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Biomedical subjects

M L Clements

Publications and source records attributed to M L Clements.

At least 109 records · Page 6Linked to original sources
PubMed1983

Recombinant DNA risk assessment studies in humans: efficacy of poorly mobilizable plasmids in biologic containment.

Recombinant DNA risk assessment studies quantitated the mobilizability of "safe" plasmid pBR325, in comparison with readily mobilizable plasmid pJBK5 (chloramphenicol and tetracycline resistant). Of 15 volunteers who became colonized after ingestion of 5 X 10(10) Escherichia coli HS-4, a normal human flora strain containing pJBK5 and daily oral tetracycline, nine manifested transfer of pJBK5 to normal flora by means of triparental mating. In contrast, none of 12 other volunteers cocolonized with HS-4 bearing "safe" pBR325 and normal flora showed transfer (P = 0.001), despite ingestion of tetracycline. To accomplish transfer directly, E coli HS-4 containing both pBR325 and a derepressed, conjugative plasmid (F-amp) was fed to two groups of volunteers. Transfer of pBR325 to normal flora occurred in 13 of 18 volunteers taking daily tetracycline but in none of eight who did not (P less than 0.002). Nor were transconjugants detected, despite tetracycline ingestion, in five volunteers who ingested and excreted E coli K12 (pBR325 plus F-amp).

Adult↗
PubMed1983

Serodiagnosis of Rocky Mountain spotted fever: comparison of IgM and IgG enzyme-linked immunosorbent assays and indirect fluorescent antibody test.

To characterize IgM and IgG antibody responses in Rocky Mountain spotted fever (RMSF), a microtiter enzyme-linked immunosorbent assay (ELISA) using density gradient-purified Rickettsia rickettsii as antigen was developed. Sera of vaccinated individuals and patients with RMSF were tested by ELISA and by indirect fluorescent antibody (IFA) tests. Diagnostic agreement between ELISA and the IFA test was 76% and 52% for IgG and IgM antibody, respectively. Diagnostic agreement between the ELISA for IgG antibody and the IFA test for total immunoglobulins was 84%. The ELISAs for IgM and IgG antibody were as specific (100%) and as sensitive (100%) as the IFA test (83%-100%) in detecting antibody increases in paired sera from persons with RMSF and were superior to the IFA test in detecting seroconversions in vaccinees. The ELISA also detected antibodies in a single convalescent-phase serum with sensitivity and reliability. The ELISA for IgG antibody is appropriate for seroepidemiology and serodiagnosis since it permits measurement of antibody at a single dilution of serum up to a year after illness.

Adult↗
PubMed1983

Reactogenicity, immunogenicity, and efficacy of a chick embryo cell-derived vaccine for Rocky Mountain spotted fever.

A new formalin-inactivated vaccine prepared by sucrose density gradient centrifugation of tissue culture-grown Rickettsia rickettsii was evaluated for safety and immunogenicity in a placebo-controlled, double-blind study. Most of the 52 seronegative adult vaccinees, 88% after the first and 66% after the second dose, experienced brief, mild (mostly local) reactions, but only 50% exhibited a systemic immune response to vaccination. Six unvaccinated volunteers (controls) and 16 of these vaccinees were challenged with R rickettsii one month after vaccination. Vaccine efficacy was 25%; all six controls and 12 of 16 vaccinees developed typical Rocky Mountain spotted fever. The incubation period was longer, the duration of constitutional symptoms shorter, and the height of fever lower in ill vaccinees than in controls. The vaccine provided only partial protection against Rocky Mountain spotted fever but ameliorated the illness.

Adolescent↗
PubMed1983

Dose response of A/Alaska/6/77 (H3N2) cold-adapted reassortant vaccine virus in adult volunteers: role of local antibody in resistance to infection with vaccine virus.

