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1.
Pol J Microbiol ; 68(2): 173-183, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31257790

RESUMO

In this research, Salmonella species were isolated from the animal, insect and human enteric sources in Faisalabad, Punjab, Pakistan. These species were characterized by different microbiological and molecular techniques including polymerase chain reaction (PCR) by amplification of the 16S rRNA gene. Furthermore, sequencing of the amplicons confirmed all ten isolates as Salmonella strains. The antigenic cross-reactivity was found maximum between the HB1 (strain isolated from honeybee) antiserum and its antigen with an antibody titer of 1:128, while the HB1 antiserum showed a cross-reactive titer range of 1:8 to 1:64. On the basis of the highest geometric mean titer (GMT) shown by the antiserum of the HB1 antigen, it was selected as the best candidate for a cross-reactive live Salmonella oral antigen. Moreover, the HB1 antigen was used a live oral antigen (1 × 1010 CFU/ml) in a safety test in rabbits and proved to be avirulent. During the animal trial, three different oral doses of the HB1 live oral antigen were evaluated in four different rabbits' groups (R1, R2, R3, and R4). The dose number 2 of 0.5 ml (two drops orally and repeated after one week) gave the best GMT measured by indirect hemagglutination (IHA) as compared to the other two doses, while R4 group was kept as control. Results of the challenge protection test also validated the efficacy of the double dose of the HB1 live vaccine, which gave the highest survival percentage. Results of this study lay the foundation for a potential cross-reactive live oral Salmonella vaccine that has proved to be immunogenic in rabbits.In this research, Salmonella species were isolated from the animal, insect and human enteric sources in Faisalabad, Punjab, Pakistan. These species were characterized by different microbiological and molecular techniques including polymerase chain reaction (PCR) by amplification of the 16S rRNA gene. Furthermore, sequencing of the amplicons confirmed all ten isolates as Salmonella strains. The antigenic cross-reactivity was found maximum between the HB1 (strain isolated from honeybee) antiserum and its antigen with an antibody titer of 1:128, while the HB1 antiserum showed a cross-reactive titer range of 1:8 to 1:64. On the basis of the highest geometric mean titer (GMT) shown by the antiserum of the HB1 antigen, it was selected as the best candidate for a cross-reactive live Salmonella oral antigen. Moreover, the HB1 antigen was used a live oral antigen (1 × 1010 CFU/ml) in a safety test in rabbits and proved to be avirulent. During the animal trial, three different oral doses of the HB1 live oral antigen were evaluated in four different rabbits' groups (R1, R2, R3, and R4). The dose number 2 of 0.5 ml (two drops orally and repeated after one week) gave the best GMT measured by indirect hemagglutination (IHA) as compared to the other two doses, while R4 group was kept as control. Results of the challenge protection test also validated the efficacy of the double dose of the HB1 live vaccine, which gave the highest survival percentage. Results of this study lay the foundation for a potential cross-reactive live oral Salmonella vaccine that has proved to be immunogenic in rabbits.


Assuntos
Antígenos de Bactérias/imunologia , Abelhas/microbiologia , Salmonelose Animal/prevenção & controle , Salmonella typhimurium/imunologia , Salmonella typhimurium/isolamento & purificação , Vacinas Tíficas-Paratíficas/imunologia , Animais , Antígenos de Bactérias/administração & dosagem , DNA Bacteriano/genética , Fezes/microbiologia , Reação em Cadeia da Polimerase , RNA Ribossômico 16S/genética , Coelhos , Salmonelose Animal/microbiologia , Salmonella typhimurium/classificação
3.
Vaccine ; 36(31): 4725-4733, 2018 07 25.
Artigo em Inglês | MEDLINE | ID: mdl-29958737

RESUMO

BACKGROUND: We have previously demonstrated that polyfunctional Ty21a-responsive CD4+ and CD8+ T cells are generated at the duodenal mucosa 18 days following vaccination with live-attenuated S. Typhi (Ty21a). The longevity of cellular responses has been assessed in peripheral blood, but persistence of duodenal responses is unknown. METHODS: We vaccinated eight healthy adults with Ty21a. Peripheral blood and duodenal samples were acquired after a median of 1.5 years (ranging from 1.1 to 3.7 years) following vaccination. Cellular responses were assessed in peripheral blood and at the duodenal mucosa by flow cytometry. Levels of IgG and IgA were also assessed in peripheral blood by enzyme-linked immunosorbent assay. RESULTS: No T-cell responses were observed at the duodenal mucosa, but CD4+ T-cell responses to Ty21a and FliC were observed in peripheral blood. Peripheral anti-lipopolysaccharide IgG and IgA responses were also observed. Early immunoglobulin responses were not associated with the persistence of long-term cellular immune responses. CONCLUSIONS: Early T-cell responses which we have previously observed at the duodenal mucosa 18 days following oral vaccination with Ty21a could not be detected at a median of 1.5 years. Peripheral responses were observed at this time. Immunoglobulin responses observed shortly after vaccination were not associated with cellular immune responses at 1.5 years, suggesting that the persistence of cellular immunity is not associated with the strength of the initial humoral response to vaccination.


