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PubMed1973

Host specificity of Salmonella typhimurium deoxyribonucleic acid restriction and modification.

The restriction and modification genes of Salmonella typhimurium which lie near the thr locus were transferred to a restrictionless mutant of Escherichia coli. These genes were found to be allelic to the E. coli K, B, and A restriction and modification genes. E. coli recombinants with the restriction and modification host specificity of S. typhimurium restricted phage lambda that had been modified by each of the seven known host specificities of E. coli at efficiency of plating levels of about 10(-2). Phage lambda modified with the S. typhimurium host specificity was restricted by six of the seven E. coli host specificities but not by the RII (fi(-) R-factor controlled) host specificity. It is proposed that the restriction and modification enzymes of this S. typhimurium host specificity have two substrates, one of which is a substrate for the RII host specificity enzymes.

Alleles↗

PubMed2000

Host-specificity of monogenean (platyhelminth) parasites: a role for anterior adhesive areas?

Monogeneans (flatworms) are among the most host-specific of parasites in general and may be the most host-specific of all fish parasites. Specificity, in terms of a restricted spatial distribution within an environment, is not unique to parasites and is displayed by some fungi, insects, birds, symbionts and pelagic larvae of free-living marine invertebrates. The nature of cues, how "habitats" are recognised and how interactions between partners are mediated and maintained is of interest across these diverse "associations". We review some experiments that demonstrate important factors that contribute to host-specificity at the level of infective stages (larvae of oviparous monogeneans; juveniles of viviparous gyrodactylids) and adult parasites. Recent research on immune responses by fish to monogenean infections is considered. We emphasise the critical importance of host epidermis to the Monogenea. Monogeneans live on host epidermis, they live in its products (e.g. mucus), monopisthocotyleans feed on it, some of its products are "attractants" and it may be an inhospitable surface because of its immunological activity. We focus attention on fish but reference is made to amphibian hosts. We develop the concept for a potential role in host-specificity by the anterior adhesive areas, either the specialised tegument and/or anterior secretions produced by monogeneans for temporary but firm attachment during locomotion on host epithelial surfaces. Initial contact between the anterior adhesive areas of infective stages and host epidermis may serve two important purposes. (1) Appropriate sense organs or receptors on the parasite interact with a specific chemical or chemicals or with surface structures on host epidermis. (2) A specific but instant recognition or reaction occurs between component(s) of host mucus and the adhesive(s) secreted by monogeneans. The chemical composition of fish skin is known to be species-specific and our preliminary analysis of the chemistry of some monogenean adhesives indicates they are novel proteins that display some differences between parasite families and species.

Animals↗

PubMed2001

Comparative ribotyping of Staphylococcus intermedius isolated from members of the Canoidea gives possible evidence for host-specificity and co-evolution of bacteria and hosts.

A total of 41 Staphylococcus intermedius isolates were isolated from skin of healthy members of six phylogenetic groups within the Canoidea (the dog family, skunk subfamily, weasel subfamily, racoon family, red panda and bear family) of different geographical origin and compared by EcoRI ribotyping and cluster analysis. The S. intermedius isolates from the different families and subfamilies clustered together in separate groups, almost completely following the phylogenetic relationship of the animal hosts. These ribotype data indicate host-specificity of different types of S. intermedius and suggest co-evolution between the animal hosts within the Canoidea and S. intermedius.

Animals↗

PubMed1985

Transmission experiments on the host specificity of Heterophyes species in 16 potential definitive hosts.