An attenuated influenza A candidate vaccine virus, derived from the A/Ann Arbor/6/60 (H2N2) cold-adapted (ca) donor virus and the A/Alaska/6/77 (H3N2) wild-type virus, was evaluated in adult seronegative volunteers (serum hemagglutination-inhibiting antibody titer, less than or equal to 1:8) for level of attenuation, infectivity, antigenicity, and genetic stability. Four groups with similar preinoculation mean titers of serum and nasal wash antibodies were inoculated intranasally with 10(4.5), 10(5.5), 10(6.5), or 10(7.5) 50% tissue culture infectious doses (TCID50) of the ca reassortant virus, and eight other seronegative adult volunteers received the wild-type virus. Only 2 of 66 vaccinees developed fever or mild and brief systemic or upper respiratory tract illness or both. Both volunteers with vaccine-related reactions received the highest dose (10(7.5) TCID50) of ca virus, which indicates that the vaccine retains some mild reactogenicity at a high dosage. In contrast, four of eight volunteers infected with the wild-type virus became ill. Each of the 54 isolates tested retained the temperature-sensitive phenotype of the vaccine virus. Thus, the ca reassortant was genetically stable and attenuated at 10(4.5) to 10(7.5) TCID50 for seronegative adults. The 50% human infective dose of ca virus was approximately 10(5.3) TCID50. Ten and one hundred 50% human infectious doses infected 73 and 83% of vaccinees, respectively, and approximately 75% developed an immunological response at these doses. The failure of the vaccine virus to infect some volunteers was correlated with the presence of pre-inoculation nasal wash immunoglobulin A hemagglutinin antibody.

Adult↗
PubMed1983

Hemagglutinin-specific antibody responses in immunoglobulin G, A, and M isotypes as measured by enzyme-linked immunosorbent assay after primary or secondary infection of humans with influenza A virus.

The isotype-specific antibody responses to purified hemagglutinin of adults undergoing either primary or secondary infection with an influenza A virus were characterized by using an enzyme-linked immunosorbent assay. Twenty-eight military recruits undergoing primary infection with A/USSR/92/77 (H1N1)-like virus had serum antibody rises in the immunoglobulin M (IgM) (86%), IgG (100%), and IgA (96%) isotypes. In contrast, 19 adult volunteers undergoing secondary infection with A/Peking/2/79 (H3N2) wild-type virus had serum antibody titer rises largely restricted to the IgG (68%) and IgA (74%) classes, with only 1 volunteer having a serum IgM antibody titer rise. Nasal wash hemagglutinin-specific antibody responses in the adults undergoing secondary infection were predominantly in the IgA class (74%). There was a correlation between the presence of and the magnitude of nasal wash and serum hemagglutinin-specific IgA antibody responses in these adults. This suggested that there was a common source for the hemagglutinin-specific local IgA antibody and serum IgA antibody produced after infection. The recruits undergoing primary H1N1 influenza virus infection had H1 hemagglutinin-specific enzyme-linked immunosorbent assay antibody in each of the IgA, IgG, and IgM isotypes in their acute-phase serum. However, no role for this cross-reactive antibody in modifying the severity of illness experienced by the recruits could be demonstrated.

Adult↗
PubMed1983

Immunogenicity of Ty21a attenuated "Salmonella typhi" given with sodium bicarbonate or in enteric-coated capsules.

Ty21a, a stable attenuated mutant of Salmonella typhi, is a safe, protective oral vaccine when 3 doses of 10(9) cells in saline are taken after neutralization of gastric acidity by 1 g NaHCO3. To identify a more convenient method to administer vaccine and to determine the feasibility of immunizing with a single dose, we studied the immune response of children and adults to different formulations of Ty21a with a newly developed, sensitive, enzyme-linked immunosorbent assay (ELISA). In this ELISA, a rise in S. typhi O antibody was defined as a change in net optical density of greater than or equal to 0.15 (more than 3 SD from the mean difference in optical density in a negative control population). Three hundred and thirty-five Chilean children were given 3 doses of 10(9) Ty21a in 150 ml of milk with 0.8 g NaHCO3 or in enteric-coated capsules. In each group, 5% seroconverted by Widal O but 41% by IgG ELISA O antibody titers; mean antibody levels by group were identical. Studies were also carried out in healthy college students in a non-endemic area (U.S.A.) who had no history of prior typhoid immunization. In total, 141 U.S. adults received vaccine formulated in either one of two ways: 1) in gelatin capsules administered with two additional gelatin capsules containing a total of 0.8 gm NaHCO3 or 2) in enteric-coated capsules. Thirty-six persons received one dose, 30 got two doses and 16 ingested three doses of enteric-coated vaccines, while 44 persons receiving one dose and 15 got two doses of vaccine in the gelatin capsule formulation. Rates of seroconversion of ELISA O antibody were similar in all the groups. Ty21a vaccine was not recovered from multiple stool, jejunal fluid or blood cultures of the U.S. vaccine recipients. Based on these observations a large-scale field trial of efficacy has been initiated in 90.000 schoolchildren 6-20 years of age in Santiago, Chile, of whom one-third received one dose of enteric-coated vaccine, one-third got two doses and the remainder received placebo.

Adolescent↗
PubMed1983

Exogenous lactobacilli fed to man - their fate and ability to prevent diarrheal disease.

