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PubMed1985

Copy number of the broad host-range plasmid R1162 is determined by the amounts of essential plasmid-encoded proteins.

DNA of the broad host-range plasmid R1162 contains a 1700 base-pair segment essential for plasmid maintenance. This region, RepI, consists of two cotranscribed genes encoding polypeptides with molecular weights of 29,000 and 31,000. Fusion of RepI to the strong tac promoter results in greatly increased amounts of at least one of these polypeptides. In trans, this construction has two other properties: it can raise the copy number of R1162, and it can protect this plasmid from loss due to incompatibility. Both effects require intact RepI genes. These properties of the RepI region, along with those of an origin-linked region described earlier, are discussed with respect to current models for control of plasmid copy number.

Adenosine Triphosphatases↗
PubMed1983

Nucleotide sequences of gag-pol regions that determine the Fv-1 host range property of BALB/c N-tropic and B-tropic murine leukemia viruses.

Previously, in vitro recombinant DNA studies demonstrated that genetic determinants of N-tropism and B-tropism, or Fv-1-related host range properties of murine leukemia viruses, were located in a BamHI-HindIII DNA segment derived from the 5' portion of the cloned viral genome. We sequenced this segment and its immediate 5' region from cloned DNA of two BALB/c mouse C-type viruses (WN1802N and WN1802B) and found base differences at 12 positions out of the otherwise identical 1,390-base-pair sequences. Analysis of the most likely reading frame showed that 6 of the 12 base differences would result in four encoded amino acid changes, three of which occur at positions 109 (glutamine in WN1802N versus threonine in WN1802B), 110 (arginine in WN1802N versus glutamic acid in WN1802B), and 159 (glutamic acid in WN1802N versus glycine in WN1802B) of the p30 protein. The remaining one is located at position 36 (threonine in WN1802N versus isoleucine in WN1802B) of the viral polymerase protein. Significant conformational alteration of the p30 protein could be predicted from these amino acid changes.

Alleles↗
PubMed2003

Influenza type A in humans, mammals and birds: determinants of virus virulence, host-range and interspecies transmission.

The virulence of a virus is determined by its ability to adversely affect the host cell, host organism or population of host organisms. Influenza A viruses have been responsible for four pandemics of severe human respiratory disease this century. Avian species harbour a large reservoir of influenza virus strains, which can contribute genes to potential new pandemic human strains. The fundamental importance of understanding the role of each of these genes in determining virulence in birds and humans was dramatically emphasised by the recent direct transmission of avian influenza A viruses to humans, causing fatal infection but not community spread. An understanding of the factors involved in transmission between avian and mammalian species should assist in the development of better surveillance strategies for early recognition of influenza A virus strains having human pandemic potential, and possibly in the design of anti-viral strategies.

Animals↗
PubMed1995

Both bipartite geminivirus movement proteins define viral host range, but only BL1 determines viral pathogenicity.

Bipartite geminiviruses such as squash leaf curl virus (SqLCV) encode two movement proteins (MPs), BR1 and BL1, that are essential for virus movement and systemic infection of host plants. BR1 has been implicated in the host range properties of the virus, and BL1 in viral pathogenic properties. To more precisely examine the roles of each MP, we have introduced missense and deletion mutations into the coding sequence of both BR1 and BL1, and examined the effects of these mutations on viral infectivity and the production of disease symptoms in pumpkin, squash, and Nicotiana benthamiana. For each MP, a range of mutant phenotypes from partially to fully defective was observed that affected the overall level and rate of infectivity. However, only mutations in BL1, and not BR1, affected the severity of disease symptoms, confirming our earlier finding that BL1 is responsible for the production of disease symptoms. For all mutants, the cucurbit hosts were found to be more permissive for viral movement than was N. benthamiana, and several mutations in both BL1 and BR1 produced host-specific phenotypes, retaining high levels of infectivity in pumpkin and squash, but abolishing infectivity for N. benthamiana. Unexpectedly, functional SqLCV coat protein (AR1) was found to specifically mask the phenotypes of certain BR1 mutations, suggesting some redundancy of function between coat protein and the BR1 MP and an interaction of AR1 with the viral movement pathway. AR1 and BR1 have similar nucleic acid binding affinities, suggesting a possible mechanism for the observed effects of the viral coat protein on viral movement.