Sixteen different species of piscivorous mammals and birds were tried as experimental definitive hosts for Heterophyes heterophyes, H. aequalis and H. dispar. The hosts were classified in four categories, by fluke longevity, recovery and size, and the number of uterine eggs (embryonated/unembryonated): (1) Canidae and the cat were highly susceptible hosts for all three species of Heterophyes; (2) several mammals and herons showed a reduced susceptibility to infection (H. aequalis, 6 species; H. dispar, 1 species; H. heterophyes, 0 species); (3) In a group of hosts specific to each trematode, flukes were recovered up to 14 days post infection, but their uterine eggs did not become embryonated; (4) In a fourth category of hosts, chiefly Mustelidae, flukes could not be recovered. Taking also the literature into account it is concluded that man is a highly susceptible host for H. heterophyes, and that probably H. aequalis and H. dispar may reach reproductive maturity in humans also. The described wide host range of H. aequalis appears to be more typical for Heterophyidae than the comparably narrow host range of H. heterophyes.

Animals↗

PubMed1990

Host specificity of Strigiphilus owl lice (Ischnocera: Philopteridae), with the description of new species and host associations.

Three new species and 11 new host associations are described for the cursitans species group of the genus Strigiphilus, the only genus of Mallophaga confined to owls (Strigiformes). The new species are S. schemskei ex Bubo coromandus, S. garylarsoni ex Otus leucotis, and S. petersoni ex Ninox punctulata. This paper completes a taxonomic review of the cursitans species group and includes an updated host-parasite list. The host specificity of the group is reviewed, including features of the natural history of lice and their hosts that may have influenced the evolution of host-parasite associations. Although most members of the cursitans group are host specific, several cases of secondary transfer among ecologically related hosts are apparent. The significance of such transfers is discussed in light of attempts to employ data on host-parasite associations for host systematics.

Animals↗

PubMed1997

Predictive value of host-specific donor helper T-cell precursor frequency for acute graft-versus-host disease and relapse in HLA-identical siblings receiving allogeneic bone marrow transplantation for hematological malignancies.

BACKGROUND: Acute graft-versus-host disease (aGVHD) is still one of the main causes of morbidity and mortality after allogeneic bone marrow transplantation. Attempts to avoid GVHD are associated with an increased risk of relapse, probably because the graft-versus-leukemia effect is also abrogated. It was recently suggested that a high frequency of host-specific donor helper T cell precursors (HTLp) might be predictive of significant aGVHD (grade > or = II). METHODS: We retrospectively studied the frequency of HTLp by means of simplified limiting-dilution analysis to determine its predictive value for aGVHD and relapse. Pre-bone marrow transplantation, host-specific donor HLTp frequencies were analyzed in 32 patients who had received marrow from HLA-identical siblings for hematological malignancies, in terms of aGVHD and relapse. RESULTS: HTLp frequencies were significantly higher in patients who had aGVHD > or = grade II (n=14) than in those without aGVHD (n=18) (P=0.007). Patients who relapsed (n=13) had significantly lower HTLp frequencies than those who did not relapse (n=19) (P<0.0001). The probabilities of relapse (Kaplan-Meier method) when the HTLp frequency was higher and lower than 1/200,000 were 0% and 88%, respectively (P<0.0001). CONCLUSIONS: The definition of HTLp cut-off values predictive of aGVHD and relapse should contribute to donor selection and could open the way to protocols adapting immunomodulation to the likely risk of aGVHD and relapse.

Adolescent↗

PubMed2003

A codon-based model of host-specific selection in parasites, with an application to the influenza A virus.

Parasites sometimes expand their host range by acquiring a new host species. After a host change event, the selective regime acting on a given parasite gene may change as a result of host-specific adaptive alterations of protein functionality or host-specific immune-mediated selection. We present a codon-based model that attempts to include these effects by allowing the position-specific substitution process to change in conjunction with a host change event. Following maximum-likelihood parameter estimation, we employ an empirical Bayesian procedure to identify candidate sites potentially involved in host-specific adaptation. We discuss the applicability of the model to the more general problem of ascertaining whether the selective regime differs in two groups of related organisms. The utility of the model is illustrated on a data set of nucleoprotein sequences from the influenza A virus obtained from avian and human hosts.

Animals↗

PubMed1980

[Detection of the host specificity system in shigellae].

