Vaccine value profile for enterotoxigenic Escherichia coli (ETEC)

Enterotoxigenic Escherichia coli (ETEC) is one of the leading bacterial causes of diarrhoea, especially among children in low-resource settings, and travellers and military personnel from high-income countries. WHO's primary strategic goal for ETEC vaccine development is to develop a safe, effective, and affordable ETEC vaccine that reduces mortality and morbidity due to moderate-to-severe diarrhoeal disease in infants and children under 5 years of age in LMICs, as well as the long-term negative health impact on infant physical and cognitive development resulting from infection with this enteric pathogen. An effective ETEC vaccine will also likely reduce the need for antibiotic treatment and help limit the further emergence of antimicrobial resistance bacterial pathogens. The lead ETEC vaccine candidate, ETVAX, has shown field efficacy in travellers and has moved into field efficacy testing in LMIC infants and children. A Phase 3 efficacy study in LMIC infants is projected to start in 2024 and plans for a Phase 3 trial in travellers are under discussion with the U.S. FDA. Licensing for both travel and LMIC indications is projected to be feasible in the next 5-8 years. Given increasing recognition of its negative impact on child health and development in LMICs and predominance as the leading etiology of travellers' diarrhoea (TD), a standalone vaccine for ETEC is more cost-effective than vaccines targeting other TD pathogens, and a viable commercial market also exists. In contrast, combination of an ETEC vaccine with other vaccines for childhood pathogens in LMICs would maximize protection in a more cost-effective manner than a series of stand-alone vaccines. This 'Vaccine Value Profile' (VVP) for ETEC is intended to provide a high-level, holistic assessment of available data to inform the potential public health, economic and societal value of pipeline vaccines and vaccine-like products. This VVP was developed by a working group of subject matter experts from academia, non-profit organizations, public private partnerships, and multi-lateral organizations. All contributors have extensive expertise on various elements of the ETEC VVP and collectively aimed to identify current research and knowledge gaps. The VVP was developed using only existing and publicly available information.

Oral inactivated whole cell vaccine for mucosal immunization: ETVAX case study

Oral immunization is an effective strategy for inducing protective immunity against mucosal enteric pathogens. Although live-attenuated as well as subunit approaches have been explored for vaccination against enteric pathogens, inactivated whole bacterial cells may also be effective in introducing protective immunity. Successfully accomplishing this goal with inactivated whole bacterial cells will require that a complex antigenic repertoire be presented in controlled immunogenic amounts, in a safe and relatively simple and self-contained delivery format. The benefit from immunization with whole cell vaccines can be further enhanced through genetic engineering to over-express selected antigens and also by the use of mucosal adjuvants to direct a more robust immunologic response. These steps are being taken for the development of ETVAX, the most clinically advanced vaccine candidate against the major enteric pathogen, enterotoxigenic Escherichia coli (ETEC) with significant positive impact.

Controlled Human Infection Models To Accelerate Vaccine Development

The timelines for developing vaccines against infectious diseases are lengthy, and often vaccines that reach the stage of large phase 3 field trials fail to provide the desired level of protective efficacy. The application of controlled human challenge models of infection and disease at the appropriate stages of development could accelerate development of candidate vaccines and, in fact, has done so successfully in some limited cases. Human challenge models could potentially be used to gather critical information on pathogenesis, inform strain selection for vaccines, explore cross-protective immunity, identify immune correlates of protection and mechanisms of protection induced by infection or evoked by candidate vaccines, guide decisions on appropriate trial endpoints, and evaluate vaccine efficacy. We prepared this report to motivate fellow scientists to exploit the potential capacity of controlled human challenge experiments to advance vaccine development. In this review, we considered available challenge models for 17 infectious diseases in the context of the public health importance of each disease, the diversity and pathogenesis of the causative organisms, the vaccine candidates under development, and each model's capacity to evaluate them and identify correlates of protective immunity. Our broad assessment indicated that human challenge models have not yet reached their full potential to support the development of vaccines against infectious diseases. On the basis of our review, however, we believe that describing an ideal challenge model is possible, as is further developing existing and future challenge models.

Induction of mucosal and systemic immune responses against the common O78 antigen of an oral inactivated ETEC vaccine in Bangladeshi children and infants

We tested an oral enterotoxigenic Escherichia coli (ETEC) vaccine, ETVAX, consisting of inactivated E. coli overexpressing the most prevalent ETEC colonization factors (CFs) and a toxoid (LCTBA), in Bangladeshi children for capacity to induce mucosal and plasma immune responses against O78 lipopolysaccharide (LPS) expressed on the vaccine strains. The vaccine was given ± double-mutant heat-labile toxin (dmLT) adjuvant. We evaluated the impact of dmLT on anti-O78 LPS immune responses and whether such responses can predict responses against the CFs as a marker for vaccine "take". Two fractionated doses of ETVAX ± different amounts of dmLT were administered biweekly to groups of children 24-59 (n = 125), 12-23 (n = 97) and 6-11 (n = 158) months of age. Immune responses were evaluated in antibody in lymphocyte supernatants (ALS), fecal extracts and plasma. ALS IgA responses against O78 LPS were induced in 44-49% of the children aged 12-59 months. The magnitudes of the ALS responses were significantly higher in children receiving a half-dose (5 × 10¹⁰ bacteria) of ETVAX ± dmLT than in placebo recipients. <10% of the vaccinees aged 6-11 months mounted ALS responses against O78 LPS. However, 49% of the infants developed fecal secretory IgA responses which were significantly more frequent in those receiving a quarter-dose (2.5 × 10¹⁰ bacteria) of vaccine + dmLT (62%) compared to a quarter-dose alone (36%). Plasma IgA antibody responses were induced in 80% of older children and 36% of infants. The frequencies of O78 LPS responses in plasma and feces were comparable or higher than against the vaccine CFs in infants. Our findings show that ETVAX induced mucosal and systemic immune responses against O78 LPS in all age groups and that dmLT improved intestinal immune responses among infants. These observations may have implications for more successful use of other oral vaccines based on O antigens in children.

Functional antibodies and innate immune responses to WRSS1, a live oral Shigella sonnei vaccine candidate in Bangladeshi adults and children

Background

We demonstrated in a randomized placebo-controlled trial that WRSS1, a live oral Shigella sonnei vaccine candidate, is safe in Bangladeshi adults and children, and elicits antigen-specific antibodies. Here, we describe functional antibody and innate immune responses to WRSS1.

Methods

Adults (18–39 years) and children (5–9 years) received 3 doses of 3 × 10⁵ or 3 × 10⁶ colony forming units (CFU) of WRSS1 or placebo, 4 weeks apart; children additionally received 3 × 10⁴ CFU. Blood and stool were collected at baseline and 7 days after each dose. Functional antibodies were measured using serum bactericidal antibody (SBA) assay. Cytokine/chemokine concentrations were measured in lymphocyte cultures. Host defense peptides LL-37, HBD-1, and HD-5 were analyzed in plasma and stool.