Amino Acid Sequence↗
PubMed1999

Adaptation of the geminivirus bean yellow dwarf virus to dicotyledonous hosts involves both virion-sense and complementary-sense genes.

Bean yellow dwarf virus (BeYDV) and maize streak virus (MSV) belong to the geminivirus genus Mastrevirus and have host ranges confined to dicotyledonous and monocotyledonous species, respectively. To investigate viral determinants of host range specificity, chimeras were constructed by exchanging their coding and non-coding regions. BeYDV chimeras containing MSV ORF V1, ORF V2 or small intergenic region sequences, either individually or in various sequential combinations, replicated and produced virus particles in Nicotiana tabacum protoplasts. BeYDV chimeras containing MSV ORFs C1 and C2 and/or the large intergenic region were unable to replicate. None of the chimeras was able to systemically infect either N. benthamiana or maize. Complementation experiments using BeYDV chimeras containing MSV ORF V1 and/or ORF V2 suggest that expression of MSV movement protein and/or coat protein prevents BeYDV movement. The results demonstrate that factors involved in both viral DNA replication and virus movement are exclusively adapted to either monocotyledonous or dicotyledonous host backgrounds.

Adaptation, Physiological↗
PubMed2003

Host range of poliovirus is restricted to simians because of a rapid sequence change of the poliovirus receptor gene during evolution.

The host range of most poliovirus (PV) strains is restricted to simians. This host range specificity is believed to be determined by the interaction between PV and its receptor molecule. To elucidate the molecular basis of this species-specific infection of PV, we cloned orthologs of the PV receptor (PVR) gene ( pvr) as well as those of PV receptor-related genes 1 and 2 ( prr1 and prr2) from various mammalian species. These three genes are widely present in mammalian genomes including those of non-susceptible species. Comparison of the deduced amino acid sequences of PVR orthologs revealed that the NH(2)-terminal immunoglobulin-like domain (domain 1), which is the virus binding site in the human PVR, is highly variable among species, whereas that of PRR1 is highly conserved. Domain 1 of the PVR orthologs for the ring-tailed lemur and rabbit, which are not susceptible to PV, show only 51 and 61% amino acid sequence identity to that of human PVR, respectively. Chimeric PVR proteins that have the domain 1 of the ring-tailed lemur and rabbit PVRs failed to serve as receptors for PV. These results suggest that rapid changes in the domain 1 sequence during mammalian evolution determined the host range restriction of PV.

Amino Acid Sequence↗
PubMed2003

Roles of outer capsid proteins as determinants of pathogenicity and host range restriction of avian rotaviruses in a suckling mouse model.

We previously demonstrated that a pigeon rotavirus, PO-13, but not turkey strains Ty-3 and Ty-1 and a chicken strain, Ch-1, induced diarrhea in heterologous suckling mice. In this study, it was suggested that these avirulent strains, but not PO-13, were inactivated immediately in gastrointestinal tracts of suckling mice when they were orally inoculated. To determine which viral proteins contribute to the differences between the pathogenicitiy and the inactivation of PO-13 and Ty-3 in suckling mice, six PO-13 x Ty-3 reassortant strains that had the genes of the outer capsid proteins, VP4 and VP7, derived from the opposite strain were prepared and were orally inoculated to suckling mice. A single strain that had both PO-13 VP4 and VP7 with the genetic background of Ty-3 had an intermediate virulence for suckling mice. Three strains with Ty-3 VP7, regardless of the origin of VP4, rapidly disappeared from gastrointestinal tracts of suckling mice. These results indicated that the difference between the pathogenicity of PO-13 and that of Ty-3 was mainly dependent on both their VP4 and VP7. In particular, VP7 was found to be related to the inactivation of Ty-3 in gastrointestinal tracts of suckling mice.

Animals↗
PubMed1988

The avian retrovirus env gene family: molecular analysis of host range and antigenic variants.

