Metformin Inhibits Zika Virus Infection in Trophoblast Cell Line.

Zika virus (ZIKV) infections have been associated with severe clinical outcomes, which may include neurological manifestations, especially in newborns with intrauterine infection. However, licensed vaccines and specific antiviral agents are not yet available. Therefore, a safe and low-cost therapy is required, especially for pregnant women. In this regard, metformin, an FDA-approved drug used to treat gestational diabetes, has previously exhibited an anti-ZIKA effect in vitro in HUVEC cells by activating AMPK. In this study, we evaluated metformin treatment during ZIKV infection in vitro in a JEG3-permissive trophoblast cell line. Our results demonstrate that metformin affects viral replication and protein synthesis and reverses cytoskeletal changes promoted by ZIKV infection. In addition, it reduces lipid droplet formation, which is associated with lipogenic activation of infection. Taken together, our results indicate that metformin has potential as an antiviral agent against ZIKV infection in vitro in trophoblast cells.

Production and Immunogenicity Assessment of LTp50: An Escherichia coli-Made Chimeric Antigen Targeting S1- and S2-Epitopes from the SARS-CoV-2/BA.5 Spike Protein.

Subunit vaccines stand as a leading approach to expanding the current portfolio of vaccines to fight against COVID-19, seeking not only to lower costs but to achieve long-term immunity against variants of concern and have the main attributes that could overcome the limitations of the current vaccines. Herein a chimeric protein targeting S1 and S2 epitopes, called LTp50, was designed as a convenient approach to induce humoral responses against SARS-CoV-2. LTp50 was produced in recombinant Escherichia coli using a conventional pET vector, recovering the expected antigen in the insoluble fraction. LTp50 was purified by chromatography (purity > 90%). The solubilization and refolding stages helped to obtain a stable protein amenable for vaccine formulation. LTp50 was adsorbed onto alum, resulting in a stable formulation whose immunogenic properties were assessed in BALB/c mice. Significant humoral responses against the S protein (BA.5 variant) were detected in mice subjected to three subcutaneous doses (10 µg) of the LTp50/alum formulation. This study opens the path for the vaccine formulation optimization using additional adjuvants to advance in the development of a highly effective anti-COVID-19 vaccine directed against the antigenic regions of the S protein, which are less prone to mutations.

Modulation of the Altered Intestinal Microbiota by Use of Antibiotics with a Novel Synbiotic on Wistar Rats.

The use of antibiotics unbalances the intestinal microbiota. Probiotics, prebiotics, and synbiotics are alternatives for these unbalances. The effects of a new synbiotic composed of probiotic Saccharomyces boulardii CNCM I-745 and fructans from Agave salmiana (fAs) as prebiotics were assessed to modulate the intestinal microbiota. Two probiotic presentations, the commercial probiotic (CP) and the microencapsulated probiotic (MP) to improve those effects, were used to prepare the synbiotics and feed Wistar rats subjected to antibiotics (AB). Eight groups were studied, including five controls and three groups to modulate the microbiota after the use of antibiotics: G5: AB + MP-synbiotic, G6: AB + CP-synbiotic, and G8: AB + fAs. All treatments were administered daily for 7 days. On days 7 and 21, euthanasia was performed, cecum tissue was recovered and used to evaluate histological analysis and to study microphotograph by TEM, and finally, bacterial DNA was extracted and 16S rRNA gene metabarcode sequencing was performed. Histological analysis showed less epithelial damage and more abundance of the intestinal microbiota in the groups G5, G6, and G8 in comparison with the AB control group after 7 days. Microphotograph of the cecum at 2 weeks post treatment showed that G5 and G6 presented beneficial effects in epithelial reconstruction. Interestingly, in the groups that used the synbiotic without AB (G3 and G4) in addition to contributing to the recovery of the autochthonous microbiota, it promotes the development of beneficial microorganisms; those results were also achieved in the groups that used the synbiotic with AB enhancing the bacterial diversity and regulating the impact of AB.