Clinical and microbiologic studies were conducted to evaluate the capability of exogenous lactobacilli to implant in the upper small intestine, the ability of exogenous lactobacilli to prevent enterotoxigenic Escherichia coli (ETEC) diarrhea, and the effect of lactobacillus therapy in reduction of diarrhea due to neomycin. Microbiologic studies of jejunal aspirates indicated that orally ingested Lactobacillus acidophilus and L. bulgaricus in LactinexR and L. acidophilus in Infloran BernaR survived passage through the stomach and remained viable in the proximal small bowel for three to six hours in most, not all, individuals. Challenge studies with ETEC revealed that despite the ability of lactobacilli in LactinexR to persist in the upper small intestine for several hours, the lactobacillus preparation did not prevent or alter the course of ETEC diarrhea in adults. Lactobacillus therapy with one lot of LactinexR reduced the volume and duration of neomycin-associated diarrhea, whereas another lot of LactinexR had no therapeutic effect. Thus, lot to lot variations in lactobacillus preparations may account for some conflicting results observed with lactobacillus therapy for intestinal disorders.

Adolescent↗
PubMed1983

Texas Star-SR: attenuated "Vibrio cholerae" oral vaccine candidate.

Texas Star-SR, a laboratory-derived mutant of Vibrio cholerae El Tor Ogawa 3083, which produces B but not A subunit of cholera toxin was given to 68 healthy adult volunteers in doses of 10(5) to 5 X 10(10) organisms. 16 of 68 exhibited loose stools but in only one individual was stool volume notable. Vomiting occurred in 1 and abdominal cramps in 3 vaccines; malaise and fever were not seen. Texas star was recovered from stools of 22% who received low doses (10(5) or 10(6) organisms) and from 63% who received high doses (10(8), 10(10), 2 X 10(10) or 5 X 10(10)). The attenuated strain was also recovered from jejunal fluid of 76% in the high dose group; cultures revealed 10(2)-10(5) organisms/ml. Seroconversions of vibriocidal antibody occurred in 93% and peak organisms/ml. Seroconversions of vibriocidal antibody occurred in 93% and peak titers were resembling those seen following clinical cholera. In contrast, serum IgG ELISA antitoxin rose significantly in only 29% and levels were below those encountered after clinical cholera. Only 5 of 18 vaccinees tested so far had significant rises in intestinal SIgA antitoxin; these also manifested rises in serum antitoxin. The occurrence of loose stools did not correlate with dose ingested, excretion of vibrios or rise in serum antitoxin. 503 clones recovered from coprocultures and jejunal fluids were negative when tested for enterotoxin. One month following a single 5 X 10(10) organism dose of Texas Star, 7 vaccinees and 6 controls were challenged with 10(6) pathogenic El Tor Ogawa vibrios. Diarrhea occurred in 7 of 10 controls but in only 1 of 7 vaccinees (p = 0.05). Despite clinical protection, excretion of pathogenic V. cholerae was similar in vaccinated and control groups. Twelve vaccinees who received two 10(9) or two 2 X 10(10) organisms doses of Texas Star 1 week apart were challenged with 10(6) pathogenic V. cholerae El Tor of the heterologous serotype. Diarrhea occurred in 11 of 15 controls but in only 3 of 12 vaccinees (p. 0.01). The 3 vaccinees with diarrhea all had mild illness. Texas Star-SR is a prototype that commonly causes mild diarrheal responses but is genetically stable in vivo and stimulates protective immunity against challenge with either the homologous or heterologous serotype.

Adult↗
PubMed1982

The pathogenicity of nonenterotoxigenic Vibrio cholerae serogroup O1 biotype El Tor isolated from sewage water in Brazil.

Nonenterotoxigenic strains no. 1196-78 and no. 1074-78 of Vibrio cholerae serogroup O1 (biotype El Tor, serotype Ogawa) were isolated from sewage water in Brazil and fed to 20 volunteers. Neither strain caused diarrhea. None of the seven volunteers who ingested Ogawa strain no. 1074-78 (10(6) organisms) excreted the organism whereas eight of the 13 volunteers who ingested Ogawa strain no. 1196-78 (10(6) or 10(8) organisms) did excrete the organism in their stools. None of 114 stool-culture isolates yielded cholera enterotoxin, and none of the 20 volunteers had significant increases in serum titers of antitoxin as measured by enzyme-linked immunosorbent assay although six of the volunteers had slightly elevated vibriocidal antibody levels. Six volunteers used as controls and four volunteers who had stool cultures positive for strain no. 1196-78 of V. cholerae were challenged with pathogenic El Tor Ogawa strain no. E7946 (10(6) organisms) to determine if previous ingestion of the Brazilian strain would induce protective immunity. All 10 of the volunteers developed diarrhea, and the severity of the illness was similar in both groups.

