Biomedical subjects

T R Burkot

Publications and source records attributed to T R Burkot.

At least 37 records · Page 2Linked to original sources

PubMed1996

A novel 95-kilodalton antigen of Wuchereria bancrofti infective larvae identified by species-specific monoclonal antibodies.

CBA and BALB/c mice produced polyspecific and monospecific polyclonal antibody responses, respectively, following immunization with Wuchereria bancrofti stage-3 larvae. Two monoclonal antibodies (MAbs) were produced from the immunized BALB/c mouse. These MAbs (both isotype M) recognized a previously undescribed highly expressed W. bancrofti antigen present in stage-3 larvae. The epitopes bound by the MAbs appear to be species specific for W. bancrofti since the MAbs did not bind to antigens of either nine other nematode species or two vector species in Western blots (immunoblots). Phosphorylcholine epitopes, responsible for immunological cross-reactivity among nematodes, were identified only on a 200-kDa antigen and not on the 95-kDa molecule. The targets of these immunoglobulin M MAbs are not carbohydrate epitopes.

Animals↗

PubMed1996

Outer surface protein C (OspC), but not P39, is a protective immunogen against a tick-transmitted Borrelia burgdorferi challenge: evidence for a conformational protective epitope in OspC.

Outbred mice were immunized with the soluble fraction of a crude Escherichia coli lysate containing either recombinant outer surface protein C (OspC or P39 of Borrelia burgdorferi B31 (low passage). Following seroconversion, the mice were challenged with an infectious dose of B. burgdorferi B31 via the natural transmission mode of tick bite. Three mice immunized with P39 were not protected; however, all 12 of the recombinant OspC-immunized mice were protected from infection as assayed by culture and serology. Although OspC has been shown to be a protective immunogen against challenge with in vitro-cultured borrelia administered by needle, this study is the first to demonstrate OspC effectiveness against tick-borne spirochetes. Following feeding, all ticks still harbored B. burgdorferi, suggesting that the mechanism of protection is not linked to destruction of the infectious spirochete within the tick. In a separate experiment, groups of four mice were immunized with protein fractions from B. burgdorferi B31 purified by preparative gel electrophoresis in an attempt to identify potential protective antigens. Many of these mice developed high-titer-antibody responses against OspC, but curiously the mice were susceptible to B. burgdorferi infection via tick bite. These results suggest that the protective epitope(s) on OspC is heat sensitive/conformational, a finding which has implications in vaccine development.

Animals↗

PubMed1996

Ability of experimentally infected chickens to infect ticks with the Lyme disease spirochete, Borrelia burgdorferi.

Chickens were used as a laboratory model to determine the conditions affecting the ability of birds to infect ticks with Lyme disease spirochetes. Chicks (Gallus gallus) were exposed to 12 nymphal Ixodes scapularis at one week or three weeks of age. Xenodiagnostic larval ticks fed these birds at weekly intervals thereafter. Chicks exposed to infected nymphs at one week of age infected 87% of larvae at three weeks of age, but only infected 3% of larvae at four weeks and 0% of larvae at five weeks. Chicks exposed to nymphs at three weeks of age infected only 12% of larvae at four weeks, and 0% thereafter. Thus, experimentally infected chicks can infect larval ticks, but only for a brief interval after exposure. Young chicks are more infectious than older chickens. The immune response of infected chicks was rapid and directed against diverse antigens.

Animals↗

PubMed1995

The Lyme disease vaccine candidate outer surface protein A (OspA) in a formulation compatible with human use protects mice against natural tick transmission of B. burgdorferi.

Development of a vaccine for the Lyme disease spirochete, Borrelia burgdorferi, has focused on the bacterial lipoprotein, major outer surface protein A (OspA). With few exceptions, testing of OspA vaccines in animal models has involved challenge with needle inoculation of cultured spirochetes. Recombinant OspA proteins from two OspA divergent strains of B. burgdorferi were tested for their vaccine potential in three different strains of mice challenged with laboratory reared ticks with a high rate of B. burgdorferi infection. All formulations of the B. burgdorferi sensu stricto derived OspA vaccine protected all strains of mice when challenged by ticks infected with an OspA homologous strain of the spirochete, whereas heterologous OspA from B. afzelii did not protect. Furthermore, ticks feeding on protected mice had reduced OspA levels compared to unvaccinated controls.

