The Junín virus strain Candid#1 was developed as a live attenuated vaccine for Argentine hemorrhagic fever. In this article, we report sequence information of the L and S RNAs of Junín virus Candid#1 and XJ#44 strains, and show the comparisons with the XJ13 wild-type strain and with other Junín virus strains, like Romero, IV4454 and MC2 strains, and other closely and distantly related arenaviruses. Comparisons of the nucleotide and amino acid sequences of all genes of three strains from the same vaccine genealogy, revealed different point mutations that could be associated with the attenuated phenotype. A 91% of the mutations found are consistent with a hypothesis of progressive attenuation of virulence from XJ13 to XJ#44 and to Candid#1; 39% of mutations were observed in XJ#44 and conserved in Candid#1, while another 52% of the mutations appeared only in Candid#1 strain. The remaining 9% corresponded to reverse mutations in the L gene. In summary, the present work shows a set of mutations that could be related to the virulence attenuation phenomenon. This information will serve as a starting point to study this biological phenomenon, provided that a reverse genetics system for Junín virus is developed to allow the generation of infectious virions with specific mutations.

Designing degenerate PCR primers for templates of unknown nucleotide sequence may be a very difficult task. In this paper, we present a new method to design degenerate primers, implemented in family-specific degenerate primer design (FAS-DPD) computer software, for which the starting point is a multiple alignment of related amino acids or nucleotide sequences. To assess their efficiency, four different genome collections were used, covering a wide range of genomic lengths: Arenavirus (10 × 104 nucleotides), Baculovirus (0.9 × 105 to 1.8 × 105 bp), Lactobacillus sp. (1 × 106 to 2 × 106 bp), and Pseudomonas sp. (4 × 106 to 7 × 106 bp). In each case, FAS-DPD designed primers were tested computationally to measure specificity. Designed primers for Arenavirus and Baculovirus were tested experimentally. The method presented here is useful for designing degenerate primers on collections of related protein sequences, allowing detection of new family members.

Two new vaccine candidates against dengue virus (DENV) infection were generated by fusing the coding sequences of the self-budding Z protein from Junin virus (Z-JUNV) to those of two cryptic peptides (Z/DENV-P1 and Z/DENV-P2) conserved on the envelope protein of all serotypes of DENV. The capacity of these chimeras to generate virus-like particles (VLPs) and to induce virus-neutralizing antibodies in mice was determined. First, recombinant proteins that displayed reactivity with a Z-JUNV-specific serum by immunofluorescence were detected in HEK-293 cells transfected with each of the two plasmids and VLP formation was also observed by transmission electron microscopy. Next, we determined the presence of antibodies against the envelope peptides of DENV in the sera of immunized C57BL/6 mice. Results showed that those animals that received Z/DENV-P2 DNA coding sequences followed by a boost with DENV-P2 synthetic peptides elicited significant specific antibody titers (≥6.400). Finally, DENV plaque-reduction neutralization tests (PRNT) were performed. Although no significant protective effect was observed when using sera of Z/DENV-P1-immunized animals, antibodies raised against vaccine candidate Z/DENV-P2 (diluted 1:320) were able to reduce in over 50 % the number of viral plaques generated by infectious DENV particles. This reduction was comparable to that of the 4G2 DENV-specific monoclonal cross-reactive (all serotypes) neutralizing antibody. We conclude that Z-JUNV-VLP is a valid carrier to induce antibody-mediated immune responses in mice and that Z/DENV-P2 is not only immunogenic but also protective in vitro against infection of cells with DENV, deserving further studies. On the other side, DENV's fusion peptide-derived chimera Z/DENV-P1 did not display similar protective properties.

BackgroundArenavirus matrix protein Z plays an important role in virus budding and is able to generate enveloped virus-like-particles (VLPs) in absence of any other viral proteins. In these VLPs, Z protein is associated to the plasma membrane inner surface by its myristoyl residue. Budding induction and vesicle formation properties can be exploited to generate enveloped VLPs platform. These structures can be designed to carry specific antigen in the inner side or on the surface of VLPs.Vaccines based on VLPs are a highly effective type of subunit vaccines that mimic the overall structure of virus particles in absence of viral nucleic acid, being noninfectious.In this work we assayed the capacity of Junin Z protein to produce VLPs carrying the green fluorescent protein (eGFP), as a model antigen.ResultsIn this report the Junin Z protein ability to produce VLPs from 293T cells and its capacity to deliver a specific antigen (eGFP) fused to Z was evaluated. Confocal microscopy showed a particular membrane bending in cells expressing Z and a spot welded distribution in the cytoplasm. VLPs were detected by TEM (transmission electron microscopy) and were purified from cell supernatant. The proteinase protection assay demonstrated the VLPs integrity and the absence of degradation of the fused antigen, thus indicating its internal localization. Finally, immunization of mice with purified VLPs produced high titres of anti-eGFP antibodies compared to the controls.ConclusionsIt was proved that VLPs can be generated from cells transfected with a fusion Junin virus Z-eGFP protein in absence of any other viral protein, and the capacity of Z protein to support fusions at the C-terminal, without impairing its budding activity, allowing vehiculization of specific antigens into VLPs.

Vaccination has been one of the most successful and the most significant scientific advances in human health and life expectancy all around the globe. The World Health Organization considers that immunization should be recognized as the main component of human health right, due to the fact that vaccination prevents 2.5 million deaths annually (World Health Organization, 2011). The most successful vaccines have been developed using conventional methods that follow the paradigm established by Pasteur: "to isolate, inactivate and inject" the pathogen microorganism and mimic a natural infection. Recently, metagenomics have played an important role in the discovery of new immunogens for vaccine design and the selection of antigens based on genomic information. The main approach that has used this strategy has been called "reverse vaccinology". This promising and arising field allows the screening of the entire potential antigenic repertoire of an organism using predictive bioinformatic tools. Once the antigenic protein or proteins have been selected, they are expressed and purified using molecular cloning and in vitro expression techniques. Following the in vitro production step, they are probed in animal models to evaluate the in vivo protective strength of the immune response. The main aim of this in vivo approach is to evaluate the ability of the immune response to eliminate or neutralize the pathogen at the time of infection. Those antigens capable of generate a specific immune response with neutralizing activity for natural infections are the best candidate vaccines. In this review we summarize the evolution of vaccinology since its inception, with special emphasis on the development of VLPs as vaccine platforms and their future in preventive medicine and we introduce a new recombinant platform for antigen presentation based on Junin virus VLPs (JUNV-VLPs).