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Order Articulavirales
Published in Paul Pumpens, Peter Pushko, Philippe Le Mercier, Virus-Like Particles, 2022
Paul Pumpens, Peter Pushko, Philippe Le Mercier
These live virus strains are cold adapted, temperature sensitive, and attenuated so as not to produce influenza-like illness by limiting their replication to only the upper respiratory tract in humans. The reassortant strains developed by serial passage at sequentially lower temperatures acquire attenuated phenotypes because of multiple mutations in gene segments that encode viral internal proteins (Murphy and Coelingh 2002).
A Brief Introduction to Virology
Published in Rae-Ellen W. Kavey, Allison B. Kavey, Viral Pandemics, 2020
Rae-Ellen W. Kavey, Allison B. Kavey
The process of recombination identified by the Cold Springs Harbor team – two virus particles simultaneously infecting the same cell exchanging parts of their genetic material to produce new hybrid forms of the original viruses – was found to occur primarily in DNA viruses and was recognized as resulting in new viral strains which could infect previously resistant hosts, an important part of the infectivity of viruses. A particular form of recombination called “reassortment” occurred only in RNA viruses with segmented RNA, like the influenza virus. In this setting, whole segments of genetic material are exchanged, resulting in progeny with immediate and major antigenic change, a process called genetic shift.30 Based on findings like these, it was recognized that reassortment could yield an entirely new and antigenically novel virus strain. In the 30 minutes needed for a virus replication cycle, an infinitesimal killer virus could emerge, highly infectious, easily transmittable and lethal. It was molecular genetic work that identified this most important characteristic of RNA viruses: endless evolution by both spontaneous mutation and by genetic reassortment leading to continuous emergence of new, antigenically novel strains. Faced with an entirely new virus strain, human hosts have little if any resistance, so these emerging strains have high infectivity. This is especially true when reassortment occurs between an animal virus and a human virus.
Autoimmunity and Immune Pathological Aspects of Virus Disease
Published in Irun R. Cohen, Perspectives on Autoimmunity, 2020
H. Wege, R. Dörries, P. Massa, R. Watanabe
Clinical diseases caused by LCM virus are only rarely observed in humans. The infection is transmitted from mice or hamsters and may lead to typical lymphocytic choriomeningitis, to acute meningoencephalomyelitis, or to influenza-like syndromes. The majority of patients develop a benign course without further sequelae. It is not known if the disease in humans involves immune pathological mechanisms.2,89 LCM virions are composed of four structural proteins and contain a negative-stranded RNA genome made of two segments. Virus strains differ widely in their ability to induce acute and chronic diseases based on persistent infections of lymphocytes, hormone-producing cells, and neural cells. Analysis of reassortant viruses has recently helped to map different pathogenic properties of the genome.7,8,90
Next generation live-attenuated influenza vaccine platforms
Published in Expert Review of Vaccines, 2022
Despite the effective vaccines and antiviral drugs availability, influenza viruses pose a threat to public health worldwide. There were four influenza virus pandemics in the last ~100 years. The pandemics of 1918 (H1N1), 1957 (H2N2), 1968 (H3N2), and 2009 (H1N1) caused millions of human deaths. Annually, influenza viruses affect 5–15% of the human population and cause 290,000–650,000 deaths worldwide [5]. Novel influenza strains caused by zoonotic transmission and antigenic diversity pose an eminent threat to people with no or little preexisting immunity. Current vaccines provide protection against the seasonal outbreaks that are well-matched to circulating strains. These seasonal vaccines are updated annually due to the antigenic changes in the variable head HA region that lead to viral escape from immune responses. In addition, most of the population remains vulnerable to influenza virus outbreak that often results from the genetic reassortment of influenza virus strains.
The risk of a swine influenza pandemic: still a concern?
Published in Expert Review of Respiratory Medicine, 2019
Paul Loubet, Vincent Enouf, Odile Launay
The ecology of IAV is complex and involves a broad range of avian and mammalian host species. Influenza viruses have high mutation rates and are constantly changing, which enables the virus to quickly adapt to changes in the host environment, as is the case during interspecies transmission. The rapid evolution results from two mechanisms: reassortment and point mutations. Reassortment occurs when two different strains infect the same cell of a given host, allowing for the exchange of intact gene segments. When reassortment involves either the HA or NA segments, it is termed antigenic shift. Point mutations occur due to an error-prone polymerase devoid of a proof-reading and correction mechanism. When point mutations are fixed in the HA or NA segments it is called antigenic drift. Both of these mechanisms play pivotal roles in the emergence of novel influenza viruses that could jump the host barrier. Once the virus jumps into a new host, it must adapt and change to be able to spread and become established in the new population [2].
Influenza vaccine programs for children in low- and middle-income countries: current status and way forward
Published in Expert Review of Vaccines, 2019
Justin R Ortiz, Kathleen M Neuzil
Influenza viruses circulate globally, affect people of all ages, and cause annual disease outbreaks. Influenza A viruses undergo frequent antigenic mutations (antigenic drift) that allow them to evade immune protection and to cause repeated infections in an individual over a lifetime [13]. Novel virus strains may emerge through genetic reassortment between different strains in a common host (antigenic shift) [14]. Further, non-human strains may directly infect and cause disease in humans [15]. Reassortment events or direct infection of humans by animal viruses have the potential to cause a pandemic if humans have little to no pre-existing immunity to the virus, if person-to-person transmission is sustained, and the infection causes clinical disease [16]. An influenza pandemic could be catastrophic for human health and have major effects on the functioning of societies and economies [13].