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Definitions

• the invention relates generally to the fields of microbiology, vaccines, and lyophilization, and more specifically to methods for lyophilizing Bordetella bacteria and lyophilized formulations made according to such methods.
• BPZE1 a live attenuated B. pertussis strain
• This vaccine strain was constructed by genetically removing dermonecrotic toxin, reducing tracheal cytotoxin to background levels, and inactivating pertussis toxin.
• a single nasal administration of BPZE1 was found to provide strong protection against both pertussis disease and infection, following a challenge by a highly virulent recent clinical B. pertussis isolate.
• BPZE1 is now in clinical development and has already successfully completed two phase I studies, which have shown that the vaccine is safe in adult volunteers, able to transiently colonize the human nasal cavity and to induce antibody responses to B. pertussis antigens.
• the liquid formulation of BPZE1 used in these previous studies requires storage at -70°C to maintain bacterial viability. Because most point-of-care facilities are not equipped with ultra low freezers, this requirement is an impediment to the future commercialization of BPZE1 -based vaccines.
• Described herein are formulations and methods of making formulations of lyophilized Bordetella bacteria which are stable for at least two years when stored at temperatures between -20° and 22.5°C, and which exhibit sufficient bacterial viability and potency to be used as a live vaccine.
• lyophilized formulations Prior to the work described herein, it was unknown if such lyophilized formulations could even be made because successful lyophilization of biological molecules, and particularly live bacteria, is a challenging endeavour for several reasons.
• components used in the culture of bacteria can destabilize bacterial molecules even when freeze-dried.
• bacterial viability can be impaired in the lyophilization process by interactions at the air/liquid interface and the solution/ice interface.
• crystal (ice) formation can kill bacteria.
• dehydration can destabilize protein structure and activity.
• Bordetella-based vaccines There are also additional challenges involved in the large scale lyophilization of Bordetella-based (e.g., BPZEl-based) vaccines.
• Bordetella species produce a large number of virulence factors that enable binding to epithelial cells, but these factors also cause the bacteria to adhere to one another which exacerbates the loss of function/viability caused by clumping and biofilm formation when grown to high cell densities in a bioreactor. Clumping or biofilm formation can lead to an inhomogenous product which, in turn, leads to significant loss of product on the filter during the tangential flow filtration (TFF) step.
• TMF tangential flow filtration
• BPZE1 in particular, has a thinner cell wall than its parent wild-type strain, and has mutations (a mutated pertussis toxin gene (ptx), a deleted dermonecrotic gene (dnt), and a heterologous ampG gene which replaces the native Bordetella ampG gene which might affect the ability of the bacteria to withstand lyophilization. See U.S. Patent No. 9,180,178.
• a lyophilized vaccine including live attentuated Bordetella bacteria as an active agent.
• These methods can include the steps of : harvesting Bordetella bacteria from a culture at an ODeoo between 0.4 and 1.6; mixing the harvested Bordetella bacteria with a lyophilization buffer comprising 5-65% by weight a cryoprotectant sugar and having a temperature between 2-35°C, wherein the ratio of harvested Bordetella bacteria to lyophilization buffer is between 5:1 and 1:5 by volume; lyophilizing the mixture of the Bordetella bacteria and the lyophilization buffer; wherein the hold time between the harvesting and lyophilizing steps is less than 48 hours (e.g., less than 36 hours); and collecting the lyophilized Bordetella bacteria.
• the Bordetella bacteria can be a strain of Bordetella pertussis such as a BPZE strain, (e.g., BPZE1). In some variations of the methods, the Bordetella bacteria from cultures at an ODeoo between 0.4 and 1.0, or less than 1.0.
• the cryoprotectant sugar can be sucrose
• the lyophilization buffer can include a nutrient substrate such as glutamate.
• the lyophilizing step can include a pre-crystallization hold step wherein the mixture of the Bordetella bacteria and the lyophilization buffer is held at 0.1 to 10°C above the crystallization temperature of the mixture for 0.5-10 hours prior to further cooling.
• the methods can also feature a step of concentrating the harvested Bordetella bacteria to an ODeoo of 1.0 - 30.0 prior to the mixing step.
• lyophilized vaccine products including live attentuated Bordetella bacteria made according to the methods described above and elsewhere herein.
• the lyophilized vaccine products can have a shelf life of at least two years when stored at 22.5°C, and at least 20% of the bacteria in the product remains viable after the lyophilizing step.