Animals↗

PubMed1995

The value of vector-based estimates of malaria transmission.

Estimating malaria transmission in the human is fraught with problems of reconciling clinical illness with parasitological status. It follows that there is a role for entomological assessments as an independent outcome variable and as a process indicator. Advances in DNA technology have expanded our capacity to identify vectors rapidly, while immunoassays allow the inoculation rate to be measured simultaneously in a number of villages with a precision 3-fold greater than measurements of vectorial capacity. The rapid specific identification of parasites in vectors has been utilized to estimate survivorship in mosquitoes per extrinsic incubation period (EIP), circumventing the need for estimates of survivorship per feeding cycle, lengths of feeding cycles or the length of the EIP. While lack of accuracy does not universally preclude the utility of estimates of the components of vectorial capacity in serving as relative estimates of transmission, particularly as process indicators, more accurate estimates of these parameters, particularly for density-dependent variables, may diminish the associated bias in their measurement. When this is accomplished, we will come closer to obtaining true rather than relative estimates of transmission.

Animals↗

PubMed1994

Quantitation of the Borrelia burgdorferi outer surface protein A in Ixodes scapularis: fluctuations during the tick life cycle, doubling times, and loss while feeding.

The presence of outer surface protein A (OspA) as a marker for Borrelia burgdorferi in Ixodes scapularis ticks was monitored with an OspA antigen-capture ELISA. The OspA ELISA, with a sensitivity of 30 spirochetes (8 fg), was not affected by the presence of either recently blood-fed or flat tick homogenates. Median spirochete equivalent levels as high as 16,000 in larvae, 55,000 in attached nymphs, and 10,000 in unfed adults were observed. Estimates of OspA doubling times ranged from a maximum of 140 h in larvae to as short as 17.5 h during nymphal attachment to the host. Spirochete equivalents in nymphs fell by 3 x 10(4) spirochete equivalents (54% of total OspA) in the last 12 h of attachment to mice but rose after detachment. Each OspA-positive I. scapularis nymph, regardless of spirochete equivalent density or length of attachment, successfully transmitted B. burgdorferi to a mouse.

Animals↗

PubMed1994

DNA probes for identifying the members of the Anopheles punctulatus complex in Papua New Guinea.

Genomic DNA probes were made for five members of the Anopheles punctulatus complex of mosquitoes found in Papua New Guinea. Specific DNA probes were developed for An. punctulatus, An. koliensis, and three sibling species, An. farauti No. 4, An. farauti No. 5, and An. farauti No. 6, by differentially screening total genomic DNA libraries of individual species and sibling species with homologous DNA against heterologous DNA labeled with 32P. Probes ranged from 273 to 630 bp. Identification of species can be made from squash or dot blots using only a segment of the mosquito (i.e, head, thorax, abdomen, or even legs), allowing for concurrent analysis of the remainder of the mosquito for other epidemiologic characteristics.

Animals↗

PubMed1994

Field trial of an outer surface protein A (OspA) antigen-capture enzyme-linked immunosorbent assay (ELISA) to detect Borrelia burgdorferi in Ixodes scapularis.

Field-collected adult male Ixodes scapularis from Westchester County, New York were bisected and Borrelia burgdorferi infection rates were ascertained by both a direct fluorescent antibody test and an outer surface protein A (OspA) antigen-capture enzyme-linked immunosorbent assay (ELISA). Both assays gave identical antigen positivity rates with 89% concordance between the two assays. Storing dried ticks before ELISA analysis had no significant effect on the ability of the ELISA to determine the presence of OspA compared with assaying live ticks. The OspA antigen positivity rate for dried ticks was 49% compared with 53% for live ticks, with mean OspA antigen spirochete equivalents of 3,388 and 2,823 for dried and live ticks, respectively.