Ultrastructural and Functional Characterization of Mitochondrial Dynamics Induced by Human Respiratory Syncytial Virus Infection in HEp-2 Cells.

Human respiratory syncytial virus (hRSV) is the leading cause of acute lower respiratory tract infections in children under five years of age and older adults worldwide. During hRSV infection, host cells undergo changes in endomembrane organelles, including mitochondria. This organelle is responsible for energy production in the cell and plays an important role in the antiviral response. The present study focuses on characterizing the ultrastructural and functional changes during hRSV infection using thin-section transmission electron microscopy and RT-qPCR. Here we report that hRSV infection alters mitochondrial morphodynamics by regulating the expression of key genes in the antiviral response process, such as Mfn1, VDAC2, and PINK1. Our results suggest that hRSV alters mitochondrial morphology during infection, producing a mitochondrial phenotype with shortened cristae, swollen matrix, and damaged membrane. We also observed that hRSV infection modulates the expression of the aforementioned genes, possibly as an evasion mechanism in the face of cellular antiviral response. Taken together, these results advance our knowledge of the ultrastructural alterations associated with hRSV infection and might guide future therapeutic efforts to develop effective antiviral drugs for hRSV treatment.

Description and quantification of micronucleus and nuclear abnormalities in erythrocytes of the sentinel green turtle (Chelonia mydas) with fluorescence microscopy.

Contamination in marine ecosystems is of the most critical threats to marine turtles. The identification of useful biomarkers to detect and monitor the physiological and clinical effects of pollutants on these populations will allow early detection of alterations (e.g., mutagenic damages) that could risk their viability or favor the development of diseases, thus threatening the biodiversity of these ecosystems and human population. This study is aimed at describing and quantifying nuclear anomalies in peripheral blood erythrocytes of green turtles (Chelonia mydas) from three distinct foraging areas in Mexico (Akumal, Xcalak, and Punta Herrero). We developed a novel morphological index that could be used as a biomarker to identify abnormal nuclei in peripheral blood erythrocytes. Here we describe for the first time in C. mydas, with a species-specific staining protocol, distinct nuclear abnormalities such as blebbed, lobed, notched, eight shape nuclei, and binucleated cells. These nuclear abnormalities were present in > 90 % of the subjects (n = 30). Moreover, 50 % of the organisms presented erythrocytes with micronuclei. The number of nuclear abnormalities did not correlate with size of the green turtles or differ between sites, or health status. We found a higher frequency of green turtles with nuclear abnormalities in the southern region (Punta Herrero and Xcalak) with the highest frequency of micronucleus and buds. The former could be associated to the constant exposure to chemical pollutants of oceanographic origin in the southern coast of Quintana Roo. Furthermore, the increasing anthropogenic pollution in Akumal could also explain the highest variability in the number of nuclear abnormalities presented in resident individuals. We propose that a long-term monitoring programs of green turtle populations in the Mexican Caribbean that include a micronucleus test could be a useful to determine possible mutagenic damage in these animals.

Astrocytes derived from neural progenitor cells are susceptible to Zika virus infection.

Zika virus (ZIKV) was first isolated in 1947. From its isolation until 2007, symptoms of ZIKV-caused disease were limited (e.g., fever, hives, and headache); however, during the epidemic in Brazil in 2014, ZIKV infection caused Guillain-Barré syndrome in adults and microcephaly in fetuses and infants of women infected during pregnancy. The neurovirulence of ZIKV has been studied using neural progenitor cells (NPCs), brain organoids, neurons, and astrocytes. NPCs and astrocytes appear to be the most susceptible cells of the Central Nervous System to ZIKV infection. In this work, we aimed to develop a culture of astrocytes derived from a human NPC cell line. We analyze how ZIKV affects human astrocytes and demonstrate that 1) ZIKV infection reduces cell viability, increases the production of Reactive Oxygen Species (ROS), and results in high viral titers; 2) there are changes in the expression of genes that facilitate the entry of the virus into the cells; 3) there are changes in the expression of genes involved in the homeostasis of the glutamatergic system; and 4) there are ultrastructural changes in mitochondria and lipid droplets associated with production of virions. Our findings reveal new evidence of how ZIKV compromises astrocytic functionality, which may help understand the pathophysiology of ZIKV-associated congenital disease.

