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The transmembrane isoform of Plasmodium falciparum MAEBL is essential for the invasion of Anopheles salivary glands.

Saenz FE, Balu B, Smith J, Mendonca SR, Adams JH - PLoS ONE (2008)

Bottom Line: MAEBL is the first P. falciparum ligand experimentally determined to be essential for this important step in the life cycle where the vector becomes infectious for transmitting sporozoites to people.With an increasing emphasis on advancing vector-based transgenic methods for suppression of malaria, it is important that this type of study, using modern molecular genetic tools, is done with the agent of the human disease.Understanding what P. falciparum sporozoite ligands are critical for mosquito transmission will help validate targets for vector-based transmission-blocking strategies.

View Article: PubMed Central - PubMed

Affiliation: Global Health and Infectious Diseases Research, Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida, United States of America.

ABSTRACT
Malaria transmission depends on infective stages in the mosquito salivary glands. Plasmodium sporozoites that mature in midgut oocysts must traverse the hemocoel and invade the mosquito salivary glands in a process thought to be mediated by parasite ligands. MAEBL, a homologue of the transmembrane EBP ligands essential in merozoite invasion, is expressed abundantly in midgut sporozoites. Alternative splicing generates different MAEBL isoforms and so it is unclear what form is functionally essential. To identify the MAEBL isoform required for P. falciparum (NF54) sporozoite invasion of salivary glands, we created knockout and allelic replacements each carrying CDS of a single MAEBL isoform. Only the transmembrane form of MAEBL is essential and is the first P. falciparum ligand validated as essential for invasion of Anopheles salivary glands. MAEBL is the first P. falciparum ligand experimentally determined to be essential for this important step in the life cycle where the vector becomes infectious for transmitting sporozoites to people. With an increasing emphasis on advancing vector-based transgenic methods for suppression of malaria, it is important that this type of study, using modern molecular genetic tools, is done with the agent of the human disease. Understanding what P. falciparum sporozoite ligands are critical for mosquito transmission will help validate targets for vector-based transmission-blocking strategies.

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Related in: MedlinePlus

Sections of salivary glands of Anopheles mosquitoes infected with NF54, ORF1, ORF2 and MAEBL KO on day 19 post feeding are shown in Nomarski bright field images (top lane) and by nuclear fluorescence using dihydroethidium (bottom lane).The sporozoites can be seen as small nuclei inside the salivary cells. NF54 and ORF1 sporozoites are visible inside salivary glands cells whereas no sporozoites of ORF2 or MAEBL KO clones were found in salivary glands. These results were confirmed by RT-PCR using primers for csp.
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pone-0002287-g003: Sections of salivary glands of Anopheles mosquitoes infected with NF54, ORF1, ORF2 and MAEBL KO on day 19 post feeding are shown in Nomarski bright field images (top lane) and by nuclear fluorescence using dihydroethidium (bottom lane).The sporozoites can be seen as small nuclei inside the salivary cells. NF54 and ORF1 sporozoites are visible inside salivary glands cells whereas no sporozoites of ORF2 or MAEBL KO clones were found in salivary glands. These results were confirmed by RT-PCR using primers for csp.

Mentions: P. falciparum sporozoites usually begin to infect the salivary glands of Anopheles mosquitoes beginning day 14 post blood meal. This was confirmed in NF54 parasites, where hundreds or thousands of sporozoites were observed inside the salivary glands (Figure 3). Similar to the wild type NF54, ORF1 mutant parasites had abundant sporozoites in the salivary glands (Figure 3, Figure S1, Table 1). In contrast, no sporozoites were observed or detected in the salivary glands of mosquitoes fed the MAEBL KO parasites or ORF2 mutant parasites (Figure 3), even though midgut sporozoites were readily observed beginning day 10 in the hemolymph of these mosquitoes infected with the MAEBL KO or ORF2 mutant. The absence of sporozoites in the salivary glands determined by microscopic analysis was confirmed with RT-PCR using primers for csp, the most highly expressed gene in sporozoites (Figure 4).