Assuntos
Duodeno/imunologia , Imunidade Celular , Imunidade nas Mucosas , Salmonella typhi/imunologia , Linfócitos T/imunologia , Vacinas Tíficas-Paratíficas/imunologia , Adulto , Ensaio de Imunoadsorção Enzimática , Feminino , Voluntários Saudáveis , Humanos , Imunidade Humoral , Imunoglobulina A/sangue , Imunoglobulina G/sangue , Masculino , Fatores de Tempo , Vacinas Tíficas-Paratíficas/administração & dosagem , Adulto Jovem
4.
Molecules ; 23(7)2018 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-30018230

RESUMO

Typhoid fever due to Salmonella Typhi and invasive nontyphoidal Salmonella (iNTS) infections caused by serovars Enteritidis (SE) and Typhimurium (STm) are major pediatric health problems in sub-Saharan Africa. Typhoid has high complication rates, and iNTS infections have high case fatality rates; moreover, emerging antimicrobial resistance is diminishing treatment options. Vi capsule-based typhoid conjugate vaccine (Typbar-TCV™), licensed in India and pre-qualified by the World Health Organization, elicits durable immunity when administered to infants, but no iNTS vaccines are licensed or imminent. We have developed monovalent SE and STm glycoconjugate vaccines based on coupling lipopolysaccharide-derived core-O polysaccharide (COPS) to phase 1 flagellin protein (FliC) from the homologous serovar. Herein, we report the immunogenicity of multivalent formulations of iNTS COPS:FliC conjugates with Typbar-TCV™. Rabbits immunized with the trivalent typhoid-iNTS glycoconjugate vaccine generated high titers of serum IgG antibody to all three polysaccharide antigens for which anti-COPS IgG antibodies were directed primarily against serogroup-specific OPS epitopes. Responses to SE and STm FliC were lower relative to anti-COPS titers. Post-vaccination rabbit sera mediated bactericidal activity in-vitro, and protected mice after passive transfer against challenge with virulent SE or STm Malian blood isolates. These results support accelerated progression to clinical trials.


Assuntos
Anticorpos Antibacterianos/imunologia , Glicoconjugados , Imunogenicidade da Vacina , Salmonella typhi , Febre Tifoide , Vacinas Tíficas-Paratíficas , Animais , Glicoconjugados/química , Glicoconjugados/imunologia , Glicoconjugados/farmacologia , Coelhos , Salmonella typhi/química , Salmonella typhi/imunologia , Febre Tifoide/imunologia , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/química , Vacinas Tíficas-Paratíficas/imunologia , Vacinas Tíficas-Paratíficas/farmacologia
5.
Vaccine ; 36(28): 4014-4022, 2018 06 27.
Artigo em Inglês | MEDLINE | ID: mdl-29861180

RESUMO

Salmonella is one of the key global causes of food and water borne enteric infections, responsible for significant morbidity and mortality worldwide especially in developing countries. Currently available vaccines against typhoid are moderately effective with several side effects and not efficacious against all Salmonella serovars. Due to limitations of these vaccines and emerging threats of multidrug resistance, developing an effective vaccine against these infections has increasingly become a priority. Heat shock proteins (Hsps), being evolutionarily conserved, represent dominant antigens in the host immune response. In continuation of our earlier studies on the development of S. Typhi DnaK and GroEL vaccine candidates, highly efficacious against Salmonella and multiple pathogens, in the present study, we have designed multi-epitope vaccine candidates common to multiple serovars of Salmonella using bioinformatics approach. Implementing various immunoinformatics tools such as IEDB, EpiJen, BCPRED, ElliPro and VaxiJen, led to the identification of many immunogenic B and T cell epitopes. The 3-D structure model of DnaK was generated to predict conformational B-cell epitopes using ElliPro server. Most promising T cell epitopes (29 CTLs, 18 T-helper cells) were selected based on their binding efficiency with commonly occurring MHC alleles. Finally we narrowed down to 5 protective antigenic peptides (PAPs), comprising highly conserved, antigenic and immunogenic B /T cell epitopes, least homologous with human host. These PAPs were predicted to be non-allergenic by allergenicity prediction tools (SORTALLER and AllerHunter). Hence, these immunogenic epitopes can be used for prophylactic or therapeutic usages specifically to defeat antibiotic-resistant Salmonella. These antigens have been reported for the first time and their conserved nature endow them as potential future vaccine candidates against other multiple pathogens as well.


Assuntos
Proteínas de Bactérias/imunologia , Epitopos de Linfócito B/imunologia , Epitopos de Linfócito T/imunologia , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/imunologia , Vacinas de Subunidades/imunologia , Antígenos de Bactérias/química , Antígenos de Bactérias/genética , Antígenos de Bactérias/imunologia , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Simulação por Computador , Epitopos de Linfócito B/genética , Epitopos de Linfócito T/genética , Humanos , Conformação Proteica , Vacinas Tíficas-Paratíficas/genética , Vacinas de Subunidades/genética , Vacinas Sintéticas/genética , Vacinas Sintéticas/imunologia
6.
Vaccine ; 36(26): 3794-3801, 2018 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-29776750

