Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2022 Sep 29:13:1005476.
doi: 10.3389/fimmu.2022.1005476. eCollection 2022.

Sterile protection and transmission blockade by a multistage anti-malarial vaccine in the pre-clinical study

Mitsuhiro Iyori  1 , Andrew M Blagborough  2 , Tetsushi Mizuno  3 , Yu-Ichi Abe  1 , Mio Nagaoka  1 , Naoto Hori  1 , Iroha Yamagoshi  1 , Dari F Da  4 , William F Gregory  2 , Ammar A Hasyim  1 , Yutaro Yamamoto  1 , Akihiko Sakamoto  1 , Kunitaka Yoshida  1 , Hiroaki Mizukami  5 , Hisatoshi Shida  6 , Shigeto Yoshida  1
Affiliations

Sterile protection and transmission blockade by a multistage anti-malarial vaccine in the pre-clinical study

Mitsuhiro Iyori et al. Front Immunol. .

Abstract

The Malaria Vaccine Technology Roadmap 2013 (World Health Organization) aims to develop safe and effective vaccines by 2030 that will offer at least 75% protective efficacy against clinical malaria and reduce parasite transmission. Here, we demonstrate a highly effective multistage vaccine against both the pre-erythrocytic and sexual stages of Plasmodium falciparum that protects and reduces transmission in a murine model. The vaccine is based on a viral-vectored vaccine platform, comprising a highly-attenuated vaccinia virus strain, LC16m8Δ (m8Δ), a genetically stable variant of a licensed and highly effective Japanese smallpox vaccine LC16m8, and an adeno-associated virus (AAV), a viral vector for human gene therapy. The genes encoding P. falciparum circumsporozoite protein (PfCSP) and the ookinete protein P25 (Pfs25) are expressed as a Pfs25-PfCSP fusion protein, and the heterologous m8Δ-prime/AAV-boost immunization regimen in mice provided both 100% protection against PfCSP-transgenic P. berghei sporozoites and up to 100% transmission blocking efficacy, as determined by a direct membrane feeding assay using parasites from P. falciparum-positive, naturally-infected donors from endemic settings. Remarkably, the persistence of vaccine-induced immune responses were over 7 months and additionally provided complete protection against repeated parasite challenge in a murine model. We propose that application of the m8Δ/AAV malaria multistage vaccine platform has the potential to contribute to the landmark goals of the malaria vaccine technology roadmap, to achieve life-long sterile protection and high-level transmission blocking efficacy.

Keywords: LC16m8Δ; PfCSP; Pfs25; adeno-associated virus (AAV); malaria; plasmodium falciparum; vaccine.