Results

Children showed increased SBA titers over baseline after the third dose of 3 × 10⁶ CFU (P = .048). Significant increases of Th-17 and proinflammatory cytokines (TNF-α, G-CSF, MIP-1β), and reduction of anti-inflammatory and Th2 cytokines (IL-10, IL-13, GM-CSF) were observed in children. Plasma HBD-1 and LL-37 decreased in children after vaccination but were increased/unchanged in adults.

Conclusions

Functional antibodies and Th1/Th17 cytokine responses in children may serve as important indicators of immunogenicity and protective potential of WRSS1.

Clinical Trials Registration: NCT01813071.

A phase I trial of WRSS1, a Shigella sonnei live oral vaccine in Bangladeshi adults and children

Shigella sonnei live vaccine candidate, WRSS1, which was previously evaluated in US, Israeli and Thai volunteers, was administered orally to Bangladeshi adults and children to assess its safety, clinical tolerability and immunogenicity. In a randomized, placebo-controlled, dose-escalation, age-descending study, 39 adults (18-39 years) and 64 children (5-9 years) were enrolled. Each adult cohort (n = 13) received one dose of 3x10⁴, or three doses of 3 × 10⁵ or 3 × 10⁶ colony forming unit (CFU) of WRSS1 (n = 10) or placebo (n = 3). Each child cohort (n = 16) received one dose of 3x10³, or three doses of 3x10⁴, 3x10⁵, or 3 × 10⁶ CFU WRSS1 (n = 12) or placebo (n = 4). WRSS1 elicited mostly mild and transient reactogenicity events in adults and children. In the 3 × 10⁶ dose group, 50% of the adults shed the vaccine; no shedding was seen in children. At the highest dose, 100% of adults and 40% of children responded with a ≥ 4-fold increase of S. sonnei LPS-specific IgA antibody in lymphocyte supernatant (ALS). At the same dose, 63% of adults and 70% of children seroconverted with IgA to LPS, while in placebo, 33% of adults and 18% of children seroconverted. Both the vaccinees and placebos responded with fecal IgA to LPS, indicating persistent exposure to Shigella infections. In conclusion, WRSS1 was found safe up to 10⁶ CFU dose and immunogenic in adults and children in Bangladesh. These data indicate that live, oral Shigella vaccine candidates, including WRSS1 can potentially be evaluated in toddlers and infants (<2 years of age), who comprise the target population in an endemic environment.

Evaluation of the safety and immunogenicity of the oral inactivated multivalent enterotoxigenic Escherichia coli vaccine ETVAX in Bangladeshi adults in a double-blind, randomized, placebo-controlled Phase I trial using electrochemiluminescence and ELISA assays for immunogenicity analyses

The safety and immunogenicity of the second generation oral enterotoxigenic Escherichia coli (ETEC) vaccine ETVAX, consisting of inactivated recombinant E. coli strains over-expressing the colonization factors (CFs) CFA/I, CS3, CS5 and CS6 and the heat labile toxoid LCTBA, were evaluated in Bangladeshi volunteers. To enable analysis of antibody responses against multiple vaccine antigens for subsequent use in small sample volumes from children, a sensitive electrochemiluminescence (ECL) assay for analysis of intestine-derived antibody-secreting cell responses using the antibodies in lymphocyte secretions (ALS) assay was established using Meso Scale Discovery technology. Three groups of Bangladeshi adults (n = 15 per group) received two oral doses of ETVAX with or without double mutant LT (dmLT) adjuvant or placebo in the initial part of a randomized, double-blind, placebo-controlled, age-descending, dose-escalation trial. CF- and LTB-specific ALS and plasma IgA responses were analyzed by ECL and/or ELISA. ETVAX was safe and well tolerated in the adults. Magnitudes of IgA ALS responses determined by ECL and ELISA correlated well (r = 0.85 to 0.98 for the five primary antigens, P < 0.001) and ECL was selected as the ALS readout method. ALS IgA responses against each of the primary antigens were detected in 87-100% of vaccinees after the first and in 100% after the second vaccine dose. Plasma IgA responses against different CFs and LTB were observed in 62-93% and 100% of vaccinees, respectively. No statistically significant adjuvant effect of dmLT on antibody responses to any antigen was detected, but the overall antigenic breadth of the plasma IgA response tended to favor the adjuvanted vaccine when responses to 4 or more or 5 vaccine antigens were considered. Responses in placebo recipients were infrequent and mainly detected against single antigens. The promising results in adults supported testing ETVAX in descending age groups of children. ClinicalTrials.gov Identifier: NCT02531802.

Vaccines against Shigella and enterotoxigenic Escherichia coli: A summary of the 2016 VASE Conference

PATH hosted the inaugural Vaccines Against Shigella and Enterotoxigenic Escherichia coli (VASE) Conference in Washington, DC in June 2016, bringing together experts from around the world for a highly collaborative forum to discuss progress in the development of new enteric vaccines. Diarrheal disease and long-term sequelae caused by infections with the bacterial pathogens Shigella and enterotoxigenic E. coli (ETEC) pose a significant public health burden in low-income communities. There are currently no licensed vaccines against these pathogens, and the global health community has recently prioritized their development. The 2016 VASE Conference aimed to accelerate communication and progress among those working in the enteric vaccine field to make Shigella and ETEC vaccines a reality as quickly as possible. Research presented in oral and poster presentations at the VASE Conference covered a range of topics, including: the global burden of disease and public health case for Shigella and ETEC vaccines; current vaccine candidates in development; immunology and host responses to the pathogens; and the rationale for and status of combined Shigella-ETEC vaccine candidates. This article reviews key points and highlighted research presented in each of the plenary conference sessions and poster presentations at the 2016 conference. Planning for the 2018 VASE Conference is underway and will likely provide an important platform for sharing the latest updates on Shigella and ETEC vaccine research efforts and maintaining the momentum for accelerating this work. It is also expected that the VASE Conference will continue to provide a unique opportunity for those in the enteric vaccine field to share ideas, make connections, and create workable plans to make Shigella and ETEC vaccines a reality. (Updates available at: www.vaseconference.org.).

Individual-specific changes in the human gut microbiota after challenge with enterotoxigenic Escherichia coli and subsequent ciprofloxacin treatment

Background

Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in inhabitants from low-income countries and in visitors to these countries. The impact of the human intestinal microbiota on the initiation and progression of ETEC diarrhea is not yet well understood.

Results

We used 16S rRNA (ribosomal RNA) gene sequencing to study changes in the fecal microbiota of 12 volunteers during a human challenge study with ETEC (H10407) and subsequent treatment with ciprofloxacin.

Five subjects developed severe diarrhea and seven experienced few or no symptoms. Diarrheal symptoms were associated with high concentrations of fecal E. coli as measured by quantitative culture, quantitative PCR, and normalized number of 16S rRNA gene sequences. Large changes in other members of the microbiota varied greatly from individual to individual, whether or not diarrhea occurred. Nonetheless the variation within an individual was small compared to variation between individuals. Ciprofloxacin treatment reorganized microbiota populations; however, the original structure was largely restored at one and three month follow-up visits.

Conclusion

Symptomatic ETEC infections, but not asymptomatic infections, were associated with high fecal concentrations of E. coli. Both infection and ciprofloxacin treatment caused variable changes in other bacteria that generally reverted to baseline levels after three months.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2777-0) contains supplementary material, which is available to authorized users.

