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At least 19 recordsLinked to original sources
PubMed2025

Vaccine efficacy of NVX-CoV2373 against SARS-CoV-2 infection in adolescents in the USA: an ancillary study to a phase 3, observer-blinded, randomised, placebo-controlled trial.

BACKGROUND: Although existing COVID-19 vaccines are known to be highly effective against severe disease and death, data are needed to assess their ability to reduce SARS-CoV-2 infection. We aimed to estimate the efficacy of the NVX-CoV2373 protein subunit vaccine against SARS-CoV-2 infection, regardless of symptoms, among adolescents. METHODS: We performed an ancillary observational study (SNIFF) to the phase 3, observer-blinded, randomised, placebo-controlled PREVENT-19 trial that assessed vaccine efficacy against symptomatic COVID-19 in the USA. Participants in the PREVENT-19 trial included healthy adolescents aged 12-17 years and with no history of laboratory-confirmed SARS-CoV-2 infection. They were randomly assigned (2:1) to receive either the NVX-CoV2373 (Novavax, Gaithersburg, MD, USA) vaccine (immediate NVX-CoV2373 group) or placebo (delayed NVX-CoV2373 group) on days 0 and 21 (initial series). After 2 months, in a crossover series, participants received two doses, 21 days apart, of the intervention that they did not receive in their initial series. Participants at 47 of the PREVENT-19 sites were invited to participate in the SNIFF study and self-collect nasal swabs at home twice weekly for SARS-CoV-2 testing to assess vaccine efficacy against SARS-CoV-2 infection. This primary outcome was defined as the first identification of SARS-CoV-2 detected by RT-PCR, regardless of symptoms, with onset within 4 weeks after the second dose of the initial vaccination series until the second dose of the crossover series. Secondary outcomes were vaccine efficacy against asymptomatic and minimally symptomatic SARS-CoV-2 infection, durability of vaccine efficacy against SARS-CoV-2 infection, and durability of vaccine efficacy against asymptomatic and minimally symptomatic infections. Outcomes were analysed in the modified intention-to-treat population, which included all participants without previous SARS-CoV-2 infection and was restricted to participants enrolled within 4 weeks of the second dose of the primary (primary analysis population) or crossover (post-crossover analysis population) series. This study is registered with ClinicalTrials.gov (NCT04611802). FINDINGS: Between June 1 and Dec 17, 2021, 1196 (53·2%) of the 2247 adolescent participants recruited in the PREVENT-19 trial enrolled in the SNIFF study. The primary analysis population included 471 participants in the immediate NVX-CoV2373 group and 220 in the delayed NVX-CoV2373 group. Incidence of SARS-CoV-2 infection was 14·9 cases per 100 person-years (95% CI 7·9-25·5) in the immediate group and 54·2 cases per 100 person-years (33·6-82·9) in the delayed group; vaccine efficacy was 73·5% (95% CI 47·1-86·7; p=0·0002). Incidence of minimally symptomatic or asymptomatic SARS-CoV-2 infection was 10·3 cases per 100 person-years (95% CI 4·7-19·6) in the immediate group and 36·1 cases per 100 person-years (19·8-60·7) in the delayed group; vaccine efficacy was 72·8% (95% CI 37·1-88·2; p=0·0023). After the second crossover dose, incidence of SARS-CoV-2 was 14·6 cases per 100 person-years (95% CI 8·6-23·0) in the immediate group (receiving placebo at crossover) and 9·1 cases per 100 person-years (3·0-21·3) in the delayed group, with a durability ratio of 160·3 (95% CI 59·5-431·6; p=0·35). Almost all infections after crossover were minimally symptomatic or asymptomatic, with a durability ratio of 151·4 (55·9-410·4; p=0·41). INTERPRETATION: Among adolescents participating in the PREVENT-19 trial during the delta (B.1.617.2) variant wave of the COVID-19 pandemic, the NVX-CoV2373 vaccine was highly efficacious against SARS-CoV-2 infection regardless of symptoms, indicating its potential to reduce the reservoir of infections that contribute to community transmission. FUNDING: US Department of Health and Human Services, Administration for Strategic Preparedness and Response, Biomedical Advanced Research and Development Authority, National Institute of Allergy and Infectious Diseases, and National Institutes of Health.

Adolescent↗
PubMed1987

Safety and efficacy of a recombinant DNA Plasmodium falciparum sporozoite vaccine.

