Molecular characteristics and antimicrobial resistance of invasive pneumococcal isolates from children in the post-13-valent pneumococcal conjugate vaccine era in Shenzhen, China.

OBJECTIVES: This study aimed to evaluate the molecular epidemiology and antimicrobial resistance of invasive pneumococcal isolates from children in Shenzhen, China, in the early stage of the pneumococcal 13-valent conjugated vaccine (PCV-13) era from 2018 to 2020. METHODS: Invasive pneumococcal strains were isolated from hospitalized children with invasive pneumococcal diseases (IPDs) from January 2018 to December 2020. The serotype identification, multilocus sequence typing (MLST), and antibiotic susceptibility tests were performed on all culture-confirmed strains. RESULTS: Sixty-four invasive strains were isolated mainly from blood (70.3%). Prevalent serotypes were 23F (28.1%), 14 (18.8%), 19F (15.6%), 6A/B (14.1%), and 19A (12.5%), with a serotype coverage rate of 96.9% for PCV13. The most common sequence types (STs) were ST876 (17.1%), ST271 (10.9%), and ST320 (7.8%). Half of the strains were grouped in clonal complexes (CCs): CC271 (21.9%), CC876 (20.3%), and CC90 (14.1%). Meningitis isolates showed a higher resistance rate (90.9% and 45.5%) to penicillin and ceftriaxone than the rate (3.8% and 9.4%) of non-meningitis isolates. The resistance rates for penicillin (oral), cefuroxime, and erythromycin were 53.13%, 73.4%, and 96.9%, respectively. The dual ermB and mefA genotype was found in 81.3% of erythromycin-resistant strains. The elevated minimum inhibitory concentration (MIC) of ß-lactam antibiotics and dual-genotype macrolide resistance were related mainly to three major serotype-CC combinations: 19F-CC271, 19A-CC271, and 14-CC876. CONCLUSION: Invasive pneumococcus with elevated MICs of ß-lactams and increased dual ermB and mefA genotype macrolide resistance were alarming. Expanded PCV13 vaccination is expected to reduce the burden of paediatric IPD and to combat antibiotic-resistant pneumococcus in Shenzhen.

Epidemiology and serotype distribution of Streptococcus pneumoniae carriage among influenza-like illness cases in metropolitan Vientiane, Lao PDR: a community-based cohort study.

Background: Data on the epidemiology of Streptococcus pneumoniae among influenza-like illness (ILI) cases, particularly in low- and middle-income countries are scarce. This study assessed the prevalence, risk factors and serotype distribution of S. pneumoniae carriage among ILI cases in metropolitan Vientiane, Lao People's Democratic Republic. The 13-valent pneumococcal conjugate vaccine (PCV13) was introduced among infants in October 2013. Methods: Active ILI surveillance was conducted through weekly phone calls in an open community-based cohort study (April 2015-February 2019), involving 5,690 participants from 1,142 randomly selected households. Participants reporting ILI symptoms provided a nasopharyngeal swab and answered a questionnaire. S. pneumoniae and serotype pneumococcal-positive samples were screened by Multiplex PCR assays. Chi-squared tests and generalized linear mixed models were used to test for variables associated with pneumococcal positivity. Results: Among 1,621 ILI episodes, 269 (16.6%) tested positive for nasopharyngeal pneumococcal carriage, with the highest prevalence (55.4%) in children under 5 years. Pneumococcal carriage was significantly associated with concurrent detection of Hemophilus influenzae (adjusted odds ratio [aOR]: 6.93; 95% CI: 2.10-22.9) and exposure to household cigarette smoke (aOR: 1.65; 95% CI: 1.07-2.54). PCV13 serotypes accounted for 37.8% of all pneumococcal isolates. Detection of PCV13 serotypes among ILI cases aged under 5 years declined significantly between 2015/16 and 2018/19. Conclusions: Community-based surveillance of S. pneumoniae among ILI cases complement surveillance at healthcare facilities to provide a more complete picture of pneumococcal carriage. Our findings contribute also to the growing body of evidence on the effects of PCV13 introduction on circulating serotypes and their potential replacement.

Serotype Distribution and Antimicrobial Resistance of Streptococcus pneumoniae Causing Invasive Pneumococcal Disease in Korea Between 2017 and 2019 After Introduction of the 13-Valent Pneumococcal Conjugate Vaccine.

