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Addition of histamine to subcutaneously injected Plasmodium berghei sporozoites increases the parasite liver load and could facilitate whole-parasite vaccination.

Pfeil J, Heine JF, Mueller AK - Malar. J. (2015)

Bottom Line: The parasite liver load following subcutaneous SPZ administration can be significantly increased by co-administration of histamine and heparin.However, despite a relatively high parasite liver load, the protective efficacy of histamine-supplemented subcutaneous immunization remains inferior as compared to intravenous SPZ administration.Further investigations are needed to reveal the effect of histamine supplementation and subcutaneous SPZ administration on the acquisition of protective immunity.

View Article: PubMed Central - PubMed

Affiliation: Centre for Childhood and Adolescent Medicine (General Paediatrics), University Hospital, Im Neuenheimer Feld 430, 69120, Heidelberg, Germany. Johannes.Pfeil@med.uni-heidelberg.de.

ABSTRACT

Background: Whole-parasite immunization remains the benchmark in malaria vaccine development. A major bottleneck in the translation of whole-parasite immunization towards routine vaccination is the mode of administration, since high degrees of protection are currently only achieved by intravenous, and not by intradermal or subcutaneous injection of viable parasites. It is known that only a small proportion of subcutaneously administered parasites reach the subsequent liver stage and low parasite liver load was shown to be associated with low protective efficacy. The objective of this analysis was to evaluate whether the liver load following subcutaneous parasite injection could be augmented by co-administration of pro-inflammatory or anti-coagulatory drugs.

Methods: In the C57BL/6 Plasmodium berghei ANKA model, the clinical outcome (time to patent blood stage infection and survival) and relative parasite liver load was assessed in mice infected by subcutaneous or intramuscular sporozoite (SPZ) administration in the presence or absence of histamine and heparin supplementation in comparison to intravenously administered SPZ. In addition, a vaccination experiment was carried out to assess the protective efficacy of an improved, histamine-supplemented subcutaneous immunization regimen.

Results: The parasite liver load following subcutaneous SPZ administration can be significantly increased by co-administration of histamine and heparin. A dose-dependent relation between parasite liver load and histamine dosage was observed. However, despite a relatively high parasite liver load, the protective efficacy of histamine-supplemented subcutaneous immunization remains inferior as compared to intravenous SPZ administration.

Conclusions: Histamine supplementation might facilitate the future development of a non-intravenous whole-parasite vaccine. Further investigations are needed to reveal the effect of histamine supplementation and subcutaneous SPZ administration on the acquisition of protective immunity.

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Related in: MedlinePlus

Relative 18S rRNA liver load following subcutaneous infection in relation to intravenously infected control animals. Animals were infected sc by a single injection of 104 SPZ. SPZ were administered either without supplementation (sc, n = 7) or supplemented with 3 μg histamine and 5 IU heparin (3 μg sc; n = 7) or 100 μg histamine and 5 IU heparin (100 μg sc, n = 5). The liver load was obtained at 48 hrs after infection and is expressed in relation to the median 18S rRNA liver load of four iv-infected control mice.
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Fig4: Relative 18S rRNA liver load following subcutaneous infection in relation to intravenously infected control animals. Animals were infected sc by a single injection of 104 SPZ. SPZ were administered either without supplementation (sc, n = 7) or supplemented with 3 μg histamine and 5 IU heparin (3 μg sc; n = 7) or 100 μg histamine and 5 IU heparin (100 μg sc, n = 5). The liver load was obtained at 48 hrs after infection and is expressed in relation to the median 18S rRNA liver load of four iv-infected control mice.

Mentions: Following this clinical observation, further experiments were conducted to evaluate whether parasitic liver burden as determined by both qRT-PCR and in vivo imaging were increased in animals infected with SPZ plus histamine compared to animals infected with SPZ in PBS only. In animals infected sc by 104 SPZ in PBS supplemented with 3 μg histamine and 5 IU of heparin (3 μg sc; n = 9), the mean parasitic liver load was increased by approximately 2.5-fold (P <0.05) as compared to animals infected with 104 SPZ sc in PBS (sc; n = 11). A wide inter-individual variance in parasite liver burden was noted (Figure 3). Based on the clinical outcome described above, a dose-dependent effect of histamine supplementation on the resulting parasite liver load was assumed. According to this hypothesis, further experiments compared the parasite liver load of mice infected subcutaneous with 104 SPZ in PBS (sc, n = 7), or in PBS supplemented with 5 IU of heparin and either 3 μg (3 μg sc; n = 7) or an increased dosage of 100 μg (100 μg sc; n = 5) of histamine. The parasite liver load was calculated by the transcriptional abundance of 18SrRNA versus the GAPDH reference. Four control mice were infected at the same time point with equivalent doses of SPZ iv, and the liver load of sc infected mice was expressed in relation to the median liver load of these iv-infected control animals. The median relative liver burden detected was 2, 3 and 10% in the sc, 3 μg sc and 100 μg sc groups, respectively, and subject to wide inter-individual variance (Figure 4).Figure 3


Addition of histamine to subcutaneously injected Plasmodium berghei sporozoites increases the parasite liver load and could facilitate whole-parasite vaccination.