Status of vaccine research and development for norovirus

The global health community is beginning to gain an understanding of the global burden of norovirus-associated disease, which appears to have significant burden in both developed- and developing-country populations. Of particular importance is the growing recognition of norovirus as a leading cause of gastroenteritis and diarrhea in countries where rotavirus vaccine has been introduced. While not as severe as rotavirus disease, the sheer number of norovirus infections not limited to early childhood makes norovirus a formidable global health problem. This article provides a landscape review of norovirus vaccine development efforts. Multiple vaccine strategies, mostly relying on virus-like particle antigens, are under development and have demonstrated proof of efficacy in human challenge studies. Several are entering phase 2 clinical development. Norovirus vaccine development challenges include, but are not limited to: valency, induction of adequate immune responses in pediatric and elderly populations, and potential for vaccine-strain mismatch. Given current strategies and global health interest, the outlook for a norovirus vaccine is promising. Because a norovirus vaccine is expected to have a dual market in both developed and developing countries, there would likely be scale-up advantages for commercial development and global distribution. Combination with or expression by another enteric pathogen, such as rotavirus, could also enhance uptake of a norovirus vaccine.

Recommendations regarding the development of combined enterotoxigenic Eschericha coli and Shigella vaccines for infants

PATH hosted a workshop on October 14 and 15, 2013 in Washington, DC to solicit expert opinions on the potential merits and challenges of developing combined enterotoxigenic Escherichia coli (ETEC) and Shigella vaccine products to benefit children in developing countries. This article summarizes the key issues raised during the workshop and provides an analysis of the recommendations regarding the strategic, clinical and regulatory, and manufacturing considerations for the development of a combined enteric vaccine, which aim to guide future vaccine development efforts and donor investment strategies in this area. Notwithstanding the potential technical, legal, financial, and other constraints that would be faced in developing a combined ETEC/Shigella vaccine, it is clear that this is the preferred approach over standalone products. There are many advantages to a combined vaccine, such as the potential cost-effectiveness and easier logistics of introducing a combined vaccine instead of two standalone vaccines in low-resource, endemic countries.

An assessment of enterotoxigenic Escherichia coli and Shigella vaccine candidates for infants and children

Despite improvements to water quality, sanitation, and the implementation of current prevention and treatment interventions, diarrhea remains a major cause of illness and death, especially among children less than five years of age in the developing world. Rotavirus vaccines have already begun making a real impact on diarrhea, but several more enteric vaccines will be necessary to achieve broader reductions of illness and death. Among the many causes of diarrheal disease, enterotoxigenic Escherichia coli (ETEC) and Shigella are the two most important bacterial pathogens for which there are no currently licensed vaccines. Vaccines against these two pathogens could greatly reduce the impact of disease caused by these infections. This review describes the approaches to ETEC and Shigella vaccines that are currently under development, including a range of both cellular and subunit approaches for each pathogen. In addition, the review discusses strategies for maximizing the potential benefit of these vaccines, which includes the feasibility of co-administration, consolidation, and combination of vaccine candidates, as well as issues related to effective administration of enteric vaccines to infants. Recent impact studies indicate that ETEC and Shigella vaccines could significantly benefit global public health. Either vaccine, particularly if they could be combined together or with another enteric vaccine, would be an extremely valuable tool for saving lives and promoting the health of infants and children in the developing world, as well as potentially providing protection to travelers and military personnel visiting endemic areas.

New vaccines against enteric bacteria for children in less developed countries

Diarrheal diseases represent a major threat to infant survival in less developed countries. A real opportunity now exists to help alleviate this problem through the development of safe and effective multicomponent whole-bacterial cell vaccine(s) against enterotoxigenic Escherichia coli and Shigella, two important pathogens for which no licensed vaccine exists. What is preventing realization of this achievement is a lack of focus on the unique needs of children in less developed countries, along with committed and sufficient funding directed toward this goal. Live-attenuated and inactivated whole-cell vaccine candidates, some of which have languished too long, are available for testing, which, if performed in a coordinated fashion, can answer key unresolved issues concerning mucosal vaccination against enteric diseases. These candidate vaccines potentially provide a relatively simple intervention which could, if implemented, reduce the impact of these diseases upon the life and productivity of children.

Vaccine potential for inactivated shigellae

We used human monocyte-derived dendritic cells (DC) and Balb/c mice as models to establish the immunogenic and protective potential of formalin-inactivated Shigella spp. Incubation of DC with inactivated or live bacteria induced DC maturation and cytokine release. Mice immunized orally or intranasally with killed S. flexneri, S. sonnei, or S. dysenteriae developed IgG and fecal IgA titers to the homologous LPS. Following respiratory challenge with the live homologous organisms, 80-100% survival was seen in all vaccinated groups compared to negligible survival in mice given PBS. Oral or intranasal immunization with an inactivated S. flexneri 2a strain (CVD1203) expressing the CFA/I and CS3 antigens of enterotoxigenic Escherichia coli induced IgG responses to both heterologous antigens. These in vivo and in vitro data indicate that inactivated shigellae retain the ability to interact effectively with key antigen presenting cells and induce protective immune responses in mice.

Analysis of strategies to successfully vaccinate infants in developing countries against enterotoxigenic E. coli (ETEC) disease

Enterotoxigenic Escherichia coli (ETEC) is the most common bacterial cause of diarrhoea in the world, annually affecting up to 400,000,000 children under 5 years of age living in developing countries (DCs). Although ETEC possesses numerous antigens, the relatively conserved colonization factor (CF) antigens and the heat labile enterotoxin (LT) have been associated with protection and most vaccine candidates have exploited these antigens. A safe and effective vaccine against ETEC is a feasible goal as supported by the acquisition of protective immunity. The success of an ETEC vaccine targeting infants and children in DCs will depend on a combination of maximally antigenic vaccine preparations and regimens for their delivery which will produce optimal immune responses to these antigens. Vaccine candidates having a high priority for accelerated development and clinical testing for eventual use in infants would include inactivated ETEC or Shigella hybrids expressing ETEC antigens as well as attenuated ETEC strains which express the major CF antigens and LT toxin B-subunit, as well as attenuated Shigella, Vibrio cholerae and Salmonella typhi hybrids engineered to deliver antigens of ETEC. Candidates for an ETEC vaccine would have to meet the minimal requirement of providing at least 50% protection against severe disease in DCs during the first 2 years of life. The critical roadblock to achieving this goal has not been the science as much as the lack of a sufficiently funded and focused effort to bring it to realization. However, a Product Development Partnership to overcome this hurdle could accelerate the time lines towards when control of ETEC disease in DCs is substantially closer.

