Absence of a pancreatic microbiome in intraductal papillary mucinous neoplasm

OBJECTIVE

This study aims to validate the existence of a microbiome within intraductal papillary mucinous neoplasm (IPMN) that can be differentiated from the taxonomically diverse DNA background of next-generation sequencing procedures.

DESIGN

We generated 16S rRNA amplicon sequencing data to analyse 338 cyst fluid samples from 190 patients and 19 negative controls, the latter collected directly from sterile syringes in the operating room. A subset of samples (n=20) and blanks (n=5) were spiked with known concentrations of bacterial cells alien to the human microbiome to infer absolute abundances of microbial traces. All cyst fluid samples were obtained intraoperatively and included IPMNs with various degrees of dysplasia as well as other cystic neoplasms. Follow-up culturing experiments were conducted to assess bacterial growth for microbiologically significant signals.

RESULTS

Microbiome signatures of cyst fluid samples were inseparable from those of negative controls, with no difference in taxonomic diversity, and microbial community composition. In a patient subgroup that had recently undergone invasive procedures, a bacterial signal was evident. This outlier signal was not characterised by higher taxonomic diversity but by an increased dominance index of a gut-associated microbe, leading to lower taxonomic evenness compared with the background signal.

CONCLUSION

The 'microbiome' of IPMNs and other pancreatic cystic neoplasms does not deviate from the background signature of negative controls, supporting the concept of a sterile environment. Outlier signals may appear in a small fraction of patients following recent invasive endoscopic procedures. No associations between microbial patterns and clinical or cyst parameters were apparent.

Abstract 876: Sequencing a new broadly-consented tumor/normal cell line for a Genome in a Bottle Benchmark

Here, we describe analyses towards the first tumor/normal benchmark from the Genome in a Bottle (GIAB) consortium using new cell lines from a broadly-consented pancreatic ductal adenocarcinoma patient. This effort builds on the widely-used germline variant benchmarks for seven normal DNA reference materials. GIAB benchmarks are designed to reliably identify false positive and false negative variant calls, and are formed by combining multiple sequencing technologies and variant callers. To combine technologies and variant callers, we first understand their strengths and weaknesses for different variant types and repetitive regions. In this initial work on the new tumor/normal cell line, we have analyzed sequencing from HiC for copy number and structural variant analysis and 100to150x PCR-free Illumina WGS from normal and tumor cells for small variants. Preliminary HiC results identified substantial aneuploidy common in pancreatic tumors, with ~15 large inversions and translocations and 16 chromosomes with extensive loss of heterozygosity due to missing >30% of one copy. The tumor contains the common G12V mutation in KRAS, and interestingly the ~2Mbp region containing this mutation is likely triplicated. About 300 (76% of) SNVs and 10,000 (69% of) small indels agree between mutect2 and strelka2 with default filtering. After excluding difficult regions, 95% of SNVs and 94% of small indels agree, with remaining disagreements caused by systematic sequencing errors, alignment errors, low frequency, and proximity to germline variants. Examining discordant SNVs indifficult regions, most are erroneous somatic variants inregions with loss of heterozygosity that also have mapping errors due to segmental duplications, sequences missing from GRCh38, and/or tandem repeats. After excluding difficult regions, we also found that somatic SNVs fell in 4 primary classes: ~5100 in most cells in diploid regions, ~2100 in most cells in haploid regions, ~760 in only some cells in diploid regions, and ~450 in only some cells in haploid regions. GIAB plans to perform PacBioHiFi and ultra long ONT sequencing to generate phased assemblies for the normal and tumor, and is forming an open working group to develop the first authoritative benchmarks from publicly available, broadly-consented tumor-normal cell lines.

Citation Format: Gail Rosen, Justin Wagner, Andrew Liss, Justin Zook. Sequencing a new broadly-consented tumor/normal cell line for a Genome in a Bottle Benchmark [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 876.

