Biology subjects

Alfonso, V.

Publications and source records attributed to Alfonso, V..

3 recordsLinked to original sources

bioRxiv2025

Incorporation of ChiA into AcMNPV occlusion bodies and its implications for oral infectivity

Baculoviruses are insect-specific viruses primarily employed in biological pest control and recombinant protein expression. As biopesticides, they offer numerous advantages over chemical pesticides and hold significant potential for application in integrated pest management (IPM). However, their slower action compared to conventional synthetic strategies has limited their widespread adoption. This study aimed to investigate the impact of incorporating a viral protein, AcChiA chitinase, which disrupts the gut peritrophic membrane of susceptible insects, into AcMNPV occlusion bodies in trans. This was achieved through the development of an insect cell line that facilitates the passive incorporation of this protein. The presence of ChiA was detected in dissolved occlusion bodies (OBs) preparations from infected transgenic lines, in a method-dependent manner, with the stronger signals observed in chimeric polyhedra. It is hypothesized that ChiA in OBs will increase peritrophic membrane permeability and facilitate primary infection. In bioassays, OBs produced in ChiA-expressing lines were associated with higher larval mortality than OBs produced in Sf9, consistent with a ChiA-mediated effect. Notably, the addition of ChiA proteins from stably transformed insect cell lines improved infection rates, particularly in recombinant baculoviruses, which exhibited a significant reduction in occlusion-derived virion (ODV) occlusion. This underscores the critical role of these proteins in the oral infection process. Consequently, it was possible to incorporate the ChiA protein from stably transformed insect cell lines into wild-type and recombinant baculovirus occlusion bodies, paving the way for potential applications in IPM with AcMNPV.

bioengineering↗

bioRxiv2024

Birnaviral Hijacking of Endosomal Membranes

Birnaviruses are a group of double-stranded RNA (dsRNA) viruses infecting birds, fish and insects. Early endosomes (EE) constitute the platform for viral replication. Here, we study the mechanism of birnaviral targeting of EE membranes. Using the Infectious Bursal Disease Virus (IBDV) as a model, we validate that the viral protein 3 (VP3) binds to phosphatidylinositol-3-phosphate (PI3P) present in EE membranes. We identify the domain of VP3 involved in PI3P-binding, named P2 and localized in the core of VP3, and establish the critical role of the arginine at position 200 (R200), conserved among all known birnaviruses. Mutating R200 abolishes viral replication. Moreover, we propose a two-stage modular mechanism for VP3 association with EE. Firstly, the carboxy-terminal region of VP3 adsorbs on the membrane, and then the VP3 core reinforces the membrane engagement by specifically binding PI3P through its P2 domain, additionally promoting PI3P accumulation. Significance StatementBirnaviruses are a family of viruses unique among the group of dsRNA viruses. Here, we show that VP3 seizes the endosomes by anchoring to the PI3P lipids in the luminal side of the EE membrane, in order to organize the viral replication factory. We propose a two-stage modular mechanism for VP3 association with PI3P-enriched EE. The significance of this work resides in the biochemical and biophysical insights on the mechanism of association of VP3 with EE and its role in the viral life cycle, which represents a substantial contribution toward understanding the replication strategy of these "non-canonical" viruses.

microbiology↗

bioRxiv2022

A fijivirus major viroplasm protein shows RNA-stimulated ATPase activity by adopting pentameric and hexameric assemblies of dimers

The fijivirus Mal de Rio Cuarto virus (MRCV) causes a devastating maize disease. Its non-structural protein P9-1, which shows ATPase and RNA binding activities, is the major component of the intracellular viroplasm where virus replication takes place. Here, we established that the 24 C-terminal residues (C-arm) of P9-1 are required for the formation of viroplasm-like structures (VLS) in vivo and for the protein multimerization in vitro. Employing an integrative structural approach, we found that the C-arm is dispensable for P9-1 dimer assembly, but essential for the formation of doughnut-shaped pentamers and hexamers of dimers (decamers and dodecamers). Both assemblies, larger than those reported for other reoviruses, contain disordered loops oriented towards the inner pore of the structures, where RNA binding sites and conditional proteasome-mediated degradation signals (PEST) were predicted. In vitro assays demonstrated that ssRNA binding is favored towards P9-1 (do)decamers over the dimeric {Delta}C-arm version. In addition, although both P9-1 and P9-1{Delta}C-arm catalyze the hydrolysis of ATP with similar activity values, an RNA-stimulated ATPase activity was only observed in the full-length protein, indicating a C-arm-mediated interaction between the ATP catalytic site and the allosteric RNA binding sites in the (do)decameric assemblies. Computational studies revealed a stronger preference of phosphate moieties to the decamer in the pore and the C-arm regions, suggesting that the allosteric communication between the ATP and RNA binding sites is favored with this protein arrangement. Overall, our work reveals the structural versatility of a major viroplasm protein providing unprecedented insights into fijivirus viroplasm assembly and function and establishes the structural basis for the development of antiviral strategies against the Mal de Rio Cuarto crop disease.

biochemistry↗