Kinetics of the Natural, Humoral Immune Response to<i>Salmonella enterica</i>Serovar Typhi in Kathmandu, Nepal

Pulickal, Anoop S.; Gautam, Samir C.; Clutterbuck, Elizabeth A.; Thorson, Stephen; Basynat, Buddha; Adhikari, Neelam; Makepeace, Katherine; Rijpkema, Sjoerd; Borrow, Ray; Farrar, Jeremy; Pollard, Andrew J.

doi:10.1128/cvi.00245-09

Cited by 57 publications

(57 citation statements)

References 26 publications

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“…Horizontal lines indicate mean titers, and error bars indicate SE. (36). The assays described in our work, if implemented in vaccine or natural typhoid studies, could aid in vaccine development by analyzing whether S. Typhi-specific antibodies have bactericidal roles, rather than measuring antibody titers.…”

Section: Discussionmentioning

confidence: 99%

“…The bactericidal activity of anti-Vi (capsule) antibodies is predominantly IgG2 mediated (36). Early work on the typhoid vaccine Ty21a showed that IgA played a role in antibodydependent cell cytotoxicity of S. Typhi (9,42,43).…”

Section: Discussionmentioning

confidence: 99%

“…Recent work in Nepal demonstrated that individuals living in a region where typhoid is endemic have serum antibodies with bactericidal activity against S. Typhi (36). To further explore the functional activity of S. Typhi antibodies, we tested our samples for antibodymediated, complement-dependent killing using serum bactericidal assays (SBA), as previously described (36). The bactericidal antibody titer is defined as the inverse of the serum dilution at which Յ50% of the initial bacteria survive.…”

Section: Vol 79 2011mentioning

confidence: 99%

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Antibodies in Action: Role of Human Opsonins in Killing Salmonella enterica Serovar Typhi

et al. 2011

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Although vaccines have been available for over a century, a correlate of protection for typhoid fever has yet to be identified. Antibodies are produced in response to typhoid infection and vaccination and are generally used as the gold standard for determining vaccine immunogenicity, even though their role in clearance of Salmonella enterica serovar Typhi infections is poorly defined. Here, we describe the first functional characterization of S. Typhi-specific antibodies following vaccination with a new vaccine, M01ZH09 (Ty2 ⌬aroC ⌬ssaV). We determined that postvaccination sera increased the uptake of wild-type S. Typhi by human macrophages up to 2.3-fold relative to prevaccination (day 0) or placebo samples. These results were recapitulated using immunoglobulins purified from postvaccination serum, demonstrating that antibodies were largely responsible for increases in uptake. Imaging verified that macrophages internalized 2-to 9.5-fold more S. Typhi when the bacteria were opsonized with postvaccination sera than when the bacteria were opsonized with day 0 or placebo sera. Once inside macrophages, the survival of S. Typhi was reduced as much as 50% when opsonized with postvaccination sera relative to day 0 or placebo serum samples. Lastly, bactericidal assays indicated that antibodies generated postvaccination were recognized by complement factors and assisted in killing S. Typhi: mean postvaccination bactericidal antibody titers were higher at all time points than placebo and day 0 titers. These data clearly demonstrate that there are at least two mechanisms by which antibodies facilitate killing of S. Typhi. Future work could lead to improved immunogenicity tests associated with vaccine efficacy and the identification of correlates of protection against typhoid fever.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Vol 79 2011mentioning

confidence: 99%

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Antibodies in Action: Role of Human Opsonins in Killing Salmonella enterica Serovar Typhi

et al. 2011

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“…We previously measured antibody-dependent complement-mediated SBAs in the serum samples of mice immunized with a live attenuated S. Paratyphi A vaccine using an adaptation of the Vibrio cholerae serum vibriocidal assay that employs guinea pig complement (GPC) (14). Other groups have successfully used 3-to 4-week-old baby rabbit complement (BRC) in SBA assays to evaluate S. Typhi vaccines (23,24). Similarly, BRC was employed in an S. Typhimurium SBA assay, although very high concentrations (75%) of complement were required to mediate killing by the antibody (25).…”

mentioning

confidence: 99%

Serum Bactericidal Assays To Evaluate Typhoidal and Nontyphoidal Salmonella Vaccines

Boyd

Tennant

Saague

et al. 2014

Clin. Vaccine Immunol.

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Invasive Salmonella infections for which improved or new vaccines are being developed include enteric fever caused by Salmonella enterica serovars Typhi, Paratyphi A, and Paratyphi B and sepsis and meningitis in young children in sub-Saharan Africa caused by nontyphoidal Salmonella (NTS) serovars, particularly S. enterica serovars Typhimurium and Enteritidis. Assays are needed to measure functional antibodies elicited by the new vaccines to assess their immunogenicities and potential protective capacities. We developed in vitro assays to quantify serum bactericidal antibody (SBA) activity induced by S. Typhi, S. Paratyphi A, S. Typhimurium, and S. Enteritidis vaccines in preclinical studies. Complement from various sources was tested in assays designed to measure antibody-dependent complement-mediated killing. Serum from rabbits 3 to 4 weeks of age provided the best complement source compared to serum from pigs, goats, horses, bovine calves, or rabbits 8 to 12 weeks of age. For S. Enteritidis, S. Typhimurium, and S. Typhi SBA assays to be effective, bacteria had to be harvested at log phase. In contrast, S. Paratyphi A was equally susceptible to killing whether it was grown to the stationary or log phase. The typhoidal serovars were more susceptible to complement-mediated killing than were the nontyphoidal serovars. Lastly, the SBA endpoint titers correlated with serum IgG anti-lipopolysaccharide (LPS) titers in mice immunized with mucosally administered S. Typhimurium, S. Enteritidis, and S. Paratyphi A but not S. Typhi live attenuated vaccines. The SBA assay described here is a useful tool for measuring functional antibodies elicited by Salmonella vaccine candidates.