Phase Ib study testing neoadjuvant transforming growth factor (TGF)-β antibody, NIS793, plus 5-fluorouracil, irinotecan, and oxaliplatin chemotherapy (FOLFIRINOX) in patients (pts) with borderline resectable (BR)/locally advanced (LA) pancreatic ductal adenocarcinoma (PDAC)

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Background: Overcoming resistance to chemotherapy and immune checkpoint inhibitors remains an unmet need for PDAC. In this context, TGF-β plays a key role in PDAC by promoting the activation of fibroblasts and extracellular matrix deposition, facilitating epithelial-to-mesenchymal transition, immune evasion, and resistance to chemotherapy. Combination of FOLFIRINOX with losartan, an indirect TGF-β inhibitor with antifibrotic properties, has shown an increased R0 resection rate in pts with BR/LA PDAC, providing the rationale to explore the combination of other TGF-β targeting agents with FOLFIRINOX in the neoadjuvant setting (PMID: 34884782; PMID: 31145418). NIS793 is a first-in-class monoclonal antibody that directly binds TGF-β and reduces intratumoral fibrosis in preclinical models (PMID: 33298926). NIS793 also has an acceptable safety profile and preliminary clinical activity. This study investigates whether NIS793 modulation of the tumor fibrotic network improves clinical outcomes of FOLFIRINOX neoadjuvant therapy in BR/LA PDAC. Our aim is to demonstrate how TGF-β inhibition and stroma remodeling contribute to clinical outcomes. Methods: This is a single institution, open label, 2-part, 2-arm, non-comparator, Phase Ib study (NCT05417386) of FOLFIRINOX + NIS793 as neoadjuvant therapy for pts with untreated BR/LA PDAC. Eligible pts are adults with measurable disease, adequate organ and bone marrow function, and ECOG PS ≤1. In Part 1 (safety run-in), 6-18 pts with histologically confirmed untreated metastatic PDAC receive FOLFIRINOX + NIS793 at different dose levels. Dose escalation is primarily guided by the number of dose-limiting toxicities. Primary objectives are assessing safety, defining the recommended Phase II dose (RP2D), and providing initial evidence of clinical benefit of the combination. In Part 2, pts with untreated BR/LA PDAC are randomized 4:1 and stratified by BR vs LA. Pts in Arm 1 (n=5) receive 8 cycles of FOLFIRINOX followed by chemoradiation therapy (CRT) and surgery. Pts in Arm 2 (n=23) receive 8 cycles of FOLFIRINOX + NIS793 at RP2D followed by CRT + NIS793, surgery, and 12 cycles of adjuvant NIS793. The primary endpoint is R0 resection rate. Secondary endpoints are disease-free survival, progression-free survival, overall survival, and pathologic complete response. The effect of neoadjuvant therapy will be assessed by ferumoxytol-MRI, circulating cell-free DNA dynamics analysis, single-cell RNA sequencing, immunohistochemistry, and digital spatial analysis. Together, these correlative analyses may enable development of a mechanistic model for TGF-β inhibition in PDAC. This study is ongoing. The first pt was treated on Aug 2, 2022. Clinical trial information: NCT05417386 .

Spatially defined enrichment of a neuronal-like malignant phenotype in pancreatic cancer after neoadjuvant treatment

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Background: Pancreatic ductal adenocarcinoma (PDAC) is highly lethal and resistance to chemotherapy and radiotherapy is a major obstacle to improving clinical outcomes. Hence, there is an urgent need to elucidate the gene expression programs, spatial context, and interactions among different cell types in residual disease after neoadjuvant treatment. Methods: We optimized and applied single-nucleus RNA-seq (snRNA-seq) to 43 frozen primary PDAC tumors. Eighteen were treatment-naïve, 14 received FOLFIRINOX followed by radiotherapy with 5-FU or capecitabine (CRT), and 5 were subjected to CRT combined with losartan on protocol (CRTL). We performed unsupervised clustering of single nucleus profiles and then annotated and quantified cell subsets. Malignant and fibroblast gene expression programs were identified by consensus non-negative matrix factorization (cNMF). We mapped our cell type signatures and expression programs onto the tumor architecture using whole-transcriptome digital spatial profiling (DSP) to uncover distinct multicellular spatial neighborhoods and intercellular interactions that compose PDAC and are remodeled by neoadjuvant treatment. Results: Consistent with treatment effect, the proportion of malignant cells was significantly lower in tumors treated with neoadjuvant therapy. Within the immune compartment, CRTL was associated with a higher fraction of CD8+ T cells and Tregs compared to untreated and CRT tumors. Differential expression analysis of CD8+ T cells revealed greater effector function (e.g., IL2, CCL4, CCL5) and reduced quiescence/dysfunction markers (e.g., TIGIT, TCF7, KLF2, LEF1) associated with CRTL. We discovered expression programs across malignant and fibroblast profiles that formed a refined molecular taxonomy, including a novel neuronal-like malignant program enriched in the neoadjuvant groups and associated with the worst prognosis in independent cohorts. Ex vivo treatment of organoids derived from an untreated PDAC with FOLFIRINOX chemotherapy and radiotherapy recapitulated enrichment of the neuronal-like program. Whole-transcriptome DSP revealed three distinct multicellular neighborhoods: classical, squamoid-basaloid, and treatment-enriched. The observed enrichment in post-treatment residual disease of multiple spatially-defined receptor-ligand interactions and a neighborhood featuring colocalization of the neuronal-like malignant program, neurotropic CAF program, and CD8+ T cells may open new opportunities for therapeutic targeting in PDAC. Conclusions: Our work provides a high-resolution molecular framework for understanding the inter- and intra-tumoral heterogeneity of pancreatic cancer, spatial organization into discrete multicellular communities, and treatment-associated reprogramming as a blueprint for exploring novel therapeutic strategies tailored to residual disease.

