Viral fitness and virulence. Medical search. Frequent questions

Pathogenicity and Virulence of Ebolaviruses with Species- and Variant-specificity. (cdc.gov)
Fitness obstacles to infections adapting to brand-new hosts, including efficient viral replication and host-to-host transmissibility, may be selected for individually of changes associated with virulence and pathogenicity properties and might be associated with different and possibly conflicting or competing mutations (61). (biopaqc.com)
It was not until the modern molecular biology era the genome of the 1918 pandemic computer virus could be sequenced from small viral RNA fragments retained in the lung cells of victims of the 1918 pandemic computer virus (60) and reconstructed by reverse genetics to evaluate its pathogenicity in animal models (65). (biopaqc.com)
To summarize, in the short-term, this project expects to provide much needed quality data about viral pathogenicity and data on full genome sequence of the SARS-CoV-2 in mild versus severe cases. (ous-research.no)
Targeting bacterial virulence factors is a wise option, as it can mitigate the pathogenicity of bacteria without eradicating them. (qxmd.com)
The pathogenicity of C. albicans is mainly due to its virulence factors, which are the novel targets of antifungal drugs for low risk of resistance development. (qxmd.com)
Our previous studies recognized peptidyl-prolyl isomerase (PrsA) as a critical virulence factor promoting SS2 pathogenicity. (qxmd.com)

Viral determinants that drive Enterovirus-A71 fitness and virulence. (nih.gov)
Bergstrom CT, McElhany P, Real LA (1999) Transmission bottlenecks as determinants of virulence in rapidly evolving pathogens. (springer.com)

Experimental manipulation of population-level MHC diversity controls pathogen virulence evolution in Mus musculus. (utah.edu)
Theory of the evolution of pathogen specialization suggests that a specialist pathogen gains high fitness in one host, but this comes with fitness loss in other hosts. (usgs.gov)
Evolution of the UC generalist from an ancestral UP sockeye specialist was associated with fitness increases in steelhead and Chinook salmon, but only slight decrease in fitness in sockeye salmon, consistent with low- or no-cost generalism. (usgs.gov)
These results also quantify within-host replicative fitness tradeoffs resulting from the natural evolution of specialist and generalist virus lineages in multi-host ecosystems. (usgs.gov)
This study illustrates the importance of coupling genomic and biologic comparisons of viral strains in order to enhance understanding of viral evolution and pathogenesis. (biomedcentral.com)
Charpentier C, Dwyer DE, Mammano F, Lecossier D, Clavel F, Hance AJ (2004) Role of minority populations of human immunodeficiency virus type 1 in the evolution of viral resistance to protease inhibitors. (springer.com)
The purpose of this project is to gain new knowledge about the genomic evolution and clinical correlation of viral variants (quasispecies) of the previously unknown virus, SARS-CoV-2, in both hospitalized and outpatients. (ous-research.no)
Evolution is a result of random mutations (or errors) in the viral genome when it replicates. (thewire.in)
So we can expect an arms race between vaccine developers and the virus, with vaccines trying to play catch up with viral evolution. (thewire.in)
[1] But this appears to be little more than harsh rhetoric: the NCSE cites papers that demonstrate trivial degrees of evolution and when read carefully, actually validate EE's arguments about fitness costs associated with antibiotic resistance. (exploreevolution.com)
The NCSE later admits that "Explore Evolution then says mutations do confer resistance but with a 'fitness cost. (exploreevolution.com)
Dr. Dugan was an assistant professor of viral genomics at the J. Craig Venter Institute from 2010 to 2012, where she focused on influenza and vector-borne viral genomics, viral evolution and synthetic influenza vaccine development. (cdc.gov)

As a result, specialist pathogens are predicted to have greater variation in fitness across hosts, and generalists would have lower fitness variation across hosts. (usgs.gov)
Klebsiella Pneumoniae Causes Bacteremia Using Factors That Mediate Tissue-Specific Fitness and Resistance to Oxidative Stress Published in PLOS Pathogens on July 18th, 2023 New research from MCIDT affiliates Dr. Harry Mobley and Dr. Lili Zhao identifies genes that aid. (umich.edu)
Studies the molecular basis of virulence of bacterial pathogens of veterinary and public health importance toward the design of control strategies. (salmonella-systomics.ca)

Treatment-associated polymorphisms in protease are significantly associated with higher viral load and lower CD4 count in newly diagnosed drug-naive HIV-1 infected patients. (ox.ac.uk)
Protease genotypic variability estimated to increase fitness during treatment was associated with higher viral load and lower CD4 cell counts also in treatment-naive patients, which could primarily be attributed to well-known compensatory mutations at highly polymorphic positions. (ox.ac.uk)