Production and Purification of LTB-RBD: A Potential Antigen for Mucosal Vaccine Development against SARS-CoV-2.

Most of the current SARS-CoV-2 vaccines are based on parenteral immunization targeting the S protein. Although protective, such vaccines could be optimized by inducing effective immune responses (neutralizing IgA responses) at the mucosal surfaces, allowing them to block the virus at the earliest stage of the infectious cycle. Herein a recombinant chimeric antigen called LTB-RBD is described, which comprises the B subunit of the heat-labile enterotoxin from E. coli and a segment of the RBD from SARS-CoV-2 (aa 439-504, carrying B and T cell epitopes) from the Wuhan sequence and the variant of concern (VOC)-delta. Since LTB is a mucosal adjuvant, targeting the GM1 receptor at the surface and facilitating antigen translocation to the submucosa, this candidate will help in designing mucosal vaccines (i.e., oral or intranasal formulations). LTB-RBD was produced in E. coli and purified to homogeneity by IMAC and IMAC-anionic exchange chromatography. The yields in terms of pure LTB-RBD were 1.2 mg per liter of culture for the Wuhan sequence and 3.5 mg per liter for the delta variant. The E. coli-made LTB-RBD induced seric IgG responses and IgA responses in the mouth and feces of mice when subcutaneously administered and intestinal and mouth IgA responses when administered nasally. The expression and purification protocols developed for LTB-RBD constitute a robust system to produce vaccine candidates against SARS-CoV-2 and its variants, offering a low-cost production system with no tags and with ease of adaptation to new variants. The E. coli-made LTB-RBD will be the basis for developing mucosal vaccine candidates capable of inducing sterilizing immunity against SARS-CoV-2.

Production and characterization of chimeric SARS-CoV-2 antigens based on the capsid protein of cowpea chlorotic mottle virus.

The COVID-19 pandemic has highlighted the need for new vaccine platforms to rapidly develop solutions against emerging pathogens. In particular, some plant viruses offer several advantages for developing subunit vaccines, such as high expression rates in E. coli, high immunogenicity and safety, and absence of pre-immunity that could interfere with the vaccine's efficacy. Cowpea chlorotic mottle virus (CCMV) is a model system that has been extensively characterized, with key advantages for its use as an epitope carrier. In the present study, three relevant epitopes from the SARS-CoV-2 Spike protein were genetically inserted into the CCMV CP and expressed in E. coli cultures, resulting in the CCMV1, CCMV2, and CCMV3 chimeras. The recombinant CP mutants were purified from the formed inclusion bodies and refolded, and their immunogenicity as a subunit vaccine was assessed in BALB/c mice. The three mutants are immunogenic as they induce high IgG antibody titers that recognize the recombinant full-length S protein. This study supports the application of CCMV CP as an attractive carrier for the clinical evaluation of vaccine candidates against SARS-CoV-2. Furthermore, it suggests that VLPs assembled from these chimeric proteins could result in antigens with better immunogenicity.

Construction of a Chikungunya Virus, Replicon, and Helper Plasmids for Transfection of Mammalian Cells.

The genome of Alphaviruses can be modified to produce self-replicating RNAs and virus-like particles, which are useful virological tools. In this work, we generated three plasmids for the transfection of mammalian cells: an infectious clone of Chikungunya virus (CHIKV), one that codes for the structural proteins (helper plasmid), and another one that codes nonstructural proteins (replicon plasmid). All of these plasmids contain a reporter gene (mKate2). The reporter gene in the replicon RNA and the infectious clone are synthesized from subgenomic RNA. Co-transfection with the helper and replicon plasmids has biotechnological/biomedical applications because they allow for the delivery of self-replicating RNA for the transient expression of one or more genes to the target cells.