Influence of Klebsiella pneumoniae and quinolone treatment on prognosis in patients with pancreatic cancer

BACKGROUND

An increasing body of evidence suggests that microbiota may promote progression of pancreatic ductal adenocarcinoma (PDAC). It was hypothesized that gammaproteobacteria (such as Klebsiella pneumoniae) influence survival in PDAC, and that quinolone treatment may attenuate this effect.

METHODS

This was a retrospective study of patients from the Massachusetts General Hospital (USA) and Ludwig-Maximilians-University (Germany) who underwent preoperative treatment and pancreatoduodenectomy for locally advanced or borderline resectable PDAC between January 2007 and December 2017, and for whom a bile culture was available. Associations between tumour characteristics, survival data, antibiotic use and results of intraoperative bile cultures were investigated. Survival was analysed using Kaplan-Meier curves and Cox regression analysis.

RESULTS

Analysis of a total of 211 patients revealed that an increasing number of pathogen species found in intraoperative bile cultures was associated with a decrease in progression-free survival (PFS) (-1·9 (95 per cent c.i. -3·3 to -0·5) months per species; P = 0·009). Adjuvant treatment with gemcitabine improved PFS in patients who were negative for K. pneumoniae (26·2 versus 15·3 months; P = 0·039), but not in those who tested positive (19·5 versus 13·2 months; P = 0·137). Quinolone treatment was associated with improved median overall survival (OS) independent of K. pneumoniae status (48·8 versus 26·2 months; P = 0·006) and among those who tested positive for K. pneumoniae (median not reached versus 18·8 months; P = 0·028). Patients with quinolone-resistant K. pneumoniae had shorter PFS than those with quinolone-sensitive K. pneumoniae (9·1 versus 18·8 months; P = 0·001).

CONCLUSION

K. pneumoniae may promote chemoresistance to adjuvant gemcitabine, and quinolone treatment is associated with improved survival.

Single-nucleus RNA-seq of frozen archival primary pancreatic ductal adenocarcinoma uncovers multi-compartment intratumoral heterogeneity associated with neoadjuvant treatment

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Background: Pancreatic ductal adenocarcinoma (PDAC) remains a treatment-refractory disease and existing molecular subtypes do not inform clinical decisions. Previously identified bulk transcriptomic subtypes of PDAC were often unintentionally driven by “contaminating” stroma. RNA extraction from pancreatic tissue is difficult and prior single-cell RNA-seq efforts have been limited by suboptimal dissociation/RNA quality and poor performance in the setting of neoadjuvant treatment. We developed a robust single-nucleus RNA-seq (sNuc-seq) technique compatible with frozen archival PDAC specimens. Methods: Single nuclei suspensions were extracted from frozen primary PDAC specimens (n = 27) derived from patients with (borderline)-resectable PDAC who underwent surgical resection with or without neoadjuvant chemoradiotherapy (CRT). Approximately 170,000 nuclei were processed with the 10x Genomics Single Cell 3’ v3 pipeline and gene expression libraries were sequenced (Illumina HiSeq X). Results: Distinct nuclei clusters with gene expression profiles/inferred copy number variation analysis consistent with neoplastic, acinar, ductal, fibroblast, endothelial, endocrine, lymphocyte, and myeloid populations were identified with proportions similar to corresponding multiplexed ion beam imaging. Non-negative matrix factorization revealed intra-tumoral heterogeneity shared across patients. Neoplastic cells featured eight distinct transcriptional topics characterized by developmental (epithelial, mesenchymal, endoderm progenitor, neural progenitor) and environmental (anabolic, catabolic, cycling, hypoxic) programs. CAFs exhibited four different transcriptional topics (activated/desmoplastic, myofibroblast, neurogenic, osteochondral). Differential gene expression and gene set enrichment analyses demonstrated that CRT was associated with an enrichment in myogenic programs in CAFs, activation pathways in immune cells, and type I/II interferons in malignant cells. CRT was also associated with a depletion in developmental programs within malignant cells. Conclusions: We uncovered significant intratumoral heterogeneity and treatment-associated differences in the malignant, fibroblast, and immune compartments of PDAC using sNuc-seq. Deconvolution of clinically-annotated bulk RNA-seq cohorts and characterization of intercellular interactions with receptor-ligand analysis and spatial transcriptomics are ongoing.

