Person: Calderwood, Stephen
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Calderwood, Stephen
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Publication Vibrio cholerae genomic diversity within and between patients(Microbiology Society, 2017) Levade, Inès; Terrat, Yves; Leducq, Jean-Baptiste; Weil, Ana; Mayo-Smith, Leslie M.; Chowdhury, Fahima; Khan, Ashraful I.; Boncy, Jacques; Buteau, Josiane; Ivers, Louise C.; Ryan, Edward; Charles, Richelle; Calderwood, Stephen; Qadri, Firdausi; Harris, Jason; Larocque, Regina; Shapiro, B. JesseCholera is a severe, water-borne diarrhoeal disease caused by toxin-producing strains of the bacterium Vibrio cholerae. Comparative genomics has revealed ‘waves’ of cholera transmission and evolution, in which clones are successively replaced over decades and centuries. However, the extent of V. cholerae genetic diversity within an epidemic or even within an individual patient is poorly understood. Here, we characterized V. cholerae genomic diversity at a micro-epidemiological level within and between individual patients from Bangladesh and Haiti. To capture within-patient diversity, we isolated multiple (8 to 20) V. cholerae colonies from each of eight patients, sequenced their genomes and identified point mutations and gene gain/loss events. We found limited but detectable diversity at the level of point mutations within hosts (zero to three single nucleotide variants within each patient), and comparatively higher gene content variation within hosts (at least one gain/loss event per patient, and up to 103 events in one patient). Much of the gene content variation appeared to be due to gain and loss of phage and plasmids within the V. cholerae population, with occasional exchanges between V. cholerae and other members of the gut microbiota. We also show that certain intra-host variants have phenotypic consequences. For example, the acquisition of a Bacteroides plasmid and non-synonymous mutations in a sensor histidine kinase gene both reduced biofilm formation, an important trait for environmental survival. Together, our results show that V. cholerae is measurably evolving within patients, with possible implications for disease outcomes and transmission dynamics.Publication Cellular and Cytokine Responses to Salmonella enterica Serotype Typhi Proteins in Patients with Typhoid Fever in Bangladesh(The American Society of Tropical Medicine and Hygiene, 2014) Bhuiyan, Saruar; Sayeed, Abu; Khanam, Farhana; Leung, Daniel T.; Rahman Bhuiyan, Taufiqur; Sheikh, Alaullah; Salma, Umme; Larocque, Regina; Harris, Jason; Pacek, Marcin; Calderwood, Stephen; LaBaer, Joshua; Ryan, Edward; Qadri, Firdausi; Charles, RichelleWe assessed interferon-gamma (IFN-γ) responses via enzyme-linked immunosorbent spot (ELISPOT) to a number of S. Typhi antigens in samples from humans with S. Typhi bacteremia and typhoid fever in Bangladesh. Compared with responses in healthy endemic zone controls, there were significantly increased IFN-γ responses at the time of clinical presentation (acute phase) and at convalescence 14–28 days later. The majority (80–90%) of IFN-γ expressing T cells were CD4+. We observed a significant increase in interleukin-17 (IL-17) positive CD4 + T cells at convalescent versus acute stage of infection using an intracellular cytokine staining assay. We also found that stimulated peripheral blood mononuclear cells (PBMCs) produced significantly increased levels of a number of cytokines at the convalescent versus acute phase of infection, including IFN-γ, MIP-1β, sCD40L, TNF-β, IL-13, and IL-9. These results suggest that S. Typhi antigens induce a predominantly Th1 response, but that elevations in other cytokines may be modulatory.Publication Immunogenicity of a Killed Bivalent (O1 and O139) Whole Cell Oral Cholera Vaccine, Shanchol, in Haiti(Public Library of Science, 2014) Charles, Richelle; Hilaire, Isabelle J.; Mayo-Smith, Leslie M.; Teng, Jessica E.; Jerome, J. Gregory; Franke, Molly; Saha, Amit; Yu, Yanan; Kováč, Paul; Calderwood, Stephen; Ryan, Edward; Larocque, Regina; Almazor, Charles P.; Qadri, Firdausi; Ivers, Louise C.; Harris, JasonBackground: Studies of the immunogenicity of the killed bivalent whole cell oral cholera vaccine, Shanchol, have been performed in historically cholera-endemic areas of Asia. There is a need to assess the immunogenicity of the vaccine in Haiti and other populations without historical exposure to Vibrio cholerae. Methodology/Principal Findings We measured immune responses after administration of Shanchol, in 25 adults, 51 older children (6–17 years), and 47 younger children (1–5 years) in Haiti, where cholera was introduced in 2010. A≥4-fold increase in vibriocidal antibody titer against V. cholerae O1 Ogawa was observed in 91% of adults, 74% of older children, and 73% of younger children after two doses of Shanchol; similar responses were observed against the Inaba serotype. A≥2-fold increase in serum O-antigen specific polysaccharide IgA antibody levels against V. cholerae O1 Ogawa was observed in 59% of adults, 45% of older children, and 61% of younger children; similar responses were observed against the Inaba serotype. We compared immune responses in Haitian individuals with age- and blood group-matched individuals from Bangladesh, a historically cholera-endemic area. The geometric mean vibriocidal titers after the first dose of vaccine were lower in Haitian than in Bangladeshi vaccinees. However, the mean vibriocidal titers did not differ between the two groups after the second dose of the vaccine. Conclusions/Significance: A killed bivalent whole cell oral cholera vaccine, Shanchol, is highly immunogenic in Haitian adults and children. A two-dose regimen may be important in Haiti, and other populations lacking previous repeated exposures to V. cholerae.Publication Polymorphic Amplified Typing Sequences (PATS) Strain Typing System Accurately Discriminates a Set of Temporally and Spatially Disparate Escherichia coli O157 Isolates Associated with Human Infection(Bentham Open, 2013) Kudva, Indira T.; Smole, Sandra; Griffin, Robert; Garren, Jeonifer; Kalia, Nimisha; Murray, Megan; John, Manohar; Timperi, Ralph; Calderwood, StephenPolymorphic Amplified Typing Sequences (PATS) is a PCR-based Escherichia coli O157 (O157) strain typing system. Here, we show that PATS compares excellently with Pulsed-Field Gel Electrophoresis (PFGE) in that both methods cluster geographically diverse O157 isolates similarly. Comparative analysis of the results obtained in this simulated “blind” study attests to the discriminating power and applicability of PATS to epidemiological/nosocomial situations.Publication Evaluation in Mice of a Conjugate Vaccine for Cholera Made from Vibrio cholerae O1 (Ogawa) O-Specific Polysaccharide(Public Library of Science, 2014) Alam, Mohammad Murshid; Bufano, Megan Kelly; Xu, Peng; Kalsy, Anuj; Yu, Y.; Freeman, Y. Wu; Sultana, Tania; Rashu, Md. Rasheduzzaman; Desai, Ishaan; Eckhoff, Grace; Leung, Daniel T.; Charles, Richelle; Larocque, Regina; Harris, Jason; Clements, John D.; Calderwood, Stephen; Qadri, Firdausi; Vann, W. F.; Kováč, Pavol; Ryan, EdwardBackground: Protective immunity against cholera is serogroup specific. Serogroup specificity in Vibrio cholerae is determined by the O-specific polysaccharide (OSP) of lipopolysaccharide (LPS). Generally, polysaccharides are poorly immunogenic, especially in young children. Methodology Here we report the evaluation in mice of a conjugate vaccine for cholera (OSP:TThc) made from V. cholerae O1 Ogawa O-Specific Polysaccharide–core (OSP) and recombinant tetanus toxoid heavy chain fragment (TThc). We immunized mice intramuscularly on days 0, 21, and 42 with OSP:TThc or OSP only, with or without dmLT, a non-toxigenic immunoadjuvant derived from heat labile toxin of Escherichia coli. Principal Findings We detected significant serum IgG antibody responses targeting OSP following a single immunization in mice receiving OSP:TThc with or without adjuvant. Anti-LPS IgG responses were detected following a second immunization in these cohorts. No anti-OSP or anti-LPS IgG responses were detected at any time in animals receiving un-conjugated OSP with or without immunoadjuvant, and in animals receiving immunoadjuvant alone. Responses were highest following immunization with adjuvant. Serum anti-OSP IgM responses were detected in mice receiving OSP:TThc with or without immunoadjuvant, and in mice receiving unconjugated OSP. Serum anti-LPS IgM and vibriocidal responses were detected in all vaccine cohorts except in mice receiving immunoadjuvant alone. No significant IgA anti-OSP or anti-LPS responses developed in any group. Administration of OSP:TThc and adjuvant also induced memory B cell responses targeting OSP and resulted in 95% protective efficacy in a mouse lethality cholera challenge model. Conclusion: We describe a protectively immunogenic cholera conjugate in mice. Development of a cholera conjugate vaccine could assist in inducing long-term protective immunity, especially in young children who respond poorly to polysaccharide antigens.Publication A bacteriophage encodes its own CRISPR/Cas adaptive response to evade host innate immunity(2013) Seed, Kimberley