Characterization of Turbo, a TLR Ligand-based Adjuvant for Glycoconjugate Vaccines.

Many bacterial polysaccharide vaccines, including the typhoid Vi polysaccharide (ViPS) and tetravalent meningococcal polysaccharide conjugate (MCV4) vaccines, do not incorporate adjuvants and are not highly immunogenic, particularly in infants. I found that endotoxin, a TLR4 ligand in ViPS, contributes to the immunogenicity of typhoid vaccines. Because endotoxin is pyrogenic, and its levels are highly variable in vaccines, I developed monophosphoryl lipid A, a nontoxic TLR4 ligand-based adjuvant named Turbo. Admixing Turbo with ViPS and MCV4 vaccines improved their immunogenicity across all ages and eliminated booster requirement. To understand the characteristics of this adjuvanticity, I compared Turbo with alum. Unlike alum, which polarizes the response toward the IgG1 isotype, Turbo promoted Ab class switching to all IgG isotypes with affinity maturation; the magnitude of this IgG response is durable and accompanied by the presence of long-lived plasma cells in the mouse bone marrow. In striking contrast with the pathways employed by alum, Turbo adjuvanticity is independent of NLPR3, pyroptotic cell death effector Gasdermin D, and canonical and noncanonical inflammasome activation mediated by Caspase-1 and Caspase-11, respectively. Turbo adjuvanticity is primarily dependent on the MyD88 axis and is lost in mice deficient in costimulatory molecules CD86 and CD40, indicating that Turbo adjuvanticity includes activation of these pathways. Because Turbo formulations containing either monophosphoryl lipid A or TLR2 ligands, Pam2CysSerLys4, and Pam3CysSerLys4 help generate Ab response of all IgG isotypes, as an adjuvant Turbo can improve the immunogenicity of glycoconjugate vaccines against a wide range of bacterial pathogens whose elimination requires appropriate IgG isotypes.

Improving Our Understanding of Salmonella enterica Serovar Paratyphi B through the Engineering and Testing of a Live Attenuated Vaccine Strain.

Enteric fever is caused by three Salmonella enterica serovars: Typhi, Paratyphi A, and Paratyphi B sensu stricto Although vaccines against two of these serovars are licensed (Typhi) or in clinical development (Paratyphi A), as yet there are no candidates for S. Paratyphi B. To gain genomic insight into these serovars, we sequenced 38 enteric fever-associated strains from Chile and compared these with reference genomes. Each of the serovars was separated genomically based on the core genome. Genomic comparisons identified loci that were aberrant between serovars Paratyphi B sensu stricto and Paratyphi B Java, which is typically associated with gastroenteritis; however, the majority of these were annotated as hypothetical or phage related and thus were not ideal vaccine candidates. With the genomic information in hand, we engineered a live attenuated S. Paratyphi B sensu stricto vaccine strain, CVD 2005, which was capable of protecting mice from both homologous challenge and heterologous challenge with S. Paratyphi B Java. These findings extend our understanding of S. Paratyphi B and provide a viable vaccine option for inclusion in a trivalent live attenuated enteric fever vaccine formulation.IMPORTANCE We developed a live attenuated Salmonella enterica serovar Paratyphi B vaccine that conferred protection in mice against challenge with S Paratyphi B sensu stricto and S Paratyphi B Java, which are the causes of enteric fever and gastroenteritis, respectively. Currently, the incidence of invasive S. Paratyphi B sensu stricto infections is low; however, the development of new conjugate vaccines against other enteric fever serovars could lead to the emergence of S. Paratyphi B to fill the niche left by these other pathogens. As such, an effective S. Paratyphi B vaccine would be a useful tool in the armamentarium against Salmonella infections. Comparative genomics confirmed the serovar-specific groupings of these isolates and revealed that there are a limited number of genetic differences between the sensu stricto and Java strains, which are mostly hypothetical and phage-encoded proteins. The observed level of genomic similarity likely explains why we observe some cross-protection.

Implementation of Interventions for the Control of Typhoid Fever in Low- and Middle-Income Countries.