RESUMO

BACKGROUND: Typhoid fever remains a major public health problem in low- and middle-income countries where children aged 2-14 years bear the greatest burden. Vi polysaccharide is poorly immunogenic in children <2 years of age, and protection in adults is modest. The limitations of Vi polysaccharide vaccines can be overcome by conjugation of the Vi to a carrier protein. A typhoid conjugate vaccine composed of Vi polysaccharide conjugated to diphtheria toxoid (Vi-DT) has been developed. The Phase I study results are presented here. METHODS: This was a randomized, observer-blinded Phase I study to assess the safety and immunogenicity of Vi-DT compared to Vi polysaccharide vaccine, conducted in Manila, Philippines. Participants enrolled in an age de-escalation manner (18-45, 6-17 and 2-5 years) were randomized between Test (Vi-DT, 25 µg) administered at 0 and 4 weeks and Comparator (Vi polysaccharide, Typhim Vi® and Vaxigrip®, Sanofi Pasteur) vaccines. RESULTS: A total of 144 participants were enrolled (48 by age strata, 24 in Test and Comparator groups each). No serious adverse event was reported in either group. Solicited and unsolicited adverse events were mild or moderate in both groups with the exception of a 4-year old girl in Test group with grade 3 fever which resolved without sequelae. All participants in Test group seroconverted after first and second doses of Vi-DT while the proportions in the Comparator group were 97.1% and 97.2%, after first dose of Typhim Vi® and second dose of Vaxigrip®, respectively. Vi-DT showed 4-fold higher Geometric Mean Titers (GMT) compared to Typhim Vi® (adjusted for age strata, p < 0.001). No further increase of GMT was detected after the second dose of Vi-DT. Anti-DT IgG seroresponse rates were 81.2% and 84.5% post first and second Vi-DT doses, respectively. CONCLUSIONS: Vi-DT vaccine was safe, well-tolerated and immunogenic in participants aged 2-45 years. ClinicalTrials.gov registration number: NCT02645032.


Assuntos
Polissacarídeos Bacterianos/imunologia , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/efeitos adversos , Vacinas Tíficas-Paratíficas/imunologia , Adolescente , Adulto , Anticorpos Antibacterianos/sangue , Criança , Pré-Escolar , Toxina Diftérica/imunologia , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/epidemiologia , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/patologia , Feminino , Voluntários Saudáveis , Humanos , Masculino , Pessoa de Meia-Idade , Filipinas , Método Simples-Cego , Vacinas Tíficas-Paratíficas/administração & dosagem , Vacinas Conjugadas/administração & dosagem , Vacinas Conjugadas/efeitos adversos , Vacinas Conjugadas/imunologia , Adulto Jovem
7.
Vaccine ; 36(28): 4134-4141, 2018 06 27.
Artigo em Inglês | MEDLINE | ID: mdl-29801999

RESUMO

All-trans retinoic acid (ATRA) up-regulates, in laboratory animals, the expression of the gut homing markers α4ß7 integrin and CCR9 on lymphocytes, increasing their gut tropism. Here, we show that, in healthy adult volunteers, ATRA induced an increase of these gut homing markers on T cells in vivo in a time dependent manner. The coordinated increase of α4ß7 and CCR9 by ATRA was seen in 57% (12/21) of volunteers and only when given together with an oral Vivotif vaccine. When this coordinated response to ATRA and Vivotif vaccine was present, it was strongly correlated with the gut immunoglobulin A (IgA) specific response to vaccine LPS (ρ = 0.82; P = 0.02). Using RNA-Seq analysis of whole blood transcription, patients receiving ATRA and Vivotif in conjunction showed transcriptomic changes in immune-related pathways, particularly including interferon α/ß signaling pathway, membrane-ECM interactions and immune hubs. These results suggest that exogenous ATRA can be used to manipulate responses to a subclass of oral vaccines, so far limited to a live attenuated Vivotif vaccine.


Assuntos
Adjuvantes Imunológicos/administração & dosagem , Vacinas contra Cólera/imunologia , Trato Gastrointestinal/imunologia , Polissacarídeos Bacterianos/imunologia , Vacinas contra Rotavirus/imunologia , Linfócitos T/imunologia , Tretinoína/administração & dosagem , Vacinas Tíficas-Paratíficas/imunologia , Administração Oral , Adolescente , Adulto , Animais , Vacinas contra Cólera/administração & dosagem , Perfilação da Expressão Gênica , Voluntários Saudáveis , Humanos , Imunoglobulina A/análise , Fatores Imunológicos/biossíntese , Integrinas/análise , Lipopolissacarídeos/imunologia , Masculino , Pessoa de Meia-Idade , Polissacarídeos Bacterianos/administração & dosagem , Receptores CCR/análise , Vacinas contra Rotavirus/administração & dosagem , Linfócitos T/química , Linfócitos T/efeitos dos fármacos , Vacinas Tíficas-Paratíficas/administração & dosagem , Vacinas Atenuadas/administração & dosagem , Vacinas Atenuadas/imunologia , Adulto Jovem , Zâmbia
8.
Vaccine ; 36(21): 2978-2984, 2018 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-29681410

