Different formulations of inactivated COVID-19 vaccine candidates in the human compatible adjuvants: Preclinical studies in mice
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Akbar Khorasani ,1 Melika Haghighi ,2 pegah karimi,3 Mehdi Mahdavi ,4,*
1. 1. Department of FMD vaccine production, Razi Vaccine & Serum Research Institute, Agricultural Research, Education & Extension Organization (AREEO) Karaj, Iran
2. Recombinant Vaccine Research Center, Tehran University of Medical Sciences, Tehran, Iran
3. Recombinant Vaccine Research Center, Tehran University of Medical Sciences, Tehran, Iran
4. Recombinant Vaccine Research Center, Tehran University of Medical Sciences, Tehran, Iran
- Introduction: The Covid-19 pandemic started in December 19 in Wuhan (China). The World Health Organization named the epidemic a Public Health Emergency of Global Importance in January 2020 and a pandemic in March 2020. Numerous vaccines are currently being developed using various methods such as inactivated vaccine, recombinant protein vaccine, live attenuated vaccine, adenovirus vector vaccine, DNA vaccine and mRNA vaccine. Adjuvants are an important component of inactivated vaccines and elicit specific immune responses that have higher resistance and durability. Here, we first isolated and inactivated the human COVID-19 virus and then different formulations with Alum, Montanide 51VG and Montanide 720VG adjuvants were developed and then examined different aspects of the immune response.
- Methods: A SARS-CoV-2 strain was isolated and cultivated in Vero cell line for propagation, and the virus was inactivated with formalin. Inactivated COVID-19 virus was formulated in Montanide ISA 720VG, Montanide ISA51VG and or Alum hydroxide adjuvants. Inactivated COVID-19 virus in PBS buffer was admixed with Montanide ISA 720VG (30/70) and Montanide ISA 51VG (50/50) by vigorously shaking and homogenized using homogenizer. For Alum-based vaccine, 4µg of inactivated COVID-19 virus in PBS buffer was mixed with 200µg of Alum hydroxide adjuvant and shaked at 100 RPM for 60 minutes and allowed that the viral particles adsorb on the surface of Alum gel. Six-to eight-week-old male BALB/c mice (N=40) were purchased from Royan Institute of Iran (Tehran, Iran) and grouped as below;
Group 1: inactivated COVID-19-Alum vaccine.
Group 2: inactivated COVID-19-Montanide ISA-51VG vaccine.
Group 3: inactivated COVID-19-Montanide ISA-720VG vaccine.
Group 4: Mice were immunized with PBS as control group.
Experimental mice were immunized subcutaneously with 4µg of vaccine, two times on days 0 and 14 and two weeks after the final immunization, immunologic parameters were assessed.
- Results: Immunization with COVID-19-Montanide ISA51VG shows a significant increase of IFN-γ cytokine versus COVID-19-Alum, COVID-19-Montanide ISA720VG and control groups (P< 0.0033). The results of IL-4 response show that injection of COVID-Alum showed a significant increase versus COVID-19-Montanide ISA 51 VG, COVID-19-Montanide ISA 720 VG and control groups (P<0.0206).
The results of CTL activity based on Gr-B secretion showed that immunization with COVID-19- Montanide ISA51 VG and with COVID-19-Montanide ISA720 VG resulted to a significant increase versus COVID-19-Alum and control groups (P<0.0075).
Results of specific IgG titer in the experimental groups showed that immunization with COVID-19- Montanide ISA51 VG and with COVID-19-Montanide ISA720 VG resulted to the highest IgG titer and a significant increase versus COVID-19-Alum and control groups (P<0.0143).
Results of specific IgG-1and IgG2a level showed that all three formulations of COVID-19-Alum, COVID-19-Montanide ISA51VG and COVID-19-Montanide ISA720VG vaccine showed a significant increase versus the control group (P<0.0001).
- Conclusion: According to the immune responses triggered by different formulations of COVID-19 in the human compatible adjuvants, it seems that the type of vaccine formulation is a critical parameter that effect on the cellular and humoral immune responses and vaccine potency. Here, results showed that human compatible oil-based adjuvants were more potent than Alum adjuvant in the induction of cellular and humoral immune responses versus COVID-19 virus.
- Keywords: Inactivated COVID-19, Alum, Montanide 51VG and Montanide 720VG, Adjuvants, Vaccine formulation.
