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Kinetics of mosquito-injected Plasmodium sporozoites in mice: fewer sporozoites are injected into sporozoite-immunized mice.

Kebaier C, Voza T, Vanderberg J - PLoS Pathog. (2009)

Bottom Line: Sporozoites injected into immunized mice were rapidly immobilized, did not appear to invade dermal blood vessels and became morphologically degraded within several hours.Strikingly, mosquitoes introduced significantly fewer sporozoites into immunized than into non-immunized mice, presumably by formation of an immune complex between soluble sporozoite antigens in the mosquito saliva and homologous host antibodies at the proboscis tip.These results indicate that protective antibodies directed against sporozoites may function both by reducing the numbers of sporozoites injected into immunized hosts and by inhibiting the movement of injected sporozoites into dermal blood vessels.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Parasitology, New York University School of Medicine, New York, New York, United States of America.

ABSTRACT
Malaria is initiated when the mosquito introduces sporozoites into the skin of a mammalian host. To successfully continue the infection, sporozoites must invade blood vessels in the dermis and be transported to the liver. A significant number of sporozoites, however, may enter lymphatic vessels in the skin or remain in the skin long after the mosquito bite. We have used fluorescence microscopy of Plasmodium berghei sporozoites expressing a fluorescent protein to evaluate the kinetics of sporozoite disappearance from the skin. Sporozoites injected into immunized mice were rapidly immobilized, did not appear to invade dermal blood vessels and became morphologically degraded within several hours. Strikingly, mosquitoes introduced significantly fewer sporozoites into immunized than into non-immunized mice, presumably by formation of an immune complex between soluble sporozoite antigens in the mosquito saliva and homologous host antibodies at the proboscis tip. These results indicate that protective antibodies directed against sporozoites may function both by reducing the numbers of sporozoites injected into immunized hosts and by inhibiting the movement of injected sporozoites into dermal blood vessels.

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Confocal micrographs of remnant Plasmodium berghei sporozoites in the skin of control vs. immunized mice.A & B show typical presentation of sporozoites 2 and 4 h, respectively after mosquito inoculation into ear pinnae. C & D show typical presentation of sporozoites 2 and 4 h, respectively, after mosquito inoculation into ear pinna of actively immunized mice. Bar = 5 µm.
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ppat-1000399-g002: Confocal micrographs of remnant Plasmodium berghei sporozoites in the skin of control vs. immunized mice.A & B show typical presentation of sporozoites 2 and 4 h, respectively after mosquito inoculation into ear pinnae. C & D show typical presentation of sporozoites 2 and 4 h, respectively, after mosquito inoculation into ear pinna of actively immunized mice. Bar = 5 µm.

Mentions: Immunized mice at 0 h had a median number of sporozoites that was less than 45% of the median number deposited in non-immunized 0 h controls; this reduction was highly significant; P<0.001. Motility of sporozoites in immunized mice ceased within min after deposition by mosquitoes. Counts of sporozoites injected into immunized mice were unreliable beyond 2 h due to deterioration and fragmentation of sporozoites (Fig. 2). Immunization status of mice was verified by ELISA, with use of a multiple antigen peptide specific for the P. berghei CSP for capture of anti-CSP antibodies in mouse sera. The geometric mean ELISA titer of sera taken from immunized mice on the day prior to challenge was 17,065 compared with <80 for sera from non-immunized controls. No immunized mice developed parasitemia after challenge by bite of individual mosquitoes, whereas 60% of the paired, non-immunized control mice developed parasitemia under the same conditions.


Kinetics of mosquito-injected Plasmodium sporozoites in mice: fewer sporozoites are injected into sporozoite-immunized mice.

Kebaier C, Voza T, Vanderberg J - PLoS Pathog. (2009)

Confocal micrographs of remnant Plasmodium berghei sporozoites in the skin of control vs. immunized mice.A & B show typical presentation of sporozoites 2 and 4 h, respectively after mosquito inoculation into ear pinnae. C & D show typical presentation of sporozoites 2 and 4 h, respectively, after mosquito inoculation into ear pinna of actively immunized mice. Bar = 5 µm.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2667259&req=5

ppat-1000399-g002: Confocal micrographs of remnant Plasmodium berghei sporozoites in the skin of control vs. immunized mice.A & B show typical presentation of sporozoites 2 and 4 h, respectively after mosquito inoculation into ear pinnae. C & D show typical presentation of sporozoites 2 and 4 h, respectively, after mosquito inoculation into ear pinna of actively immunized mice. Bar = 5 µm.
Mentions: Immunized mice at 0 h had a median number of sporozoites that was less than 45% of the median number deposited in non-immunized 0 h controls; this reduction was highly significant; P<0.001. Motility of sporozoites in immunized mice ceased within min after deposition by mosquitoes. Counts of sporozoites injected into immunized mice were unreliable beyond 2 h due to deterioration and fragmentation of sporozoites (Fig. 2). Immunization status of mice was verified by ELISA, with use of a multiple antigen peptide specific for the P. berghei CSP for capture of anti-CSP antibodies in mouse sera. The geometric mean ELISA titer of sera taken from immunized mice on the day prior to challenge was 17,065 compared with <80 for sera from non-immunized controls. No immunized mice developed parasitemia after challenge by bite of individual mosquitoes, whereas 60% of the paired, non-immunized control mice developed parasitemia under the same conditions.

Bottom Line: Sporozoites injected into immunized mice were rapidly immobilized, did not appear to invade dermal blood vessels and became morphologically degraded within several hours.Strikingly, mosquitoes introduced significantly fewer sporozoites into immunized than into non-immunized mice, presumably by formation of an immune complex between soluble sporozoite antigens in the mosquito saliva and homologous host antibodies at the proboscis tip.These results indicate that protective antibodies directed against sporozoites may function both by reducing the numbers of sporozoites injected into immunized hosts and by inhibiting the movement of injected sporozoites into dermal blood vessels.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Parasitology, New York University School of Medicine, New York, New York, United States of America.

ABSTRACT
Malaria is initiated when the mosquito introduces sporozoites into the skin of a mammalian host. To successfully continue the infection, sporozoites must invade blood vessels in the dermis and be transported to the liver. A significant number of sporozoites, however, may enter lymphatic vessels in the skin or remain in the skin long after the mosquito bite. We have used fluorescence microscopy of Plasmodium berghei sporozoites expressing a fluorescent protein to evaluate the kinetics of sporozoite disappearance from the skin. Sporozoites injected into immunized mice were rapidly immobilized, did not appear to invade dermal blood vessels and became morphologically degraded within several hours. Strikingly, mosquitoes introduced significantly fewer sporozoites into immunized than into non-immunized mice, presumably by formation of an immune complex between soluble sporozoite antigens in the mosquito saliva and homologous host antibodies at the proboscis tip. These results indicate that protective antibodies directed against sporozoites may function both by reducing the numbers of sporozoites injected into immunized hosts and by inhibiting the movement of injected sporozoites into dermal blood vessels.

Show MeSH
Related in: MedlinePlus