Biomedical subjects

Rosie S Hails

Publications and source records attributed to Rosie S Hails.

7 recordsLinked to original sources

PubMed2006

Host mediated selection of pathogen genotypes as a mechanism for the maintenance of baculovirus diversity in the field.

The genetic diversity of many DNA virus populations in nature is unknown, but for those that have been studied it has been found to be relatively high. This is particularly true for baculoviruses, a family of large double-stranded DNA viruses that infect the larval stages of insects. Why there should be such heterogeneity within these virus populations is puzzling and what sustains it is still unknown. It has long been recognized that some baculoviruses have a relatively wide host range, but the effect of different host species on the genotypic structure of a baculovirus population has received little attention. We provide evidence that infection of different insect species can influence the genetic diversity of a Panolis flammea nucleopolyhedrovirus (PaflNPV) population, isolated from the pine beauty moth. Variable regions of the PaflNPV genome were sequenced and novel ORFs were identified on each of the enlarged fragments. The roles of these orfs and the implications of their presence or absence within different genotypes are discussed. The variable fragments were also labelled with 32P and used as polymorphic genetic markers of genotype abundance. The proportion of polymorphic loci changed after passage in different insect species and this varied among species, suggesting a role for host selection of pathogen genotypes in the field as a mechanism for maintaining genetic diversity. These results have wide-ranging implications for understanding the ecology of insect-virus interactions in the natural environment and the evolution of baculovirus life history strategies.

Animals↗

PubMed2006

An antivector vaccine protects against a lethal vector-borne pathogen.

Vaccines that target blood-feeding disease vectors, such as mosquitoes and ticks, have the potential to protect against the many diseases caused by vector-borne pathogens. We tested the ability of an anti-tick vaccine derived from a tick cement protein (64TRP) of Rhipicephalus appendiculatus to protect mice against tick-borne encephalitis virus (TBEV) transmitted by infected Ixodes ricinus ticks. The vaccine has a "dual action" in immunized animals: when infested with ticks, the inflammatory and immune responses first disrupt the skin feeding site, resulting in impaired blood feeding, and then specific anti-64TRP antibodies cross-react with midgut antigenic epitopes, causing rupture of the tick midgut and death of engorged ticks. Three parameters were measured: "transmission," number of uninfected nymphal ticks that became infected when cofeeding with an infected adult female tick; "support," number of mice supporting virus transmission from the infected tick to cofeeding uninfected nymphs; and "survival," number of mice that survived infection by tick bite and subsequent challenge by intraperitoneal inoculation of a lethal dose of TBEV. We show that one dose of the 64TRP vaccine protects mice against lethal challenge by infected ticks; control animals developed a fatal viral encephalitis. The protective effect of the 64TRP vaccine was comparable to that of a single dose of a commercial TBEV vaccine, while the transmission-blocking effect of 64TRP was better than that of the antiviral vaccine in reducing the number of animals supporting virus transmission. By contrast, the commercial antitick vaccine (TickGARD) that targets only the tick's midgut showed transmission-blocking activity but was not protective. The 64TRP vaccine demonstrates the potential to control vector-borne disease by interfering with pathogen transmission, apparently by mediating a local cutaneous inflammatory immune response at the tick-feeding site.

Amino Acid Sequence↗

PubMed2005

A cross-reactive tick cement antigen is a candidate broad-spectrum tick vaccine.

Truncated constructs of 64P (64TRPs), a secreted cement protein from salivary glands of the tick Rhipicephalus appendiculatus, provided cross-protection against Rhipicephalus sanguineus and Ixodes ricinus, apparently by targeting antigens in the midgut and salivary glands of adults and nymphs, causing mortality. Tick feeding on 64TRP-immunised animals stimulated local inflammatory immune responses (involving basophils, eosinophils, lymphocytes, mast cells, macrophages and dendritic-like cells) that boosted the immune status of vaccinated animals. The vaccine trial results, and antigenic cross-reactivity of 64TRPs with R. sanguineus, I. ricinus, Amblyomma variegatum and Boophilus microplus, indicate the potential of 64TRPs as a broad-spectrum anti-tick vaccine.