Adult↗
PubMed1982

Magnitude, kinetics, and duration of vibriocidal antibody responses in North Americans after ingestion of Vibrio cholerae.

Sera from 147 volunteers were examined for vibriocidal antibody by the tube-dilution method before and after they ingested 10(3)-10(6) Vibrio cholerae organisms. Titers increased significantly after challenge in 97% of 110 persons who excreted V. cholerae. In 12% of the bacteriologically confirmed infections, the titer increased significantly only to the homologous (Inaba or Ogawa) serotype. Levels of vibriocidal antibody decreased substantially between one and six months after challenge, but they usually remained elevated over base-line values. Levels of antitoxin to V. cholerae were measured by IgG enzyme-linked immunosorbent assay (ELISA), rabbit skin permeability tests, and adrenal cell techniques in 73 pairs of prechallenge and postchallenge sera. Results of the vibriocidal assay agreed most closely with those of the ELISA, the most sensitive antitoxin assay, in serologically detecting clinical and subclinical infections. Recent infection could be accurately serodiagnosed by levels of vibriocidal antibody and antitoxin (by IgG ELISA) in a convalescent-phase serum.

Adolescent↗
PubMed1982

Evaluation of a phenotypic revertant of the A/Alaska/77-ts-1A2 reassortant virus in hamsters and in seronegative adult volunteers: further evidence that the temperature-sensitive phenotype is responsible for attenuation of ts-1A2 reassortant viruses.

In a previous study, a seronegative child to whom attenuated A/Alaska/77-ts-1A2 virus was administered (37 degrees C shutoff temperature for plaque formation) shed virus with an altered temperature-sensitive (ts) phenotype (40 degrees C shutoff temperature) (Murphy et al., Ann. N.Y. Acad. Sci. 354:172-182, 1980; Tolpin et al., Virology 112:505-517, 1981). This ts+ virus (FV1319) was evaluated for its level of replication in hamsters and for its virulence for humans. In hamsters, FV1319 ts+ virus replicated to the same level in the nasal turbinates as that of which the A/Alaska/77 wild-type virus replicated, but its replication in the lungs was reduced 40-fold. In contrast, the A/Alaska/77-ts-1A2 reassortant achieved a titer in hamster nasal turbinates that was significantly lower (P less than 0.005) than those achieved by the wild-type and the FV1319 viruses; the A/Alaska/77-ts-1A2 reassortant was not recoverable from the lungs. In seronegative adult volunteers, the pattern of replication of the FV1319 virus was similar to that of the A/Alaska/77 wild-type virus. The illness induced by the FV1319 ts+ virus was also similar to that caused by the wild-type virus. In contrast, the A/Alaska/77-ts-1A2 reassortant was satisfactorily attenuated in adult volunteers. These results suggest that attenuation of the A/Alaska/77-ts-1A2 reassortant virus in humans is a function of the ts phenotype: loss of this phenotype restored virulence. The ability of the A/Alaska/77-ts-1A2 reassortant to lose its ts phenotype and regain virulence during growth in a permissive host limits the usefulness of the ts-1A2 reassortants as vaccine viruses for humans.

Animals↗
PubMed1982

Reactogenicity, immunogenicity and efficacy studies of Escherichia coli type 1 somatic pili parenteral vaccine in man.

Purified type 1 somatic pili from enterotoxigenic Escherichia coli (ETEC) strain H10407 (O78:H11) was evaluated as a parenteral immunizing agent in the hope that this antigen might enhance a contemplated polyvalent pilus vaccine. Intramuscular inoculation with 45, 90, 900 or 1 800 mcg of pili vaccine was tolerated without incident in 82 volunteers. Six of 15 persons who received a 28 day booster of 1 800 mcg developed local reactions while none of 52 persons receiving 180 or 450 mcg boosters evinced such reactions. Pili vaccine did not significantly alter intestinal transit time, absorptive capacity or the prevalence of colonic E. coli bearing type 1 somatic pili of the H10407 antigenic variety. All vaccinees developed significant rises in circulating IgG antibody to type 1 somatic pili, the magnitude of the response being directly proportioned to the vaccine dose. None of the vaccinees had significant rises to CFA I or II pili nor to heat-labile enterotoxin. However, many had rises in O antibody, particularly among those inoculated with 1 800 mcg. Three challenge studies were carried out with E. coli H10407 to assess vaccine efficacy. In the initial study the vaccinees were either protected against diarrhea (2 of 6 vaccinees versus 7/7 of controls) or had milder disease than the controls. In two subsequent challenges with H10407 significant protection was not seen. It was not clear whether protection exhibited by the vaccinee group in the first challenge was due to O antibody, pili antibody, or both acting synergistically. To clarify this, a group of the immunized volunteers were challenged with ETEC strain B7A which is a different serotype (O148:H28) lacks CFA/I or II pili, but possesses type 1 somatic pili antigenically distantly related to those of H10407. Attack rates and severity of illness were similar in both vaccinee and control groups. While most volunteers challenged with E. coli H10407 developed significant rises in circulating antibody to CFA/I, LT and O antigen, none had rises to type 1 somatic pili. It is unclear if this is due to immune tolerance to this antigen when encountered enterally or whether these pili are not present in vivo in ETEC initiating diarrhea in the proximal small intestine. In summary, parenterally inoculated type 1 somatic pili were safe and highly immunogenic in man but did not consistently induce protection. Further studies are planned to clarify the role of antibody to type 1 somatic pili in mediating protection.

