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Infection and Immunity, January 1999, p. 342-349, Vol. 67, No. 1
Division of Parasitic Diseases, National
Center for Infectious Diseases, Centers for Disease Control and
Prevention, Public Health Service, U.S. Department of Health and Human
Services, Atlanta, Georgia 30341,1 and
Laboratory of Malaria Research, National Institute of Allergy
and Infectious Diseases, National Institutes of Health, Bethesda,
Maryland 208922
Received 26 May 1998/Returned for modification 24 July
1998/Accepted 1 October 1998
Merozoite surface protein 1 is a candidate for blood-stage vaccines
against malaria parasites. We report here an immunization study of
Saimiri monkeys with a yeast-expressed recombinant protein containing the C terminus of Plasmodium vivax merozoite
surface protein 1 and two T-helper epitopes of tetanus toxin
(yP2P30Pv20019), formulated in
aluminum hydroxide (alum) and block copolymer P1005. Monkeys immunized
three times with yP2P30Pv20019 in
block copolymer P1005 had significantly higher prechallenge titers of
immunoglobulin G (IgG) antibodies against the immunogen and asexual
blood-stage parasites than those immunized with
yP2P30Pv20019 in alum, antigen alone, or phosphate-buffered saline (PBS) (P < 0.05).
Their peripheral blood mononuclear cell proliferative responses to
immunogen stimulation 4 weeks after the second immunization were also
significantly higher than those from the PBS control group
(P < 0.05). Upon challenge with 100,000 asexual
blood-stage parasites 5 weeks after the last immunization, monkeys
immunized with yP2P30Pv20019 in block copolymer P1005 had prepatent periods longer than those for the
control alone group (P > 0.05). Three of the five
animals in this group also had low parasitemia (peak parasitemia,
0019-9567/99/$00.00+0
Partial Protection against Plasmodium vivax
Blood-Stage Infection in Saimiri Monkeys by Immunization
with a Recombinant C-Terminal Fragment of Merozoite Surface
Protein 1 in Block Copolymer Adjuvant
20 parasites/µl of blood). Partially protected monkeys had significantly higher levels of prechallenge antibodies against the immunogen than
those unprotected (P < 0.05). There was also a
positive correlation between the prepatent period and titers of IgG
antibodies against the immunogen and asexual blood-stage parasites and
a negative correlation between accumulated parasitemia and titers of
IgG antibodies against the immunogen (P < 0.05).
These results indicate that when combined with block copolymer and
potent T-helper epitopes, the yeast-expressed
P2P30Pv20019 recombinant protein
may offer some protection against malaria.
*
Corresponding author. Mailing address: Immunology
Branch, Mail Stop F-12, Centers for Disease Control and Prevention,
4770 Buford Highway, Atlanta, GA 30341. Phone: (770) 488-4047. Fax: (770) 488-4454. E-mail: aal1{at}cdc.gov.
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