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Daily Plasmodium yoelii infective mosquito bites do not generate protection or suppress previous immunity against the liver stage.

Pollock T, Leitao R, Galan-Rodriguez C, Wong KA, Rodriguez A - Malar. J. (2011)

Bottom Line: It was observed that while the bites of normal infected mosquitoes do not generate strong antibody responses and protection, the bites of irradiated mosquitoes result in high levels of anti-sporozoite antibodies and protection against liver stage Plasmodium infection.Exposure to daily infected mosquito bites did not eliminate the protection acquired previously with a experimental liver stage vaccine.While infective mosquito bites do not induce a protective liver stage response, they also do not interfere with previously acquired liver stage protective responses, even if they induce a complete blood stage infection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology, Division of Medical Parasitology, New York University School of Medicine, New York, NY 10010, USA.

ABSTRACT

Background: Human populations that are naturally subjected to Plasmodium infection do not acquire complete protection against the liver stage of this parasite despite prolonged and frequent exposure. However, sterile immunity against Plasmodium liver stage can be achieved after repeated exposure to radiation attenuated sporozoites. The reasons for this different response remain largely unknown, but a suppressive effect of blood stage Plasmodium infection has been proposed as a cause for the lack of liver stage protection.

Methods: Using Plasmodium yoelii 17XNL, the response generated in mice subjected to daily infective bites from normal or irradiated mosquitoes was compared. The effect of daily-infected mosquito bites on mice that were previously immunized against P. yoelii liver stage was also studied.

Results: It was observed that while the bites of normal infected mosquitoes do not generate strong antibody responses and protection, the bites of irradiated mosquitoes result in high levels of anti-sporozoite antibodies and protection against liver stage Plasmodium infection. Exposure to daily infected mosquito bites did not eliminate the protection acquired previously with a experimental liver stage vaccine.

Conclusions: Liver stage immunity generated by irradiated versus normal P. yoelii infected mosquitoes is essentially different, probably because of the blood stage infection that follows normal mosquito bites, but not irradiated. While infective mosquito bites do not induce a protective liver stage response, they also do not interfere with previously acquired liver stage protective responses, even if they induce a complete blood stage infection. Considering that the recently generated anti-malaria vaccines induce only partial protection against infection, it is encouraging that, at least in mouse models, immunity is not negatively affected by subsequent exposure and infection with the parasite.

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Anti-sporozoite antibody titres. Serum from each mouse was serially diluted and used to stain P. yoelii sporozoites. The titers represent the inverse of the highest dilution at which sporozoites could still be detected. Each circle represents an individual mouse. Significant differences between the group of normal mosquito bite and the other groups were found (P < 0.05) when comparing with ANOVA).
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Figure 3: Anti-sporozoite antibody titres. Serum from each mouse was serially diluted and used to stain P. yoelii sporozoites. The titers represent the inverse of the highest dilution at which sporozoites could still be detected. Each circle represents an individual mouse. Significant differences between the group of normal mosquito bite and the other groups were found (P < 0.05) when comparing with ANOVA).

Mentions: Antibody levels in the groups of mice that were immunized with two doses of the irradiated sporozoite vaccine followed or not by the bites of normal infected mosquitoes showed no significant differences in their anti-sporozoite antibody levels, suggesting that after immunization, the antibody levels are not affected by the bites of infected mosquitoes (Figure 3), even if the mice developed a full blood stage infection (Figure 2).


Daily Plasmodium yoelii infective mosquito bites do not generate protection or suppress previous immunity against the liver stage.

Pollock T, Leitao R, Galan-Rodriguez C, Wong KA, Rodriguez A - Malar. J. (2011)

Anti-sporozoite antibody titres. Serum from each mouse was serially diluted and used to stain P. yoelii sporozoites. The titers represent the inverse of the highest dilution at which sporozoites could still be detected. Each circle represents an individual mouse. Significant differences between the group of normal mosquito bite and the other groups were found (P < 0.05) when comparing with ANOVA).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3102649&req=5

Figure 3: Anti-sporozoite antibody titres. Serum from each mouse was serially diluted and used to stain P. yoelii sporozoites. The titers represent the inverse of the highest dilution at which sporozoites could still be detected. Each circle represents an individual mouse. Significant differences between the group of normal mosquito bite and the other groups were found (P < 0.05) when comparing with ANOVA).
Mentions: Antibody levels in the groups of mice that were immunized with two doses of the irradiated sporozoite vaccine followed or not by the bites of normal infected mosquitoes showed no significant differences in their anti-sporozoite antibody levels, suggesting that after immunization, the antibody levels are not affected by the bites of infected mosquitoes (Figure 3), even if the mice developed a full blood stage infection (Figure 2).

Bottom Line: It was observed that while the bites of normal infected mosquitoes do not generate strong antibody responses and protection, the bites of irradiated mosquitoes result in high levels of anti-sporozoite antibodies and protection against liver stage Plasmodium infection.Exposure to daily infected mosquito bites did not eliminate the protection acquired previously with a experimental liver stage vaccine.While infective mosquito bites do not induce a protective liver stage response, they also do not interfere with previously acquired liver stage protective responses, even if they induce a complete blood stage infection.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Microbiology, Division of Medical Parasitology, New York University School of Medicine, New York, NY 10010, USA.

ABSTRACT

Background: Human populations that are naturally subjected to Plasmodium infection do not acquire complete protection against the liver stage of this parasite despite prolonged and frequent exposure. However, sterile immunity against Plasmodium liver stage can be achieved after repeated exposure to radiation attenuated sporozoites. The reasons for this different response remain largely unknown, but a suppressive effect of blood stage Plasmodium infection has been proposed as a cause for the lack of liver stage protection.

Methods: Using Plasmodium yoelii 17XNL, the response generated in mice subjected to daily infective bites from normal or irradiated mosquitoes was compared. The effect of daily-infected mosquito bites on mice that were previously immunized against P. yoelii liver stage was also studied.

Results: It was observed that while the bites of normal infected mosquitoes do not generate strong antibody responses and protection, the bites of irradiated mosquitoes result in high levels of anti-sporozoite antibodies and protection against liver stage Plasmodium infection. Exposure to daily infected mosquito bites did not eliminate the protection acquired previously with a experimental liver stage vaccine.

Conclusions: Liver stage immunity generated by irradiated versus normal P. yoelii infected mosquitoes is essentially different, probably because of the blood stage infection that follows normal mosquito bites, but not irradiated. While infective mosquito bites do not induce a protective liver stage response, they also do not interfere with previously acquired liver stage protective responses, even if they induce a complete blood stage infection. Considering that the recently generated anti-malaria vaccines induce only partial protection against infection, it is encouraging that, at least in mouse models, immunity is not negatively affected by subsequent exposure and infection with the parasite.

Show MeSH
Related in: MedlinePlus