• the collected lyophilized bacteria in the vaccine products can also feature the ability to prevent or reduce infection of a subject’s (e.g., a mammalian subject such as a human or mouse) respiratory tract with a pathogenic strain of Bordetella pertussis.
• Figure 1 is a series of photographs of gels showing PCR analyses of loci of a lyophilized Bordetella bacteria (the BPZE1 strain of B. pertussis) formulation compared to a liquid formulation of BPZE1.
• E. coli ampG panel A
• B. pertussis ampG panel B
• the B. pertussis dnt flanking regions panel C
• lanes 1 and 2 two lots of the liquid BPZE1 formulation
• lanes 3 and 4 two lots of the lyophilized BPZE1 formulation
• lane 5 a BPSM wild- type control
• Figure 2 is a graph showing the results of quantitative-PCR (q-PCR) amplification of the pertussis toxin (PTX) SI subunit-coding DNA. Results for the SI subunit gene of the liquid BPZE1 formulation (BPZE1 liquid), the lyophilized BPZE1 formulation (BPZE1 lyo), BPSM and BPSM-spiked lyophilized BPZE1 (Spiked) are shown.
• q-PCR quantitative-PCR
• Figure 3 is a graph showing the microbiological stability (measured in CFUs) of the liquid BPZE1 formulation at various time points over 2 years storage at -70°C. The results for the liquid BPZE1 formulation at 10 7 CFU/dose (middle line, low dose), 10 8 CFU/dose (top line, middle dose) and 10 9 CFU/dose (bottom line, high dose) are shown.
• Figure 4 is a graph showing the microbiological stability (measured in CFUs) of the lyophilized BPZE1 formulation over time.
• the lyophilized BPZE1 formulation at 10 9 CFU/dose was stored at -20°C ⁇ 10°C (top line), 5°C ⁇ 3°C (middle line) and 22.5°C ⁇ 2.5°C (bottom line) for two years, and CFUs were quantified at the indicated time points.
• the dotted and full lines represent the upper and lower limits of the specification indicated in Table 1 below.
• Figure 5 is a series of graphs showing the in vivo colonization kinetics of the lyophilized BPZE1 formulation compared to the liquid formulation in BAEB/c mice which were intranasally administered 10 5 CFU of the liquid BPZE1 formulation (black bars) or the reconstituted lyophilized BPZE1 formulation (gray bars) and sacrificed 3h (day 0), 1 or 3 days thereafter.
• Graph A shows a comparison of the CFU counts of the liquid BPZE1 formulation with those of the reconstituted lyophilized BPZE1 formulation reconstituted and administered immediately after lyophilization.
• Graph B shows a comparison of the CFU counts of the liquid BPZE1 formulation with those of the reconstituted lyophilized BPZE1 formulation reconstituted 6 months after storage at -20°C ⁇ 10°C (light gray bars), 5°C ⁇ 3°C (medium gray bars) or 22.5°C ⁇ 2.5°C (dark gray bars).
• Graph C shows a comparison of the CFU counts of the liquid BPZE1 formulation with those of the reconstituted lyophilized BPZE1 formulation reconstituted 24 months after storage at -20°C ⁇ 10°C (light gray bars), 5°C ⁇ 3°C (medium gray bars) or 22.5°C ⁇ 2.5°C (dark gray bars).
• the results are expressed as means +/- SEM. *, p ⁇ 0.05; **, p ⁇ 0.01; ***, p ⁇ 0.005; ns, not significant.
• Figure 6 is a series of graphs showing the potency of the lyophilized BPZE1 formulation compared to the liquid formulation in B ALB/c mice were intranasally administered 10 5 CFU of the liquid BPZE1 formulation (black bars) or the reconstituted lyophilized BPZE1 formulation (gray bars), or PBS as a mock control (white bars), and then challenged intranasally four weeks later with 10 6 CFU of a virulent strain of B. pertussis (BPSM). CFUs present in the lungs were quantified 3h (DO) and 7 days (D7) post challenge.
• DO 3h
• D7 7 days
• Graph A shows a comparison of the potency of the liquid BPZE1 formulation with that of the reconstituted lyophilized BPZE1 formulation reconstituted and administered immediately after lyophilization.
