Triatoma virus structural polyprotein expression, processing and assembly into virus-like particles

Abstract

In contrast to the current wealth of structural information concerning dicistrovirus particle structure, very little is known about their morphogenetic pathways. Here, we describe the expression of the two ORFs encoded by the Triatoma virus (TrV) genome. TrV, a member of the Cripavirus genus of the Dicistroviridae family, infects blood-sucking insects belonging to the Triatominae subfamily that act as vectors for the transmission of Trypanosoma cruzi, the aetiological agent of the Chagas disease. We have established a baculovirus-based model for the expression of the NS (non-structural) and P1 (structural) polyproteins. A preliminary characterization of the proteolytic processing of both polyprotein precursors has been performed using this system. We show that the proteolytic processing of the P1 polyprotein is strictly dependent upon the coexpression of the NS polyprotein, and that NS/P1 coexpression leads to the assembly of virus-like particles (VLPs) exhibiting a morphology and a protein composition akin to natural TrV empty capsids. Remarkably, the unprocessed P1 polypeptide assembles into quasispherical structures conspicuously larger than VLPs produced in NS/P1-coexpressing cells, likely representing a previously undescribed morphogenetic intermediate. This intermediate has not been found in members of the related Picornaviridae family currently used as a model for dicistrovirus studies, thus suggesting the existence of major differences in the assembly pathways of these two virus groups.

Plant and insect virus‐like particles: emerging nanoparticles for agricultural pest management

“…110 Baculovirus-mediated expression of the polyprotein P1 resulted in the assembly of quasi-spherical particles that were marginally larger than the VLPs produced by coexpression of NS and P1, which indicates that NS encodes a protease required for the maturation cleavage of P1 to form VLPs similar to the native virions in shape and size. 111 Intriguingly, administration of T. cruzi antigens directly mixed with TrV-based VLPs could stimulate higher expression of antibodies in mice compared with antigens alone, 112 VLPs have robust stability of storage at 4 °C for at least 18 months, 112 which is also beneficial for its application in medicine.…”

“…Triatoma virus (TrV) ( Triatovirus ) can infect triatomine bugs, hemipteran bloodsucking insects that transmit the human pathogen Trypanosoma cruzi 110 . Baculovirus‐mediated expression of the polyprotein P1 resulted in the assembly of quasi‐spherical particles that were marginally larger than the VLPs produced by co‐expression of NS and P1, which indicates that NS encodes a protease required for the maturation cleavage of P1 to form VLPs similar to the native virions in shape and size 111 . Intriguingly, administration of T. cruzi antigens directly mixed with TrV‐based VLPs could stimulate higher expression of antibodies in mice compared with antigens alone, 112 thereby indicating the potential of TrV‐based VLPs to function as a vaccine adjuvant for better protection against Chagas disease.…”

New Cell Lines Derived from Laboratory Colony Triatoma infestans and Rhodnius prolixus, Vectors of Trypanosoma cruzi, Do Not Harbour Triatoma Virus

“…Interestingly, TrV was also detected in a laboratory colony of another triatomine bug, Rhodnius prolixus [ 8 ]. Research into TrV has been hampered by the lack of an in vitro system for laboratory propagation of the virus outside the insect host [ 9 ]. To date, no insect cell line has been reported to support replication of TrV [ 10 ], possibly because the virus may be specific to triatomine bugs [ 11 ], and no cell lines derived from Triatoma or Rhodnius spp.…”

Triatoma Virus Recombinant VP4 Protein Induces Membrane Permeability through Dynamic Pores

“…On the other hand, the second ORF codes for the four structural proteins which build the capsid in the order N terminus-VP2-VP4-VP3-VP1-C terminus as a unique protein precursor called P1. Once the P1 precursor has been cleaved into VP0 (VP2 plus VP4), VP3, and VP1 by the protease encoded by the viral genome and after particle assembly, VP0 undergoes autoproteolytic cleavage into its components by an unknown mechanism that takes place only in RNA-encapsulating TrV particles (8,9).…”