PubMed Disclaimer

Conflict of interest statement

The authors have read the journal’s policy and declare the following conflicts of interest: Authors SY, HS, HM and MI are named inventors on filed patents related to viral-vectored malaria vaccines (2022-24221). HS is a named inventor on a filed patent related to LC16m8Δ (WO 2005/054451 A1). Neither of these products has been commercialized. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Protective efficacy against low-dose sporozoites. (A) Construction of recombinant m8Δ and AAV. HA, hemagglutinin; p7.5, 7.5 promoter; pCMVie, CMV immediate early promoter; S, signal sequence; F, FLAG epitope tag; G6S, GGGGGGS hinge sequence; G, VSV-G TM; WPRE, woodchuck hepatitis virus posttranscriptional regulatory element. (B) Western blotting of viral-transduced HEK293T cells. (C, E) Protective efficacy in Balb/c mice (C) and ICR mice (E) immunized with m8Δ/AAV-Pf(s25-CSP) (n = 10) and m8Δ/AAV-PfCSP (n = 10) against 1,000 PfCSP/Pb sporozoites at day 28 (Balb/c) or day 40 (ICR) after the last immunization. P values were calculated by log-rank (Mantel–Cox) tests versus the PBS group. (D, F) IgG antibodies against PfCSP and Pfs25 at 41 days after priming “P” and 27 days after boosting “B” in Balb/c mice (D), or 41 days after priming and 39 days after boosting in ICR mice (F). P values were calculated using Mann–Whitney tests. ****p < 0.0001.
Figure 2
Figure 2
Protective efficacy against high-dose sporozoites. (A, B) Protective efficacy in Balb/c mice immunized with m8Δ/AAV-Pf(s25-CSP) (n = 10 for both short-term and long-term studies) and Ad/AAV-Pf(s25-CSP) (n = 10 for short-term and n = 7 for long-term studies) after challenge with 2,500 PfCSP/Pb sporozoites. Sporozoite challenges were conducted at day 29 (A), short-term) and day 102 (B), long-term) after the last immunization. P values were calculated by log-rank (Mantel–Cox) tests versus the PBS group or each vaccine group. (C, D) IgG antibodies against PfCSP (C) and Pfs25 (D) in the protected mice in (A) were periodically monitored. P values were calculated by repeated measures two-way ANOVA with Sidak’s multiple comparisons test for the vaccine type. *p < 0.05; ****p < 0.0001.
Figure 3
Figure 3
TB efficacy. (A, B) TB efficacy in mice immunized with m8Δ/AAV-Pf(s25-CSP) at day 37 (A), (n = 3) and day 236 (B), (wn = 5) after the last immunization. Each data point represents the oocyst number from a single blood-fed mosquito and horizontal lines indicate the mean number. (C) The sera from immunized mice at day 115 after the last immunization were tested for a direct membrane feeding assay. A summary of the transmission-reducing activity (TRA) and TB activity (TBA) for the indicated dilution ratio of the sera from m8Δ/AAV-Pf(s25-CSP) and Ad/AAV-Pf(s25-CSP) is shown. P values were calculated either using Mann–Whitney tests for TRA or Fisher’s exact probability tests for TBA versus the control groups. **p < 0.01; ***p < 0.0001; ****p < 0.0001.
Figure 4
Figure 4
Multiple parasite exposure. (A) Protective efficacy in mice immunized with m8Δ/AAV-Pf(s25-CSP) (n = 10) after challenge by the bites of PfCSP/Pb sporozoite-infected mosquitoes at day 26 after the last immunization. (B, C) Protective efficacy in the protected mice in (A) against 2,500 (B), day 86) and 10,000 PfCSP/Pb sporozoites (C), day 100). (D) TB efficacy in the protected mice at day 276 (n = 5) versus naïve mice (n = 4). (E) IgG antibodies against PfCSP and Pfs25 at the indicated time points before each challenge and TB studies. P values (day 25 versus others) were calculated using ANOVA followed by Dunnett’s multiple comparisons test. *p < 0.05; **p < 0.01; ***p < 0.0001; ****p < 0.0001.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

References

    1. WHO . World malaria report 2021. Geneva, Switzerland: WHO; (2021).
    1. WHO . More malaria cases and deaths in 2020 linked to Covid-19 disruptions. Geneva, Switzerland: WHO; (2021).
    1. Chandramohan D, Zongo I, Sagara I, Cairns M, Yerbanga RS, Diarra M, et al. . Seasonal malaria vaccination with or without seasonal malaria chemoprevention. N Engl J Med (2021) 385(11):1005–17. doi: 10.1056/NEJMoa2026330 - DOI - PubMed
    1. RTS,S Clinical Trials Partnership . Efficacy and safety of RTS,S/AS01 malaria vaccine with or without a booster dose in infants and children in Africa: Final results of a phase 3, individually randomised, controlled trial. Lancet (2015) 386(9988):31–45. doi: 10.1016/S0140-6736(15)60721-8 - DOI - PMC - PubMed
    1. Kidokoro M, Tashiro M, Shida H. Genetically stable and fully effective smallpox vaccine strain constructed from highly attenuated vaccinia LC16m8. Proc Natl Acad Sci USA (2005) 102(11):4152–7. doi: 10.1073/pnas.0406671102 - DOI - PMC - PubMed

Publication types

LinkOut - more resources