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Results for “Virus adaptation”

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At least 19 recordsLinked to original sources
PubMed2026

Comparative dynamics of Japanese encephalitis virus adaptation in porcine macrophages and insect cells.

BACKGROUND: Japanese encephalitis virus (JEV) is a zoonotic mosquito-borne Orthoflavivirus that circulates primarily in birds and pigs. Previous observations of vector-free transmission between pigs indicates the possibility of single-host cycling in swine. Therefore, the aim of this work was to investigate the evolutionary pressure of single host cycling using a relevant primary cell culture model. METHODS: To investigate whether such single-host cycles affect viral infectivity, fitness and genomic adaptations, two strains and a reverse genetic cDNA-derived clone of JEV were serially passaged 12 times in primary porcine monocyte-derived macrophages (MDMs), in Aedes albopictus-derived C6/36 cells, and alternately between both cell types. Next-generation sequencing analysis was used to identify selected single nucleotide variants (SNVs) and haplotypes. Phenotype-to-genotype connections were confirmed using reverse genetics. RESULTS: For all viruses, serial passaging in MDMs - but not in C6/36 cells - led to a rapid increase in relative infectivity toward MDMs, accompanied by reduced plaque sizes in porcine endothelial cells. In contrast to C6/36 cells, MDM imposed a strong selective pressure, rapidly favoring selection of many SNVs and viral haplotypes. In addition, we identified a dominant selection of mutants with glutamic acid to lysine substitutions at positions 49 or 138 in the E protein, which explained the small plaque phenotype and caused viral sensitivity to heparin-mediated inhibition of attachment, indicating enhanced virus binding to glycosaminoglycans (GAG). The E138K mutant also explained the increased relative infectivity for MDM. CONCLUSION: This work demonstrates a high evolutionary pressure on JEV in MDM causing rapid selections of minor haplotypes. Furthermore, the efficient selection of E49K and E138K SNV, which were responsible for the phenotype, are likely caused by a selective pressure for GAG binding, observed in vitro with other mammalian cells.

Animals↗
PubMed2026

O'nyong-nyong virus adaptive mutations in non-structural protein 1 and 3 enhance RNA replication and overcome FHL1 requirement.

Arthritogenic alphaviruses, like o'nyong-nyong virus (ONNV), cause debilitating musculoskeletal diseases and are geographically expanding. To predict their emergence, we seek to better understand evolutionary mechanisms that enable changes in virus tropism. Here, we identify adaptive mutations in the ONNV non-structural proteins (nsPs) that arose during cellular serial passaging and enabled ONNV to infect non-permissive Lunet cells. Using shotgun proteomics, we show that this human hepatoma cell line lacks the four-and-a-half-LIM domain protein 1 (FHL1), an essential host factor in ONNV RNA replication. Individual single nucleotide mutations in the nsP1 ring-aperture membrane-binding and oligomerization domain, the nsP3 macrodomain, and the nsP3 opal stop codon overcome FHL1 deficiency in Lunet cells by enhanced RNA replication. These findings demonstrate how subtle genomic changes in nsPs can profoundly influence alphavirus replication and tropism.

LIM Domain Proteins↗
PubMed1976

High-titer replication of nondefective Sendai virus in MDBK cells.

Egg-grown Sendai virus was adapted to growth in a bovine kidney cell line (MDBK cells) by serial passage under defined conditions. The adapted virus contained only 50S RNA and was highly infectious for MDBK cells. Infection of these cells with a high multiplicity of adapted virus resulted in a yield of 10(8) MDBK-infectious units/ml by 18 h, accompanied by severe cytopathic changes in the host. Cell fusion did not occur. Examination of the proteins of the adapted virus revealed that despite the high infectivity of this virus for MDBK cells the virions contained considerable quantities of Fo, the precursor to the F glycoprotein that is responsible for cell fusion and high infectivity in other systems.

Adaptation, Biological↗
PubMed1976

Effect of in vitro adaptation of Marek's disease virus on pock induction on the chorioallantoic membrane of embryonated chicken eggs.

Cell-associated preparations of several isolates of Marek's disease virus produced more pocks on the chorioallantoic membrane of embryonated chicken eggs than plaques in duck embryo fibroblasts, thus indicating that lesion response in eggs was more sensitive than cytopathic response in duck embryo fibroblasts for assaying low-passage Marek's disease virus. Adaptation of the virus to cell cultures by serial passages, however, substantially reduced its pock response so that the titer ratio (plaque-forming units in duck embryo fibroblasts/pock-forming units in eggs) of cell culture-adapted Marek's disease virus was 1 or higher. The decreased pock response could not be attributed to selection of preexisting virus variant(s) with low affinity for chorioallantoic membrane because cloned Marek's disease virus had a good pock response at low cell culture passage levels, but this response decreased as the virus was attenuated by serial cell culture passage.

