Vaginal microbiome of reproductive-age women.

The means by which vaginal microbiomes help prevent urogenital diseases in women and maintain health are poorly understood. To gain insight into this, the vaginal bacterial communities of 396 asymptomatic North American women who represented four ethnic groups (white, black, Hispanic, and Asian) were sampled and the species composition characterized by pyrosequencing of barcoded 16S rRNA genes. The communities clustered into five groups: four were dominated by Lactobacillus iners, L. crispatus, L. gasseri, or L. jensenii, whereas the fifth had lower proportions of lactic acid bacteria and higher proportions of strictly anaerobic organisms, indicating that a potential key ecological function, the production of lactic acid, seems to be conserved in all communities. The proportions of each community group varied among the four ethnic groups, and these differences were statistically significant [χ(2)(10) = 36.8, P < 0.0001]. Moreover, the vaginal pH of women in different ethnic groups also differed and was higher in Hispanic (pH 5.0 ± 0.59) and black (pH 4.7 ± 1.04) women as compared with Asian (pH 4.4 ± 0.59) and white (pH 4.2 ± 0.3) women. Phylotypes with correlated relative abundances were found in all communities, and these patterns were associated with either high or low Nugent scores, which are used as a factor for the diagnosis of bacterial vaginosis. The inherent differences within and between women in different ethnic groups strongly argues for a more refined definition of the kinds of bacterial communities normally found in healthy women and the need to appreciate differences between individuals so they can be taken into account in risk assessment and disease diagnosis.

Oral priming with Salmonella Typhi vaccine strain CVD 909 followed by parenteral boost with the S. Typhi Vi capsular polysaccharide vaccine induces CD27+IgD-S. Typhi-specific IgA and IgG B memory cells in humans.

Attenuated live oral typhoid vaccine candidate CVD 909 constitutively expresses Salmonella Typhi capsular polysaccharide antigen (Vi). A randomized, double-blind, heterologous prime-boost clinical study was conducted to determine whether immunity to licensed parenteral Vi vaccine could be enhanced by priming with CVD 909. Priming with CVD 909 elicited higher and persistent, albeit not significant, anti-Vi IgG and IgA following immunization with Vi, than placebo-primed recipients. Vi-specific IgA B memory (B(M)) cells were significantly increased in CVD 909-primed subjects. S. Typhi-specific LPS and flagella IgA B(M) cells were observed in subjects immunized with CVD 909 or with the licensed Vi-negative oral typhoid vaccine Ty21a. CVD 909-induced B(M) cells exhibited a classical B(M) phenotype (i.e., CD3(-)CD19(+)IgD(-)CD27(+)). This is the first demonstration of classical B(M) cells specific for bacterial polysaccharide or protein antigens following typhoid immunization. The persistent IgA B(M) responses demonstrate the capacity of oral typhoid vaccines to prime mucosally relevant immune memory.

Adjuvanted intranasal Norwalk virus-like particle vaccine elicits antibodies and antibody-secreting cells that express homing receptors for mucosal and peripheral lymphoid tissues.

BACKGROUND: Noroviruses cause significant morbidity and mortality from acute gastroenteritis in all age groups worldwide. METHODS: We conducted 2 phase 1 double-blind, controlled studies of a virus-like particle (VLP) vaccine derived from norovirus GI.1 genotype adjuvanted with monophosphoryl lipid A (MPL) and the mucoadherent chitosan. Healthy subjects 18-49 years of age were randomized to 2 doses of intranasal Norwalk VLP vaccine or controls 21 days apart. Study 1 evaluated 5-, 15-, and 50-µg dosages of Norwalk antigen, and study 2 evaluated 50- and 100-µg dosages. Volunteers recorded symptoms for 7 days after dosing, and safety was followed up for 180 days. Blood samples were collected for serological profile, antibody secreting cells (ASCs), and analysis of ASC homing receptors. RESULTS: The most common symptoms were nasal stuffiness, discharge, and sneezing. No vaccine-related serious adverse events occurred. Norwalk VLP-specific immunoglobulin G and immunoglobulin A antibodies increased 4.8- and 9.1-fold, respectively, for the 100-µg dosage level. All subjects tested who received the 50- or 100-µg vaccine dose developed immunoglobulin A ASCs. These cells expressed molecules associated with homing to mucosal and peripheral lymphoid tissues. CONCLUSIONS: The intranasal monovalent adjuvanted Norwalk VLP vaccine was well tolerated and highly immunogenic and is a candidate for additional study.