Animals↗

PubMed1994

Quantitative sampling of immature Aedes aegypti in metal drums using sweep net and dipping methods.

The behavior of aquatic stages of Aedes aegypti was evaluated in 200-liter metal drums to develop improved surveillance. When known numbers of larvae recovered with a rectangular net and with a standard dipper were compared, all stages except 1st instar were most numerous in the top 1/3 of the drum. Water temperature was the only significant variable affecting the vertical distribution of 4th-instar larvae; light intensity and pH were nonsignificant factors. Rust in the water was also thought to influence distribution towards the surface layer. When 100-400 immatures were released into a full drum, immatures were detected by sweeping and dipping the surface layer on 93.3 and 72.9% of trials, respectively. The correlation coefficients (r) of recoveries of known numbers of immatures by sweeping and dipping varied from 0.92 to 0.98 and from 0.38 to 0.89, respectively. The coefficients of variation were 2-5 times smaller for sweeping than for dipping. Recoveries from dipping were shown to be affected by the water volume in the drum. Counts of 4th-instar larvae from one sweep around the top are sufficient to assess productivity in drums.

Aedes↗

PubMed1993

The major histocompatibility complex-restricted response of recombinant inbred strains of mice to natural tick transmission of Borrelia burgdorferi.

The causative agent of Lyme disease, Borrelia burgdorferi, is transmitted by ticks of the Ixodes ricinus complex. In this study, we report the antibody response of recombinant inbred strains of mice of the H-2, b, d, and k haplotypes, infected with B. burgdorferi as a result of exposure to infected I. dammini. The patterns of antibody response assayed by Western blot analysis indicate significant major histocompatibility complex (MHC) restriction to bacterial antigens within the first 2 mo of infection in mice. Other bacterial antigens induce a significant response across the MHC haplotypes tested when assayed on the same bacterial strain used to transmit the infection, but do not crossreact with the same proteins derived from heterologous strains of B. burgdorferi. No response to outer surface protein A was detected at any time during the 60-d period we analyzed this infection. A third group of bacterial antigens appear to generate a MHC-nonrestricted response, and this lack of restriction is maintained when assaying the crossreactivity of the response with other strains of B. burgdorferi. These proteins may provide more accurate diagnostic probes than those currently in use. Finally, there appears to be a significant difference in the expression of most bacterial antigens when the spirochete is cultured for many passages since the same strain of bacterium isolated from low-passage and high-passage preparations exhibit different banding patterns in Western blots when assayed with the same sera.

Animals↗

PubMed1993

Impact of permethrin-impregnated mosquito nets compared with DDT house-spraying against malaria transmission by Anopheles farauti and An.punctulatus in the Solomon Islands.

In villages of northern Guadalcanal in the Solomon Islands, where the predominant malaria vector is An.farauti No. 1 and An.puctulatus is also involved, malaria transmission rates were compared for three zones: (1) non-intervention: 438 people in seventeen villages; (2) residual DDT house-spraying two cycles per year: 644 people in thirty villages; (3) bednets impregnated with permethrin 0.5 g/m2 twice per year, used by 580 people in sixteen villages. Regular DDT spraying in zones 1 and 3 had been withdrawn 18 months previously. Malariological blood smear surveys of children aged 1-9 years in August 1986 to January 1987 showed a mean baseline malaria parasite rate of 38% (32/84). By February 1988, 18 months after introduction of impregnated bednets, the Plasmodium falciparum infection rate in children was lowest in the zone using impregnated bednets (21% of 29), intermediate in the untreated zone (29% of 34) and highest in the DDT zone (46% of 53), but these differences were not statistically significant. P. vivax infection rates were 9-14%. Using ELISA tests for malaria circumsporozoite antigen in the vectors, overall positivity rates were 0.7% of 49,902 An.farauti and 2.54% of 118 An.punctulatus, comprising 228 P.falciparum and 124 P.vivax infections. In the study zones, vector positivity rates were 0.93% of 31,615 An.farauti in the untreated zone; 0.32% of 16,883 An.farauti in the DDT zone; 0.07% of 1404 An.farauti and 2.54% of 118 An.puctulatus in the impregnated bednet zone. here was no significant correlation between malaria parasite rates in the vectors and the children.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

An OspA antigen-capture enzyme-linked immunosorbent assay for detecting North American isolates of Borrelia burgdorferi in larval and nymphal Ixodes dammini.

