Prashant Kumar

Background/Objectives: This work describes the development of a new, lyophilized, live-attenuated measles–rubella (MR) vaccine formulation designed for lower-cost production in Africa. The formulation consists of a stabilizer solution (containing only non-animal-derived excipients) and high-titer MR viral bulks (produced in MRC-5 cells by a modernized process) prepared at a ratio of 95% and 5% (v/v), respectively. Methods: Both lab-scale and pilot-scale freeze-drying cycles were developed, a high-throughput RT-qPCR-based viral infectivity assay was implemented, and effective excipient screening conditions to identify stabilizing additives for MR viruses were employed. Based on the down-selected hits, candidate lyophilized MR formulations were designed, prepared, and evaluated by comparative storage stability assessments. Results: First, protein-based bulking agents (used in many commercial lyophilized MR-containing vaccines) were avoided in favor of sucrose/mannitol mixtures. Second, ~50 excipients were screened, and two additional key stabilizing components were identified (both previously reported to stabilize MR viruses): sodium phosphate buffer and urea. Next, stability assessments were performed on different variations of a candidate lyophilized MR formulation to elucidate the inter-relationships between sucrose–mannitol ratios, cake integrity, and MR virus stability. An optimized MR vaccine formulation composition (post-reconstitution) of 5% (w/v) mannitol, 5% (w/v) sucrose, 50 mM urea, 25 mM sodium phosphate buffer (pH 6.5), and 5% (v/v) viral bulks was established. When this formulation was lyophilized at lab-scale in a single-dose format, both MR viruses displayed promising stability profiles during storage under real-time and accelerated conditions. A five-dose format was then evaluated in a pilot-scale freeze-dryer by using a 2X formulation filled into larger vials, lyophilized, and then reconstituted to 1X concentration. Conclusions: Results demonstrated the feasibility of a new, lower-cost, lyophilized, multidose MR formulation for potential use with a live-attenuated MR vaccine candidate targeted for local production in Africa.

Background/Objectives: Local manufacturing of Measles-Rubella (MR) vaccines is part of a multifaceted approach to improve vaccine accessibility in Africa, yet process development and technology transfer challenges remain for large-scale production of viral bulks and lyophilized drug product. This case study describes lab-scale formulation development of a multidose, lyophilized MR vaccine candidate, leveraging the availability of concentrated bulks of Measles (MeV) and Rubella (RuV) produced in MRC-5 cells by a new bulk manufacturing process. Methods: Formulation studies utilized both high-throughput RT-qPCR viral infectivity assays and standard lyophilization measurements. The off-patent, publicly available formulation composition of a single-dose, lyophilized trivalent MMR vaccine was evaluated as a starting point to develop a multidose, bivalent lyophilized MR vaccine candidate. To identify optimized conditions, various formulation (e.g., human serum albumin, viral bulk volume), drug product (e.g., vial size, fill volume), and lyophilization (e.g., freezing rate, primary/secondary drying cycle) parameters were evaluated to lower costs and assess MR stability during lyophilization, storage, and reconstitution. Results: Real-time and accelerated stability studies were conducted with four variations of the top candidate MR formulation, filled into primary packaging selected for technology transfer and lyophilized in both lab- and pilot- scale freeze-dryers. An optimized five-dose MR vaccine formulation with 5% (v/v) bulk and 95% (v/v) stabilizer solution, filled at 2X and reconstituted to 1X concentrations, demonstrated promising stability profiles and cost reduction potential. Stability profiles at 2–8 °C were used to estimate the MR release doses needed to ensure the required expiry doses at end of shelf-life. Conclusions: Results are discussed, along with recommendations for future work, in the context of the analytical, formulation, and lyophilization challenges encountered during lab-scale development of a candidate multidose, lyophilized MR vaccine dosage form targeted for technology transfer and large-scale local production in Africa.