Background: Streptococcus pneumoniae is a serious pathogen causing various infections in humans. We evaluated the serotype distribution and antimicrobial resistance of S. pneumoniae causing invasive pneumococcal disease (IPD) after introduction of pneumococcal conjugate vaccine (PCV)13 in Korea and investigated the epidemiological characteristics of multidrug-resistant (MDR) isolates. Methods: S. pneumoniae isolates causing IPD were collected from 16 hospitals in Korea between 2017 and 2019. Serotyping was performed using modified sequential multiplex PCR and the Quellung reaction. Antimicrobial susceptibility tests were performed using the broth microdilution method. Multilocus sequence typing was performed on MDR isolates for epidemiological investigations. Results: Among the 411 S. pneumoniae isolates analyzed, the most prevalent serotype was 3 (12.2%), followed by 10A (9.5%), 34 (7.3%), 19A (6.8%), 23A (6.3%), 22F (6.1%), 35B (5.8%), 11A (5.1%), and others (40.9%). The coverage rates of PCV7, PCV10, PCV13, and pneumococcal polysaccharide vaccine (PPSV)23 were 7.8%, 7.8%, 28.7%, and 59.4%, respectively. Resistance rates to penicillin, ceftriaxone, erythromycin, and levofloxacin were 13.1%, 9.2%, 80.3%, and 4.1%, respectively. MDR isolates accounted for 23.4% of all isolates. Serotypes 23A, 11A, 19A, and 15B accounted for the highest proportions of total isolates at 18.8%, 16.7%, 14.6%, and 8.3%, respectively. Sequence type (ST)166 (43.8%) and ST320 (12.5%) were common among MDR isolates. Conclusions: Non-PCV13 serotypes are increasing among invasive S. pneumoniae strains causing IPD. Differences in antimicrobial resistance were found according to the specific serotype. Continuous monitoring of serotypes and antimicrobial resistance is necessary for the appropriate management of S. pneumoniae infections.

Effect of pneumococcal conjugate vaccine on prevalence of otitis media with effusion among children in Vietnam.

PURPOSE: Otitis media with effusion (OME) is common in young children and is associated with Streptococcus pneumoniae infection. We aimed to determine the impact of pneumococcal conjugate vaccine (PCV) introduction on the prevalence of OME and OME associated with vaccine-type (VT) or non-VT. METHODS: Population-based cross-sectional surveys were conducted in pre- (2016) and post-PCV periods (2017, 2018, and 2019) at selected communes in Nha Trang, Vietnam. For each survey, we randomly selected 60 children aged 4-11 months and 60 aged 14-23 months from each commune. Nasopharyngeal sample collection and tympanic membrane examination by digital otoscope were performed. S. pneumoniae was detected and serotyped by lytA qPCR and microarray. Odds ratios (OR) and 95% confidence intervals (CIs) were calculated using Firth's logistic regression, stratified by age group. RESULTS: Over the four surveys, 2089 children had a bilateral ear examination. Compared to pre-PCV, the prevalence of OME reduced in 2018 (OR 0.51, 95 %CI 0.28-0.93) and in 2019 (OR 0.53, 95 %CI 0.29-0.97) among the <12-month-olds, but no significant reduction among the 12-23-month-olds. The prevalence of OME associated with VT pneumococcus decreased in 2018 and 2019 (2018: OR 0.14, 95 %CI 0.03-0.55; 2019: OR 0.20, 95 %CI 0.05-0.69 in the <12-months-olds, 2018: OR 0.05, 95 %CI 0.00-0.44, 2019: OR 0.41, 95 %CI 0.10-1.61 in the 12-23-months-olds). The prevalence of OME associated with non-VT pneumococcus increased in the 12-23-month-olds in 2017 (OR 3.09, 95 %CI 1.47-7.45) and returned to the pre-PCV level of prevalence in 2018 and 2019 (OR 0.94, 95 %CI 0.40-2.43 and 1.40, 95 %CI 0.63-3.49). CONCLUSION: PCV10 introduction was associated with a reduction of OME prevalence in infants but not in older children.

Effect of childhood vaccination and antibiotic use on pneumococcal populations and genome-wide associations with disease among children in Nepal: an observational study.