The nucleotide sequence of the env gp85-coding domain from two avian sarcoma and leukosis retrovirus isolates was determined to identify host range and antigenic determinants. The predicted amino acid sequence of gp85 from a subgroup D virus isolate of the Schmidt-Ruppin strain of Rous sarcoma virus was compared with the previously reported sequences of subgroup A, B, C, and E avian sarcoma and leukosis retroviruses. Subgroup D viruses are closely related to the subgroup B viruses but have an extended host range that includes the ability to penetrate certain mammalian cells. There are 27 amino acid differences shared between the subgroup D sequence and three subgroup B sequences. At 16 of these sites, the subgroup D sequence is identical to the sequence of one or more of the other subgroup viruses (A, C, and E). The remaining 11 sites are specific to subgroup D and show some clustering in the two large variable regions that are thought to be major determinants of host range. Biological analysis of recombinant viruses containing a dominant selectable marker confirmed the role of the gp85-coding domain in determining the host range of the subgroup D virus in the infection of mammalian cells. We also compared the sequence of the gp85-coding domain from two subgroup A viruses, Rous-associated virus type 1 and a subgroup A virus of the Schmidt-Ruppin strain of Rous sarcoma virus. The comparison revealed 24 nonconservative amino acid changes, of which 6 result in changes in potential glycosylation sites. The positions of 10 amino acid differences are coincident with the positions of 10 differences found between two subgroup B virus env gene sequences. These 10 sites identify seven domains in the sequence which may constitute determinants of type-specific antigenicity. Using a molecular recombinant, we demonstrated that type-specific neutralization of two subgroup A viruses was associated with the gp85-coding domain of the virus.

Alpharetrovirus↗
PubMed1993

A single missense mutation in the BR1 movement protein alters the host range of the squash leaf curl geminivirus.

The bipartite geminiviruses causing squash leaf curl disease, SqLCV-E and SqLCV-R, have a broad host range that includes Nicotiana benthamiana, pumpkin, squash, and beans. We have characterized a naturally occurring mutant of the SqLCV-R B component (BRtd1) which has lost the ability to infect N. benthamiana, but still retains full infectivity for pumpkin and squash. The mutation responsible for this host range alteration was localized to the coding region of BR1, a gene essential for viral movement. Sequence analysis identified three missense mutations in the BR1 gene encoded by BRtd1. By site-directed mutagenesis, one of these missense mutations, a substitution of Cys for Arg at position 98 in the BR1 protein, has been identified as responsible for the altered host range properties of BRtd1. These results establish a role for the BR1 movement protein in determining the host range properties of SqLCV.

Agrobacterium tumefaciens↗
PubMed1997

The coevolutionary potential of a 'generalist' parasite, the hen flea Ceratophyllus gallinae.

Hosts exert selection pressures on their parasites and it is often assumed that host-parasite coevolution with each host is less intense in a generalist parasite than for a parasite with a narrow host range. Selection pressure on the parasite, however, is rather determined by host specificity, i.e. the relative importance of each host, than simply by the range of hosts. The determination of host specificity requires an assessment of the prevalence and intensity of parasite infestation within each host's nests, as well as the local abundance of each host species. Since the hen flea, Ceratophyllus gallinae, is a rather generalist parasite of birds it could be concluded that there has been weak coevolution with each of its hosts. By reviewing the literature on the prevalence and intensity of hen flea infestations in bird nests we estimated the number of individuals produced in the nest of each host species. The comparative analysis shows (1) that the prevalence of infestation is highest in hole-nesting avian families, (2) that prevalence and intensity of infestation among bird families are highly correlated, and (3) that hole-nesting Paridae have the highest intensities of infestation and harbour the majority of the flea population. These results underline the fleas' potential for coevolution with Paridae despite their extensive host range.

Animals↗
PubMed2004

The exploitation of distinct recognition receptors in dendritic cells determines the full range of host immune relationships with Candida albicans.

