Most malariologists believe that optimal malaria vaccines will induce protective immune responses against different stages of the parasite's life cycle. A multiple antigen peptide (MAP) vaccine based on the Plasmodium yoelii circumsporozoite protein (PyCSP) protects mice against sporozoite challenge by inducing antibodies that prevent sporozoites from invading hepatocytes. A purified recombinant protein vaccine based on the P. yoelii merozoite surface protein-1 (PyMSP-1) protects mice against challenge with infected erythrocytes, presumably by inducing antibodies against the erythrocytic stage of the parasite. We now report studies designed to determine if the PyMSP-1 vaccine protects against challenge with sporozoites, the stage encountered in the field, and if immunization with a combination of the PyCSP and PyMSP-1 vaccines provides additive or synergistic protection against sporozoite challenge. In two experiments, using TiterMax or Ribi R-700 as adjuvant, 3 of 19 mice immunized with the PyMSP-1 vaccine were completely protected against sporozoite challenge. The remaining mice had significantly delayed onset and lower levels of peak parasitemia than did control mice (11.1 +/- 2.8% vs. 36.7 +/- 1.6% in experiment #2, P < 0.01). Immunization with the combination vaccine reduced by approximately 50% the level of antibodies induced to PyCSP and PyMSP-1, as compared to that induced by the individual components. However, in two experiments, there was evidence of additive protection. Six of 19 (31.6%) immunized with the PyCSP vaccine, 3 of 19 (15.8%) immunized with the PyMSP-1 vaccine, and 10 of 19 (52.6%) immunized with the combination were completely protected against sporozoit challenge. This modest increase in protection in the combination group may be a reflection of additive anti-PyCSP and anti-PyMSP-1 immunity, since mice in the combination group had diminished levels of antibodies to each components. These studies indicate that considerable work may be required to optimize the construction, delivery, and assessment of multi-stage malaria vaccines.
This research output has an Altmetric Attention Score of 3. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 07 December 2004.
All research outputs
#9,514,662
of 27,776,330 outputs
Outputs from Immunology Letters
#601
of 1,977 outputs
Outputs of similar age
#10,496
of 30,867 outputs
Outputs of similar age from Immunology Letters
#3
of 13 outputs
Altmetric has tracked 27,776,330 research outputs across all sources so far. This one is in the 42nd percentile – i.e., 42% of other outputs scored the same or lower than it.
So far Altmetric has tracked 1,977 research outputs from this source. They receive a mean Attention Score of 5.0. This one is in the 30th percentile – i.e., 30% of its peers scored the same or lower than it.
Older research outputs will score higher simply because they've had more time to accumulate mentions. To account for age we can compare this Altmetric Attention Score to the 30,867 tracked outputs that were published within six weeks on either side of this one in any source. This one is in the 7th percentile – i.e., 7% of its contemporaries scored the same or lower than it.
We're also able to compare this research output to 13 others from the same source and published within six weeks on either side of this one. This one is in the 1st percentile – i.e., 1% of its contemporaries scored the same or lower than it.
