Background and objectives Convalescent plasma (CP) has been embraced as a safe therapeutic option for coronavirus disease 2019 (COVID‐19), while other treatments are developed. Severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is not transmissible by transfusion, but bloodborne pathogens remain a risk in regions with high endemic prevalence of disease. Pathogen reduction can mitigate this risk; thus, the objective of this study was to evaluate the effect of riboflavin and ultraviolet light (R + UV) pathogen reduction technology on the functional properties of COVID‐19 CP (CCP). Materials and methods COVID‐19 convalescent plasma units (n = 6) from recovered COVID‐19 research donors were treated with R + UV. Pre‐ and post‐treatment samples were tested for coagulation factor and immunoglobulin retention. Antibody binding to spike protein receptor‐binding domain (RBD), S1 and S2 epitopes of SARS‐CoV‐2 was assessed by ELISA. Neutralizing antibody (nAb) function was assessed by pseudovirus reporter viral particle neutralization (RVPN) assay and plaque reduction neutralization test (PRNT). Results Mean retention of coagulation factors was ≥70%, while retention of immunoglobulins was 100%. Starting nAb titres were low, but PRNT₅₀ titres did not differ between pre‐ and post‐treatment samples. No statistically significant differences were detected in levels of IgG (P ≥ 0·3665) and IgM (P ≥ 0·1208) antibodies to RBD, S1 and S2 proteins before and after treatment. Conclusion R + UV PRT effects on coagulation factors were similar to previous reports, but no significant effects were observed on immunoglobulin concentration and antibody function. SARS‐CoV‐2 nAb function in CCP is conserved following R + UV PRT treatment.

Background and Objective: Convalescent plasma (CP) has been embraced as a safe therapeutic option for coronavirus disease 2019 (COVID-19) while other treatments are developed. However, transfusion-transmitted disease is a risk, particularly in regions with high endemic prevalence of transfusion-transmissible diseases. Pathogen reduction can mitigate this risk; thus, the objective of this study was to evaluate the effect of riboflavin and ultraviolet light (R+UV) pathogen reduction technology on the functional properties of CCP. Materials and Methods: CCP units (n = 6) from recovered COVID-19 research donors were treated with R+UV. Pre- and post-treatment samples were tested for coagulation factor and immunoglobulin retention. Antibody binding to spike protein receptor binding domain (RBD), S1, and S2 epitopes of SARS-CoV-2 was assessed by ELISA. Neutralizing antibody (nAb) function was assessed by pseudovirus reporter viral particle neutralization (RVPN) assay and plaque reduction neutralization test (PRNT). Results: Mean retention of coagulation factors was ≥ 70% while retention of immunoglobulins was 100%. Starting nAb titers were low, but PRNT ₅₀ titers did not differ between pre- and post-treatment samples. No statistically significant differences were detected in levels of IgG ( P ≥ 0.3665) and IgM ( P ≥ 0.1208) antibodies to RBD, S1, and S2 proteins before and after treatment. Conclusion: R+UV PRT effects on coagulation factors were similar to previous reports, but no significant effects were observed on immunoglobulin concentration and antibody function. SARS-CoV-2 nAb function in COVID-19 convalescent plasma is conserved following R+UV PRT treatment.

Background: A novel platform to produce whole-virion vaccines using riboflavin and ultraviolet (UV) light for photochemical inactivation has been developed. We previously reported on the potential for this platform to produce a safe and effective inactivated whole-virion SARS-CoV-2 vaccine. Feasibility studies used a hamster infection challenge model to explore the effects of route of administration and adjuvants on immune responses elicited by the vaccine candidate. Here, we utilized the same animal model to evaluate the dose response to the vaccine candidate in combination with the adjuvant CpG1018. Methods: A pilot batch of the vaccine candidate was produced at a contract development and manufacturing organization (CDMO) for use in this study. A two-dose intramuscular regimen at three antigen concentrations formulated with CpG1018 adjuvant was assessed against a live SARS-CoV-2 (USA-WA-1/2020) challenge. Results: The vaccine elicited dose-dependent neutralizing antibody responses, with peak PRNT₅₀ titers exceeding 1:5120. Vaccination significantly reduced lung viral burden and mitigated pulmonary pathology compared to controls. Antibodies persisted up to 154 days post-vaccination and neutralized Delta and Omicron (Jn.1) variants but showed limited activity against XBB.1.5. Flow cytometry revealed enhanced CD4⁺ Th1-biased responses in higher-dose groups. Conclusions: These findings demonstrate the protective efficacy of the SolaVAX SARS-CoV-2 vaccine candidate and support further evaluation of this vaccine production platform.