Order Asfuvirales
Paul Pumpens, Peter Pushko, Philippe Le Mercier in Virus-Like Particles, 2022
According to the present ICTV (2020) situation, the extremely small Asfuvirales order currently includes a sole family Asfarviridae with the sole genus Asfivirus involving the only recognized African swine fever virus species, well known because of its ecological and economical danger. The order Asfuvirales, together with the well-known Chitovirales order including the famous Poxviridae family, which is touched on briefly in Chapter 5, forms the class Pokkesviricetes. The latter, together with the class Megaviricetes, forms the Nucleocytoviricota phylum. The latter, together with the Preplasmiviricota phylum, forms the Bamfordvirae kingdom, while the latter, together with the kingdom Helvetiavirae, belongs in turn to the great realm Varidnaviria.
The role of apoptosis in non-mammalian host-parasite relationships
G. F. Wiegertjes, G. Flik in Host-Parasite Interactions, 2004
One group of host proteins is a particular target for viruses. Caspases are activated by a variety of ‘death signals’, pro-caspases being cleaved at specific aspartic acid residues resulting in the production of two subunits. These subunits, acting as a tetramer, carry out the protein cleavage, which produces the typical apoptotic morphological changes in target cells. Several viruses, e.g. African swine fever virus and poxvirus produce gene products that inhibit the function of caspases. For example in cowpox the product termed cytokine response modifier A (CRMA), which is a serpin-like molecule, inhibits several caspases, e.g. 3, 6 and 8 in mammals but, interestingly, it also blocks apoptosis caused by synthesis of reaper in Drosophilia (see Villa et al., 1997).
Host Defense and Parasite Evasion
Eric S. Loker, Bruce V. Hofkin in Parasitology, 2015
The ability to alter antigen presentation is certainly not limited to protozoa. A number of animal parasites are known to produce cystatins, a family of cysteine protease inhibitors with known immunoregulatory functions. Cystatins negatively affect MHC II presentation by inhibiting host proteases required for antigen processing. Brugia malayi is just one nematode that owes part of its success to cystatin production. Another example is the filarial nematode Onchocerca volvulus, in which infection is characterized by a significant lack of protective immunity. Part of the explanation lies in the secretion of a cystatin known as onchocystatin. And cystatins are not limited to nematodes. The soft tick Ornithodoros moubata, for instance, is an important vector for African swine fever virus and the spirochete Borrelia duttoni. The cystatin present in its saliva, OmC2, reduces the ability of dendritic cells at the bite site to present antigen and secrete inflammatory cytokines. This prevents the acquisition of immunity to tick feeding, and it permits more efficient transmission of the tick-borne pathogens. Yet the discovery of immunosuppressive parasite cystatins comes with a silver lining. It has been proposed, for instance, that OmC2 might make a good vaccine target to protect animals against both feeding ticks and the pathogens they transmit. Furthermore, because of their immunosuppressive activity, synthesized parasite cystatins might have value for the treatment of certain autoimmune diseases, such as rheumatoid arthritis, in which symptoms are caused by an aberrant immune response.
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
Another useful trait of a PRRSV-based recombinant vaccine would be the host cell-specificity of PRRSV. Similar to other known porcine viruses, such as porcine circovirus (PCV) and African swine fever virus (ASFV), PRRSV primarily infects immune cells of swine, particularly those involved in antigen presentation. PRRSV-based vector would deliver antigens from these pathogens to the similar tissues/cells as in the infected host, eliciting similar local and systematic immune responses and rendering optimal protection against diseases caused by these pathogens. As no effective vaccine currently available against ASFV infection, it would be particularly interesting to test if a PRRSV vectored vaccine expressing multiple protective antigens from ASFV would render protection against this devastating porcine disease.
How relevant are in vitro culture models for study of tick-pathogen interactions?
Published in Pathogens and Global Health, 2021
Cristiano Salata, Sara Moutailler, Houssam Attoui, Erich Zweygarth, Lygia Decker, Lesley Bell-Sakyi
Some arthropod genomes contain non-retroviral integrated RNA virus sequences (NIRVS) that are a substrate for the production of short RNAs involved in the response to viral infections. NIRVS originate by the integration of DNA derived from the retrotranscription of small regions of viral RNA genomes and may modulate the outcome of infection. In particular, ISE6 cells and I. scapularis ticks both contain many bunya- and orthomyxo-like NIRVS sequences, suggesting that ticks are a dominant host for these virus groups [101]. Furthermore, the genomes of OME/CTVM21 and other Ornithodoros moubata cell lines, as well as some populations of O. moubata ticks, harbor African swine fever virus (ASFV)-like integrated elements that may interfere with ASFV infection [102].
CRISPR-cas systems based molecular diagnostic tool for infectious diseases and emerging 2019 novel coronavirus (COVID-19) pneumonia
Published in Journal of Drug Targeting, 2020
Xiaohong Xiang, Keli Qian, Zhen Zhang, Fengyun Lin, Yang Xie, Yang Liu, Zongfa Yang
Identification of CRISPR-Cas12 systems (Type V) have expand the CRISPR-Cas arsenal for genomic editing [44]. Cpf1 was characterised firstly and renamed as Cas12a [45], C2c1 (Cas12b) [46] and other type V members were identified subsequently [37,47,48]. Chen et al. reported a technique named DETECTR (DNA endonuclease-targeted CRISPR trans reporter), which provides a straightforward platform for molecular diagnostics [38]. DETECTR achieves attomolar sensitivity for DNA detection by combination the activation of non-specific single-stranded deoxyribonuclease of Cas12a ssDNase with isothermal amplification that enables fast and specific detection of virus from patient samples. In this assay, crRNA-Cas12a complex binds to target DNA and induces indiscriminate cleavage of ssDNA that is coupled to a fluorescent reporter. The author used DETECTR to differentiate between different types of human papillomavirus from cultured human cells and clinical samples within 1 h [38]. In addition, another technique combines CRISPR-Cas12 with a fluorescence-based point-of-care (POC) system is recently reported for rapid and detection for accurate African Swine Fever Virus (ASFV) [49]. In this method, Cas12a/crRNA detects and binds to targeting DNA, the Cas12a/crRNA/DNA complex becomes activated and degrades a fluorescent ssDNA reporter. The author used this method to detect ASFV at a detection limit of 1 mM within 2 h. A detection limit of 100 fM can be achieved after 24 h of incubation.
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