Relatedness of Vibrio cholerae O1/O139 isolates from patients and their household contacts, determined by multilocus variable-number tandem-repeat analysis.

The genetic relatedness of Vibrio cholerae O1/O139 isolates obtained from 100 patients and 146 of their household contacts in Dhaka, Bangladesh, between 2002 and 2005 was assessed by multilocus variable-number tandem-repeat analysis. Isolate genotypes were analyzed at five loci containing tandem repeats. Across the population, as well as within households, isolates with identical genotypes were clustered in time. Isolates from individuals within the same household were more likely to have similar or identical genotypes than were isolates from different households, but even within a household, isolates from different individuals often had different genotypes. When household contacts were sampled regularly for 3 weeks after the illness of the household index patient, isolates with genotypes related to the index patient appeared in contacts, on average, approximately 3 days after the index patient, while isolates with unrelated genotypes appeared in contacts approximately 6 days after. Limited data revealed that multiple isolates from the same individual collected within days of each other or even from a single stool sample may have identical, similar, or unrelated genotypes as well. Our results demonstrate that genetically related V. cholerae strains cluster in local outbreaks but also suggest that multiple distinct strains of V. cholerae O1 may circulate simultaneously within a household.

An in vivo expression technology screen for Vibrio cholerae genes expressed in human volunteers.

In vivo expression technology (IVET) has been widely used to study gene expression of human bacterial pathogens in animal models, but has heretofore not been used in humans to our knowledge. As part of ongoing efforts to understand Vibrio cholerae pathogenesis and develop improved V. cholerae vaccines, we have performed an IVET screen in humans for genes that are preferentially expressed by V. cholerae during infection. A library of 8,734 nontoxigenic V. cholerae strains carrying transcriptional fusions of genomic DNA to a resolvase gene was ingested by five healthy adult volunteers. Transcription of the fusion leads to resolvase-dependent excision of a sacB-containing cassette and thus the selectable phenotype of sucrose resistance (Suc(R)). A total of approximately 20,000 Suc(R) isolates, those carrying putative in vivo-induced fusions, were recovered from volunteer stool samples. Analysis of the fusion junctions from >7,000 Suc(R) isolates from multiple samples from multiple volunteers identified 217 candidate genes for preferential expression during human infection. Of genes or operons induced in three or more volunteers, the majority of those tested (65%) were induced in an infant mouse model. VC0201 (fhuC), which encodes the ATPase of a ferrichrome ABC transporter, is one of the identified in vivo-induced genes and is required for virulence in the mouse model.

CVD 908, CVD 908-htrA, and CVD 909 live oral typhoid vaccines: a logical progression.

Typhoid fever remains an important public health problem in many parts of the world. Despite the availability of oral Ty21a (Vivotif; Berna Biotech) and parenteral Vi polysaccharide vaccine (Typhim Vi; Aventis Pasteur), improved typhoid fever vaccines have been sought. These include a series of vaccine candidates developed at the Center for Vaccine Development, University of Maryland, based on attenuation of Salmonella enterica serovar Typhi by deletions in the aroC, aroD, and htrA genes. These vaccine candidates, designated "CVD 908," "CVD 908-htrA," and "CVD 909," have been developed and tested in volunteers with variable success. This review summarizes the clinical data that directed the logical progression of this vaccine development strategy.

Clinical responses to undiluted and diluted smallpox vaccine.

