Biology subjects

Loos, A.

Publications and source records attributed to Loos, A..

4 recordsLinked to original sources

bioRxiv2025

Resources for molecular studies of unculturable obligate biotrophic fungal plant pathogens using their saprotrophic relatives

Obligate biotrophic plant pathogens like the powdery mildew fungi commit to a closely dependent relationship with their plant hosts and have lost the ability to grow and reproduce independently. Thus, at present, these organisms are not amenable to in vitro cultivation, which is a prerequisite for effective genetic modification and functional molecular studies. Saprotrophic fungi of the family Arachnopezizaceae are the closest known extant relatives of the powdery mildew fungi and may hold great potential for studying genetic components of their obligate biotrophic lifestyle. Here, we established telomere-to-telomere genome assemblies for two representatives of this family, Arachnopeziza aurata and A. aurelia. Both species harbor haploid genomes that are composed of 16 chromosomes at a genome size of 43.1 and 46.3 million base-pairs, respectively, which, in contrast to most powdery mildew genomes that are transposon-enriched, show a repeat content below 5% and signs of repeat-induced point mutation (RIP). Both species could be grown in liquid culture and on solid standard media and were sensitive to common fungicides such as hygromycin and fenhexamid. We successfully expressed a red fluorescent protein and hygromycin resistance in A. aurata following polyethylene glycol-mediated protoplast transformation, demonstrating that Arachnopeziza species are amenable to genetic alterations that may include gene replacement, gene modification, and gene complementation. With this work, we established a potential model system that promises to sidestep the need for genetic modification of powdery mildew fungi by using Arachnopeziza species as a proxy to uncover the molecular functions of powdery mildew proteins.

genomics↗

bioRxiv2023

Fungivorous protists in the rhizosphere of Arabidopsis thaliana - Diversity, functions, and publicly available cultures for experimental exploration

In the context of the soil food web, the transfer of plant-fixed energy and carbon to higher trophic levels has traditionally been attributed to two main energy channels: the fungal energy channel and the bacterial energy channel. Historically, protists were overlooked in the fungal energy channel, which was believed to be controlled by fungivorous microarthropods and nematodes. In this study, we investigated fungivorous protists in the rhizosphere of Arabidopsis thaliana. Our findings revealed a notable abundance and diversity of protists that have developed specialized strategies to overcome the protective cell wall of fungi. Among the identified species were two Vampyrellida (Rhizaria) species, namely Theratromyxa weberi and Platyreta germanica, as well as one Arcellinida (Amoebozoa) species, called Cryptodifflugia oviformis. While T. weberi typically consumed entire fungal cells, the other two species perforated fungal cell walls and extracted the cellular contents. We elucidate the feeding strategies and dietary ranges of the amoebae, highlighting the non-uniform nature of fungivory in protists, as different taxa have evolved distinct approaches to access fungi as a food source. Moreover, we provide publicly available cultures of these protists to facilitate further experimental investigations within the research community.

ecology↗

bioRxiv2022

Potent universal-coronavirus therapeutic activity mediated by direct respiratory administration of a Spike S2 domain-specific human neutralizing monoclonal antibody

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) marks the third novel {beta}-coronavirus to cause significant human mortality in the last two decades. Although vaccines are available, too few have been administered worldwide to keep the virus in check and to prevent mutations leading to immune escape. To determine if antibodies could be identified with universal coronavirus activity, plasma from convalescent subjects was screened for IgG against a stabilized pre-fusion SARS-CoV-2 spike S2 domain, which is highly conserved between human {beta}-coronavirus. From these subjects, several S2-specific human monoclonal antibodies (hmAbs) were developed that neutralized SARS-CoV-2 with recognition of all variants of concern (VoC) tested (Beta, Gamma, Delta, Epsilon, and Omicron). The hmAb 1249A8 emerged as the most potent and broad hmAb, able to recognize all human {beta}-coronavirus and neutralize SARS-CoV and MERS-CoV. 1249A8 demonstrated significant prophylactic activity in K18 hACE2 mice infected with SARS-CoV-2 lineage A and lineage B Beta, and Omicron VoC. 1249A8 delivered as a single 4 mg/kg intranasal (i.n.) dose to hamsters 12 hours following infection with SARS-CoV-2 Delta protected them from weight loss, with therapeutic activity further enhanced when combined with 1213H7, an S1-specific neutralizing hmAb. As little as 2 mg/kg of 1249A8 i.n. dose 12 hours following infection with SARS-CoV Urbani strain, protected hamsters from weight loss and significantly reduced upper and lower respiratory viral burden. These results indicate in vivo cooperativity between S1 and S2 specific neutralizing hmAbs and that potent universal coronavirus neutralizing mAbs with therapeutic potential can be induced in humans and can guide universal coronavirus vaccine development.

immunology↗

bioRxiv2020

Therapeutic activity of an inhaled potent SARS-CoV-2 neutralizing human monoclonal antibody in hamsters

SARS-CoV-2 infection results in viral burden in the upper and lower respiratory tract, enabling transmission and often leading to substantial lung pathology. Delivering the antiviral treatment directly to the lungs has the potential to improve lung bioavailability and dosing efficiency. As the SARS-CoV-2 Receptor Binding Domain (RBD) of the Spike (S) is increasingly deemed to be a clinically validated target, RBD-specific B cells were isolated from patients following SARS-CoV-2 infection to derive a panel of fully human monoclonal antibodies (hmAbs) that potently neutralize SARS-CoV-2. The most potent hmAb, 1212C2 was derived from an IgM memory B cell, has high affinity for SARS-CoV-2 RBD which enables its direct inhibition of RBD binding to ACE2. The 1212C2 hmAb exhibits in vivo prophylactic and therapeutic activity against SARS-CoV-2 in hamsters when delivered intraperitoneally, achieving a meaningful reduction in upper and lower respiratory viral burden and lung pathology. Furthermore, liquid nebulized inhale treatment of SARS-CoV-2 infected hamsters with as low as 0.6 mg/kg of inhaled dose, corresponding to approximately 0.03 mg/kg of lung deposited dose, mediated a reduction in respiratory viral burden that is below the detection limit, and mitigated lung pathology. The therapeutic efficacy achieved at an exceedingly low-dose of inhaled 1212C2 supports the rationale for local lung delivery and achieving dose-sparing benefits as compared to the conventional parenteral route of administration. Taken together, these results warrant an accelerated clinical development of 1212C2 hmAb formulated and delivered via inhalation for the prevention and treatment of SARS-CoV-2 infection.

immunology↗