RESUMO

Immune responses to poorly immunogenic antigens, such as polysaccharides, can be enhanced by conjugation to carriers. Our previous studies indicate that conjugation to Vi polysaccharide of Salmonella Typhi may also enhance immunogenicity of some protein carriers. We therefore explored the possibility of generating a bivalent vaccine against Plasmodium falciparum malaria and typhoid fever, which are co-endemic in many parts of the world, by conjugating Vi polysaccharide, an approved antigen in typhoid vaccine, to Pfs25, a malaria transmission blocking vaccine antigen in clinical trials. Vi-Pfs25 conjugates induced strong immune responses against both Vi and Pfs25 in mice, whereas the unconjugated antigens are poorly immunogenic. Functional assays of immune sera revealed potent transmission blocking activity mediated by anti-Pfs25 antibody and serum bactericidal activity due to anti-Vi antibody. Pfs25 conjugation to Vi modified the IgG isotype distribution of antisera, inducing a Th2 polarized immune response against Vi antigen. This conjugate may be further developed as a bivalent vaccine to concurrently target malaria and typhoid fever.


Assuntos
Transmissão de Doença Infecciosa/prevenção & controle , Vacinas Antimaláricas/imunologia , Malária Falciparum/prevenção & controle , Polissacarídeos Bacterianos/imunologia , Proteínas de Protozoários/imunologia , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/imunologia , Animais , Anticorpos Antiprotozoários/sangue , Atividade Bactericida do Sangue , Feminino , Imunoglobulina G/sangue , Vacinas Antimaláricas/administração & dosagem , Vacinas Antimaláricas/isolamento & purificação , Camundongos , Plasmodium falciparum/imunologia , Salmonella typhi/imunologia , Vacinas Tíficas-Paratíficas/administração & dosagem , Vacinas Tíficas-Paratíficas/isolamento & purificação , Vacinas Combinadas/administração & dosagem , Vacinas Combinadas/imunologia , Vacinas Conjugadas/administração & dosagem , Vacinas Conjugadas/imunologia
9.
Vaccine ; 36(17): 2233-2236, 2018 04 19.
Artigo em Inglês | MEDLINE | ID: mdl-29567032

RESUMO

Live oral rotavirus (RV) vaccines used worldwide are most effective in reducing diarrheal hospitalizations from RV in high income countries and least effective in low income countries where RV remains a prime cause of death in children. Research has failed to fully explain the reason for this difference of efficacy for RV vaccines, an observation made with other live oral vaccines for polio, cholera and typhoid fever. Use of parenteral vaccines have been successful in overcoming this problem for both polio and typhoid and parenteral RV vaccines are now in development. This approach should be pursued for rotavirus vaccine as well because in low income countries where oral RV vaccines have been introduced and are only partially effective, RV remains the most common cause of diarrhea in children under 5 years. The ultimate control of RV diarrheal will likely require both oral and parenteral vaccines.


Assuntos
Infecções por Rotavirus/imunologia , Infecções por Rotavirus/prevenção & controle , Vacinas contra Rotavirus/imunologia , Rotavirus/imunologia , Vacinas Atenuadas/imunologia , Administração Oral , Criança , Cólera/imunologia , Cólera/prevenção & controle , Diarreia/imunologia , Diarreia/prevenção & controle , Humanos , Febre Tifoide/imunologia , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/imunologia
10.
PLoS One ; 12(12): e0189100, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-29287062

RESUMO

In recent years there have been major efforts to develop glycoconjugate vaccines based on the Vi polysaccharide that will protect against Salmonella enterica Typhi infections, particularly typhoid fever, which remains a major public health concern in low-income countries. The design of glycoconjugate vaccines influences the immune responses they elicit. Here we systematically test the response in mice to Vi glycoconjugates that differ in Vi chain length (full-length and fragmented), carrier protein, conjugation chemistry, saccharide to protein ratio and size. We show that the length of Vi chains, but not the ultimate size of the conjugate, has an impact on the anti-Vi IgG immune response induced. Full-length Vi conjugates, independent of the carrier protein, induce peak IgG responses rapidly after just one immunization, and secondary immunization does not enhance the magnitude of these responses. Fragmented Vi linked to CRM197 and diphtheria toxoid, but not to tetanus toxoid, gives lower anti-Vi antibody responses after the first immunization than full-length Vi conjugates, but antibody titres are similar to those induced by full-length Vi conjugates following a second dose. The chemistry to conjugate Vi to the carrier protein, the linker used, and the saccharide to protein ratio do not significantly alter the response. We conclude that Vi length and carrier protein are the variables that influence the anti-Vi IgG response to immunization the most, while other parameters are of lesser importance.