Dendritic cells (DC) sense saprophytic yeast and pathogenic, filamentous forms of Candida albicans in a specific way, resulting in disparate patterns of DC and T(h) cell activation. Using human and murine DC, such disparate patterns could be traced to the exploitation of distinct recognition receptors. Although usage of mannose receptors led to protective type 1 responses in mice, entry through Fcgamma receptors was responsible for suppression of mannose receptor-dependent reactivity, onset of type 2 responses and associated pathology. As the usage of distinct receptors selectively occurred with yeast or hyphal forms of the fungus, these findings suggest that the responsibility for pathogenicity of C. albicans is shared by the organism and DC, with implications for fungal virulence, immunity and vaccine development.

Animals↗
PubMed1998

Gag-Pol region determines the tropism of SIVagm for human cells.

Simian immunodeficiency virus isolated from African green monkeys (SIVagm) does not grow in many of human cell lines such as CEM x 174, H9, and MT-4, but could replicate in some human cell lines. Sequence of SIVagm responsible for its narrow host range was determined by making and monitoring growth potential of chimeric clones between SIVagm and human immunodeficiency virus type 1 (HIV-1). The results obtained indicated that the gag-pol region determines the observed narrow host range. By monitoring virus DNA synthesis and progeny virion production, the defect(s) of SIVagm in the replication in the restricted cells was demonstrated to be located at early phase.

Animals↗
PubMed1999

Host range, specificity, and virulence of Steinernema feltiae, Steinernema rarum, and Heterorhabditis bacteriophora (Steinernematidae and Heterorhabditidae) from Argentina.

Infections were carried out in the laboratory to determine the host range, specificity, and virulence of Steinernema rarum, S. feltiae, and Heterorhabditis bacteriophora that were isolated from different regions of Argentina. All insect orders showed a remarkable susceptibility to the three nematode species, showing mortality values higher than 66%, except for Anoplura. The mortality of the insects of agronomic interest was more than 90%. As for insects of sanitary importance, S. feltiae and S. rarum caused 60% of mortality, whereas H. bacteriophora caused 80%. The results fluctuated when considering the buccal apparatus function of the insects. Nematodes completed their cycle in anoplurans, orthopterans, lepidopterans, and hymenopterans, while the development varied in coleopterans, homopterans, hemipterans, and dipterans. S. rarum developed completely both in immature and adult, while S. feltiae and H. bacteriophora developed preferably in immature. The three isolates are capable of parasitizing a wide host range under laboratory conditions; H. bacteriophora is more virulent than the evaluated Steinernema spp. against Galleria mellonella larvae; the pathogenicity and specificity depend on the bioecological characteristics of nematodes and hosts.

Animals↗
PubMed1992

Host range analysis of a chimeric simian virus 40 genome containing the BKV capsid genes.

Simian virus 40 (SV40) propagates poorly in cells from human embryonic kidney (HEK) and human fetal fibroblasts (HFF) while BK virus grows well in many human cell types. It has been suggested that sequences within the SV40 late region but not within the BKV late region may act to inhibit growth of virus in HEK and HFF cells. In order to test this and to identify a late region host range function, we have replaced the late region of wtSV40 DNA with the late region of RFV (a variant of BKV) to produce an intermolecular hybrid or chimera. The constructed SV40/RFV chimeric genome contained approx. 5900 base pairs, more than 650 base pairs greater than wtSV40. Nevertheless, when introduced by transfection the chimera appeared to be infectious. Three chimeric genomes were recovered from infected cells and all contained deletions of nearly 600 base pairs, exclusively at the region of the 3' terminal junction. Since all three chimeras propagated in human HFF and HEK cells, the RFV late region and not the RFV regulatory region possesses a host range function required for growth in human cells. Analysis of T-antigen gene expression suggests that the replacement of the SV40 late region with the BKV late region leads to full expression of the SV40 early region in human cells. Two chimeras exhibited a BKV-like host range and the third exhibited both a BKV and an SV40-like host range. We determined precisely which sequences were deleted in each chimera and we exchanged 3' terminal junction fragments containing these deletions, between two chimeras with different host ranges. From these experiments we demonstrated that: (1) The 3' terminus of the SV40 large T-antigen gene is required for growth of SV40/RFV in TC-7 and CV-1 simian cells but not for growth in human cells; (2) while the SV40 late region is refractory for growth in human cells, the RFV late region is not refractory for growth in simian cells; (3) the 3' terminus of the RFV T-antigen gene is not required for growth in human cells. The results of the 3' terminal junction exchanges and studies of early gene expression also demonstrate that BKV and SV40 can penetrate human and simian cells, even when they failed to grow in one cell type.

