Antibodies response induced by recombinant virus-like particles from Triatoma virus and chimeric antigens from Trypanosoma cruzi.

BACKGROUND: The infection caused by the protozoan Trypanosoma cruzi affects humans and is called as Chagas disease. Currently, the main measures available to reduce the incidence of this disease are drug treatment and vector control. Traditionally, the development of vaccines occurs mainly through the use of antigenic candidates of the etiologic agent in the form of a vaccine preparation. Virus-like particles (VLPs) are structures analogous to viral capsids composed essentially of structural proteins and are widely used in vaccination protocols because of their immunostimulatory properties. In this context, the objective of this study was to use strategies in a murine immunization model to characterize the immunostimulatory capacity of VLPs from Triatoma virus (TrV-VLPs), analysed in the presence or absence of the aluminium vaccine adjuvant. In parallel, to characterize the immunogenic behaviour of four T. cruzi chimeric recombinant proteins (mix-IBMP) associated with TrV-VLPs or aluminium vaccine adjuvant. METHOD: We immunized BALB/c mice once or twice, depending on the strategy, and collected serum samples at 15, 30 and 45 days after the immunization. Subsequently, serum samples from animals immunized with TrV-VLPs were used to determine total IgG, IgG1, IgG2a, IgG2b and IgG3 anti-TrV-VLPs by enzyme-linked immunosorbent assay (ELISA). RESULTS: Data obtained demonstrate the ability of TrV-VLPs to preferably induce IgG2b and IgG3 type antibodies in the absence of aluminium adjuvant. In fact, the use of aluminium did not interfere with the total IgG profile of anti-TrV-VLPs. Interestingly, mix-IBMP had a better profile of total IgG, IgG1 and IgG3 subclasses when mixed with TrV-VLPs. CONCLUSION: In conclusion, these results suggest the potential of TrV-VLPs as a vaccine adjuvant and the use of T. cruzi chimeric antigens as a rational strategy for the development of vaccines against the experimental model of Chagas disease.

Exploring the role of genome and structural ions in preventing viral capsid collapse during dehydration.

Even though viruses evolve mainly in liquid milieu, their horizontal transmission routes often include episodes of dry environment. Along their life cycle, some insect viruses, such as viruses from the Dicistroviridae family, withstand dehydrated conditions with presently unknown consequences to their structural stability. Here, we use atomic force microscopy to monitor the structural changes of viral particles of Triatoma virus (TrV) after desiccation. Our results demonstrate that TrV capsids preserve their genome inside, conserving their height after exposure to dehydrating conditions, which is in stark contrast with other viruses that expel their genome when desiccated. Moreover, empty capsids (without genome) resulted in collapsed particles after desiccation. We also explored the role of structural ions in the dehydration process of the virions (capsid containing genome) by chelating the accessible cations from the external solvent milieu. We observed that ion suppression helps to keep the virus height upon desiccation. Our results show that under drying conditions, the genome of TrV prevents the capsid from collapsing during dehydration, while the structural ions are responsible for promoting solvent exchange through the virion wall.

X-ray structure of Triatoma virus empty capsid: insights into the mechanism of uncoating and RNA release in dicistroviruses.

In viruses, uncoating and RNA release are two key steps of successfully infecting a target cell. During these steps, the capsid must undergo the necessary conformational changes to allow RNA egress. Despite their importance, these processes are poorly understood in the family Dicistroviridae. Here, we used X-ray crystallography to solve the atomic structure of a Triatoma virus(TrV) empty particle (Protein Data Bank ID 5L7O), which is the resulting capsid after RNA release. It is observed that the overall shape of the capsid and of the three individual proteins is maintained in comparison with the mature virion. Furthermore, no channels indicative of RNA release are formed in the TrV empty particle. However, the most prominent change in the empty particle when compared with the mature virion is the loss of order in the N-terminal domain of the VP2 protein. In mature virions, the VP2 N-terminal domain of one pentamer is swapped with its twofold related copy in an adjacent pentamer, thereby stabilizing the binding between the pentamers. The loss of these interactions allows us to propose that RNA release may take place through transient flipping-out of pentameric subunits. The lower number of stabilizing interactions between the pentamers and the lack of formation of new holes support this model. This model differs from the currently accepted model for rhinoviruses and enteroviruses, in which genome externalization occurs by extrusion of the RNA through capsid channels.

Catalyst- and solvent-dependent stereodivergence in the intramolecular Et(2)Zn/Pd(0) -promoted carbonyl propargylation: mechanistic implications.

Carbonyl-tethered propargylic benzoates undergo intramolecular carbonylpropargylation upon treatment with Et2 Zn in the presence of a catalytic amount of Pd(0) with the formation of 2-alkynylcyclopentanol products. A ligand/solvent effect on the cis/trans selectivity (referring to the relative positions of alkynyl and OH groups) of ring-closure has been found. In a non-coordinating solvent (benzene), increasing the electron-donating ability of the phosphine ligand (while decreasing its dissociation ability) leads to an increased tendency towards the trans product. On the other hand, the combination of a coordinating solvent (THF) and PPh3 , an easily dissociated phosphine, results in the exclusive formation of cis products. Experimental and computational results are compatible with a divergent behavior of an allenylethylpalladium intermediate that partitions between competitive carbonyl-addition and transmetalation pathways, each leading to a different diastereoisomer. These results also suggest that the dissociating ability of the phosphine regulates that behavior.

Palladium-catalyzed cyclization/Heck- and cyclization/conjugate-addition-type sequences in the preparation of polysubstituted furans.

Palladium-catalyzed heterocyclization-coupling sequences have been developed starting from buta-1,2,3-trienyl carbinols and electron-deficient alkenes. Polysubstituted furans are formed where the heterocyclic ring originates from the elements of the butatrienyl carbinol while the electron-deficient olefin is incorporated as a C-3 substituent. In most cases, the reaction proceeds via a Heck-type pathway leading to the efficient formation of 3-vinylfurans. However, couplings with methyl vinyl ketone display a divergent behavior to afford selectively either Heck- or hydroarylation-type products depending on reaction conditions.