Positive-sense Single-stranded RNA Research Articles

Dengue structural proteins as antiviral drug targets: Current status in the drug discovery & development.

Dengue virus belongs to the class of RNA viruses and subclass of enveloped single-stranded positive-sense RNA virus. It causes dengue fever (DF), dengue hemorrhagic fever (DHF), or dengue shock syndrome (DSS), where DHF and DSS are life-threatening. Even though dengue is an age-old disease, it is still a mystery and continues to be a global threat. Numerous attempts have been carried out in the past few decades to eradicate the virus through vaccine and antiviral drugs, but still battle continues. In this review, the possible drug targets for discovery and development of potential antiviral drugs against structural proteins of dengue virus, the current development status of the antiviral drugs against dengue around the world, and challenges that need to be addressed to overcome the shortcomings in the process of drug discovery have been discussed.

Low Seroprevalence of Aichi Virus Infection in Taiwan.

Aichi virus (AiV) belongs to the genus Kobuvirus of the family Picornaviridae; it is a single-stranded positive-sense RNA virus without an envelope. AiV causes acute gastroenteritis, abdominal pain, nausea, vomiting, and fever. Low incidence and high seroprevalence of AiV infections have been reported in several regions of the world; however, little was known on the prevalence of AiV infections in Taiwan. This study described the first two cases of AiV infection and analyzed AiV seroprevalence in Taiwan. A total of 700 sera were collected from a single hospital in southern Taiwan. The neutralization assay was employed to assess AiV neutralization antibodies in the serum. The test identified 48 positive cases, with a seroprevalence of 6.86%. Results also showed a gradual increase in AiV seroprevalence rate with age. Compared with other countries, Taiwan had a relatively low AiV seroprevalence, suggesting a low incidence of or sporadic AiV infections.

Japanese B Encephalitis.

RNA viruses are not only reported for viral pandemics but also as important agents for emerging/re-emerging diseases. Japanese encephalitis virus (JEV) is reported to cause epidemics of encephalitis in Southeast Asia, India, Korea, China, and Indonesia. In addition, several reports show that JEV has spread to new populations beyond these geographical regions. The disease mostly affects children with a mortality rate up to 30%. In peridomestic settings, pigs are reported as amplifiers of JEV transmission and aquatic birds as maintenance hosts of the virus. The Culex mosquito is the vector for transmission of JEV. This virus is a member of the family Flaviviridae and has a single-stranded positive-sense RNA virus. Five different genotypes (G-I to G-V) of JEV have been reported. Four different kinds of vaccines have been produced to prevent JEV infection. However, there is no FDA-approved antiviral drug available for JEV.How to cite this article: Mehta A, Singh R, Mani VE, Poddar B. Japanese B Encephalitis. Indian J Crit Care Med 2021;25(Suppl 2):S171–S174.

The Function of the PRRSV-Host Interactions and Their Effects on Viral Replication and Propagation in Antiviral Strategies.

Porcine reproductive and respiratory syndrome virus (PRRSV) affects the global swine industry and causes disastrous economic losses each year. The genome of PRRSV is an enveloped single-stranded positive-sense RNA of approximately 15 kb. The PRRSV replicates primarily in alveolar macrophages of pig lungs and lymphatic organs and causes reproductive problems in sows and respiratory symptoms in piglets. To date, studies on how PRRSV survives in the host, the host immune response against viral infections, and pathogenesis, have been reported. PRRSV vaccines have been developed, including inactive virus, modified live virus, attenuated live vaccine, DNA vaccine, and immune adjuvant vaccines. However, there are certain problems with the durability and effectiveness of the licensed vaccines. Moreover, the high variability and fast-evolving populations of this RNA virus challenge the design of PRRSV vaccines, and thus effective vaccines against PRRSV have not been developed successfully. As is well known, viruses interact with the host to escape the host’s immune response and then replicate and propagate in the host, which is the key to virus survival. Here, we review the complex network and the mechanism of PRRSV–host interactions in the processes of virus infection. It is critical to develop novel antiviral strategies against PRRSV by studying these host–virus interactions and structures to better understand the molecular mechanisms of PRRSV immune escape.