The finding that a viral population was essentially a pool of mutants came at a time when mutations in general genetics were considered rare events, and virologists associated a viral genome with a defined nucleotide sequence, as still implied today in the contents of data banks. (wikipedia.org)
This deficiency could be overcome using genome-wide analysis of multiple viral strains by high-throughput sequencing. (biomedcentral.com)
The researchers say this heralds the application of these molecules as chemical probes to explore viral biology and produce specific antivirals targeting RNA regions of the coronavirus genome. (news-medical.net)
and viral genome condensation for virion assembly. (news-medical.net)

By contrast, a generalist pathogen does not achieve high fitness in any host, but gains ecological fitness by exploiting different hosts, and has higher fitness than specialists in non-specialized hosts. (usgs.gov)
We test these hypotheses by measuring pathogen replicative fitness as within-host viral loads from the onset of infection to the beginning of virus clearance, using the rhabdovirus infectious hematopoietic necrosis virus (IHNV) in salmonid fish. (usgs.gov)
By contrast, a generalist pathogen does not achieve high fitness in any host, but gains ecological fitness by exploiting different hosts, and has higher fitness than specialists in nonspecialized hosts. (usgs.gov)
Evolutionary theory hypothesizes that intermediate virulence maximizes pathogen fitness as a result of a trade-off between virulence and transmission, but empirical evidence remains scarce. (johnshopkins.edu)
Previous studies suggest that most viruses will co-evolve with their hosts, and intermediate virulence maximizes pathogen fitness, which is called a trade-off between virulence and transmission[7]. (researchsquare.com)

A viral quasispecies is a population structure of viruses with a large number of variant genomes (related by mutations). (wikipedia.org)
However, standard clonal analyses and deep sequencing methodologies have confirmed the presence of myriads of mutant genomes in viral populations, and their participation in adaptive processes. (wikipedia.org)
The cloud nature of Qβ was understood as a consequence of its high mutation rate, calculated in 10−4 mutations introduced per nucleotide copied, together with tolerance of individual genomes to accept an undetermined proportion of the newly arising mutations, despite fitness costs. (wikipedia.org)
We have sequenced the genomes of a further seven strains from various geographical sources, and have compared their growth in vitro and virulence in vivo. (biomedcentral.com)
On the contrary, current evidence indicates that mutant spectra contribute to viral pathogenesis, can modulate the expression of phenotypic traits by subpopulations of viruses, can include memory genomes that reflect the past evolutionary history of the viral lineage, and, furthermore, can participate in viral extinction through lethal mutagenesis. (springer.com)
Arias A, Ruiz-Jarabo CM, Escarmis C, Domingo E (2004) Fitness increase of memory genomes in a viral quasispecies. (springer.com)
For example, differences in alleles, or forms of genes that arise from mutations, between the viral genomes collected from vaccinated versus unvaccinated individuals would indicate that selection has taken place. (debuglies.com)

First, increased transmissibility allows the virus to pass from person to person more efficiently, and perhaps with a lower viral load, meaning fewer viruses are needed for infection. (jax.org)
Viruses carrying the H4-HA with or without R327 or K327 mutations and the other gene segments from HPAIV H5N1 exhibited high virulence and efficient transmission in chickens. (preprints.org)
Additional nuances in the data included different fitness levels for non-specialist interactions, reflecting different trade-offs for specialist viruses in other hosts. (usgs.gov)
The survival of the fittest in the virus world depends on those trans-generationally inheritable attributes that endow a virus with the ability to produce more viruses (higher viral load) with more virulence than the parental generation virus. (biologyonline.com)
During viral infections, the complex and dynamic distributions of variants, termed viral quasispecies, play a key role in the adaptability of viruses to changing environments and the fate of the population as a whole. (springer.com)
Virulence and transmission characteristics of clade 2.3.4.4b H5N6 subtype avian influenza viruses possessing different internal gene constellations. (qxmd.com)
New viral strains can also develop via recombination , when viruses acquire genes from other viruses or even from their hosts. (thewire.in)
In a project funded by the National Institutes of Health NIAID , we are developing safer live attenuated vaccines for chikungunya and Venezuelan equine encephalitis viruses using virus variants that mutate less frequently and therefore develop fewer mutations that confer virulence. (ucdavis.edu)
Viruses cannot reproduce themselves until they infect a living cell, she explained, so viral RNA or DNA cause an infected cell to make copies of the virus, thus infecting other living cells and potentially making people very sick in the process. (health.mil)
When considering natural selection in viruses, two aspects of the viral lifecycle are particularly important. (isemph.org)