A recombinant DNA Plasmodium falciparum sporozoite vaccine produced in Escherichia coli (FSV-1) was tested in doses of 10 micrograms to 800 micrograms protein in fifteen volunteers. No serious adverse reactions occurred. Antibodies that reacted with P falciparum sporozoite antigens by enzyme-linked immunoassay developed in twelve of the volunteers. The highest antibody titres induced were similar to those resulting from lifelong natural exposure to sporozoite-infected mosquitoes. Postimmunization serum samples from a majority of volunteers mediated the circumsporozoite (CS) precipitation reaction and inhibited sporozoite invasion of hepatoma cells in vitro. Serum from the three volunteers who received 800 micrograms doses reacted with the surface of sporozoites in an immunofluorescence assay. Six immunised volunteers receiving a fourth dose of FSV-1 and two non-immunised controls were challenged by bites of mosquitoes infected from cultured P falciparum gametocytes. Parasitaemia did not develop in the volunteer with the highest titre of CS antibodies, and parasitaemia was delayed in two other immunised volunteers. This study confirms that human beings can be protected by CS protein subunit vaccines and provides a framework for the further development and testing of more immunogenic sporozoite vaccines.

Adult↗
PubMed1989

Immune response gene regulation of immunity to Plasmodium berghei sporozoites and circumsporozoite protein vaccines. Overcoming genetic restriction with whole organism and subunit vaccines.

We conducted a series of experiments to define Ir gene regulation of the immune response to Plasmodium berghei sporozoites and circumsporozoite (CS) protein-derived subunit vaccines. The studies demonstrated that there is no apparent genetic restriction of the capacity to develop protective immunity against a large sporozoite challenge after immunization with irradiation-attenuated P. berghei sporozoites; that the Th response to (Asp-Pro-Ala-Pro-Pro-Asn-Ala-Asn)n, the predominant protective B epitope on the P. berghei CS protein, is genetically restricted and regulated by Class II genes (I-Ab) and by genes in the Class I region (H-2Dk) or telomeric to this region; and that this restriction can be overcome by immunization with a r protein including the entire P. berghei CS protein. The results support the development of full length human CS protein vaccines to take advantage of all potential T epitopes on this protein.

Amino Acid Sequence↗
PubMedDate not supplied

Recombinant cholera toxin B subunit and gene fusion proteins for oral vaccination.

The B subunit portion of cholera toxin (CTB) is a safe and effective oral immunizing agent in humans, affording protection against both cholera and diarrhoea caused by enterotoxigenic Escherichia coli producing heat-labile toxin (LT) (Clemens et al., 1986; 1988). CTB may also be used as a carrier of various "foreign" antigens suitable for oral administration. To facilitate large-scale production of CTB for vaccine development purposes, we have constructed recombinant overexpression systems for CTB proteins in which the CTB gene is under the control of strong foreign (non-cholera) promoters and in which it is also possible to fuse oligonucleotides to the CTB gene and thereby achieve overexpression of hybrid proteins (Sanchez and Holmgren, 1989; Sanchez et al., 1988). We here expand these findings by describing overexpression of CTB by a constitutive tacP promoter as well as by the T7 RNA-polymerase promoter, and also by describing gene fusions leading to overexpression of several hybrid proteins between heat-stable E. coli enterotoxin (STa)-related peptides to either the amino or carboxy ends of CTB. Each of the hybrid proteins, when tested as immunogens in rabbits, stimulated significant anti-STa as well as anti-CTB antibody formation, although the anti-STa antibody levels attained (c.a. 1-15 micrograms/ml specific anti-STa immunoglobulin) were too low to give more than partial neutralization of STa intestinal challenge in baby mice. The hybrid proteins also had a near-native conformation, as apparent from their oligomeric nature and their strong reactivity with both a neutralizing antibody against the B subunit and a neutralizing monoclonal antibody (mAb) against STa.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1991

Stimulation of adherent cells by addition of purified proteins of viral hemorrhagic septicemia virus to trout kidney cell cultures.

Purified proteins of the virus causing viral hemorrhagic septicemia in the trout were added to cultures on semisolid medium of leukocytes obtained from either healthy or immunized rainbow trout. Adherent cells were specifically stimulated by the glycoprotein of the viral spikes and, to a lesser extent, by the nucleoproteins. In contrast, a specific memory response was associated more with the nucleoproteins than with the glycoprotein when leukocytes from trout immunized with the virus were employed. These results suggest the necessity of employing both proteins in subunit vaccination trials and the possibility of using this assay to select the proper epitopes for genetically engineered proteins during subunit vaccine development.