D.; Lazinski, David W.; Calderwood, Stephen; Camilli, AndrewPublication Antigen-Specific Memory B-cell Responses to Enterotoxigenic Escherichia coli Infection in Bangladeshi Adults(Public Library of Science, 2014) Alam, Mohammad Murshid; Aktar, Amena; Afrin, Sadia; Rahman, Mohammad Arif; Aktar, Sarmin; Uddin, Taher; Rahman, M. Arifur; Mahbuba, Deena Al; Chowdhury, Fahima; Khan, Ashraful Islam; Bhuiyan, Taufiqur Rahman; Begum, Yasmin Ara; Ryan, Edward; Calderwood, Stephen; Svennerholm, Ann-Mari; Qadri, FirdausiBackground: Multiple infections with diverse enterotoxigenic E. coli (ETEC) strains lead to broad spectrum protection against ETEC diarrhea. However, the precise mechanism of protection against ETEC infection is still unknown. Therefore, memory B cell responses and affinity maturation of antibodies to the specific ETEC antigens might be important to understand the mechanism of protection. Methodology In this study, we investigated the heat labile toxin B subunit (LTB) and colonization factor antigens (CFA/I and CS6) specific IgA and IgG memory B cell responses in Bangladeshi adults (n = 52) who were infected with ETEC. We also investigated the avidity of IgA and IgG antibodies that developed after infection to these antigens. Principal Findings Patients infected with ETEC expressing LT or LT+heat stable toxin (ST) and CFA/I group or CS6 colonization factors developed LTB, CFA/I or CS6 specific memory B cell responses at day 30 after infection. Similarly, these patients developed high avidity IgA and IgG antibodies to LTB, CFA/I or CS6 at day 7 that remained significantly elevated at day 30 when compared to the avidity of these specific antibodies at the acute stage of infection (day 2). The memory B cell responses, antibody avidity and other immune responses to CFA/I not only developed in patients infected with ETEC expressing CFA/I but also in those infected with ETEC expressing CFA/I cross-reacting epitopes. We also detected a significant positive correlation of LTB, CFA/I and CS6 specific memory B cell responses with the corresponding increase in antibody avidity. Conclusion: This study demonstrates that natural infection with ETEC induces memory B cells and high avidity antibodies to LTB and colonization factor CFA/I and CS6 antigens that could mediate anamnestic responses on re-exposure to ETEC and may help in understanding the requirements to design an effective vaccination strategies.Publication Evaluation of a Typhoid/Paratyphoid Diagnostic Assay (TPTest) Detecting Anti-Salmonella IgA in Secretions of Peripheral Blood Lymphocytes in Patients in Dhaka, Bangladesh(Public Library of Science, 2013) Khanam, Farhana; Sheikh, Alaullah; Sayeed, Md. Abu; Bhuiyan, Md. Saruar; Choudhury, Feroza Kaneez; Salma, Umme; Pervin, Shahnaz; Sultana, Tania; Ahmed, Dilruba; Goswami, Doli; Hossain, Md. Lokman; Mamun, K. Z.; Charles, Richelle; Brooks, W. Abdullah; Calderwood, Stephen; Cravioto, Alejandro; Ryan, Edward; Qadri, FirdausiBackground: Rapid and reliable diagnostic assays for enteric (typhoid and paratyphoid) fever are urgently needed. We report the characterization of novel approach utilizing lymphocyte secretions, for diagnosing patients with enteric fever by the TPTest procedure. Methodology TPTest detects Salmonella-specific IgA responses in lymphocyte culture supernatant. We utilized TPTest in patients with suspected enteric fever, patients with other illnesses, and healthy controls. We also evaluated simplified modifications of TPTest for adaptation in laboratories with limited facilities and equipment. Principal Findings TPTest was positive in 39 (27 typhoid and 12 paratyphoid A) patients confirmed by blood culture and was negative in 74 healthy individuals. Among 32 individuals with other illnesses, 29 were negative by TPTest. Of 204 individuals with suspected enteric fever who were negative by blood culture, 44 were positive by TPTest and the patients were clinically indistinguishable from patients with confirmed bacteremia, except they were more likely to be under 5 years of age. We evaluated simplifications in TPTest, including showing that lymphocytes could be recovered using lysis buffer or buffy coat method as opposed to centrifugation, that incubation of cells at 37°C did not require supplemental CO2, and that results were available for majority of samples within 24 hours. Positive results by TPTest are transient and revert to negative during convalescence, supporting use of the test in endemic areas. The results can also be read using immunodot blot approach as opposed to ELISA. Since no true gold standard currently