Middlebrook EA, Stark DL, Cornwall DH, Kubinak JL, Potts WK (2021) Deep sequencing of MHC-adapted viral lines reveals complex recombinational exchanges with endogenous retroviruses leading to high-frequency variants. (utah.edu)
Viral quasispecies refer to a population, or mutant cloud, consisting of large numbers of genomic viral variants. (ous-research.no)
Quasispecies recognition is important for identification of pathogenic RNA virus variants leading to selection of treatment or vaccine-escape variants, immune escape, increased virulence and development of future anti-viral therapies. (ous-research.no)
viral variants that can evade vaccines have an evolutionary advantage. (thewire.in)
These variants have increased transmissibility, and virulence. (indiatimes.com)

Quasispecies result from high mutation rates as mutants arise continually and change in relative frequency as viral replication and selection proceeds. (wikipedia.org)
Viral kinetics show that the mechanisms of specialization involve both the ability to maximize early virus replication and to avoid clearance at later times, with different mechanisms of specialization evident in different host-virus combinations. (usgs.gov)
A new U.S. study published on the bioRxiv * preprint server reports the use of an amiloride-based scaffold that targets a viral RNA structure known to be essential in viral replication in the 5'-untranslated region (UTR) of the virus. (news-medical.net)
The virus exploits the host machinery to facilitate efficient viral replication, which ultimately leads to progression of infection. (news-medical.net)
These are apparently cis-elements involved in regulating viral replication. (news-medical.net)

Therefore, the evolutionary trajectory of the viral infection cannot be predicted solely from the characteristics of the fittest sequence. (wikipedia.org)
Mitochondria-mediated oxidative stress during viral infection. (nih.gov)
Collectively, these studies will provide new information on how EVs-critical for both the virulence of orthopoxviruses and their utility as oncolytic vectors-assemble, egress, and spread to new cells during infection. (hhs.gov)
Reduction of set-point viral loads should have resulted in a 20% reduction in incidence, and a three years extension of untreated asymptomatic infection, increasing opportunities for timely treatment of infected individuals. (johnshopkins.edu)
More importantly, differential viral kinetics correlated with differential pro-inflammatory host immune responses in the lungs of infected ferrets, where OR-infected animals developed a protective higher expression of type I IFN and Retinoid acid Inducible Gene I (RIG-I) genes early after infection, resulting in the development of milder disease. (bris.ac.uk)

and (v) a negative correlation was observed among strains between viral growth in vitro and virulence in vivo. (biomedcentral.com)
This may be related to a higher viral load (more copies of the virus) in someone infected with delta compared with earlier strains. (thewire.in)
Further, phage production leads to a net positive gain in fitness only at antibiotic concentrations slightly above the MIC (i.e., concentrations for which the benefits of antibiotic sequestration outweigh the metabolic cost of phage production) but which are not lethal for Pf+ strains. (stanford.edu)
The objective of this work was to compare the fitness of two strains of OR (R6 and R7) containing the H275Y mutation, and a wild-type (F) pandemic influenza A (H1N1) 2009 (pdm09) virus both in vitro and in vivo in mice and to select one OR strain for a comparison with F in ferrets. (bris.ac.uk)

Using a new platform for unbiased and deep mutagenesis of any genomic locus in the prototypic orthopoxvirus, vaccinia virus (VACV), we conducted deep-mutational scans (DMS) of two EV proteins, A33 and A34, in the context of infectious viral particles and identified novel regiospecific mutations that enhance EV fitness. (hhs.gov)

The theory predicts that a viral quasispecies at a low but evolutionarily neutral and highly connected (that is, flat) region in the fitness landscape will outcompete a quasispecies located at a higher but narrower fitness peak in which the surrounding mutants are unfit. (wikipedia.org)

While compensatory mutations increase fitness during treatment, their presence may also modulate viral fitness and virulence in absence of therapy and major resistance mutations. (ox.ac.uk)

There's a trade-off between transmissibility and how sick a person gets (virulence) with most disease-causing microorganisms. (thewire.in)