Wirus SARS-CoV-2: pochodzenie, budowa i cykl replikacyjny

In December 2019, a novel highly pathogenic coronavirus SARS-CoV-2, which can be transmitted from person to person, was discovered in patients with infectious respiratory disease in Wuhan, Hubei Province, China. The disease, now known as the 2019 coronavirus disease (COVID-19), has spread rapidly around the world causing a pandemic. This survey presents basic information on the structure and replication cycle of SARS-CoV-2. Fundamental discoveries in genetics and molecular biology of the virus paved the way to design and development of molecules that would act as potential therapeutic agents for COVID-19. The virus belongs to the β-coronavirus 2B lineage. Comparison of the SARS-CoV-2 genome sequence and other available β-coronavirus genomes suggests that it may have evolved naturally from the RaTG13 bat strain of coronaviruses. The virus has a positivesense single-stranded RNA that acts as mRNA following cellular entry and is completely dependent on the translation machinery of the host cell. The genomic RNA of SARS-CoV-2 comprises 14 open reading frames (ORFs). Two main ORFs, ORF1a and ORF1b, encompass two-thirds of the genome and are translated to polyproteins pp1a and pp1ab, respectively. These polyproteins are processed by viral proteases (papain-like protease and chymotrypsin-like protease), to produce 16 nonstructural proteins (Nsp). The remaining one-third of the genome encodes four major structural proteins: Spike (S), membrane (M), envelope (E) and nucleocapsid (N), and seven accessory proteins. SARS-CoV-2 infects human cells by binding to its receptor, i.e. angiotensin converting enzyme 2 (ACE2) at the cell surface through the receptor binding domain of its S protein. Following the entry into the host cell, the genetic material is released into the cytoplasm, and the synthesis of viral proteins necessary for the further process of replication and translation takes place. After mature virus particles are formed, they travel in Golgi vesicles to the host cell membrane where they are released into extracellular space by exocytosis. With the continued spread of SARS-CoV-2 around the world, thousands of mutations have been identified, some of which have relatively high incidences. The following proteins exhibited the highest mutation density: N, S, Nsp2, Nsp3, Nsp5, Nsp6, Nsp7, Nsp12, Nsp13, Orf3 and Orf8. The changes in SARS-CoV-2 proteins caused by mutations can not only affect virus transmission, pathogenesis, and immunogenicity, but also give rise to false negative diagnoses and drug resistance. © 2021 Polish Pharmaceutical Society. All rights reserved.

Carbon-Based Nanomaterials: Promising Antiviral Agents to Combat COVID-19 in the Microbial-Resistant Era.

Therapeutic options for the highly pathogenic human severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing the current pandemic coronavirus disease (COVID-19) are urgently needed. COVID-19 is associated with viral pneumonia and acute respiratory distress syndrome causing significant morbidity and mortality. The proposed treatments for COVID-19 have shown little or no effect in the clinic so far. Additionally, bacterial and fungal pathogens contribute to the SARS-CoV-2-mediated pneumonia disease complex. The antibiotic resistance in pneumonia treatment is increasing at an alarming rate. Therefore, carbon-based nanomaterials (CBNs), such as fullerene, carbon dots, graphene, and their derivatives constitute a promising alternative due to their wide-spectrum antimicrobial activity, biocompatibility, biodegradability, and capacity to induce tissue regeneration. Furthermore, the antimicrobial mode of action is mainly physical (e.g., membrane distortion), characterized by a low risk of antimicrobial resistance. In this Review, we evaluated the literature on the antiviral activity and broad-spectrum antimicrobial properties of CBNs. CBNs had antiviral activity against 13 enveloped positive-sense single-stranded RNA viruses, including SARS-CoV-2. CBNs with low or no toxicity to humans are promising therapeutics against the COVID-19 pneumonia complex with other viruses, bacteria, and fungi, including those that are multidrug-resistant.

Choice of assemblers has a critical impact on de novo assembly of SARS-CoV-2 genome and characterizing variants.

BackgroundCoronavirus Disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global pandemic following its initial emergence in China. SARS-CoV-2 has a positive-sense single-stranded RNA virus genome of around 30Kb. Using next-generation sequencing technologies, a large number of SARS-CoV-2 genomes are being sequenced at an unprecedented rate and being deposited in public repositories. For the de novo assembly of the SARS-CoV-2 genomes, a myriad of assemblers is being used, although their impact on the assembly quality has not been characterized for this virus. In this study, we aim to understand the variabilities on assembly qualities due to the choice of the assemblers.ResultsWe performed 6648 de novo assemblies of 416 SARS-CoV-2 samples using eight different assemblers with different k-mer lengths. We used Illumina paired-end sequencing reads and compared the assembly quality of those assemblers. We showed that the choice of assembler plays a significant role in reconstructing the SARS-CoV-2 genome. Two metagenomic assemblers, e.g. MEGAHIT and metaSPAdes, performed better compared with others in most of the assembly quality metrics including, recovery of a larger fraction of the genome, constructing larger contigs and higher N50, NA50 values, etc. We showed that at least 09% (259/2873) of the variants present in the assemblies between MEGAHIT and metaSPAdes are unique to one of the assembly methods.ConclusionOur analyses indicate the critical role of assembly methods for assembling SARS-CoV-2 genome using short reads and their impact on variant characterization. This study could help guide future studies to determine the best-suited assembler for the de novo assembly of virus genomes.

