Delivery of MERS antigen encapsulated in α-GalCer-bearing liposomes elicits stronger antigen-specific immune responses.

Alpha-Galactosylceramide (α-GalCer) effectively activates the natural killer T (NKT) cells to secrete remarkable amounts of Th1 and Th2 cytokines and therefore, acts as a potential immunoadjuvant in vaccine formulation. In the present study, we prepared α-GalCer-bearing or α-GalCer-free liposomes and loaded them with Middle East Respiratory Syndrome Coronavirus papain-like protease (α-GalCer-Lip-MERS-CoV PLpro or Lip-MERS-CoV PLpro). These formulations were injected in mice to investigate the antigen-specific humoral and cell-mediated immune responses. The immunisation with α-GalCer-Lip-MERS-CoV PLpro or Lip-MERS-CoV PLpro did not induce any notable toxicity in immunised mice. The results demonstrated that mice immunised with α-GalCer-Lip-MERS-CoV PLpro showed greater antigen-specific antibody titre, switching of IgG isotyping to IgG2a subclass and higher lymphocyte proliferation. Moreover, the splenocytes from α-GalCer-Lip-MERS-CoV PLpro immunised mice secreted greater levels of IFN-γ, IL-4, IL-2 and IL-12. Interestingly, a booster dose induced stronger memory immune responses in mice previously immunised with α-GalCer-Lip-MERS-CoV PLpro. In summary, α-GalCer-Lip-MERS-CoV PLpro may prove to be a promising vaccine formulation to protect the individuals against MERS-CoV infection.

Encapsulation of MERS antigen into α-GalCer-bearing-liposomes elicits stronger effector and memory immune responses in immunocompetent and leukopenic mice.

Objectives: Here, we prepared a liposome-based vaccine formulation containing Middle East Respiratory Syndrome Coronavirus papain-like protease (MERS-CoV-PLpro). Methods: A persistent leukopenic condition was induced in mice by injecting cyclophosphamide (CYP) three days before each dose of immunization. Mice were immunized on days 0, 14 and 21 with α-GalCer-bearing MERS-CoV PLpro-encapsulated DPPC-liposomes (α-GalCer-MERS-PLpro-liposomes or MERS-CoV PLpo-encapsulated DPPC-liposomes (MERS-PLpro-liposomes), whereas the antigen emulsified in Alum (MERS-PLpro-Alum) was taken as a control. On day 26, the blood was taken from the immunized mice to analyze IgG titer, whereas the splenocytes were used to analyze the lymphocyte proliferation and the level of cytokines. In order to assess the memory immune response, mice were given a booster dose after 150 days of the last immunization. Results: The higher levels of MERS-CoV-PLpro-specific antibody titer, IgG2a and lymphocyte proliferation were noticed in mice immunized with α-GalCer-MERS-PLpro-liposomes. Besides, the splenocytes from mice immunized with α-GalCer-MERS-PLpro-liposomes produced larger amounts of IFN-γ as compared to the splenocytes from MERS-PLpro-liposomes or MERS- PLpro-Alum immunized mice. Importantly, an efficient antigen-specific memory immune response was observed in α-GalCer-MERS-PLpro-liposomes immunized mice. Conclusions: These findings suggest that α-GalCer-MERS-PLpro-liposomes may substantiate to be a successful vaccine formulation against MERS-CoV infection, particularly in immunocompromised individuals.

Potential Implications of Black Seed and its Principal Constituent Thymoquinone in the Treatment of COVID-19 Patients.

BACKGROUND: Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the causative agent of the current pandemic of Coronavirus Disease-2019 (COVID-19). The progression of COVID-19 is related to an excessive host inflammatory immune response to SARS-CoV-2 infection, which is considered a major cause of disease severity and death. Dysregulated immune response produces huge amounts of pro-inflammatory cytokines and chemokines called "cytokine storm". Moreover, the activation of microthrombi formation plays an important role in multiple organ failure. METHODS: Keeping into consideration the potent anti-inflammatory activity of black seed and its major constituent Thymoquinone (TQ), we hypothesize their potential implication in the treatment of COVID-19 patients. A literature search was performed in PubMed, ScienceDirect, Google Scholar and Scopus electronic databases using the terms, including black seed, N. sativa, thymoquinone, SARSCoV- 2, COVID-19 and inflammatory immune response. RESULTS: Various studies confirmed that Black seed and TQ reduced the thrombus formation, the expression of tissue factor and the immune activation. Furthermore, TQ demonstrated the broad-spectrum antimicrobial activity that may be effective in controlling the secondary infections in COVID-19 patients. CONCLUSION: Keeping into consideration the multi-targeting nature of the black seed and TQ, they may be used as a potential therapeutic formulation or as an adjunct therapy in the treatment of COVID-19 patients.