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D H Kemp

Publications and source records attributed to D H Kemp.

At least 37 records · Page 2Linked to original sources
PubMed1989

Immunologic control of a parasitic arthropod. Identification of a protective antigen from Boophilus microplus.

Cattle can be vaccinated against the tick Boophilus microplus by inducing an immunologic reaction against Ag in the tick gut. The uptake of antibody during feeding leads to severe damage to the parasite. One of the responsible tick gut Ag has now been purified and characterized: the Bm86 Ag. It is a membrane-bound glycoprotein present in very low abundance in extracts of partially engorged adult female ticks. It has an apparent m.w. of 89,000, an isoelectric point of 5.1 to 5.6 and an affinity for wheat germ lectin. Microgram amounts of this Ag are able to induce effective protection in cattle against the parasite, as shown by the decreased survival of ticks on vaccinated cattle and a reduction in engorgement weights and egg laying capacity of the survivors. Antisera to the Ag react with the surface of digest cells in the tick gut. As a result of the reaction with antibody, the endocytotic activity of these cells, which is a critical step in bloodmeal digestion in this tick, is strongly and rapidly inhibited. A number of peptides from this Ag, produced by digestion of the reduced and alkylated protein with endoproteinase lys-C, have been sequenced. One peptide has significant amino acid sequence homology with the epidermal growth factor precursor and a second peptide has homology with a putative protective antigen from Plasmodium falciparum.

Amino Acid Sequence↗
PubMed1989

Vaccination against Boophilus microplus: localization of antigens on tick gut cells and their interaction with the host immune system.

Cattle have been vaccinated against Boophilus microplus with antigens derived from partially fed female ticks. The immune response of the host lyses the gut cells of adult ticks, causing a reduction in the number, weight and reproductive capacity of engorging ticks. This response is different from the immunity that cattle acquire after repeated tick infestation. Evidence is presented that the antigens used in vaccination are located on the plasma membrane of the gut cells and it is unlikely that these antigens are secreted into the host during feeding. Vaccination using such 'concealed' antigens may not encounter the mechanisms of immune evasion that parasites usually demonstrate. In-vitro assays suggest that vaccination immunity is not dependent on the need to stimulate cell-mediated responses. Immunoglobulin G alone, or with the aid of complement, is enough to damage tick gut. The normal function of the one protein antigen isolated so far is unknown but we speculate that it serves some vital function on the cell plasma membrane.

Animals↗
PubMed1988

Vaccination with 'concealed' antigens for tick control.

Ticks are responsible for substantial economic losses to the livestock industry, necessitating intensive use of chemical acoricides in many parts of the world. Problems of chemical residues, cost of acoricides, and development of resistance by ticks, have long been recognized and have helped to stimulate interest in tick control by immunological means (see Box 1). One approach has been to seek ways to enhance the natural immunity often acquired by animals in response to tick infestation. An alternative, discussed here by Peter Willadsen and David Kemp, is to vaccinate with 'concealed' tick antigens not normally encountered by the host, and so stimulate a different immune effector mechanism.

Journal Article↗
PubMed1987

Boophilus microplus (ixodid tick): fine structure of the gut basophilic cell in relation to water and ion transport.

Basophilic cells in the guts of female ticks are derived from the basal remnants of type 2 secretory cells. As viewed by electron microscopy, these cells have microvilli uniformly distributed on the luminal surface, but they lack the abundant pinocytotic vesicles and lysosomes characteristic of digest cells. The cytoplasm is filled with well organized rough endoplasmic reticulum, Golgi complexes and secretory granules. Infoldings of a basal labyrinth extend the contact of the cell with the underlying haemolymph, and there are many mitochondria in the cell processes between folds. This morphology appears to fit the cell for functioning in active water transport across the gut wall. Subsequent to a final rapid phase of engorgement, the basophilic cell reorganizes its cisternae of rough endoplasmic reticulum into whorls and parallel arrays and resumes a secretory role.

Animals↗
PubMed1987

Boophilus microplus: passage of bovine immunoglobulins and albumin across the gut of cattle ticks feeding on normal or vaccinated cattle.

Cattle were vaccinated with antigens from adult female Boophilus microplus and haemolymph was collected from female ticks which had engorged on these animals and on matched control cattle. Radio-immunoassay for bovine plasma proteins in haemolymph from ticks fed on control cattle showed low concentrations of IgG1 and albumin. There was a significant increase in bovine plasma proteins passing across the gut in ticks fed on vaccinated cattle, with an average of 150 times more albumin and four to five times more IgG1 in the haemolymph. Ticks with obviously damaged gut had the highest concentrations of bovine plasma proteins but apparently undamaged ticks from vaccinated cattle also had elevated protein concentrations.

Animals↗
PubMed1986

Continued functioning of the feeding apparatus during moulting of Boophilus microplus as an adaptation of one-host ticks.

Nymphs of the 1-host cattle tick Boophilus microplus remain attached to the host during moulting, but this process is not uniform throughout the tick tissues. The muscles of the pharynx and salivarium remain attached to the cuticle and are functional while the cuticle of the legs has already separated from the underlying epidermis and muscle. The nymphs continue to feed for 2 days after the moulting process in the legs has begun, and they more than double their weight in this time. Mouth-part primordia of the adults develop while the nymphs are still feeding. These adaptations could be an advantage of a 1-host feeding strategy, as they decrease the non-feeding development time spent on the host. In the 3-host tick Haemaphysalis longicornis, which moults off the host, the pharynx, salivarium and legs all begin the moulting process at the same time.

Animals↗
PubMed1985

The isolation of arboviruses including a new flavivirus and a new Bunyavirus from Ixodes (Ceratixodes) uriae (Ixodoidea: Ixodidae) collected at Macquarie Island, Australia, 1975-1979.

Pools of ticks, Ixodes (Ceratixodes) uriae collected between 1975 and 1979 at Macquarie Island, yielded 33 strains of at least 4 different viruses: Nugget virus (Kemerovo group), 1 strain; Taggert virus (Sakhalin group) 9 strains; a previously undescribed flavivirus, related to Central European Tickborne encephalitis virus, for which the name "Gadgets Gully" is proposed, 9 strains; a virus serologically related to the Uukuniemi serogroup, family Bunyaviridae, for which the name "Precarious Point" is proposed, 10 strains. Three isolates were mixtures of Nugget and Gadgets Gully viruses; the remaining virus strain remains unidentified.

Animals↗
PubMed1984

Isolation of a new arbovirus from the tick Argas robertsi from a cattle egret (Bubulcus ibis coromandus) colony in Australia.

A new arbovirus was isolated from ticks of the species A. robertsi collected on 3 January 1980 from trees in which B. ibis coromandus was breeding. The breeding site is located in a swamp at latitude 27 degrees S., longitude 152 degrees E. in south-east Queensland. Larvae, nymphs and adults of A. robertsi were observed to feed on egrets. The serum of 29 out of 37 egrets from the same colony contained neutralizing antibodies to the virus. No information is available on the pathogenicity of this virus for cattle egrets, or other species of bird. Lake Clarendon virus is suggested as the name for this new virus.

Animals↗
PubMed1983

Comparison of cutaneous hyperemia in cattle elicited by larvae of Boophilus microplus and by prostaglandins and other mediators.

Blood flow has been measured in bovine skin following the injection of tick antigens and a number of pharmacological mediators; including histamine, prostaglandins and slow reacting substance of anaphylaxis. The greatest increase in blood flow (20 times normal) was recorded with tick antigens and with prostaglandin F2. This mediator may therefore influence blood flow during immune reactions to ticks and during the rapid ingestion of blood by the ticks.

Animals↗