Assuntos
Glicoconjugados/imunologia , Salmonella typhi/imunologia , Vacinas Tíficas-Paratíficas/imunologia , Vacinas Conjugadas/imunologia , Animais , Proteínas de Bactérias/imunologia , Imunoglobulina G/imunologia , Camundongos , Polissacarídeos Bacterianos/imunologia
11.
Vaccine ; 35(51): 7121-7126, 2017 12 18.
Artigo em Inglês | MEDLINE | ID: mdl-29150208

RESUMO

Typhoid fever remains a serious public health problem with a high impact on toddlers and young children. Vaccines against the Vi capsular polysaccharide are efficacious against typhoid fever demonstrating that antibodies against Vi confer protection. The currently licensed Vi typhoid vaccines have however limited efficacy and are manufactured by a complex process from wild-type bacteria. Due to these inherent issues with the current vaccines, an alternative vaccine based on an O-acetylated high molecular weight (HMW) polygalacturonic acid (GelSite-OAc™) was generated. The HMW polygalacturonic acid shares the same backbone as the Vi polysaccharide of Salmonella Typhi. The GelSite-OAc™ has a high molecular weight (>1 × 106 Da) and a high degree of O-acetylation (DOAc) (>5 µmole/mg), both exceeding the potency specifications of the current Vi vaccine. Studies in Balb/c mice demonstrated that GelSite-OAc™ was highly immunogenic, inducing a strong antigen-specific antibody response in a DOAc- and dose-dependent manner which was comparable to or higher than those induced by the licensed Vi vaccine. Importantly, the GelSite-OAc™ was shown to be fully protective in mice against lethal challenge with Salmonella Typhi. Furthermore, the GelSite-OAc™ demonstrated a boosting effect or memory response, exhibiting a >2-fold increase in antibody levels upon the second immunization with either GelSite-OAc™ or the Vi vaccine. This novel boosting effect is unique among polysaccharide antigens and potentially makes GelSite-OAc™ effective in people under 2 years old. Together these results suggest that the GelSite-OAc™ could be a highly effective vaccine against Salmonella Typhi.


Assuntos
Pectinas/imunologia , Polissacarídeos Bacterianos/química , Polissacarídeos Bacterianos/imunologia , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/química , Vacinas Tíficas-Paratíficas/imunologia , Vacinas Sintéticas/imunologia , Acetilação , Animais , Anticorpos Antibacterianos/sangue , Formação de Anticorpos/imunologia , Modelos Animais de Doenças , Imunização Secundária , Imunogenicidade da Vacina , Imunoglobulina G/sangue , Memória Imunológica , Camundongos , Pectinas/administração & dosagem , Pectinas/química , Polissacarídeos Bacterianos/administração & dosagem , Salmonella typhi/imunologia , Febre Tifoide/imunologia , Febre Tifoide/microbiologia , Vacinas Tíficas-Paratíficas/administração & dosagem , Vacinas Sintéticas/administração & dosagem , Vacinas Sintéticas/química
12.
Vaccine ; 35(47): 6359-6366, 2017 11 07.
Artigo em Inglês | MEDLINE | ID: mdl-29031693

RESUMO

Enteric fever has been one of the leading causes of severe illness and deaths worldwide. S. Typhi and S. Paratyphi A, B and C are important enteric fever-causing organisms globally. This infection causes about 21 million cases among which 222,000 typhoid related deaths occurred in 2015. These estimates do not reflect the ultimate and real status of the disease due to the lack of unified diagnostic and proper reporting system from typhoid endemic and other regions. Current control strategies have become increasingly ineffective due to the emergence of multi-drug resistance among the strains. This situation worsens the disease-burden in developing as well as in developed countries. Moreover the emergence of S. Paratyphi A as a major enteric fever-causing organism in several Asian countries, demands a prophylactic measure at this hour. Other than two licensed vaccines of S. Typhi, there are no exsisting vaccines for S. Paratyphi A. Moreover, travelers returning from endemic regions are becoming more susceptible to have these infections. In this situation, a need for bivalent approach is required where a single immunogen (consisting from each organism) will be effective against the disease. In this review, we have focused on the general information about typhoidal fever, its spread and epidemiology in brief and the present status of typhoidal vaccines and its future. This review highlights existing gaps in the typhoidal salmonellae research with a special emphasis on the status of present typhoidal salmonellae vaccine research.


Assuntos
Descoberta de Drogas/tendências , Salmonella paratyphi A/imunologia , Salmonella typhi/imunologia , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/imunologia , Vacinas Tíficas-Paratíficas/isolamento & purificação , Saúde Global , Humanos , Febre Tifoide/epidemiologia
14.
PLoS Negl Trop Dis ; 11(9): e0005912, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28873442

RESUMO

Salmonella enterica serovar Typhi (S. Typhi), the causative agent of the typhoid fever, is a pathogen of great public health importance. Typhoid vaccines have the potential to be cost-effective measures towards combating this disease, yet the antigens triggering host protective immune responses are largely unknown. Given the key role of cellular-mediated immunity in S. Typhi protection, it is crucial to identify S. Typhi proteins involved in T-cell responses. Here, cells from individuals immunized with Ty21a typhoid vaccine were collected before and after immunization and used as effectors. We also used an innovative antigen expressing system based on the infection of B-cells with recombinant Escherichia coli (E. coli) expressing one of four S. Typhi gene products (i.e., SifA, OmpC, FliC, GroEL) as targets. Using flow cytometry, we found that the pattern of response to specific S. Typhi proteins was variable. Some individuals responded to all four proteins while others responded to only one or two proteins. We next evaluated whether T-cells responding to recombinant E. coli also possess the ability to respond to purified proteins. We observed that CD4+ cell responses, but not CD8+ cell responses, to recombinant E. coli were significantly associated with the responses to purified proteins. Thus, our results demonstrate the feasibility of using an E. coli expressing system to uncover the antigen specificity of T-cells and highlight its applicability to vaccine studies. These results also emphasize the importance of selecting the stimuli appropriately when evaluating CD4+ and CD8+ cell responses.


