A stable live bacterial vaccine

Abstract

Formulating vaccines into a dry form enhances its thermal stability. This is critical to prevent administering damaged and ineffective vaccines, and to reduce its final cost. A number of vaccines in the market as well as those being evaluated in the clinical setting are in a dry solid state; yet none of these vaccines have achieved long-term stability at high temperatures. We used spray-drying to formulate a recombinant live attenuated Listeria monocytogenes (Lm; expressing Francisella tularensis immune protective antigen pathogenicity island protein IglC) bacterial vaccine into a thermostable dry powder using various sugars and an amino acid. Lm powder vaccine showed minimal loss in viability when stored for more than a year at ambient room temperature (∼23°C) or for 180days at 40°C. High temperature viability was achieved by maintaining an inert atmosphere in the storage container and removing oxygen free radicals that damage bacterial membranes. Further, in vitro antigenicity was confirmed by infecting a dendritic cell line with cultures derived from spray dried Lm and detection of an intracellularly expressed protective antigen. A combination of stabilizing excipients, a cost effective one-step drying process, and appropriate storage conditions could provide a viable option for producing, storing and transporting heat-sensitive vaccines, especially in regions of the world that require them the most.

Evaluation of the thermal stability and the protective efficacy of spray-dried HPV vaccine, Gardasil® 9

“…33 An alternative that has been well researched by us and others is to formulate vaccines into a dry form. [20][21][22][23][24][25]34,35 An optimum vaccine formulation in a dry form with stabilizing excipients will eliminate the need for uninterrupted cold-chain and significantly reduce the overall cost of a vaccine. Such a thermostable vaccine could potentially facilitate the goal of universal vaccination against HPV.…”

“…We have previously shown that these excipients, when used in varying concentrations, provide stability to different vaccine types by decreasing the hygroscopicity and crystallinity of the formulations. 20,[22][23][24][25] Further, the spray drying parameters were optimized from our previous spray drying studies for various vaccines. 20,22 A dry powder yield of 91.52% (w/w) was obtained after spray drying the Gardasil® 9 vaccine; further, a VLPs loading of~7 µg (initial VLPs loading prior to spray drying~10 µg) per mg of dry powder (70% VLPs loading efficiency) was achieved.…”

“…For storing, the spray-dried powders were loaded into hydroxypropyl methylcellulose (HPMC) capsules (size 3) and placed in amber-colored serum bottles (referred to as storage bottles) at 4°C, 25°C (RTroom temperature), and 40°C, as described previously. 20 As a control, Gardasil® 9 liquid suspension was also stored at the above storage conditions in storage bottles. PharmaKeep® KD-20 packets (combined antioxidant and moisture protectant; Mitsubishi Gas Chemical Company, Inc.) were placed in the storage bottles for protection from moisture and oxygen scavengers.…”

“…[16][17][18][19] In addition to spray drying, excipients such as sugars, surfactants, proteins, and polymers play an important role in stabilizing the vaccine during manufacture, storage, and transportation. [20][21][22] In this study, we spray-dried the commercially available Gardasil® 9 vaccine with stabilizing excipients. Gardasil® 9 is made up of nine VLPs (derived from HPV6, 11,16,18,31,33,45,52, and 58) absorbed on an aluminum adjuvant (amorphous aluminum hydroxyphosphate sulfate).…”

Developments in the formulation and delivery of spray dried vaccines

“… 70 This also may be the case for viral or bacterial membranes. Research from Muttil et al 71 suggested formation of hydrogen bonds between hydroxyl group of the sugars and the phosphate group in the lipid bilayer of live attenuated Listeria monocytogenes during spray drying. Furthermore, to maximize the hydrogen bonding with a protein, the sugar molecule should firmly fit the irregular surface of the protein.…”