BACKGROUND: To evaluate the potential to increase the supply of smallpox vaccine (vaccinia virus), we compared the response to vaccination with 10(8.1), 10(7.2), and 10(7.0) plaque-forming units (pfu) of vaccinia virus per milliliter. METHODS: In this randomized, single-blind, prospective study, 680 adults who had not been previously immunized were inoculated intradermally with undiluted vaccine (mean titer, 10(8.1) pfu per milliliter), a 1:5 dilution, or a 1:10 dilution of vaccinia virus with use of a bifurcated needle, and the site was covered with a semipermeable dressing. Subjects were monitored for vesicle formation (an indicator of the success of vaccination) and adverse events for 56 days after immunization. RESULTS: Success rates did not differ significantly among the groups and ranged from 97.1 to 99.1 percent after the first vaccination. Both the undiluted and diluted vaccines were reactogenic. In addition to the formation of pustules, common adverse events included the formation of satellite lesions, regional lymphadenopathy, fever, headache, nausea, muscle aches, fatigue, and chills consistent with the presence of an acute viral illness. Generalized and localized rashes, including two cases of erythema multiforme, were also observed. CONCLUSIONS: When given by a bifurcated needle, vaccinia virus vaccine can be diluted to a titer as low as 10(7.0) pfu per milliliter (approximately 10,000 pfu per dose) and induce local viral replication and vesicle formation in more than 97 percent of persons.

Plant-based vaccines against diarrheal diseases.

Every year 1.6 million deaths occur due to diarrhea related to unsafe water and inadequate sanitation-the vast majority in children under 5 years old. Safe and effective vaccines against enteric infections could contribute to control of these diseases. However, purification of protective antigens for inclusion in vaccines using traditional expression systems is expensive and unattractive to vaccine manufacturers who see the vaccine market as economically uninviting. Cost is one of the persistent barriers to deployment of new vaccines to populations that need them most urgently. Transgenic plant-derived vaccines offer a new strategy for development of safe, inexpensive vaccines against diarrheal diseases. In phase 1 clinical studies, these vaccines have been safe and immunogenic without the need for a buffer or vehicle other than the plant cell. This paper describes early clinical studies evaluating oral transgenic plant vaccines against enteric infections such as enterotoxigenic E. coli infection and norovirus.

Plant-derived vaccines against diarrhoeal diseases.

Transgenic plant-derived vaccines offer a new strategy for the development of safe, inexpensive vaccines against diarrhoeal diseases. In animal and Phase I clinical studies, these vaccines have been safe and immunogenic without the need for a buffer or vehicle other than the plant cell. This review examines some early attempts to develop oral transgenic plant vaccines against enteric infections such as enterotoxigenic Escherichia coli infection, cholera and norovirus infection.

Cell-mediated immune responses in humans after immunization with one or two doses of oral live attenuated typhoid vaccine CVD 909.

CVD 909 is a novel live attenuated S. Typhi oral vaccine candidate derived from strain CVD 908-htrA which constitutively expresses Vi. Herein we investigated whether the genetic manipulations involved in modifying CVD 908-htrA altered its ability to induce potent T-cell immune responses (CMI) after a single dose (five subjects) and, in a separate trial, whether a second dose (eight subjects) further enhanced its immunogenicity. In these clinical trials we observed that CVD 909 immunization elicits a wide array of CMI, including cytotoxic T cells (CTL), IFN-gamma, TNF-alpha and IL-10 (but not IL-2, IL-4 or IL-5) production, and proliferation to S. Typhi antigens. However, the administration of a second dose did not result in increases in CMI. These results suggest that the genetic manipulations to constitutively express Vi did not adversely affect the ability of CVD 909 to elicit a wide array of CMI responses. These observations add impetus for the continuing evaluation of CVD 909 as a typhoid vaccine candidate.

Plant-derived vaccines against diarrheal diseases.