• Graph B shows a comparison of potency of the liquid BPZE1 formulation with that of the reconstituted lyophilized BPZE1 formulation reconstituted 6 months after storage at -20°C ⁇ 10°C (light gray bars), 5°C ⁇ 3°C (medium gray bars) or 22.5°C ⁇ 2.5°C (dark gray bars).
• Graph C shows a comparison of the potency of the liquid BPZE1 formulation with that of the reconstituted lyophilized BPZE1 formulation reconstituted 24 months after storage at -20°C ⁇ 10°C (light gray bars), 5°C ⁇ 3°C (medium gray bars) or 22.5°C ⁇ 2.5°C (dark gray bars). The results are expressed as means +/- SEM. *, p ⁇ 0.005.
• Figure 7 is a graph showing a comparison of CFU counts of three different GMP runs after lyophilization using different methods as described in the Examples section below.
• lyophilized formulations containing live attenuated Bordetella bacteria as the active agent which are stable for at least two years when stored at temperatures between -20° and 22.5 °C, and which exhibit sufficient bacterial viability and potency to be used as a live vaccine.
• Methods of making these lyophilized formulations are also described.
• the below described embodiments illustrate representative examples of these formulations and methods. Nonetheless, from the description of these embodiments, other aspects of the invention can be made and/or practiced based on the description provided below.
• Lyophilized formulations containing live attenuated Bordetella bacteria are made by harvesting Bordetella bacteria from cultures at an appropriate growth phase, optionally concentrating the harvested Bordetella bacteria from the cultures, mixing the concentrated Bordetella bacteria with a lyophilization buffer containing a cryoprotectant sugar; and then lyophilizing the mixture of the Bordetella bacteria and the lyophilization buffer.
• Bordetella bacteria used in the compositions and methods described herein may be any suitable species or strain of Bordetellae.
• Bordetella species include Bordetella pertussis, Bordetella parapertussis, and Bordetella bronchiseptica.
• Preferred Bordetella bacteria are those that have shown activity as vaccines against infections disease (e.g., pertussis) or have other beneficial prophylactic or therapeutic effects (e.g., reduction of inflammation or treatment of allergy).
• a number of live, attenuated B. pertussis strains have been made which are effective in preventing or reducing the pathology associated with pertussis, other infectious diseases, or have other beneficial prophylactic or therapeutic effects are preferred for use in the methods and compositions described herein.
• BPZE1 (described in U.S. Patent No. 9,180,178; and deposited with the Collection Nationale de Cultures de Microorganismes in Paris, France on March 9, 2006 under accession number CNCM 1-3585), and variants thereof such as BPZE1 modified to express a hybrid protein including the N-terminal fragment of filamentous haemagglutinin (FHA) and a heterologous epitope or antigenic protein or protein fragment (described in U.S. Patent No. 9,528,086), adenylate cyclase-deficient BPZE strains such as BPAL10 (described in U.S. Patent No.
• the methods of making lyophilized vaccine products including live attenuated Bordetella bacteria begin with culturing and then harvesting the Bordetella bacteria from a bioreactor. Suitable media and culture conditions are described in the Examples section below. Harvesting the cultured bacteria is performed by standard methods.
• Bordetella bacteria like BPZE1 are especially prone to aggregation/clumping in culture, to avoid the loss of viability due to this aggregation/clumping it is preferred that harvesting be performed when the culture reaches an ODeoo between 0.4 and 1.6; 0.5-1.5, 0.6-1.4, 0.7-1.3, 0.8-1.2, 0.9-1.1, 1.0, or less than 1.0 (e.g., at 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9).
• they may be optionally concentrated (e.g., to meet final CFU/dose requirements) and/or subjected to diafiltration to reduce salt or exchange buffer.
• the harvested Bordetella bacteria can be concentrated to an ODeoo of 1.0 - 30.0 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 +/- 0, 0.1, 0.2, 0.3, 0.4, or 0.5) prior to the mixing step.
• the bacteria are then mixed with a suitable lyophilization buffer.
• the lyophilization buffer is generally at a temperature between 2-35°C (e.g., between 4-30°C, between 8-25°C, between 10-20°C, or 4+/-1, 2, or 3°C).
• a suitable cryoprotectant is included in the lyophilization buffer (or added in the mixing step) at a weight ratio of 5-65% (e.g., 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, or 60 +/- 0, 1, 2, 3, 4, or 5%) of the lyophilization buffer. Based on a comparison of different cryoprotectants, cryoprotectant sugars (particularly sucrose) are preferred.