Animals↗
PubMed2025

Extensive longevity and DNA virus-driven adaptation in nearctic Myotis bats.

The genus Myotis is one of the largest clades of bats, and exhibits some of the most extreme variation in lifespans among mammals alongside unique adaptations to viral tolerance and immune defense. To study the evolution of longevity-associated traits and infectious disease, we generated cell lines and near-complete genome assemblies for 8 closely related species of Myotis. Using genome-wide screens of positive selection, analyses of structural variation, and functional experiments in primary cells, we identify new patterns of adaptation contributing to longevity, cancer resistance, and viral interactions in bats. We show that the recurrent evolution of longevity seen in Myotis leads to some of the highest predicted increases in cancer risk across mammals and demonstrate a unique DNA damage response in primary cells of the long-lived M. lucifugus. We also find evidence of abundant adaptation in response to DNA viruses - but not RNA viruses - in Myotis and other bats in sharp contrast with other mammals, potentially contributing to the role of bats as reservoirs of zoonoses. Together, our results demonstrate how genomics and primary cells derived from diverse taxa uncover the molecular bases of extreme adaptations in non-model organisms.

Aging↗
PubMed1977

Comparative studies of wild-type and 'cold-mutant' (temperature sensitive) influenza viruses: geneology of the matrix (M) and non-structural (NS) proteins in recombinant cold-adapted H3N2 viruses.

The matrix (M) protein of the H2N2 virus A/Ann Arbor/6/60 may be distinguished from M protein of several H3N2 viruses and A/New Jersey/76 (HSWINI) by SDS acrylamide gel electrophoresis using a discontinuous buffer system. The smallest RNA (RNA 8) of the A/Ann Arbor/6/60 virus may be distinguished from RNA 8 of several H3N2 viruses by acrylamide gel electrophoresis in 3% or 3-6% gels in the absence of urea, if electrophoresis is done at 30 to 36 degrees C or 20 degrees C respectively. Ten clones of conditionally-lethal temperature-sensitive (ts) mutants were studied, which derived their cold-adaption and ts genes from mutant A/Ann Arbor/6/60, and their haemagglutinin from the H3N2 virus A/Scotland/840/74. Each clone was found to derive its M protein from A/Ann Arbor/6/60 mutant, and its RNA 8 from A/Scotland/840/74. The only assignment of genes 7 and 8 consistent with these findings for the recombinants is that in each parent virus (and in the recombinants) gene 7 codes for M protein, and gene 8 for NS protein. Furthermore, it may be concluded from the results that the biologically important ts lesions in the A/Ann Arbor/6/60 mutant parent are not present in the NS gene. In addition to the recombinants of A/Ann Arbor/6/60 and A/Scotland/840/74, five independent ts/cold-adapted recombinants of A/Ann Arbor/6/60 mutant with H3N2 and HSWINI wild-type viruses were examined, and all were found to contain the M protein of the A/Ann Arbor/6/60 mutant parent. This is suggestive that M protein may be at least partially responsible for the cold-adaptation and/or ts properties of the A/Ann Arbor/6/60 mutant and the recombinants.

Adaptation, Biological↗
PubMed1979

Murine influenzal tracheitis: a model for the study of influenza and tracheal epithelial repair.

The murine model of influenza virus infection is generally a lethal pneumonitis produced by a highly mouse-adapted virus. However, we infected mice with a less adapted virus and produced a nonlethal disease that involved the airways without producing gross pneumonitis. Changes that occurred in the tracheal epithelium were studied by scanning and transmission electron microscopy. Complete desquamation of the epithelium occurred within 3 days after infection, regeneration began within 5 days, and repair was complete within 2 wk after infection. This model is proposed as an alternative to the lethal pneumonitis for the study of murine influenza and also as a model for the study of repair of the respiratory ciliated epithelium.

Animals↗
PubMed1977

Immunofluorescent study on egg-adapted avian encephalomyelitis virus infection in chickens.

Fluorescent antibody study showed persistent infection of egg-adapted avian encephalomyelitis virus in the central nervous system and pancreatic tissues of infected embryos and chickens hatched from them. The limited organ tropism of the egg-adapted virus in hatched chickens was in striking contrast to the systemic infection that occurs with a field strain. In chidkens orally infected with egg-adapted virus strains, transient infection of a few organs was found despite occurrence of viremia.

Animals↗
PubMed1979

Effect of passage history on dengue-2 virus replication in subpopulations of human leukocytes.

