A High-Content Screen for Mucin-1-Reducing Compounds Identifies Fostamatinib as a Candidate for Rapid Repurposing for Acute Lung Injury

Drug repurposing has the advantage of identifying potential treatments on a shortened timescale. In response to the pandemic spread of SARS-CoV-2, we took advantage of a high-content screen of 3,713 compounds at different stages of clinical development to identify FDA-approved compounds that reduce mucin-1 (MUC1) protein abundance. Elevated MUC1 levels predict the development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) and correlate with poor clinical outcomes. Our screen identifies fostamatinib (R788), an inhibitor of spleen tyrosine kinase (SYK) approved for the treatment of chronic immune thrombocytopenia, as a repurposing candidate for the treatment of ALI. In vivo, fostamatinib reduces MUC1 abundance in lung epithelial cells in a mouse model of ALI. In vitro, SYK inhibition by the active metabolite R406 promotes MUC1 removal from the cell surface. Our work suggests fostamatinib as a repurposing drug candidate for ALI.

Identification of Races 0 and 2 of Cladosporium fulvum (syn Passalora fulva) on Tomato in the Cinturón Hortícola de La Plata, Argentina

Surveys aimed at evaluating the incidence and severity of a new disease that developed in greenhouses cultivated with tomato (Solanum lycopersicum L.) were performed during 2009 and 2010 in greenhouses of the cultivars Elpida (Enza Zaden) and Colibrí (Clause) in an area of tomato production known as the Cinturón Hortícola de La Plata (the "horticultural belt of La Plata"). The disease had a 100% prevalence and 90% incidence within the ten 250 m² greenhouses that were monitored in 2009, 2010, and 2011. In two consecutive assays, severity was 40%. The wide distribution of the disease suggests that the tomato hybrids under use lack resistance genes. The upper surface of diseased leaves had pale green to yellowish, 1- to 1.5-cm spots with undefined margins that progressed to a yellowish brown color, while on the lower side they had pale brown to brown sporulation of fungal conidiophores and conidia. Monosporic fungal cultures were obtained by needle transfer of conidia from sporulating areas of leaves (n = 20) to water agar medium. On 2% potato dextrose agar (PDA) the colonies of the relatively low growing fungus were strongly pigmented, greenish grey, and black on the reverse of the plate. The fungus developed one-celled, pale olive-green, ovoid conidia on long, branched chains, which arose from pigmented conidiophores, corresponding to the description of Cladosporium fulvum made by Joosten and de Wit (1). The identity of two isolates was confirmed by amplifying the 580-bp ITS sequences by means of primers ITS4 (5'-TCCTCCGCTTATTGATATGC-3') and ITS5 (5'-GAATTCGGAAGTAAAAGTCGTAACAAGG-3') (ITS sequence Race 0 JQ768324.1 and Race 2 JQ768325.1). Both were 100% homologous to the ITS sequences of C. fulvum strains ATCC44962 (AF393700) and ATCC44960 (AF303701). Monosporic cultures of four isolates, each obtained from leaves collected from different plants growing in different greenhouses, were inoculated on a set of differential genotypes of tomato: cvs. Moneymaker, Cf-0, Cf-2, Cf-4, Cf-5, and Cf-9 (kindly provided by the Laboratory of Phytopathology of Wageningen University). Three plants of each tomato genotype at the 5 to 6 true leaf stage were inoculated by spraying a 10⁵ conidia/ml conidial suspension of C. fulvum on the leaflets of the 3rd and 4th leaf. Inoculation tests of each isolate were repeated at least twice. After inoculation, plants were grown in the greenhouse at 13 to 29°C and 99% relative humidity. However, for the first 20 h after inoculation, plants were kept in the dark. They were regularly monitored and were scored as resistant or susceptible at 20 days after inoculation. Susceptible genotypes developed pale green to yellow spots on the abaxial leaf surface and pale brown to olivaceous brown sporulation on the adaxial side. Plants lacking disease symptoms were considered resistant. Inoculated fungi were reisolated from infected tissue and the identity of the fungal cultures confirmed based on morphology and the ITS sequence. Based on the reactions of the tomato genotypes, two races were identified, three isolates (race 2) developed symptoms only in cv. MM Cf-2, while the remaining isolate (race 0) provoked symptoms only in cv. MM Cf-0. Reference: (1) M. Joosten and P. de Wit. Annu Rev Phytopathol. 37:335, 1999.

Fluorescent Pseudomonas species causing post-harvest decay of endives in Argentina

A post-harvest bacterial decay was observed on ready-to-use French endives in Argentina. Affected chicons showed browning and soft-rot of inner leaves and marginal necrosis. Physiological and biochemical tests allowed us to identify the isolates from endive as Pseudomonas fluorescens bv. III, Pseudomonas fluorescens bv. V, and Pseudomonas cichorii. Pathogenicity was verified on RTU healthy endives by inoculation with each bacterial species, and also with the mixture of the 3 strains. P. cichorii caused dark brown necrosis of the margins of outer leaves; both isolates of P. fluorescens caused browning and soft-rotting of inner leaves, while the mixture induced all the described symptoms, that were similar to those found in natural infection. Identity of bacterial isolates was confirmed by RFLP analysis of a PCR-DNA fragment amplified from the 16S rRNA gene. This is the first record of a post-harvest decay in endives in Argentina.