• the ratio of Bordetella bacteria to lyophilization buffer in the mixture is between 5:1 and 1:5 (e.g., 5: 1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, between 4:1 and 1:4, between 3:1 and 1:3, or between 2:1 and 1:2) by volume.
• the time between harvesting and the start of lyophilization should be less than 48 hours (e.g., less than 44, 40, 36, 32, 28, 24, 20, or 16 hours) to avoid significant losses in viability.
• the prepared mixture of bacteria and lyophilization buffer is then aliquoted into lyophilization containers (e.g., glass vials) containing between 5 X 10 6 to 1 X 10 10 (e.g., 1 X 10 6 , 5 X 10 6 , 1 X 10 7 , 5 X 10 7 , 1 X 10 8 , 5 X 10 8 , 1 X 10 9 , 2 X 10 9 , or 3 X 10 9 +/- 10, 20, 30, 40, or 50%) CFU of bacteria.
• the filled containers are then placed in a lyophilizer and the lyophilization process is started.
• Primary drying can be performed in the range of -40-0°C (e.g., at 34°C) under suitable pressure (e.g., between 50-250 microbar or 100 +/- 0, 10, 20, 30, 40, 50, 60, 70, 80, or 90 microbar). This primary drying step is typically continued until the pirani and the capacitance manometer readings converged, indicating that sublimation had ended.
• suitable pressure e.g., between 50-250 microbar or 100 +/- 0, 10, 20, 30, 40, 50, 60, 70, 80, or 90 microbar.
• the containers are then stoppered, cooled (e.g., to +4°C), unloaded, and then capped (e.g., with an aluminum cap).
• the lyophilization step preferably includes a precrystallization hold step to reduce vial-to-vial viability.
• Ice crystal formation means that the dissolved components of the lyophilization buffer increase in molarity, including the salts.
• the high salt concentration is likely to damage the outer membrane of B. pertussis, or any other bacterium, yeast, fungus or virus, so that duration of the phase in which high salt concentrations are present should be shortened if possible.
• glass vials conduct heat/cold very poorly and typically contact the lyophilizer shelf at only 3 points, during freezing, this poor conduction leads to inhomogenous cooling of vials such that the liquid in some vials will have initiated crystal formation while the liquid in others will remain liquid longer.
• the introduction of a pre-crystallization hold step prior to freezing to the Tg' is as follows. Of a given lyophilization buffer the crystallization temperature is determined by slowly cooling the buffer and noting the temperature at which the onset of crystallization occurs.
• the pre-crystallization hold step can be defined as a hold step of half an hour to several (e.g., 0.5, 0.
• Virulent B. pertussis BPSM (Menozzi et al., Infect Immun 1994, 62:769-778) was grown at 37°C on Bordet-Gengou (BG) agar containing 100 pg/ml streptomycin and supplemented with 1% glycerol and 10% defibrinated sheep blood as described (Mielcarek et al., PLoS Pathog 2006; 2: e65). After growth, the bacteria were harvested by scraping the plates and resuspending them in phosphate-buffered saline (PBS) at the desired density.
• PBS phosphate-buffered saline
• the BPZE1 vaccine strain (Mielcarek et al., PLoS Pathog 2006; 2: e65)
• Working Cell Bank (WCB) was grown in fully synthetic Thijs medium (Thalen et al., Biologicals 2006, 34:213-220) under agitation. After addition of 20% vol/vol of 86% glycerol and filling in 1.5 mL aliquots in cryo- vials, the WCB was stored at -70°C until further use, as described (Thorstensson et al., PLoS ONE 2014; 9, e83449; and Jahnmatz et al., Lancet Infect Dis 2020, 20:1290-1301).
• the WCB with a volume of 1.5 ml was inoculated in Erlenmeyer flasks containing 28.5 ml of Thijs medium (Thalen et al., Biologicals 2006, 34:213-220).
• the second pre-culture consisting of a 2-L Erlenmeyer with 0.5 L Thijs medium, was inoculated at an ODeoo of 0.1, which was in turn used as inoculum for 5 x 2-L flasks with 0.5 L Thijs medium each.
• the 5 cultures were pooled and added to a 50-L bioreactor (Sartorius, 50 L SUB) with 20 L Thijs medium so that the bioreactor started at an ODeoo of 0.1.
