Exposure to DDT and Pyrethroid Insecticides and Humoral Response to Vaccines among South African Children from an Area Sprayed for Malaria Control
Bibliographic record
Abstract
Animals studies strongly suggest that exposure to insecticides such as DDT and pyrethroids inhibit immune response to vaccines. However, few human studies have investigated this question and none have done so in communities where insecticides are used to control malaria as part of Indoor Residual Spraying programs. These communities experience high exposure to insecticides and may be particularly susceptible to their toxic effects due to poverty, malnutrition and poor health. Our objective was thus to evaluate whether prenatal exposure to DDT and pyrethroids was associated with reduced immune response to vaccines at age 3.5 years among South African children participating in the Venda Health Examination of Mothers, Babies and their Environment (VHEMBE) birth cohort study. Between August 2012 and December 2013, we enrolled 752 women when they presented for delivery at Tshilidzini hospital in the city of Thohoyandou. We collected urine and blood samples at delivery for the measurement of pyrethroid metabolites and DDT via gas chromatography-mass spectrometry, respectively. At age 3.5 years, we collected child blood samples and measured measles, tetanus and Haemophilus influenzae b (Hib)-specific 1) antibody titers via enzyme-linked immunosorbent assay (ELISA) and polyfunctional transitional, central and effector memory CD4+ T cells. Initial analyses suggest that each 10-fold increase in maternal DDT serum concentration is associated with a 75% (95%CI=-15, 306) increased risk of measles antibody seronegativity and a 5.2-fold (95%CI=1.5, 17.5) increase in the risk of detecting no transitional memory CD4+ T cells expressing TNF-α and IFN-γ. Pyrethroid metabolites cis-DBCA and 3-PBA were primarily associated with reduced measles- and tetanus-specific central memory CD4+ T cells expressing TNF-α and IL-2. Overall, results suggest that exposure to DDT and pyrethroids may inhibit immune response to vaccines among South African children.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".