five of five colonies tested) isolated from a 5-month-old girl with diarrhea in whom no other enteric infections were identified. Although LA E. coli was highly associated with infantile diarrhea, the role of DA and AA E. coli was uncertain in this setting.

Bacterial Adhesion↗
PubMed1992

Age-specific prevalence of serum antibodies to the invasion plasmid and lipopolysaccharide antigens of Shigella species in Chilean and North American populations.

Shigella species have virulence plasmids that encode outer membrane proteins (invasion plasmid antigens, Ipa) associated with pathogenicity. Western blots were used to detect antibodies to Ipa in sera from 390 Chilean children, and these responses were compared with those of a US population of infants and adults. Antibodies to lipopolysaccharide (LPS) of Plesiomonas shigelloides and Shigella flexneri 2a were measured by ELISA. Among the Chileans, there was an age-related acquisition of Ipa antibodies, with 28% of 1-year-olds and 100% of children greater than or equal to 10 years showing positive responses. In contrast, none of the US infants and only 38% of the adults had antibodies to Ipa. Levels of LPS antibodies were also found to increase in an age-related manner among the Chileans. These results corroborate findings of previous epidemiologic studies which show that Shigella infections are endemic in Chile, as in other developing countries. The measurement of Ipa and LPS antibodies is a useful seroepidemiologic tool for investigating previous exposure to Shigella species in populations.

Adolescent↗
PubMed1992

Onset and duration of protective immunity in challenged volunteers after vaccination with live oral cholera vaccine CVD 103-HgR.

CVD 103-HgR is a live oral cholera vaccine that, in phase I and II studies to date, has been well tolerated and immunogenic. In challenge studies of US volunteers conducted 4-5 weeks after vaccination, CVD 103-HgR provided significant protection against experimental cholera due to classical and El Tor Vibrio cholerae O1. To determine the onset and duration of protection, two volunteer challenge studies were conducted: the first, 6 months after vaccination and the second, 8 days after vaccination. In both studies, CVD 103-HgR was 100% protective against diarrhea and significantly reduced the rate of shedding of vibrios after challenge with V. cholerae classical Inaba strain 569B, the virulent parent strain of CVD 103-HgR. Previously vaccinated subjects were less likely than naive controls to develop rises in titer of vibriocidal antibodies after challenge (P = .002), and the mean peak titer of vibriocidal antibodies was less than among controls. CVD 103-HgR can provide homologous protective immunity as soon as 8 days after vaccination and protection can persist for at least 6 months.

Administration, Oral↗
PubMed1992

An analysis of the quantitative relationship between oral temperature and severity of illness in experimental shigellosis.

The relationship between oral temperature and other parameters of illness was examined in 139 adult volunteers infected experimentally with Shigella sonnei. In subjects developing clinical disease, peak temperature correlated positively with total number of signs and symptoms other than fever (rxy = .71, P < .001), stool volume (rxy = .41, P < .001) and number of stools produced during the illness (rxy = .46, P < .001). Peak temperature correlated negatively with incubation period (rxy = -.34, P = .007) but exhibited no apparent correlation with duration of illness. The average oral temperature during illness correlated positively with number of other signs and symptoms of infection but not with stool volume or stool number. These results suggest that in clinical investigations involving S. sonnei, and perhaps with other pathogenic microorganisms, oral temperature is a useful quantitative marker for estimating disease severity.

Adult↗
PubMed1992

Safety and immunogenicity in North Americans of a single dose of live oral cholera vaccine CVD 103-HgR: results of a randomized, placebo-controlled, double-blind crossover trial.

We conducted a double-blind, placebo-controlled, randomized crossover study to evaluate the safety and immunogenicity of a single 5 x 10(8)-CFU dose of live oral recombinant cholera vaccine CVD 103-HgR in 94 North American adults. The vaccine was well tolerated without associated adverse reactions. Despite minimal fecal excretion of vaccine, 97% of subjects exhibited serum vibriocidal antibody and 72% had antitoxin responses.

Administration, Oral↗
PubMed1992

Studies with enteroaggregative Escherichia coli in the gnotobiotic piglet gastroenteritis model.

Two strains of enteroaggregative Escherichia coli of human origin fed to gnotobiotic piglets caused diarrhea or death in the majority of them. Histological examination revealed moderate hyperemia of the distal small intestine and cecum, swelling of small intestinal villi, and layers of aggregated bacteria stacked together in a mucus gel-like matrix overlying intact epithelium. These findings confirm that enteroaggregative E. coli strains produce distinctive intestinal lesions different from those caused by other major categories of diarrheagenic E. coli.

Animals↗
PubMed1992

Comparison of the safety and immunogenicity of delta aroC delta aroD and delta cya delta crp Salmonella typhi strains in adult volunteers.

Three attenuated Salmonella typhi strains have been constructed by introducing deletions in aroC and aroD or deletions in cya and crp into one of two wild-type parent strains, Ty2 or ISP1820. These mutant strains were designated CVD 906 (ISP1820 delta aroC delta aroD), CVD 908 (Ty2 delta aroC delta aroD), and chi 3927 (Ty2 delta cya delta crp). Two studies were conducted with 36 healthy adult inpatient volunteers to determine in a double-blind fashion the safety and immunogenicity of approximately 5 x 10(4) and 5 x 10(5) CFU of each of these three vaccine candidates given as a single dose. No statistically significant difference in the incidence of reactions among vaccinees was observed. Fever (oral temperature greater than or equal to 38.2 degrees C) occurred in 2 of 12 volunteers who received CVD 906, in 0 of 12 who received CVD 908, and in 1 of 12 who received chi 3927. Vaccine bacteremia without symptoms occurred in 1 of 12 vaccinees who received CVD 906, in 0 of 12 who received CVD 908, and in 2 of 12 who received chi 3927. Overall, 19 (53%) of 36 vaccinees developed immunoglobulin G antibody to S. typhi lipopolysaccharide after vaccination, with no statistically significant differences in the rate of seroconversion among volunteers in the three groups. We conclude that defined mutations in the aromatic biosynthetic pathway and in the cyclic AMP global regulatory system attenuate S. typhi. Mutant strains CVD 906, CVD 908, and chi 3927 are highly (and approximately equally) immunogenic but possibly differ in their propensity to induce fever. Further studies are needed to document the apparent relative safety of CVD 908 as a typhoid vaccine and as a vaccine carrier of foreign antigens.

Adolescent↗