Three passage levels of dengue-2 virus strain PR-159, obtained during the course of deriving the attenuated S-1 vaccine, were tested for their ability to replicate in subpopulations of human peripheral blood leukocytes: (i) 6th primary African green monkey kidney (PGMK) cell passage (parent virus); (ii) 19th PGMK cell passage of a small-plaque-forming clone derived from the parent virus (S-1 PGMK virus); and (iii) virus derived by four additional passages of the S-1 PGMK virus in diploid fetal rhesus lung cells (S-1 vaccine virus). Replication of these PR-159 viruses and another strain of dengue-2 virus adapted to Raji cells (16681-Raji virus) was measured in adherent and nonadherent mononuclear cells. All viruses except the S-1 PGMK virus replicated in monocytes. Occasional replication of the S-1 PGMK virus was associated with reversion to parent virus. The addition to the monocyte cultures of low concentrations of homologous dengue-2 antibody or non-neutralizing heterologous antibody increased the yield of the parent virus as much as 400-fold. This phenomenon of immune enhancement usually enabled the S-1 PGMK virus to replicate slowly in monocytes, but the progeny virus produced large plaques similar to the parent virus. Replication of the S-1 vaccine virus in cultured monocytes did not result in the appearance of large plaques. We could not recover S-1 vaccine virus from monocytes harvested from infected volunteers in the same manner that monocytes from natural human infections yield wild virus. The three passage levels of PR-159 virus were tested for replication in lymphocytes in comparison with the 16681-Raji virus. Only the 16681-Raji virus replicated in human lymphocytes cultured with or without enhancing antibody.

Animals↗
PubMed1977

Comparison of intestinal (Illinois strain) and cell culture-adapted (M-HP strain) viral populations of transmissible gastroenteritis of swine.

Intestinal and cell culture-adapted viral populations of transmissible gastroenteritis (TGE) of swine were compared by means of sucrose gradient centrifugation, immunnofluorescence, electron microscopy, immune electron microscopy, statistical analysis of the number of plaque-forming units, and ultraviolet sensitivity. Results indicated that the size range and general coronavirus morphologic characteristics were shared by both viral populations. Marked morphologic variations existed among particles from both populations. Unlike the cell culture-adapted virus, the Illinois virus of intestinal origin was infractions representing 2 bands of infectivity which were isolated by the sucrose gradient centrifugation method. The intestinal and cell culture-adapted TGE viruses were similar in antigenicity and in sensitivity to ultraviolet irradiation. There was no indication of a 2nd virus in addition to the coronavirus described as the cause of TGE.

Animals↗
PubMed1975

An animal model for studying infection and immunity to and attenuation of human parainfluenza viruses.

Neonatal ferrets were found to be highly via the intranasal route of inoculation to infection with wild type isolates of parainfluenza viruses. Wild type infection consistently resulted in deaths of these animals in 48 to 72 hours. Autopsy and histopathological findings in lung tissue were consistent with those of viral infection. Virus could consistently be isolated from lung tissues. Using wild green monkey kidney grown viruses and selected passage levels of egg adapted viruses, virus attenuation markers were observed by comparing infectivity in neonatal ferrets, propagation in cell cultures of human, primate, rabbit and chick embryo tissues, and in chick embryos and interferon induction. Adult pregant dams could be immunized (silently infected) and circulating hemagglutinin-inhibiting antibody could be detected within two weeks of intranasal instillation of wild and low egg passage types of virus. The animal model described could be valuable in studying immunity to parainfluenza virus infections.

Aerosols↗
PubMed1976

Virus content and effectiveness of foot-and-mouth disease vaccines.

(I) The amount of 22 nm particles in 26 batches of cattle tongue epithelium extract used for the preparation of C-type vaccine was determined with an improved 50% haemolytic and point complement fixation test after fluorocarbon precipitation of non-immunizing 7 nm particles. The total amount of 22 nm and 7 nm particles (alpha GN value) varied considerably from batch to batch, 22 nm components (alpha GF value) showing a maximum 5-fold difference. (ii) Effectiveness of vaccines with known virus content was tested in adult mice challenged with an adapted virus strain. In commercial C-type vaccines the complement-fixing activitiy of 22 nm particles and the potency of the vaccine showed a logarithmic regression (mouse index = -1.43 + 2.27 1g alpha GF).

Animals↗
PubMedDate not supplied

[Cellular hypersensitivity in the infection of mice by Junin virus. I. Passive transfer].

The data presented confirm previous evidence of delayed hypersensitivity in mice following infection with Junin virus. Adaptive transfer of sensitized cells from adult mice which had received 5 Junin virus injections into preinfected newborn mice shortened their survival by 72 hours. It was clear, however, that the development of the immunological mechanism in adult mice occurred under certain conditions. This evidence was confirmed by the observations that the induction of cell-mediated immunity and the response of sensitized lymphocytes to viral antigens appeared to be related to multiple injections of the virus. On the other hand, the sensitized cells were present in adult mice by day 9 and vanished 60 days after the infection. These results revealed the difference between the lymphoid cells from adult mice in the early and the late stages of immunity. The implications of these results in the development of the fatal neurological disease induced by the Junin virus in newborn mice are discussed.

Animals↗