Animals↗
PubMed2004

The role of honeydew in host searching of aphid hyperparasitoids.

Foraging in many insect parasitoids is mediated by chemicals associated with hosts. For example, honeydew, the feces of feeding aphids, induces and/or prolongs searching behavior of aphid parasitoids. In the laboratory, we tested if aphid hyperparasitoids, which belong to a higher trophic level, also rely on aphid honeydew to locate their hosts. We used the potato aphid. Macrosiphum euphorbiae, the primary parasitoid, Aphidius nigripes, and four hyperparasitoids, Asaphes suspensus, Dendrocerus carpenteri. Alloxysta victrix, and Syrphophagus aphidivorus that possess different biological attributes and host ranges. We determined if foraging hyperparasitoid females could discriminate between (i) honeydew from a host and a non-aphid host (the potato aphid and the soft brown scale, Coccus hesperidum), and (ii) honeydew from healthy aphids and those parasitized by A. nigripes. Females of A. suspensus did not react to any of the honeydew treatments. While the presence of non-aphid honeydew did not modify the behavior of A. victrix, D. carpenteri, and S. aphidivorus females, they exhibited an increase in searching time and path length but not walking speed when in the presence of honeydew from aphids. However, there were no changes in host searching behaviors, such as antennation or ovipositor probing that have been reported for primary aphid parasitoids. There was no difference in the response of hyperparasitoid females to honeydew from healthy and parasitized aphids. These results indicate that hyperparasitoids may use aphid honeydew, a conspicuous cue from the second trophic level, as an infochemical to locate their hosts.

Animals↗
PubMed1998

In vitro and in vivo host range of Anticarsia gemmatalis multiple nuclear polyhedrosis virus.

A clone of the wild type (wt) Anticarsia gemmatalis multiple nuclear polyhedrosis virus AgMNPV, derived from a geographical isolate (Hondrina, Brazil) and designated AgMNPV-CL4-3A1, was used to determine the host range of this virus in six established lepidopteran cell lines: Anticarsia gemmatalis (BCIRL-AG-AM1), Helicoverpa zea (BCIRL-HZ-AM1), Heliothis virescens (BCIRL-HV-AM1), Helicoverpa armigera (BCIRL-HA-AM1), Trichoplusia ni (TN-CL1), Bombyx mori (BMN), and a coleopteran cell line Anthonomus grandis (BRL-AG-1). In addition, the in vivo host range of this clone was also assayed in larvae of Helicoverpa zea, Heliothis virescens, Trichoplusia ni, and the homologous species Anticarsia gemmatalis by probit analysis. On the basis of temporal studies of TCID50 values, BCIRL-HV-AM1 cells gave the highest extracellular virus (ECV) titer (9.7 x 10(6) TCID50/ml) followed by BCIRL-HA-AM1 cells (8.3 x 10(5) TCID50/ml) and BCIRL-AG-AM1 cells (3.2 x 10(5) TCID50/ml). In addition, a low ECV titer of 1.37 x 10(3) TCID50/ml was detected from TN-CL1 cells 96 h postinoculation, while BRL-AG-1, BMN, and BCIRL-HZ-AM1 cells were nonpermissive to AgMNPV-CL4-3A1 on the basis of TCID50 results. AgMNPV-CL4-3A1 and the wild type AgMNPV had similar restriction profiles that were different from wild type AcMNPV. The LC50 values were 96.9, 564.6, 733.3, and 1.1 x 10(4) occlusion bodies/cm2 of diet for A. gemmatalis, Helicoverpa zea, Heliothis virescens, and T. ni, respectively.

Animals↗