Safety and immunogenicity of an oral, inactivated, whole-cell vaccine for Shigella sonnei: preclinical studies and a Phase I trial

Orally delivered, inactivated whole-cell vaccines are safe methods of inducing local and systemic immunity. To increase surface proteins associated with adherence and invasion, Shigella sonnei were grown in BHI broth containing deoxycholate. A whole-cell vaccine (SsWC) was then produced by formalin inactivation. In pre-clinical studies, the SsWC vaccine was immunogenic and protected against S. sonnei-induced keratoconjunctivitis in the guinea pig model. In a randomized, double-blind, placebo-controlled, Phase I study, 10 evaluable subjects received either three doses of SsWC on Days 0, 14, and 28 (N = 3); five doses of SsWC on Days 0, 2, 4, 6, and 28 (N = 4); or placebo (N = 3). Each dose contained 2.0 x 10(10) inactivated cells. Serum and fecal antibodies against SsWC, LPS, and IpaC were measured by ELISA. A > or = 4-fold increase in titer was considered significant. Both SsWC dosing regimens were well tolerated. No fever or severe gastrointestinal symptoms were noted by any of the vaccinated subjects. Antibody responses were similar in the two dosing groups. Serum IgG or IgA responses to SsWC were seen in six of seven vaccinees (86%), to LPS in four of seven (57%), and to IpaC in five of seven (61%). Fecal IgA responses to these three antigens developed in five of five, three of five, and three of five subjects, respectively. Among the seven vaccinees, geometric mean rises in serum IgA levels to all three immunogens were significant; IgG increases trended toward significance (paired one-tailed t-test). We conclude that SsWC was immunogenic and protective in animal studies and well tolerated and immunogenic in a Phase I trial.

Enteric vaccines for pediatric use

Diarrheal diseases remain a major cause of death in children under 5 in less developed countries (LDCs). Vaccine development and implementation offers the best near-term approach to alleviating this problem. For this reason, a workshop to examine the possibilities for making enteric vaccines available to meet the specific needs of children in LDCs was convened in Virginia on April 24-26, 2004. Discussants considered research and development needs, regulatory and business issues, and previous experiences with enteric vaccine development and implementation. No insurmountable roadblocks to progress in this area were noted, and the possibility currently exists that properly supported efforts will enable the realization of enteric vaccines for pediatric use.

Prevention of disease in ferrets fed an inactivated whole cell Campylobacter jejuni vaccine

Ferrets were used to demonstrate the potential of a killed whole cell vaccine prepared from Campylobacter jejuni to protect against disease. C. jejuni strain 81-176 was grown in BHI broth, formalin-fixed, and resuspended in PBS to a concentration of 10(10) cells per ml. This vaccine (CWC) or live organisms were delivered orally with a nasogastric tube into anesthetized animals treated to reduce gastric acidity and intestinal motility. When 5x10(10) CFU of the vaccine strain (Lior serotype 5) or one of two other serotypes, CGL-7 (Lior 4) or BT44 (Lior 9), was used to challenge the ferrets, all of the animals developed a mucoid diarrhea. If the animals had been challenged with 5x10(9) CFU of the homologous strain 1 month before challenge with 10(10) CFU, 80-100% protection against disease was seen. This protection was also obtained after an initial exposure to the 81-176 strain followed by challenge with either of the heterologous strains. CWC was used to see if protection demonstrated with the live organisms could be produced with the non-living preparation. When 10(9) cells of CWC was given as two doses 7 days apart with or without 25mug of a coadministered mucosal adjuvant, LT(R192G), only 40-60% of the animals were protected. If the regimen was changed to four doses given 48h apart, 80% of the animals were free of diarrhea after subsequent challenge. Increasing the number of cells in the four dose regimen to 10(10) cells did not improve protection. Animals given four doses of 10(10) cells combined with LT(R192G) were subsequently challenged with 10(10) cells of the homologous strain or the heterologous strain CGL-7. The CWC protected against both strains. Serum IgG antibody titers determined by ELISA showed little increase following the CWC four dose vaccination regimen, compared to animals given one dose of the live organism. On subsequent challenge, however, both CWC vaccinated and live-challenged ferrets showed comparable antibody titer increases above those obtained following the initial challenge or vaccination. Western blots were used to show that the immunodominant antigen in vaccinated animals was a 45kDa protein, while in ferrets challenged with live organisms the immunodominant antigen was a 62kDa protein. These data show that the CWC can be used to protect against disease caused by Campylobacter. They also show that protection and serum IgG responses do not depend upon the use of the mucosal adjuvant and that cross protection among some of the major serotypes of Campylobacter responsible for human disease is possible.

Case report: pulmonary blastoma: presentation of two atypical cases and review of the literature

Pulmonary blastoma is a relatively rare aggressive adult malignancy. The clinical and radiographic features of two cases are described and the literature reviewed. Pulmonary blastoma usually presents radiologically as a well-defined mass lesion on chest radiography, which may be large enough to completely opacify the hemithorax and cause mediastinal shift. On CT, pulmonary blastoma is seen as a mixed solid and cystic lesion with variable contrast enhancement and a necrotic centre. Pleural effusion may be present but is not the predominant abnormality. Our cases are unusual as recurrent pleural effusions in the absence of a significant lung mass were the presenting findings.

Considerations for development of whole cell bacterial vaccines to prevent diarrheal diseases in children in developing countries

Enteric pathogens constitute a major pediatric threat in the developing world through their impact on morbidity and mortality, physical and cognitive development and cause and effect relationship with malnutrition. Although many bacterial pathogens can cause diarrheal diseases, a group of less than 10 including Shigella spp., enterotoxigenic Escherichia coli (ETEC), Vibrio cholerae, and possibly, Campylobacter jejuni account for a significant percentage of these diseases in developing countries. Rotavirus is also a major cause of diarrheal diseases. Vaccines against these agents offer a potentially effective control measure against these diseases, but safe, practical, and effective vaccines for many of these agents have yet to be realized. Many vaccine development approaches are under investigation, but the one that is currently most advanced and that has been most widely applied to enteric pathogens is the use of orally administered live or killed whole pathogen preparations. If inactivated, these vaccines will probably be administered as multiple doses with approximately 10(10) to 10(11) total particles per dose, but they are relatively safe for oral administration. Further, they may not require a buffer for delivery and can be stored in liquid formulations. Fewer doses may be required for some live attenuated pathogen vaccines, but a buffer will most likely be required for oral delivery and the product must be stored in a dried formulation. Also, safety becomes more of a concern with live pathogens depending on the degree of attenuation, host immunocompetence, and the total number and kinds of attenuated pathogens which may be present in a combined agent vaccine. Both live and killed whole pathogen vaccines can be immunogenic and have the possibility to serve as vectors for other antigens. Although many organisms and serotypes are clinically important, by exploiting antigenic cross reactivity and using some pathogen components as vectors for cloned antigens of other pathogens, it could be possible to induce immunity against major enteric pathogens/serotypes with <10 whole pathogen components in a multi-agent vaccine. Safe and effective mucosal adjuvants may in the future be useful in whole pathogen vaccines, but they do not seem to be essential for immunization. Further, dietary supplements such as zinc, mixed routes of delivery and new regimens are under study which may in the future enhance further the effectiveness of the whole pathogen vaccines which now seem realizable in the near term. For this to happen, however, a coordinated and committed effort is necessary now to address the immunologic, regulatory, manufacturing, testing and implementation issues which will be involved in the realization of this important product to benefit children's health worldwide.

