AbstractRTS,S and R21 are the only vaccines recommended by the WHO to protect children from Plasmodium falciparum (Pf) clinical malaria. Both vaccines target the Pf sporozoite surface protein circumsporozoite protein (CSP). Recent studies showed that human antibodies neutralize Pf sporozoites most efficiently when simultaneously binding to the PfCSP NANP repeat and the NPDP junction domain. However, neither RTS,S nor R21 targets this junction domain. To test the potential of the NPDP junction domain and other sites of PfCSP as innovative vaccine targets, we developed multiple vaccine candidates based on cucumber mosaic virus-like particles (CuMVTT-VLPs). These candidates vary in several aspects: the number of targeted NANP repeats, the presence or absence of the junction domain, the cleavage site, and up to three NVDP repeats within the target sequence. Immunogenicity and efficacy studies were conducted in BALB/c mice, utilizing chimeric Plasmodium berghei (Pb) sporozoites, in which the endogenous CSP has been replaced by PfCSP (Pb/PfCSP). We observed a positive association between the number of targeted NANP repeats and the induction of specific IgM/IgG antibodies. Elevated humoral responses led to enhanced protection against parasitemia after Pb/PfCSP sporozoite challenge. Especially high-avidity/affinity antibody formation and vaccine protection were NANP repeat-dependent. Intriguingly, vaccine efficacy was not enhanced by targeting sites on PfCSP other than the NANP repeats. Our data emphasize the dominant role of the NANP repeat region for induction of protective antibodies. Furthermore, we present here novel malaria vaccine candidates with an excellent immunogenic profile that confer sterile protection in mice, even in absence of adjuvants.

AbstractHantaan virus (HTNV) and Puumala virus (PUUV) are pathogenic zoonoses found in Asia and Europe, respectively. We conducted a randomized Phase 1 clinical trial of individual HTNV and PUUV DNA vaccines targeting the envelope glycoproteins (GnGc), as well as a combined HTNV/PUUV DNA vaccine delivered at varying doses using the PharmaJet Stratis® needle-free injection system (NCT02776761). Cohort 1 and 2 vaccines consisted of 2 mg/vaccination of HTNV or PUUV plasmid, respectively. Cohort 3 vaccine consisted of 2 mg/vaccination of 1:1 mixture of HTNV and PUUV vaccines. Vaccinations were administered on Days 0, 28, 56, and 168. The vaccines were safe and well tolerated. Neutralizing antibody responses were elicited in 7/7 (100%) subjects who received the HTNV DNA (Cohort 1) and 6/6 (100%) subjects who received the PUUV DNA (Cohort 2) vaccines alone. The combination vaccine resulted in 4/9 (44%) seroconversion against both viruses. After the first two vaccinations, the seroconversion rates for the HTNV and PUUV vaccines were >80%.

AbstractLassa virus (LASV) is a rodent-borne mammarenavirus that causes tens to hundreds of thousands of human infections annually in Western Africa. Approximately 20% of these infections progress to Lassa fever (LF), an acute disease with case–fatality rates from ≈20–70%. Currently, there are no approved vaccines or specific therapeutics to prevent or treat LF. The LASV genome consists of a small (S) segment that has two genes, GP and NP, and a large (L) segment that has two genes, L and Z. In both segments, the two genes are separated by non-coding intergenic regions (IGRs). Recombinant LASVs (rLASVs), in which the L segment IGR was replaced with the S segment IGR or in which the GP gene was codon-deoptimized, lost fitness in vitro, were highly attenuated in vivo, and, when used as vaccines, protected domesticated guinea pigs from otherwise lethal LASV exposure. Here, we report the generation of rLASV/IGR-CD, which includes both determinants of attenuation and further enhances the safety of the vaccine compared with its predecessors. rLASV/IGR-CD grew to high titers in Vero cells, which are approved for human vaccine production, but did not cause signs of disease or pathology in guinea pigs. Importantly, guinea pigs vaccinated with rLASV/IGR-CD were completely protected from disease and death after a typically lethal exposure to wild-type LASV. Our data support the development of rLASV/IGR-CD as a live-attenuated LF vaccine with stringent safety features.

Streptococcus suis infection represents a major challenge in pig farming and public health due to its zoonotic potential and diverse serotypes, while existing vaccines lack effective cross-protection. This study employed reverse vaccinology and immunoinformatics to identify 8 conserved proteins across 11 prevalent serotypes of S. suis. 16 candidate epitopes were selected to design three multi-epitope antigens against S. suis (designated as MEASs), which fused with a dendritic cell-targeting peptide to improve antigen presentation in host. Purified MEASs displayed favorable cross-reactogenicity against 29 serotype-specific antiserums. Robust humoral and cellular immune responses can be induced by MEAS 1 and MEAS 3 in a mouse model, which provided substantial protection against virulent strains from two different serotypes. In particular, their immune serums exhibited positive opsonization effects within bloodstream and macrophage phagocytosis. Taken together, we identified two promising MEASs with excellent cross-protection, offering potential in preventing S. suis infections in a mouse model.

The development and rollout of mRNA vaccines during COVID-19 marked a significant advancement in vaccinology, yet public hesitation to vaccination was prevalent, indicating the potential risk that future mRNA-based medical innovations will fail to be adopted. Utilizing a combined approach of large language models with manual validation and unsupervised machine learning, we conducted a social listening analysis to assess attitudes towards mRNA vaccines and therapeutics on Twitter from June 2022 to May 2023, contrasting online perspectives with data from the Vaccine Adverse Event Reporting System. Our findings reveal widespread negative sentiment and a global lack of confidence in the safety, effectiveness, and trustworthiness of mRNA vaccines and therapeutics, with frequent discussions of severe vaccine side effects, rumors, and misinformation. This underscores the need for targeted communication strategies to foster acceptance of medical treatments and strengthen public trust in order to enhance societal resilience to future health challenges.

Despite their efficacy, the currently available polio vaccines, oral polio vaccine (OPV) and inactivated polio vaccine (IPV), possess inherent flaws posing significant challenges in the global eradication of polio. OPV, which uses live Sabin attenuated strains, carries the risk of reversion to pathogenic forms and causing vaccine-associated paralytic poliomyelitis (VAPP) and vaccine-derived polio disease (VDPD) in incompletely vaccinated or immune-compromised individuals. Conventional IPVs, which are non-replicative, are more expensive to manufacture and introduce biohazard and biosecurity risks due to the use of neuropathogenic strains in production. These types of limitations have led to a call by the Global Polio Eradication Initiative and others for the development of updated polio vaccines. We are developing a novel Ultraviolet-C radiation (UVC) inactivation method that preserves immunogenicity and is compatible with attenuated strains of polio. The method incorporates an antioxidant complex, manganese-decapeptide-phosphate (MDP), derived from the radioresistant bacterium Deinococcus radiodurans. The inclusion of MDP protects the immunogenic neutralizing epitopes from damage during UVC inactivation. The novel vaccine candidate, ultraIPVTM, produced using these methods demonstrates three crucial attributes: complete inactivation, which precludes the risk of vaccine-associated disease; use of non-pathogenic strains to reduce production risks; and significantly enhanced yield of doses per milligram of input virus, which could increase vaccine supply while reducing costs. Additionally, ultraIPVTM retains antigenicity post-freeze-thaw cycles, a testament to its robustness.