Animals↗
PubMed2026

Chimeric vaccine based on Iraqi HLA alleles against a predominant local Escherichia coli phylogroup.

INTRODUCTION: Escherichia coli remains amongst the most globally important pathogens implicated in severe clinical manifestations. The progressive rise in multidrug-resistant strains highlights the urgent need for new vaccines. Therefore, this study was designed to develop a new multi-epitope vaccine containing the most conserved epitopes across E. coli pathotypes. Consequently, the study aimed to investigate the immunoadjuvant role of faecal microbiota transplantation in enhancing vaccine efficacy. METHODS: Eighteen of the most conserved B-cell and T-cell epitopes of FimH, LptD, and BamA proteins were selected and included in a single construct. During the epitope selection process, HLA alleles predominant in the Iraqi population, as reported in previous studies, were used as criteria for selecting T-cell epitopes. The chimeric protein was expressed in BL21 E. coli and purified using affinity chromatography. Vaccine cross-protective immunity and protection were tested in in vivo experiments. Different formulations were used in the experimental evaluation: three doses of 100 μg of purified chimeric protein, injected intraperitoneally alone or encapsulated in PLGA nanoparticles, after faecal microbiota transplantation with and without gut microbiota modulation mediated by a cocktail of antibiotics. IgG1, IL-4, INF-γ, and NLRP3 levels were measured at 30 and 75 days after the first immunisation dose. Immunised mice were challenged with the local B2 UPEC phylogroup, and protection efficacy was considered 48 h later. Finally, the histological effects of the different chimeric protein formulations on the liver were assessed. RESULTS: All vaccine formulations except those after faecal microbiota transplantation without gut microbiota modulation induce significant increases in IgG1, IL-4, and INF-γ levels at different times. Only vaccination after faecal microbiota transplantation with gut microbiota modulation elicited robust NLRP3 levels at 30 and 75 days after, and this was linked to the highest reduction in bladder bacterial load by 813-fold compared to the other formulations, as well as the mildest effect on liver histological changes. DISCUSSION: These results demonstrated that the chimeric vaccine provides preliminary protection against a local B2 UPEC isolate. Furthermore, modulating gut microbiota via faecal transplantation markedly enhances the immunogenicity and protective efficacy of vaccination, suggesting its adjuvanticity.

Animals↗
PubMed1988

Mechanisms of immunodominance in T-cell recognition, with applications to vaccine design.

Immunodominant T-cell antigenic sites can so dominate a response that their presence leads to high responsiveness and their absence to low responsiveness. Therefore, it is important to locate such sites for vaccine development. Factors that lead to immunodominance include features extrinsic to the structure of the site itself, such as the major histocompatibility complex (MHC) molecules of the host and the types of fragments produced by processing of the protein antigen before the T cell sees it. They also include factors intrinsic to the structure of the T-cell site, that determine a repertoire of potential immunodominant sites from which the extrinsic factors select a subset that will be immunodominant in a given individual. We have focused on one of these intrinsic factors, helical amphipathicity, that we have found to be a common feature among both helper and cytotoxic T-cell antigenic sites, suggesting that the same physical principles apply to sites seen in association with class I and class II MHC molecules. We have used this feature to locate immunodominant epitopes on the circumsporozoite protein of the Plasmodium falciparum malaria parasite and the envelope protein of the AIDS virus. Both helper and cytotoxic T-cell epitopes were identified. At least in the case of the helper T-cell sites, it was striking that the same sites in both the malaria and AIDS proteins studied that were immunodominant in the mouse were also immunodominant in the human, an indication that the same principles apply across species, and that the animal model will be useful for identifying sites to be used in vaccines for humans. These sites have been coupled with neutralizing antibody sites to produce artificial constructs that can elicit antibodies. It is hoped that the rational design of more complex versions of these artificial constructs will produce vaccines that are more effective than the natural pathogen proteins used in subunit vaccines, since such pathogen protein antigens have been selected through evolution to evade the immune system, not to optimize immunogenicity.

Animals↗
PubMed2026

A Multiepitope Intranasal Adenoviral Vaccine Induces Robust Mucosal Immunity and Protection against SARS‑CoV‑2.