A Rapid and Sensitive Reverse Transcription-Loop-Mediated Isothermal Amplification (RT-LAMP) Assay for the Detection of Indian Citrus Ringspot Virus.

Indian citrus ringspot virus (ICRSV) is a devastating pathogen that has a particularly deleterious effect on the 'Kinnow mandarin', a commercial citrus crop cultivated in the northwest of India. ICRSV belongs to the Mandarivirus genus within the family of Alphaflexiviridae and has a positive sense single-stranded RNA (ssRNA) genome consisting of six open reading frames (ORFs). Severe cases of ICRSV result in a significant reduction in both the yield and quality of crops. Consequently, there is an urgent need to develop methods to detect ICRSV in an accurate and timely manner. Current methods involve a two-step reverse transcription polymerase chain reaction (RT-PCR) that is time consuming. Here, we describe a novel, one-step reverse transcription loop-mediated isothermal amplification (RT-LAMP) method for the sensitive and rapid detection of ICRSV. To standardize the RT-LAMP assay, four different primers were designed and tested to target the coat protein gene of ICRSV. Amplification results were visualized by a color change after addition of SYBR Green I. The standardized RT-LAMP assay was highly specific and successfully detected all 35 ICRSV isolates tested from the Punjab and Haryana states of India. Furthermore, there was no cross-reaction with 17 isolates of five other citrus pathogens that are common in India. The ICRSV RT-LAMP assay developed in the present study is a simple, rapid, sensitive, specific technique. Moreover, the assay consists of only a single step and is more cost effective than existing methods. This is the first application of RT-LAMP for the detection of ICRSV. Our RT-LAMP assay is a powerful tool for the detection of ICRSV and will be particularly useful for large-scale indexing of field samples in diagnostic laboratories, in nurseries, and for quarantine applications.

An expanded class of histidine-accepting viral tRNA-like structures.

Structured RNA elements are common in the genomes of RNA viruses, often playing critical roles during viral infection. Some viral RNA elements use forms of tRNA mimicry, but the diverse ways this mimicry can be achieved are poorly understood. Histidine-accepting tRNA-like structures (TLSHis) are examples found at the 3′ termini of some positive-sense single-stranded RNA (+ssRNA) viruses where they interact with several host proteins, induce histidylation of the RNA genome, and facilitate processes important for infection, to include genome replication. As only five TLSHis examples had been reported, we explored the possible larger phylogenetic distribution and diversity of this TLS class using bioinformatic approaches. We identified many new examples of TLSHis, yielding a rigorous consensus sequence and secondary structure model that we validated by chemical probing of representative TLSHis RNAs. We confirmed new examples as authentic TLSHis by demonstrating their ability to be histidylated in vitro, then used mutational analyses to imply a tertiary interaction that is likely analogous to the D- and T-loop interaction found in canonical tRNAs. These results expand our understanding of how diverse RNA sequences achieve tRNA-like structure and function in the context of viral RNA genomes and lay the groundwork for high-resolution structural studies of tRNA mimicry by histidine-accepting TLSs.

A review of novel coronavirus disease (COVID-19): based on genomic structure, phylogeny, current shreds of evidence, candidate vaccines, and drug repurposing.

