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Why are the French different from the British?
News & Comment
TRENDS in Parasitology Vol.17 No.10 October 2001
467
recognized by antiserum of sheep immunized against H. contortus, suggesting that vaccination against H. contortus might induce immunity against T. circumcincta. Although protection against homologous challenge was found, no cross-protection against T. circumcincta, Trichostrongylus axei or Cooperia oncophora was observed [Smith, W.D. et al. (2001) Parasite Immunol. 23, 203–211]. Unexpectedly, vaccination of sheep with equivalent glycoproteins of T. circumcincta significantly reduced worm egg output in sheep that were challenged with H. contortus, whereas no protection against homologous infection was induced. The authors suggest that protection is related to the amount of blood ingested by H. contortus, which is likely to exceed that ingested by T. circumcincta. TS
falciparum infection. Parasight detects the presence of P. falciparum-specific histidinerich protein 2 by using an antigen-capture immunochromatographic strip format. Overall, the sensitivity of Parasight for P. falciparum was 95%, ranging from 83% at low parasite densities (1–500 parasites µl−1) to 98% at high densities (>5000 parasites µl−1). The specificity of the device was 86%. SHK
In Brief
Hubble, bubble, Toll and trouble
A hitherto unrecognized role for Toll-like receptors in initiating immunity against Trypanosoma cruzi was recently identified. M. Campos et al. [(2001) J. Immunol. 167, 416–423] found that highly purified glycosylphosphatidylinositol (GPI) anchors from T. cruzi are potent activators of Toll-like receptor 2 (TLR-2) from both mouse and human origin. These findings were initiated using TLR-2-transfected Chinese hamster ovary-K1 cells, which became activated on exposure to subnanomolar concentrations of trypomastigote-derived GPI anchors. Protozoan-derived GPI anchors were also effective, but only at higher concentrations. Experiments with macrophages from TLR-2 knockout mice showed that TLR-2 expression appears to be essential for GPI anchor-induced upregulation of interleukin 12, tumor necrosis factor α and nitric oxide. The activation of TLR-2 is thought to initiate host innate defense mechanisms and inflammatory responses during protozoan infection and might provide new strategies for immune intervention. SHK
Vampires only For a helminth vaccine to be commercially attractive, it would preferably protect against a range of gastrointestinal helminths. Membrane glycoproteins derived from the gut wall of Haemonchus contortus, most of which have proteolytic activity, successfully protected sheep against haemonchosis. Polypeptides from another gastrointestinal helminth, Teladorsagia circumcincta, were also http://parasites.trends.com
RADical new gene identified in Leishmania The identification of a new gene in Leishmania will open the doors to future research into the contribution of homologous recombination to virulence in this pathogen. The LmRAD51 gene identified by Paul McKean et al. [(2001) Mol. Biochem. Parasitol. 115, 209–216] in Leishmania major encodes a 377-amino-acid polypeptide that is highly homologous to the Rad51 family of proteins. This gene was below the level of detection in exponentially growing cultures of Leishmania, but could be induced at the mRNA and protein level following exposure to the DNA-damaging agent phleomycin. LmRAD51 is one of the first examples of a Leishmania gene that is induced by DNA damage. Based on studies of similar genes in other organisms, LmRAD51 probably plays a central role in homologous recombination and DNA repair. SHK
A new malaria diagnostic device The sensitivity and specificity of a new malaria rapid diagnostic test ‘Parasight’ has been reported. J. Forney et al. [(2001) J. Clin. Microbiol. 39, 2884–2890] performed their study at outpatient malaria clinics in Peru and Thailand, utilizing duplicate, blind samples as the reference standard for microscopic evaluation of the performance of the device in diagnosis of Plasmodium
Why are the French different from the British? Parasites affect the physiological and immunological systems of their host to increase the chance of successful transmission. It has been reported that Toxoplasma gondii, which also infects the brain, can change the behaviour of the host. When rats are infected with T. gondii, the propensity to explore novel stimuli in their environment was increased, whereas there was no effect on social status in the group or mating success. This selective change in behaviour would increase the chance of rats to be captured by cats and consequently increase the transmission of the parasite. Manuel Berdoy from the University of Oxford, UK, states that such effects of T. gondii on the brain could explain the reports of altered personality and IQ levels in some humans following parasite infection. Interestingly, ~22% of the UK population carries the organism, whereas in France the level is 87% (source: www.webmesh.co.uk). TS
Parasites, poo and PCR A surprising report suggests that PCR-based examination of dried feces can be an effective tool for surveillance of trypanosome infection of triatome bugs in residential buildings. S. Hamano et al. [(2001) Parasitol. Int. 50, 135–138] used primers specific to a conserved region of Trypanosoma cruzi to successfully amplify DNA from triatome bug feces collected from the house wall of an area endemic for Chagas disease. The kinetoplast DNA was considered to be stable because it was detected in feces experimentally exposed to 25°C for 26 weeks, and in feces exposed to 40ºC for four weeks. The use of PCR to screen feces for trypanosome DNA could prove to be a relatively simple means to assess parasite distribution within populated areas. SHK
1471-4922/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved.