BACKGROUND: Pneumococcal disease is a leading cause of bacterial pneumonia and invasive bacterial disease among children globally. The reason some strains of pneumococci are more likely to cause disease, and how interventions such as vaccines and antibiotics affect pneumococcal strains is poorly understood. We aimed to identify genetic regions under selective pressure and those associated with disease through the analysis of pneumococcal whole-genome sequences. METHODS: Whole-genome sequencing was performed on pneumococcal isolates collected between January, 2005, and May, 2018, in Kathmandu, Nepal, which included programmatic ten-valent pneumococcal conjugate vaccine (PCV10) introduction in 2015. Isolates were from three distinct cohorts: nasopharyngeal swabs of healthy community-based children, nasopharyngeal swabs of children admitted to hospital with pneumonia, and sterile-site cultures from children admitted to hospital. Across these cohorts we examined serotype distribution, antibiotic resistance, strain distribution, and regions of recombination to determine genes that were undergoing diversifying selection. Genome-wide association studies comparing pneumonia and sterile-site isolates with healthy carriage were used to determine novel variants associated with disease. FINDINGS: After programmatic introduction of PCV10, there was a decline in vaccine covered serotypes; however, strains that had expressed these serotypes continued to exist in the post-PCV population. We identified GPSC9 to be a strain of concern due to its high prevalence in disease, multidrug resistance, and ability to switch to an unencapsulated phenotype via insertion of virulence factor pspC into the cps locus. Antibiotic resistance loci to co-trimoxazole were found to be prevalent (pre-PCV10 78% vs post-PCV10 81%; p=0·27) and increasingly prevalent to penicillin (pre-PCV10 15% vs post-PCV10 32%; p<0·0001). Regions with multiple recombinations were identified spanning the surface protein virulence factors pspA and pspC and antibiotic targets pbpX, folA, folC, folE, and folP. Furthermore, we identified variants in lacE2 to be strongly associated with isolates from children with pneumonia and PRIP to be strongly associated with isolates from sterile sites. INTERPRETATION: Our work highlights the effect of pneumococcal conjugate vaccines, antibiotics, and host-pathogen interaction in pneumococcal variation, and the pathogen's capability of adapting to these factors at both population-wide and strain-specific levels. Ongoing surveillance of disease-associated strains and further investigation of lacE2 and PRIP as serotype-independent targets for therapeutic interventions is required. FUNDING: Gavi, The Vaccine Alliance; WHO; Bill & Melinda Gates Foundation; Wellcome Sanger Institute; and US Centers for Disease Control and Prevention.

Development of an O-polysaccharide based recombinant glycoconjugate vaccine in engineered E. coli against ExPEC O1.

Extraintestinal pathogenic Escherichia coli O1 is a frequently identified serotype that causes serious infections and is often refractory to antimicrobial therapy. Glycoconjugate vaccine represents a promising measure to reduce ExPEC infections. Herein, we designed an O1-specific glyco-optimized chassis strain for manufacture of O-polysaccharide (OPS) antigen and OPS-based bioconjugate. Specifically, OPS and OPS-based glycoprotein were synthesized in glyco-optimized chassis strain, when compared to the unmeasurable level of the parent strain. The optimal expression of oligosaccharyltransferase and carrier protein further improved the titer. MS analysis elucidated the correct structure of resulting bioconjugate at routine and unreported glycosylation sequons of carrier protein, with a higher glycosylation efficiency. Finally, purified bioconjugate stimulated mouse to generate specific IgG antibodies and protected them against virulent ExPEC O1 challenge. The plug-and-play glyco-optimized platform is suitable for bioconjugate synthesis, thus providing a potential platform for future medical applications.

Rotavirus spike protein ΔVP8* as a novel carrier protein for conjugate vaccine platform with demonstrated antigenic potential for use as bivalent vaccine.

Conjugate vaccine platform is a promising strategy to overcome the poor immunogenicity of bacterial polysaccharide antigens in infants and children. A carrier protein in conjugate vaccines works not only as an immune stimulator to polysaccharide, but also as an immunogen; with the latter generally not considered as a measured outcome in real world. Here, we probed the potential of a conjugate vaccine platform to induce enhanced immunogenicity of a truncated rotavirus spike protein ΔVP8*. ΔVP8* was covalently conjugated to Vi capsular polysaccharide (Vi) of Salmonella Typhi to develop a bivalent vaccine, termed Vi-ΔVP8*. Our results demonstrated that the Vi-ΔVP8* vaccine can induce specific immune responses against both antigens in immunized mice. The conjugate vaccine elicits high antibody titers and functional antibodies against S. Typhi and Rotavirus (RV) when compared to immunization with a single antigen. Together, these results indicate that Vi-ΔVP8* is a potent and immunogenic vaccine candidate, thus strengthening the potential of conjugate vaccine platform with enhanced immune responses to carrier protein, including ΔVP8*.

