Engineered Nanovesicles Expressing Bispecific Single Chain Variable Fragments to Protect against SARS-CoV-2 Infection

Abstract

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in high morbidity and mortality rates worldwide. Although the epidemic has been controlled in many areas and numerous patients have been successfully treated, the risk of reinfection persists due to the low neutralizing antibody titers and weak immune response. To provide long-term immune protection for infected patients, novel bispecific CB6/dendritic cell (DC)-specific intercellular adhesion molecule 3-grabbing nonintegrin (SIGN) nanovesicles (NVs) were constructed to target both the SARS-CoV-2 spike protein (S) and the DC receptors for virus neutralization and immune activation. Herein, we designed NVs expressing both CB6 and DC-SIGN single chain variable fragments (scFvs) on the surface to block SARS-CoV-2 invasion and activate DC function. Monophosphoryl lipid A (MPLA) was loaded into the CB6/DC-SIGN NVs as an adjuvant to promote this process. The CB6/DC-SIGN NVs prevented a pseudovirus expressing the S protein from infecting the target cells expressing high levels of angiotensin-converting enzyme 2 in vitro. Additionally, CB6/DC-SIGN NVs admixed with Sexpressing pseudoviruses activated the DCs, which was promoted by the adjuvant MPLA loaded in the NVs. Using a mouse model, we also confirmed that the CB6/DC-SIGN NVs effectively improved the neutralizing antibody titer and inhibited the growth of tumors expressing the S protein after 3 weeks of treatment. This potential NV-based treatment not only exerts a blocking effect by binding the S protein in the short term but may also provide patients with long-term protection against secondary infections.

Peptide-TLR7/8a-Coordinated DNA Vaccines Elicit Enhanced Immune Responses against Infectious Diseases

“…Initially, we assessed the transfection efficacy of these PBAE NPs using a plasmid encoding GFP in the 293T cell. The GFP-expressing cells were visualized using a fluorescence microscope and quantified by flow cytometry. , Compared to the PEI group, the PBAE, PP, and PPT groups exhibited brighter green fluorescence (Figure a). Flow cytometry analysis revealed that the PP and PPT groups had approximately 56.0% GFP-positive cells at 3 days post-transfection, while the PEI and unmodified PBAE exhibited GFP-positive cell percentages of 12.1 and 39.6%, respectively (Figure b).…”