Synthesis and immunogenicity assessment of a gold nanoparticle conjugate for the delivery of a peptide from SARS-CoV-2.

The development of vaccines is a crucial response against the COVID-19 pandemic and innovative nanovaccines could increase the potential to address this remarkable challenge. In the present study a B cell epitope (S461-493) from the spike protein of SARS-CoV-2 was selected and its immunogenicity validated in sheep. This synthetic peptide was coupled to gold nanoparticles (AuNP) functionalized with SH-PEG-NH2 via glutaraldehyde-mediated coupling to obtain the AuNP-S461-493 candidate, which showed in s.c.-immunized mice a superior immunogenicity (IgG responses) when compared to soluble S461-493; and led to increased expression of relevant cytokines in splenocyte cultures. Interestingly, the response triggered by AuNP-S461-493 was similar in magnitude to that induced using a conventional strong adjuvant (Freund's adjuvant). This study provides a platform for the development of AuNP-based nanovaccines targeting specific SARS-CoV-2 epitopes.

The Role of Virus-Like Particles in Medical Biotechnology.

Virus-like particles (VLPs) are protein-based, nanoscale, self-assembling, cage architectures, which have relevant applications in biomedicine. They can be used for the development of vaccines, imaging approaches, drug and gene therapy delivery systems, and in vitro diagnostic methods. Today, three relevant viruses are targeted using VLP-based recombinant vaccines. VLP-based drug delivery, nanoreactors for therapy, and imaging systems are approaches under development with promising outcomes. Several VLP-based vaccines are under clinical evaluation. Herein, an updated view on the VLP-based biomedical applications is provided; advanced methods for the production, functionalization, and drug loading of VLPs are described, and perspectives for the field are identified.

Challenges and Opportunities for the Biotechnology Research Community during the Coronavirus Pandemic.

The coronavirus disease 2019 (COVID-19) pandemic has presented some significant challenges to the scientific community. However, this has also offered opportunities for the pursuit of new scientific activities, and in particular for the field of biotechnology.

Packaging of Genomic RNA in Positive-Sense Single-Stranded RNA Viruses: A Complex Story.

The packaging of genomic RNA in positive-sense single-stranded RNA viruses is a key part of the viral infectious cycle, yet this step is not fully understood. Unlike double-stranded DNA and RNA viruses, this process is coupled with nucleocapsid assembly. The specificity of RNA packaging depends on multiple factors: (i) one or more packaging signals, (ii) RNA replication, (iii) translation, (iv) viral factories, and (v) the physical properties of the RNA. The relative contribution of each of these factors to packaging specificity is different for every virus. In vitro and in vivo data show that there are different packaging mechanisms that control selective packaging of the genomic RNA during nucleocapsid assembly. The goals of this article are to explain some of the key experiments that support the contribution of these factors to packaging selectivity and to draw a general scenario that could help us move towards a better understanding of this step of the viral infectious cycle.

Efficient support of virus-like particle assembly by the HIV-1 packaging signal.

The principal structural component of a retrovirus particle is the Gag protein. Retroviral genomic RNAs contain a 'packaging signal' ('Ψ') and are packaged in virus particles with very high selectivity. However, if no genomic RNA is present, Gag assembles into particles containing cellular mRNA molecules. The mechanism by which genomic RNA is normally selected during virus assembly is not understood. We previously reported (Comas-Garcia et al., 2017) that at physiological ionic strength, recombinant HIV-1 Gag binds with similar affinities to RNAs with or without Ψ, and proposed that genomic RNA is selectively packaged because binding to Ψ initiates particle assembly more efficiently than other RNAs. We now present data directly supporting this hypothesis. We also show that one or more short stretches of unpaired G residues are important elements of Ψ; Ψ may not be localized to a single structural element, but is probably distributed over >100 bases.

