Albumin nanoparticles loaded with hemin as peroxidase mimics for immunoassay

Contemporary immunoassays commonly used in clinical diagnostics mostly utilize enzymes, such as horseradish peroxidase, for signal generation. Numerous research is dedicated to the development of artificial peroxidase-mimicking catalysts with lower cost, high activity, better operational stability, and tunable properties. Herein we synthesized hemin-loaded bovine serum albumin (BSA) nanoparticles and applied them as catalytic labels (nanozymes) in colorimetric immunoassay of anti-tetanus antibodies. Hemin is a key part of the peroxidase catalytic center, possessing peroxidase like-activity. Albumin nanoparticles were loaded with multiple hemin molecules and decorated with Streptococcal protein G. Resulting nanozymes possessed good colloidal stability and allowed for antibody detection in blood serum. The sensitivity of antibody detection was sufficient for the assessment of post-vaccination immunity.

Widespread circulation of pertussis and poor protection against diphtheria among middle-aged adults in 18 European countries

Reported incidence of pertussis in member states of the European Union (EU) and the European Economic Area (EEA) varies and may not reflect the real situation. In the EU/EEA, vaccine-induced protection against diphtheria and tetanus seems sufficient as few cases are reported even among the adult population who was vaccinated many years ago. Aim of this study was to determine the seroprevalence of pertussis, diphtheria and tetanus antibodies in EU/EEA countries within the age groups of 40-49 and 50-59 years. Eighteen countries collected around 500 samples between 2015 and 2018 (N=10,302 in total) and they were analysed for IgG-specific antibodies against pertussis toxin (PT), diphtheria toxoid (Dt) and tetanus toxin (TT). The proportion of sera with IgG-PT antibody levels ≥100 IU/mL, indicative for recent pertussis infection was comparable for 13/18 countries ranging between 4.0-6.4%. For diphtheria the proportion of sera lacking the protective level (<0.1 IU/mL) varied between 22.8% and 82.0%. For tetanus the protection was sufficient: only very few sera showed unprotective IgG-TT antibody levels. The seroprevalence of pertussis indicates that the circulation of B. pertussis is widespread across EU/EEA. The lack of vaccine-induced seroprotection against diphtheria in EU/EEA in these age groups is of concern and deserves further attention.

Association between season of vaccination and antibody levels against infectious diseases

Vaccination has reduced the disease burden of vaccine-preventable diseases. However, the extent to which seasonal cycles of immunity could influence vaccine-induced immunity is not well understood. A national cross-sectional serosurveillance study performed in the Netherlands (Pienter-2) yielded data to investigate whether season of vaccination was associated with antibody responses induced by DT-IPV (diphtheria, tetanus and poliomyelitis), MMR (measles, mumps and rubella) and meningococcus C (MenC) vaccines in children. In total, 434 children met the inclusion criteria to study DT-IPV immunity, 811 for MMR and 311 for MenC. Differences in log(antibody levels) by season of vaccination were investigated with linear multivariable regression analyses. Seroconversion rates varied according to season of vaccination for rubella (90% of autumn-vaccinated children vs. 99% of winter-vaccinated had concentrations above cut-off levels). Summer-vaccinated boys showed a slower decline of tetanus antibodies (6% per month), in comparison with winter-vaccinated boys. In conclusion, season of vaccination showed little association with immunological protection. However, a number of associations were seen with a P-value of about 0.03; and adding data from a just-completed nationwide serological study might add more power to the current study. Further immunological and longitudinal investigations could help understand the mechanisms of seasonal influence in vaccine-induced responses.

Serum anti-tetanus and measles antibody titres in Ugandan children aged 4 months to 6 years: implications for vaccine programme

To study the antibody response to tetanus toxoid and measles by age following vaccination in children aged 4 months to 6 years in Entebbe, Uganda. Serum samples were obtained from 113 children aged 4–15 months, at the Mother-Child Health Clinic (MCHC), Entebbe Hospital and from 203 of the 206 children aged between 12 and 75 months recruited through the Outpatients Department (OPD). Antibodies to measles were quantified by plaque reduction neutralisation test (PRNT) and with Siemens IgG EIA. VaccZyme IgG EIA was used to quantify anti-tetanus antibodies. Sera from 96 of 113 (85.0%) children attending the MCHC contained Measles PRNT titres below the protective level (120 mIU/ml). Sera from 24 of 203 (11.8%) children attending the OPD contained PRNT titres <120 mIU/ml. There was no detectable decline in anti-measles antibody concentrations between 1 and 6 years. The anti-tetanus antibody titres in all 113 children attending MCHC and in 189 of 203 (93.1%) children attending the OPD were >0.15 IU/ml by EIA, a level considered protective. The overall concentration of anti-tetanus antibody was sixfold higher in children under 12 months compared with the older children, with geometric mean concentrations of 3.15 IU/ml and 0.49 IU/ml, respectively. For each doubling in age between 4 and 64 months, the anti-tetanus antibody concentration declined by 50%. As time since the administration of the third DTP vaccination doubled, anti-tetanus antibody concentration declined by 39%. The low measles antibody prevalence in the children presenting at the MCHC is consistent with the current measles epidemiology in Uganda, where a significant number of measles cases occur in children under 1 year of age and earlier vaccination may be indicated. The consistent fall in anti-tetanus antibody titre over time following vaccination supports the need for further vaccine boosters at age 4–5 years as recommended by the WHO.

Evaluation of the protective level of antibodies to tetanus toxin in adults in Poland

Introduction: The aim of the research was to assess the protective level of antibodies for tetanus toxin in adults in Poland. The obtained research results provide information on how the protective level of anti-tetanus antibodies is formed after the administration of basic doses and booster doses in people of different ages and gender. Material and Methods: A total of 493 serum samples collected from 321 adult individuals, 86 blood donors and 86 pregnant women with ages ranging from 20 to 40 years were investigated. Antibody concentrations were measured with an enzymelinked immunosorbent assay (Tetanus IgG ELISA, IBL International, Germany). Results: The results showed that among 493 individuals examined, only four were not detected with an IBL ELISA antibody for tetanus toxin. The most, as many as 258 people had antibodies at the level of 0.1-1.0 IU / ml, in 220 people these antibodies were detected at 1.0-5.0 IU / ml and only in 11 people at the level above 5.0 IU / ml. What is very important, the percentage of results with a high level of antibodies to the tetanus toxin (>1.0 IU/ml) decreased with the age of the examined patients. Analysis of the results showed that statistically significantly higher levels of antibodies (>1.0 IU/ml) were detected more frequently in men than in women. The percentage of highly positive results (over 1.0 IU/ml) was significantly higher in pregnant women (73.3%) than in the group of all 169 other women examined (24.3%) and higher than in the group of 50 women (40.0%) and 61 men (57.4%) at a similar age of 19-39 years as pregnant women. Conclusions: The results we obtained testify generally to a relatively good level of immunization against tetanus in the adult population in Poland up to 50 years of age. A high percentage of older people, especially after the age of 60, with a low level of vaccine anti-tetanus antibodies indicate the desirability of administering doses of the anti-tetanus vaccine in people in this age group.