Molecular characterization and epidemiology of Streptococcus pneumoniae serotype 8 in Denmark.

BACKGROUND: Streptococcus pneumoniae serotype 8 incidence has increased in Denmark after the introduction of pneumococcal conjugated vaccines (PCV). The mechanism behind the serotype 8 replacement is not well understood. In this study, we aimed to present epidemiological data on invasive pneumococcal disease (IPD) and molecular characterization of 96 serotype 8 clinical isolates. METHODS: IPD data from 1999 to 2019 were used to calculate the incidence and age distribution. Whole-genome sequencing (WGS) analysis was performed on 96 isolates (6.8% of the total serotype 8 IPD isolates in the period) to characterize the isolates with respect to pneumococcal lineage traits, a range of genes with potential species discrimination, presence of colonization and virulence factors, and molecular resistance pattern. RESULTS: The serotype 8 IPD incidence increased significantly (P < 0.05) for the age groups above 15 years after the introduction of PCV13, primarily affecting the elderly (65+). All isolates were phenotypically susceptible to penicillin, erythromycin and clindamycin. Molecular characterization revealed seven different MLST profiles with ST53 as the most prevalent lineage (87.5%) among the analyzed serotype 8 isolates. The genes covering the cell-surface proteins: lytA, rspB, pspA, psaA & Xisco and the pneumococcal toxin pneumolysin = ply were present in all isolates, while genes for the membrane transporter proteins: piaA/piaB/piaC; the capsular genes: cpsA (wzg) & psrP; the metallo-binding proteins zmpB & zmpC; and the neuroamidase proteins: nanA/nanB were variably present. Surprisingly, the putative transcriptional regulator gene SP2020 was not present in all isolates (98%). Susceptibility to penicillin, erythromycin and clindamycin was molecularly confirmed. CONCLUSION: The observed serotype 8 replacement was not significantly reflected with a change in the MLST profile or changes in antibiotic resistance- or virulence determinants.

Evaluation of the Immunogenic Response of a Novel Enterobactin Conjugate Vaccine in Chickens for the Production of Enterobactin-Specific Egg Yolk Antibodies.

Passive immunization with specific egg yolk antibodies (immunoglobulin Y, IgY) is emerging as a promising alternative to antibiotics to control bacterial infections. Recently, we developed a novel conjugate vaccine that could trigger a strong immune response in rabbits directed against enterobactin (Ent), a highly conserved siderophore molecule utilized by different Gram-negative pathogens. However, induction of Ent-specific antibodies appeared to be affected by the choice of animal host and vaccination regimen. It is still unknown if the Ent conjugate vaccine can trigger a specific immune response in layers for the purpose of production of anti-Ent egg yolk IgY. In this study, three chicken vaccination trials with different regimens were performed to determine conditions for efficient production of anti-Ent egg yolk IgY. Purified Ent was conjugated to three carrier proteins, keyhole limpet hemocyanin (KLH), bovine serum albumin (BSA) and CmeC (a subunit vaccine candidate), respectively. Intramuscular immunization of Barred Rock layers with KLH-Ent conjugate four times induced strong immune response against whole conjugate vaccine but the titer of Ent-specific IgY did not change in yolk with only a 4 fold increase detected in serum. In the second trial, three different Ent conjugate vaccines were evaluated in Rhode Island Red pullets with four subcutaneous injections. The KLH-Ent or CmeC-Ent conjugate consistently induced high level of Ent-specific IgY in both serum (up to 2,048 fold) and yolk (up to 1,024 fold) in each individual chicken. However, the Ent-specific immune response was only temporarily and moderately induced using a BSA-Ent vaccination. In the third trial, ten White Leghorn layers were subcutaneously immunized three times with KLH-Ent, leading to consistent and strong immune response against both whole conjugate and the Ent molecule in each chicken; the mean titer of Ent-specific IgY increased approximately 32 and 256 fold in serum and yolk, respectively. Consistent with its potent binding to various Ent derivatives, the Ent-specific egg yolk IgY also inhibited in vitro growth of a representative Escherichia coli strain. Together, this study demonstrated that the novel Ent conjugate vaccine could induce strong, specific, and robust immune response in chickens. The Ent-specific hyperimmune egg yolk IgY has potential for passive immune intervention against Gram-negative infections.