Campylobacter vaccine development:a key to controlling enteric diseases

Worldwide, Campylobacter jejuni is a major cause of diarrhoea and dysentery, with approximately 400 million cases occurring annually. Control of the disease through public health and antibiotic measures is insufficient, and vaccination offers the most promising solution. Infection produces immunity from disease, suggesting that vaccination may produce similar protection. Epidemiological data suggest that there are conserved antigens among serotypes; immunity against which protects against disease. Therefore a monovalent serotype vaccine seems practical. Several antigens on Campylobacter have been found to be immunogenic and, in some cases, associated with virulence. However, none of these proteins have been produced recombinantly in the proper conformation, nor have they been protective in preclinical models. For this reason, live attenuated or inactivated Campylobacter whole cell (CWC) vaccines may be the best approach. Development of an attenuated strain of Campylobacter has been complicated by the fact that the organism is highly transformable. Rec A mutants of Campylobacter have recently been constructed in an attempt to avoid this trait. Such mutants have been made defective in various virulence properties and are being evaluated for safety in preclinical models. Antex Biologics has made an inactivated CWC vaccine using the Company's patented NST (nutriment signal transduction) technology, whereby the cells are grown using physiologically logical conditions to maximise the expression of antigens associated with in vivo virulence. This vaccine has been shown to be safe, immunogenic, and protective in preclinical models of infection. Inclusion of a mucosal adjuvant in the vaccine increases the immunological response to the antigen. Recent Phase I and Phase II clinical trials, using the CWC vaccine formulated with an adjuvant and orally administered, show that the vaccine is safe and immunogenic in human volunteers. The approach used to develop this inactivated whole cell Campylobacter vaccine is also applicable for the rapid development of new vaccines against a variety of mucosal pathogens.

In vivo phase variation and serologic response to lipooligosaccharide of Campylobacter jejuni in experimental human infection

Some Campylobacter jejuni strains which exhibit mimicry of gangliosides in their lipooligosaccharides (LOSs) are associated with development of Guillain-Barré syndrome, which complicates the selection of a suitable C. jejuni strain in a live-attenuated vaccine. C. jejuni 81-176 is the most well characterized strain available, but structurally, LOS of C. jejuni 81-176 exhibits mimicry of predominantly GM2 and GM3 gangliosides. We compared the antiganglioside human serologic responses of 22 volunteers post-oral vaccination (two-dose series, 14 days apart) with a killed whole-cell C. jejuni vaccine, those of volunteers (22 following initial challenge and 5 upon rechallenge) experimentally infected with the homologous C. jejuni vaccine strain 81-176, and those of 12 volunteers used as controls (placebo recipients). All volunteers were evaluated using thin-layer chromatography immuno-overlay and a panel of nine gangliosides at days 0, 21, and 28 either postvaccination or postinoculation. Antiganglioside antibodies were identified at baseline in 6 of the 61 volunteers (9.8%). There were no antiganglioside antibodies observed following vaccination or experimental infection rechallenge. Evidence of seroconversion was observed in 2 of 22 (9.1%) in the initial infection challenge group, comparable to 1 of 12 (8.3%) in the placebo recipients. Additional testing of seven selected volunteers in the initial challenge group at days 0, 3, 7, 10, 21, 28, and 60 showed that when antiganglioside antibodies occurred (mostly anti-GM1 and -GM2), responses were weak and transient. Furthermore, evidence from serologic probing of LOSs of isolates recovered from stools of six volunteers indicated that the isolates had undergone antigenic phase variation in ganglioside mimicry during passage in vivo. Collectively, with the exception of one volunteer with anti-GM2 antibodies at day 60, the results show an absence of persistent antiganglioside antibodies after experimental infection with C. jejuni or following administration of a killed C. jejuni whole-cell oral vaccine, although LOS phase variation occurred.

B cell responses in gastric antrum and duodenum following oral inactivated Helicobacter pylori whole cell (HWC) vaccine and LT(R192G) in H pylori seronegative individuals

To investigate whether B cell-specific responses could be elicited in the gastric mucosa of Helicobacter pylori (HP) naive subjects, five volunteers ingested three doses of a HP killed whole cell (HWC) vaccine with 25 microg of recombinant heat-labile toxin (LT(R192G)). Two of three subjects had detectable LT(R192G) and HWC IgA antibody secreting cell (ASC) gastric responses. LT(R192G) and HWC responses in duodenal were 5-14-fold higher than those detected in antral biopsies (P<0.01 and P=0.05, respectively). These results provide the first evidence that specific gastric B cell responses can be induced in HP-non-infected individuals following oral immunization.

Safety and immunogenicity of oral inactivated whole-cell Helicobacter pylori vaccine with adjuvant among volunteers with or without subclinical infection

Helicobacter pylori infection of the gastric mucosa can be found in approximately 50% of the world's population and is associated with a range of pathology, including peptic ulcer, atrophic gastritis, and gastric cancer. To explore immunization as a strategy for preventing and treating H. pylori-associated disease, we assessed the safety and immunogenicity in healthy adults of a formalin-inactivated, oral H. pylori whole-cell (HWC) vaccine, administered with or without mutant Escherichia coli heat-labile toxin (LT(R192G)) as a mucosal adjuvant. In a dose-response study, 23 subjects with or without H. pylori infection were vaccinated with either 2.5 x 10(6) HWC, 2.5 x 10(8) HWC, or 2.5 x 10(10) HWC, plus 25 microg of LT(R192G). Thereafter, a randomized study was conducted in which 18 H. pylori-infected subjects were assigned, in a double-blind fashion, to receive either 2.5 x 10(10) HWC plus placebo-adjuvant, placebo-vaccine plus 25 microg of LT(R192G), placebo-vaccine plus placebo-adjuvant, or 2.5 x 10(10) HWC plus 25 microg of LT(R192G). Diarrhea (six subjects), low-grade fever (five subjects), and vomiting (two subjects) were observed, usually after the first dose. Significant rises in geometric mean mucosal (fecal and salivary) anti-HWC immunoglobulin A antibodies occurred among H. pylori-infected and uninfected subjects following inoculation with 2.5 x 10(10) HWC plus 25 microg of LT(R192G). Moreover, among H. pylori-negative volunteers, this regimen induced significant lymphoproliferative responses in 5 of 10 subjects and gamma interferon production responses to H. pylori sonicate in 7 of 10 subjects. There was no evidence that vaccination eradicated H. pylori in infected volunteers. These results suggest that it is possible to stimulate mucosal and systemic immune responses in humans to H. pylori antigens by using an HWC vaccine.

Inactivated whole-cell bacterial vaccines: current status and novel strategies

Inactivated bacterial whole-cell vaccines have been the most widely studied prophylactic treatment for infectious diseases. They offer an economical, and potentially safe, effective means of preventing disease. The disadvantages of these vaccines have been that parenteral administration, while effective in some instances, may have caused adverse reactions in vaccinees, while oral administration often required high doses and resulted in short-term immunity. More recent studies describing new approaches for improving antigenicity of inactivated whole-cell vaccines and the enhancement of immune responses to oral immunization offer great hope for improving the efficacy of these agents. Promising whole cell vaccines include those against Vibrio cholerae, enterotoxigenic Escherichia coli, and more recently Campylobacter jejuni.