Past research has focused on typhoid fever surveillance with little attention to implementation methods or effectiveness of control interventions. This study purposefully sampled key informants working in public health in Chile, India, Pakistan, Bangladesh, Thailand, Vietnam, South Africa, and Nigeria to 1) scope typhoid-relevant interventions implemented between 1990 and 2015 and 2) explore contextual factors perceived to be associated with their implementation, based on the Consolidated Framework for Implementation Research (CFIR). We used a mixed methods design and collected quantitative data (CFIR questionnaire) and qualitative data (interviews with 34 public health experts). Interview data were analyzed using a deductive qualitative content analysis and summary descriptive statistics are provided for the CFIR data. Despite relatively few typhoid-specific interventions reportedly implemented in these countries, interventions for diarrheal disease control and regulations for food safety and food handlers were common. Most countries implemented agricultural and sewage treatment practices, yet few addressed the control of antibiotic medication. Several contextual factors were perceived to have influenced the implementation of typhoid interventions, either as enablers (e.g., economic development) or barriers (e.g., limited resources and habitual behaviors). Consolidated Framework for Implementation Research factors rated as important in the implementation of typhoid interventions were remarkably consistent across countries. The findings provide a snapshot of typhoid-relevant interventions implemented over 25 years and highlight factors associated with implementation success from the perspective of a sample of key informants. These findings can inform systematic investigations of the implementation of typhoid control interventions and contribute to a better understanding of the direct effects of implementation efforts.

Typhoid fever vaccination strategies.

Typhoid vaccination is an important component of typhoid fever prevention and control, and is recommended for public health programmatic use in both endemic and outbreak settings. We reviewed experiences with various vaccination strategies using the currently available typhoid vaccines (injectable Vi polysaccharide vaccine [ViPS], oral Ty21a vaccine, and injectable typhoid conjugate vaccine [TCV]). We assessed the rationale, acceptability, effectiveness, impact and implementation lessons of these strategies to inform effective typhoid vaccination strategies for the future. Vaccination strategies were categorized by vaccine disease control strategy (preemptive use for endemic disease or to prevent an outbreak, and reactive use for outbreak control) and vaccine delivery strategy (community-based routine, community-based campaign and school-based). Almost all public health typhoid vaccination programs used ViPS vaccine and have been in countries of Asia, with one example in the Pacific and one experience using the Ty21a vaccine in South America. All vaccination strategies were found to be acceptable, feasible and effective in the settings evaluated; evidence of impact, where available, was strongest in endemic settings and in the short- to medium-term. Vaccination was cost-effective in high-incidence but not low-incidence settings. Experience in disaster and outbreak settings remains limited. TCVs have recently become available and none are WHO-prequalified yet; no program experience with TCVs was found in published literature. Despite the demonstrated success of several typhoid vaccination strategies, typhoid vaccines remain underused. Implementation lessons should be applied to design optimal vaccination strategies using TCVs which have several anticipated advantages, such as potential for use in infant immunization programs and longer duration of protection, over the ViPS and Ty21a vaccines for typhoid prevention and control.

Challenges in measuring complications and death due to invasive Salmonella infections.

Despite the highest burden of Typhoid fever in children globally, exact estimates of morbidity and mortality are lacking due to scarcity of published data. Despite a high prevalence and a socioeconomic burden in developing countries, published data with morbidity and mortality figures are limited especially Africa and South American regions. Data from the community is insufficient and most case fatality estimates are extrapolations from hospital based studies that do not cover all geographical regions, and include cases which may or not be culture confirmed, MDR resistant or sensitive cases, or from mixed populations of age (adults and children). Complications of typhoid such as intestinal perforation, bone marrow suppression, and encephalopathy are dependent on MDR/Fluoroquinolone resistant Salmonella infection, comorbidities such as malnutrition, and health-care access. Data is again insufficient to estimate the true burden of Typhoid Fever in different regions and groups of populations. Although there has been a rapid decline in cases in developed countries with the advent of improved sanitization, timely and easy access to health care and laboratories, this is still not the case in the developing countries where Typhoid deaths are still occurring. The way forward is to develop rapid and cost effective point of care diagnostic tests, put in place validated clinical algorithms for suspected clinical cases, and design prospective, and community based studies in different groups, implement maintenance of electronic health records in large public sector hospitals and regions to identify populations that will benefit most from the implementation of vaccine. Policies on public health education and typhoid vaccine may help to reduce morbidity and mortality due to the disease.

Typhoid vaccination for international travelers from Greece visiting developing countries.