Animals↗

PubMed2005

Differential crop damage by healthy and nucleopolyhedrovirus-infected Mamestra brassicae L. (Lepidoptera: Noctuidae) larvae: a field examination.

Baculovirus infection in Lepidoptera can alter both larval mobility and feeding rates, which can in turn affect pathogen transmission and dispersal in the field. We compared the damage to cabbage plants in the field caused by healthy and nucleopolyhedrovirus-infected Mamestra brassicae L. (Lepidoptera: Noctuidae) larvae released as second and fourth instars. There was no significant difference in plant consumption by healthy and infected larvae for the first 4 days after release. From day 5 onwards, infected larvae caused significantly less defoliation. This pattern was similar for larvae at both larval instars. Defoliation was greater for fourth instars throughout the experiment.

Animals↗

PubMed2005

Genes invading new populations: a risk assessment perspective.

One of the concerns raised over the introduction of genetically modified crops is that transgenes will invade populations of wild relatives, causing ecologically significant changes in fitness. In recent years, this has given rise to several studies estimating hybridization rates and the fitness of crop-wild relative hybrids. These studies have established that transgenes are likely to move to F1 hybrids, albeit at low frequency. Hybridization, however, is not synonymous with introgression, and questions remain as to whether particular transgenes will cause ecologically significant changes in recipient plant populations. Research effort should now focus on estimating any changes in the fitness of a population as a consequence of having a transgene, understanding genotype x environment interactions, and deducing the extent to which pathogens and herbivores (transgene targets) regulate wild relative populations. This will involve a combination of manipulative experiments and empirically motivated mathematical models.

Journal Article↗

PubMed2004

The role of food plant and pathogen-induced behaviour in the persistence of a nucleopolyhedrovirus.

Insect baculoviruses can survive between epidemics as infectious particles external to the host. Many pathogens persist in reservoirs, i.e., microhabitats where survival is enhanced, for example due to protection from the degrading effects of UV irradiation. However, the probability of infecting new susceptible hosts is usually reduced. Persistence of pathogens and their movement in and out of reservoirs is an important, albeit little understood, aspect of insect pathogen ecology. This study investigated interactions between the behaviour of infected insect hosts, virus distribution and plant species on the persistence of the winter moth (Operophtera brumata) nucleopolyhedrovirus. Habitat influenced the persistence of infectious baculovirus in the field: virus on Sitka spruce (Picea sitchensis) and oak (Quercus robur) in forested areas retained more infectivity than virus on heather (Calluna vulgaris) in an unshaded habitat. Plant species per se did not directly affect the persistence of virus on the foliage of potted seedlings. Virally infected insects had altered behaviour and moved down plants relative to control insects, whereas in other systems larvae show height-seeking behaviour. Consequently, the majority of virus particles were distributed on plant stems. In two experiments (one using winter moth NPV and one Mamestra brassicae NPV) virus persisted better on plant stems relative to foliage. Neonate larvae were shown to be able to acquire infections from tree stems contaminated with a low level of virus. These data suggest that plant stems may be important reservoirs for between-year persistence of this pathogen. The observed virus-induced changes in host behaviour in winter moth could enhance the viral persistence by increasing the deposition of occlusion bodies in these reservoirs.

Animals↗

PubMed2002

Dual action ectoparasite vaccine targeting 'exposed' and 'concealed' antigens.

Blood-feeding ectoparasites, such as mosquitoes, sandflies and ticks, transmit many disease agents. Their control relies on large-scale, repeated use of chemical pesticides. An alternative, targeted and environmentally friendly approach is to develop anti-ectoparasite vaccines. We describe a vaccine to control ticks that targets an 'exposed' tick saliva antigen and cross-reacts with 'concealed' tick midgut antigens. Ticks feeding on immunised animals induced a cutaneous inflammatory response and increased antibody titer, while engorged ticks died following damage to their midgut. This dual action, acting at the feeding site and in the midgut, offers a self-sustaining strategy for ectoparasite control boosted by natural infestations.

Amino Acid Sequence↗