Limits...
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.

Show MeSH

Related in: MedlinePlus

Mosquito injection of Plasmodium berghei sporozoites into mouse ear pinna or ventral abdomen (controls vs. mice passively immunized with anti-sporozoite antibodies).Scatter plot shows numbers of sporozoites deposited at bite site from biopsy specimens taken immediately after mosquito feeding. Each point shows number of sporozoites left by a single mosquito. (N = total number of mosquito feedings for each time point.) After mosquitoes fed on the ear pinnae of control mice, we found a median of 51 sporozoites deposited in the tissue; there was a 54% reduction in numbers of sporozoites injected into passively immunized mice (**P = 0.005). (IV-injected monoclonal antibodies were directed against repeat region of CSP of P. berghei sporozoites.) After mosquitoes fed on the ventral abdomen of control mice, we found a median of 33 sporozoites deposited in abdominal tissues; there was a 54.5% reduction in numbers of sporozoites injected into passively immunized mice (**P = 0.005).
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2667259&req=5

ppat-1000399-g004: Mosquito injection of Plasmodium berghei sporozoites into mouse ear pinna or ventral abdomen (controls vs. mice passively immunized with anti-sporozoite antibodies).Scatter plot shows numbers of sporozoites deposited at bite site from biopsy specimens taken immediately after mosquito feeding. Each point shows number of sporozoites left by a single mosquito. (N = total number of mosquito feedings for each time point.) After mosquitoes fed on the ear pinnae of control mice, we found a median of 51 sporozoites deposited in the tissue; there was a 54% reduction in numbers of sporozoites injected into passively immunized mice (**P = 0.005). (IV-injected monoclonal antibodies were directed against repeat region of CSP of P. berghei sporozoites.) After mosquitoes fed on the ventral abdomen of control mice, we found a median of 33 sporozoites deposited in abdominal tissues; there was a 54.5% reduction in numbers of sporozoites injected into passively immunized mice (**P = 0.005).

Mentions: To assess whether the reduced number of sporozoites deposited in actively immunized mice could be attributed to antibodies alone, we repeated the above studies with mice that had received passive IV transfer of a monoclonal antibody (MoAb 3D11), which is directed against the repeat region of the CS protein of P. berghei sporozoites. Control mice received either PBS or no injection. Challenge by bite of infected mosquitoes was delayed for 24 h to allow the MoAb to permeate avascular skin tissue. A summary of numbers of sporozoites visualized at the bite sites after feedings by individual mosquitoes is presented as a scatter plot in Fig. 4. After mosquitoes fed on the ear pinnae of control mice, we found a median of 51 sporozoites in biopsy specimens taken immediately after feeding; there was a 54% reduction in numbers of sporozoites injected into passively immunized mice; P = 0.005. After mosquitoes fed on the ventral abdomen of control mice, we found a median of 33 sporozoites in biopsy specimens taken immediately after feeding; there was a 54.5% reduction in numbers of sporozoites injected into passively immunized mice; P = 0.005. No immunized mice developed parasitemia after challenge by bite of individual mosquitoes, whereas 39% of the paired, non-immunized control mice developed parasitemia under the same conditions. As an additional negative control we passively immunized some mice in the same manner with MoAb NYS1, which is directed against the repeat region of the CS protein of P. yoelii sporozoites [9] and challenged these mice by bite of mosquitoes infected with P. berghei sporozoites (N = 8, with 2 ear bite sites and 2 abdominal bite sites for each mouse). There was no significant difference in numbers of sporozoites deposited in the ear pinnae or abdominal tissues of mice passively immunized with this heterologous antibody vs. non-immunized control mice, as determined by ANOVA (P>0.2).


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)

Mosquito injection of Plasmodium berghei sporozoites into mouse ear pinna or ventral abdomen (controls vs. mice passively immunized with anti-sporozoite antibodies).Scatter plot shows numbers of sporozoites deposited at bite site from biopsy specimens taken immediately after mosquito feeding. Each point shows number of sporozoites left by a single mosquito. (N = total number of mosquito feedings for each time point.) After mosquitoes fed on the ear pinnae of control mice, we found a median of 51 sporozoites deposited in the tissue; there was a 54% reduction in numbers of sporozoites injected into passively immunized mice (**P = 0.005). (IV-injected monoclonal antibodies were directed against repeat region of CSP of P. berghei sporozoites.) After mosquitoes fed on the ventral abdomen of control mice, we found a median of 33 sporozoites deposited in abdominal tissues; there was a 54.5% reduction in numbers of sporozoites injected into passively immunized mice (**P = 0.005).
© Copyright Policy
Related In: Results  -  Collection

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

ppat-1000399-g004: Mosquito injection of Plasmodium berghei sporozoites into mouse ear pinna or ventral abdomen (controls vs. mice passively immunized with anti-sporozoite antibodies).Scatter plot shows numbers of sporozoites deposited at bite site from biopsy specimens taken immediately after mosquito feeding. Each point shows number of sporozoites left by a single mosquito. (N = total number of mosquito feedings for each time point.) After mosquitoes fed on the ear pinnae of control mice, we found a median of 51 sporozoites deposited in the tissue; there was a 54% reduction in numbers of sporozoites injected into passively immunized mice (**P = 0.005). (IV-injected monoclonal antibodies were directed against repeat region of CSP of P. berghei sporozoites.) After mosquitoes fed on the ventral abdomen of control mice, we found a median of 33 sporozoites deposited in abdominal tissues; there was a 54.5% reduction in numbers of sporozoites injected into passively immunized mice (**P = 0.005).
Mentions: To assess whether the reduced number of sporozoites deposited in actively immunized mice could be attributed to antibodies alone, we repeated the above studies with mice that had received passive IV transfer of a monoclonal antibody (MoAb 3D11), which is directed against the repeat region of the CS protein of P. berghei sporozoites. Control mice received either PBS or no injection. Challenge by bite of infected mosquitoes was delayed for 24 h to allow the MoAb to permeate avascular skin tissue. A summary of numbers of sporozoites visualized at the bite sites after feedings by individual mosquitoes is presented as a scatter plot in Fig. 4. After mosquitoes fed on the ear pinnae of control mice, we found a median of 51 sporozoites in biopsy specimens taken immediately after feeding; there was a 54% reduction in numbers of sporozoites injected into passively immunized mice; P = 0.005. After mosquitoes fed on the ventral abdomen of control mice, we found a median of 33 sporozoites in biopsy specimens taken immediately after feeding; there was a 54.5% reduction in numbers of sporozoites injected into passively immunized mice; P = 0.005. No immunized mice developed parasitemia after challenge by bite of individual mosquitoes, whereas 39% of the paired, non-immunized control mice developed parasitemia under the same conditions. As an additional negative control we passively immunized some mice in the same manner with MoAb NYS1, which is directed against the repeat region of the CS protein of P. yoelii sporozoites [9] and challenged these mice by bite of mosquitoes infected with P. berghei sporozoites (N = 8, with 2 ear bite sites and 2 abdominal bite sites for each mouse). There was no significant difference in numbers of sporozoites deposited in the ear pinnae or abdominal tissues of mice passively immunized with this heterologous antibody vs. non-immunized control mice, as determined by ANOVA (P>0.2).

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