Automated fluorescent analysis procedure for enzymatic mutation detection

The Enzymatic Mutation Detection (EMD) assay detects mutations or polymorphisms in DNA. The assay procedure takes <1 h and is followed by electrophoretic detection. We report an automated procedure, using fluorescently labeled probe and quantitative analysis on the ABI Prism 377 DNA Sequencer, that improves on earlier methods (1, 2) by eliminating the need for sample purification, shortening the hybridization time, and increasing the signal-to-noise ratio. The EMD assay uses the bacteriophage resolvase T4 endonuclease VII, which cleaves the heteroduplex molecules at the mismatch site, forming two shorter fragments that are resolved by gel electrophoresis. Unlike existing mutation techniques, the EMD method uses a single protocol to identify point mutations, deletions, and insertions for all DNA fragments. Test DNA samples are assayed directly from PCR reactions, and fragments up to 4 kb in size have been assayed successfully. A independent analysis on the p53 tumor suppressor gene from clinical samples has shown 100% sensitivity and 94% specificity. Because the fluorescent EMD assay has been optimized for high signal-to-noise ratios, mutations can be identified in mixed samples containing up to a 20-fold excess of normal DNA.

Problems and priorities for controlling opportunistic pathogens with new antimicrobial strategies; an overview of current literature

An International Study Group on New Antimicrobial Strategies (ISGNAS) has been formed in response to the recognition that development of microbial resistance to antibiotics is becoming a serious, world-wide problem. The group met in 1993 for the first time to discuss the feasibility of developing rational alternatives to the use of antibiotics and prepared, as a result, a comprehensive overview of normal (physiological) mechanisms involved in the control of potentially pathogenic (oppotunistic) microorganisms. One objective of ISGNAS is to understand the conditions which allow opportunistic microbes present among the symbionts to cause an infection. There is a need for more coherent information concerning the habitat, growth requirements and host and pathogen properties which allow opportunistic pathogens to cause life-threatening infections. In particular, information is urgently being sought to understand the complexity of the interactions between the vast number of microbial species, and the interactions between the microbes and their host. Another goal is to inspire and enable basic and clinical research that will lead to the development of new therapies for regulating colonization, translocation and infection by opportunistic micro-organisms in patients during periods of decreased resistance. With a sufficient amount of knowledge of how healthy individuals keep opportunistic micro-organisms under control, it may become feasible for physicians to maintain host resistance and inter-microbial factors involved in the containment of opportunistic microbes. Therapies aimed at boostering natural resistance mechanisms will be of critical importance to individuals whose resistance has been compromised as a result of another clinical condition.

Safety and immunogenicity of a prototype oral whole-cell killed Campylobacter vaccine administered with a mucosal adjuvant in non-human primates

The safety and immunogenicity of two prototype oral Campylobacter killed whole-cell (CWC) vaccines were tested in rhesus monkeys. Animals were immunized with a primary two-dose series (days 0 and 14) of vaccine consisting of CWC (10(10) particles/dose) given alone or in combination with 0.5-1000 micrograms of the heat-labile enterotoxin of Escherichia coli as an oral adjuvant (OA). A booster vaccination, 4 weeks after primary immunization, was given to animals receiving CWC alone or supplemented with 0.5, 5 or 50 micrograms of OA. Both CWC and CWC-OA were well tolerated, with no adverse side-effects noted. Campylobacter-specific as well as adjuvant-specific antibody-secreting cells (ASCs) were determined in peripheral blood collected 7 days after each vaccine dose. Campylobacter-specific IgA ASC responses were enhanced by OA in a dose-dependent manner (p = 0.025), while IgG ASC responses were not. Seroconversions (both IgA and IgG) to Campylobacter antigens were also enhanced in monkeys receiving adjuvanted vaccine. No significant booster vaccination effect was observed in circulating ASCs in any of the immunization groups. In vitro T-cell proliferative responses to Campylobacter jejuni antigens were somewhat enhanced in both the CWC and CWC-OA immunization groups. These results demonstrate that CWC-OA is safe and superior to CWC alone in its ability to stimulate both local and systemic Campylobacter-specific IgA and IgG responses in primates and they support its further evaluation in human clinical studies.

New strategies for using mucosal vaccination to achieve more effective immunization

Future progress in vaccination will be significantly advanced by application of emerging technologies for immunization of mucosal surfaces. It should now be possible to maximize the antigenicity of many vaccines and facilitate their interaction with appropriate lymphoid tissues to induce protective cellular and humoral responses. Mucosal vaccines requiring no more than two doses are achievable with current technologies. Living vaccines have been among the most promising candidates for mucosal vaccination, but with few exceptions their promise is still to be realized. Development of new microencapsulated delivery systems and adjuvants has made non-living vaccines reasonable options for mucosal immunization. To be practical, such vaccines should be developed as combined agent vaccines, possibly deliverable by multiple mucosal routes. Although strategies to be used for specific mucosal vaccines will depend upon a number of factors pertinent to the disease agent, in concept an adjuvant administered with inactivated but maximally antigenic pathogens or their recombinant adhesive subcomponents could prove to be among the more practical mucosal vaccine options for use globally.

Killed Campylobacter elicits immune response and protection when administered with an oral adjuvant

The heat-labile toxin (HLT) of enterotoxigenic Escherichia coli (ETEC) is a potent oral adjuvant. We determined whether the ETEC HLT could be mixed with killed campylobacter to induce an immune response protective upon subsequent challenge with live pathogens. Mice were immunized orally three times with 10(9) sonicated campylobacter with or without 25 micrograms of ETEC HLT, and humoral immune responses in intestinal lavage fluids measured by ELISA. Whereas 10(9) live bacteria induced strong intestinal IgA responses, killed bacteria did not unless ETEC HLT was also added. The magnitude of the antibody response was dependent on the amount of antigen given. The ETEC HLT given with bacteria also induced a potent cross-reaction with cholera toxin. The latter had an adjuvant effect in mice similar to that of ETEC HLT. Protection against colonization was studied in mice and rabbits. In contrast to non-immune animals, those given live organisms or sonicated cells mixed with ETEC HLT quickly cleared homologous, but not heterologous, Lior serotypes of Campylobacter upon challenge. These data show for the first time that ETEC HLT can potentiate an immune response to killed campylobacter that promotes a rapid clearance of live pathogens from the intestine.

Therapies for radiation injuries: research perspectives

Exposure to radiation damages the immune, hematopoietic, and gastrointestinal components of the host defense system. This may lead to serious endogenous or exogenous infections. When radiation injury is combined with other physical trauma, e.g., burn or wound, the resulting damage to these systems is synergistic, and treatment for infection requires multiple approaches. This paper reviews successful single and combined therapeutic modalities for infections in irradiated mice and irradiated mice inflicted with trauma that are currently conducted at the Armed Forces Radiobiology Research Institute. The models of endogenous and exogenous infection and combined injury are described. The management of wounds infected with bacteria, exogenous systemic infection due to gram-negative enteric bacteria, and the chemoprophylaxis of enteric-derived systemic infection with quinolones is described. Infections can be treated successfully with proper antimicrobial therapy. In gamma- and neutron-irradiated mice, the immunomodulator trehalose dimycolate (TDM) was effective in treating endogenous infection. TDM with the antimicrobial ceftriaxone was effective in treating exogenous infection due to Klebsiella pneumoniae. Improvement in managing infection in irradiated and injured hosts will require further research using these diagnostic and therapeutic modalities. Accurate biological dosimetry is critical in determining if victims are at risk of developing infection. We found that radiation induced changes in plasma diamine oxidase activity; monitoring these changes was a useful indicator of the severity of radiation injury.