The presence of DNA host specific system in Shigella sonnei 47843 bacteria has been demonstrated. Phage DDIII grown on the cells of Shigella stutzeri 2, in Shigella sonnei 47843 cells is restricted by a factor of 105. Phage T3 of Eco B phenotype as well as DDIII phage is restricted in these cells. This circumstance means that the restriction-modification system of Shigella sonnei 47843 differs in specificity from the well known system E. coli. The results obtained are the second case of host specific system identification in Shigella. The biological properties of the strain (form of the colonies, colicinogenic activity, antibiotic resistance, ability to ferment sugars, etc.) have been studied.

Adsorption↗

PubMed1994

Identification and characterization of a novel Bradyrhizobium japonicum gene involved in host-specific nitrogen fixation.

To understand the genetic mechanism of host specificity in the interaction between rhizobia and their hosts, it is important to identify genes that influence both early and late steps in symbiotic development. This paper focuses on the little-understood genetics of host-specific nitrogen fixation. A deletion mutant of Bradyrhizobium japonicum, strain NAD163, was found to induce effective, nitrogen-fixing nodules on soybean and siratro plants but produced ineffective nodules on cowpea plants. Additional transposon and deletion mutants defined a small region that conferred this phenotype, and this region was sequenced to identify two putative open reading frames (ORFs). Data indicate that only one of these ORFs is detectable in bacteroids. This ORF was termed hsfA, with a predicted protein product of 11 kDa. The transcriptional start site of hsfA was determined and found to coincide with a predicted RpoN-dependent promoter. Microscopic studies of nodules induced by the wild type and hsfA mutants on cowpea and soybean plants indicate that the cowpea mutant nodules are slow to develop. The data indicate that hsfA appears to play a crucial role in bacteroid development on cowpea but does not appear to be essential for nitrogen fixation on the other hosts tested.

Amino Acid Sequence↗

PubMed2003

Host specificity among Ancyrocephalinae (Monogenoidea) of Nebraska sunfish.

This study addressed the problem of local patterns of host specificity among Ancyrocephalinae (Monogenoidea) on bass and sunfish species, when the hosts occur in different species combinations in separate ponds. One hundred fifty-three fish of the Centrarchidae, from 4 study sites in Nebraska, were collected. Host species included bluegill (Lepomis macrochirus), green sunfish (L. cyanellus), largemouth bass (Micropterus salmoides), black crappie (Pomoxis nigromaculatus), white crappie (P. annularis), and rock bass (Ambloplites rupestris). These fish occurred in different species combinations, depending on the pond sampled. Results indicated that several centrarchid species could inhabit the same pond and yet support distinct monogene communities. Clavunculus bursatus, Onchocleidus helicis, O. principalis, and Syncleithrum fusiformis were found only on largemouth bass, regardless of what other centrarchids were present in a particular pond. Haplocleidus dispar occurred on green sunfish, bluegill, largemouth bass, and black crappie, and H. furcatus occurred on both bluegill and largemouth bass. Onchocleidus cyanellus and O. ferox were found on both bluegill and green sunfish. Rock bass were present in only 1 of the 4 ponds, but were not infected with any monogenes, even though co-occurring centrarchids were often heavily infected. Largemouth bass had the most diverse ancyrocephaline communities. The degree of parasite host specificity among these monogenes was inversely related to the diversity of host species present in a particular pond. In general, the parasites were more host specific than might be inferred from the literature; parasite species did not necessarily colonize supposedly receptive host species even when the latter were present, and host relatedness was the major factor in determining whether host species shared a common parasite species.

Animals↗

PubMed2005

Patterns of host specificity and transmission among parasites of wild primates.

