Isfahan University of Medical Sciences Journal of Isfahan Medical School 1027-7595 41 737 2023 11 22 Investigating the Effect of Monophosphoryl Lipid A as a Co-adjuvant on Humoral Immune Response against Staphylococcus Aureus Infection in a Mouse Model Investigating the Effect of Monophosphoryl Lipid A as a Co-adjuvant on Humoral Immune Response against Staphylococcus Aureus Infection in a Mouse Model 835 845 31088 10.48305/jims.v41.i737.0835 FA Mehdi Mirshekar PhD Student, Department of Toxicology and Pharmacology, School of Pharmacy, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran 0000-0002-9805-6269 Setareh Haghighat Associate Professor, Department of Microbiology, School of Advanced Science and Technology, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran 0000-0002-6605-5245 Seyedeh Zahra Mousavi Professor, Department of Toxicology and Pharmacology, School of Pharmacy, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran 0000-0001-6524-491X Amir Hossein Abdolghaffari Assistant Professor, Department of Toxicology and Pharmacology, School of Pharmacy, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran 0000-0001-9961-9097 Mohammad Hossein Yazdi Associate Professor, Biotechnology Research Center, Tehran University of Medical Sciences, Tehran, Iran 0000-0001-8567-8555 Journal Article 2023 07 13 Background: Staphylococcus aureus is one of the leading causes of nosocomial infections, therefore, it is necessary to develop a suitable vaccine candidate to prevent infections caused by this bacterium. Autolysin protein as a virulence factor plays an important role in bacterial division. Monophosphoryl lipid A (MPLA) as a Toll-like receptor 4 agonist is currently used as an adjuvant. In this study, autolysin protein along with MPLA was investigated as a vaccine candidate. Methods: Recombinant autolysin was expressed with IPTG and purified by Ni-NTA affinity chromatography. To increase the immunogenicity of vaccine candidates, Monophosphoryl lipid A (biologic and synthetic) was formulated in combination with Alum in four groups of Balb/c mice. Animals were injected subcutaneously three times at intervals of two weeks. Total IgG and IgG1, IgG2a isotype antibodies were measured in sera by indirect ELISA technique. Then, experimental mice were challenged with a sub-lethal dose of Staphylococcus Strain (5×108 CFU) and following that, the number of bacteria from internal organs was assessed. Also, the survival rate was monitored daily for 30 days. Findings: Total IgG, IgG1, and IgG2a isotype antibody levels were significantly improved in vaccinated groups in comparison to the control group. Bacterial burden in the internal organ (Liver, spleen, and kidney), and animal mortality of the vaccinated group especially r-Autolysin+Alum+MPLA Synthetic and r-Autolysin+Alum+MPLA biologic were decreased in comparison to the control group. Conclusion: We concluded that synthetic MPLA is a reliable candidate for immune response improvement against Staphylococcal infection. Background: Staphylococcus aureus is one of the leading causes of nosocomial infections, therefore, it is necessary to develop a suitable vaccine candidate to prevent infections caused by this bacterium. Autolysin protein as a virulence factor plays an important role in bacterial division. Monophosphoryl lipid A (MPLA) as a Toll-like receptor 4 agonist is currently used as an adjuvant. In this study, autolysin protein along with MPLA was investigated as a vaccine candidate. Methods: Recombinant autolysin was expressed with IPTG and purified by Ni-NTA affinity chromatography. To increase the immunogenicity of vaccine candidates, Monophosphoryl lipid A (biologic and synthetic) was formulated in combination with Alum in four groups of Balb/c mice. Animals were injected subcutaneously three times at intervals of two weeks. Total IgG and IgG1, IgG2a isotype antibodies were measured in sera by indirect ELISA technique. Then, experimental mice were challenged with a sub-lethal dose of Staphylococcus Strain (5×108 CFU) and following that, the number of bacteria from internal organs was assessed. Also, the survival rate was monitored daily for 30 days. Findings: Total IgG, IgG1, and IgG2a isotype antibody levels were significantly improved in vaccinated groups in comparison to the control group. Bacterial burden in the internal organ (Liver, spleen, and kidney), and animal mortality of the vaccinated group especially r-Autolysin+Alum+MPLA Synthetic and r-Autolysin+Alum+MPLA biologic were decreased in comparison to the control group. Conclusion: We concluded that synthetic MPLA is a reliable candidate for immune response improvement against Staphylococcal infection.

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