BACKGROUND: Typhoid fever is one of the most common diagnoses in returned international travelers. Our aim was to study the typhoid vaccine prescription practices for travelers from Greece visiting developing countries. METHODS: A prospective questionnaire-based study was conducted during 2009-2012 in 57 Public Health Departments, which are the only sources of typhoid vaccine in Greece. RESULTS: A total of 3,680 travelers were studied (median age: 38.1 years). Typhoid vaccine was delivered to 1,108 (30.1%) of them. Of those who traveled to sub-Saharan Africa, South America, the Middle East, the Indian subcontinent, Southeast Asia, South Africa, East Asia, North Africa, and Central America, 31.6, 17.1, 35, 44.2, 36.9, 31, 17.7, 31.6, and 36.8% received typhoid vaccine, respectively. Of travelers who stayed <1 month, 1 to <3 months, 3 to <6 months, and ≥6 months, 21.4, 63.1, 32.3, and 34.9% were vaccinated, respectively. According to the purpose of travel, typhoid vaccine was administered to 32.7% of those who traveled for leisure, to 28.8% of those who traveled for business, and to 24.1% of those visiting friends and relatives (VFRs). Of travelers who stayed in urban areas, rural areas, and urban and rural areas, 36.3, 30.1, and 26.8% were vaccinated, respectively. The majority of travelers who received the typhoid vaccine stayed in camps (62.9%) or at local residences (41%). Typhoid vaccine administration was statistically significantly associated with destination, duration of travel, purpose of travel, area of stay, and type of accommodation. DISCUSSION: There is a need to increase awareness of travelers and public health professionals for typhoid vaccination and particularly for high-risk groups of travelers, such as travelers to the Indian subcontinent and VFRs. Strategies for continuing professional education should be developed for travel health professionals.

Immune adjuvant effect of V. cholerae O1 derived Proteoliposome coadministered by intranasal route with Vi polysaccharide from Salmonella Typhi.

The proteoliposome derived from Vibrio cholerae O1 (PLc) is a nanoscaled structure obtained by a detergent extraction process. Intranasal (i.n) administration of PLc was immunogenic at mucosal and systemic level vs. V. cholerae; however the adjuvant potential of this structure for non-cholera antigens has not been proven yet. The aim of this work was to evaluate the effect of coadministering PLc with the Vi polysaccharide antigen (Poli Vi) of S. Typhi by the i.n route. The results showed that Poli Vi coadministered with PLc (PLc+Poli Vi) induce a higher IgA response in saliva (p<0.01) and faeces (p<0.01) than Poli Vi administered alone. Likewise, the IgG response in sera was higher in animals immunised with PLc+Poli Vi (p<0.01). Furthermore, IgG induced in sera of mice immunised with PLc+Poli Vi was similar (p>0.05) to that induced in a group of mice immunised by the parenteral route with the Cuban anti-typhoid vaccine vax-TyVi, although this vaccine did not induce a mucosal response. In conclusion, this work demonstrates that PLc can be used as a mucosal adjuvant to potentiate the immune response against a polysaccharide antigen like Poli Vi.

Immunogenicity of a new Salmonella Typhi Vi polysaccharide vaccine--vax-TyVi--in Cuban school children and teenagers.

A randomized, controlled, double blind study was carried out in Cuban children and teenagers aged 9-13 years to evaluate the immunogenicity of vax-TyVi-Salmonella Typhi Vi polysaccharide vaccine-with respect control vaccines. Serum samples were taken before and 21 days after the immunization, and ELISA was used for the determination of antibodies to Vi polysaccharide. Subjects who received vax-TyVi and TYPHIM Vi (Pasteur-Mérieux) showed seroconversion rates of 85.61 and 78.36%, respectively. The geometric mean titer (GMT) values for Vi antibodies induced after vaccination were 6.27 microg/ml (5.40-7.38 microg/ml) and 5.97 microg/ml (5.01-7.10 microg/ml), respectively. In contrast, subjects receiving the tetanus toxoid vaccine showed 0% seroconversion.

Fiebre tifoidea: brote epidémico en el reten de Catia: diciembre 1991-Septiembre 1992: Hospital General del Oeste / Thiphoid fever: epidemie outbreaks in the reten of Catia: december 1991-September 1992: General Hospital of the west

Evaluamos 23 historias médicas con diagnóstico de fiebre tifoidea, de pacientes provenientes del Reten de Catia durante el período Diciembre 1991 -Septiembre 1992. Conseguimos edad, sexo, ocurrencia estacional, motivo de consulta, sintomas, signos complicaciones, paraclínicos y mortalidad. Todos los pacientes fueron varones con edad promedio de 25-78 años. El mayor número de casos ocurrió en Mayo 1992, el tiempo de convalescencia fue de 41-57 días. Los hallazgos más frecuenttes fueron: como motivos de consulta y datos de la enfermedad actual, fiebre, disminución de peso, diarrea, dolor abdominal, taquicardia, hipotensión taquipnea al examen físico y perforación intestinal y sepsis como complicaciones Serología y cultivos fuerron positivos en un 69.57 por ciento y 43.48 por ciento respectivamente. Encontramos elevado porcentaje de complicaciones y alta mortalidad debido al traslado tardio de los pacientes al hospital (entre la tercera y cuarta semana). Sugerimos medidas preventivas