Multihost parasites have been implicated in the emergence of new diseases in humans and wildlife, yet little is known about factors that influence the host range of parasites in natural populations. We used a comprehensive data set of 415 micro- and macroparasites reported from 119 wild primate hosts to investigate broad patterns of host specificity. The majority (68%) of primate parasites were reported to infect multiple host species, including animals from multiple families or orders. This pattern corresponds to previous studies of parasites found in humans and domesticated animals. Within three parasite groups (viruses, protozoans and helminths), we examined parasite taxonomy and transmission strategy in relation to measures of host specificity. Relative to other parasite groups, helminths were associated with the greatest levels of host specificity, whereas most viruses were reported to infect hosts from multiple families or orders. Highly significant associations between the degree of host specificity and transmission strategy arose within each parasite group, but not always in the same direction, suggesting that unique constraints influence the host range of parasites within each taxonomic group. Finally characteristics of over 100 parasite species shared between wild primates and humans, including those recognised as emerging in humans, revealed that most of these shared parasites were reported from multiple host orders. Furthermore, nearly all viruses that were reported to infect both humans and non-human primates were classified as emerging in humans.

Animals↗

PubMed2006

The role of body size in host specificity: reciprocal transfer experiments with feather lice.

Although most parasites show at least some degree of host specificity, factors governing the evolution of specificity remain poorly understood. Many different groups of host-specific parasites show a striking correlation between parasite and host body size, suggesting that size reinforces specificity. We tested this hypothesis by measuring the relative fitness of host-specific feather lice transferred to pigeons and doves that differ in size by an order of magnitude. To test the general influence of size, we transferred unrelated groups of wing and body lice, which are specialized for different regions of the host. Lice were transferred in both directions, from a large native host species, the rock pigeon (Columba livia), to several progressively smaller hosts, and from a small native host species, the common ground dove (Columbina passerina), to several larger hosts. We measured the relative fitness (population size) of lice transferred to these novel host species after two louse generations. Neither wing lice nor body lice could survive on novel host species that were smaller in size than the native host. However, when host defense (preening behavior) was blocked, both groups survived and reproduced on all novel hosts tested. Thus, host defense interacted with host size to govern the ability of lice to establish on small hosts. Neither wing lice nor body lice could survive on larger hosts, even when preening was blocked. In summary, host size influenced the fitness of both types of feather lice, but through different mechanisms, depending on the direction of the transfer. Our results indicate that host switching is most likely between hosts of similar body size. This finding has important implications for studies of host-parasite coevolution at both the micro- and macroevolutionary scales.

Animals↗

PubMed1983

Effect of adenovirus on metabolism of specific host mRNAs: transport control and specific translational discrimination.

We have studied the adenovirus-induced inhibition of host cell protein synthesis and the effect of infection on the overall metabolism of host cell mRNA during the late phase of adenovirus infection by following the fate of a number of cellular mRNAs complementary to specific cloned DNA segments. At a time in infection when the rate of total cellular protein synthesis is drastically (greater than 90%) reduced, transcription of specific cellular genes is undiminished. However, the transport of newly synthesized cellular mRNA to the cytoplasm is greatly decreased. This decreased appearance of new mRNA in the cytoplasm cannot account for the observed cessation of cell specific protein synthesis, however, since the concentration of several preexisting cellular mRNAs, including the mRNA for actin, remains unchanged throughout the course of infection. The preexisting mRNA is intact, capped, and functional as judged by its ability to direct protein synthesis in vitro in a cap-dependent fashion. The interruption in host translation appears to operate at the level of initiation directly, since we find that fewer ribosomes are associated with a given cellular mRNA after infection than before infection. Furthermore, the in vivo inhibition of cellular protein synthesis does not appear to be the result of competition with viral mRNA, since conditions which prevent the efficient initiation of translation of viral mRNA (infection with a viral mutant) do not result in the recovery of cell translation. Thus, it appears that a late adenovirus gene product directly mediates a shutoff of host protein synthesis.

Adenoviridae↗

PubMed2005

Phylogeny of the ectomycorrhizal mushroom genus Alnicola (Basidiomycota, Cortinariaceae) based on rDNA sequences with special emphasis on host specificity and morphological characters.