Assuntos
Apresentação do Antígeno , Antígenos de Bactérias/imunologia , Proteínas de Bactérias/imunologia , Polissacarídeos Bacterianos/imunologia , Salmonella typhi/imunologia , Linfócitos T/imunologia , Vacinas Tíficas-Paratíficas/imunologia , Adulto , Antígenos de Bactérias/genética , Proteínas de Bactérias/genética , Escherichia coli/genética , Escherichia coli/metabolismo , Feminino , Citometria de Fluxo , Humanos , Masculino , Pessoa de Meia-Idade , Polissacarídeos Bacterianos/administração & dosagem , Proteínas Recombinantes/genética , Proteínas Recombinantes/imunologia , Vacinas Tíficas-Paratíficas/administração & dosagem , Voluntários , Adulto Jovem
15.
Vaccine ; 35(38): 5081-5088, 2017 09 12.
Artigo em Inglês | MEDLINE | ID: mdl-28802757

RESUMO

Typhoid fever is estimated to cause between 11.9-26.9 million infections globally each year with 129,000-216,510 deaths. Access to improved water sources have reduced disease incidence in parts of the world but the use of efficacious vaccines is seen as an important public health tool for countries with a high disease burden. A new generation of Vi typhoid conjugate vaccines (TCVs), licensed for use in young children and expected to provide longer lasting protection than previous vaccines, are now available. The WHO Strategic Advisory Group of Experts on Immunization (SAGE) has convened a working group to review the evidence on TCVs and produce an updated WHO position paper for all typhoid vaccines in 2018 that will inform Gavi, the Vaccine Alliance's future vaccine investment strategies for TCVs. The Typhoid Vaccine Acceleration Consortium (TyVAC) has been formed through a $36.9 million funding program from the Bill & Melinda Gates Foundation to accelerate the introduction of TCVs into Gavi-eligible countries. In October 2016, a meeting was held to initiate planning of TCV effectiveness studies that will provide the data required by policy makers and stakeholders to support decisions on TCV use in countries with a high typhoid burden. Discussion topics included (1) the latest evidence and data gaps in typhoid epidemiology; (2) WHO and Gavi methods and data requirements; (3) data on TCV efficacy; (4) cost effectiveness analysis for TCVs from mathematical models; (5) TCV delivery and effectiveness study design. Specifically, participants were asked to comment on study design in 3 sites for which population-based typhoid surveillance is underway. The conclusion of the meeting was that country-level decision making would best be informed by the respective selected sites in Africa and Asia vaccinating children aged from 9-months to 15-years-old, employing either an individual or cluster randomized design with design influenced by population characteristics, transmission dynamics, and statistical considerations.


Assuntos
Febre Tifoide/imunologia , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/imunologia , Vacinas Tíficas-Paratíficas/uso terapêutico , Ensaios Clínicos como Assunto , Congressos como Assunto , Humanos , Vacinas Conjugadas/imunologia , Vacinas Conjugadas/uso terapêutico
16.
J Immunol Methods ; 450: 27-33, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-28735760

RESUMO

Efficacious typhoid vaccines for young children will significantly reduce the disease burden in developing world. The Vi polysaccharide based conjugate vaccines (Vi-rEPA) against Salmonella Typhi Vi positive strains has shown high efficacy but may be ineffective against Vi negative S. Typhi. In this study, for the first time, we report the synthesis and evaluation of polysaccharide-protein conjugates of Vi negative S. Typhi as potential vaccine candidates. Four different conjugates were synthesized using recombinant exoprotein A of Pseudomonas aeruginosa (rEPA) and human serum albumin (HSA) as the carrier proteins, using either direct reductive amination or an intermediate linker molecule, adipic acid dihydrazide (ADH). Upon injection into mice, a significantly higher antibody titer was observed in mice administrated with conjugate-1 (OSP-HSA) (P=0.0001) and conjugate 2 (OSP-rEPA) (P≤0.0001) as compared to OSP alone. In contrast, the antibody titer elicited by conjugate 3 (OSPADH-HSA) and conjugate 4 (OSPADH-rEPA) were insignificant (P=0.1684 and P=0.3794, respectively). We conclude that reductive amination is the superior method to prepare the S. Typhi OSP glycoconjugate. Moreover, rEPA was a better carrier protein than HSA. Thus OSP-rEPA conjugate seems to be efficacious typhoid vaccines candidate, it may be evaluated further and recommended for the clinical trials.