BACKGROUND: Vaccination has been central to mitigating the COVID-19 pandemic; however, the continual emergence of SARS-CoV-2 variants of concern (VOCs) has reduced the effectiveness of current intramuscular vaccines that primarily target the Spike (S) protein. Although updated formulations are periodically introduced, there remains a critical need for next-generation vaccine platforms capable of inducing broad, variant-independent protection. Here we evaluate a heterologous intranasal (i.n.) prime-boost vaccination strategy using bovine adenoviral (BAd) and chimpanzee adenoviral (ChAd) vectors expressing the S1 subunit in combination with either full-length membrane (M) and nucleocapsid (N) proteins (Ad-S1 + N + M) or multiepitope constructs derived from M and N (Ad-S1 + Epi/N + Epi/M). The constructs were incorporated with the autophagy-inducing peptide C5 (AIP-C5) to enhance antigen-specific T-cell responses. RESULTS: In BALB/c mice, Ad-S1 + Epi/N + Epi/M vaccination induced robust S1-specific immunity while simultaneously inducing strong N- and M-specific humoral and cellular responses that were comparable to or greater than those induced by Ad-S1 + N + M. All S1-containing formulations generated high neutralizing antibody titers (~ 3.8 log₁₀) against Omicron B.1.1.529 and BA.2.86 variants, although titers against the ancestral Wuhan strain were approximately one log₁₀ lower. In K18-hACE2 mice, i.n. immunization with S1-expressing vectors provided near-complete protection against BA.2.86 challenge, with undetectable lung viral titers and viral genome copies. CONCLUSION: An i.n. multiepitope adenoviral vaccine incorporating conserved SARS-CoV-2 antigens induces robust mucosal, humoral, and cellular immune responses and confers significant protection following SARS-CoV-2 challenge.

Animals↗
PubMed2026

An immunoinformatics-based multi-epitope vaccine candidate confers cross-protection against two Actinobacillus pleuropneumoniae serovars.

Porcine contagious pleuropneumonia (PCP) is caused by Actinobacillus pleuropneumoniae (APP) and inflicts heavy economic losses on the swine industry. However, existing inactivated vaccines provide limited cross-protection, highlighting the need for improved vaccine strategies. In this study, we combined pangenome analysis with subtractive proteomics to screen the APP core genome and identified 11 potential antigens. Seven of them showed immunoreactivity by ELISA and Western blotting. These antigens, together with the ApxI-III toxins, were used for T and B cell epitope prediction. On this basis, a multi-epitope fusion protein MVAPP was constructed. In silico molecular docking with swine immune receptors and immune simulations suggested that MVAPP has the potential to induce immune responses. In the mouse model, that MVAPP elicited specific antibody responses, shifted the splenic T-cell subset distribution toward CD4+ T cells, and provided partial protection against challenge with strains from two serovars. In conclusion, MVAPP represents a potential multi-epitope vaccine candidate for further development against APP.

Animals↗
PubMed1989

Quality assessment of DNA vaccines: hepatitis-B vaccine.

Vaccines manufactured following "classical" methods contain inactivated or infectious but attenuated viruses or bacteria. In some instances, the inactivated agents are purified. In other cases, the vaccines contain protein subunits or practically pure polysaccharides. It is generally accepted that the final product cannot be completely characterised and that therefore extensive "in-process" controls are necessary to prove the consistent quality of such vaccines. Control tests are carried out on the substrate, the pooled bulk vaccine and on the final containers. Vaccines produced by recombinant DNA techniques consist of pure proteins. The production is carried out by the multiplication of the "working seed" under well-defined standardised conditions followed by clarification, extraction, purification, formulation. "In-process" controls are incorporated at each step and specifications for acceptance are formulated. The biological methods used for the classical vaccines are completed by physicochemical and immunological determinations of antigen content, identity and purity for the "new generation" products. The requirements for the manufacturers are based on the documents issued by the World Health Organisation and by the national control authorities. The marketing of vaccines is based on a lot by lot release procedure, whereby each lot is tested by the manufacturer and the national control authority before use. Hepatitis-B vaccine, derived from transformed yeast cells, is the first and sole vaccine which has obtained a world-wide license. The quality assessment of this vaccine has been achieved following the requirements for the new generation of biomolecules. It is an example for future vaccines.

Animals↗
PubMed1990

Isolation of recombinant fragments of the major outer-membrane protein of Chlamydia trachomatis: their potential as subunit vaccines.

