In-vitro Immunomodulatory activity of Azadirachta indica A.Juss. Ethanol: water mixture against HIV associated chronic CD4+ T-cell activation/ exhaustion

Omalla A Olwenyi,Mariam Nakabuye,Godwin Upoki Anywar,Anthony T Podany,Courtney V Fletcher,Justine Nalunga,Hannah Kibuuka,Fatim Cham,Prossy Naluyima,Michael Semwogerere,Bannet Asingura,Bernard Bagaya,Allan Tindikahwa,Francis Kiweewa,Eliezer Z Lichter,Siddappa N Byrareddy

doi:10.1186/s12906-021-03288-0

Abstract

BackgroundIn Sub-Saharan Africa, herbal therapy continues to be utilized for HIV-1 disease management. However, the therapeutic benefits of these substances remain ambiguous. To date, little is known about the effects of these plant extracts on chronic CD4 + T-cell activation and exhaustion which is partly driven by HIV-1 associated microbial translocation.MethodsEffects of Azadirachta indica, Momordica foetida and Moringa oleifera ethanol: water mixtures on cell viability were evaluated using the Guava PCA system. Then, an in-vitro cell culture model was developed to mimic CD4+ T cell exposures to antigens following HIV-1 microbial translocation. In this, peripheral blood mononuclear cells (PBMCs) isolated from HIV negative (n = 13), viral load < 1000 copies per mL (n = 10) and viral load > 1000 copies per mL (n = 6) study participants from rural Uganda were treated with Staphylococcus enterotoxin B (SEB). Then, the candidate plant extract (A. indica) was added to test the potential to inhibit corresponding CD4+ T cell activation. Following BD Facs Canto II event acquisition, variations in %CD38, %CD69, Human Leukocyte Antigen -DR (HLA-DR), Programmed cell death protein 1 (PD-1), T-cell immunoglobulin and mucin domain-containing protein 3 (Tim-3), interferon gamma (IFN γ) and interleukin 2 (IL-2) CD4 + T cell expression were evaluated.ResultsFollowing exposure to SEB, only A. indica demonstrated a concentration-dependent ability to downregulate the levels of CD4 + T cell activation. At the final concentration of 0.500 μg/mL of A. indica, a significant downregulation of CD4 + CD38 + HLA-DR+ expression was observed in HIV negative (p < 0.0001) and both HIV infected groups (P = 0.0313). This plant extract also significantly lowered SEB induced % CD4+ T cell HLADR, PD-1 and Tim-3 levels. PD-1 and CD69 markers were only significantly downmodulated in only the HIV negative ((p = 0.0001 and p = 0.0078 respectively) and viral load< 1000 copies per ml (p = 0.0078) groups.ConclusionA. indica exhibited the in-vitro immunomodulatory potential to inhibit the continuum of SEB induced CD4+ T-cell activation/ exhaustion without impacting general T-cell specific functions such as cytokine secretion. Additional studies are needed to confirm A. indica as a source of natural products for targeting persistent immune activation and inflammation during ART.

Highlights

In Sub-Saharan Africa, herbal therapy continues to be utilized for HIV-1 disease management
A. indica exhibited the in-vitro immunomodulatory potential to inhibit the continuum of Staphylococcus enterotoxin B (SEB) induced CD4+ T-cell activation/ exhaustion without impacting general T-cell specific functions such as cytokine secretion
Cultural differences and poor health care force people living with HIV (PLWH) resort to herbal therapy for alternative/ complementary treatment [4,5,6,7]. It is common for PLWH who are actively enrolled on antiretroviral therapy (ART) to concurrently use traditional herbal medicines [8]

Summary

Introduction

In Sub-Saharan Africa, herbal therapy continues to be utilized for HIV-1 disease management. In resource-limited settings such as sub-Saharan Africa (SSA), incapacitated health care systems limit access to ART [1,2,3] In these settings, cultural differences and poor health care force PLWH resort to herbal therapy for alternative/ complementary treatment [4,5,6,7]. HIV principally infects CD4+ T cells and skews diverse cellular pathways to favour its replication [9] This is accompanied by persistent CD4+ T cell activation as denoted by increased surface expression of (1) the early activation marker CD69, (2) the antigen presenting molecule Human Leukocyte Antigen – DR (HLA-DR), (3) the metabolite marker CD38 [10, 11]. This state of chronic immune activation is majorly driven by continuous responses to bacterial antigens arising from gut microbial translocation [12]

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Discussion

Conclusion