FDA-approved immunosuppressants targeting staphylococcal superantigens: mechanisms and insights

Cellular immune response of Staphylococcus aureus enterotoxin B in Balb/c mice through intranasal infection

Background and Aim:

Staphylococcus aureus produces various superantigen exotoxins, including staphylococcal enterotoxin B (SEB). It causes fatal anaphylactic reactions and toxic shock. This study aimed to evaluate the reaction of leukocytes and histopathological changes in the respiratory organs of Balb/c mice after intranasal infection with enterotoxigenic S. aureus (SEB).

Materials and Methods:

The presence of the seb gene in S. aureus was established in this study using polymerase chain reaction-specific primer. Two groups of 8-week-old male Balb-c mice consist of six mice in each group. The treated group was infected with 50 μL and 100 μL of SEB intranasal on days 1 and 14, respectively. NaCl was administered in the second group and was considered as a control group. Blood samples were collected through the retro-orbital plexus on days 1, 4, 7, 14, and 22 after infections. Total cell counts were analyzed with an independent sample t-test and compared using the statistical package for the social sciences (SPSS) version 16.0 (IBM Corp., NY, USA). The infected tissues of the respiratory organ were observed descriptively and compared to the control group.

Results:

The seb gene with a molecular size of 478 bp, indicating the SEB strain, is present in S. aureus used in this study. Intranasal administration of SEB showed increased leukocytes, lymphocytes, monocytes, and eosinophils on day 22 post-infection. Significant leukocytosis was seen on days 6 and 14; lymphocytosis on days 1, 4, 6, and 16; and eosinophilia on days 6, 14, and 22 compared with the control group (p > 0.05). In contrast, the neutrophil decreased after an increase of immature band cells compared to the control group, indicating a severe acute infection with SEB. The lungs and trachea of the test group had an inflammatory cell accumulation in the respiratory organ.

Conclusion:

Intranasal route infection of S. aureus containing seb gene significantly induced the cellular immune response and caused pathological changes in the respiratory tissues of the Balb/c mice model. The hematological changes were aligned with marked pathological changes in the respiratory tract. Balb/c mice could be an excellent experimental model to study toxic and anaphylactic shock against SEB to define the future therapeutic agents.

Role of Superantigens In Various Childhood Inflamatory Diseases

----:: Super antigens (Sags) are some part of virus or bacteria proteins which stimulate T cells and antigen-presenting cells leading to systemic immune repose and inflammation. ---SAgs might have possible role in in various inflammatory childhood diseases (eg Kawasaki disease, atopic dermatitis, and chronic rhinosinusitis). ----Worldwide studies had done to determine the role of staphylococcal SAgs (TSST-1 ) in various inflammatory diseases. The SAgs (TSST-1) not only induce sepsis and septic shock (even in negative blood culture for S.aureus) ,but also might have significant role in various childhood inflammatory diseases ( eg KD, OMS, Polyp, dermatitis, psoriasis ) . In proven SAgs induced inflammatory diseases, inhibition the cell-destructive process by SAgs suppressants might be helpful. ----In toxic shock or sepsis like presentation even in cases with negative blood cultures immediate use pf anti staphylococcal drugs is required. ---Occasionaly, clinical presentation of some human viruses (eg coronavirus and adenovirus) mimic KD. ----- In addition ,coinfection with adenovirus, coronavirus, and para-influenza virus type 3 were observed with KD. -- Bacterial Sags induced increasement of acute-phase reactants and number of white blood cell, and neutrophil counts In developed KD. ----Multisystem inflammatory syndrome in children (MISC) and KS observed during the recent COVID-19 pandemia. This study summarized the relation between viral and bacterial SAgs and childhood inflammatory diseases.

Induction of CD4+ regulatory T cells by stimulation with Staphylococcal Enterotoxin C2 through different signaling pathways

As a member of superantigens, Staphylococcal Enterotoxin C2 (SEC2) can potently activate T cells expressing specific Vβ repertoires and has been applied in clinic for tumor immunotherapy in China for more than 20 years. However, excessive activation of T cells by over-stimulation with superantigen are always followed by eliciting regulatory T cells (Tregs) induction and functional immunosuppression, which brings uncertainties to SEC2 application in tumor immunotherapy. In this study, we found that SEC2 could induce CD4+CD25+Foxp3+ Tregs from the murine splenocytes in dose and time related manners. The induced Tregs with high expression of GITR and CTLA-4 and low expression of CD127 were TCR Vβ8.2-specific and have character of IL-10 production in a SEC2 dose-depended manner. Importantly, SEC2-induced CD4+ Tregs showed the potent capacity of suppressing proliferation of intact murine splenocytes response to SEC2. Furthermore, by using specific inhibitors or neutralizing antibody, we proved that the signaling pathways of TCR-NFAT/AP-1, IL-2-STAT5, and TGF-β-Smad3 play crucial roles in Tregs induction by SEC2. These findings will help us better understand the balance of immune stimulation and immunosuppression mediated by SEC2 and provide valuable guidance for SEC2 application in antitumor immunology.