• the fermentation was performed at 35°C, dissolved oxygen was controlled at 20% using compressed air supplied through the sparger, and the pH was controlled at pH 7.5 using 0.2 M lactic acid. All product contact materials, such as the culture and medium flasks, containers, tubing, filters, connectors, as well as the bioreactor were single use. After reaching the target ODeoo of 1.1 - 1.4, a sample of 8 L culture was concentrated and/or diafiltered to an ODeoo as specified using hollow fiber tangential flow filtration (TFF; 750 kDA mPES membrane 1400 cm 2 , Spectrum) at a maximum transmembrane pressure of 0.3 bar.
• TMF hollow fiber tangential flow filtration
• CFU Colony Forming Unit
• BALB/c mice were purchased from Charles Rivers and kept at an animal facility under specific pathogen-free conditions.
• the various BPZE1 suspensions were diluted to 10 5 CFU per 20 pl, which were nasally administered to six-week old BALB/c mice.
• the mice were sacrificed 3h, 24h or 3 days after infection, and nasal homogenates were prepared as described (Solans et al., Mucosal Immunol 2018, 11:1753-1762) and then plated in ten-fold serial dilutions onto BG blood agar pates and incubated at 37°C for 3-5 days to quantify colonization by CFU counting.
• mice were intranasally vaccinated with 10 5 CFU of BPZE1 or received PBS intranasally as described (Debrie et al., Vaccine 2018, 36:1345-1352). Four weeks later, the mice were challenged intranasally with 10 6 CFU of virulent BPSM. Lung colonization was determined 3h and 7 days post challenge.
• PCR polymerase chain reaction
• BPZE1 preparations Approximately 10 10 CFU of the BPZE1 preparations were harvested by centrifugation and suspended in buffer Bl (Qiagen, #19060), containing RNaseA and proteinase K, and incubated at 37°C for 30 min. The bacteria were then lysed in lysis buffer for 30 min at 50°C and applied to a Qiagen genomic-tip 100/G column.
• buffer Bl Qiagen, #19060
• the DNA was precipitated with isopropanol (CarloErba), centrifuged at 5,000 x g for 15 min, washed with ice cold 70% ethanol, air dried for 10 min and resuspended in 100 pl bi-distilled water.
• the DNA concentration was measured using a NanoDrop 2000c spectrophotometer.
• One pl BPZE1, BPSM or BPSM-spiked BPZE1 DNA corresponding to 10 7 genome copies was mixed with 19 pl of LightCycler 480 SYBR Green I Master mix containing 0.5 pM of primer pairs in 96-well LightCycler 480 plates.
• the plates were sealed with specific plastic film, transferred to the LightCycler 480 and subjected to 15 min incubation at 95°C, followed by 1 to 40 cylces of denaturation for 15 seconds at 95°C, annealing for 8 seconds at 68°C and 18 seconds of elongation at 72°C.
• the data were then analysed using the LightCycler 480 software release 1.5.0.
• 10 copies of BPSM DNA were mixed with 10 7 copies of BPZE1 DNA. All primers were purchased from Eurogentec (Liege, Belgium).
• B. pertussis produces a number of virulence factors that enable binding to epithelial cells as well as to each other, and is capable of biofilm formation.
• biofilm formation leads to bacterial clumping and therefore to an inherently inhomogenous vaccine formulation.
• Clumping in the bioreactor can be avoided by increasing agitation, but too high shear forces during fermentation or ultrafiltration lead to cell damage, which translates into low survival after lyophilization.
• the manufacturing process development for the formulation consisted of developing a lyophilized formulation, including a lyophilization buffer and a matching lyophilization cycle, as well as verifying that the developed process does not interfere with the biological activity of the BPZE1 formulation. It is especially important that the formulation maintains its ability to reduce the bacterial burden in the lungs by at least two orders of magnitude in the murine protection assay.
• the target formulation attributes are shown in Table 1.
• Table 1 Target formulation attributes for the lyophilized BPZE1 formulation.
• the formulation of the lyophilization buffer was based on commonly used cryoprotectants, containing 5 to 10% sucrose or trehalose, sometimes in combination with other cryoprotectants such as hydroxy ethyl starch (HES) or sodium glutamate (MSG).
• HES hydroxy ethyl starch
• MSG sodium glutamate
• a single bacterial suspension was used to generate all formulations shown in Table 2. All formulations showed a residual moisture content (RMC) below the 2.5% target and a glass transition temperature (Tg) above the 35 °C target. Sucrose appeared superior over trehalose as cryoprotectant when used alone.
• RMC residual moisture content
• Tg glass transition temperature
• Sucrose appeared superior over trehalose as cryoprotectant when used alone.
• the addition of HES or MSG to trehalose or sucrose did not enhance survival. Repeat experiments with sucrose and trehalose showed similar results, although the absolute survival percentages varied between experiments. Therefore, 10% sucrose was chosen for further development.
• Table 3 Overview of the various runs carried out in a 50-L single use bioreactor with 20 L medium, comparing different harvest methods.
• Run 1 was filled ⁇ 50 vials, lyophilization was started with ⁇ 6 h hold time.
• Run 2 was filled ⁇ 700 vials, lyophilization was started with ⁇ 16 h hold time.
• Runs 3 to 7 were harvested, lyophilized in 2000 to 7000 vials per formulation and lyophilization was initiated after between 24 and 36 h hold time.
• Thijs medium is chemically defined and consists of components that are all generally regarded as safe. Therefore, there is no need to remove these components from the BPZE1 formulation from a quality perspective.
• Cultures that were either directly diluted with lyophilization buffer (Table 3, Runs la and 6b) or were concentrated and subsequently diluted with lyophilization buffer (Table 3, Run 7) did not show any signs of clumping directly after the harvest and just before filling.
• the culture was concentrated to an ODeoo of 5.0, followed by diluting the bacterial suspension 1:1 with cold lyophilization buffer (Table 3, Run 7).
• the lyophilized formulation was compared to the liquid formulation stored at -70°C to verify that the mutations introduced into the B. pertussis genome to generate BPZE1 were conserved, in particular the deletion of the dnt gene, the replacement of the B. pertussis ampG gene by the E. coli ampG gene and the presence of the two mutated codons in the PT SI subunit gene.
• the first two genetic modifications were verified by PCR as described in Feunou et al., Vaccine 2008, 26:5722-5727.
• the presence of the E. coli ampG gene was detected by the amplification of a 402-bp fragment corresponding to an internal fragment of the E. coli ampG gene.
• the two lyophilized BPZE1 formulations and the two liquid BPZE1 formulation controls yielded the expected 402-bp fragment, whereas this was not seen in the BPSM control sample (Fig. 1A).
• a 659-bp fragment corresponding to the B. pertussis ampG gene was amplified in the BPSM control sample, but not in any of the BPZE1 formulations (Fig. IB), indicating that both the liquid and the lyophilized BPZE1 formulations lacked B. pertussis ampG, but contained E. coli ampG.
• the deletion of the dnt gene was shown by the amplification of a 1,511 -bp fragment resulting from a PCR using primers that flank the deleted dnt gene.
• the two lyophilized BPZE1 formulations and the two liquid BPZE1 formulation controls yielded the expected 1,511 -bp fragment, whereas this was not seen in the BPSM control sample (Fig. 1C).
• a quantitative PCR method was developed, which is able to detect 1 copy of the wild type gene among 10 6 copies of the mutated gene.
• 10 7 copies BPZE1 DNA, and 10 7 copies BPZE1 DNA spiked with 10 copies of BPSM DNA were subjected to qPCR using BPSM- or BPZEl-specific oligonucleotides.
• 10 7 copies BPSM DNA served as control.
• the threshold of positivity was set at 35 qPCR cycles.
• BPSM DNA was amplified with the BPSM-specific primers, but not with the BPZEl-specific primers, while spiked BPZE1 DNA was amplified with both primer pairs (Fig. 2).
• the biological stability of the lyophilized BPZE1 formulation was evaluated in two different mouse assays: an in-vivo colonization assay and a potency assay. In each of these assays the performance of the BPZE1 formulation stored at the various temperatures was compared with that of the original liquid formulation of BPZE1, stored at -70°C.
• mice were intranasally inoculated with approximately 10 5 CFU of reconstituted lyophilized BPZE1 formulation stored at different temperatures or the liquid BPZE1 formulation control. Three hours, one day and 3 days after administration, mice were sacrificed and CFU present in the nasal homogenates were counted.
• the effect of lyophilization and the composition of the lyophilization buffer was tested by comparing the liquid formulation with the lyophilized formulation immediately after lyophilization. As shown in Figure 5A, both formulations colonized the murine nasal cavity equally well, as there was no statistically significant difference between the liquid formulation and the lyophilized formulation.
• the lyophilized formulation was then stored for 2 years at - 20°C ⁇ 10°C, 5°C ⁇ 3°C or 22.5°C ⁇ 2.5° C, and colonization kinetics were evaluated after 6 months (Fig. 5B) and 24 months (Fig. 5C) of storage and compared to those of the liquid formulation. Although after storage of 6 months, the material stored at -20°C ⁇ 10°C adhered slightly better at day 0 and colonized faster 1 day after administration than the material stored at the other temperatures, this difference was no longer detected 3 days after administration (Fig. 5B).
• mice were intranasally immunized with 10 5 CFU of the reconstituted, lyophilized BPZE1 formulation or with the BPZE1 liquid formulation control, followed by an intranasal challenge with virulent BPSM. Mice were sacrificed 3 hours or 7 days after the BPSM challenge to evaluate the bacterial load in the lungs. First, the liquid formulation was compared to the lyophilized formulation tested immediately after lyophilization.
• mice immunized with the liquid BPZE1 formulation were those immunized with the lyophilized BPZE1 formulation, and no influence of the storage temperature could be detected.
• this had no effect on the lyophilized formulation's ability to provide protection against a BPSM challenge, when stored for 6 months.
• BPZE1 was shown to provide protection against B. pertussis challenge in mice (Mielcarek et al., PLoS Pathog 2006; 2:e65; and Solans et al., Mucosal Immunol 2018, 11:1753-1762) and non-human primates (Locht, et al., J Infect Dis 2017, 216:117-124), and was found to be safe, even in severely immunocompromised animals, such as IFN-y receptor KO mice and MyD 88 -deficient mice.
• BPZE1 was also shown to be safe and immunogenic in humans in two phase 1 clinical trials.
• the RMC of the lyophilized formulation was consistently below 2.5% which is generally compatible with long term stability at 5°C or lower.
• Tg which is the temperature at which the remaining water in the lyophilized product becomes mobile again, leading to accelerated loss of viability.
• a target Tg was set at >35°C for logistical and supply chain reasons, since relatively brief exposure (from hours to several days) of the formulation to ambient, yet controlled temperatures, does not significantly affect the formulation, as confirmed by the stability of the lyophilized formulation for 2 years at +22.5 ⁇ 2.5°C.
• the manufacturing process for the lyophilized BPZE1 product did not affect the key molecular characteristics of the attenuated BPZE1 vaccine, i.e., the replacement of the B. pertussis ampG gene by that of E. coli, the deletion of the dnt gene, as assessed by specific PCRs, and the modifications of the PT SI subunit gene that result in genetically inactivated PT, as assessed by a qPCR procedure, able to detect one putative reversion among 10 6 genome equivalents.
• the lyophilized BPZE1 formulation was subjected to a real-time stability study at -20°C ⁇ 10°C, 5°C ⁇ 3°C and 22.5°C ⁇ 2.5°C.
• Ice crystal formation means that the dissolved components of the lyophilization buffer increase in molarity, including the salts.
• the high salt concentration is likely to damage the outer membrane of B. pertussis, or any other bacterium, yeast, fungus or virus, so that duration of the phase in which high salt concentrations are present should be shortened if possible.
• the vials of GMP run 3 were cooled from ambient to -5°C at a rate of l°C/minute, at which the temperature was held for 1.5 hours, followed by freezing to -50°C, at a rate of l°C/minute.
• the CFU counts of GMP run 1, 2 and 3 are compared in Figure 7, showing a 3 to almost 6-fold difference between the highest and lowest CFU count for GMP run 2 and 1 , respectively.
• the difference between the highest and lowest vial is less than 2-fold.
• Table 5 shows the same information, normalizing the highest CFU count for each batch to 100%.
• the introduction of a pre-crystallization hold step prior to freezing to the Tg' is as follows. Of a given lyophilization buffer the crystallization temperature is determined by slowly cooling the buffer and noting the temperature at which the onset of crystallization occurs.
• the pre-crystallization hold step can be defined as a hold step of half an hour to several hours, depending on the size of the lyophilizer, at 0.1 °C to several degrees above the crystallization temperature, depending on the variability of the temperature of the cooling liquid running through the lyophilizer shelves.

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