The transmembrane isoform of Plasmodium falciparum MAEBL is essential for the invasion of Anopheles salivary glands.

Saenz FE, Balu B, Smith J, Mendonca SR, Adams JH - PLoS ONE (2008)

Sections of salivary glands of Anopheles mosquitoes infected with NF54, ORF1, ORF2 and MAEBL KO on day 19 post feeding are shown in Nomarski bright field images (top lane) and by nuclear fluorescence using dihydroethidium (bottom lane).The sporozoites can be seen as small nuclei inside the salivary cells. NF54 and ORF1 sporozoites are visible inside salivary glands cells whereas no sporozoites of ORF2 or MAEBL KO clones were found in salivary glands. These results were confirmed by RT-PCR using primers for csp.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2386256&req=5

pone-0002287-g003: Sections of salivary glands of Anopheles mosquitoes infected with NF54, ORF1, ORF2 and MAEBL KO on day 19 post feeding are shown in Nomarski bright field images (top lane) and by nuclear fluorescence using dihydroethidium (bottom lane).The sporozoites can be seen as small nuclei inside the salivary cells. NF54 and ORF1 sporozoites are visible inside salivary glands cells whereas no sporozoites of ORF2 or MAEBL KO clones were found in salivary glands. These results were confirmed by RT-PCR using primers for csp.
Mentions: P. falciparum sporozoites usually begin to infect the salivary glands of Anopheles mosquitoes beginning day 14 post blood meal. This was confirmed in NF54 parasites, where hundreds or thousands of sporozoites were observed inside the salivary glands (Figure 3). Similar to the wild type NF54, ORF1 mutant parasites had abundant sporozoites in the salivary glands (Figure 3, Figure S1, Table 1). In contrast, no sporozoites were observed or detected in the salivary glands of mosquitoes fed the MAEBL KO parasites or ORF2 mutant parasites (Figure 3), even though midgut sporozoites were readily observed beginning day 10 in the hemolymph of these mosquitoes infected with the MAEBL KO or ORF2 mutant. The absence of sporozoites in the salivary glands determined by microscopic analysis was confirmed with RT-PCR using primers for csp, the most highly expressed gene in sporozoites (Figure 4).

Bottom Line: MAEBL is the first P. falciparum ligand experimentally determined to be essential for this important step in the life cycle where the vector becomes infectious for transmitting sporozoites to people.With an increasing emphasis on advancing vector-based transgenic methods for suppression of malaria, it is important that this type of study, using modern molecular genetic tools, is done with the agent of the human disease.Understanding what P. falciparum sporozoite ligands are critical for mosquito transmission will help validate targets for vector-based transmission-blocking strategies.

View Article: PubMed Central - PubMed

Affiliation: Global Health and Infectious Diseases Research, Department of Global Health, College of Public Health, University of South Florida, Tampa, Florida, United States of America.

ABSTRACT
Malaria transmission depends on infective stages in the mosquito salivary glands. Plasmodium sporozoites that mature in midgut oocysts must traverse the hemocoel and invade the mosquito salivary glands in a process thought to be mediated by parasite ligands. MAEBL, a homologue of the transmembrane EBP ligands essential in merozoite invasion, is expressed abundantly in midgut sporozoites. Alternative splicing generates different MAEBL isoforms and so it is unclear what form is functionally essential. To identify the MAEBL isoform required for P. falciparum (NF54) sporozoite invasion of salivary glands, we created knockout and allelic replacements each carrying CDS of a single MAEBL isoform. Only the transmembrane form of MAEBL is essential and is the first P. falciparum ligand validated as essential for invasion of Anopheles salivary glands. MAEBL is the first P. falciparum ligand experimentally determined to be essential for this important step in the life cycle where the vector becomes infectious for transmitting sporozoites to people. With an increasing emphasis on advancing vector-based transgenic methods for suppression of malaria, it is important that this type of study, using modern molecular genetic tools, is done with the agent of the human disease. Understanding what P. falciparum sporozoite ligands are critical for mosquito transmission will help validate targets for vector-based transmission-blocking strategies.

Show MeSH
Related in: MedlinePlus