Dissection of specific binding of HIV-1 Gag to the 'packaging signal' in viral RNA.

Selective packaging of HIV-1 genomic RNA (gRNA) requires the presence of a cis-acting RNA element called the 'packaging signal' (Ψ). However, the mechanism by which Ψ promotes selective packaging of the gRNA is not well understood. We used fluorescence correlation spectroscopy and quenching data to monitor the binding of recombinant HIV-1 Gag protein to Cy5-tagged 190-base RNAs. At physiological ionic strength, Gag binds with very similar, nanomolar affinities to both Ψ-containing and control RNAs. We challenged these interactions by adding excess competing tRNA; introducing mutations in Gag; or raising the ionic strength. These modifications all revealed high specificity for Ψ. This specificity is evidently obscured in physiological salt by non-specific, predominantly electrostatic interactions. This nonspecific activity was attenuated by mutations in the MA, CA, and NC domains, including CA mutations disrupting Gag-Gag interaction. We propose that gRNA is selectively packaged because binding to Ψ nucleates virion assembly with particular efficiency.

On the Selective Packaging of Genomic RNA by HIV-1.

Like other retroviruses, human immunodeficiency virus type 1 (HIV-1) selectively packages genomic RNA (gRNA) during virus assembly. However, in the absence of the gRNA, cellular messenger RNAs (mRNAs) are packaged. While the gRNA is selected because of its cis-acting packaging signal, the mechanism of this selection is not understood. The affinity of Gag (the viral structural protein) for cellular RNAs at physiological ionic strength is not much higher than that for the gRNA. However, binding to the gRNA is more salt-resistant, implying that it has a higher non-electrostatic component. We have previously studied the spacer 1 (SP1) region of Gag and showed that it can undergo a concentration-dependent conformational transition. We proposed that this transition represents the first step in assembly, i.e., the conversion of Gag to an assembly-ready state. To explain selective packaging of gRNA, we suggest here that binding of Gag to gRNA, with its high non-electrostatic component, triggers this conversion more readily than binding to other RNAs; thus we predict that a Gag-gRNA complex will nucleate particle assembly more efficiently than other Gag-RNA complexes. New data shows that among cellular mRNAs, those with long 3'-untranslated regions (UTR) are selectively packaged. It seems plausible that the 3'-UTR, a stretch of RNA not occupied by ribosomes, offers a favorable binding site for Gag.

Physicochemical Study of Viral Nanoparticles at the Air/Water Interface.

The assembly of most single-stranded RNA (ssRNA) viruses into icosahedral nucleocapsids is a spontaneous process driven by protein-protein and RNA-protein interactions. The precise nature of these interactions results in the assembly of extremely monodisperse and structurally indistinguishable nucleocapsids. In this work, by using a ssRNA plant virus (cowpea chlorotic mottle virus [CCMV]) as a charged nanoparticle we show that the diffusion of these nanoparticles from the bulk solution to the air/water interface is an irreversible adsorption process. By using the Langmuir technique, we measured the diffusion and adsorption of viral nucleocapsids at the air/water interface at different pH conditions. The pH changes, and therefore in the net surface charge of the virions, have a great influence in the diffusion rate from the bulk solution to the air/water interface. Moreover, assembly of mesoscopic and microscopic viral aggregates at this interface depends on the net surface charge of the virions and the surface pressure. By using Brewster's angle microscopy we characterized these structures at the interface. Most common structures observed were clusters of virions and soap-frothlike micron-size structures. Furthermore, the CCMV films were compressed to form monolayers and multilayers from moderate to high surface pressures, respectively. After transferring the films from the air/water interface onto mica by using the Langmuir-Blodgett technique, their morphology was characterized by atomic force microscopy. These viral monolayers showed closed-packing nano- and microscopic arrangements.