exists, we used a number of definitions of true positives and negatives. TPTest had sensitivity of 100% compared to blood culture, and specificity that ranged from 78–97% (73–100, 95% CI), depending on definition of true negative. Conclusion: The TPTest is useful for identification of patients with enteric fever in an endemic area, and additional development of simplified TPTest is warranted.Publication Identification of Immunogenic Salmonella enterica Serotype Typhi Antigens Expressed in Chronic Biliary Carriers of S. Typhi in Kathmandu, Nepal(Public Library of Science, 2013) Charles, Richelle; Sultana, Tania; Alam, Mohammad Murshid; Yu, Yanan; Wu-Freeman, Ying; Bufano, Meagan Kelly; Rollins, Sean M.; Tsai, Lillian; Harris, Jason; Larocque, Regina; Leung, Daniel T.; Brooks, W. Abdullah; Nga, Tran Vu Thieu; Dongol, Sabina; Basnyat, Buddha; Calderwood, Stephen; Farrar, Jeremy; Khanam, Farhana; Gunn, John S.; Qadri, Firdausi; Baker, Stephen; Ryan, EdwardBackground: Salmonella enterica serotype Typhi can colonize and persist in the biliary tract of infected individuals, resulting in a state of asymptomatic chronic carriage. Chronic carriers may act as persistent reservoirs of infection within a community and may introduce infection to susceptible individuals and new communities. Little is known about the interaction between the host and pathogen in the biliary tract of chronic carriers, and there is currently no reliable diagnostic assay to identify asymptomatic S. Typhi carriage. Methodology/Principal Findings To study host-pathogen interactions in the biliary tract during S. Typhi carriage, we applied an immunoscreening technique called in vivo-induced antigen technology (IVIAT), to identify potential biomarkers unique to carriers. IVIAT identifies humorally immunogenic bacterial antigens expressed uniquely in the in vivo environment, and we hypothesized that S. Typhi surviving in the biliary tract of humans may express a distinct antigenic profile. Thirteen S. Typhi antigens that were immunoreactive in carriers, but not in healthy individuals from a typhoid endemic area, were identified. The identified antigens included a number of putative membrane proteins, lipoproteins, and hemolysin-related proteins. YncE (STY1479), an uncharacterized protein with an ATP-binding motif, gave prominent responses in our screen. The response to YncE in patients whose biliary tract contained S. Typhi was compared to responses in patients whose biliary tract did not contain S. Typhi, patients with acute typhoid fever, and healthy controls residing in a typhoid endemic area. Seven of 10 (70%) chronic carriers, 0 of 8 bile culture-negative controls (0%), 0 of 8 healthy Bangladeshis (0%), and 1 of 8 (12.5%) Bangladeshis with acute typhoid fever had detectable anti-YncE IgG in blood. IgA responses were also present. Conclusions/Significance: Further evaluation of YncE and other antigens identified by IVIAT could lead to the development of improved diagnostic assays to identify asymptomatic S. Typhi carriers.Publication Plasma Leptin Levels in Children Hospitalized with Cholera in Bangladesh(The American Society of Tropical Medicine and Hygiene, 2015) Falkard, Brie; Uddin, Taher; Arifur Rahman, M.; Franke, Molly; Aktar, Amena; Uddin, Muhammad Ikhtear; Bhuiyan, Taufiqur Rahman; Leung, Daniel T.; Charles, Richelle; Larocque, Regina; Harris, Jason; Calderwood, Stephen; Qadri, Firdausi; Ryan, EdwardVibrio cholerae, the cause of cholera, induces both innate and adaptive immune responses in infected humans. Leptin is a hormone that plays a role in both metabolism and mediating immune responses. We characterized leptin levels in 11 children with cholera in Bangladesh, assessing leptin levels on days 2, 7, 30, and 180 following cholera. We found that patients at the acute stage of cholera had significantly lower plasma leptin levels than matched controls, and compared with levels in late convalescence. We then assessed immune responses to V. cholerae antigens in 74 children with cholera, correlating these responses to plasma leptin levels on day 2 of illness. In multivariate analysis, we found an association between day 2 leptin levels and development of later anti-cholera toxin B subunit (CtxB) responses. This finding appeared to be limited to children with better nutritional status. Interestingly, we found no association between leptin levels and antibody responses to V. cholerae lipopolysaccharide, a T cell–independent antigen. Our results suggest that leptin levels may be associated with cholera, including the development of immune responses to T cell–dependent antigens.