Image-Based Profiling of Patient-Derived Pancreatic Tumor-Stromal Cell Interactions Within a Micropatterned Tumor Model

Pancreatic cancer is one of the most aggressive cancers with a 5-year patient survival rate of 8.2% and limited availability of therapeutic agents to target metastatic disease. Pancreatic cancer is characterized by a dense stromal cell population with unknown contribution to the progression or suppression of tumor growth. In this study, we describe a microengineered tumor stromal assay of patient-derived pancreatic cancer cells to study the heterotypic interactions of patient pancreatic cancer cells with different types of stromal fibroblasts under basal and drug-treated conditions. The population dynamics of tumor cells in terms of migration and viability were visualized as a functional end point. Coculture with cancer-associated fibroblasts increased the migration of cancer cells when compared to dermal fibroblasts. Finally, we imaged the response of a bromodomain and extraterminal inhibitor on the viability of pancreatic cancer clusters surrounding by stroma in microengineered tumor stromal assay. We visualized a codynamic reduction in both cancer and stromal cells with bromodomain and extraterminal treatment compared to the dimethyl sulfoxide-treated group. This study demonstrates the ability to engineer tumor–stromal assays with patient-derived cells, study the role of diverse types of stromal cells on cancer progression, and precisely visualize a coculture during the screening of therapeutic compounds.

Professional competencies and work-related support in relation to periodontal therapy and work satisfaction: A questionnaire study among Swedish Dental Hygienists

OBJECTIVES

To analyse dental hygienists' (DHs) views on professional competencies and behavioural interventions in the treatment of periodontitis patients, perceived work-related support and work satisfaction.

METHODS

A Web-based questionnaire was distributed to all DHs employed at the public dental service in the county of Västra Götaland, Sweden. 302 (83%) responded to the questionnaire; 291 of these DHs stated that they on regular basis treated periodontitis patients and thus constituted the sample for analyses. Based on initial correlation and bivariate analyses of the questionnaire data, multiple logistic regression models were formulated to estimate perceived competencies to treat patients with periodontitis and work satisfaction.

RESULTS

The multiple analyses revealed that DHs who worked with specific methods for behavioural intervention, like motivational interviewing, were more likely to rate themselves as "definitely possessing the competencies required to treat patients with periodontitis" (OR 4.0). Likewise, this group of DHs did not consider it more difficult to charge their patients the financial costs for such a behavioural intervention than for scaling therapy (OR 3.1). The perception that one's professional competencies were utilized well in daily practice was associated with high work satisfaction (OR 4.1). More years in the profession (OR 1.03) and a good support by colleagues (OR 1.9) had also a positive impact on work satisfaction.

CONCLUSIONS

Dental hygienists' considered that competencies in the treatment of periodontitis patients were related to the practice of behavioural interventions as part of therapy. A stimulating and supportive work environment, with opportunities for professional development, is important for work satisfaction.

Abstract 5538A: Cell size-specific intracellular delivery

Among the many methods of intracellular delivery, cell size-selective delivery is particularly applicable to cancer research and therapeutics where tumor cells tend to be larger than blood cells and selective manipulation of a single cell-type while minimally affecting the other cells in a heterogeneous mixture is important. In this study, cell size-selective delivery is achieved using a novel microfluidic device with 75 parallel channels through which cells are pushed under nitrogen pressure. The cells undergo deformation as they transit through the channels, which results in temporary disruption of the cell membrane to facilitate delivery of material into the cytoplasm. For each cell size, there is a specific channel width for which optimal cell viability and fluorophore delivery is achieved, with smaller cells requiring narrower channels. When two cells of different sizes are mixed in solution, the channel width for optimal cell viability and fluorophore delivery for each cell type remains the same, and larger cells can achieve fluorophore delivery at a significantly higher percentage than smaller cells at the former's optimal channel width. One possible application for this technology is tagging circulating tumor cells, and we have been able to selectively deliver fluorophores into tumor cells when spiked into whole human blood with 91% specificity. We were also able to isolate pancreatic tumors cells from a patient's blood sample that matched the genotype of the patient's primary pancreatic tumor. Intracellular delivery of materials has become increasingly important as we delve deeper into understanding cellular processes and developing targeted therapies, and with this device, selective delivery can be achieved in a vector-free environment and without dependence on cell-surface receptors.