Adult↗
PubMed1981

Duration of infection-derived immunity to cholera.

Four volunteers were rechallenged with Vibrio cholerae (10(6) classical Ogawa 395 organisms) 33-36 months after their initial induced cholera infection; none of the four veterans and four of five control volunteers developed diarrhea (P = 0.04). All control subjects, but only one veteran, had positive coprocultures. Three of the four veterans had significant levels of serum IgG antitoxin before challenge, but none had measurable intestinal levels of secretory IgA antitoxin. Significant rises in levels of serum vibriocidal and antitoxic antibody occurred in all control subjects and in two veterans, who also manifested rises in levels of intestinal secretory IgA antitoxin. The impressive duration of infection-derived immunity suggests that the most promising approach to development of cholera vaccines may be to mimic natural immunity with orally administered, attenuated strains of V. cholerae.

Antibodies, Bacterial↗
PubMed1981

Lactobacillus prophylaxis for diarrhea due to enterotoxigenic Escherichia coli.

In vitro and animal experiments indicated that lactobacilli might prevent Escherichia coli from colonizing the intestine and may produce substances counteracting enterotoxin. Lactinex, a commercial preparation of dried Lactobacillus acidophilus and L. bulgaricus, is marketed for uncomplicated diarrhea. Preliminary experiments in nonfasting volunteers indicated that lactobacilli in this preparation colonized the small intestine for up to 6 h. To evaluate the protective efficacy of Lactinex, a double-blind randomized study was carried out in which 48 volunteers (23 receiving Lactinex and 25 receiving placebos) were challenged with E. coli strains that produced heat-stable or heat-labile enterotoxins or both. No significant differences between the two groups were noted with respect to attack rate, incubation period, duration of diarrhea, volume and number of liquid stools, and coproculture yields. These data suggest that this lactobacillus preparations does not prevent or alter the course of enterotoxigenic E. coli diarrhea in adults. Lack of efficacy occurred despite efforts to maximize small bowel colonization, including administration of Lactinex in milk and in a 6-hour-interval regimen during 36 h before and 96 h after challenge.

Adolescent↗
PubMed1981

Evaluation of A/Alaska/6/77 (H3N2) cold-adapted recombinant viruses derived from A/Ann Arbor/6/60 cold-adapted donor virus in adult seronegative volunteers.

The influenza A/Ann Arbor/6/60 (H2N2) cold-adapted (ca) virus was evaluated as a donor of attenuating genes to new variants of influenza A virus. This ca donor virus was mated with the A/Alaska/6/77 (H3N2) wild-type virus, and three A/Alaska/6/77 (H3N2) ca recombinant viruses were produced. The parental origin of the genes in the three ca recombinants had been determined previously (2), and their virulence for adult seronegative volunteers was assessed in the present study to identify the genes present in the ca donor virus that confer attenuation. Each of the recombinants received the hemagglutinin and neuraminidase genes from the A/Alaska/6/77 (H3N2) wild-type parent. One ca recombinant (CR-29) received all six transferable genes from the ca parent and was found to be satisfactorily attenuated in the volunteers. The two other ca recombinants received five of the six transferable genes with a wild-type gene at the M or NS locus. The pattern of infection in humans with these latter two ca recombinants was similar to the CR-29 ca recombinant. These findings demonstrate that inheritance of a gene in ca recombinants at the M or NS locus segregates independently of attenuation and suggest that the M and NS genes present in the ca donor virus are not the major determinants of attenuation conferred by this virus.

Antibodies, Viral↗