Alnicola (=Naucoria, pro parte) is a mushroom genus of strictly temperate, obligately ectomycorrhizal species, traditionally included in the family Cortinariaceae. Most Alnicola spp. are primarily host specific on Alnus, although a few are mycobionts of Salix or other hosts. The different species of Alnicola exhibit unique morphological (cystidia, pileipellis) and cytological (dikaryotic or monokaryotic hyphae) characters. This makes the genus Alnicola of particular interest for studying the evolution of host specificity and morphological characters in ectomycorrhizal basidiomycetes. We used a combination of classical morphological and phylogenetic methods (rDNA ITS and LSU sequences) to address the following questions: (i) Is Alnicola monophyletic? And (ii) Are characters like host specificity or microscopical structures synapomorphic for certain clades? The study included nearly all currently known European Alnicola sp. Our results demonstrated that, on one hand, the genus Alnicola is polyphyletic, with sistergroup relationships to Hebeloma, Anamika or the clades /Hymenogaster I and /Hymenogaster II. On the other hand, Alnicola splits into three well-supported clades corresponding to the sections Alnicola, Submelinoides, and Salicicolae. The strict host-specificity to Alnus is a derived character and has occurred at least twice. The following morphological characters are synapomorphic for defined clades: the spindle-shaped hymenial cystidia for sect. Alnicola, the hymeniform pileipellis for sect. Submelinoides, and monocaryotic/clampless hyphae for sect. Salicicolae and its sistergroup /Hymenogaster II. As a taxonomical consequence, polyphyly of Alnicola implies that the sects. Submelinoides and Salicicolae need to be segregated from Alnicola.

Basidiomycota↗

PubMed2004

Host specificity and molecular phylogeny of larval Digenea isolated from New Zealand and Australian topshells (Gastropoda: Trochidae).

The maintenance of strict host specificity by parasites when several closely related host species live in sympatry is poorly understood. Species of intertidal trochid snails in the genera Diloma, Melagraphia and Austrocochlea often occur together and are parasitised by a single digenean morphotype (Platyhelminthes, Trematoda), tentatively placed in Opecoelidae. Of the 10 trochid species (6 from New Zealand, 4 from Australia) we examined, six were found to be infected, and the prevalence of infection was as high as 17.5%. We obtained molecular data (mitochondrial 16S and nuclear rDNA internal transcriber spacer 2 sequences, representing 774 bp), to infer phylogenetic relationships amongst these Digenea. Our phylogeny separated the single morphotype into three clearly defined clades (which are almost certainly separate biological species): (i) those infecting two species of Austrocochlea from Tasmania, (ii) those infecting Diloma subrostrata in Otago and Southland, New Zealand, and (iii) those infecting all the parasitised New Zealand topshells (Melagraphia aethiops, D. subrostrata, Diloma nigerrima and Diloma arida) throughout the country. This last group comprised two subclades, one infecting only D. subrostrata and one infecting the other three species. Two D. subrostrata populations were each found to be infected by genetically distinct parasites, yet sympatric populations of the other snails were not necessarily infected. This study is thus the first to reveal cryptic species of digeneans in a single population of a molluscan first intermediate host. We point out also that the degree of host specificity would have been grossly underestimated if, in the absence of our genetic analysis, we had only considered digenean morphology. Our results shed light on the conditions that may favour switching among intermediate hosts in digeneans, and on the presence/absence of host specificity in these parasites.

Animals↗

PubMed2001

Cytokine gene expression in lymph node and spleen of sheep in response to Salmonella infection by two serotypes displaying different host specificity.