Assuntos
ADP Ribose Transferases/imunologia , Toxinas Bacterianas/imunologia , Exotoxinas/imunologia , Antígenos O/imunologia , Polissacarídeos Bacterianos/imunologia , Salmonella typhi/imunologia , Vacinas Tíficas-Paratíficas/imunologia , Fatores de Virulência/imunologia , ADP Ribose Transferases/administração & dosagem , ADP Ribose Transferases/química , Aminação , Animais , Anticorpos Antibacterianos/sangue , Toxinas Bacterianas/administração & dosagem , Toxinas Bacterianas/química , Western Blotting , Eletroforese em Gel de Poliacrilamida , Exotoxinas/administração & dosagem , Exotoxinas/química , Feminino , Imunização , Esquemas de Imunização , Injeções Intraperitoneais , Camundongos Endogâmicos BALB C , Antígenos O/administração & dosagem , Antígenos O/química , Oxirredução , Espectroscopia de Prótons por Ressonância Magnética , Proteínas Recombinantes/imunologia , Albumina Sérica/imunologia , Albumina Sérica Humana , Vacinas Tíficas-Paratíficas/administração & dosagem , Vacinas Tíficas-Paratíficas/química , Vacinas Conjugadas/imunologia , Fatores de Virulência/administração & dosagem , Fatores de Virulência/química
17.
Scand J Immunol ; 86(4): 207-215, 2017 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-28675263

RESUMO

Secondary immunization with polysaccharide vaccines may imply a risk of hyporesponsiveness. Despite the wide use of typhoid Vi capsular polysaccharide vaccine, its potential tendency to hyporesponsiveness has been inadequately addressed. While previous studies have explored serum antibody responses, we applied a more sensitive approach, a single-cell assay for circulating plasmablasts, to compare primary and secondary responses. Twelve subjects received primary and booster doses of the Vi vaccine (Typherix® ) at 30- to 37-month intervals. Plasmablasts specific to the Vi or typhoidal O antigens or cross-reactive with paratyphoid and non-typhoidal Salmonella strains were identified as antibody-secreting cells (ASC) with ELISPOT. Before vaccinations, none had plasmablasts specific to the antigens tested. Twelve of 12 subjects showed a Vi-specific response after primary, but only eight of 12 after booster vaccination. All responded to typhoidal O-9,12 antigen after both immunizations. The geometric mean of plasmablasts specific to the Vi antigen was 59 (95% CI 24-119) and 1 (0-54) IgA + IgG + IgM-ASC/106 peripheral blood mononuclear cell (PBMC) after primary and booster immunizations, respectively, and 20 (9-49) and 56 (29-103) to the O-9,12 antigen. We detected 1 (0-28) and 17 (6-36) ASC/106 PBMC cross-reactive with Salmonella Paratyphi A; 3 (0-30) and 22 (8-48) with S. Paratyphi B; 3 (0-29) and 18 (7-47) with S. Paratyphi C; 19 (10-34) and 51 (26-94) with Salmonella Enteritidis; and 1 (0-35) and 23 (9-52) with Salmonella Typhimurium, respectively. One-third of the vaccinees, although responding to the O-9,12 antigen, failed to respond to the Vi antigen after booster immunization, suggesting hyporesponsiveness in part of the vaccinees. The findings warrant further investigation.


Assuntos
Epitopos/imunologia , Leucócitos Mononucleares/imunologia , Plasmócitos/imunologia , Polissacarídeos Bacterianos/imunologia , Salmonella typhi/imunologia , Febre Tifoide/imunologia , Vacinas Tíficas-Paratíficas/imunologia , Adulto , Células Cultivadas , Reações Cruzadas , ELISPOT , Feminino , Humanos , Imunização Secundária , Masculino , Pessoa de Meia-Idade , Antígenos O/imunologia , Análise de Célula Única
18.
Hum Vaccin Immunother ; 13(9): 2017-2024, 2017 09 02.
Artigo em Inglês | MEDLINE | ID: mdl-28604164

RESUMO

A Typhoid Conjugate Vaccine (TCV) is expected to acquire WHO prequalification soon, which will pave the way for its use in many low- and middle-income countries where typhoid fever is endemic. Thus it is critical to forecast future vaccine demand to ensure supply meets demand, and to facilitate vaccine policy and introduction planning. We forecasted introduction dates for countries based on specific criteria and estimated vaccine demand by year for defined vaccination strategies in 2 scenarios: rapid vaccine introduction and slow vaccine introduction. In the rapid introduction scenario, we forecasted 17 countries and India introducing TCV in the first 5 y of the vaccine's availability while in the slow introduction scenario we forecasted 4 countries and India introducing TCV in the same time period. If the vaccine is targeting infants in high-risk populations as a routine single dose, the vaccine demand peaks around 40 million doses per year under the rapid introduction scenario. Similarly, if the vaccine is targeting infants in the general population as a routine single dose, the vaccine demand increases to 160 million doses per year under the rapid introduction scenario. The demand forecast projected here is an upper bound estimate of vaccine demand, where actual demand depends on various factors such as country priorities, actual vaccine introduction, vaccination strategies, Gavi financing, costs, and overall product profile. Considering the potential role of TCV in typhoid control globally; manufacturers, policymakers, donors and financing bodies should work together to ensure vaccine access through sufficient production capacity, early WHO prequalification of the vaccine, continued Gavi financing and supportive policy.


