Toxicology assessment for six per- and polyfluoroalkyl (PFAS)-free aqueous film forming foam (AFFF) products.

There is an urgent need to understand the toxicity hazards of aqueous film forming foam (AFFF) replacement products to ensure the balance between performance and toxicity hazards and avoid regrettable substitutions during the rapid phasing out of per- and polyfluoroalkyl substance (PFAS)-containing AFFFs. To address this need, we assessed the toxicity of six candidate PFAS-free products via literature review, estimation techniques, and incorporation of testing data from whole products and compared them against one PFAS-containing product. Then, we combined the relative hazards across human occupational exposure (e.g., concentrate, foam, or dilute exposures), human environmental exposure (e.g., training, emergency response, cleanup), and environmental exposure to aquatic, mammalian, and other terrestrial species using an index-based scoring system to quantify potential hazards across these domains. We found that most PFAS-free products in their concentrated form may cause dermal and ocular irritation, and aquatic toxicity may be a concern from direct or repeated environmental releases. Additionally, all PFAS-free AFFF products assessed contain chemicals that are notable as plausible hazards resulting from release uncertainties (e.g., concentration, release volume, release timing), but the PFAS-free AFFF products appear to have a lower likelihood of environmental persistence and bioaccumulation and to have lower oral human health toxicity than the PFAS-containing reference product. Decision makers can use this information alongside cost-benefit, sustainability, or life-cycle analyses to make a data-driven decision for the adoption of PFAS-free AFFF. Integr Environ Assess Manag 2023;19:1609-1618. © 2023 SETAC.

Comparative Toxicity of Seven Aqueous Film-Forming Foam to In Vitro Systems and Mus.

The comparative toxicity of six per- and polyfluoroalkyl substance (PFAS)-free and one PFAS-containing aqueous film-forming foam (AFFF) was evaluated in an outbred mouse species as well as several in vitro assays. The in vivo toxicological profile of PFAS-free AFFFs in short-term, high-concentration exposures is different than that of a PFAS-containing AFFF. The PFAS-containing reference product induced increased liver weights, while the PFAS-free AFFFs were linked to either decreased or unaffected relative liver weights. The in vitro toxicological profile across PFAS-free AFFFs was uniform except in the Microtox® assay, where thresholds were variable and spanned several orders of magnitude. This direct comparison of products through short-term toxicity tests and in vitro screenings represents early data to support evaluation of potential regrettable substitutions when selecting alternative PFAS-free AFFFs. Further work in diverse taxa (e.g., aquatic organisms, terrestrial invertebrates, birds) and mammalian studies capturing sensitive life stages will refine and expand this data set across a range of risk-relevant toxicological endpoints. Environ Toxicol Chem 2023;42:2364-2374. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

An Interrogation of Shared and Unique Copy Number Variants Across Genetically Distinct Zebrafish Strains.

Zebrafish (Danio rerio) are a widely utilized model system for human disorders, but common laboratory strains have distinct behavioral and physiological differences. Accompanying these known strain differences, commonly used "wildtype" zebrafish strains have both shared and unique suites of single nucleotide polymorphisms and copy number variants (CNVs). Despite this, genomic variation is often ignored in study design, and the actual strain used is often not adequately reported. The goal of this study was to assess CNVs across three common laboratory strains of zebrafish-AB, Tubingen (TU), and WIK-and provide these data as a tool for the zebrafish community. Herein we identified 1351 CNV regions within the most recent genome assembly (GRCz11) covering 1.9% of the zebrafish genome (31.7 Mb). CNVs were found across all chromosomes, and 2200 genes (5121 transcripts) lie within ±5 kb of identified CNVs, pointing to likely cis regulatory actions of CNVs on nearby gene neighbors. We have created a Public Session accessible on the UCSC Genome Browser to view CNVs from this study titled "danRer11 zebrafish CNV across strains" as a tool for the zebrafish community.

Baseline mRNA expression differs widely between common laboratory strains of zebrafish.

Common strains of wildtype zebrafish (Danio rerio) have unique genomic features including SNPs and CNV, but strain information often goes unreported in the literature. As a result, the confounding effects of interstrain variation makes repetition of studies in zebrafish challenging. Here we analyze hepatic mRNA expression patterns between three common zebrafish strains (AB, Tuebingen (TU), and WIK) using Agilent 4 × 44 K gene expression microarrays to establish baseline mRNA expression across strains and between sexes. We observed wide variation in sex-specific gene expression within AB and WIK strains (141 genes in AB and 67 genes in WIK), but no significant variation between sexes within TU. After partitioning the dataset into male and female subsets, we detected 421 unique mRNA transcripts with statistically significant differential expression; 269 mRNA transcripts varied between males, 212 mRNA transcripts varied between females, and 59 mRNA transcripts varied across the three strains, regardless of sex. It is not surprising that mRNA expression profiles differ between sexes and strains, but it is imperative to characterize the differences. These results highlight the complexity of variation within zebrafish and underscore the value of this model system as a valid representation of normal variation present in other species, including humans.

Assembly and Analysis of Unmapped Genome Sequence Reads Reveal Novel Sequence and Variation in Dogs.

Dogs are excellent animal models for human disease. They have extensive veterinary histories, pedigrees, and a unique genetic system due to breeding practices. Despite these advantages, one factor limiting their usefulness is the canine genome reference (CGR) which was assembled using a single purebred Boxer. Although a common practice, this results in many high-quality reads remaining unmapped. To address this whole-genome sequence data from three breeds, Border Collie (n = 26), Bearded Collie (n = 7), and Entlebucher Sennenhund (n = 8), were analyzed to identify novel, non-CGR genomic contigs using the previously validated pseudo-de novo assembly pipeline. We identified 256,957 novel contigs and paired-end relationships together with BLAT scores provided 126,555 (49%) high-quality contigs with genomic coordinates containing 4.6 Mb of novel sequence absent from the CGR. These contigs close 12,503 known gaps, including 2.4 Mb containing partially missing sequences for 11.5% of Ensembl, 16.4% of RefSeq and 12.2% of canFam3.1+ CGR annotated genes and 1,748 unmapped contigs containing 2,366 novel gene variants. Examples for six disease-associated genes (SCARF2, RD3, COL9A3, FAM161A, RASGRP1 and DLX6) containing gaps or alternate splice variants missing from the CGR are also presented. These findings from non-reference breeds support the need for improvement of the current Boxer-only CGR to avoid missing important biological information. The inclusion of the missing gene sequences into the CGR will facilitate identification of putative disease mutations across diverse breeds and phenotypes.

Author Correction: Assembly and Analysis of Unmapped Genome Sequence Reads Reveal Novel Sequence and Variation in Dogs.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.

Plasma cell survival in the absence of B cell memory.

Pre-existing serum antibodies play an important role in vaccine-mediated protection against infection but the underlying mechanisms of immune memory are unclear. Clinical studies indicate that antigen-specific antibody responses can be maintained for many years, leading to theories that reactivation/differentiation of memory B cells into plasma cells is required to sustain long-term antibody production. Here, we present a decade-long study in which we demonstrate site-specific survival of bone marrow-derived plasma cells and durable antibody responses to multiple virus and vaccine antigens in rhesus macaques for years after sustained memory B cell depletion. Moreover, BrdU+ cells with plasma cell morphology can be detected for 10 years after vaccination/BrdU administration, indicating that plasma cells may persist for a prolonged period of time in the absence of cell division. On the basis of these results, long-lived plasma cells represent a key cell population responsible for long-term antibody production and serological memory.