Transgenic plants present a novel system for both production and oral delivery of vaccine antigens. Production of protein antigen in food plants is substantially cheaper than production in bacterial, fungal, insect cell, or mammalian cell culture. Edible plants themselves can also serve as the oral vaccine delivery system. Phase-1 studies of raw transgenic potatoes expressing the B subunit of Escherichia coli heat labile enterotoxin (LT-B), potatoes expressing Norwalk virus capsid protein, and defatted corn germ meal expressing LT-B have been conducted. New oral vaccines based on other transgenic plants will soon be evaluated in humans.

Phase 1 safety and pharmacokinetic study of chimeric murine-human monoclonal antibody c alpha Stx2 administered intravenously to healthy adult volunteers.

Hemolytic-uremic syndrome (HUS) is a serious complication of infection by Shiga toxin-producing Escherichia coli. Shiga toxin type 2 (Stx2) is responsible for the renal toxicity that can follow intestinal infection and hemorrhagic colitis due to E. coli. A chimeric mouse-human antibody, designated c alpha Stx2, that has neutralizing activity in a mouse model was produced and tested in healthy adult volunteers. In this phase I dose escalation study, c alpha Stx2 was generally well tolerated. Pharmacokinetic studies indicated that clearance was stable over the dose range of 1.0 to 10 mg/kg of body weight (0.249 +/- 0.023 ml/kg/h) but was higher for the 0.1-mg/kg dose (0.540 +/- 0.078 ml/kg/h), suggesting saturable elimination. A similar nonlinear trend was observed for the volume of distribution, where average values ranged from 0.064 +/- 0.015 liter/kg for the 1.0- to 10-mg/kg doses and 0.043 +/- 0.005 for the 0.01-mg/kg dose. The relatively small volume of distribution suggests that the antibody is limited to the vascular (plasma) compartment. The mean half-life was 165 +/- 66 h, with lowest values observed for the 0.1-mg/kg dose (56.2 +/- 9.7 h) and the highest values reported for the 10.0-mg/kg dose (206.4 +/- 12.4 h). Future studies are needed to confirm the safety of this c alpha Stx2, and innovative clinical trials will be required to measure its efficacy in preventing or treating HUS.

Garden-variety vaccines: antigens derived from transgenic plants.

The discovery of new vaccines can result from deletion of virulence determinants from a specific pathogen or from identification of target antigens that stimulate a protective immune response. Vaccine development will become less empirical as applications of genomics, proteomics and reverse vaccinology are exploited, and new protective antigens will emerge for inclusion in the vaccines of the future. However, production and purification of these new antigens for oral and parenteral use using traditional expression systems, will be expensive and unattractive to vaccine manufacturers who see the vaccine market as economically uninviting. Cost is one of the persistent barriers to deployment of new vaccines to populations that need them most urgently. This factor will inhibit the development and distribution of safe and effective new vaccines against high priority pathogens.

Immunogenicity of recombinant LT-B delivered orally to humans in transgenic corn.

Previous clinical studies have demonstrated the feasibility of using edible transgenic plants to deliver protective antigens as new oral vaccines. Transgenic corn is particularly attractive for this purpose since the recombinant antigen is stable and homogeneous, and corn can be formulated in several edible forms without destroying the cloned antigen. Transgenic corn expressing 1 mg of LT-B of Escherichia coli without buffer was fed to adult volunteers in three doses, each consisting of 2.1 g of plant material. Seven (78%) of nine volunteers developed rises in both serum IgG anti-LT and numbers of specific antibody secreting cells after vaccination. Four (44%) of nine volunteers also developed stool IgA. Transgenic plants represent a new vector for oral vaccine antigens.

Immune responses to an oral typhoid vaccine strain that is modified to constitutively express Vi capsular polysaccharide.

Protection against typhoid fever might be best achieved by a vaccine that stimulates IgG antibody to Vi capsular polysaccharide (Vi) in serum, IgG antibody to O antigen in serum, and cell-mediated immune responses. Live typhoid vaccines have not elicited anti-Vi antibody, presumably because Vi expression is highly regulated. CVD 909 is an oral attenuated typhoid vaccine candidate that is engineered to constitutively express Vi. In the present study, CVD 909, at doses of 10(6-9) cfu, was orally administered to 32 healthy adults, and immune responses were measured. Although many of the volunteers generated antibody-secreting cell responses to Vi, only 2 of the 32 volunteers generated anti-Vi IgG antibody in serum.