First Report of Fusarium solani Causing Stunt on Lisianthus

Fusarium solani Mart. (Sacc.) is the causal agent of stem rot and damping-off of lisianthus (Eustoma grandiflorum (Raf.) Shinn.) (1). Since the end of the 1980s, when this flower crop was introduced in Argentina, it has been affected by a basal stem rot (2). A previously undescribed disease was observed in 100% of the greenhouses in the Buenos Aires Province that grow lisianthus. Symptoms that developed after seedlings were transplanted included stunting, shortened internodes with reduced stem diameter, and small narrow leaves that were a dull green color. Some affected plants turned yellow-brownish and died 2 to 3 months after transplanting. Other plants recovered but produced low quality flowers later than normal. A third group of plants remained stunted (5 to 10 cm high) until the last flower harvest (about 8 to 10 months). F. solani was consistently isolated from basal stems and roots of diseased plants. For pathogenicity tests, inoculum was produced by culturing the fungus for 10 days in petri dishes containing sterile moistened rice. Inoculum was air dried, crushed, and mixed with soil that had been autoclaved at 112°C for 40 min on each of two consecutive days. The propagules in the soil were estimated by soil plate dilutions on the Nash & Snyder-PCNB medium at a ratio of about 10⁴ CFU/g soil. Twenty plants of each cultivar Echo White and Echo Blue, whose roots had been pruned, were planted in both infested and noninfested soil. After about 40 days, stunting was observed in 85% of the inoculated plants, while controls remained asymptomatic. F. solani was reisolated from symptomatic plants, thus fulfilling Koch's postulates. A test also was conducted in a commercial greenhouse that produced lisianthus for several years, in which healthy plants were planted in three plots fumigated with methyl bromide and in three nonfumigated plots. The mean cfu/g soil of F. solani in the methyl-bromide treated plots was 5 × 10² and 1.6 × 10⁴ CFU/g in the nontreated plot. After 120 days, the incidence of stunting in the treated plots was 0.6 and about 88% in the control plots. F. solani was recovered from symptomatic plants. Because disinfestation of soil is generally practiced in flower production, stunted plants are limited and can be confused with root problems. This is the first report of F. solani causing stunt on lisianthus. References: (1) J. J. Taubenhaus and W. N. Ezekiel. Phytopathology 24:19, 1934. (2) S. M. Wolcan and G. A. Lori. Invest. Agr. Prot. Veg. 11:465, 1996.

First Report of Powdery Mildew on Heath Aster Caused by Erysiphe cichoracearum in Argentina

In 1995, powdery mildew was observed on commercial greenhousegrown Aster ericoides L. from La Plata, Buenos Aires Province. The disease affected about 95% of the growers. Mildew first appeared as white circular patches on the adaxial surface of leaves. As disease progressed, the abaxial surface of leaves, petioles, stems, and calyces were covered by cottony masses of mycelium and conidia, and basal leaves later wilted and died. Young plants (4 to 5 leaves) through flowering plants were affected. Conidia were ovoid-cylindrical, often slightly constricted at the ends, and were produced in chains on unbranched conidiophores. Conidia lacked fibrosin bodies and ranged from 30 to 41 μm × 10 to 19 μm. Long unbranched germ tubes were formed from the ends of conidia. The morphological characteristics of the fungus fit those described for Erysiphe cichoracearum DC (1). In addition, the perfect stage was found on older tissues. Subglobose, dark brown cleistothecia (105 to 210 μm in diameter) with a basal ring of myceloid appendages were observed. Cleistothecia contained multiple ellipsoid asci (48 to 69 μm × 30 to 37 μm) with two hyaline, one-celled, ellipsoid ascospores (22 to 26 μm × 11 to 15 μm). Pathogenicity was tested by pressing diseased leaves onto healthy leaves of aster cv. Sunset and incubating plants in humidity chambers for 48 h. The powdery mildew that developed was morphologically identical to the original isolate. This is the first report of E. cichoracearum on heath aster in Argentina. Reference: (1) H. J. Boesewinkel. Bot. Rev. 46:167, 1980.

[Bacterial leaf blight affecting Syngonium podophyllum in Argentina]

Bacterial leaf blight of Syngonium podophyllum caused by Xanthomonas campestris pv. syngonii is recorded for the first time in Argentina. The first symptom of the disease was an interveinal watersoaking of leaves, the tissues became chlorotic and finally necrotic over areas of about 4 cm. The identification of the causal microorganism was based on disease symptoms, morphological, physiological and biochemical characteristics and pathogenicity test.