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“…As these vaccines enter clinical development, it is important to establish their immunogenicity through relevant, well-characterized immunological assays. There is a growing realization within the vaccinology community that in addition to determining antibody levels through binding assays, it is important to determine the functional, antimicrobial capacity of these antibodies.Although many studies have evaluated anti-Salmonella serum bactericidal and opsonophagocytic antibody activity (2,(8)(9)(10)(11)(12)(13)(14)(15), there is a need for reproducible assays that can be used routinely to characterize functional antibody responses to Salmonella in a standardized manner. We previously developed a complementdependent serum bactericidal antibody (SBA) activity assay that quantifies serum antibody responses to typhoidal (S. Typhi and S. Paratyphi A) and nontyphoidal (S. Typhimurium and S. Enteritidis) Salmonella (16).…”

mentioning

confidence: 99%

Opsonophagocytic Assay To Evaluate Immunogenicity of Nontyphoidal Salmonella Vaccines

Ramachandran

Boyd

MacSwords

et al. 2016

Clin Vaccine Immunol

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Nontyphoidal Salmonella (NTS) invasive infections are an important cause of morbidity and mortality in sub-Saharan Africa. Several vaccines are in development to prevent these infections. We describe an NTS opsonophagocytic killing assay that uses HL-60 cells and baby rabbit complement to quantify functional antibodies elicited by candidate NTS vaccines. Invasive nontyphoidal Salmonella (NTS) infections are increasingly being recognized as an important cause of morbidity and mortality in infants and HIV-infected adults and children in subSaharan Africa (1). Multiple vaccines are currently in development, including live-attenuated vaccines, conjugate vaccines, and generalized modules for membrane antigens against invasive S. Typhimurium and S. Enteritidis (2-7). As these vaccines enter clinical development, it is important to establish their immunogenicity through relevant, well-characterized immunological assays. There is a growing realization within the vaccinology community that in addition to determining antibody levels through binding assays, it is important to determine the functional, antimicrobial capacity of these antibodies.Although many studies have evaluated anti-Salmonella serum bactericidal and opsonophagocytic antibody activity (2,(8)(9)(10)(11)(12)(13)(14)(15), there is a need for reproducible assays that can be used routinely to characterize functional antibody responses to Salmonella in a standardized manner. We previously developed a complementdependent serum bactericidal antibody (SBA) activity assay that quantifies serum antibody responses to typhoidal (S. Typhi and S. Paratyphi A) and nontyphoidal (S. Typhimurium and S. Enteritidis) Salmonella (16). Here, we describe an assay that measures the opsonophagocytic capacity of NTS antibodies based on the wellcharacterized pneumococcus opsonophagocytic activity (OPA), which employs HL-60 phagocytic cells and a standardized source of complement, i.e., baby rabbit complement (BRC) (17,18).The Salmonella OPA assay was evaluated using serum samples from mice that had been vaccinated with live-attenuated NTS vaccines (7). BALB/c mice were orally immunized with 10 9 CFU of S. Typhimurium CVD 1931 or S. Enteritidis CVD 1944 suspended in phosphate-buffered saline (PBS) or given PBS alone on days 0, 28, and 56, as previously described (7) [19]) from overnight cultures were diluted 1 in 1,000 in Hy-Soy medium (0.5% sodium chloride, 1% Hy-Soy [Kerry, Clackmannshire, United Kingdom], and 0.5% Hy-Yest [Kerry]), grown at 37°C to an optical density at 600 nm (OD 600 ) of 0.3, and then diluted to 3 ϫ 10 4 CFU/ml in OPB. Immune and nonimmune sera were heat-inactivated at 56°C for 20 min, and 2-fold serial dilutions in OPB (25 l/well final volume) were performed in a Ubottomed 96-well microplate (Sigma-Aldrich, St. Louis, MO). The bottom row was left without sera to act as a negative control. To each well, 3 ϫ 10 2 CFU of bacterial suspension in 10 l OPB was added. Opsonization of bacteria was allowed to occur for 15 min at 37°C with 5% CO 2 . After incubation, 25 ...

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Kinetics of the Natural, Humoral Immune Response toSalmonella entericaSerovar Typhi in Kathmandu, Nepal

Cited by 57 publications

References 26 publications

Antibodies in Action: Role of Human Opsonins in Killing Salmonella enterica Serovar Typhi

Antibodies in Action: Role of Human Opsonins in Killing Salmonella enterica Serovar Typhi

Serum Bactericidal Assays To Evaluate Typhoidal and Nontyphoidal Salmonella Vaccines

Opsonophagocytic Assay To Evaluate Immunogenicity of Nontyphoidal Salmonella Vaccines

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