Vacunación contra la fiebre tifoidea / Vaccination against typhoid fever

La fiebre tifoidea es una enfermedad infecciosa aguda y febril causada por Salmonella typhi. La infección se adquiere por medio de la ingestión de alimentos o agua masivamente contaminados con la bacteria. Debido a que este microorganismo afecta sólo al ser humano y no hay reservorios animales, el elemento más importante en la cadena de transmisión son los individuos que no presentan sintomatología clínica pero son portadores y excretores activos del agente (portadores asintomáticos). En México, la enfermedad tiene características endémico-epidémicas relacionadas con deficiencias en el saneamiento ambiental y el aprovisionamiento de agua potable. La tasa de letalidad es de alrededor del 1 por ciento, sin embargo en los casos complicados puede ascender hasta el 30 por ciento. La vacuna que se utiliza más ampliamente en la actualidad es la inactivada por calor y fenol, la cual tiene efectos colaterales debido al LPS que siempre lo contamina. Además, confiere protección parcial y de corta duración, por lo tanto su empleo se ha limitado a grupos considerados como de alto riesgo y no está indicada en niños. La vacuna de Germanier -mutante avirulenta de Salmonella que se administra por vía oral- proteje hasta un 95 por ciento, siempre y cuando antes de administrarse se neutralice el jugo gástrico, aunque su utilización general en Salud Pública es impráctica. Ya que las porinas son buenos inmunógenos en modelos animales, la obtención de un conjugado antígenico Vi-porinas puede ser una excelente opción como vacuna contra la fiebre tifoidea

[Typhoid fever in school children: by what measures is the modification of the clinical course due to oral vaccination?]. / Fiebre tifoidea en escolares: en que medida la clinica es modificada por el uso de una vacuna oral?

The clinical course of infection by Salmonellae was compared between patients who had been vaccinated against typhoid fever using the Ty21a vaccine and those who had not. Of 2566 bacteriological confirmed cases 84% were infected with S typhi, 14% with S paratyphi B and 2% with S paratyphi A. Among patients with typhoid fever, 34% were treated in hospital, 3.5% had relapses, 5.4% developed complications and 1 patient died (0.05%). Among patients with paratyphoid fever, 18% were treated in hospital, 0.6% had relapses, 1.4% developed complications and there were no deaths. These figures were similar among vaccinated and non-vaccinated cases. A slightly greater proportion of vaccinated cases were treated in hospital (38 vs 30%). Thus, use of oral vaccination against typhoid fever does not alter the clinical course of infection with Salmonellae.

Efficacy of one or two doses of Ty21a Salmonella typhi vaccine in enteric-coated capsules in a controlled field trial. Chilean Typhoid Committee.

Typhoid fever remains an important public health problem in many areas of the world and an effective, non-reactogenic vaccine would be useful to control this disease. An attenuated Salmonella typhi strain (Ty21a), which has shown promise in previous trials, was evaluated in a controlled field trial in Santiago, Chile. In this trial, 82,543 schoolchildren were randomly assigned to receive one or two doses of Ty21a vaccine in enteric-coated capsules or placebo. The enteric-coated vaccine formulation was well tolerated and practical for mass oral immunization. In the first two years of surveillance, 213 cases of bacteriologically-confirmed typhoid fever were found in schoolchildren participating in the trial; annual rates in the placebo group were 139 and 227 per 100,000. Vaccine efficacy in the first two years after vaccination was 59% for two doses and 29% for one dose; no efficacy was found 3-5 years after vaccination. These results indicate that it will be necessary to identify a vaccine formulation and schedule for Ty21a S. typhi that is practical and provides high level protection for greater than 2 years.

Large-scale field trial of Ty21a live oral typhoid vaccine in enteric-coated capsule formulation.

Three doses, given within one week, of Ty21a attenuated Salmonella typhi oral vaccine in an enteric-coated formulation provided 67% efficacy for at least 3 years in a randomised, placebo-controlled field trial involving 109,000 schoolchildren in Santiago, Chile. Increasing the interval between doses to twenty-one days did not enhance protection. Significantly less protection followed administration of vaccine in gelatin capsules with sodium bicarbonate. Ty21a provides the same level of protection as the heat/phenol-inactivated whole cell parenteral vaccine but differs in not causing adverse reactions. Ty21a may now be regarded as a practical public health tool.

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.