Plasmodium falciparum-isolates from Cameroonian pregnant
Transcription
Plasmodium falciparum-isolates from Cameroonian pregnant
Article available at http://www.parasite-journal.org or http://dx.doi.org/10.1051/parasite/1998053281 PLASMODIUM FALCIPARUM-ISOLATES FROM CAMEROONIAN PREGNANT WOMEN DO NOT ROSETTE , , , , , MAUBERT B.* ** ***, FIEVET N.* **, TAMI G.*, BOUDIN C.* ** & DELORON P.** **** Summary : The placenta of pregnant women is frequently parasitized by erythrocytes infected by mature stages of Plasmodium falciparum Résumé : PLASMODIUM FALCIPARUM NE FORME PAS DE ROSETTES CHEZ LES FEMMES ENCEINTES CAMEROUNAISES Chez la femme enceinte en zone d'endémie malarique, le (IE), a phenomenon associated with low birth weight of the placenta séquestre les hématies parasitées offspring. The cytoadherence phenotype of the parasites from de Plasmodium falciparum, ce qui entraîne un faible poids de pregnant women suggests that placental sequestration may result naissance. from cytoadherence to the syncytiotrophoblast. However, as syncytiotrophoblaste anatomopathological studies report that cytoadherence in the placentaire, par les stades matures Il a été suggéré que la cytoadhérence au pouvait être impliquée dans la séquestration mais le rôle des autres mécanismes de séquestration placenta is a rare event, we investigated whether placental n'a pas été étudié. Nous parasites may sequester by forming rosettes with uninfected pouvait avons recherché si la séquestration erythrocytes, another possible sequestration mechanism. Parasites avec des hématies non parasitées. résulter de la formation de rosettes des hématies Nous from placental blood as well as parasites from the peripheral capacité à former des rosettes d'isolats blood of pregnant and non pregnant subjects were assessed for du sang placentaire their ability to rosette. In non pregnant subjects, the rosetting ainsi capacity of parasites was as reported in litterature while, except sujets non enceintes, de P. falciparum et du sang périphérique que du sang périphérique parasitées avons mesuré la de femmes de sujets non enceintes. la fréquence provenant enceintes, Chez les et l'intensité de la formation de in one case, parasites from pregnant women did not rosette. W e rosettes étaient conformes aux valeurs rapportées conclude that the lack of rosetting is a new feature of lEs from études, alors que, hormis un cas, les parasites des femmes pregnant women and that rosetting cannot be involved in the enceintes ne formaient pas de rosettes. En conclusion, la placental sequestration of lEs. séquestration placentaire dans d'autres des hématies parasitées par P. falciparum ne peut pas résulter de la formation de rosettes et le K E Y W O R D S : malaria, Plasmodium falciparum, human, placenta, pregnancy, rosette. ABBREVIATION : IE, Plasmodium falciparum-infected erythrocyte. I manque de capacité à former des rosettes est une nouvelle caractéristique des isolats des femmes enceintes. MOTS CLÉS : paludisme, Plasmodium falciparum, humain, placenta, grossesse, rosette. t h e peripheral b l o o d o f t h e s a m e w o m a n c o n t a i n s o n l y n areas in w h i c h Plasmodium falciparum malaria young stages (Garnham, 1938). The involvement o f is e n d e m i c , p l a c e n t a l malaria is frequent a n d a s s o c y t o a d h e r e n c e as a m e c h a n i s m for the sequestration o f ciated with l o w birth weight o f t h e b a b y , a major IEs in the p l a c e n t a has b e e n r e p o r t e d (Fried & Duffy, c a u s e o f neonatal morbidity, thus posing a public health 1996; Maubert et a l , 1 9 9 7 ) , but o t h e r potential m e c h a - p r o b l e m (for review, s e e B r a b i n , 1 9 9 1 a n d M e n e n d e z , nisms h a v e not b e e n a s s e s s e d . Rosettes ( b i n d i n g o f at 1 9 9 5 ) . In the placenta, most o f infected erythrocytes ( I E ) c o n t a i n mature stages o f t h e parasite, w h i l e IEs from least t w o uninfected erythrocytes to an infected ery- t h r o c y t e ) are large cellular structures that facilitate the s e q u e s t r a t i o n o f IEs in microvasculature ex vivo (Kaul et a l , 1 9 9 1 ) . W e investigated w h e t h e r malaria parasites from pregnant w o m e n c o u l d form rosettes, that c o u l d * Organisation d e Coordination p o u r la Lutte c o n t r e l e s E n d é m i e s e n Afrique C e n t r a l e ( O C E A C ) , P B 2 8 8 , Y a o u n d e , ** Institut F r a n ç a i s d e R e c h e r c h e Scientifique p o u r l e D é v e l o p p e m e n t en Coopération b e t r a p p e d in t h e placental intervillous s p a c e s . F o r this Cameroon. p u r p o s e , w e c o m p a r e d the rosetting ability o f parasites from pregnant a n d n o n pregnant (ORSTOM). subjects. *** Institut National d e la S a n t é e t de la R e c h e r c h e M é d i c a l e U 1 3 / I n s titut d e M é d e c i n e et d'Épidémiologie Claude-Bernard, 4 6 , rue Henri-Huchard, Africaine, Hôpital Bichat- 7 5 0 1 8 Paris, F r a n c e . **** P r é s e n t a d d r e s s : P h i l i p p e D e l o r o n , U n i t é d e P a r a s i t o l o g i e M é d i cale, Centre