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Biomedical subjects

A G Luckins

Publications and source records attributed to A G Luckins.

At least 55 records · Page 3Linked to original sources
PubMed1989

Evaluation of enzyme immunoassays in the diagnosis of camel (Camelus dromedarius) trypanosomiasis: a preliminary investigation.

Three enzyme immunoassays were used for the serodiagnosis of Trypanosoma evansi in camels in the Sudan in order to evaluate their ability to discriminate between infected and non-infected animals. Two assays were used for the detection of trypanosomal antibodies, one using specific anti-camel IgG conjugate and another using a non-specific Protein A conjugate. The third assay detected the presence of trypanosomal antigens using anti-T. evansi antibodies in a double antibody sandwich assay. Inspection of the frequency distribution of assay results suggested that the ELISA for circulating trypanosomal antibodies using specific antisera and the ELISA for circulating antigens can distinguish between non-infected camels and infected camels exhibiting patent infections or not. The ELISA using Protein A conjugate to bind non-specifically to camel immunoglobulin did not appear to discriminate between infected and non-infected animals.

Animals↗
PubMed1988

Trypanosoma evansi in Asia.

Trypanosoma evansi has the widest geographical range of all the pathogenic trypanosome species and infects domesticated livestock in many countries of South America, Africa and Asia. In spite of this wide distribution, T. evansi has been less intensively investigated than the African tsetse-transmitted trypanosomes and there is correspondingly less information available on the incidence and economic importance of the disease that it causes. Many of the new techniques in immunology and molecular biology, which have provided much fundamental information on the tsetse-transmitted trypanosomes, have yet to be applied to T. evansi. Interest in T. evansi is increasing and a Working Group has now been established to coordinate and promote future research (Box 1). T. evansi is an important aetiological agent of disease in the livestock of Asia; this article evaluates both the historical perspective and our current knowledge of the epidemiology and pathology of T. evansi in this region.

Journal Article↗
PubMed1987

Hyalomma anatolicum anatolicum: the role of humoral factors in the acquisition of host resistance.

A significant degree of resistance to Hyalomma anatolicum anatolicum can be adoptively transferred to naive recipients with immune serum from rabbits repeatedly infected with adult H. a. anatolicum. Ticks fed on recipients of immune serum took longer to become engorged and showed a significant decrease (P less than 0.01) in engorgement weight and oviposition compared with ticks that fed on recipients of normal serum. A direct correlation between resistance and anti-saliva IgG antibodies was indicated by a progressive increase in the degree of resistance and IgG antibody titres following successive tick infestations. Challenge feeding sites on actively sensitised hosts and recipients of immune serum revealed significantly greater infiltration of basophils and eosinophils compared with feeding sites on recipients of normal serum. However, both the degree of resistance and the accompanying cutaneous basophil and eosinophil responses in recipients of immune serum were considerably weaker than those induced by active tick feeding, thus suggesting that nonhumoral (cell-mediated) mechanisms might also be involved in acquired host resistance to H. a. anatolicum.

Animals↗
PubMed1986

Analysis of trypanosome variable antigen types in cultures of metacyclic and mammalian forms of Trypanosoma congolense.

Cultured metacyclic forms of Trypanosoma congolense display a characteristic repertoire of metacyclic variable antigen types (M-VATs) similar to that exhibited in vitro in the tsetse fly. There appeared to be no change in expression of M-VATs in cultures of two stocks of T. congolense even after several passages, cryopreservation or long-term cultivation in vitro. Metacyclic forms transformed into mammalian forms when transferred to cultures of bovine aorta endothelial cells and whilst one stock retained expression of M-VATs without change even after 4 months, the other stock underwent antigenic variation within 14 days of transfer. Analysis of the M-VAT composition of mammalian forms of this stock using monoclonal antibodies showed that although the proportion of mammalian forms expressing certain M-VATs declined considerably, trypanosomes expressing one M-VAT increased proportionally to comprise 50% of the population. In contrast, only small changes were seen in antigen expression in cultures of metacyclic trypanosomes from which mammalian-form cultures were derived. It was possible to produce in vitro, loss and reacquisition of variable antigen surface coat, similar to the differentiation process occurring when bloodstream trypanosomes are ingested by the tsetse fly and eventually develop into metacyclic forms.

Animals↗
PubMed1986

Extrachromosomal inheritance of susceptibility to trypanosome infection in tsetse flies. II. Susceptibility of selected lines of Glossina morsitans morsitans to different stocks and species of trypanosome.