Coronavirus disease (COVID-19) pandemic is instigated by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). As of March 13, 2021, more than 118.9 million cases were infected with COVID-19 worldwide. SARS-CoV-2 is a positive-sense single-stranded RNA beta-CoV. Most COVID-19 infected individuals recover within 1–3 weeks. Nevertheless, approximately 5% of patients develop acute respiratory distress syndrome and other systemic complications, leading to death. Structural genetic analyses of SARS-CoV-2 have shown genomic resemblances but a low evolutionary correlation to SARS-CoV-1 responsible for the 2002–2004 outbreak. The S glycoprotein is critical for cell adhesion and the entrance of the virus into the host. The process of cell entry uses the cellular receptor named angiotensin-converting enzyme 2. Recent evidence proposed that the CD147 as a SARS-CoV-2′s potential receptor. The viral genome is mainly held by two non-structural proteins (NSPs), ORF1a and ORF1ab, along with structural proteins. Although NSPs are conserved among the βCoVs, mutations in NSP2 and NSP3 may play critical roles in transmitting the virus and cell tropism. To date, no specific/targeted anti-viral treatments exist. Notably, more than 50 COVID-19 candidate vaccines in clinical trials, and a few being administered. Preventive precautions are the primary strategy to limit the viral load transmission and spread, emphasizing the urgent need for developing significant drug targets and vaccines against COVID-19. This review provides a cumulative overview of the genomic structure, transmission, phylogeny of SARS-CoV-2 from Indian clusters, treatment options, updated discoveries, and future standpoints for COVID-19.Supplementary InformationThe online version contains supplementary material available at 10.1007/s13205-021-02749-0.

Enhancement of Antimicrobial Activity of Alginate Films with a Low Amount of Carbon Nanofibers (0.1% w/w)

The World Health Organization has called for new effective and affordable alternative antimicrobial materials for the prevention and treatment of microbial infections. In this regard, calcium alginate has previously been shown to possess antiviral activity against the enveloped double-stranded DNA herpes simplex virus type 1. However, non-enveloped viruses are more resistant to inactivation than enveloped ones. Thus, the viral inhibition capacity of calcium alginate and the effect of adding a low amount of carbon nanofibers (0.1% w/w) were explored here against a non-enveloped double-stranded DNA virus model for the first time. The results of this study showed that neat calcium alginate films partly inactivated this type of non-enveloped virus and that including that extremely low percentage of carbon nanofibers (CNFs) significantly enhanced its antiviral activity. These calcium alginate/CNFs composite materials also showed antibacterial properties against the Gram-positive Staphylococcus aureus bacterial model and no cytotoxic effects in human keratinocyte HaCaT cells. Since alginate-based materials have also shown antiviral activity against four types of enveloped positive-sense single-stranded RNA viruses similar to SARS-CoV-2 in previous studies, these novel calcium alginate/carbon nanofibers composites are promising as broad-spectrum antimicrobial biomaterials for the current COVID-19 pandemic.

Structural biology of coronavirus ion channels

Viral infection compromises specific organelles of the cell and readdresses its functional resources to satisfy the needs of the invading body. Around 70% of the coronavirus positive-sense single-stranded RNA encodes proteins involved in replication, and these viruses essentially take over the biosynthetic and transport mechanisms to ensure the efficient replication of their genome and trafficking of their virions. Some coronaviruses encode genes for ion-channel proteins - the envelope protein E (orf4a), orf3a and orf8 - which they successfully employ to take control of the endoplasmic reticulum-Golgi complex intermediate compartment or ERGIC. The E protein, which is one of the four structural proteins of SARS-CoV-2 and other coronaviruses, assembles its transmembrane protomers into homopentameric channels with mild cationic selectivity. Orf3a forms homodimers and homotetramers. Both carry a PDZ-binding domain, lending them the versatility to interact with more than 400 target proteins in infected host cells. Orf8 is a very short 29-amino-acid single-passage transmembrane peptide that forms cation-selective channels when assembled in lipid bilayers. This review addresses the contribution of biophysical and structural biology approaches that unravel different facets of coronavirus ion channels, their effects on the cellular machinery of infected cells and some structure-functional correlations with ion channels of higher organisms.

Brief Facts about COVID-19 (SARS-CoV-2)

Coronaviruses are a group of related viruses that cause diseases in mammals and birds. In humans, coronaviruses cause respiratory tract infections that can range from mild to lethal. Mild illnesses include some cases of the common cold, while more lethal varieties can cause SARS, MERS, and COVID-19. The outbreak was identified in Wuhan, China, in December 2019, declared to be a Public Health Emergency of International Concern on 30 January 2020, and recognized as a pandemic on 11 March 2020. Coronaviruses are the subfamily Orthocoronavirinae, within the family of Coronaviridae, order Nidovirales, and realm Riboviria. They are enveloped viruses with a positive-sense single-stranded RNA genome and a nucleocapsid of helical symmetry. The genome size of coronaviruses is approximately from 26 to 32 kilobases. Coronaviruses were first discovered in the 1930s and Human coronaviruses were discovered in the 1960s. The earliest ones studied were from human patients with the common cold, which were later named human coronavirus 229E and human coronavirus OC43. Other human coronaviruses have since been identified, including SARS-CoV in 2003, HCoV NL63 in 2004, HKU1 in 2005, MERS-CoV in 2012, and SARS-CoV-2 in 2019. Most of these have involved serious respiratory tract infections

Broad-Spectrum Anti-coronavirus Vaccines and Therapeutics to Combat the Current COVID-19 Pandemic and Future Coronavirus Disease Outbreaks.