If vaccines are not 100% effective in blocking transmission, we can expect a shift in the trade-off towards higher virulence. (thewire.in)
Excluding the influence of environmental factors, has the virulence of the SARS-CoV-2 been reduced in the process of transmission? (researchsquare.com)
Cryo-transmission electron micrograph of IIV6 displaying a fringe of hair-like fibers surrounding the viral particle (figure provided by IA Ince and J van Lent). (ictv.global)
The researchers also recommend that nasal swabs typically collected during clinical trials may be used to determine the viral titer, or amount of virus present, which can be considered a proxy for transmission potential. (debuglies.com)
Understanding how these two populations have influenced each other's' evolutionary trajectories - and ultimately why rabbit populations are still flourishing in Australia to this day- requires discussing one more layer of evolutionary complexity: virulence-transmission trade-offs. (isemph.org)
To the extent that this is true, it is often said that a virulence-transmission trade-off exists. (isemph.org)
Thus, while selective pressures on transmission drive virulence down, selective pressures that take place within the host drive it up. (isemph.org)
In particular, an approach which is agnostic to the taxonomy of the host, focusing on the fundamental ecological and evolutionary processes inherent to a pathogenic lifestyle (e.g., transmission, host immune or other defenses, virulence, or species interactions), promises rapid conceptual and technical advances. (springer.com)

The systems of host change, and mammalian web host version especially, remain only understood partly, characterizing the origin thus, virulence, and pathogenic properties of past pandemic influenza infections, like the 1918 trojan, is essential for current community wellness potential and preparedness pandemic setting up. (biopaqc.com)
These studies have shown that both the gene encoding hemagglutinin (HA) and those encoding the ribonucleoprotein polymerase (RNP) complex become virulence elements in chimeric infections in which a number of 1918 trojan genes was placed on the backdrop of the modern human-adapted seasonal influenza trojan. (biopaqc.com)

be associated with a wide range of clinical disease and viral ASPCR also can provide an accurate quantitative result of kinetics. (cdc.gov)
Ferrets infected with the F virus showed more severe clinical signs, histopathological lung lesions, and viral quantification when compared to OR R6-infected animals. (bris.ac.uk)

We show that specialist subgroups had highest peak and mean viral loads in the hosts in which they are specialized, and they had low viral loads in non-specialized hosts, resulting in large variation in viral load across hosts. (usgs.gov)
The generalist UC subgroup reached intermediate viral loads in all hosts and showed the smallest variation in fitness across hosts. (usgs.gov)

Arias A, Agudo R, Ferrer-Orta C, Pérez-Luque R, Airaksinen A, Brocchi E, Domingo E, Verdaguer N, Escarmis C (2005) Mutant viral polymerase in the transition of virus to error catastrophe identifies a critical site for RNA binding. (springer.com)

In parallel, we will perform genetic modifier and proteomic screens to uncover new functional interactions of A33/A34 with viral and host proteins. (hhs.gov)
These results suggest the presence of early specific viral-host immune interactions relevant in the development of influenza-associated lung pathology. (bris.ac.uk)

This work is an important step toward understanding and controlling the viral enteric problems commonly seen in young broilers and turkeys. (feedstuffs.com)

Sortase A (SrtA), which is critical for bacterial adhesion, invasion, and immune evasion, is a promising target for virulence inhibition in S. aureu s. (qxmd.com)
Sex-associated Early-life viral Innate Immune Response is Transcriptionally Associated with chromatin remodeling of Type-I IFN-inducible Genes Published in Mucosal Immunology on June 9th, 2023 Check out these new findings from MCIDT Affiliates Dr. Nicholas Lukacs and. (umich.edu)

Novel inhibitors that target bacterial virulence identified via HTS against intra-macrophage survival of Shigella flexneri Published in American Society for Microbiology on August 11th, 2023 MCIDT affiliate Dr. George Garcia is coming in with new research on the. (umich.edu)

The difficulty of finding effective antivirals in the current pandemic has stimulated the search for better drug development approaches that will reveal targetable viral structures, thus helping to prevent and treat both the current and any future coronavirus outbreaks. (news-medical.net)

We previously designed a modeling technique that quantifies genotypic footprints of in vivo treatment selective pressure, including both drug resistance mutations and polymorphic compensatory mutations, through the quantitative description of a fitness landscape from virus genetic sequences. (ox.ac.uk)
The association of surveillance drug resistance mutations, reported compensatory mutations and fitness estimated from drug selective pressure fitness landscapes with baseline viral load and CD4 cell count was evaluated using regression techniques. (ox.ac.uk)

The impact of single mutations or reassortment on virus fitness in vitro and in vivo was studied. (preprints.org)

Together, increasing the number of basic amino acids in the H4N2 HACS was detrimental for viral fitness particularly in vivo but compensated by reassortment with HPAIV H5N1. (preprints.org)

Since human being IAV had not yet been recognized in 1918, no viral isolates were made during the 1918-1919 influenza pandemic. (biopaqc.com)
However, genetic and/or serologic characterization cannot provide data for inference of pathotype or virulence, thus complicating the selection of the 'right' isolates for use in autogenous vaccines. (feedstuffs.com)