Citation Format: May Tun Saung, Armon Sharei, Viktor Adalsteinsson, Andrew Liss, Nahyun Cho, Tushar Kamath, Camilo Ruiz, Jesse Kirkpatrick, Robert Langer, Christopher Love, Klavs Jensen. Cell size-specific intracellular delivery. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5538A. doi:10.1158/1538-7445.AM2015-5538A

The chicken RelB transcription factor has transactivation sequences and a tissue-specific expression pattern that are distinct from mammalian RelB

Rel/NF-kappaB proteins are eukaryotic transcription factors that control the expression of genes involved in a large variety of cellular processes. Rel proteins share a highly conserved DNA-binding/dimerization domain called the Rel Homology (RH) domain. We have constructed and characterized a composite cDNA encoding most of the chicken RelB transcription factor. The predicted chicken RelB protein has a high degree of sequence similarity to other vertebrate RelB proteins within the RH domain, but is much less conserved outside this domain. Chicken RelB does not bind DNA as a homodimer, but forms DNA-binding heterodimers with NF-kappaB p50 or p52. Overexpressed chicken RelB localizes to the nucleus in chicken embryo fibroblasts, and the nonconserved C-terminal sequences of chicken RelB contain a transactivation domain that functions in chicken and mouse fibroblasts. Thus, chicken RelB has functional properties similar to other vertebrate RelB proteins. However, Western blotting of diverse chicken tissues indicates that chicken RelB is more widely expressed than mammalian RelB.

One manufacturer's approach to using nucleic acid testing for enhanced plasma-product safety

Source plasma must contain the lowest possible pathogen bioburden so as to minimize the stress placed on subsequent viral reduction steps. Differences exist between European and US criteria for developing assays used to detect these viral pathogens. The approach used by 1 plasma-product manufacturer is described here. By adding polymerase chain reaction (PCR) detection techniques for various viral pathogens (including human immunodeficiency virus-1, hepatitis C virus, and hepatitis B virus) to the plasma screening process, this manufacturer maximizes the use of cutting-edge technology for plasma product safety while satisfying both European and US criteria and requirements for this process. The protocol begins with maxipool testing and eventually identifies any specific donor plasma that might be positive in the contributing minipools. The goal is to identify reactive donors for possible periodic monitoring and to use only nonreactive donations to continue producing a particular plasma product. Controversy surrounding the use of PCR to screen emerging organisms of questionable pathogenicity or known organisms that are of minimal pathogenicity for most of the population is also discussed, and possible solutions to this debate are provided.

Primary sensory neuron survival following targeted administration of nerve growth factor to an injured nerve

Nerve injuries induce neurochemical changes within primary sensory neurons, including expression of neuropeptides, and a loss of a substantial proportion of the neurons may possibly be caused by a lack of neurotrophic support. In the present study the role of nerve growth factor (NGF) in preventing these changes was investigated in monkeys by giving NGF peripherally through a fibronectin (Fn) conduit. A sensory nerve (superficial radial) was transected and a gap of 5 mm was bridged with either autologous sural nerve graft (SNG), Fn, or Fn impregnated with NGF (Fn-NGF). After four months the dorsal root ganglia, that received the cutaneous afferents of the nerve, were removed and analysed by quantitative immunohistochemistry using antibodies to calcitonin gene related polypeptide (CGRP) and substance P. The percentage of immunostained cells was taken as an indication of neuronal survival. The results showed that SNG and Fn-NGF reduced the loss of CGRP positive sensory neurons compared with Fn alone. For substance P-positive neurons the differences were small with only a tendency towards reduction of neuronal death after NGF had been given, suggesting that NGF might act preferentially on a subpopulation of CGRP immunoreactive sensory neurons that do not coexist with substance P.