While the COVID-19 pandemic caused by SARS-CoV-2 is continuing, it may become worse in the coming winter months with a high potential for the emergence and spread of escape variants of SARS-CoV-2. SARS-related CoVs (SARSr-CoVs) from bats may also cause outbreaks of emerging coronavirus diseases in the future. These predictions call for the development of broad-spectrum anti-coronavirus vaccines and therapeutics to combat the current COVID-19 pandemic and future emerging coronavirus disease epidemics. In this review, we describe advances and challenges in the development of broad-spectrum vaccines and neutralizing antibodies against lineage B betacoronaviruses (β-CoV-Bs), including SARS-CoV-2, SARS-CoV, and SARSr-CoVs, as well as peptide-based pan-CoV fusion inhibitors and their potential in the prevention and treatment of COVID-19 and other human coronavirus infections.

Inflammation, immunity and potential target therapy of SARS-COV-2: A total scale analysis review

Coronavirus disease-19 (COVID-19) is a complex disease that causes illness ranging from mild to severe respiratory problems. It is caused by a novel coronavirus SARS-CoV-2 (Severe acute respiratory syndrome coronavirus-2) that is an enveloped positive-sense single-stranded RNA (+ssRNA) virus belongs to coronavirus CoV family. It has a fast-spreading potential worldwide, which leads to high mortality regardless of lows death rates. Now some vaccines or a specific drug are approved but not available for every country for disease prevention and/or treatment. Therefore, it is a high demand to identify the known drugs and test them as a possible therapeutic approach. In this critical situation, one or more of these drugs may represent the only option to treat or reduce the severity of the disease, until some specific drugs or vaccines will be developed and/or approved for everyone in this pandemic. In this updated review, the available repurpose immunotherapeutic treatment strategies are highlighted, elucidating the crosstalk between the immune system and SARS-CoV-2. Despite the reasonable data availability, the effectiveness and safety of these drugs against SARS-CoV-2 needs further studies and validations aiming for a better clinical outcome.

Coronavirus (SARS-CoV-2) in gastroenterology and its current epidemiological situation: An updated review until January 2021.

Coronaviruses are positive-sense single-strand RNA viruses that infect amphibians, birds, and mammals. Coronavirus Disease 2019 (COVID-19) has become a major health problem caused by one of the coronaviruses called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It has spread fast throughout the globe since its first identification in Wuhan, China, in December 2019. Although COVID-19 is principally defined by its respiratory symptoms, it is now clear that the virus can also affect the digestive system causing gastrointestinal (GI) symptoms like diarrhea, loss of appetite, nausea/vomiting, and abdominal pain as a major complaint. GI symptoms could be the initial signs of preceding respiratory signs, carrying a potential for slowed investigation and raised disease transmission opportunities. Various studies recognized the COVID-19 RNA in stool specimens of infected patients, and its viral receptor angiotensin-converting enzyme-2 (ACE-2) is highly expressed in GI epithelial cells. Many cases were reported negative using nasopharyngeal/oropharyngeal swabs and finally, SARS‐CoV‐2 RNA was detected in their anal/rectal swabs and stool specimens. These suggest that COVID-19 can actively infect and replicate in the GI tract. In this review, we elaborate on the close relationship between SARS-CoV-2 and the digestive system, focusing on the current status in the field of COVID-19 in gastroenterology, liver injury, endoscopy, inflammatory bowel disease, imaging, and the potential underlying mechanisms with illustrating the current epidemiological status regarding this pandemic.

Current understanding of the impact of COVID-19 on gastrointestinal disease: Challenges and openings.