Searching the Staphylococcal Toxic Shock Syndrome Toxin -1 in Septic Children with negative Cultures: A Comparative Study in Tehran, Iran

BACKGROUND

Bacteria induced sepsis is common in infants and children. Staphylococcus aureus produces numerous exotoxins, like staphylococcal Toxic shock syndrome toxin (TSST- 1), which stimulate the immune system by T cell activation and inflammation in various organs. Recent studies suggest that staphylococcal toxins, generally named super antigens (SAgs), may also have a significant role in the pathogenesis of some pediatric disorders especially in the clinical presentation of sepsis and septic shock. This study was carried out in order to compare staphylococcal TSST- 1 (SAgs) in children with sepsis symptoms (and septic shock) with negative blood culture versus a control group.

MATERIALS AND METHODS

This cross-sectional study was conducted during 2 years (2014 -2016) in two referral hospitals (Rasoul Akram and Bahrami hospitals) in Tehran, Iran. We selected 44 children) mean age of 4 years) who were admitted in pediatrics and PICUs wards with sepsis symptoms- /+septic shock. Forty-five children (mean age of 3.9 years) were selected as a control group. All cases with blood samples were examined for TSST-1 (SAgs) by polymerase chain reaction (PCR) method in both case and control groups and results were compared. Data were analyzed by SPSS-16software. Chi-square or Fisher test was used to compare the variables. P-value < 0.05 was considered as a valuable tool.

RESULTS

Positive blood cultures with other bacteria, Streptococcus pneumonia, Haemophilus influenzae, Pseudomonas aeruginosa, Escherichia coli, were detected in 5 cases with negative TSST-1 in blood samples. S.aureus isolated from blood culture was detected in 2 cases with positive TSST- 1.Positive TSST-1 (SAgs) was detected in 6 cases (14%) with negative blood culture for S.aureus; it was significantly higher in cases (14% vs. 2%; P value = 0.05).

CONCLUSION

This study indicates the probable role of TSST-1(SAgs) in the progression of sepsis (and septic shock) in toxic children with negative blood culture for S.aureus. Anti-staphylococcal treatment is immediately required, especially in toxic children with related clinical presentations, even in cases with negative blood cultures. Indeed, the clinical use against SAgs suppressants of downstream cell-destructive events might be helpful.

Influence of Phosphatidylinositol-3-Kinase/Protein Kinase B-Mammalian Target of Rapamycin Signaling Pathway on the Neuropathic Pain Complicated by Nucleoside Reverse Transcriptase Inhibitors for the Treatment of HIV Infection

Background:

Nucleoside reverse transcriptase inhibitors (NRTIs) are the earliest and most commonly used anti-human immunodeficiency virus drugs and play an important role in high active antiretroviral therapy. However, NRTI drug therapy can cause peripheral neuropathic pain. In this study, we aimed to investigate the mechanisms of rapamycin on the pain sensitization of model mice by in vivo experiments to explore the effect of mammalian target of rapamycin (mTOR) in the pathogenesis of neuropathic pain caused by NRTIs.

Methods:

Male Kun Ming (KM) mice weighing 20–22 g were divided into control, 2 mg/kg rapamycin, 12 mg/kg stavudine, and CMC-Na groups. Drugs were orally administered to mice for 42 consecutive days. The von Frey filament detection and thermal pain tests were conducted on day 7, 14, 21, 28, 35, and 42 after drug administration. After the last behavioral tests, immunohistochemistry and western blotting assay were used for the measurement of mTOR and other biomarkers. Multivariate analysis of variance was used.

Results:

The beneficial effects of rapamycin on neuropathic pain were attributed to a reduction in mammalian target of rapamycin sensitive complex 1 (mTORC1)-positive cells (70.80 ± 2.41 vs. 112.30 ± 5.66, F = 34.36, P < 0.01) and mTORC1 activity in the mouse spinal cord. Mechanistic studies revealed that Protein Kinase B (Akt)/mTORsignaling pathway blockade with rapamycin prevented the phosphorylation of mTORC1 in stavudine-intoxicated mice (0.72 ± 0.04 vs. 0.86 ± 0.03, F = 4.24, P = 0.045), as well as decreased the expression of phospho-p70S6K (0.47 ± 0.01 vs. 0.68 ± 0.03, F = 6.01, P = 0.022) and phospho-4EBP1 (0.90 ± 0.04 vs. 0.94 ± 0.06, F = 0.28, P = 0.646).

Conclusions:

Taken together, these results suggest that stavudine elevates the expression and activity of mTORC1 in the spinal cord through activating the Akt/mTOR signaling pathway. The data also provide evidence that rapamycin might be useful for the treatment of peripheral neuropathic pain.