International BP 7 6 9 , Franceville, G a b o n . Correspondence: METHODS AND RESULTS d e R e c h e r c h e Médicale d e Franceville, B . Maubert I M E A / I N S E R M U 1 3 , Hôpital Bichat, 46, r u e Henri-Huchard, 7 5 0 1 8 Paris, F r a n c e . Tel.: ( 3 3 ) 01 4 0 2 5 63 65 Fax: (33) 0 1 4 0 2 5 63 5 1 . e-mail: m a u b e r t @ b i c h a t . i n s e r m . f r . P Parasite, 1 9 9 8 , 5, 2 8 1 - 2 8 3 Note de recherche arasites from collected from attending at non the pregnant nine women subjects and M e s s a dispensary, five were men Yaounde, 281 M A U B E R T B . , F I E V E T N., T A M I G . , B O U D I N C. & D E L O R O N P. Cameroon. T h e y presented with acute but uncomplicated P. falciparum malaria, a peripheral parasitaemia higher than 0.2 %, and were 22.2 ± 6.6 years old ( m ± S D ) . B l o o d samples were drawn and parasites w e r e c r y o c o n s e r v e d in liquid nitrogen. Before the assay, samples w e r e thawed and cultured for less than o n e cycle to pigmented stages (late trophozoites to young schizonts) according to the standard method (Trager & J e n s e n , 1976). Among those 14 isolates, parasites from 12 showed mature stages within the first life cycle, and rosetting assay was performed using the standard p r o c e d u r e ( C a r l s o n & W a h l g r e n , 1 9 9 2 ) . Briefly, 5 0 µl o f the parasite culture was mixed with 50 µl o f a 0.01 % acridine orange solution. 10 µl o f the suspension were distributed under a 22 x 22 m m coverslip and at least 2 0 0 IEs were e x a m i n e d under fluorescence microscopy using x 5 0 0 magnification. T h e n u m b e r o f rosettes (i. e. IEs that b o u n d at least two uninfected erythrocytes) was determined. Eight out o f the 12 samples studied formed rosettes, the percent o f IEs forming rosettes being: 1, 1, 1, 5.5, 6.5, 7.5, 14.5, and 17.5. T h e s e figures are in line with other reports (Hasler et al, 1 9 9 0 ; Wahlgren et al, 1990), and the rosetting ability was not related to s e x . W e assessed rosette formation in placental b l o o d from parasitized placentas collected after delivery in two maternity hospitals ( N k o l n d o n g o and Etoudi) o f Y a o u n d e . Their age was similar to the o n e o f non pregnant subjects ( 2 1 . 5 ± 5.6 years). An incision was m a d e on the maternal face o f the placenta and a drop o f placental b l o o d was diluted to a 5 % hematocrit in P. falciparum culture medium containing acridine orange. Rosetting rate was assessed as above. None o f the 23 infected placental b l o o d studied presented with rosettes. As the a b s e n c e o f rosettes in placental b l o o d may b e related to alteration o f the IEs during labor, w e studied parasites from the peripheral b l o o d o f pregnant w o m e n . Twenty five w o m e n (age: 2 2 . 8 ± 4 . 6 ) presenting with a b l o o d parasites were bled within o n e hour after delivery and parasites w e r e cryoconserved. Rosetting assay was performed as mentioned for n o n pregnant subjects. After in vitro culture, 16 samples s h o w e d mature parasites and at least 0.2 % parasite density. Seven w e r e the peripheral counterpart o f studied placental parasites and nine w e r e from other w o m e n . Only o n e formed rosettes and the percentage o f rosette-forming IEs was low (2 % ) . (Fisher's exact test p = 0 . 0 0 1 ) , and than in placental b l o o d ( 0 / 2 3 ) ( F i s h e r ' s e x a c t test p < 0 . 0 0 0 1 ) . As rosetting assay with parasites from peripheral b l o o d was performed in a medium free o f immune serum, the difference in rosetting ability cannot result from a difference in antibodies against rosettes. In non-pregnant host, rosetting facilitates the s e q u e s tration o f parasites ex vivo (Kaul et al., 1991). H o w e v e r the i m p l i c a t i o n o f rosetting in h u m a n p a t h o l o g y remains uncertain as studies c o n d u c t e d in G a m b i a (Carlson, 1 9 9 3 ) and in Kenia ( R o w e et al., 1 9 9 5 ) found an association b e t w e e n rosetting and the development o f severe or cerebral malaria, while n o such relationship was found in a larger study carried out in Papua New Guinea (Al-Yaman et al., 1 9 9 5 ) . Although pregnant w o m e n are at increased risk for malaria (Diagne et al., 1 9 9 7 ) , our data demonstrate that rosetting is not involved in pregnancy-related malaria morbidity which has to b e explained by other mechanisms. Parasites from pregnant and non pregnant w o m e n were recently b e e n s h o w n to differ in their c y t o a d h e r e n c e p h e n o type (Fried & Duffy, 1996). Our data s h o w that the lack o f rosetting ability is another feature o f parasites from pregnant w o m e n and that rosetting cannot contribute to parasite concentration in the placenta. ACKNOWLEDGEMENTS W e are indebted to Anne Daban and the staff o f the maternity clinics o f N k o l n d o n g o and Etoudi, and especially to Odette N k o u o and Sister Anne-Philippe. 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HELMBY Reçu le 17 février 1998 Accepté le 25 avril 1998 Parasite, 1 9 9 8 , 5, 2 8 1 - 2 8 3 Note de recherche 283