Co-Opting Host Receptors for Targeted Delivery of Bioconjugates-From Drugs to Bugs.

Bioconjugation has allowed scientists to combine multiple functional elements into one biological or biochemical unit. This assembly can result in the production of constructs that are targeted to a specific site or cell type in order to enhance the response to, or activity of, the conjugated moiety. In the case of cancer treatments, selectively targeting chemotherapies to the cells of interest limit harmful side effects and enhance efficacy. Targeting through conjugation is also advantageous in delivering treatments to difficult-to-reach tissues, such as the brain or infections deep in the lung. Bacterial infections can be more selectively treated by conjugating antibiotics to microbe-specific entities; helping to avoid antibiotic resistance across commensal bacterial species. In the case of vaccine development, conjugation is used to enhance efficacy without compromising safety. In this work, we will review the previously mentioned areas in which bioconjugation has created new possibilities and advanced treatments.

Discovery of Semi- and Fully-Synthetic Carbohydrate Vaccines Against Bacterial Infections Using a Medicinal Chemistry Approach.

The glycocalyx, a thick layer of carbohydrates, surrounds the cell wall of most bacterial and parasitic pathogens. Recognition of these unique glycans by the human immune system results in destruction of the invaders. To elicit a protective immune response, polysaccharides either isolated from the bacterial cell surface or conjugated with a carrier protein, for T-cell help, are administered. Conjugate vaccines based on isolated carbohydrates currently protect millions of people against Streptococcus pneumoniae, Haemophilus influenzae type b, and Neisseria meningitides infections. Active pharmaceutical ingredients (APIs) are increasingly discovered by medicinal chemistry and synthetic in origin, rather than isolated from natural sources. Converting vaccines from biologicals to pharmaceuticals requires a fundamental understanding of how the human immune system recognizes carbohydrates and could now be realized. To illustrate the chemistry-based approach to vaccine discovery, I summarize efforts focusing on synthetic glycan-based medicinal chemistry to understand the mammalian antiglycan immune response and define glycan epitopes for novel synthetic glycoconjugate vaccines against Streptococcus pneumoniae, Clostridium difficile, Klebsiella pneumoniae, and other bacteria. The chemical tools described here help us gain fundamental insights into how the human system recognizes carbohydrates and drive the discovery of carbohydrate vaccines.

Estimated impact of the pneumococcal conjugate vaccine on pneumonia mortality in South Africa, 1999 through 2016: An ecological modelling study.

BACKGROUND: Data on the national-level impact of pneumococcal conjugate vaccine (PCV) introduction on mortality are lacking from Africa. PCV was introduced in South Africa in 2009. We estimated the impact of PCV introduction on all-cause pneumonia mortality in South Africa, while controlling for changes in mortality due to other interventions. METHODS AND FINDINGS: We used national death registration data in South Africa from 1999 to 2016 to assess the impact of PCV introduction on all-cause pneumonia mortality in all ages, with the exclusion of infants aged <1 month. We created a composite (synthetic) control using Bayesian variable selection of nondiarrheal, nonpneumonia, and nonpneumococcal deaths to estimate the number of expected all-cause pneumonia deaths in the absence of PCV introduction post 2009. We compared all-cause pneumonia deaths from the death registry to the expected deaths in 2012 to 2016. We also estimated the number of prevented deaths during 2009 to 2016. Of the 9,324,638 deaths reported in South Africa from 1999 to 2016, 12·6% were pneumonia-related. Compared to number of deaths expected, we estimated a 33% (95% credible interval (CrI) 26% to 43%), 23% (95%CrI 17% to 29%), 25% (95%CrI 19% to 32%), and 23% (95%CrI 11% to 32%) reduction in pneumonia mortality in children aged 1 to 11 months, 1 to 4 years, 5 to 7 years, and 8 to 18 years in 2012 to 2016, respectively. In total, an estimated 18,422 (95%CrI 12,388 to 26,978) pneumonia-related deaths were prevented from 2009 to 2016 in children aged <19 years. No declines were estimated observed among adults following PCV introduction. This study was mainly limited by coding errors in original data that could have led to a lower impact estimate, and unmeasured factors could also have confounded estimates. CONCLUSIONS: This study found that the introduction of PCV was associated with substantial reduction in all-cause pneumonia deaths in children aged 1 month to <19 years. The model predicted an effect of PCV in age groups who were eligible for vaccination (1 months to 4 years), and an indirect effect in those too old (8 to 18 years) to be vaccinated. These findings support sustaining pneumococcal vaccination to reduce pneumonia-related mortality in children.

