T. brucei infections abrogate diverse plasma cell-mediated effector B cell responses, independently of their specificity, affinity and host genetic background

COVID-19 and Diarylamidines: The Parasitic Connection

As emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants (Omicron) continue to outpace and negate combinatorial vaccines and monoclonal antibody therapies targeting the spike protein (S) receptor binding domain (RBD), the appetite for developing similar COVID-19 treatments has significantly diminished, with the attention of the scientific community switching to long COVID treatments. However, treatments that reduce the risk of "post-COVID-19 syndrome" and associated sequelae remain in their infancy, particularly as no established criteria for diagnosis currently exist. Thus, alternative therapies that reduce infection and prevent the broad range of symptoms associated with 'post-COVID-19 syndrome' require investigation. This review begins with an overview of the parasitic-diarylamidine connection, followed by the renin-angiotensin system (RAS) and associated angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSSR2) involved in SARS-CoV-2 infection. Subsequently, the ability of diarylamidines to inhibit S-protein binding and various membrane serine proteases associated with SARS-CoV-2 and parasitic infections are discussed. Finally, the roles of diarylamidines (primarily DIZE) in vaccine efficacy, epigenetics, and the potential amelioration of long COVID sequelae are highlighted.

The Role of MIF and IL-10 as Molecular Yin-Yang in the Modulation of the Host Immune Microenvironment During Infections: African Trypanosome Infections as a Paradigm

African trypanosomes are extracellular flagellated unicellular protozoan parasites transmitted by tsetse flies and causing Sleeping Sickness disease in humans and Nagana disease in cattle and other livestock. These diseases are usually characterized by the development of a fatal chronic inflammatory disease if left untreated. During African trypanosome infection and many other infectious diseases, the immune response is mediating a see-saw balance between effective/protective immunity and excessive infection-induced inflammation that can cause collateral tissue damage. African trypanosomes are known to trigger a strong type I pro-inflammatory response, which contributes to peak parasitaemia control, but this can culminate into the development of immunopathologies, such as anaemia and liver injury, if not tightly controlled. In this context, the macrophage migration inhibitory factor (MIF) and the interleukin-10 (IL-10) cytokines may operate as a molecular “Yin-Yang” in the modulation of the host immune microenvironment during African trypanosome infection, and possibly other infectious diseases. MIF is a pleiotropic pro-inflammatory cytokine and critical upstream mediator of immune and inflammatory responses, associated with exaggerated inflammation and immunopathology. For example, it plays a crucial role in the pro-inflammatory response against African trypanosomes and other pathogens, thereby promoting the development of immunopathologies. On the other hand, IL-10 is an anti-inflammatory cytokine, acting as a master regulator of inflammation during both African trypanosomiasis and other diseases. IL-10 is crucial to counteract the strong MIF-induced pro-inflammatory response, leading to pathology control. Hence, novel strategies capable of blocking MIF and/or promoting IL-10 receptor signaling pathways, could potentially be used as therapy to counteract immunopathology development during African trypanosome infection, as well as during other infectious conditions. Together, this review aims at summarizing the current knowledge on the opposite immunopathological molecular “Yin-Yang” switch roles of MIF and IL-10 in the modulation of the host immune microenvironment during infection, and more particularly during African trypanosomiasis as a paradigm.

The immunomodulatory effect of koumine on B cells under dependent and independent responses by T cells

Dysregulated activation of polyclonal B cells and production of pathogenic antibodies are involved in the development of rheumatoid arthritis (RA). Therefore, targeted B cell therapy is effective against RA. Gelsemium elegans (Gardn. & Champ.) Benth., a toxic plant widely distributed in Southeast Asia, has been used for treating rheumatoid pain, neuropathic pain, spasticity, skin ulcers, and cancers for many years in traditional Chinese medicine. Koumine, an alkaloid monomer from Gelsemium elegans Benth., exerts therapeutic effects against RA. However, whether koumine affects B cells remains unknown. In this study, the effect of koumine on B cells under T cell-independent (TI) and T cell-dependent (TD) immune responses is investigated in vitro and in vivo. Mouse primary B cells were obtained by immunomagnetic bead sorting, and immunomodulatory effects of koumine on the activation, proliferation, and differentiation of B cells were determined in TI and TD models induced by lipopolysaccharide (LPS) and anti-CD40 antibodies in vitro, respectively. The humoral immune responses of TI and TD were established using NP-AECM-FICOLL and NP-CGG in C57BL/6J mice, respectively. We found that koumine inhibited B cell differentiation in the TI model and inhibited B cell activation and proliferation in the TD model in vitro. Koumine also inhibited antibody secretion in TI immune response, TD initial immune response, and in TD secondary immune response. Our results reveal that koumine has a direct and indirect immune regulatory effect on B cells, showing that it can directly inhibit the differentiation and secretion of autoantibodies after abnormal activation of B cells, and indirectly inhibit the activation and proliferation of TD B cells to reduce the secretion of antibodies. It may be an important mechanism for its anti-RA effect in mice, providing a rationale and laboratory data support for the application of koumine in anti-human RA therapy.