An antigen-capture enzyme-linked immunosorbent assay (ELISA) was developed for detecting North American isolates of Borrelia burgdorferi in larval, nymphal, and adult ticks. The assay uses an anti-OspA monoclonal antibody (H5332) for antigen capture and biotin-labelled polyclonal sera with streptavidinhorseradish peroxidase for signal generation. The assay recognized 15 of 15 North American B. burgdorferi isolates and did not cross-react with spirochete antigens of Borrelia hermsii, Borrelia turicatae, Borrelia coriaceae, or Borrelia parkeri, or with tick antigens of Ixodes dammini, Ixodes scapularis, Ixodes pacificus, Ixodes cookei, Ixodes angustus, or Ambylomma americanum. The assay, with a sensitivity of less than 150 spirochetes, can detect infections in larval, nymphal, and adult ticks. In addition to fresh ticks, B. burgdorferi infections in ticks stored frozen, dried, or in 70% ethanol can be determined with the assay.

Animals↗

PubMed1992

Development and evaluation of an enzyme-linked immunosorbent assay for Plasmodium vivax-VK247 sporozoites.

An enzyme-linked immunosorbent assay (ELISA) for the Plasmodium vivax-VK247 (variant) circumsporozoite (CS) protein was developed and evaluated using sporozoites produced by feeding mosquitoes on Thai patients with parasitologically confirmed P. vivax infections. The ELISA had a detection threshold of fewer than 50 sporozoites. Using this assay in conjunction with an ELISA for the VK210 polymorph, nearly 16% of the 235 P. vivax cases produced sporozoites positive only for the variant; 69% produced sporozoites positive only in the VK210 assay; and 15% were positive in both assays, indicating mixed infections. Twelve cases (5%) produced sporozoites negative in one assay and with unexpectedly low activity in the other ELISA, indicating the possibility of other CS protein polymorphs.

Amino Acid Sequence↗

PubMed1992

The population dynamics in mosquitoes and humans of two Plasmodium vivax polymorphs distinguished by different circumsporozoite protein repeat regions.

The population dynamics of two Plasmodium vivax polymorphs were studied over a two-year period in a village in a hyperendemic area of Papua New Guinea in both the mosquito and human populations. Strains of P. vivax were distinguished by different circumsporozoite (CS) protein repeats, the VK210 (classic) and the VK247 (variant) polymorphs. In 1986, 34% of P. vivax CS protein-positive mosquitoes were of the VK247 type. Although the proportion of P. vivax sporozoite antigen-positive mosquitoes compared with all sporozoite-positive mosquitoes did not change from 1986 to 1987, the proportion of P. vivax-positive mosquitoes of the VK247 polymorph decreased significantly from 34% to 11% (5 of 45) in 1987. In 1986, 61% (47 of 77) of humans tested had IgGs that recognized the VK247 CS repeat, while only 26% (22 of 84) had IgGs that recognized the VK210 CS repeat. The observed fluctuation in the proportion of the two P. vivax CS protein polymorphs recorded in the mosquito population from 1986 to 1987 is consistent with a hypothesis of selection by humoral immune pressure on the VK247 strain.

Adolescent↗

PubMed1991

The Anopheles punctulatus complex: DNA probes for identifying the Australian species using isotopic, chromogenic, and chemiluminescence detection systems.