Humoral, mucosal, and cellular immune responses to oral Norwalk virus-like particles in volunteers.

Norwalk virus-like particles (VLPs), made from recombinant capsid protein, are a promising vaccine. Thirty-six healthy adult volunteers received 250 microg (n = 10), 500 microg (n = 10), or 2000 microg (n = 10) of orally administered VLP or placebo (n = 6). All vaccinees developed significant rises in IgA anti-VLP antibody-secreting cells. Ninety percent who received 250 microg developed rises in serum anti-VLP IgG; neither the rates of seroconversion nor geometric mean titers increased at the higher doses. About 30-40% of volunteers developed mucosal anti-VLP IgA. Lymphoproliferative responses and IFN-gamma production were observed transiently among those who received 250 microg or 500 microg but not 2000 microg of VLP. Studies to increase immunogenicity using a mucosal adjuvant are planned.

Concomitant induction of CD4+ and CD8+ T cell responses in volunteers immunized with Salmonella enterica serovar typhi strain CVD 908-htrA.

Type 1 cell-mediated immunity might play an important role in protection from typhoid fever. We evaluated whether immunization with Salmonella enterica serovar Typhi (S. Typhi) strain CVD 908-htrA (a Delta aroC Delta aroD Delta htrA mutant), a leading live oral typhoid vaccine candidate, elicits specific CD4(+) and CD8(+) S. Typhi immune responses. Potent CTL responses and IFN-gamma secretion by CD8(+) T cells were detected following immunization with CVD 908-htrA in high (4.5 x 10(8) CFU) and low (5 x 10(7) CFU) dosages. S. Typhi-specific CTL were observed in six of eight vaccinees (four high and two low dose) after immunization. Mean increases in the frequency of IFN-gamma spot-forming cells (SFC) in the presence of S. Typhi-infected targets were 221 +/- 41 SFC/10(6) PBMC and 233 +/- 87 SFC/10(6) PBMC, in the high and low dose groups, respectively. Strong CD4(+) T cell responses were also observed. Increases in the IFN-gamma production to soluble S. Typhi flagella (STF) occurred in 82 and 38% of the volunteers who received the high and low doses, respectively. Robust correlations were observed between volunteers that responded with IFN-gamma SFC to stimulation with S. Typhi-infected cells and IFN-gamma released in response to stimulation with STF Ags (r = 0.822, p < 0.001) and between CTL and IFN-gamma production to STF (r = 0.818, p = 0.013). These data demonstrating the concomitant induction of both CD4- and CD8-mediated CMI are consistent with a significant role for type 1 immunity in controlling typhoid infection and support the continuing evaluation of CVD 908-htrA as a typhoid vaccine candidate.

Dose-dependent neutralizing-antibody responses to vaccinia.

To evaluate the humoral immune responses to smallpox-vaccine stocks currently available in the United States (Dryvax; Wyeth) and to generate data for comparison of responses to newly produced lots of smallpox vaccine, we evaluated dose-response effects, using undiluted and diluted smallpox vaccine. At 28 and 56 days after vaccination, serum samples were obtained from vaccinated subjects (N=674) who had participated in a randomized, single-blinded trial of an undiluted or a 1 : 5 or 1 : 10 dilution of smallpox vaccine and who subsequently were tested for plaque-reduction neutralizing-antibody titer. All subjects who developed a vesicle after vaccination also developed neutralizing antibodies by day 28. Subjects given either a 1 : 5 or 1 : 10 dilution of vaccinia had significantly higher neutralizing-antibody titers than did subjects given undiluted vaccine. Larger lesion size and fever after vaccination were associated with significantly higher neutralizing-antibody titers after vaccination.