In order to investigate the determinism of the host specificity and to better understand the host resistance mechanisms, infections of sheep were performed with either S. abortusovis, serotype specific for ovine species, or with S. dublin, serotype adapted to cattle and accidentally transmissible to human. Following a subcutaneous challenge, S. dublin disseminated more rapidly towards lymphoid tissues than S. abortusovis. However, S. abortusovis tended to persist in spleen more efficiently than S. dublin. Using a quantitative RT-PCR method, the expression level of ovine cytokines genes was measured in the draining lymph node and in the spleen, in the course of infection. Inflammatory cytokine response was characterised by an early and strong increase of IL-1beta and TNFalpha mRNA in both lymphoid organs following S. dublin infection, while S. abortusovis challenge only induced IL-1beta mRNA increase in the spleen at day 3 post-inoculation. Likewise, S. dublin infection provoked a marked increase of IL-12 mRNA and a slight up-regulation of IFNgamma gene transcription in the local lymphoid site, in contrast to S. abortusovis infection. Elsewhere, both serotypes induced a strong and early IL-10 mRNA production and had no effect on IL-4 gene expression. Finally, taken together, these data suggest that the intensity of inflammatory and anti-infectious cytokine responses, but not the type 2 cytokine response, is serotype-dependent. They also suggest that the host-specific serotype, by limiting the host cytokine-mediated defence, could favour its persistence within lymphoid organs.

Animals↗

PubMed1994

The molecular basis of the host specificity of the Rhizobium bacteria.

The interaction between soil bacteria belonging to the genera Rhizobium, Bradyrhizobium and Azorhizobium and leguminous plants results in the induction of a new plant organ, the root nodule. After invading these root nodules via infection threads the bacteria start to fix atmospheric nitrogen into ammonia which is beneficial for the host plant. This symbiotic interaction is highly host-specific in that each rhizobial strain is able to associate with only a limited number of host plant species. The subject of this presentation is the molecular mechanism by which the bacterium determines its host-specific characteristics. This mechanism appears to be based on at least two stages of molecular signaling between the bacterium and the plant host. In the first stage, flavonoids secreted by the plant root induce, in a host specific way, the transcription of bacterial genes which are involved in nodulation, the so-called nod genes. This leads to the second step of the signaling system: the production and secretion of lipo-oligosaccharide molecules by the Rhizobium bacteria. These signal molecules, which are acylated forms of small fragments of chitin, have various discernable effects on the roots of the host plants. One of these effects is the dedifferentiation of groups of cells located in the cortex which leads to the formation of nodule meristems. In their mitogenic activity the bacterial signals resemble several well-known plant hormones like auxins and cytokinins. However, there are two major differences: (i) the bacterial signals lead to the induction of a specific organ and (ii) they are host-specific in that only the signals produced by compatible bacteria are able to induce meristems. The nod genes determine this stage of host specificity by their essential role in the biosynthesis of the signal molecules. They appear to encode enzymes which are involved in the processes of fatty acid biosynthesis, fatty acid transfer, chitin synthesis and chitin modification. I will illustrate the statement that the nod gene products are ideal model enzymes for the study of these important processes because they are not needed in the free-living state of the bacteria.

Base Sequence↗

PubMed1992

Host-specific interleukin-2-secreting donor T-cell precursors as predictors of acute graft-versus-host disease in bone marrow transplantation between HLA-identical siblings.

BACKGROUND: Acute graft-versus-host disease (GVHD) is a serious complication of allogeneic bone marrow transplantation from an HLA-identical sibling. There is no practical test before transplantation that gives sufficient information to predict the degree of allogeneic reactivity between HLA-identical siblings. METHODS: We determined the frequency with which host-specific interleukin-2-secreting donor T-cell precursors occurred in 16 consecutive pairs of HLA-identical siblings before they underwent marrow grafting. The results were correlated with the development of acute GVHD after transplantation. RESULTS: High frequencies of host-specific T-cell precursors (> or = 1 per 100,000) were detectable before transplantation in eight donors whose siblings later had severe (grade II or III) acute GVHD. Among the donors to eight patients with mild (grade 0 or 1) acute GVHD, low frequencies (< 1 per 100,000) were found. CONCLUSIONS: Analysis of the frequency of such cells before transplantation may be a useful predictor of severe acute GVHD in allogeneic bone marrow transplantation between HLA-identical siblings. It is possible that the patients at risk for serious acute GVHD after marrow grafting may benefit from some alternative form of immunosuppressive therapy.

Acute Disease↗