Enzymological features of aromatic amino acid biosynthesis reflect the phylogeny of mycoplasmas

Acholeplasma laidlawii possesses a biochemical pathway for tyrosine and phenylalanine biosynthesis, while Mycoplasma iowae and Mycoplasma gallinarum do not. The detection of 7-phospho-2-dehydro-3-deoxy-D-arabino-heptonate (DAHP) synthase (EC 4.1.2.15), dehydro-shikimate reductase (EC 1.1.1.25) and 3-enol-pyruvoylshikimate-5-phosphate synthase (EC 2.5.1.19) activities in cell-free extracts established the presence in A. laidlawii of a functional shikimate pathway. L-Phenylalanine synthesis occurs solely through the phenylpyruvate route via prephenate dehydratase (EC 4.2.1.51), no arogenate dehydratase activity being found. Although arogenate dehydrogenase was detected, L-tyrosine synthesis appears to occur mainly through the 4-hydroxyphenylpyruvate route, via prephenate dehydrogenase (EC 1.3.1.12), which utilized NAD+ as a preferred coenzyme substrate. L-Tyrosine was found to be the key regulatory molecule governing aromatic biosynthesis. DAHP synthase was feedback inhibited by L-tyrosine, but not by L-phenylalanine or L-tryptophan; L-tyrosine was a potent feedback inhibitor of prephenate dehydrogenase and an allosteric activator of prephenate dehydratase. Chorismate mutase (EC 5.4.99.5) was sensitive to product inhibition by prephenate. Prephenate dehydratase was feedback inhibited by L-phenylalanine. It was also activated by hydrophobic amino acids (L-valine, L-isoleucine and L-methionine), similar to results previously found in a number of other genera that share the Gram-positive line of phylogenetic descent. Aromatic-pathway-encoded cistrons present in saprophytic large-genome mycoplasmas may have been eliminated in the parasitic small-genome mycoplasmas.

Cytotoxic and cytolytic activity of nonadecafluoro-n-decanoic acid on Acholeplasma laidlawii

We studied the interactions between the perfluorinated fatty acid nonadecafluoro-n-decanoic acid (NDFDA) and the cell wall-less procaryote Acholeplasma laidlawii, which were cultured in an identical medium base but with different serum supplements. When grown in mycoplasma media supplemented with PPLO serum fraction (Difco Laboratories, Detroit, Mich.), A. laidlawii was rapidly killed by low concentrations of toxicant (less than 1.0 mM). At higher concentrations (greater than 10 mM), NDFDA treatment appeared to lyse cells. A. laidlawii cells grown in horse serum-supplemented mycoplasma media were both killed and lysed at the same NDFDA concentration (greater than 10 mM). These data suggest that this perfluorinated fatty acid can be cytotoxic and cytolytic to mycoplasmas. Changes in active concentrations occurred in parallel with changes in growth medium serum supplementation, which is known to alter mycoplasma membrane composition. We propose that NDFDA interacts with the membranes of A. laidlawii cells, resulting in cell death or cell lysis or both.

Isolation of a virus from Mycoplasma pulmonis

A virus designated mycoplasma virus P1 has been isolated from Mycoplasma pulmonis. The virus infects M. pulmonis strain UAB 6510, and a plaque-forming unit assay has been developed. P1 has a tailed, polyhedral morphology with a head diameter of about 28 nm. Nucleic acid isolated from crude preparations of P1 virus contains double-stranded RNA, suggesting that P1 may be the first example of an RNA-containing mycoplasma virus.

Perfluorinated fatty acids alter merocyanine 540 dye binding to plasma membranes

We have evaluated the effect of the perfluorinated fatty acids pentadecafluoro-n-octanoic acid (PFOA) and nonadecafluoro-n-decanoic acid (NDFDA) on the ability of a human B-lymphoblastoid cell line to bind the lipid-binding, membrane-impermeant, fluorescent dye merocyanine 540 (MC540). Subtoxic concentrations of perfluorinated fatty acids (0.9 mM PFOA; 0.5 mM NDFDA) greatly diminish binding of MC540 by normal plasma membranes, as determined by fluorescence flow cytometry. When perfluorinated fatty acids are added to cells at toxic or lethal concentrations (1.2 mM PFOA; 0.75 mM NDFDA), MC540 binding increases dramatically, with entrance of dye to internal membrane domains. Neither perfluorinated fatty acid molecule reduces the ability of surface immunoglobulin to migrate laterally and cap on cells. Our data suggest that perfluorinated fatty acids either interact directly with lipid binding sites for MC540, and thereby inhibit dye intercalation, or alter membrane lipid architecture and lipid packing to diminish MC540 binding. Both possibilities support a direct, physical, membrane-altering mechanism for perfluorinated fatty acid toxicity on mammalian cells.