Two lines of Glossina m. morsitans, selected for susceptibility and refractoriness to infection with a single stock of Trypanosoma congolense, have now been shown to be susceptible or refractory to different stocks of T. congolense and, also, to different stocks of T. b. brucei and T. b. gambiense. The mean midgut infection rates of the susceptible line obtained in different experiments with T. congolense, T. b. brucei and T. b. gambiense were, respectively, 66%, 56% and 55%; the corresponding mature (hypopharynx or salivary gland) infection rates were 37%, 23% and 0%. The highest mature infection rates obtained in individual experiments with susceptible flies were 65% (T. congolense) and 40% (T. b. brucei). Mean T. congolense and T. b. brucei midgut infection rates obtained with the refractory line were 29% and 33% respectively, the mature infection rates being 12% and 7%, all significantly lower than the corresponding rates in the susceptible line. Development of midgut infections in susceptible flies appears to take place irrespective of trypanosome stock or form. There is some evidence to suggest that higher infection rates can be obtained with flies infected and maintained on mammals rather than on in vitro feeding systems. Susceptible flies matured a significantly greater proportion of their midgut T. congolense and T. b. brucei infections than did the refractory line, which suggests that maturation of infections is influenced by the susceptibility status of the fly. However, the apparent inability of these flies to develop mature infections of a major T. b. gambiense genetic grouping suggests that maturation of infections established in the midgut is a phenomenon primarily associated with trypanosome genotype.

Animals↗
PubMed1986

Interference between different serodemes of Trypanosoma congolense in the establishment of superinfections in goats following transmission by tsetse.

When domestic ruminants cyclically infected with Trypanosoma congolense are superinfected with a different serodeme of the same species, an interference phenomenon occurs which delays the development of the second cyclical infection. Experiments were carried out to investigate the influence of the time interval between the two infections on the degree of interference and to follow the course of the superinfection clinically, serologically and histologically. Goats infected with tsetse-transmitted T. congolense IL 1587 were either infected simultaneously or 7, 14, 18, 28 or 35 days later with a different serodeme, T. congolense IL 1180. Skin reactions due to superinfection were either absent or smaller in size and delayed in onset compared with control animals undergoing a primary infection with T. congolense IL 1180 which had been initiated by tsetse fly bites. All animals were treated with the trypanocidal drug Berenil 21 days after superinfection and 3 weeks later challenged with T. congolense IL 1180 using tsetse flies. The goats that had been infected simultaneously with the two serodemes were immune to the homologous challenge, but 11 (85%) of the animals that had been superinfected were not. The effect of interference on the host immune response to T. congolense IL 1180 was most marked in animals superinfected at day 7; thereafter there was evidence that the ability to respond immunologically against secondary infection was gradually recovered. Histological examination of skin removed 7 days after a simultaneous infection of goats with two serodemes, showed trypanosomes and a cellular reaction similar to that following infection with a single serodeme. In skin removed 7 days after superinfection of goats that had been infected for 7 days, the cellular response was less pronounced and trypanosomes were not seen, although by 14 to 16 days numerous trypanosomes were present and there was a marked cellular infiltrate. It is postulated that the presence or absence of a factor induced shortly after initiation of a trypanosome infection in the skin of goats might delay parasite development when metacyclic trypanosomes are deposited by tsetse following superinfection.

Animals↗
PubMed1985

In vitro cultivation of Trypanosoma congolense: establishment of infective mammalian forms in continuous culture after isolation from the blood of infected mice.

Bloodstream form trypomastigotes of four cloned stocks of Trypanosoma congolense from West Africa were successfully adapted to continuous in vitro culture at 28 degrees C using bovine aorta endothelial cell monolayers and Eagle's minimum essential medium supplemented with 20% normal bovine serum or foetal calf serum. The trypanosomes maintained in vitro morphologically resembled bloodstream forms and remained infective for vertebrate hosts. They also induced local skin reactions in rabbits and were therefore designated "mammalian forms", possibly resembling parasites which develop extravascularly in the vertebrate host following introduction of metacyclic trypanosomes into the skin by bites of tsetse flies. Mammalian forms of two stocks were allowed to transform to procyclic trypanosomes in order to obtain cultures producing epimastigote and metacyclic stages of T. congolense. Metacyclic trypanosomes produced in this manner were shown to be neutralized by antiserum raised in rabbits against the homologous trypanosome stock transmitted by tsetse flies.

