The combined virus immunization was done as described in the legend of Fig. and causing more than 300 million infections annually. Recent efforts to prevent the spread of this disease and control it through chemotherapy and spraying of residual insecticides largely have failed because of the development of widespread drug resistance of the parasites, insecticide resistance of the mosquito vectors, and various socioeconomic factors. For these reasons, the development of a vaccine as an additional tool for malaria control has become most urgent. The feasibility of developing an effective malaria vaccine was demonstrated by the finding that immunization with irradiated sporozoites confers Ansatrienin B complete protection (sterile immunity) against this infection not only to rodents and monkeys but also to humans (1). Since then, several sporozoite antigens, shared or not with those of liver stages, were identified as potential targets of protective immune responses. One of these antigensthe circumsporozoite (CS) protein, a major sporozoite surface antigen Ansatrienin B and liver stage componenthas been investigated extensively and shown to elicit neutralizing antibodies and cell-mediated immunity (1, 2). In two experimental rodent malaria systems (and followed by the inoculation of a re vaccinia virus expressing the same plasmodial sequences, results in extensive protection against this infection (5). In the current study, we have extended this experimental approach to can prime as well as boost the protective response elicited by re viruses expressing sequences of the CS protein. Based on this observation, it is hoped that infected mosquito bites may, in the Ansatrienin B future, reinforce and prolong the protective effect of vaccination of Ansatrienin B individuals living in malaria endemic areas. MATERIALS AND METHODS Engineering re Influenza Viruses Expressing a CTL or B Cell Epitope of the CS Protein of The re influenza virus expressing the B cell epitope of the CS protein Rabbit Polyclonal to OR52E2 of (WSN/PfB1) was constructed by inserting the plasmodial amino acid sequence (NANP)3 into antigenic site B of the WSN/hemagglutinin. The FluPf virus was made by inserting the ORF encoding the plasmodial peptide KPKDELDYENDIEKKICKMEKCS after a leader peptide sequence in a bicistronic neuraminidase gene from WSN virus. Transfection of CS Protein. An CS protein of the NF54 strain was isolated from the plasmid pA13 (7). This DNA fragment was blunt-ended by treatment with a large fragment of DNA polymerase (Klenow), purified by agarose gel electrophoresis, and cloned into the CS gene under control of the vaccinia virus earlyClate promoter p7.5, the -galactosidase gene under control of the vaccinia virus late promoter p11, and flanking regions from the vaccinia virus thymidine kinase gene. To generate vaccinia CS re, the insertion vector pJRpfCS was introduced by homologous recombination into the thymidine kinase locus of the vaccinia virus genome. The re virus was selected by -galactosidase expression and purified. The re vaccinia virus expressing the CS gene from the 7G8 strain of has been described (8). Animals. Female (5C8 weeks old) BALB/c (H-2d), C3H/HeOuJ (C3H) (H-2k), and C57BL/10SnJ (B10) (H-2b) mice were immunized with WSN/PfB1 for determination of their antibody response. For CD8+ T cell induction, B10BR and C3H mice (both H-2k) were used. Mice were purchased from The Jackson Laboratory or the National Institutes of Health, Frederick, MD. Cells and Cell Culture Media. LM1 cells (H-2k) were used as antigen- presenting cells or as target cells in CD8+ T cell assays (9). They were cultured in high glucose DMEM (Life Technologies, Grand Island, NY) supplemented as described. The medium used in the enzyme-linked immunospot (ELISPOT) assay and for the culture of immune lymphocytes was high glucose DMEM supplemented with 10% fetal calf serum, 10 mM Hepes, 1% EL-4 cell supernatant, 5 10?5 M 2-mercaptoethanol, and 2 mM l-glutamine (DMEM-EL4 medium). Peptides and Lipopeptide. A 23-mer peptide, KPKDELDYENDIEKKICKMEKCS, designated as P1, kindly was provided to us by A. Lal, Centers for Disease Control. This peptide contains the previously described CTL epitope of the CS protein of the 7G8 strain of recognized by B10.BR mice (10). Five overlapping 10-mer peptides were synthesized based on the sequence of this 23-mer, namely: PF1 = KPKDELDYEN; PF2 = DELDYENDIE; PF3 = DYENDIEKKI; PF4 = NDIEKKICKM; and PF5 = EKKICKMEKC. The strain specificity of this epitope was determined by using a 22-mer peptide that has the amino acid sequence of the corresponding region of the NF54 strain of the CS protein of sporozoites of the 7G8 strain were obtained by salivary gland dissection of infected mosquitoes, kindly provided to us by I. Schneider of the Walter Reed Army Institute of Research. For the immunization of mice, 105 sporozoites were injected i.v. as an initial immunizing dose as well as a booster. Routes of Immunizations,.