Significance of flagella in colonization resistance of rabbits immunized with Campylobacter spp

Cross-protection among different Lior and Penner serogroups of Campylobacter spp. was studied. Rabbits were orally immunized by gastric feeding with Campylobacter spp., and 27 to 30 days later, they were challenged with matched or unmatched serogroups by the removable intestinal tie adult rabbit diarrhea (RITARD) procedure. When immunized animals were challenged with different Lior serotypes, no protection against colonization was seen; however, when challenged with homologous Lior serogroups, protection was demonstrated. Immune animals were colonized for an average of 1 day or less versus at least 6 days for nonimmune animals. Rabbits challenged with matched Penner-unmatched Lior strains showed only marginal protection. Our study also demonstrated that flagella are important in initiating colonization and eliciting protective immunity. Campylobacter coli VC167B3, an isogenic, nonflagellated mutant, did not colonize rabbits regardless of the route of administration. Single feeding of the mutant strain did not protect the host, whereas three feedings, 48 h apart, resulted in complete protection against the flagellated parent strain. When mutant strain immunized rabbits were challenged with other strains of the same Lior serotype, marginal protection was obtained. Immunogold labeling indicated that there is one or more antigens on the cell surface of the nonflagellated mutant which reacts with a polyclonal antiserum from organisms of the same Lior serogroup. These data implicated the flagellum as the cross-strain protective component of the Lior antigen complex.

The effect of footrot on body weight and wool growth of sheep

Body weight and traits associated with production of wool were measured over a 2-year period between 1985 and 1987 in south-western New South Wales in a flock of Merino wethers experimentally infected with footrot. The disease was allowed to spread freely amongst 150 of the flock but kept at very low prevalence in the remaining 50 by preventive footbathing during transmission periods. Severe, underrunning footrot had a significant adverse effect on body weight, for each year of the trial. Body weight was most severely reduced at times of the year when footrot was spreading among animals and lesions were severe. The mean body weight of the infected group at the end of the 2 years of observation was 7.3 kg (11.6%) below that of the control group. Footrot also depressed wool growth, with the mean clean fleece weight of the infected group being 0.4 kg (8%) lighter than that of the controls at each of the 2 annual shearings. There were no consistent differences between the groups for the other wool characteristics measured.

Serum antibody responses in sheep after natural infection with Bacteroides nodosus

Soluble outer membrane protein of Bacteroides nodosus extracted with potassium thiocyanate (KSCN) was employed as antigen in an enzyme linked immunosorbent assay (ELISA) to detect serum antibody in sheep naturally infected with a heterologous serogroup. Serum antibody responses in 55 sheep were monitored for 2 years and maximum levels were directly related to the severity of clinical foot lesions. Serum antibody levels rose 2 weeks after foot lesions developed and declined within several months of resolution of lesions. After the first footrot transmission period, antibody levels persisted significantly (P less than 0.001) longer in sheep that did not become affected in the next transmission period compared with sheep in which footrot recurred. Antibody response did not appear to result in resolution of foot lesions. ELISA using KSCN antigen gave similar results to whole cell ELISA where cells prepared from an homologous serogroup were used as antigen. Both these assays were more sensitive than ELISA in which heterologous whole cell antigen was used. Proteins extracted from the outer membrane of B. nodosus, which are known to be immunogenic in natural infection and common to different serogroups of B. nodosus, appear to be useful antigens for serological investigations of ovine footrot.

Intestinal barriers to bacteria and their toxins

Immunologic and nonimmunologic processes work together to protect the host from the multitude of microorganisms residing within the intestinal lumen. Mechanical integrity of the intestinal epithelium, mucus in combination with secretory antibody, antimicrobial metabolites of indigenous microorganisms, and peristalsis each limit proliferation and systemic dissemination of enteric pathogens. Uptake of microorganisms by Peyer's patches and other intestinal lymphoid structures and translocation circumvent the mucosal barrier, especially in immunosuppressed individuals. Improved understanding of the composition and limitation of the intestinal barrier, coupled with advances in genetic engineering of immunogenic bacteria, development of oral delivery systems, and immunomodulators, now make enhancement of mucosal barriers feasible.

Trehalose dimycolate enhances resistance to infection in neutropenic animals

Bacterial infections are lethal complications of neutropenia, and antibiotics alone are inadequate therapy for these infections. Irradiated mice become severely neutropenic and remain susceptible to infection for 2 to 3 weeks, depending on the dose and quality of radiation. Some bacterial cell wall derivatives stimulate nonspecific host defense mechanisms against a variety of microbes which might cause postirradiation infection. In this study we determined if the cell wall glycolipid trehalose dimycolate (TDM), derived from Mycobacterium phlei, or a synthetic preparation of TDM was able to (i) enhance survival in mice when given before or after lethal doses of 60Co radiation and (ii) increase nonspecific resistance to postirradiation infection. Treatment with TDM oil-in-water emulsions and with synthetic TDM significantly enhanced survival before and after lethal doses of 60Co irradiation. This result correlated with the ability of TDM to reduce the translocation of intestinal bacteria and to stimulate hematopoiesis. With respect to nonspecific resistance to infection, TDM injected 1 h after sublethal irradiation increased resistance to a lethal Klebsiella pneumoniae challenge (10 50% lethal doses of K. pneumoniae in 30 days [LD50/30]) 4 or 14 days later. Increasing the dose of K. pneumoniae to 5,000 LD50/30 on day 4 overwhelmed the ability of TDM-treated mice to overcome infection. However, TDM treatment 1 h postirradiation combined with ceftriaxone antibiotic therapy (days 5 through 14) enhanced survival, even when the higher dose of bacteria (5,000 LD50/30) was used. These results indicate that in irradiated mice, TDM can be used to enhance survival and, as a potent stimulant of nonspecific resistance to infection in neutropenic mice, can act synergistically with antibiotic therapy to reduce sepsis and mortality.

Role of endotoxemia in cardiovascular dysfunction and mortality. Escherichia coli and Staphylococcus aureus challenges in a canine model of human septic shock

Using different types of bacteria and a canine model simulating human septic shock, we investigated the role of endotoxin in cardiovascular dysfunction and mortality. Either Escherichia coli (a microorganism with endotoxin) or Staphylococcus aureus (a microorganism without endotoxin) were placed in an intraperitoneal clot in doses of viable or formalin-killed bacteria. Cardiovascular function of conscious animals was studied using simultaneous radionuclide heart scans and thermodilution cardiac outputs. Serial plasma endotoxin levels were measured. S. aureus produced a pattern of reversible cardiovascular dysfunction over 7-10 d that was concordant (P less than 0.01) with that of E. coli. Although this cardiovascular pattern was not altered by formalin killing (S. aureus and E. coli), formalin-killed organisms produced a lower mortality and less myocardial depression (P less than 0.01). S. aureus, compared to E. coli, produced higher postmortem concentrations of microorganisms and higher mortality (P less than 0.025). E. coli produced significant endotoxemia (P less than 0.01), though viable organisms (versus nonviable) resulted in higher endotoxin blood concentrations (P less than 0.05). Significant endotoxemia did not occur with S. aureus. Thus, in the absence of endotoxemia, S. aureus induced the same cardiovascular abnormalities of septic shock as E. coli. These findings indicate that structurally and functionally distinct microorganisms, with or without endotoxin, can activate a common pathway resulting in similar cardiovascular injury and mortality.