Anderson JP, Daifuku R, Loeb LA (2004) Viral error catastrophe by mutagenic nucleosides. (springer.com)
i) The virulence of the biocontrol agent must be enhanced to overcome evolutionary barriers either by mixing with synergistic chemicals or with one or more organisms, and/or by mutagenic or transgenic enhancing of virulence of the biocontrol fungus. (weizmann.ac.il)

Mouse fitness measures reveal incomplete functional redundancy of Hox paralogous group 1 proteins. (utah.edu)

Such fitness, in all its totality, takes care of the "species continuation" BUT with "the best gene pool " . (biologyonline.com)

Major drug resistance mutations severely impair viral fitness in a drug free environment, and therefore are expected to revert quickly. (ox.ac.uk)
The acquisition of oseltamivir resistance (OR) mutations, such as H275Y, hampers viral fitness. (bris.ac.uk)

We are genetically characterizing contemporary St. Louis encephalitis virus circulating in mosquitoes in California and performing experimental studies to evaluate viral, host, and environmental factors that promoted the re-emergence and establishment of St. Louis encephalitis virus in California since 2015. (ucdavis.edu)

The theory portrayed early replicon populations as organized mutant spectra dominated by a master sequence, the one endowed with the highest fitness (replicative capacity) in the distribution. (wikipedia.org)
The U.S. Poultry & Egg Assn. (USPOULTRY) and the USPOULTRY Foundation announced the completion of funded research projects: At the University of Georgia in Athens, Ga., researchers developed new tools and methods leading to improved vaccines for reovirus, while a U.S. Department of Agriculture research project characterized viral populations in the poultry intestinal tract. (feedstuffs.com)

Fitness of biological clones was inferior to that of the parental, uncloned population, a difference also documented for vesicular stomatitis virus (VSV). (wikipedia.org)
Here, we investigated the virulence of this virus in chickens after expansion of the polybasic CS by substitution of T327R (322PEKRRRR/G329) or T327K (322PEKRRKR/G329) with or without reassortment with HPAIVs H5N1 and H7N7. (preprints.org)
Arias A, Lázaro E, Escarmís C, Domingo E (2001) Molecular intermediates of fitness gain of an RNA virus: characterization of a mutant spectrum by biological and molecular cloning. (springer.com)
We robustly predict stabilising selection towards a low level of virulence, and rapid attenuation of the virus. (johnshopkins.edu)

Virions consist, of a central DNA/protein core surrounded in turn by an internal limiting membrane, a viral capsid, and, in the case of those particles that bud from the plasma membrane, an outer viral envelope (Figure 1. (ictv.global)

A hallmark of the complex biology of orthopoxvirus multiplication in the host cell cytoplasm is the generation of two distinct infectious forms-intracellular mature virions (IMV), which remain largely cell- associated, and enveloped virions (EV), which are critical for extracellular viral spread. (hhs.gov)

RESULTS: Genotypic correlates of viral load and CD4 cell count were evaluated in subtype B sequences from recently diagnosed treatment-naive patients enrolled in the SPREAD programme. (ox.ac.uk)
By contrast, treatment-related mutations in reverse transcriptase could not explain viral load or CD4 cell count variability. (ox.ac.uk)
Accordingly, set-point viral load, the most common measure of virulence, has declined in the last 20 years. (johnshopkins.edu)
This is because you need a certain viral load to be able to transmit. (thewire.in)

Our findings reveal how cells curb energy consumption while maintaining protein synthesis to advance fitness in nutrient-fluctuating environments. (yale.edu)

Immense effort is afoot in many a viral research laboratory to derail the virulence of this menace. (nutritionfit.org)

When we are asked to explain natural selection and survival of the fittest in the subject of Biology, we take forward the concept of biological or reproductive fitness. (biologyonline.com)

The master sequence is determined by viral fitness. (ous-research.no)

A host of viral RNAs and other RNAs involved in disease processes have also been demonstrated to be targeted effectively by small molecules. (news-medical.net)
Another critical virulence factor is the ability of Candida to adhere to the host tissue. (medscape.com)
In a broader view, a 2013 review of pathologic mechanisms of C albicans cited (1) the secretion of hydrolases, (2) molecules that mediate adhesion with concomitant invasion into host cells, (3) the yeast-to-hypha transition, (4) biofilm formation, (5) contact sensing and thigmotropism, (6) phenotypic switching, and (7) a variety of fitness attributes. (medscape.com)

Anatomy14

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