Isotopic and enzyme-labeled species-specific DNA probes were made for the three known members of the Anopheles punctulatus complex of mosquitoes in Australia (Anopheles farauti Nos. 1, 2, and 3). Species-specific probes were selected by screening total genomic libraries made from the DNA of individual species with 32P-labeled DNA of homologous and heterologous mosquito species. The 32P-labeled probes for A. farauti Nos. 1 and 2 can detect less than 0.2 ng of DNA while the 32P-labeled probe for A. farauti No. 3 has a sensitivity of 1.25 ng of DNA. Probes were then enzyme labeled for chromogenic and chemiluminescence detection and compared to isotopic detection using 32P-labeled probes. Sequences of the probe repeat regions are presented. Species identifications can be made from dot blots or squashes of freshly killed mosquitoes or mosquitoes stored frozen, dried, and held at room temperature or fixed in isopropanol or ethanol with isotopic, chromogenic, or chemiluminescence detection systems. The use of nonisotopic detection systems will enable laboratories with minimal facilities to identify important regional vectors.

Alkaline Phosphatase↗

PubMed1991

Evaluation of monoclonal antibodies against Plasmodium vivax sporozoites for ELISA development.

Nine monoclonal antibodies (MAbs) developed against Plasmodium vivax (Grassi & Feletti) salivary gland sporozoites were evaluated for use in an enzyme-linked immunosorbent assay (ELISA), using sporozoites developed in Anopheles dirus Peyton & Harrison An. gambiae Giles and An.maculatus Theobald. Four of the antibodies were unsuitable due to the low sensitivity of the resulting assays or the requirement for high concentrations of capture antibody. An additional two MAbs were rejected because they resulted in assays with high background absorbance, attributed to self-binding. Of the three remaining MAbs, the use of Navy vivax sporozoite (NVS) 3 resulted in an ELISA with the highest sensitivity and the lowest concentration requirement for capture antibody. Assay sensitivity varied with sporozoite strain indicating possible quantitative epitope heterogeneity. None of the MAbs cross-reacted with the heterologous sporozoites tested by immunofluorescence antibody assay (IFA). The IFA activity was not an indicator of ELISA sensitivity. The use of MAb NVS 3 in a standardized ELISA method resulted in an assay 10 times more sensitive than reported previously for P. vivax sporozoites, with a detection limit of fewer than 100 sporozoites per mosquito.

Animals↗

PubMed1991

Fine specificities of monoclonal antibodies against the Plasmodium falciparum circumsporozoite protein: recognition of both repetitive and non-repetitive regions.

The fine specificities of 6 monoclonal antibodies (MoAbs) raised against the circumsporozoite (CS) protein of the human malaria parasite, Plasmodium falciparum, were defined by their binding to a series of overlapping octapeptides corresponding to the 7G8 variant of the CS protein. The precise specificities of the MoAbs to the immunodominant NANP repeat region were elucidated by their binding to all possible 4, 5, 6, 7 and 8 amino acid peptides in this region. All 6 MoAbs recognized the NANP repeats. In addition all MoAb bound to nonrepetitive sites with 4 of the 6 MoAbs recognizing known functional sites outside the repeat region including sites required for T cell recognition and hepatocyte invasion. Antibody pressure may therefore be responsible for generating the epitope variation observed at T cell sites. The multiple specificities for all the MoAbs suggests that the repeat region may act as an internal immunological 'smokescreen' by competing more effectively for antibody binding compared to single epitope copy functional sites located outside the repeat region.

Amino Acid Sequence↗

PubMed1990

The prevalence of naturally acquired multiple infections of Wuchereria bancrofti and human malarias in anophelines.

Malaria and filaria infection rates were determined for anopheline mosquitoes collected whilst biting and resting in village houses in Papua New Guinea. The number of anophelines infected with both parasites was greater than expected from the infection rates of each parasite and this difference was significant in resting collections. The excess of multiply infected mosquitoes is probably a result of a vector population composed of individuals with differing numbers of opportunities to become infected. Malaria-positive Anopheles punctulatus from resting catches had a significantly greater number of Stage 3 Wuchereria bancrofti larvae than malaria-negative mosquitoes. However, multiply infected mosquitoes appear to suffer greater mortality than non-infected or singly infected mosquitoes when the filarial worm reaches the third stage. Any potential increase in transmission resulting from multiple infections is thereby offset by a greater mortality rate in these mosquitoes.

Animals↗