Toxicity of perfluorinated fatty acids for human and murine B cell lines

The toxicity of two perfluorinated fatty acids, penta decafluoro-n-octanoic acid (PFOA) and nonadecafluoro-n-decanoic acid (NDFDA), on three mammalian B cell lines was evaluated. Cells were exposed to the perfluorinated molecules for either 24 or 48 hr under a variety of culture conditions. Immunoglobulin secretion and surface membrane expression were unaffected by both PFOA and NDFDA at sublethal concentrations. Lethal effects of PFOA and NDFDA are diminished by either lowering culture temperature (37 to 20 degrees C) or including fetal bovine serum or human serum albumin in media. At lethal concentrations, both PFOA and NDFDA possess detergent activity since they can release IgM in soluble form from a cell line that does not secrete immunoglobulins, and brief exposure (15 min) to 1-2 mM of both perfluorinated fatty acids results in solubilization of F4 cells equivalent to the anionic detergent deoxycholic acid. Our data suggest that at subtoxic concentrations, neither PFOA nor NDFDA alters expression or secretion of a differentiated gene product (IgM). At lethal levels, both chemicals cause increased solubilization of proteins from lymphoblastoid cell lines.

Acholeplasma laidlawii cells acutely and chronically infected with group 1 acholeplasmavirus

Interactions between group 1 acholeplasmaviruses and their host cells were studied. Acutely infected, chronically infected and uninfected cultures of Acholeplasma laidlawii strain JA1 were compared by their growth in broth and on agar, by the sensitivities of the uninfected and chronically infected cells to representatives of each of the three groups of acholeplasmaviruses, and by their SDS-PAGE polypeptide profiles. Acutely infected cells resembled uninfected cells by these criteria, except for the fact that progeny virus was being released. Two types of chronically infected cells were found:rapid growers (the same doubling time as uninfected cells) and slow growers. The latter resembled uninfected cells, except for their slower growth and low-level release of virus, and the former was resistant to group 1 viruses and had a unique polypeptide profile. These biological characterizations help to establish the non-lytic, non-cytocidal cycle of the group 1 acholeplasmaviruses.

Acholeplasma laidlawii retains sensitivity to exogenous virus while releasing endogenous, mitomycin C induced, virus. Brief report

Three of five Acholeplasma laidlawii strains were found to carry Mitomycin C inducible acholeplasmaviruses. These virus hosts were capable of propagating (1) virus homologous to the one it carried, and (2) exogenous virus while releasing induced endogenous virus.

Demonstration by computed tomography of delayed thyroid metastasis

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Colonial opacity variation in Mycoplasma pulmonis

Colonial size and opacity variation were observed in four independently isolated strains of the murine pathogen Mycoplasma pulmonis. Selecting colonial opacity variants of similar size, we identified opaque and transparent stable variants. Opaque colony-derived broth cultures shed transparent colonies at a rate of about 1.2 X 10(-8) per CFU per generation. The reverse conversion was about two orders of magnitude less frequent. Appearance of opacity and plating efficiency of each pure culture were altered by changing the serum source used to supplement the growth medium. Horse or sheep serum was most efficient at accentuating visualization of opacity differences. Fetal bovine serum was least efficient. In two M. pulmonis strains, each opacity variant showed a distinctive polypeptide profile, as displayed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the same strains, distinctive intrastrain differences were found by agarose gel electrophoresis to display the DNA fragments produced after digestion by several endonucleases. Each pure culture variant retained these differences in DNA even when grown in a medium supplemented with a serum which did not accentuate visualization of the opacity phenotype. Characterization of variants in 30 other M. pulmonis strains is in progress.

Characterization of the enveloped plasmavirus MVL2 after propagation on three Acholeplasma laidlawii hosts

Plasmavirus MVL2 was propagated on three Acholeplasma laidlawii strains, JA1, S2, or BC1-13. Previously reported host-controlled modification (HCM) of MVL2, as reflected by changes in plating efficiency, was observed. Adsorption rates and one-step growth curves varied according to host used. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the three MVL2 populations revealed differences in polypeptide profiles.