Recombinant fragments of the major outer-membrane protein (MOMP) of Chlamydia trachomatis, expressed at high levels in Escherichia coli, were isolated and purified. Antisera to the recombinant proteins reacted preferentially with overlapping synthetic peptides covering the immunoaccessible variable segments of MOMP. These sera also reacted in a species-specific manner with the surface of intact infectious elementary bodies, and in a Chlamydia genus-specific manner in assays using denatured or bound chlamydial antigens. The ability of recombinant MOMP preparations to elicit antibody to the surface of chlamydial elementary bodies raises the possibility that these proteins may be useful for chlamydial vaccine development.

Animals↗
PubMed2026

Synthetic long peptide and DNA personalized cancer vaccines induce robust neoantigen-specific T cell responses in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) is unresponsive to standard immunotherapies despite harboring cancer neoantigens capable of eliciting T cell responses. We completed two phase 1 clinical trials (NCT03956056 and NCT03122106) evaluating safety and immunogenicity of synthetic long peptide (SLP) and DNA personalized cancer vaccines (PCVs). PCVs were administered after resection and adjuvant chemotherapy. Tumor/normal whole-exome sequencing, RNA sequencing, and pVACtools were used to identify and prioritize candidate PCV neoantigens. PCVs were well tolerated without any grade ≥3 adverse events. Neoantigen-specific responses were demonstrated by interferon-γ enzyme-linked immunospot and intracellular cytokine staining. Expanded T cell receptor clonotypes were sequenced and transduced into autologous peripheral blood mononuclear cells to confirm neoantigen specificity. When compared with a contemporaneous institutional propensity-matched cohort, PCV patients demonstrated a trend toward prolonged median overall survival (4.4 versus 3.5 years, log-rank P = 0.23). Overall, PDAC PCVs are safe and feasible and elicit polyclonal T cell responses, linking prioritized cancer neoantigens to functional antitumor immunity.

Humans↗
PubMed2026

Comparative Genomics-Guided Epitope Prioritization and in Silico Design of a Multi-Epitope DNA Vaccine Candidate Against Megalocytivirus pagrus 1.

Megalocytivirus pagrus 1 infection is a World Organisation for Animal Health-listed aquatic animal disease caused by a virus species comprising the RSIV, ISKNV, and TRBIV genogroups. Here, we integrated comparative genomics and immunoinformatics to prioritize a multi-epitope protein construct, pMEV, and to design a DNA vaccine candidate encoding it, with emphasis on RSIV-type infection relevant to rock bream aquaculture. Analysis of 61 complete genomes identified 28 core gene clusters, from which myristoylated membrane protein (MMP) and major capsid protein (MCP) were prioritized as source antigens for epitope screening. Four cytotoxic T-cell, five helper T-cell, and five linear B-cell epitope candidates were selected based on sequence-based screening and exploratory peptide-MHC docking. The selected epitopes were assembled with rock bream beta-defensin-3, PADRE, and peptide linkers to generate the 283-aa pMEV construct. Sequence-based physicochemical analyses indicated properties relevant to subsequent structural and expression-based evaluation, while computationally refined structural modeling identified nine putative conformational B-cell epitope regions. TLR3 docking, normal mode analysis, and a 200-ns molecular dynamics simulation characterized the structural behavior of the selected computational complex without inferring receptor activation. C-ImmSim further generated model-dependent generic humoral and helper T-cell-associated response patterns within a mammalian-based simulation framework. Finally, the pMEV coding sequence was codon-optimized and incorporated into an in silico pcDNA3.1(+)-based DNA vaccine design. Collectively, this study provides a comparative genomics-guided framework for prioritizing an experimentally testable multi-epitope DNA vaccine candidate against M. pagrus 1, while construct expression, immunogenicity, and protective efficacy remain to be evaluated experimentally.

Animals↗
PubMed2026

Computational prediction of a multi-epitope Human Metapneumovirus vaccine candidate through integrated reverse vaccinology and pan-genomic approaches.