Animals↗
PubMed1985

In vitro cultivation of Trypanosoma congolense: the production of infective forms from metacyclic trypanosomes cultured on bovine endothelial cell monolayers.

After transfer to bovine endothelial cell monolayers cultured in Eagle's minimal essential medium at 28 degrees C or 37 degrees C metacyclic trypanosomes of three cloned stocks of Trypanosoma congolense became morphologically similar to parasites found in the bloodstream of the vertebrate host. The trypanosomes resumed division and grew in close association with the mammalian cells, which were essential for growth. These dividing infective forms had the ability to cause local skin reactions and systemic infections when inoculated intradermally into rabbits. Trypanosomes grown in medium supplemented with foetal calf serum (FCS) eventually differentiated into procyclic forms. No such change occurred in medium supplemented with normal bovine serum. If procyclic forms in FCS were allowed to continue their differentiation at 28 degrees C they eventually produced epimastigotes which gave rise to infective metacyclic trypanosomes once more. It was thus possible to grow and maintain several different developmental stages of T. congolense by varying culture conditions.

Animals↗
PubMed1984

Detection of circulating trypanosomal antigens by enzyme immunoassay.

Antisera raised against Trypanosoma evansi and T. congolense were used in a double antibody sandwich enzyme immunosorbent assay (ELISA) to detect trypanosomal antigens in sera from experimentally infected rabbits and goats. Assays quantitated using reference antigen preparations and the homologous antisera showed that antigens could be detected at protein concentrations of 1.5 microgram ml-1. The antisera also cross-reacted with soluble antigens prepared from T. brucei and T. vivax at similar protein concentrations. In rabbits infected with T. evansi circulating antigens were first detected in serum four to eight days after infection and increased in levels thereafter. However, seven days after treatment with the trypanocidal drug suramin antigens were no longer detectable. In rabbits infected with T. congolense by Glossina morsitans, antigens were detected in serum 14 days after infective fly bite and had disappeared ten days after treatment with homidium chloride. Trypanosomal antigens were also detected in sera from goats infected with T. brucei and T. vivax using the antiserum prepared against T. evansi. Antigens were detected seven days after infection and maximal values observed between ten and 40 days post-infection, thereafter values declined but remained higher than pre-infection levels for up to 130 days.

Animals↗
PubMed1984

In vitro cultivation of Trypanosoma congolense: the production of infective metacyclic trypanosomes in cultures initiated from cloned stocks.

Glossina morsitans were infected with two cloned stocks of T. congolense. The proboscides, foreguts and midguts of infected flies were then used as sources of trypanosomes in vitro at 28 degrees C in the presence of bovine dermal collagen explants. Cultures were established in which trypanosomes differentiated into adhering colonies of epimastigote forms which could then be maintained and subcultured in Eagle's Minimum Essential Medium supplemented with foetal calf serum for over 40 weeks. Within 2-4 weeks of establishment of each culture or subculture the epimastigote trypanosomes differentiated into metacyclic trypanosomes which could be harvested from supernatant medium at concentrations of 1 X 10(5)-3 X 10(6) parasites/ml. These organisms were used to induce the formation of local skin reactions in rabbits. Successful cultivation of infective trypanosomes appeared to depend on the initial adhesion of the parasites to the surface of the flask where they subsequently differentiated first into epimastigote and then to metacyclic forms.

Animals↗
PubMed1983

Infection, immunity and the development of local skin reactions in rabbits infected with cyclically-transmitted stocks of Trypanosoma congolense.

The development of local skin reactions following bites by tsetse flies (Glossina morsitans) infected with Trypanosoma congolense was observed in normal rabbits, in rabbits with concurrent infections with T. congolense and in rabbits challenged after immunization by infection and treatment. Local reactions developed in normal rabbits within seven days of fly bite and were resolved by approximately 19 days after infection. In rabbits with concurrent infections no typical local reactions developed when they were bitten by infected tsetse flies. By allowing a single infected fly to bite a rabbit sequentially it was established that suppression of reaction development to homologous secondary challenge occurred within three to eight days of primary infection. Suppression of reaction development also occurred in infected rabbits challenged with an antigenically heterologous trypanosome stock within 14 to 18 days of primary infection, suggesting that reaction suppression is not associated with the specific immune response. It was also found that no neutralizing antibodies had developed against the parasites used for secondary infection by 28 days post-challenge. Rabbits were immunized by allowing an infected tsetse fly to feed on a rabbit and seven days later, when local reactions had appeared, treating it with homidium chloride. All rabbits challenged within 75 days of immunization by a tsetse fly infected with a homologous trypanosome stock resisted re-infection and some animals were immune up to 300 days after treatment. In most of the immunized animals specific neutralizing antibody activity against homologous parasites was low, suggesting that local expression of immunity in the skin might be more important in resistance to cyclically transmitted infections than serum antibodies. No local reactions developed on immune rabbits challenged with a homologous trypanosome stock but immunized rabbits challenged with heterologous trypanosome stocks developed typical local reactions.