The novel coronavirus disease-2019 (COVID-19) is caused by a positive-sense single-stranded RNA virus which belongs to the Coronaviridae family. In March 2019 the World Health Organization declared that COVID-19 was a pandemic. COVID-19 patients typically have a fever, dry cough, dyspnea, fatigue, and anosmia. Some patients also report gastrointestinal (GI) symptoms, including diarrhea, nausea, vomiting, and abdominal pain, as well as liver enzyme abnormalities. Surprisingly, many studies have found severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral RNA in rectal swabs and stool specimens of asymptomatic COVID-19 patients. In addition, viral receptor angiotensin-converting enzyme 2 and transmembrane protease serine-type 2, were also found to be highly expressed in gastrointestinal epithelial cells of the intestinal mucosa. Furthermore, SARS-CoV-2 can dynamically infect and replicate in both GI and liver cells. Taken together these results indicate that the GI tract is a potential target of SARS-CoV-2. Therefore, the present review summarizes the vital information available to date on COVID-19 and its impact on GI aspects.

Revealing Tissue-Specific SARS-CoV-2 Infection and Host Responses using Human Stem Cell-Derived Lung and Cerebral Organoids.

SummaryCOVID-19 is a transmissible respiratory disease caused by a novel coronavirus, SARS-CoV-2, and has become a global health emergency. There is an urgent need for robust and practical in vitro model systems to investigate viral pathogenesis. Here, we generated human induced pluripotent stem cell (iPSC)-derived lung organoids (LORGs), cerebral organoids (CORGs), neural progenitor cells (NPCs), neurons, and astrocytes. LORGs containing epithelial cells, alveolar types 1 and 2, highly express ACE2 and TMPRSS2 and are permissive to SARS-CoV-2 infection. SARS-CoV-2 infection induces interferons, cytokines, and chemokines and activates critical inflammasome pathway genes. Spike protein inhibitor, EK1 peptide, and TMPRSS2 inhibitors (camostat/nafamostat) block viral entry in LORGs. Conversely, CORGs, NPCs, astrocytes, and neurons express low levels of ACE2 and TMPRSS2 and correspondingly are not highly permissive to SARS-CoV-2 infection. Infection in neuronal cells activates TLR3/7, OAS2, complement system, and apoptotic genes. These findings will aid in understanding COVID-19 pathogenesis and facilitate drug discovery.

Advances in Hepatitis E Virus Biology and Pathogenesis.

Hepatitis E virus (HEV) is one of the causative agents for liver inflammation across the world. HEV is a positive-sense single-stranded RNA virus. Human HEV strains mainly belong to four major genotypes in the genus Orthohepevirus A, family Hepeviridae. Among the four genotypes, genotype 1 and 2 are obligate human pathogens, and genotype 3 and 4 cause zoonotic infections. HEV infection with genotype 1 and 2 mainly presents as acute and self-limiting hepatitis in young adults. However, HEV infection of pregnant women with genotype 1 strains can be exacerbated to fulminant hepatitis, resulting in a high rate of case fatality. As pregnant women maintain the balance of maternal-fetal tolerance and effective immunity against invading pathogens, HEV infection with genotype 1 might dysregulate the balance and cause the adverse outcome. Furthermore, HEV infection with genotype 3 can be chronic in immunocompromised patients, with rapid progression, which has been a challenge since it was reported years ago. The virus has a complex interaction with the host cells in downregulating antiviral factors and recruiting elements to generate a conducive environment of replication. The virus-cell interactions at an early stage might determine the consequence of the infection. In this review, advances in HEV virology, viral life cycle, viral interference with the immune response, and the pathogenesis in pregnant women are discussed, and perspectives on these aspects are presented.

Cluster Analysis of Coronavirus Sequences using Computational Sequence Descriptors: With Applications to SARS, MERS and SARS-CoV-2 (CoVID-19).

Coronaviruses comprise a group of enveloped, positive-sense single-stranded RNA viruses that infect humans as well as a wide range of animals. The study was performed on a set of 573 sequences belonging to SARS, MERS and SARS-CoV-2 (CoVID-19) viruses. The sequences were represented with alignment-free sequence descriptors and analyzed with different chemometric methods: Euclidean/Mahalanobis distances, principal component analysis and self-organizing maps (Kohonen networks). We report the cluster structures of the data. The sequences are well-clustered regarding the type of virus; however, some of them show the tendency to belong to more than one virus type. This is a study of 573 genome sequences belonging to SARS, MERS and SARS-- CoV-2 (CoVID-19) coronaviruses. The aim was to compare the virus sequences, which originate from different places around the world. The study used alignment free sequence descriptors for the representation of sequences and chemometric methods for analyzing clusters. Majority of genome sequences are clustered with respect to the virus type, but some of them are outliers. We indicate 71 sequences, which tend to belong to more than one cluster.