Acta virologica最新文献

Missense mutations in the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus may cause changes in the structure of proteins. The nucleocapsid (N) protein is an important target for drugs and vaccines. The main purpose of this study is to detect missense mutations in the SARS-CoV-2 N protein and to reveal the effects of these mutations on protein structure by using in silico approaches. 161 missense mutations of the N protein were determined in 2286 SARS-CoV-2 genomes derived from the GISAID EpiCoV database in the Turkish population. Identified 161 missense mutations were analyzed by using sequence and structure-based methods to predict effects of mutation on function and structure of SARS-CoV-2 N protein. These analyzes revealed that some mutations showed deleterious effects and change of stability and flexibility of nucleocapsid protein. D3L, S194L, S235F, and P13L (Omicron variant) mutations were further analyzed in our study due to their importance in the literature and in our results. Even though, our findings are essential for research of SARS-CoV-2 virus, in vitro and in vivo validations are necessary. Keywords: nucleocapsid protein; SARS-CoV-2; missense mutations; protein stability; protein flexibility.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) monitoring in air traffic is important in the prevention of the virus spreading from abroad. The gold standard for SARS-CoV-2 detection is RT-qPCR; however, for early and low viral load detection, a much more sensitive method, such as droplet digital PCR (ddPCR), is required. Our first step was to developed both, ddPCR and RT-qPCR methods, for sensitive SARS-CoV-2 detection. Analysis of ten swab/saliva samples of five Covid-19 patients in different stages of disease showed positivity in 6/10 samples with RT-qPCR and 9/10 with ddPCR. We also used our RT-qPCR method for SARS-CoV-2 detection without the need of RNA extraction, obtaining results in 90-120 minutes. We analyzed 116 self-collected saliva samples from passengers and airport staff arriving from abroad. All samples were negative by RT-qPCR, while 1 was positive, using ddPCR. Lastly, we developed ddPCR assays for SARS-CoV-2 variants identification (alpha, beta, gamma, delta/kappa) that are more economically advantageous when compared to NGS. Our findings demonstrated that saliva samples can be stored at ambient temperature, as we did not observe any significant difference between a fresh sample and the same sample after 24 hours (p = 0.23), hence, saliva collection is the optimal route for sampling airplane passengers. Our results also showed that droplet digital PCR is a more suitable method for detecting virus from saliva, compared to RT-qPCR. Keywords: COVID-19; RT-PCR; ddPCR; SARS-CoV-2; nasopharyngeal swab; saliva.

Since the emergence of the original Wuhan SARS-CoV-2 strain, several new variants of the virus have emerged. Alpha, Beta, Gamma, Delta and the most recent Omicron variants have been introduced during this pandemic. Several methods including, but not restricted to, allele-specific PCR, ligation with rolling circle amplification and real-time PCR with allele-specific probes are able to detect mutations as low as a single nucleotide polymorphism. High-resolution melting curve analysis is ano-ther technique to assess any mutations in a nucleic acid chain. Confirmed samples with SARS-CoV-2 infection were subjected to variant identification using a de novo-designed HRM assay. In order to select for mutations with the highest effect on Tm of the amplicon, deletion mutations of NSP6 (Del 3675-3677), and S1 (Del 144) were chosen for HRM analysis. HRM analysis for the amplicon of the primer set-1 (NSP6) resulted in Tm differences of -0.39°C, +0.4°C, and -0.6°C between Alpha, Delta, and Omicron variants, respectively, in comparison to the original Wuhan strain. Moreover, HRM analysis of the amplification performed by primer set-2 (S1) led to Tm differences of +0.32°C, -0.26°C, and +0.24°C between Alpha, Delta, and Omicron variants, respectively, in comparison to original Wuhan strain. The test was able to specify each sample to its variant group with more than 90 percent of confidence. The results obtained in this study demonstrate that using a single closed-tube strategy with a HRM-equipped machine, screening new variants of the virus is possible in a fast and reliable way. Keywords: high resolution melting; SARS coronavirus 2; mutation; variant; genotyping.