This study evaluated the formulation and stability of a quadrivalent glycoconjugate Shigella vaccine candidate based on four predominant strains (S. flexneri; 2a, 3a, and 6, and S. sonnei) covering ~64% of global Shigella infections. Each glycoconjugate antigen consists of a strain-specific O-polysaccharide (O-PS) covalently linked to the carrier protein IpaB, a component of the Shigella type III secretion system. First, selective competitive ELISAs were developed to measure antigenicity of the four O-PS-IpaB conjugates formulated with different adjuvants (i.e., Alhydrogel^®, AH; Adju-phos^®, AP; and CpG-1018^®, CpG). Next, the monovalent S. sonnei O-PS-IpaB conjugate was studied to elucidate interactions with aluminum salt adjuvants (AH, AP) under different solution conditions. Third, the stability profiles of AH- or AP-adjuvanted S. sonnei O-PS-IpaB conjugate in various formulations (±CpG) were determined at different temperatures. Interestingly, incubation at 25 °C for 2 weeks resulted in increased antigenicity values when the antigen was bound to AP or AH, suggesting increased epitope exposure upon adjuvant binding. When bound to AP adjuvant at pH 5.8, the best glycoconjugate antigen stability was observed at elevated temperatures. The CpG adjuvant under these conditions, however, displayed incompatibility (i.e., material loss), presumably from precipitation due to lack of interaction with AP and presence of the detergent LDAO from the bulk antigen buffer. In contrast, the glycoconjugate antigen and CpG adjuvant were both bound to the AH adjuvant and stable at 2–8 °C, pH 7.0. This AH-CpG formulation of the O-PS-IpaB conjugate antigens was identified as a promising candidate for future animal immunogenicity testing.

Exosomes are extracellular vesicles within the nanosized range that play roles in intercellular communication and thus have certain biological activities. The secretory signaling communication mechanism is an efficient way of exchanging information between cells and has been investigated as nature’s therapeutic drug carriers. This review will summarize the potential of exosomes as therapeutic tools and drug delivery vehicles for corneal pathologies. The cornea is an avascular ocular tissue, and its healing is a complex process including cell death and migration, cell proliferation and differentiation, and extracellular matrix remodeling. Here, we discussed the structure, barrier, phases, and healing cascade of cornea. We briefly reviewed the immunogenicity and toxicity of exosomes and role of exosomes in preserving cornea. Additionally, we provided combining exosome strategies with hydrogels, gene and stem cells therapy focused on corneal treatment, repair, and regeneration.

In this work, we describe compatibility assessments of a recombinant, trivalent non-replicating rotavirus vaccine (t-NRRV) candidate with a mock trivalent Sabin inactivated polio vaccine (t-sIPV). Both t-sIPV and t-NRRV are incompatible with thimerosal (TH), a preservative commonly used in pediatric pentavalent combination vaccines (DTwP-Hib-HepB) distributed in low- and middle-income countries (LMICs), preventing the development of a heptavalent combination. The compatibility of t-NRRV with a mock DTwP-Hib-HepB formulation is described in a companion paper. This case study highlights the analytical and formulation challenges encountered when combining a mock t-sIPV vaccine (unadjuvanted) with Alhydrogel^® (AH) adjuvanted t-NRRV. Selective and stability-indicating competition ELISAs were implemented to monitor antibody binding to each of the six antigens (±AH). Simple mixing caused the undesired desorption of t-NRRV from AH with the concomitant binding of t-sIPV to AH. Although the former effect was mitigated by dialyzing sIPV bulks, decreased sIPV storage stability was observed at accelerated temperatures in the bivalent combination with a rank-ordering of P[8] > P[6] > P[4] and sIPV3 > sIPV2 > sIPV1. The compatibility of AH-adsorbed t-sIPV with alternative preservatives was evaluated, and parabens (methyl, propyl) were identified for potential use in this multi-dose bivalent formulation. Along with a companion paper, the lessons learned are discussed to facilitate the future formulation development of pediatric combination vaccines with new antigens.

Drug and vaccine delivery have received considerable attention in recent years

The human body poses a spectrum of biological mechanisms operating at different levels that are important for its normal functioning and development