{
  "abstract": "Background: Clinically approved P. falciparum circumsporozoite protein (PfCSP)-based pre-erythrocytic stage malaria vaccines suffer from sub-optimal efficacy and rapidly waning memory. By decoding these limitations, we fast-tracked vaccine optimization by correcting CSPs fragile immunogenicity using a parasite-derived chaperone. Unlike other orthologues of P. falciparum heat shock protein 70 (PfHSP70), substrate-binding domain (SBD) of PfHSP70-3 is an evolutionarily conserved internal mitochondrial matrix chaperone. We demonstrate that PfHSP70-3-SBD hydrophobic region complexes with PfCSP and targets host CD91 on antigen-presenting cells to trigger cross-presentation, resulting in enhanced immune responses to PfCSP. Methods: In silico analyses predicted interactions among PfHSP70-3-SBD, PfCSP, and CD91 receptor. Recombinant PfHSP70-3-SBD and PfCSP proteins were purified and assessed for in vitro interaction using ELISA and far-western dot blot assays. BALB/c mice were immunized with alum-formulated PfCSP, with or without PfHSP70-3-SBD. PfCSP-specific IgG and IFN-{gamma} expression were evaluated by ELISA and RT-qPCR, respectively. Functional activity was assessed using transgenic Plasmodium berghei expressing PfCSP (Pb/Pf CSP), by sporozoite neutralization assay. Findings: PfHSP70-3-SBD demonstrated a specific interaction with PfCSP. The complex primarily engages CD91 receptor cluster IV, providing a potential mechanistic basis for antigen cross-presentation. Incorporation of PfHSP70-3-SBD enhanced PfCSP-specific total IgG responses and increased IFN-gamma expression in BALB/c mice, indicating improved immunogenicity upon co-formulation. Notably, immune sera neutralized Pb/Pf CSP sporozoites, delaying blood-stage patency until day 12 in 40% of C57BL/6 mice, with no detectable parasitemia in surviving mice for up to 2 months, indicating sustained efficacy against the sporozoite stage. Interpretation: Molecular chaperones, including HSPs, are currently under intense investigation for their immune-potentiating activity, leading to next-generation vaccine development. By utilizing chaperonic domains derived directly from the pathogenic agent itself to serve an essential adjuvant function, this approach reduces reliance on heterologous adjuvants while enhancing antigen-specific immunity. Funding: This work was supported by funding from Indian Council of Medical Research (IIRPSG-2024-01-03940). Keywords: Substrate-binding domain, PfHSP70-3, Adjuvant, Cross-presentation, Pre-erythrocytic stage, Plasmodium falciparum",
  "abstract_shown": true,
  "affiliations": [
    "Jawaharlal Nehru University, New Delhi, India"
  ],
  "article_type": "New results",
  "arxiv": null,
  "author_total": 10,
  "authors": [
    {
      "name": "P. Garg"
    },
    {
      "name": "C. K. Verma"
    },
    {
      "name": "K. Gupta"
    },
    {
      "name": "A. Sharma"
    },
    {
      "name": "S. Jawla"
    },
    {
      "name": "N. Jha"
    },
    {
      "name": "S. Saini"
    },
    {
      "name": "K. A. Kumar"
    },
    {
      "name": "A. Ranganathan"
    },
    {
      "affs": [
        0
      ],
      "name": "S. Singh"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/ad9c6f2ept897.bib",
  "cited_by": 0,
  "doi": "10.64898/2026.10.15.759406",
  "fulltext_url": "https://www.biorxiv.org/content/10.64898/2026.10.15.759406v1.full",
  "id": "ad9c6f2ept897",
  "issns": [],
  "landing_url": "https://www.biorxiv.org/content/10.64898/2026.10.15.759406v1",
  "language": null,
  "licence": "CC-BY-NC-ND",
  "licence_label": "CC BY-NC-ND",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by-nc-nd/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "biorxiv",
      "microbiology"
    ],
    [
      "openalex",
      "2739|Malaria Research and Control"
    ]
  ],
  "openalex": "W7222793207",
  "pdf_url": "https://www.biorxiv.org/content/10.64898/2026.10.15.759406v1.full.pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-15",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/ad9c6f2ept897.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:28:15Z",
      "native_id": "10.64898/2026.10.15.759406",
      "source": "biorxiv",
      "url": "https://www.biorxiv.org/content/10.64898/2026.10.15.759406v1"
    }
  ],
  "subjects": [
    {
      "field": "biology",
      "origin": "biorxiv:microbiology",
      "subfield": "microbiology"
    }
  ],
  "title": "Evolutionarily Conserved Plasmodium falciparum HSP70-3 Enhances the Immunogenicity of the Established Malaria Vaccine Antigen Circumsporozoite Protein through Cross-Presentation",
  "title_text": "Evolutionarily Conserved Plasmodium falciparum HSP70-3 Enhances the Immunogenicity of the Established Malaria Vaccine Antigen Circumsporozoite Protein through Cross-Presentation",
  "type": "preprint",
  "updated_at": "2026-10-30T12:28:15Z",
  "url": "https://research.draconitic.com/paper/ad9c6f2ept897",
  "venue": "bioRxiv",
  "versions": []
}