Porcine reproductive and respiratory syndrome (PRRS) caused by PRRS virus (PRRSV) is one of the most complicated and dangerous diseases in pigs with high mortality since it modulates the immune system of the lungs and has been closely associated with secondary infection of other lethal bacteria and viruses. The gold standard of molecular diagnosis for PRRSV, reverse transcription (RT)-PCR, is time-consuming, expensive and requires transportation of samples to a specialized laboratory. In this study, a direct colorimetric RT-loop-mediated isothermal amplification (RT-LAMP) method was developed to specifically and rapidly detect PRRSV. The RT-LAMP outcomes can be visualized by the naked eye after 45 min of incubation at 65˚C without any cross-reactivity recorded with the bacteria and other viruses tested. In particular, the mobile, non-instrumented, commercial pocket hand warmers were demonstrated to su-ccessfully provide constant temperature for consistent nucleic acid amplification throughout the RT-LAMP reactions. The limit of detection of the assay was defined as the genomic RNA concentration extracted from a known viral titer of 10-2.5 TCID50/ml. The direct use of clinical serum samples required a simple dilution to maintain the performance of the colorimetric RT-LAMP assay. Therefore, the direct colorimetric RT-LAMP assay developed is well-qualified for producing a ready-to-use kit for PRRSV diagnosis in the field. Keywords: porcine reproductive and respiratory syndrome; rapid testing; RT-LAMP; colorimetric; direct detection; instrument-free.

Noroviruses (NoV) are enteric caliciviruses that have been detected in multiple species of mammals, including humans. Establishing an efficient in vitro cell culture system for human norovirus (HuNoV) remains a challenge; however, its replication has been reported in 3D cultured Caco-2 cells and a clone of Caco-2 cells (C2BBe1), human enteroids and human B cells. Isolated mouse intestinal villi, with large diversity of intestinal epithelial cells, are a primary cellular model that has been shown to be permissive for the infection and replication of enteric viruses such as rotaviruses. We hypothesized that they could allow the infection and replication of the human noroviruses. In this report, we indicate that the isolated villi model of the mouse intestine is effective for the infection study and replication of the human noroviruses from faeces and environmental matrices (water, vegetables and air). For successful infection, the virus needs to be activated with trypsin. The virus has an average replicative cycle of 10 h, although viral particles with infectious capacity are found already at 2 hours post infection (2 h.p.i.). The model is efficient in obtaining abundant biological material and is ideal for studying the biological activity of the human noroviruses in the same cell model or for generating antibodies. Keywords: human norovirus; intestinal epithelial cells; intestinal villus isolation; norovirus isolated from water; norovirus isolated from plants; norovirus isolated from air.

High-throughput RNA sequencing (RNA-seq) analysis of samples from Mallotus japonicus, a traditional medicinal plant, yielded two novel RNA viruses tentatively named Mallotus japonicus virus A (MjVA) and Mallotus japonicus virus B (MjVB). The MjVA and MjVB genomes encode proteins showing amino acid sequence similarities to those of poleroviruses (the genus Polerovirus, the family Solemoviridae) and amalgaviruses (the genus Amalgavirus, the family Amalgaviridae), respectively. The MjVA genome contains seven highly overlapping open reading frames, which are translated to seven proteins through various translational mechanisms, including -1 programmed ribosomal frameshifting (PRF) at the slippery motif GGGAAAC, non-AUG translational initiation, and stop codon readthrough. The MjVB genome encodes two proteins; one of which is translated by +1 PRF mechanism at the slippery motif UUUCGN. The abundance analysis of virus-derived RNA fragments revealed that MjVA is highly concentrated in plant parts with well-developed phloem tissues as previously demonstrated in other poleroviruses, which are transmitted by phloem feeders, such as aphids. MjVB, an amalgavirus generally transmitted by seeds, is distributed in all samples at low concentrations. Thus, this study demonstrates the effectiveness and usefulness of RNA-seq analysis of plant samples for the identification of novel RNA viruses and analysis of their tissue distribution. Keywords: Polerovirus; Amalgavirus; Mallotus japonicus; RNA virus; viral genome; programmed ribosomal frameshifting.