Use of Pneumococcal Conjugate Vaccines to Prevent Acute Otitis Media in Children.

Editor's note: The mission of Cochrane Nursing is to provide an international evidence base for nurses involved in delivering, leading, or researching nursing care. Cochrane Corner provides summaries of recent systematic reviews from the Cochrane Library. For more information, see https://nursing.cochrane.org.

Synthetic protein conjugate vaccines provide protection against Mycobacterium tuberculosis in mice.

The global incidence of tuberculosis remains unacceptably high, with new preventative strategies needed to reduce the burden of disease. We describe here a method for the generation of synthetic self-adjuvanted protein vaccines and demonstrate application in vaccination against Mycobacterium tuberculosis Two vaccine constructs were designed, consisting of full-length ESAT6 protein fused to the TLR2-targeting adjuvants Pam2Cys-SK4 or Pam3Cys-SK4 These were produced by chemical synthesis using a peptide ligation strategy. The synthetic self-adjuvanting vaccines generated powerful local CD4+ T cell responses against ESAT6 and provided significant protection in the lungs from virulent M. tuberculosis aerosol challenge when administered to the pulmonary mucosa of mice. The flexible synthetic platform we describe, which allows incorporation of adjuvants to multiantigenic vaccines, represents a general approach that can be applied to rapidly assess vaccination strategies in preclinical models for a range of diseases, including against novel pandemic pathogens such as SARS-CoV-2.

Immunogenicity and Safety of a Two-Dose Series of a Meningococcal (Groups A, C, W, and Y) Polysaccharide Diphtheria Toxoid Conjugate Vaccine (Men-ACWY-D) in Healthy Japanese Adults.

The quadrivalent meningococcal polysaccharide diphtheria toxoid conjugate vaccine (Men-ACWY-D) has been licensed for use in Japan since 2014. An earlier registration study demonstrated the immunogenicity of a single dose in Japanese adults, wherein the immunogenicity against serogroup C was the lowest. The determination of the potential to increase the serogroup C response with a second dose was, therefore, of interest. This study (NCT02591290) evaluated the safety and immunogenicity of two doses administered 8 weeks apart to 60 healthy Japanese adults aged 20-55 years. Blood samples were collected at 28-35 days after vaccination. Immunogenicity endpoints included seroprotection and seroconversion rates. Safety assessments included systemic adverse events (AEs), non-serious AEs, and serious AEs. Fifty-eight participants (96.7%) completed the study. The seroprotection rates for serogroups A, C, W, and Y before vaccination were 76.8%, 26.8%, 26.8%, and 50.0%, respectively, increasing to 100%, 83.9%, 91.1%, and 96.4% and 100%, 92.9%, 94.6%, and 94.6%, respectively, after two doses. The seroconversion rates for the four serogroups were 100%, 93.8%, 97.1%, and 94.1%, respectively, after the first dose, and 100%, 96.9%, 100%, and 100%, respectively, after the second. The increase between the doses was insignificant, and there were no safety concerns. The two-dose series was well tolerated; however, the clinical benefits of a second dose within 8 weeks seemed to be low.

Vi-specific serological correlates of protection for typhoid fever.