Assuntos
Política de Saúde , Programas de Imunização , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/imunologia , Países em Desenvolvimento , Doenças Endêmicas , Humanos , Índia/epidemiologia , Pobreza , Febre Tifoide/epidemiologia , Vacinas Tíficas-Paratíficas/administração & dosagem , Vacinas Tíficas-Paratíficas/economia , Vacinação/economia , Vacinas Conjugadas/administração & dosagem , Vacinas Conjugadas/economia , Vacinas Conjugadas/imunologia
19.
J Clin Immunol ; 37(5): 427-433, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28589420

RESUMO

PURPOSE: The specific antibody response to the unconjugated 23-valent pneumococcal polysaccharide vaccine is one of the most common tests used to assess for possible humoral immunodeficiency. The results can be difficult to interpret because most people have been immunized with one or more of the pneumococcal vaccines and there is controversy regarding what constitutes a normal response. To circumvent this problem, we developed an ELISA to measure IgG-specific antibodies to the Salmonella Vi Typhim (S. Typhim) vaccine, a pure polysaccharide vaccine, which is a neoantigen for the vast majority of people in the USA. METHODS: We compared the pre- and post-vaccination serum titers to the Vi Typhim vaccine in healthy controls (n = 22), patients previously diagnosed with a primary immunodeficiency (n = 30), and patients referred for possible humoral immune deficiency (n = 29). We also determined if the S. Typhim vaccine could be used to assess specific antibody responses in people on antibody replacement therapy. RESULTS: Following immunization with the S. Typhim vaccine, we found that a 2-fold increase in titers is 100% sensitive and specific in detecting known humoral immune deficiencies as determined by ROC curve analysis. This cut-off value was successfully applied to possible immune deficiency patients (n = 29), resulting in the diagnosis of seven subjects with humoral immunodeficiency. The use of immunoglobulin replacement therapy did not affect the median response ratios compared to subjects not receiving gammaglobulin. CONCLUSION: This study suggests that measurement of the specific antibody response to the S. Typhim vaccine may have advantages over pneumococcal vaccination in the evaluation of the humoral immune response.


Assuntos
Agamaglobulinemia/diagnóstico , Agamaglobulinemia/imunologia , Anticorpos Antibacterianos/imunologia , Vacinas Tíficas-Paratíficas/imunologia , Adolescente , Adulto , Agamaglobulinemia/sangue , Idoso , Anticorpos Antibacterianos/sangue , Área Sob a Curva , Estudos de Casos e Controles , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Síndromes de Imunodeficiência/sangue , Síndromes de Imunodeficiência/diagnóstico , Síndromes de Imunodeficiência/imunologia , Masculino , Pessoa de Meia-Idade , Polissacarídeos Bacterianos/administração & dosagem , Polissacarídeos Bacterianos/imunologia , Curva ROC , Vacinas Tíficas-Paratíficas/administração & dosagem , Vacinação , Adulto Jovem
20.
Vaccine ; 35(27): 3506-3514, 2017 06 14.
Artigo em Inglês | MEDLINE | ID: mdl-28527687

RESUMO

BACKGROUND: Typhoid fever remains endemic in low- and middle-income countries. Programmatic use of existing vaccines is limited, but upcoming typhoid conjugate vaccines (TCVs) could warrant wider use. We evaluated the cost-effectiveness of five TCV delivery strategies in three urban areas (Delhi and Kolkata, India and Nairobi, Kenya) and two rural settings (Lwak, Kenya and Dong Thap, Vietnam) with varying incidence. METHODS AND FINDINGS: We evaluated routine infant vaccination with and without catch-up campaigns among older individuals. We used a dynamic model of typhoid transmission to simulate cases, hospitalizations, deaths, disability-adjusted life-years (DALY) lost, treatment and intervention costs. We estimated cost-effectiveness (in terms of cost in international dollars (I$) per DALY averted) from the healthcare payer perspective, and assessed how it was influenced by uncertain model parameters. Compared to no vaccination, routine infant vaccination at I$1/dose was cost-saving in Delhi and Dong Thap, "very cost-effective" in Kolkata and Nairobi, and "cost-effective" in Lwak according to World Health Organization thresholds. However, routine vaccination was not the optimal strategy compared to strategies that included a catch-up campaign, which yielded the highest probability of being cost-saving in Delhi and Dong Thap and were most likely to provide a return on investment above a willingness-to-pay threshold of I$1440 in Kolkata, I$2300 in Nairobi, and I$5360 in Lwak. Vaccine price impacted the optimal strategy, and the number of doses required and rate of hospitalization were the primary sources of uncertainty. CONCLUSION: Routine vaccination with TCV would be cost-effective in most settings, and additional one-time catch-up campaigns would also be economically justified.


Assuntos
Análise Custo-Benefício , Febre Tifoide/economia , Febre Tifoide/prevenção & controle , Vacinas Tíficas-Paratíficas/economia , Vacinas Tíficas-Paratíficas/imunologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Criança , Pré-Escolar , Estudos de Coortes , Países em Desenvolvimento , Feminino , Humanos , Lactente , Masculino , Pessoa de Meia-Idade , Vacinas Tíficas-Paratíficas/administração & dosagem , População Urbana , Vacinas Conjugadas/administração & dosagem , Vacinas Conjugadas/economia , Vacinas Conjugadas/imunologia , Adulto Jovem
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