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PLASMODIUM FALCIPARUM-ISOLATES

FRO

M CAMEROONIAN PREGNANT WOMEN DO NOT ROSETTE

MAUBER

T B.*, **, ***, FIEVET N.*, **, TAMI G.*, BOUDIN C.*, ** & DELORON P.**, ****

Summar

y : Th e placenta of pregnant women is frequently parasitized by erythrocyte s infected by mature stages of Plasmodium falciparum (IE) , a phenomenon associated with low birth weight of the offspring . The cytoadherence phenotype of the parasites from pregnan t wome n suggests that placental sequestration may result fro m cytoadherence to the syncytiotrophoblast. However, as anatomopathologica l studies report that cytoadherence in the placent a i s a rare event, we investigated whether placental parasite s may sequester by forming rosettes with uninfected erythrocytes , another possible sequestration mechanism. Parasites fro m placental blood as well as parasites from the peripheral bloo d of pregnant and non pregnant subjects were assessed for thei r ability to rosette. In non pregnant subjects, the rosetting capacit y of parasites was as reported in litterature while, except i n one case, parasites from pregnant women did not rosette. We conclud e tha t the lack of rosetting is a new feature of lEs from pregnan t wome n and that rosetting cannot be involved in the placenta l sequestration of lEs.

KEYWORD

S : malaria, Plasmodium falciparum, human, placenta, pregnancy, rosette

ABBREVIATIO

N : IE, Plasmodium falciparum-infected erythrocyte. Résumé : PLASMODIUM FALCIPARUM NE FORME PAS DE ROSETTES CHEZ LE

S FEMMES ENCEINTES CAMEROUNAISES

Che z la femme enceinte en zone d'endémie malarique, le placenta séquestre les hématies parasitées par les stades matures de Plasmodium falciparum, ce qui entraîne un faible poids de naissance. Il a été suggéré que la cytoadhérence au syncytiotrophoblaste pouvait

être

impliquée dans la séquestration placentaire, mais le rôle des autres mécanismes de séquestration n'a pas été étudié. Nous avons recherché si la séquestration pouvait résulter de la formation de rosettes des hématies parasitées avec des hématies non parasitées. Nous avons mesuré la capacité à former des rosettes d'isolats de P. falciparum provenant du sang placentaire et du sang périphérique de femmes enceintes, ainsi que du sang périphérique de sujets non enceintes. Chez les sujets non enceintes, la fréquence et l'intensité de la formation de rosettes étaient conformes aux valeurs rapportées dans d'autres études, alors que, hormis un cas, les parasites des femmes enceintes ne formaient pas de rosettes. En conclusion, la séquestration placentaire des hématies parasitées par P . falciparum ne peut pas résulter de la formation de rosettes et le 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. I n area s i n whic h Plasmodium falciparum malaria i s endemic, placental malaria is frequent and asso ciate d with low birth weight of the baby, a major caus e of neonatal morbidity, thus posing a public health proble m (fo r review se e

Brabin

199
1 an d

Menendez

1995)
. In the placenta, most of infected erythrocytes (IE) contai n mature stages of the parasite, while IEs from th e periphera l bloo d o f th e sam e woma n contain s onl y youn g stage s (Garnham , 1938). The involvement of cytoadherenc e as a mechanism for the sequestration of IE s in the placenta has been reported (Fried & Duffy, 1996
; Maubert et al, 1997), but other potential mecha nism s hav e no t bee n assessed

Rosette

s (bindin g o f a t leas t two uninfected erythrocytes to an infected ery throcyte ) are large cellular structures that facilitate the sequestratio n o f IE s i n microvasculatur e ex vivo (Kaul et al, 1991). We investigated whether malaria parasites fro m pregnant women could form rosettes, that could b e trapped in the placental intervillous spaces. For this purpose w e compare d th e rosettin g abilit y o f parasite s fro m pregnant and non pregnant subjects.

METHOD

S AND RESULTS

P arasite s fro m no n pregnan t subject s wer e collecte d from nine women and five men attendin g a t th e Mess a dispensary

Yaounde

* Organisation de Coordination pour la Lutte contre les Endιmies e n

Afriqu

e

Central

e (OCEAC), PB288, Yaounde, Cameroon. ** Institut Franηais de Recherche Scientifique pour le Dιveloppement e n

Coopιratio

n (ORSTOM). * Institut National de la Santι et de la Recherche Mιdicale U13/Ins- titu t de Mιdecine et d'Ιpidιmiologie Africaine, Hτpital Bichat-

Claude-Bernard

, 46, rue Henri-Huchard, 75018 Paris, France. * Prιsent address: Philippe Deloron, Unitι de Parasitologie Mιdi cale , Centre International de Recherche Mιdicale de Franceville, B

P 769, Franceville, Gabon.

Correspondence

: B. Maubert IMEA/INSERM U13, Hτpital Bichat, 46
, rue Henri-Huchard, 75018 Paris, France. Tel.: (33) 01 40 25 63 65 - Fax : (33) 01 40 25 63 51. e-mail: maubert@bichat.inserm.fr.

Parasite

1998, 5, 281-283

Not e de recherche 281 Article available athttp://www.parasite-journal.orgorhttp://dx.doi.org/10.1051/parasite/1998053281 MAUBERT B., FIEVET N., TAMI G., BOUDIN C. & DELORON P.

Cameroon

The y presente d wit h acut e bu t uncompli cate d P. falciparum malaria, a peripheral parasitaemia highe r tha n

0.2 %, and were 22.2 ± 6.6 years old

m ± SD). Blood samples were drawn and parasites wer e cryoconserve d i n liqui d nitrogen . Before the assay , samples were thawed and cultured for less than on e cycle to pigmented stages (late trophozoites to youn g schizonts accordin g t o th e standar d metho d (Trage r & Jensen, 1976). Among those 14 isolates, parasite s fro m

12 showed mature stages within the first

lif e cycle, and rosetting assay was performed using the standar d procedur e (Carlso n & Wahlgren, 1992).

Briefly

, 50 µl of the parasite culture was mixed with 5

0 µl of a 0.01 % acridine orange solution. 10 µl of

th e suspensio n wer e distribute d under a 22 x 22 mm coversli p and at least 200 IEs were examined under fluorescenc e microscopy using x 500 magnification. Th e number of rosettes (i. e. IEs that bound at least tw o uninfecte d erythrocytes wa s determined Eigh t ou t 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, an d

17.5. These figures are in line with other reports

(Hasle r et al, 1990; Wahlgren et al, 1990), and the rosettin g abilit y wa s no t relate d t o sex W e assessed rosette formation in placental blood from parasitize d placenta s collecte d afte r deliver y i n tw o maternit y hospital s (Nkolndong o an d

Etoudi

o f

Yaounde

. Their age was similar to the one of non pre gnan t subject s (21.5 ± 5.6 years). An incision was mad e o n th e materna l face of the placenta and a drop o f placental blood was diluted to a 5 % hematocrit in

P. falciparum culture medium containing acridine

orange

Rosettin

g rat e wa s assesse d a s above Non e o f th e

23 infected placental blood studied presented with

rosettes A s the absence of rosettes in placental blood may be relate d t o alteratio n o f th e IE s during labor, we stu die d parasite s fro m th e periphera l bloo d o f pregnan t women Twent y fiv e wome n (age

22.8 ± 4.6) pre

sentin g wit hquotesdbs_dbs22.pdfusesText_28

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