Pfeil J, Heine JF, Mueller AK - Malar. J. (2015)

Relative 18S rRNA liver load following subcutaneous infection in relation to intravenously infected control animals. Animals were infected sc by a single injection of 104 SPZ. SPZ were administered either without supplementation (sc, n = 7) or supplemented with 3 μg histamine and 5 IU heparin (3 μg sc; n = 7) or 100 μg histamine and 5 IU heparin (100 μg sc, n = 5). The liver load was obtained at 48 hrs after infection and is expressed in relation to the median 18S rRNA liver load of four iv-infected control mice.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4318155&req=5

Fig4: Relative 18S rRNA liver load following subcutaneous infection in relation to intravenously infected control animals. Animals were infected sc by a single injection of 104 SPZ. SPZ were administered either without supplementation (sc, n = 7) or supplemented with 3 μg histamine and 5 IU heparin (3 μg sc; n = 7) or 100 μg histamine and 5 IU heparin (100 μg sc, n = 5). The liver load was obtained at 48 hrs after infection and is expressed in relation to the median 18S rRNA liver load of four iv-infected control mice.
Mentions: Following this clinical observation, further experiments were conducted to evaluate whether parasitic liver burden as determined by both qRT-PCR and in vivo imaging were increased in animals infected with SPZ plus histamine compared to animals infected with SPZ in PBS only. In animals infected sc by 104 SPZ in PBS supplemented with 3 μg histamine and 5 IU of heparin (3 μg sc; n = 9), the mean parasitic liver load was increased by approximately 2.5-fold (P <0.05) as compared to animals infected with 104 SPZ sc in PBS (sc; n = 11). A wide inter-individual variance in parasite liver burden was noted (Figure 3). Based on the clinical outcome described above, a dose-dependent effect of histamine supplementation on the resulting parasite liver load was assumed. According to this hypothesis, further experiments compared the parasite liver load of mice infected subcutaneous with 104 SPZ in PBS (sc, n = 7), or in PBS supplemented with 5 IU of heparin and either 3 μg (3 μg sc; n = 7) or an increased dosage of 100 μg (100 μg sc; n = 5) of histamine. The parasite liver load was calculated by the transcriptional abundance of 18SrRNA versus the GAPDH reference. Four control mice were infected at the same time point with equivalent doses of SPZ iv, and the liver load of sc infected mice was expressed in relation to the median liver load of these iv-infected control animals. The median relative liver burden detected was 2, 3 and 10% in the sc, 3 μg sc and 100 μg sc groups, respectively, and subject to wide inter-individual variance (Figure 4).Figure 3

Bottom Line: The parasite liver load following subcutaneous SPZ administration can be significantly increased by co-administration of histamine and heparin.However, despite a relatively high parasite liver load, the protective efficacy of histamine-supplemented subcutaneous immunization remains inferior as compared to intravenous SPZ administration.Further investigations are needed to reveal the effect of histamine supplementation and subcutaneous SPZ administration on the acquisition of protective immunity.

View Article: PubMed Central - PubMed

Affiliation: Centre for Childhood and Adolescent Medicine (General Paediatrics), University Hospital, Im Neuenheimer Feld 430, 69120, Heidelberg, Germany. Johannes.Pfeil@med.uni-heidelberg.de.

ABSTRACT

Background: Whole-parasite immunization remains the benchmark in malaria vaccine development. A major bottleneck in the translation of whole-parasite immunization towards routine vaccination is the mode of administration, since high degrees of protection are currently only achieved by intravenous, and not by intradermal or subcutaneous injection of viable parasites. It is known that only a small proportion of subcutaneously administered parasites reach the subsequent liver stage and low parasite liver load was shown to be associated with low protective efficacy. The objective of this analysis was to evaluate whether the liver load following subcutaneous parasite injection could be augmented by co-administration of pro-inflammatory or anti-coagulatory drugs.

Methods: In the C57BL/6 Plasmodium berghei ANKA model, the clinical outcome (time to patent blood stage infection and survival) and relative parasite liver load was assessed in mice infected by subcutaneous or intramuscular sporozoite (SPZ) administration in the presence or absence of histamine and heparin supplementation in comparison to intravenously administered SPZ. In addition, a vaccination experiment was carried out to assess the protective efficacy of an improved, histamine-supplemented subcutaneous immunization regimen.

Results: The parasite liver load following subcutaneous SPZ administration can be significantly increased by co-administration of histamine and heparin. A dose-dependent relation between parasite liver load and histamine dosage was observed. However, despite a relatively high parasite liver load, the protective efficacy of histamine-supplemented subcutaneous immunization remains inferior as compared to intravenous SPZ administration.

Conclusions: Histamine supplementation might facilitate the future development of a non-intravenous whole-parasite vaccine. Further investigations are needed to reveal the effect of histamine supplementation and subcutaneous SPZ administration on the acquisition of protective immunity.

Show MeSH
Related in: MedlinePlus