Typhoid Vi vaccines have been shown to be efficacious in children living in endemic regions; however, a widely accepted correlate of protection remains to be established. We applied a systems serology approach to identify Vi-specific serological correlates of protection using samples obtained from participants enrolled in an experimental controlled human infection study. Participants were vaccinated with Vi-tetanus toxoid conjugate (Vi-TT) or unconjugated Vi-polysaccharide (Vi-PS) vaccines and were subsequently challenged with Salmonella Typhi bacteria. Multivariate analyses identified distinct protective signatures for Vi-TT and Vi-PS vaccines in addition to shared features that predicted protection across both groups. Vi IgA quantity and avidity correlated with protection from S. Typhi infection, whereas higher fold increases in Vi IgG responses were associated with reduced disease severity. Targeted antibody-mediated functional responses, particularly neutrophil phagocytosis, were also identified as important components of the protective signature. These humoral markers could be used to evaluate and develop efficacious Vi-conjugate vaccines and assist with accelerating vaccine availability to typhoid-endemic regions.

Safety of pentavalent DTaP-IPV/Hib combination vaccine in post-marketing surveillance in Guangzhou, China, from 2011 to 2017.

BACKGROUND: The DTaP-IPV/Hib combination vaccine can replace the acellular tetanus vaccine, polio vaccine, and the Haemophilus influenzae type B vaccine. Data on the safety of DTaP-IPV/Hib vaccines are required. We aimed to evaluate the safety of the vaccination program. METHODS: Using the National Adverse Events Following Immunization (AEFI) surveillance system (CNAEFIS) in Guangzhou, China, a retrospective study was performed from May 11, 2011, to December 31, 2017. There were 376 cases of adverse events after vaccination with the DTaP IPV/Hib vaccine. The primary analysis indicators were the number of vaccines used, the number of AEFI reports received, and the reporting rate (per 100,000). RESULTS: From May 1, 2011, to December 31, 2017, 516,000 doses of vaccine were inoculated, and 376 cases of adverse reactions were reported; the reporting rate was 72.8 per 100,000 vaccines. There were eight cases of serious AEFIs (1.5 per 100,000), with four cases of thrombocytopenic purpura (0.8 per 100,000); three cases of cyanosis of the lips, stiffness, and flexion of limbs, and convulsions (0.6 per 100,000); and one case of a high fever (0.2 per 100,000). The highest incidence of AEFIs occurred after the fourth dose (n = 207, 55.0%, 40.1 per 100,000), followed by the first dose (n = 81, 21.5%, 15.7 per 100,000), second dose (n = 48, 12.8%, 9.3 per 100,000) and third dose (n = 40, 10.6%, 7.7 per 100,000). The AEFI incidence was higher after injection of the vaccine into the deltoid muscle of the upper arm (n = 276, 73.4%, 53.5 per 100,000) than after injection of the vaccine into the thigh (n = 100, 26.6%, 19.4 per 100,000). There was a significant difference between AEFIs after injection into the deltoid of the upper arm deltoid and the thigh (x2 = 164.8, P < 0.05). CONCLUSIONS: Most of the reported AEFIs after DTaP-IPV/Hib vaccination are not serious. There were four cases of TP in this study; vaccination may be a rare cause of thrombocytopenic purpura.

Sequential Linkage of Carbohydrate Antigens to Mimic Capsular Polysaccharides: Toward Semisynthetic Glycoconjugate Vaccine Candidates against Streptococcus pneumoniae Serotype 14.

Vaccines based on isolated polysaccharides successfully protect humans from bacterial pathogens such as Streptococcus pneumoniae. Because polysaccharide production and isolation can be technically challenging, glycoconjugates containing synthetic antigens are an attractive alternative. Typically, the shortest possible oligosaccharide antigen is preferable as syntheses of longer structures are more difficult and time-consuming. Combining several protective epitopes or polysaccharide repeating units as blocks by bonds other than glycosidic linkages would greatly reduce the synthetic effort if the immunological response to the polysaccharide could be retained. To explore this concept, we bridged the well-understood and immunologically potent RU of S. pneumoniae serotype 14 (ST14) with an aliphatic spacer and conjugated it to the carrier protein CRM197. Mice immunized with the spacer-bridged glycan conjugates produced high levels of specific antibodies after just one or two vaccine doses, while the tetrasaccharide repeating unit alone required three doses. The antibodies recognized specifically ST14 CPS, while no significant antibody levels were raised against the spacer or unrelated CPS. Synthetic vaccines generated antibodies with opsonic activity. Mimicking polysaccharides by coupling repeating unit antigens via an aliphatic spacer may prove useful also for the development of other glycoconjugate vaccine candidates, thereby reducing the synthetic complexity while enhancing a faster immune response.

