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New tests for diagnosis of leishmaniasis
216
News & Comment
in Nigeria showed a clinical association between liver size and therapeutic response to antimalarial chemotherapy. In particular, in children aged five years or less, an increase in liver size to at least 125% was associated with a lack of therapeutic response to drugs. SHK
Tick research platform molts to adult stage
Operational and communication networks remain crucial for the continuation of science development. From 1987, the Anaplasmosis–Babesiosis Network (ABN; receiving financial support from the Office of Agriculture, Bureau for Science and Technology of the US Agency for International Development; USAID) functioned as a platform for scientists in tick-transmitted diseases. Because this funding was not continued, the network broke up in 1993. For the past four years, a new initiative to create a forum on ticktransmitted diseases (International Consortium on Ticks and Tick-borne Diseases; ICTTD) has been funded by the European Union DGXII under the INCO.DC programme. The ICTTD, initiated by Gerrit Uilenberg, is coordinated by Frans Jongejan ([email protected]) (Utrecht University, The Netherlands), who was recently appointed as Extraordinary Professor in the Dept of Veterinary Tropical Disease of the Faculty of Veterinary Science by the University of Pretoria. The ICTTD also produces a Newsletter on ticks and tickborne disease with highlights of meetings and an overview of recently published articles on this subject (edited by Uilenberg). The ICTTD programme has now received funding for another four years. Four working groups were created: genome consortium, vaccine development, improved diagnostics and the tick museum. It is felt that such initiatives are crucial for keeping up networks of scientists active in related disciplines. TS
TRENDS in Parasitology Vol.17 No.5 May 2001
New tests for diagnosis of leishmaniasis A highly sensitive PCR-based diagnostic test and a Latex agglutination test for diagnosis of Leishmania have been reported recently. The PCR test, under optimal conditions, can detect as few as ten parasites per ml of human blood (L. Lachaud et al. J. Clin. Microbiol. 39, 613–617, 2001). Four methods of lysis-DNA extraction of whole and buffy coat blood preparations were compared to reach this conclusion. The new Latex agglutination test (KATEX) for detection of leishmanial antigens in the urine of infected patients has been developed by Z.J. Attar et al. (Acta Trop. 78, 11–16, 2001). This test is reported to have 100% specificity, and sensitivity between 68 and 100%. Using human samples, KATEX performed better than any single serological test in predicting Leishmania positivity. SHK
It’s not a mouse, it’s a hamster! A new hamster model for visceral leishmaniasis has been developed that might provide vital insight into the mechanisms of the disease in humans (P.C. Melby et al. J. Immunol. 166, 1912–1920, 2001). The clinical features of Leishmania donovani infection of Syrian hamsters closely resemble human infection; both species experience progressive increases in visceral parasite burden, cachexia, splenomegaly and hypergammaglobulinaemia. The study found that, although a strong Th1-like immune response is initiated in Leishmania-infected hamsters, macrophages in this species fail to produce the effector molecule nitric oxide. The failure of humans to control visceral leishmaniasis is also thought to be because of defective nitric oxide production. In mice, the most commonly used rodent model for leishmaniasis, infection is controlled by macrophage nitric oxide production. SHK
Vaccinia virus-based Plasmodium falciparum vaccine A live recombinant vaccinia virus vaccine for Plasmodium falciparum can stimulate Th1 responses in immunized animals according to a recent study (W. Dong et al. Int. J. Parasitol. 31, 57–62, 2001). Four to six weeks following the immunization of
rabbits, rats and mice with this vaccine, the sera from all three animal groups showed evidence of enhanced production of IL-2 and IFN-γ, as well as an ability to inhibit the growth of Plasmodium falciparum in vitro. The vaccine contains a synthesized hybrid gene encoding proteins CSP, MSA1, MSA2 and RESA, plus IL-1 and tetanus toxoid epitopes (which act as immune enhancers). The benefits of using a live vaccinia virus vaccine include the potential to include multiple and diverse antigens (a crucial factor in malaria vaccination) and the capability to express these in eukaryotic cells. Future studies are directed at testing this vaccine in Aotus monkeys and eventually human clinical trials. SHK
IL-4 involved in regulation of liver damage during schistosomiasis An investigation of the pathology in schistosomiasis has revealed an unexpected role for the cytokine IL-4 in regulating the generation of free radicals in the liver (A.C. La Flamme et al. J. Immunol. 166, 1903–1911, 2001). Normal mice infected with the parasite Schistosoma mansoni show liver enlargement and hepatocyte proliferation during disease resolution. However, in IL-4 ‘knockout’ mice, these responses do not occur, and the mice become severely diseased. Instead of liver proliferation, these mice show an abnormally high accumulation of reactive oxygen and nitrogen intermediates and the antioxidant defenses became dramatically diminished. Both of these phenomena are believed to contribute to prolonged morbidity. SHK
Strawberry fields forever Outbreaks of hepatitis A in the USA in the late 1990s have been linked to consumption of berry-cup dessert in luncheons distributed at schools. A link was further established between the use of frozen strawberry slices to prepare this dessert and the hepatitis outbreak. The strawberries had been grown in Mexico and processed in to frozen slices in the USA. At the same time, outbreaks of cyclosporosis (caused by the recently identified coccidian parasite of humans, Cyclospora cayetanensis) were reported in the USA and Canada, and again strawberries were suspected to be the cause of the spread of the disease; however, further research
http://parasites.trends.com 1471-4922/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved.