Human metapneumovirus (HMPV) is a primary cause of global respiratory infections yet no approved vaccine currently exists. This study computationally predicts a multi-epitope vaccine candidate using a diverse dataset of 65 HMPV sequences spanning five continents. Following the screening of lead proteins for antigenicity and virulence, fifteen highly conserved MHC-I, MHC-II and B-cell epitopes were prioritized. These were integrated with a putative L7/L12 adjuvant using optimized AAY, GPGPG, and KK linkers to design three constructs (HMPV_V1-V3). Structural validation identified HMPV-V2 as the lead candidate that exhibits a Z-score of-5.24 and 87.7% of residues in favored Ramachandran regions indicating excellent stereochemical quality and structural stability. In silico docking indicated a strong predicted binding affinity between HMPV-V2 and the TLR4 receptor (energy: -969.2). Immune simulations predicted a robust adaptive response characterized by high IgG1 titers, memory B-cell maturation, and a Th1-dominant cytokine profile. Furthermore, molecular dynamics simulations suggested exceptional structural integrity for HMPV-V2, maintaining a low RMSD of 8.213 and RMSF of 0.737 throughout the simulation. Optimized in silico cloning into the pET28a (+) vector indicated a high potential for protein expression in E. coli systems. While these findings provide a theoretically grounded blueprint for vaccine development, this study is entirely computational and lacks experimental validation. Further in vitro and in vivo testing is required to confirm the actual safety and immunogenicity of the proposed candidate.

Metapneumovirus↗
PubMed1989

Antibody response of pseudorabies virus subunit-vaccinated pigs to viral nucleocapsid proteins following low-dose virus challenge of immunity.

The antibody response to pseudorabies virus nucleocapsid proteins (NCP) was evaluated by the western immunoblot analysis before and after challenge of immunity by nasal inoculation of 10(2.3) plaque-forming units of virus in 10 pigs that had been vaccinated with pseudorabies virus envelope glycoproteins. Antibody to 5 NCP with molecular mass of 140, 63, 41, 34, and 23 kD was first detected in vaccinated and nonvaccinated pigs on day 14 after challenge of immunity. Antibody to 2 of the 5 NCP continued to be detected through day 113 in 9 of 10 vaccinated pigs. Beyond day 32, antibody to NCP was not detected in 1 vaccinated pig. The 23-, 34-, and 41-kD proteins were the most immunogenic. Antibody to each of these proteins was first detected on day 14 in 10, 10, and 8 pigs, respectively. Seven, 6, and 8 pigs, respectively, were antibody-positive for these proteins on day 113. The 140- and 63-kD proteins were the least immunogenic. Antibody to these proteins was detected in 8 and 9 pigs, respectively, on day 14, and in 4 and 5 pigs, respectively, on day 113. Chi-square analysis for dependency indicated that the antibody response to the 140- and 63-kD proteins was interdependent. These results suggested that combinations of NCP may be useful as nonvaccine diagnostic antigens.

Animals↗
PubMed1976

Comparison of the humoral and cellular immune response after immunization with live, UV inactivated herpes simplex virus and a subunit vaccine and efficacy of these immunizations.

Antibody and cell-mediated immune responses were measured in rabbits immunized with live, UV inactivated herpes simplex virus or with a subunit vaccine containing envelope proteins. All the types of immunization procedures induced the production of antibody as well as a specific cellular immunity. Furthermore, the subunit vaccine was as effective as the immunization with live or UV inactivated virus to prevent death upon challenge with live HSV. Live HSV induced a transient unresponsiveness of both B and T cells to in vitro stimulation with various mitogens.

Animals↗
PubMed1990

Plasmodium berghei subunit vaccine: repeat synthetic peptide of circumsporozoite protein comprising T- and B-cell epitopes fails to confer immunity.

In the murine malaria model induced by Plasmodium berghei, we studied the immunogenicity of the repeat region of the circumsporozoite (CS) protein, which is the main target of the antibody response in infected animals. We immunized several strains with a synthetic peptide--Y(DPPPPNPN)3--corresponding to one of the two P. berghei repeat sequences in complete Freund's adjuvant. Only C57BL/6 immune sera reacted with the synthetic peptide in ELISA and with the native CS protein on P. berghei sporozoites, as detected by immunofluorescence. From lymph node cells of immunized C57BL/6 we isolated two repeat-specific T-cell lines which proliferated in the presence of the synthetic peptide or the recombinant CS protein. We analysed the protective role of this repeat-specific response by injecting infectious sporozoites into mice immunized with irradiated sporozoites or with the repeat peptide. The percentage of mice developing parasitaemia was 80-90% in the peptide-immunized group and only 10-20% in the group immunized with irradiated sporozoites. Anti-repeat antibody titres were comparable in the two groups. On the basis of these results, we can conclude that the T- and B-cell response to the CS repeat obtained with this synthetic peptide immunization is not sufficient for a protective immunity.

Amino Acid Sequence↗