Conjugation of new DNA vaccine with polyethylenimine induces cellular immune response and tumor regression in neuroblastoma mouse model.

AIM: To estimate immunogenicity and antitumor effect of new DNA vaccine against neuroblastoma using tyrosine hydroxylase as an antigen and linear polyethylenimine (PEI) 20 kDa as a synthetic DNA carrier in syngeneic mouse tumor model. MATERIALS AND METHODS: DNA vaccine was made by cloning the tyrosine hydroxylase minigene fused to the potato virus X coat protein gene into the expression vector. The A/J mice were vaccinated by three intramuscular injections. For immunogenicity study, immune response was estimated by target cells cytotoxicity assay, interferon-gamma production in enzyme-linked immunospot assay and antigen-specific antibodies in 14 days after the final vaccination. Antitumor effect was assessed by measurement of tumor volume and event-free survival rate in mice with engrafted NB41A3 murine neuroblastoma cells following three intramuscular injections of the vaccine: 7 days before, 5 and 10 days after tumor engraftment. The immune response was also assessed on the 30th day after tumor engraftment. RESULTS: The immunogenicity and antitumor effect of the vaccine in the form of aqueous solution of DNA and DNA-PEI conjugate were compared. Splenocytes cytotoxicity was the highest in the group of DNA-PEI vaccines (37.3 ± 6.9% lysis of target cells) compared with the unconjugated DNA vaccine (26.2 ± 4.0%) and placebo control (21.9 ± 3.7%). The production of interferon-gamma in the enzyme-linked immunospot assay was about ten times higher in the DNA-PEI group than in the other groups. The vaccine slowed or prevented the growth of the tumor. Mice vaccinated with the DNA-PEI vaccine had significantly better survival compared to control group (p < 0.0003). CONCLUSIONS: DNA vaccine against tyrosine hydroxylase, administered as a DNA-PEI 20 kDa conjugate, slows down the growth of neuroblastoma cells engrafted to mice.

Globo H-KLH vaccine adagloxad simolenin (OBI-822)/OBI-821 in patients with metastatic breast cancer: phase II randomized, placebo-controlled study.

PURPOSE: This randomized, double-blind, placebo-controlled, parallel-group, phase II trial assessed the efficacy and safety of adagloxad simolenin (OBI-822; a Globo H epitope covalently linked to keyhole limpet hemocyanin (KLH)) with adjuvant OBI-821 in metastatic breast cancer (MBC). METHODS: At 40 sites in Taiwan, USA, Korea, India, and Hong Kong, patients with MBC of any molecular subtype and ≤2 prior progressive disease events with stable/responding disease after the last anticancer regimen were randomized (2:1) to adagloxad simolenin (AS/OBI-821) or placebo, subcutaneously for nine doses with low-dose cyclophosphamide. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival, correlation of clinical outcome with humoral immune response and Globo H expression, and safety. RESULTS: Of 349 patients randomized, 348 received study drug. Patients with the following breast cancer subtypes were included: hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) (70.4%), triple negative (12.9%), and HER2+ (16.7%), similarly distributed between treatment arms. Median PFS was 7.6 months (95% CI: 6.5-10.9) with AS/OBI-821 (n=224) and 9.2 months (95% CI: 7.3-11.3) with placebo (n=124) (HR=0.96; 95% CI: 0.74-1.25; p=0.77), with no difference by breast cancer subtype. AS/OBI-821 recipients with anti-Globo H IgG titer ≥1:160 had significantly longer median PFS (11.1 months (95% CI: 9.3-17.6)) versus those with titers <1:160 (5.5 months (95% CI: 3.7-5.6); HR=0.52; p<0.0001) and placebo recipients (HR=0.71; p=0.03). Anti-KLH immune responses were similar at week 40 between AS/OBI-821 recipients with anti-Globo IgG titer ≥1:160 and those with anti-Globo IgG titer <1:160. The most common adverse events with AS/OBI-821 were grade 1 or 2 injection site reactions (56.7%; placebo, 8.9%) and fever (20.1%; placebo, 6.5%). CONCLUSION: AS/OBI-821 did not improve PFS in patients with previously treated MBC. However, humoral immune response to Globo H correlated with improved PFS in AS/OBI-821 recipients, leading the way to further marker-driven studies. Treatment was well tolerated.NCT01516307.