Selective association and transport of Campylobacter jejuni through M cells of rabbit Peyer's patches

M cells in the Peyer's patches may facilitate transport of pathogens such as Campylobacter jejuni from the intestine. We evaluated this hypothesis by using electron microscopy to examine Peyer's patches in ligated adult rabbit ileal loops inoculated with 5-mL suspensions of 10(9) cfu/mL of Campylobacter jejuni. Peyer's patches taken at intervals from 15 min to 2 h after inoculation of loops in anaesthetized rabbits provided evidence that Campylobacter jejuni selectively adhered to M cells as opposed to absorptive epithelial cells and was transported, apparently intact, into the M cell follicle. Although intercellular organisms were seen within the follicle, many others were phagocytosed by lymphoid cells. The proximity of the lymphatic and blood circulatory systems to the M cell follicle makes this a probable route for systemic spread of Campylobacter jejuni.

Prospects for management of gastrointestinal injury associated with the acute radiation syndrome

The effect of total-body ionizing radiation on the digestive tract is dose-dependent and time-dependent. At low doses (1.5 Gy), one observes only a short prodromal syndrome consisting of nausea, vomiting, and gastric suppression. At doses greater than 6 Gy, the prodromal syndrome is more marked, and it is followed after a 2-5-day remission period by a subacute syndrome, characterized by diarrhea and hematochezia. This gastrointestinal syndrome is superimposed onto a radiation-induced bone marrow suppression. The combination of intestinal and hemopoietic syndromes results in dehydration, anemia, and infection, leading eventually to irreversible shock and death. The treatment of prodromal symptoms is based on the administration of antiemetics and gastrokinetics, although an effective treatment devoid of side effects is not yet available for human therapy. The treatment of the gastrointestinal subacute syndrome remains difficult and unsuccessful after exposure to total body doses greater than 8-10 Gy. Supportive therapy to prevent infection and dehydration may be effective if restoration or repopulation of the intestinal and bone marrow stem cells does occur. In addition, bone marrow transplantation may improve the prospect of treating the hemopoietic syndrome, although the experience gained in Chernobyl suggests that this treatment is difficult to apply in the case of nuclear accidents. Administration of radioprotectants before irradiation decreases damage to healthy cells, while not protecting cancerous tissues. In the future, stimulation of gastrointestinal and hemopoietic progenitor cells may be possible using cell growth regulators, but much remains to be done to improve the treatment of radiation damage to the gastrointestinal tract.

Effect of antimicrobial therapy on bowel flora and bacterial infection in irradiated mice

Mice exposed to 10 Gy cobalt-60 radiation were given intramuscular antimicrobial therapy of gentamicin, or metronidazole, or a combination of the two. Mortality in the mice treated with metronidazole alone or in combination with gentamicin occurred earlier than in the controls (P less than 0.001). Microorganisms were recovered from the blood, spleen, and liver of the metronidazole-treated mice earlier than from other groups. The predominant organisms recovered from these animals were Enterobacteriaceae. Quantitative cultures of the ileal flora showed a decrease in the number of aerobic, facultative anaerobic and strict anaerobic bacteria after irradiation, and a subsequent increase only in the number of strict aerobic bacteria. As compared to untreated mice, a rapid decrease (by 8.8 logs) in the number of anaerobic flora occurred in the mice treated with metronidazole 5 days after irradiation. This was followed by a rapid increase in the number of aerobic organisms which coincided with the earlier mortality in this group. These data suggest that antimicrobial agents that decrease the number of the strict anaerobic component of the gut flora enhance systemic infection by aerobic or facultative anaerobic bacteria, and this facilitates mortality after irradiation.

Cardiovascular performance with E. coli challenges in a canine model of human sepsis

We investigated cardiovascular dysfunction by injecting lethal and nonlethal bacterial challenges into conscious dogs. E. coli bacteria of varying numbers were placed in a peritoneal clot. Cardiovascular function was studied with simultaneous radionuclide scans and thermodilution cardiac outputs. In surviving animals, the number of bacteria in the clot increased as the corresponding systolic cardiac function decreased (P = 0.01). Cardiac function was measured by left ventricular (LV) ejection fraction (EF) and LV function curves [LV stroke work index (LVSWI) vs. end-diastolic volume index (EDVI), and peak systolic pressure vs. end-systolic volume index]. Furthermore, the diastolic volume-pressure relationship of survivors shifted progressively to the right [i.e., increasing EDVI (P less than 0.02) with minimal change (P = NS) in LV filling pressure]. This increase in LV size was associated with maintenance of measures of cardiac performance [stroke volume index (SVI) and stroke work index (SWI)] at similar levels. Death occurred only in the group with the highest bacterial dose. Compared with survivors receiving the same number of bacteria, nonsurvivors had a decrease in (P less than 0.05) LV size, a leftward shift (P less than 0.01) in LV diastolic volume-pressure relationship, and a decrease in both LVSWI and SVI (possibly related to volume and/or LV functional status). Data from survivors suggest that increasing the number of bacteria produces changes in myocardial compliance and contractility. These changes increase LV size (preload), a major determinant of cardiac performance that possibly enhances survival.

Requirements of radioprotectors for military and emergency needs

Uncontrolled exposure to radiation from nuclear weapons, space, or accidents presents challenges unlike those met in radiotherapy. For example, the time and quality of exposure are uncertain. Thus it is necessary to develop radioprotectors that can be given chronically (e.g. as vitamin combinations), or shortly before exposure (e.g. as WR-2721 and related compounds), or after exposure (e.g. as immunomodulators) to cover all possible situations of use. Also, for military purposes, performance capability, as well as survival from acute effects, must be maintained. In contrast to clinical and experimental exposure, it is likely that stem cells will survive in military and accident situations, making supportive therapy (e.g. fluids, antibiotics) of real value. Radioprotectors that can increase cell survival or enhance repopulation by the remaining cells can reduce the time required for supportive therapy and enhance its effectiveness. First-generation agents to accomplish this may be combinations of agents to mitigate free radical damage such as dietary supplements or WR-2721 and related compounds. Immunomodulators, either microbial agents (e.g. glucan, TDM) or recombinant cytokines (e.g. interleukin-1, colony-stimulating factor), can enhance hematopoietic and functional cell recovery after irradiation. Synergistic effects can be demonstrated with some combinations of these agents. This is important because agents with individual DRFs of less than two can be significant radioprotectors in combinations. Whether these combinations are effective against combined injury remains to be determined. Future research into mechanisms of radiation-induced damage and natural repair mechanisms should lead to even better second-generation radioprotectants.(ABSTRACT TRUNCATED AT 250 WORDS)