News & Comment
in Nigeria showed a clinical association between liver size and therapeutic response to antimalarial chemotherapy. In particular, in children aged five years or less, an increase in liver size to at least 125% was associated with a lack of therapeutic response to drugs. SHK
Tick research platform molts to adult stage
Operational and communication networks remain crucial for the continuation of science development. From 1987, the Anaplasmosis–Babesiosis Network (ABN; receiving financial support from the Office of Agriculture, Bureau for Science and Technology of the US Agency for International Development; USAID) functioned as a platform for scientists in tick-transmitted diseases. Because this funding was not continued, the network broke up in 1993. For the past four years, a new initiative to create a forum on ticktransmitted diseases (International Consortium on Ticks and Tick-borne Diseases; ICTTD) has been funded by the European Union DGXII under the INCO.DC programme. The ICTTD, initiated by Gerrit Uilenberg, is coordinated by Frans Jongejan ([email protected]) (Utrecht University, The Netherlands), who was recently appointed as Extraordinary Professor in the Dept of Veterinary Tropical Disease of the Faculty of Veterinary Science by the University of Pretoria. The ICTTD also produces a Newsletter on ticks and tickborne disease with highlights of meetings and an overview of recently published articles on this subject (edited by Uilenberg). The ICTTD programme has now received funding for another four years. Four working groups were created: genome consortium, vaccine development, improved diagnostics and the tick museum. It is felt that such initiatives are crucial for keeping up networks of scientists active in related disciplines. TS
TRENDS in Parasitology Vol.17 No.5 May 2001
New tests for diagnosis of leishmaniasis A highly sensitive PCR-based diagnostic test and a Latex agglutination test for diagnosis of Leishmania have been reported recently. The PCR test, under optimal conditions, can detect as few as ten parasites per ml of human blood (L. Lachaud et al. J. Clin. Microbiol. 39, 613–617, 2001). Four methods of lysis-DNA extraction of whole and buffy coat blood preparations were compared to reach this conclusion. The new Latex agglutination test (KATEX) for detection of leishmanial antigens in the urine of infected patients has been developed by Z.J. Attar et al. (Acta Trop. 78, 11–16, 2001). This test is reported to have 100% specificity, and sensitivity between 68 and 100%. Using human samples, KATEX performed better than any single serological test in predicting Leishmania positivity. SHK
It’s not a mouse, it’s a hamster! A new hamster model for visceral leishmaniasis has been developed that might provide vital insight into the mechanisms of the disease in humans (P.C. Melby et al. J. Immunol. 166, 1912–1920, 2001). The clinical features of Leishmania donovani infection of Syrian hamsters closely resemble human infection; both species experience progressive increases in visceral parasite burden, cachexia, splenomegaly and hypergammaglobulinaemia. The study found that, although a strong Th1-like immune response is initiated in Leishmania-infected hamsters, macrophages in this species fail to produce the effector molecule nitric oxide. The failure of humans to control visceral leishmaniasis is also thought to be because of defective nitric oxide production. In mice, the most commonly used rodent model for leishmaniasis, infection is controlled by macrophage nitric oxide production. SHK
Vaccinia virus-based Plasmodium falciparum vaccine A live recombinant vaccinia virus vaccine for Plasmodium falciparum can stimulate Th1 responses in immunized animals according to a recent study (W. Dong et al. Int. J. Parasitol. 31, 57–62, 2001). Four to six weeks following the immunization of
rabbits, rats and mice with this vaccine, the sera from all three animal groups showed evidence of enhanced production of IL-2 and IFN-γ, as well as an ability to inhibit the growth of Plasmodium falciparum in vitro. The vaccine contains a synthesized hybrid gene encoding proteins CSP, MSA1, MSA2 and RESA, plus IL-1 and tetanus toxoid epitopes (which act as immune enhancers). The benefits of using a live vaccinia virus vaccine include the potential to include multiple and diverse antigens (a crucial factor in malaria vaccination) and the capability to express these in eukaryotic cells. Future studies are directed at testing this vaccine in Aotus monkeys and eventually human clinical trials. SHK
IL-4 involved in regulation of liver damage during schistosomiasis An investigation of the pathology in schistosomiasis has revealed an unexpected role for the cytokine IL-4 in regulating the generation of free radicals in the liver (A.C. La Flamme et al. J. Immunol. 166, 1903–1911, 2001). Normal mice infected with the parasite Schistosoma mansoni show liver enlargement and hepatocyte proliferation during disease resolution. However, in IL-4 ‘knockout’ mice, these responses do not occur, and the mice become severely diseased. Instead of liver proliferation, these mice show an abnormally high accumulation of reactive oxygen and nitrogen intermediates and the antioxidant defenses became dramatically diminished. Both of these phenomena are believed to contribute to prolonged morbidity. SHK
Strawberry fields forever Outbreaks of hepatitis A in the USA in the late 1990s have been linked to consumption of berry-cup dessert in luncheons distributed at schools. A link was further established between the use of frozen strawberry slices to prepare this dessert and the hepatitis outbreak. The strawberries had been grown in Mexico and processed in to frozen slices in the USA. At the same time, outbreaks of cyclosporosis (caused by the recently identified coccidian parasite of humans, Cyclospora cayetanensis) were reported in the USA and Canada, and again strawberries were suspected to be the cause of the spread of the disease; however, further research
http://parasites.trends.com 1471-4922/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved.