This following relates to creation of new virus strain by adapting to cell substrate recommended for vaccine production and utilizing the new strain for generating vaccines and as a diagnostic tool.
This application includes a separate sequence listing in compliance with the requirements of 37 C.F.R. §§ 1.824(a)(2)-1.824(a)(6) and 1.824(b), submitted under the file name “0032US01_Sequence_Listing_Revised”, created on Jan. 27, 2022, having a file size of 48.2 KB, the contents of which are hereby incorporated by reference.
Enterovirus 68 or Enterovirus D68 is an emerging enterovirus that causes respiratory illness with mild to severe symptoms often showing flu like symptoms and neurological diseases like acute flaccid myelitis (AFM). Enterovirus 68 is a positive-sense, single stranded RNA virus and it belongs to D species of the Enterovirus genus and Picornavirideae family. Though first isolated way back in 1962 in USA (Schieble et al., Am J Epidemiol 1967, 85:297-310), the pathogen was not reported frequently until early 21st century (Oberste et al., J Gen Virol 2004, 85:2577-2584). Thereafter, outbreaks caused by Enterovirus D68 were reported worldwide (Eshaghi et al., Front Microbiol 2017, 8: 257). In 2014, a massive outbreak occurred due to Enterovirus D68 spreading to different parts of USA which led to 1153 infections and 14 deaths (CDC. Non-Polio Enterovirus: Enterovirus D68; Midgley et al., MMWR Morb Mortal Wkly Rep 2014, 63:798-9). At the same time period upsurge of Enterovirus infections were reported in Canada (Skowronski et al., Euro Surveill 2015, 20:1-14; Edwin et al., Can Commun Dis Rep 2015, 41 Suppl 1:2-8). Subsequently, respiratory infections caused by Enterovirus D68 were reported from different countries (Dyrdak et al., Euro Surveill 2016, 21; Knoester et al., Emerg Infec Dis 2017, 23:140-143; Wang et al., SciRep 2017, 7:1242).
US20160312314A1 discloses a method for detection of enterovirus D68, through contacting nucleic acid obtained from the sample with an oligonucleotide primer, exposing the contacted sample to a DNA amplification process that provides for production of a 98 nucleotide amplification product of the enterovirus D68 VP1 gene and thereafter detecting the 98 nucleotide amplification product, wherein the presence of the amplification product indicates that the sample contained enterovirus D68.
US20160355897A1 discloses methods and compositions for detection of enterovirus D in a sample, particularly detection of enterovirus D68. The methods include contacting a sample with at least one primer (such as a forward primer and/or a reverse primer) capable of specifically amplifying an EV-D68 viral protein 1 (VP1) nucleic acid or a portion thereof and/or a detectably labeled probe capable of specifically hybridizing to an EV-D68 VP1 nucleic acid, under conditions sufficient for specific amplification of the EV-D68 VP1 nucleic acid by the at least one primer and/or under conditions sufficient for specific hybridization of the probe to the EV-D68 nucleic acid. The amplification of the EV-D68 VP1 nucleic acid and/or the hybridization of the probe to the EV-D68 VP1 nucleic acid is detected, thereby identifying presence of EV-D68 in the sample.
The conventional arts fail to teach the known Enterovirus D68 to adapt and propagate in Vero Cells, the cell substrate which is recommended for virus propagation for use in vaccine production. Furthermore, the conventional arts are limited to the methods of detection of the enterovirus D viral strains and fail to disclose any composition that may be used as a vaccine/immunogenic composition to give protection against the virus. The vaccine against this dreadful emerging virus is warranted but is not available to date. Embodiments of the present invention disclose a method of adaptation of Enterovirus D68 for propagation in Vero cells. Embodiments of the present invention also disclose an Enterovirus strain containing mutated nucleic acid sequence that translates into proteins which act as antigens suitable to be used in a vaccine composition. Embodiments of the present invention also disclose suitable vaccine compositions.
An aspect relates to a method of adapting the Enterovirus D68 strain(s) in cell substrate recommended for vaccine production e.g. Vero cells.
Another aspect of embodiments of the present invention is to provide a new Enterovirus D68 strain(s) which is/are adapted to propagate on Vero cells and can be produced in high titers on Vero cells.
Yet another aspect of embodiments of the present invention is to provide inactivated vaccine formulations against Enterovirus D68 infections comprising the virus strain.
Another aspect of embodiments of the present invention discloses the usage of recombinant proteins of Enterovirus D68 or the whole Enterovirus D68 virus adapted to Vero cells for raising antibodies against the respective recombinant proteins or the whole virus that can be utilized for diagnosis of the respective antigen.
One aspect of embodiments of the invention is to provide the process of adapting Enterovirus D68 in cell substrate recommended for vaccine production.
In some embodiments, there is provided an Enterovirus D68 adapted to propagate to high titers in Vero cells encoded by a cDNA molecule having the nucleotide sequence of SEQ ID NO: 1. In some other embodiment, there is provided a nucleotide sequence encoding the Vero cell adapted Enterovirus D68 polyprotein disclosed in SEQ ID NO: 2. In yet another embodiment, there is provided an amino acid sequence of Vero cell adapted Enterovirus D68 polyprotein disclosed in SEQ ID NO: 3.
Another aspect of embodiments of the invention is to provide the amino acid level changes (V341L, E647G, M699K, E719K, D1355N, T1406S, H2110Q) in Vero cell adapted Enterovirus D68 virus.
In some embodiment, there is provided a method of adapting Enterovirus D68 to propagate in Vero cells to high titer comprising:
In some other embodiment, there is provided a method of adapting Enterovirus D68 to propagate in Vero cells to high titer wherein Enterovirus D68 virus undergoes plaque assay comprising:
In some other embodiment, there is provided a method of inactivating Enterovirus D68 containing cDNA encoded from SEQ ID NO: 1 for immunization comprising:
In yet another aspect of embodiments of the invention there is provided formulation for inactivated Enterovirus D68 monovalent vaccine where inactivating agents for the Enterovirus D68 include chemical agents like Formalin, Beta-propiolactone, Hydrogen peroxide (H2O2) or various physical agents like UV, X-ray and gamma irradiation.
In some embodiment, there is provided an immunogenic composition comprising inactivated Enterovirus D68 virus antigen in a physiological acceptable vehicle and optionally one or more pharmaceutically acceptable excipients selected from adjuvants, stabilizers or preservatives.
Another aspect of embodiments of the invention is to provide formulation for combination vaccines comprising inactivated Enterovirus D68 and other Enteroviruses. In some embodiments, the immunogenic composition according to embodiments of the invention further comprises other Enteroviruses including EV71, polioviruses or combination thereof.
Another aspect of embodiments of the invention relates to inactivated Enterovirus D68 vaccine capable of inducing Enterovirus D68 specific humoral immune response where inactivated vaccine can be adjuvanted or unadjuvanted.
Yet another aspect of embodiments of the invention relates to Enterovirus D68 vaccine capable of eliciting significant neutralizing antibody response.
In some embodiments, there is provided an amino acid sequence belonging to Enterovirus D68 having amino acid in the polyprotein selected from L341, G647, K699, K719, N1355, S1406, Q2110 or combination thereof. In some embodiment, there is provided an immunogenic composition comprising inactivated Enterovirus D68 virus antigen in a physiological acceptable vehicle, wherein the Enterovirus D68 is having amino acid in the polyprotein selected from L341, G647, K699, K719, N1355, S1406, Q2110 or combination thereof.
In some embodiments, the immunogenic composition is stable for at least 6 months at 2-8° C. and for at least 1 month at 37° C.
Some of the embodiments will be described in detail, with references to the following Figures, wherein like designations denote like members, wherein:
Vero cells are World Health Organization (WHO) recommended most commonly used cell substrate for vaccine production in recent years. Major advantage of Vero cells is the infinite life span (continuous cell line) with proven safety and suitability for large scale production of vaccines (Barrett et al., Expert Rev Vaccines 2009, 8:607-618). Thus, Vero cell is valuable for rapid production of human vaccines. We have adapted a clinical Enterovirus D68 strain isolated from USA (US/KY/14-18953) in Vero cells after procuring from ATCC (ATCC, VR-1825).
In some embodiments, there is provided an Enterovirus D68 adapted to propagate to high titers in Vero cells encoded by a cDNA molecule having the nucleotide sequence of SEQ IDNO: 1. In some other embodiments, there is provided a nucleotide sequence encoding the Vero cell adapted Enterovirus D68 polyprotein disclosed in SEQ ID NO: 2. In yet another embodiment, there is provided an amino acid sequence of Vero cell adapted Enterovirus D68 polyprotein disclosed in SEQ ID NO: 3.
In some embodiments, there is provided a method of adapting Enterovirus D68 to propagate in Vero cells to high titer comprising:
Initially, the parent Enterovirus D68 strain US/KY/14-18953 did not propagate in Vero cells and did not show any sign of infection in the form of cytopathic effect or any cell deformities. Thus, the parent strain did not show any sign of adaptation. Later high infectious doses of virus were used for subsequent few passages. The temperature for the entire process of infection was kept around 32-34° C. and was never allowed to go above 35° C. With this strategy, the strain started to adapt in Vero cells and displayed partial cytopathic effect from 3rd passage onwards. By 5th passage complete cytopathic effect (CPE) was observed in Vero cells. Further continued passage of the Enterovirus D68 strain with gradual decrease of infectious doses for infection to determine whether or not the strain stably adapted in Vero cells. The Enterovirus D68 strain, as disclosed in embodiments of the present invention, does get adapted in Vero cells and has been used as a vaccine candidate strain to produce vaccine using Vero cells as substrate for virus propagation.
Embodiments of the present invention hereby disclose a process for adaptation of any Enterovirus D68 strain in Vero cells for making it suitable for vaccine production. In particular, embodiments of the present invention describes the process of adapting Enterovirus D68 in new cell e.g. Vero cells.
Further, embodiments of the invention also disclose the polynucleotide sequence/s of the Vero adapted Enterovirus D68 strain/s disclosed as SEQ ID NO: 1, and SEQ ID NO:2, and amino acid sequence/s of the Vero adapted Enterovirus D68 strain disclosed as SEQ ID NO:3.
Embodiments of the invention further disclose the nucleotide sequences of the individual structural proteins of EV68 disclosed as SEQ ID NO: 4, SEQ ID NO: 6, SEQ ID NO: 8, SEQ ID NO: 10 and amino acids sequences of the individual structural proteins of EV68 disclosed as SEQ ID NO: 5, SEQ ID NO: 7, SEQ ID NO: 9, and SEQ ID NO: 11, that can be used to make recombinant proteins. The nucleotide sequence of SEQ ID NO: 4 translates to give amino acid sequence of SEQ ID NO: 5, the nucleotide sequence of SEQ ID NO: 6 translates to give amino acid sequence of SEQ ID NO: 7, the nucleotide sequence of SEQ ID NO: 8 translates to give amino acid sequence of SEQ ID NO: 9, and the nucleotide sequence of SEQ ID NO: 10 translates to give amino acid sequence of SEQ ID NO: 11. The recombinant proteins can be expressed in bacterial, yeast or mammalian system after codon optimization of the nucleotide sequences suitable for each expression system and cloning into respective expression vectors. Antibody raised after immunizing the expressed recombinant proteins can be used for diagnosing whole virus or respective protein antigen.
In another embodiment, the invention discloses the process of standardization of the plaque assay of the Vero cells adapted Enterovirus D68 strain in Vero cells which may be utilized to determine the titer of the virus as Plaque forming units and especially for determining the Plaque reduction neutralization titer (PRNT) for vaccine efficacy study.
In some other embodiment, there is provided a method of adapting Enterovirus D68 to propagate in Vero cells to high titer wherein Enterovirus D68 virus undergoes plaque assay comprising:
Embodiments of the invention also disclose the preparation of antigen from the adapted virus and formulation of the same as vaccine composition to elicit antibodies against Enterovirus D68. The vaccine antigen of Vero cell adapted EV68 can be prepared by inactivation using chemical methods like formalin, beta-propiolactone (BPL), oxidizing agents like hydrogen peroxide, physical methods including but not limited to UV or X-radiation or gamma irradiation.
In some other embodiment, there is provided a method of inactivating Enterovirus D68 containing cDNA encoded from SEQ ID NO: 1 for immunization comprising:
In yet another embodiment, the inactivated vaccine antigen can be formulated either in presence or absence of adjuvants. The adjuvants include but not limited to alum (aluminium hydroxide, aluminium phosphate), emulsions like oil in a water adjuvants or water-in oil adjuvants, Toll-like receptors (TLR) ligands like monophosphoryl lipid A (MPL), flagellin either whole or truncated, adjuvant including bacterial cell components, squalene-based adjuvants like MF59 or AddaVax, montanide etc., Ribi adjuvants, CpG and non-CpG containing oligonucleotides, saponins like QS-21, Immune stimulating complexes (ISCOM), ISCOMATRIX etc, vitamins, immunomodulants including cytokines.
In some embodiments, there is provided an immunogenic composition comprising inactivated Enterovirus D68 virus antigen in a physiological acceptable vehicle and optionally one or more pharmaceutically acceptable excipients selected from adjuvants, stabilizers or preservatives.
In another embodiment, Enterovirus 68 vaccine can be formulated with other Enterovirus-based vaccine/s to make one or more combination vaccine/s where the other enterovirus includes but not limited to Enterovirus 71, Coxsackieviruses including coxsackievirus A16, coxsackievirus A6, coxsackievirus A10, rhinoviruses and polioviruses. Vaccine formulations may also include Enterovirus 68 vaccine in combination with flaviviruses, orthomyxoviruses or any other viruses that can cause respiratory diseases, encephalitis or meningitis.
In some embodiments, there is provided an amino acid sequence belonging to Enterovirus D68 having amino acid in the polyprotein selected from L341, G647, K699, K719, N1355, S1406, Q2110 or combination thereof. In some embodiment, there is provided an immunogenic composition comprising inactivated Enterovirus D68 virus antigen in a physiological acceptable vehicle, wherein the Enterovirus D68 is having amino acid in the polyprotein selected from L341, G647, K699, K719, N1355, S1406, Q2110 or combination thereof.
In some embodiments, the immunogenic composition are stable for at least 6 months at 2-8° C. and for at least 1 month at 37° C.
Enterovirus D68 strain in high infectious dose was used for infecting Vero cells. Initially, virus was allowed to adsorb in T25 cm2 flask with occasional shaking for about 60 to 120 mins followed by the addition of the DMEM as maintenance medium. About 1:3-1:10 dilution from the virus stock obtained from each passage was used to infect the next batches for initial passages. During later/subsequent passages, virus with higher dilution of the stock virus from previous passages ranging from 1:20-1:500 was used for the infection. The virus was harvested when 90% or more cytopathic effect was achieved or within 6 days of infection, whichever is earlier. The entire process of propagating Enterovirus D68 was performed at temperature not higher than 35° C. and ideally at 32-33° C. Titer of the virus in different passages were determined by TCID50 assay and/or plaque assay, and is depicted in
The entire process of selecting lower dilution of virus for infection which will not be toxic for the Vero cells during initial passages followed by higher dilution of virus for infection in later passages under controlled temperature range of 32-35° C., preferably 32-33° C. in some embodiments as described above has allowed the successful adaptation of the Enterovirus D68 virus in Vero cells.
RNA has been isolated by Trizol method according to the standard procedure from the cell free supernatant having the infectious virus after harvesting. Briefly, 750 μl of Trizol has been used for 250 μl of the virus containing supernatant. If required to obtain high amount of virus nucleic acid material, Trizol isolation method was preceded by concentrating the virus supernatant either by PEG6000 or PEG8000 (Merck, India) or ultrafiltration using 100 kDa cut off membrane (Merck, India). Isolated RNA was reverse transcribed to complementary cDNA (cDNA) using RevertAid First Strand cDNA synthesis kit (Thermo Fisher Scientific). The presence of viral RNA was confirmed using virus specific primers as depicted in
Enterovirus D68 specific primers (Calvo et al., Pediatr Infect Dis J 2016, 35:45-49):
Pan-enterovirus primers (Thao et al., J. Virol. Methods 2010, 170:134-139)
For genome wide sequencing, RNA sequencing libraries were prepared with Illumina-compatible NEBNext® Ultra™ Directional RNA Library Prep Kit (New England BioLabs, MA, USA). The sequencing library was initially quantified by Qubit fluorometer (Thermo Fisher Scientific, MA, U.S.A.) and its fragment size distribution was analyzed on Agilent TapeStation. Finally, the sequencing library was accurately quantified by quantitative PCR using Kapa Library Quantification Kit (Kapa Biosystems, Wilmington, Mass., U.S.A.). The qPCR quantified libraries were pooled in equimolar amounts to create a final multiplexed library pool for sequencing on Illumina NextSeq (150×2 chemistry).
Below Table 1 provides Amino acids difference and the corresponding nucleotide level difference between parent Enterovirus D68 virus strain US/KY/14-18953 and Vero cells adapted virus strain US/KY/14-18953-Vero:
No comprehensive literature is available in support of Enterovirus D68 plaque assay. Embodiments of the present invention disclose standardized plaque assay procedure for Enterovirus D68. About 3 to 4 million of Vero cells were plated per 12 well plate or 6 well plate (Greiner bio-one) to reach the confluency suitable for plaque assay. Different dilutions of virus were adsorbed in different wells in duplicate, triplicate or quadruplicate for 1-2 hours. 0.8% carboxymethylcellulose (CMC) (Merck, India) semisolid overlay was added subsequently. Carboxymethylcellulose of 0.6-0.5% concentration was also used alternatively as overlay media. Alternatively, Avicel RC 591(FMC Corporation, USA) of 0.8-1.8% concentration was used as overlay. For convenience, Avicel RC 591 will be termed as Avicel hereafter.
The cells were fixed with 10% formaldehyde for 1 hour after 4 to 6 day post infection when CMC was used as overlay or after 2 to 4 days post infection when Avicel was used as overlay. After fixation, the fixative solution was removed and the cells were washed with phosphate buffer saline (PBS). After washing, freshly made crystal violet solution was added dropwise to the fixed cells and was allowed to be stained for 30 minutes to 1 hour at room temperature. Plaques got visible by 5th day of infections when CMC was used as overlay or within 48 hours when Avicel was used. Results are depicted in
Vero cell adapted Enterovirus D68 antigen was checked for the expression of Enterovirus D68 VP1, VP2 proteins by Western Blot using Enterovirus D68-VP1 and VP2 specific antibodies as shown in
The propagated and harvested EVD68 virus encoding cDNAs as in SEQ ID NO: 1 was sterile filtered; the host nucleic acid was removed using nuclease treatment and concentrated by tangential flow filtration using 100 kDa filter. Subsequently, the concentrated virus was inactivated using 1/2000- 1/4000 formalin for up to 3 weeks at temperature varying from 25-37° C. or with BPL at 4-25° C. for up to 120 hours. Formalin was neutralized by using thiosulphate. Alternatively, the virus was inactivated with 0.005% to 3% hydrogen peroxide at 25±5° C. for up to 6 hours. The residual hydrogen peroxide was hydrolyzed by the addition of 10 U/ml of catalase to stop the reaction. At the end of the inactivation experiments, the inactivation was confirmed with the absence of cytopathic effect by serially passage of the inactivated virus up to thrice in Vero cells. The inactivated virus antigen is tested and confirmed for invitro antigenicity using Enterovirus 68 antigen specific VP1 antibodies. The inactivated virus was subsequently purified using gel filtration using Sepharose CL-4B followed by anion exchange chromatography using DEAE resins or by Capto Core 700 resins (GE healthcare Life Sciences). The purification was also performed by double steps/two rounds of size exclusion chromatography. The inactivated virus can be also purified using cellufine sulphate followed by anion exchange chromatography if required. The purification was also performed by mixed mode resins -CHT Type II (Biorad) alone or in combination with the resins mentioned earlier.
Alternatively, the inactivation as described above was done after purification of the virus. The buffer used for the inactivated vaccine is 10-30 mM Phosphate buffer. Alternatively, Tris buffer, Histidine buffer, Sucrose phosphate Glutamate or any pharmaceutically accepted buffer was used for the formulations.
Suitable excipients that were used for the inactivated vaccine includes but not limited to stabilizers selected from sugar alcohols like glycerol, sorbitol, mannitol (Up to 20%). The formulation also includes stabilizer like Sucrose, and/or Trehalose and/or Polysorbate 40 or Polysorbate 80. The vaccine formulation includes amino acids selected from glycine, Glutamic acids, arginine or arginine hydrochloride (Up to 2%). The vaccine formulation also includes human or animal serum albumin.
The vaccine formulation includes preservatives selected from Thiomersal and 2-phenoxyethanol. For mercury free vaccine formulation, 2-phenoxyethanol (2.5-20 mg/ml) will be used. In another embodiment, formulation is devoid of any preservatives.
Inactivated antigen is formulated with or without Alum adjuvant of concentration ranging from 100 μg to 1 mg; more precisely with 200-500 μg of alum for immunization. Inactivated Enterovirus 68 vaccine can be formulated using other adjuvants such as emulsions like oil in a water adjuvants or water-in oil adjuvants, Toll-like receptors (TLR) ligands like monophosphoryl lipid A (MPL), flagellin either whole or truncated, adjuvant including bacterial cell components, squalene-based adjuvants like MF59 or AddaVax, montanide etc., Ribi adjuvants, CpG and non-CpG containing oligonucleotides, saponins like QS-21, Immune stimulating complexes (ISCOM), ISCOMATRIX etc, vitamins, immunomodulants including cytokines.
EVD68, EV71 and polio virus causes neurological symptoms and is often associated with Accute flaccid myelitis—weakness associated with spinal cord resulting in weakness in muscles and reflexes in the body. Thus, combination vaccines directed against EVD68, EV71 and polio viruses will reduce the neurological complication associated with these viruses. In one embodiment, formalin inactivated EVD68 antigen (Up to 5 micrograms) was formulated with formalin inactivated EV71 inactivated antigen (Up to 5 micrograms) in phosphate buffer (10-30 mM) (1:1 ratio of antigens). The other components of the formulation include adjuvants (including but not limited to alum up to 0.9 mg/ml or MPLA or Alum and MPLA combined), sugar and/or sugar alcohols. The formulation may include amino acids like Glycine, and/or Glutamate and/or Arginine (Up to 2%). The formulation may or may not include preservatives such as Thiomersal or 2-phenoxyethanol.
In another embodiment, formalin inactivated EVD68 antigen (up to 5 microgram of antigen) was formulated with formalin inactivated sabin type 1 polio (up to 40D antigen units) and sabin type 3 polio vaccine (up to 32 D antigen units). The combination vaccine may or may not include formalin inactivated EV71 antigen (up to 5 microgram of antigen).
EV71 virus inactivation and type 1 and type 3 polio virus inactivation was done with formalin at 36° C.±1° C. for up to 14 days. In another embodiment, inactivated EVD68, EV71 and type 1 and 3 polioviruses were adsorbed separately in alum for 2-3 hours in room temperature or for up to 6 hours or for 16 hours in 4° C. under stirring condition. Subsequently, the adsorbed antigens were mixed together under stirring conditions.
Alternatively, EVD68 antigen or EV71 or polio antigens were adsorbed first in alum followed by the other antigens.
Formulation was also made without adjuvant by mixing the antigens.
The tables provided below is just for illustration. The scope of possible formulations with monovalent inactivated EVD68 vaccine and combination vaccines having inactivated EVD68, inactivated EV71, inactivated sabin type 1 polio and inactivated sabin type 3 polio vaccine is not limited to the formulations mentioned in the tables. The pH of the vaccine formulations was kept in the range of 6.5 to 7.5.
Stability of EVD68 antigen was tested by exposing the inactivated EVD68 antigen at 2-8° C. for up to 6 months. Alternatively, accelerated stability study was performed at 37° C. for 1 month. The inactivated antigen was found to maintain >75% stability for one month at 37° C. without any stabilizers. In presence of 10% sucrose or 10% sucrose and 10% sorbitol combination, the stability is ≥90% at 37° C. for 1 month. Stability at 2-8° C. is more than 85% when stored for 6 months without stabilizer and more than 95% with 10% sucrose or 10% sucrose and 10% sorbitol combination (
The vaccine containing inactivated antigen was used to immunize mice of 6-8 weeks thrice with three weeks apart. The serum was collected before and after each immunization. ELISA was performed after coating with Enterovirus D68 specific antigen followed by blocking in 1% BSA and subsequent treatment of the ELISA plate with immunized mice serum and anti-mouse secondary antibody.
It was found that Formalin inactivated antigen induces very high Enterovirus D68 specific antibody titer (up to 200,000) and is depicted in
Further, Enterovirus D68 specific IgG1/IG2a ratio was determined from serum collected from mice two weeks after the third immunization to detect whether the pattern of immune response is Th1 or Th2 type by ELISA (
For neutralization titer detection, serum from EVD68 inactivated antigens vaccine (formulated with or without adjuvants) immunized mice was diluted serially and incubated with Enterovirus D68 virus for 2 hours in 1:1 ratio. The serum-virus mixture was added to the Vero cells and incubated for 2 hours. Subsequently, the cells were overlayered with 1.2% Avicel in DMEM media. The cells were fixed in 10% formalin four days post infection and stained with 0.8% crystal violet solution for plaque visualization. PRNT50 was calculated as the highest sera dilution showing 50% or more reduction in the number of plaques.
Alternatively, microneutralization assay was performed in 96 well format. In microneutralization method, 2.5 million cells per 96 well plate was plated. The serum from EVD68 inactivated antigens vaccine (formulated with or without adjuvants) immunized mice was diluted serially and incubated with Enterovirus D68 virus for 2 hours in 1:1 ratio. Subsequently, serum-virus mixture was added to the Vero cells and waited for up to 4 days to observe inhibition of cytopathic effect of Vero cells in the wells having serum-virus mixture. Neutralization titer was considered as the last dilution of the serum that inhibit 50% of cytopathic effect in compare to the wells having controls virus or negative control serum-virus mixture.
Both Formalin and BPL inactivated Enterovirus D68 antigen induces significant neutralization antibody titer in Balb/c mice.
Although the invention has been illustrated and described in greater detail with reference to the preferred exemplary embodiments, the invention is not limited to the examples disclosed, and further variations can be inferred by a person skilled in the art, without departing from the scope of protection of the invention.
For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.
Number | Date | Country | Kind |
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201841049814 | Dec 2018 | IN | national |
This application claims priority to PCT Application No. PCT/IN2019/050960, having a filing date of Dec. 27, 2019, which is based on IN 201841049814, having a filing date of Dec. 29, 2018, the entire contents both of which are hereby incorporated by reference.
Filing Document | Filing Date | Country | Kind |
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PCT/IN2019/050960 | 12/27/2019 | WO | 00 |