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Organophosphate esters (OPEs) are commonly applied as flame retardants and plasticizers. Toxicological studies suggest exposure effects on immune endpoints, raising concerns as infants' OPE exposures are elevated compared to older children and adults due to hand-to-mouth behavior and breastfeeding. Here, we sought to evaluate the immune responsiveness of infants to a neoantigen (e.g., a newly encountered antigen) in the presence of OPE exposures. As a proxy for immune responsiveness, children were given three doses of the Diphtheria, Tetanus, and Pertussis (DTaP) vaccine as recommended, and diphtheria and tetanus antibodies were evaluated in serum samples collected when children were 12 months old (n = 84). Titers were compared, based on maximum sample overlap, to measurements of OPE metabolites in spot urine samples collected before vaccination (age 2 months, n = 73) and at the time of antibody assessment (12 months of age, n = 46). Metabolites of two chlorinated OPEs were significantly associated with diminished antibodies for diphtheria and tetanus. A metabolite of tris (1,3-dichloroisopropyl)phosphate (TDCIPP) measured at 2 months was associated with decreased diphtheria antibodies (-0.07 IU/mL per log

Myristoylated alanine-rich C kinase substrate (MARCKS) is a ubiquitously expressed Protein Kinase C substrate that has emerged as a potential therapeutic target for amelioration of mucin secretion during chronic obstructive pulmonary disease. MARCKS also plays a key role in regulation of neutrophil adhesion, migration and degranulation. Given its biological role in immune cells, we hypothesized that MARCKS may play an integral role in cytokine secretion. MARCKS protein is highly conserved between the dog and human, and importantly, the N-terminal 24 amino acids are virtually identical between species, allowing us to use the well-characterized MANS peptide to inhibit canine MARCKS function through the N-terminus. Using isolated neutrophils, we evaluated the effect of MARCKS inhibition on LPS-induced cytokine production. We found that pre-treatment of canine neutrophils with MANS peptide significantly reduced the secretion of a broad range of LPS-induced cytokines, including IL-8, CXCL1 and TNFα, in comparison to untreated cells or those treated with a scrambled control peptide. This reduction in IL-8 was maintained when MANS was administered 2 hours after LPS-treatment of cells. Reduction in IL-8 secretion was found not to be due to protein retention or cell death. Our observations identify MARCKS protein as a promising therapeutic target in treatment of inflammatory disease, particularly those syndromes attributed to neutrophil influx and inflammatory cytokine production.