Animals↗
PubMed1983

Interference with anti-trypanosome immune responses in rabbits infected with cyclically-transmitted Trypanosoma congolense.

Rabbits were infected with two clones of antigenically distinct stocks of Trypanosoma congolense transmitted through Glossina morsitans. Local skin reaction development and the appearance of neutralizing antibodies were followed in animals infected with one or other of the trypanosome stocks, with both stocks simultaneously or with both stocks consecutively. There was little difference in local skin reaction development on rabbits infected with a single stock or with both stocks simultaneously but, in rabbits exposed to a heterologous stock 14 or 21 days after a primary infection reactions were reduced in size or completely absent. Neutralizing antibodies against metacyclic-derived trypanosomes were detected 21 days after infection in animals infected with a single trypanosome stock and, in rabbits infected with both stocks simultaneously, antibodies against each stock were also detected 21 to 28 days after infection. In rabbits challenged 14 or 21 days after primary infection the appearance of trypanocidal antibodies against the stock used for challenge was delayed from 28 to 49 days.

Animals↗
PubMed1982

Detection of antibodies to Trypanosoma cruzi in the South American opossum (Didelphis marsupialis).

Stocks of Trypanosoma cruzi belonging to two different zymodemes, one usually associated with silvatic reservoir hosts and the other not normally found in wild reservoir hosts, were used as sources of diagnostic antigens in enzyme-linked immunosorbent assays for the detection of antibodies to T. cruzi in Didelphis marsupialis. Both antigen preparations reacted with antibodies in sera from animals found to be infected by conventional parasitological techniques and also in sera from a proportion of the remaining animals in which it was not possible to detect trypanosomes.

Animals↗
PubMed1982

Presence of serum agglutinins to Campylobacter sputorum subspecies mucosalis in pigs.

Pigs affected with intestinal adenomatosis had agglutinating antibodies to Campylobacter sputorum subspecies mucosalis. The titres obtained varied, depending on the strain used as antigen and appeared to rise with the age of the affected animal. Examination of sera from experimental animals showed that pigs between 30 and 77 days old rarely had antibody, even when they had been exposed to infection. Evidence is also presented indicating that the serological response is specific and that in a limited examination of sera derived from pigs at slaughter almost all animals had high levels of antibody.

Abattoirs↗
PubMed1981

Cultivation of infective forms of Trypanosoma congolense from trypanosomes in the proboscis of Glossina morsitans.

Two stocks of Trypanosoma congolense were established in culture at 28 degrees C using trypanosomes from the proboscides of infective Glossina morsitans. Successful primary cultures were initiated by placing an infected tsetse proboscis beside a bovine dermal collagen explant in Eagle's minimum essential medium supplemented with foetal calf serum. The trypanosomes multiplied rapidly in the medium and also gradually formed an adherent layer o the plastic surface of the culture vessel. Three primary cultures produced organisms infective for mice from 14, 20 and 35 days after initiation and thereafter continuously until days 76, 76 and 52 when they were discarded. Four attempts to initiate infective cultures using infected tsetse proboscides in medium without dermal explants were unsuccessful. When trypanosomes from primary cultures were placed in culture medium with proboscides from uninfected tsetse flies, the parasites multiplied, formed an adherent layer in the culture flasks and were seen in the proboscides within 24 h. A line of 1 stock was serially sub-passaged in this way 4 times during a period of 215 days. Infectivity titrations in mice indicated that primary and sub-passaged cultures each contained similar numbers of infective organisms. Another line of the same stock was also sub-passaged 4 times in medium alone over a period of 186 days. These sub-cultures again retained infectivity for mice, but titrations showed a decrease in infective organism production in the 4th sub-culture. Primary and sub-passaged cultures all included a variety of morphologically different developmental forms of T. congolense, closely resembling those described in the labrum and hypopharynx of Glossina by previous workers. Short metacyclic-like trypanosomes and organisms with proteinaceous surface coats were present in infective cultures. Cultures were successfully re-established after cryopreservation at -196 degrees C and retained the ability to produce infective organisms.

Animals↗