The major protective immune response against viruses is the production of type I and III interferons (IFNs). IFNs induce the expression of hundreds of IFN-stimulated genes (ISGs) that block viral replication and further viral spread. In this report, we analyzed the expression of IFNs and some ISGs (MxA, PKR, OAS-1, IFIT-1, RIG-1, MDA5, SOCS-1) in alveolar epithelial cells (A549) in response to infection with influenza A viruses (A/California/07/09 (H1N1pdm); A/Texas/50/12 (H3N2)); influenza B virus (B/Phuket/3073/13); adenovirus type 5 and 6; or respiratory syncytial virus (strain A2). Influenza B virus had the ability to most rapidly induce IFNs and ISGs as well as to stimulate excessive IFN-α, IFN-β and IFN-λ secretion. It seems curious that IAV H1N1pdm did not induce IFN-λ secretion, but enhanced type I IFN and interleukin (IL)-6 production. We emphasized the importance of the negative regulation of virus-triggered signaling and cellular IFN response. We showed a decrease in IFNLR1 mRNA in the case of IBV infection. The attenuation of SOCS-1 expression in IAV H1N1pdm can be considered as the inability of the system to restore the immune status. Presumably, the lack of negative feedback loop regulation of proinflammatory immune response may be a factor contributing to the particular pathogenicity of several strains of influenza. Keywords: lambda interferons; MxA; influenza; respiratory syncytial virus; A549 cells.

Equine herpesvirus 1 (EHV1) infection is a global health problem in equines and the virus is responsible for abortions, respiratory disease and myeloencephalitis in horses. Disease management requires proper biosecurity and immunoprophylactic measures. Vaccines strengthening both arms of immunity are essential for proper control and there has been a continuous focus in this area for generation of better vaccines. Here we report construction of bacterial artificial chromosome (BAC) clone of EHV-1 strain Tohana for mutagenesis of the virus and generation of gE gene deletion mutant EHV1. The BAC clone was generated by inserting the mini-F plasmid replacing ORF71 of EHV1 and transforming into E. coli for generation of EHV1-BAC. The infectious virus was regenerated from EHV-1 BAC DNA in RK13 cells. To check utility of EHV1-BAC, we have generated mutant EHV1 by deleting the virulence-associated gE gene. The mutant virus (vToHΔgE) showed significantly reduced plaque size without affecting replication efficiency. Pathological evaluation of lesions in BALB/c mice infected with vToHΔgE revealed reduction in clinical signs and pathology in comparison to the wild-type virus. Generation of infectious BAC of EHV1 and its usage in construction of attenuated viruses shows potential of the technology for development of indigenous modified live vaccine for EHV1. Keywords: quine herpesvirus 1; bacterial artificial chromosome (BAC); mutation; glycoprotein E; vaccine.

Parvoviruses affect both vertebrates and invertebrates, and can be both detrimental and benign to the host. Numerous studies about parvovirus-induced apoptotic cell death have been researched and reported. In most parvovirus infections, cell death heightens the virus dissemination and causes tissue damage, often leading to disease. Cell cycle arrest also induces cytopathic effects in infected cells and is sometimes a prerequisite to apoptotic cell death. Cell death mechanisms caused by parvovirus infections vary depending on the infecting parvovirus strain and the cell lines involved. Apo-ptosis, however, is a frequent form of cell death induced by parvoviruses. The non-structural protein 1 (NS1) is a major contributor to parvovirus infection-induced cell death. However, other proteins such as the 11 kDa, NP1 and viral genome replication can also induce cell death. Understanding the mechanisms involved in parvovirus cell death, and host response is important in the development of treatment for cytopathic parvoviruses. This review article discusses parvovirus-induced apoptotic cell death and the mechanisms involved. Keywords: apoptosis; cell cycle arrest; cell death; parvovirus; viral protein.