Spiroplasmal viruses: group 1 characteristics

Virus-like particles of three morphologic groups have been detected by electron microscopy in 90% of spiroplasma strains. In this study, virus-like particles of group 1 (SpV1)--unenveloped rods 230-280 nm by 10-15 nm--were found in 575 of spiroplasmas. SpV1 occurred spontaneously in large numbers in cultures of strains B (corn stunt), G1 (tulip tree flower), BC3 (honeybee), and KC3 (honeybee), respectively; the viruses were isolated and assayed as plaque-forming units, with several of the same strains used as indicators. No virus plaqued on its strain of origin, and all except one (SpV1/BC3) plaqued best on strain BC3. Host range and yields of progeny virus differed. All isolates were identical in morphology, size, and buoyant densities; contained DNA; formed turbid 1.5 to 5.0-mm plaques; produced nonlytic infections and similar one-step growth curves; were inactivated by a single antiserum; had similar kinetics of adsorption and heat inactivation; and demonstrated similar patterns of resistance and sensitivity to a variety of physical and chemical agents, as well as an inability to infect resistant host mutants. SPV1 isolates from diverse host strains apparently share many physicochemical and biological properties, but are not identical in all biological respects.

Release of a group 1 mycoplasma virus from Acholeplasma laidlawii after treatment with mitomycin C

A rod-shaped group 1 mycoplasma virus was released from Acholeplasma laidlawii strain JA2 after treatment with 2.5 mug of mitomycin C per ml. Similar treatment of A. laidlawii strain Bju failed to stimulate release of any PFU.

Membrane composition and virus susceptibility of Acholeplasma laidlawii

The membrane composition of 11 strains of Acholeplasma laidlawii, including three strains persistently infected with mycoplasmaviruses MVL51, MVL2, and MVL3, was studied and correlated with mycoplasmavirus sensitivity. Membranes of the strains had similiar sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns, and all strains were inhibited by an antiserum produced against membranes from one of the strains. The amounts of integral membrane proteins solubilized by the nonionic detergent Tween 20 differed considerably. Therefore, characteristic crossed immunoelectrophoresis patterns were obtained for each strain. Strains persistently infected with MVL2 and MVL3 were notably different from the noninfected host. The ability to propagate any of the viruses was not correlated with sodium dodecyl sulfate-polyacrylamide gel electrophoresis or crossed immunoelectrophoresis patterns. The persistently infected strains had a characteristic lipid composition. MVL51-resistant strains, including a resistant clone selected from a sensitive strain, were characterized by a large monoglucosyldiglyceride/diglucosyldiglyceride ratio and trace amounts of diphosphatidylglyceol (as opposed to the sensitive strains). Differences in lipid composition in A. laidlawii seem to affect the relationship between cells and viruses.

Intracellular replication of mycoplasmavirus MVL51

The intracellular replication of MVL51, a group L1 mycoplasmavirus, was investigated. The single-stranded parental DNA was found to enter the cell and become converted to double-stranded DNA. This replicated to yield additional double-stranded DNA molecules. The parental viral DNA was found to leave the replication complex and become associated with large molecular weight DNA not involved with viral replication. Progeny viral DNA formed from the double-stranded DNA and an intracellular accumulation of virus chromosome size DNA was observed. The interpretation of this data and a suggested model for the viral replication are discussed and compared to viral DNA replication models for other single-stranded DNA viruses.

Transfection mediated by Mycoplasmatales viral DNA

DNA isolated from Mycoplasmatales viruses MVL51 and MVGs51 was infectious when mixed with Acholeplasma laidlawii BN1-Na1(R) cells. Infectivity was destroyed by deoxyribonuclease but not by ribonuclease, Pronase, or specific antiserum to the virus. Host mycoplasma cells were only competent for transfection during late-log growth phase. The rates of the establishment of DNase insensitivity of viral DNA transfectants were similar to those of bacteriophage systems. The dose-response curve for transfection suggested that an average of six molecules of DNA must interact with a cell in order to produce one infectious center. Mycoplasmatales virus DNA exhibited a low efficiency of infection; one infectious center required 4 x 10(5) virus equivalents of DNA.

Isolation of Mycoplasmatales viruses and characterization of MVL1, MVL52, and MVG51

Eleven Mycoplasmatales viruses are now known. Burst size, burst time, sensitivity to ultraviolet and the host range of three viruses that were studied are different. However, all three are naked, rod-shaped particles of similar size. Plaque morphology and the isolation of immune cells suggest that both virulent and nonvirulent infections are possible.