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Morphology, Pathogenesis, Genome Organization, and Replication of Coronavirus (COVID-19)
Published in Hanadi Talal Ahmedah, Muhammad Riaz, Sagheer Ahmed, Marius Alexandru Moga, The Covid-19 Pandemic, 2023
Sadia Javed, Bahzad Ahmad Farhan, Maria Shabbir, Areeba Tahseen, Hanadi Talal Ahmedah, Marius Moga
The connection between asymptomatic exposure and pre-symptomatic exposure of virus events and their distribution is not quite well understood. The RT-PCR test will diagnose whether the virus can be identified, but this will not tell us whether or not someone is infected [36]. Virulence in cell culture is used to determine whether or not a patient has been infected to a viral strain. In the lack of virus sample data, RT-PCR data such as viral load or cyclical thresholds (Ct) parameters were used as a guideline for spread possibility. The Ct is the total number of cycles needed to pass a certain limit in an RT-PCR signal [30]. This variable is not proportional to the number of targeted viral genome sequences or viral sample loaded, particularly when virus levels are low, as indicated by higher Ct measurement. The virus was not successfully eliminated unless Ct was smaller than 24 among 90 infected persons with COVID-19 infection, according to Bullard and colleagues [38]. The connection among COVID-19 virus RNA elimination and the mode of transmission remains unknown. The percentage of symptomless or pre-symptomatic exposure of COVID-19 infection is not apparent when compared to symptomatic infection [39].
The Great Influenza
Published in Rae-Ellen W. Kavey, Allison B. Kavey, Viral Pandemics, 2020
Rae-Ellen W. Kavey, Allison B. Kavey
Recombination – the process of two virus particles infecting the same cell exchanging parts of their genetic material to produce new hybrid forms of the original viruses – was first described in 1936 and was subsequently found to occur primarily in DNA viruses; it was recognized as resulting in new viral strains which could infect previously resistant hosts. A particular form of recombination called “reassortment” was found to occur only in segmented RNA viruses, like the influenza virus. Whole segments of genetic material could be exchanged between viruses infecting the same cell, resulting in progeny with immediate and major antigenic change.46 Based on findings like these, it was recognized that the process of genetic information exchange by reassortment can occur between animal and human strains of a virus and can result in an entirely new and antigenically novel virus strain. In a single influenza virus replication cycle, a potential killer virus can emerge, highly infectious, easily transmittable and lethal. Endless evolution by both spontaneous mutation and by genetic reassortment results in the continuous emergence of new, antigenically novel influenza virus strains to which human hosts can have limited or no resistance.47 These findings provided powerful insight into the infectious potential of the influenza virus.
Human Influenza Virus Infections
Published in Sunit K. Singh, Human Respiratory Viral Infections, 2014
Judith M. Fontana, Daniel P. Eiras, Mirella Salvatore
There is currently no formal method to predict which influenza virus strain will circulate in the following season. A recent study has shown that there is a correlation between the early circulation of a strain of influenza virus and reduced total incidence of the other strains, which was suggested to be due to interference among strains.141 Another factor that influences the distribution of a particular influenza virus strain is the extent to which the human host has been able to develop an antibody response from prior exposures or vaccination. Once a strain has circulated in a susceptible population and sufficient immunity has developed, the strain’s propensity for epidemic spread and disease severity is diminished.142
Deciphering Vaccines for COVID-19: where do we stand today?
Published in Immunopharmacology and Immunotoxicology, 2021
Tushar Baviskar, Dezaree Raut, Lokesh Kumar Bhatt
The structure of the S protein of the SARS-CoV-2019 was deciphered in a very short time after the outbreak, thus enhancing the domain knowledge for identification of target for vaccine production [9,10]. The S glycoprotein of SARS-CoV-2 mediates entry of the virus into the host cell and is one of the most important antigenic determinants, making it a potential candidate for a vaccine [16]. Extensive mutations are discovered in the sequence of virus strain by comparative sequencing. A variety of MHC-Class I and II covering the world population were found as promising targets. T cell epitope-based vaccine targeting envelops protein E designed using the immunoinformatic approach and needs clinical validation and evaluation for safety [17]. Multiple such targets are identified as potential candidates for vaccine using computational studies. Around more than 60 projects are in progress for the development of the protein subunit vaccine. Most of these are in the pre-clinical phase [18]. Novavax registered a trial for the evaluation of a protein subunit vaccine. It is a Randomized, Phase 1/2, observer-blinded study for evaluation of the safety and immunogenicity of SARS-CoV-2 Recombinant Spike Protein Nanoparticle Vaccine (SARS-CoV-2 rS) with or without the use of MATRIX-M™ adjuvant in healthy subjects [19]. Anhui Zhifei Longcom Biologic Pharmacy Co., Ltd. is involved in the development of a subunit vaccine which is in phase 2 of a randomized, blinded, placebo-controlled trial [20]. Vaccine candidates from this category in the clinical trials are enlisted in Table 1.
The wide spectrum of Kawasaki-like disease associated with SARS-CoV-2 infection
Published in Expert Review of Clinical Immunology, 2020
Onorina Berardicurti, Alessandro Conforti, Piero Ruscitti, Paola Cipriani, Roberto Giacomelli
One of the main limitation of the included studies is the possibility of false-positivity and/or co-existence of more than one viral strain. Not SARS-CoV2 studies were not conducted during a pandemic spread, but on daily practice data. Some of assessed patients were retrieved during the possible viral offspring and some of them recruited patients over the years, without any regards on Coronaviruses seasonality. Only Esper et al. screened all the patients for respiratory syncytial virus, influenza viruses A and B, parainfluenza viruses, and adenoviruses [22]. In other reports, the possibility of other viral infections was not described. The reported prevalence of viral code detection (ie, detection of >1 virus per illness episode) was 4.8% in patients with acute respiratory infection, but not during a specific virus spread [63].
Research progress in the development of porcine reproductive and respiratory syndrome virus as a viral vector for foreign gene expression and delivery
Published in Expert Review of Vaccines, 2020
Guo Dai, Mei Huang, To Sing Fung, Ding Xiang Liu
Vaccines for PRRSV, including KV vaccines and MLV vaccines, are commercially available. These vaccines are usually generated based on a single virus strain. KV vaccines failed to induce detectable neutralizing antibodies and cell-mediated immune responses against PRRSV, while MLV vaccines are unable to offer adequate protection against heterologous strains. The problems of reversion to virulence and recombination between MLV vaccines and field strains have also been reported frequently. Furthermore, current MLV vaccines could not be distinguished from wild strains, making it difficult to establish a PRRS-free status regionally or in a country. The constant evolution of PRRSV not only leads to the emergence of new genetic and antigenic variants, but also results in numerous outbreaks of PRRS, posing tremendous challenges to the development of a new generation of safe and effective vaccines.