Subject(s)
Membrane Proteins/physiology , Amino Acid Motifs , Animals , Antigens, CD/genetics , Antigens, CD/physiology , Hepatocytes/chemistry , Hepatocytes/parasitology , Humans , Immunity, Innate , Membrane Glycoproteins/genetics , Membrane Glycoproteins/physiology , Membrane Proteins/chemistry , Membrane Proteins/classification , Membrane Proteins/genetics , Mice , Mice, Knockout , Multigene Family , Plasmodium falciparum/physiology , Sequence Homology, Amino Acid , Tetraspanin 28 , Tetraspanin 29ABSTRACT
The value of some inexpensive modifications to the standard method of preparing thick bloodsmears, involving rapid drying, an isotonic fixative and a haemolysing solution containing saponin, was evaluated. The drying, haemolysing, fixing and staining steps, together called the fast-thick-smear method (FTS), can be completed in < 10 min. The FTS and a more classical thick-smear method (CTS) were both used on each of 1185 samples of venous blood samples from 1034 cases of suspected malaria (all international travellers returning to France). The results indicated that there was no statistically significant differences between the two methods in terms of their sensitivity, specificity or predictive values for parasite detection. However, estimates of the intensities of the Plasmodium falciparum infections observed, based on counts of trophozoites against 200 leucocytes, were markedly higher (37.8% higher overall) with the FTS than with the CTS (P < 0.0001). Moreover, the concordance between results obtained by inexperienced and experienced microscopists was excellent when the FTS was used, with a kappa value of 0.96 (95% confidence interval = 0.93-0.98).
Subject(s)
Blood Specimen Collection/methods , Malaria/diagnosis , Parasitemia/diagnosis , Clinical Competence , Humans , Malaria, Falciparum/diagnosis , Observer Variation , Parasitology/methods , Predictive Value of Tests , Prospective Studies , Sensitivity and Specificity , TravelABSTRACT
Immunization with irradiation-attenuated Plasmodium sporozoites confer protection against live sporozoite challenge. Protection relies primarily on cytotoxic lymphocyte activity against infected hepatocytes, and is suppressed when sporozoites are over-irradiated. Here, we demonstrate that over-irradiated (25-30 krad) Plasmodium falciparum sporozoites invade human hepatocytes and transform into uninucleate liver-trophozoites with the same efficiency as non-irradiated and irradiation-attenuated (12-15 krad) sporozoites. Since hepatocytes infected with over-irradiated non-protective sporozoites are likely to express sporozoite-derived peptide/major histocompatibility complex class I molecules on their surface, our results strongly suggest that sporozoite proteins are not the main immunogens involved in protection, and thus may not per se constitute proper malaria vaccine candidates.