TRENDS in Parasitology Vol.17 No.10 October 2001
467
recognized by antiserum of sheep immunized against H. contortus, suggesting that vaccination against H. contortus might induce immunity against T. circumcincta. Although protection against homologous challenge was found, no cross-protection against T. circumcincta, Trichostrongylus axei or Cooperia oncophora was observed [Smith, W.D. et al. (2001) Parasite Immunol. 23, 203–211]. Unexpectedly, vaccination of sheep with equivalent glycoproteins of T. circumcincta significantly reduced worm egg output in sheep that were challenged with H. contortus, whereas no protection against homologous infection was induced. The authors suggest that protection is related to the amount of blood ingested by H. contortus, which is likely to exceed that ingested by T. circumcincta. TS
falciparum infection. Parasight detects the presence of P. falciparum-specific histidinerich protein 2 by using an antigen-capture immunochromatographic strip format. Overall, the sensitivity of Parasight for P. falciparum was 95%, ranging from 83% at low parasite densities (1–500 parasites µl−1) to 98% at high densities (>5000 parasites µl−1). The specificity of the device was 86%. SHK
In Brief
Hubble, bubble, Toll and trouble
A hitherto unrecognized role for Toll-like receptors in initiating immunity against Trypanosoma cruzi was recently identified. M. Campos et al. [(2001) J. Immunol. 167, 416–423] found that highly purified glycosylphosphatidylinositol (GPI) anchors from T. cruzi are potent activators of Toll-like receptor 2 (TLR-2) from both mouse and human origin. These findings were initiated using TLR-2-transfected Chinese hamster ovary-K1 cells, which became activated on exposure to subnanomolar concentrations of trypomastigote-derived GPI anchors. Protozoan-derived GPI anchors were also effective, but only at higher concentrations. Experiments with macrophages from TLR-2 knockout mice showed that TLR-2 expression appears to be essential for GPI anchor-induced upregulation of interleukin 12, tumor necrosis factor α and nitric oxide. The activation of TLR-2 is thought to initiate host innate defense mechanisms and inflammatory responses during protozoan infection and might provide new strategies for immune intervention. SHK
Vampires only For a helminth vaccine to be commercially attractive, it would preferably protect against a range of gastrointestinal helminths. Membrane glycoproteins derived from the gut wall of Haemonchus contortus, most of which have proteolytic activity, successfully protected sheep against haemonchosis. Polypeptides from another gastrointestinal helminth, Teladorsagia circumcincta, were also http://parasites.trends.com
RADical new gene identified in Leishmania The identification of a new gene in Leishmania will open the doors to future research into the contribution of homologous recombination to virulence in this pathogen. The LmRAD51 gene identified by Paul McKean et al. [(2001) Mol. Biochem. Parasitol. 115, 209–216] in Leishmania major encodes a 377-amino-acid polypeptide that is highly homologous to the Rad51 family of proteins. This gene was below the level of detection in exponentially growing cultures of Leishmania, but could be induced at the mRNA and protein level following exposure to the DNA-damaging agent phleomycin. LmRAD51 is one of the first examples of a Leishmania gene that is induced by DNA damage. Based on studies of similar genes in other organisms, LmRAD51 probably plays a central role in homologous recombination and DNA repair. SHK
A new malaria diagnostic device The sensitivity and specificity of a new malaria rapid diagnostic test ‘Parasight’ has been reported. J. Forney et al. [(2001) J. Clin. Microbiol. 39, 2884–2890] performed their study at outpatient malaria clinics in Peru and Thailand, utilizing duplicate, blind samples as the reference standard for microscopic evaluation of the performance of the device in diagnosis of Plasmodium
Why are the French different from the British? Parasites affect the physiological and immunological systems of their host to increase the chance of successful transmission. It has been reported that Toxoplasma gondii, which also infects the brain, can change the behaviour of the host. When rats are infected with T. gondii, the propensity to explore novel stimuli in their environment was increased, whereas there was no effect on social status in the group or mating success. This selective change in behaviour would increase the chance of rats to be captured by cats and consequently increase the transmission of the parasite. Manuel Berdoy from the University of Oxford, UK, states that such effects of T. gondii on the brain could explain the reports of altered personality and IQ levels in some humans following parasite infection. Interestingly, ~22% of the UK population carries the organism, whereas in France the level is 87% (source: www.webmesh.co.uk). TS
Parasites, poo and PCR A surprising report suggests that PCR-based examination of dried feces can be an effective tool for surveillance of trypanosome infection of triatome bugs in residential buildings. S. Hamano et al. [(2001) Parasitol. Int. 50, 135–138] used primers specific to a conserved region of Trypanosoma cruzi to successfully amplify DNA from triatome bug feces collected from the house wall of an area endemic for Chagas disease. The kinetoplast DNA was considered to be stable because it was detected in feces experimentally exposed to 25°C for 26 weeks, and in feces exposed to 40ºC for four weeks. The use of PCR to screen feces for trypanosome DNA could prove to be a relatively simple means to assess parasite distribution within populated areas. SHK
1471-4922/01/$ – see front matter © 2001 Elsevier Science Ltd. All rights reserved.