Biomedical subjects

Lishomwa C Ndhlovu

Publications and source records attributed to Lishomwa C Ndhlovu.

8 recordsLinked to original sources

PubMed2025

Transcriptional signature of induced neurons differentiates virologically suppressed people with HIV from people without HIV.

Neurocognitive impairment is a prevalent comorbidity in virologically suppressed people living with HIV (PLWH), yet the underlying mechanisms remain elusive and treatments lacking. We explored use of participant-derived directly induced neurons (iNs) to model neuronal biology and injury in PLWH. iNs retain age- and disease-related donor features, providing unique opportunities to reveal important aspects of neurological disorders. We obtained primary dermal fibroblasts from 6 virologically suppressed PLWH and 7 matched people without HIV (PWOH). iNs were generated using transcription factors NGN2 and ASCL1 and validated by immunocytochemistry, single-cell RNA-Seq, and electrophysiological recordings. Transcriptomic aging analyses confirmed retention of donor age-related signatures. Bulk RNA-Seq identified 29 significantly differentially expressed genes between PLWH and PWOH iNs. Of these, 16 were downregulated and 13 upregulated in PLWH iNs. Protein-protein interaction network mapping indicated iNs from PLWH exhibited differences in extracellular matrix organization and synaptic transmission. IFI27 was upregulated in PLWH iNs, complementing independent postmortem studies demonstrating elevated IFI27 expression in PLWH-derived brain tissue. FOXL2NB-FOXL2-LINC01391 expression was reduced in PLWH iNs and negatively correlated with neurocognitive impairment. Thus, we identified an iN gene signature of HIV revealing mechanisms of neurocognitive impairment in PLWH.

Humans↗

PubMed2024

A Transcriptional Signature of Induced Neurons Differentiates Virologically Suppressed People Living With HIV from People Without HIV.

Neurocognitive impairment is a prevalent and important co-morbidity in virologically suppressed people living with HIV (PLWH), yet the underlying mechanisms remain elusive and treatments lacking. Here, we explored for the first time, use of participant-derived directly induced neurons (iNs) to model neuronal biology and injury in PLWH. iNs retain age- and disease-related features of the donors, providing unique opportunities to reveal novel aspects of neurological disorders. We obtained primary dermal fibroblasts from six virologically suppressed PLWH (range: 27 - 64 years, median: 53); 83% Male; 50% White) and seven matched people without HIV (PWOH) (range: 27 - 66, median: 55); 71% Male; 57% White). iNs were generated using transcription factors NGN2 and ASCL1, and validated by immunocytochemistry and single-cell-RNAseq. Transcriptomic analysis using bulk-RNAseq identified 29 significantly differentially expressed genes between iNs from PLWH and PWOH. Of these, 16 genes were downregulated and 13 upregulated in PLWH iNs. Protein-protein interaction network mapping indicates that iNs from PLWH exhibit differences in extracellular matrix organization and synaptic transmission. IFI27 was upregulated in iNs from PLWH, which complements independent post-mortem studies demonstrating elevated IFI27 expression in PLWH-derived brain tissue, indicating that iN generation reconstitutes this pathway. Finally, we observed that expression of the FOXL2NB-FOXL2-LINC01391 genome locus is reduced in iNs from PLWH and negatively correlates with neurocognitive impairment. Thus, we have identified an iN gene signature of HIV through direct reprogramming of skin fibroblasts into neurons revealing novel mechanisms of neurocognitive impairment in PLWH.

HAND↗

PubMed2005

Regulatory T cell-like activity of Foxp3+ adult T cell leukemia cells.

Adult T cell leukemia (ATL) is an aggressive neoplastic disease, in which a quarter of the patients develop opportunistic infections due to cellular immunodeficiency. However, the underlying mechanism responsible for the immunosuppression has remained unclear. Recent studies have demonstrated that the leukemia cells from a subset of patients with ATL express Foxp3, a specific marker for CD25+CD4+ regulatory T (Treg) cells, which regulate the immune response by suppressing CD4+ T cell functions. However, whether there is a functional resemblance between ATL cells that have Foxp3 expression and Treg cells is still unknown. In this report, we confirmed the high expression of Foxp3 in leukemia cells from 5 of 12 ATL patients and demonstrated that ATL cells from 3 patients suppressed the proliferation of CD4+ T cells. Similarly, one of six HTLV-I-infected cell lines showed both high Foxp3 expression and suppressive activity. Like Treg cells, the suppression induced by the ATL cells from two patients and the HTLV-infected cell line appeared to be mediated by a cell-cell contact-dependent mechanism. Nevertheless, among the ATL cells that strongly expressed Foxp3, those from two of the five patients showed no apparent suppressive activity. Furthermore, retroviral transfection of Foxp3 did not confer any suppressive function on low Foxp3-expressing HTLV-I-infected cell lines. These results indicate that Foxp3 may be essential but is not sufficient for the Treg-cell-like suppressive activity of ATL cells and HTLV-I-infected cell lines.

Adult↗

PubMed2004

Distinct roles for the OX40-OX40 ligand interaction in regulatory and nonregulatory T cells.

The OX40 (CD134) molecule is induced primarily during T cell activation and, as we show in this study, is also expressed on CD25+CD4+ regulatory T (Treg) cells. A necessary role for OX40 in the development and homeostasis of Treg cells can be inferred from the reduced numbers of the cells present in the spleens of OX40-deficient mice, and their elevated numbers in the spleens of mice that overexpress the OX40 ligand (OX40L). The homeostatic proliferation of Treg cells following transfer into lymphopenic mice was also found to be potentiated by the OX40-OX40L interaction. Suppression of T cell responses by Treg cells was significantly impaired in the absence of OX40, indicating that, in addition to its homeostatic functions, OX40 contributes to efficient Treg-mediated suppression. However, despite this, we found that CD25-CD4+ T cells became insensitive to Treg-mediated suppression when they were exposed to OX40L-expressing cells, or when they were treated with an agonistic OX40-specific mAb. OX40 signaling could also abrogate the disease-preventing activity of Treg cells in an experimental model of inflammatory bowel disease. Thus, although the data reveal important roles for OX40 signaling in Treg cell development, homeostasis, and suppressive activity, they also show that OX40 signals can oppose Treg-mediated suppression when they are delivered directly to Ag-engaged naive T cells.

Animals↗

PubMed2004

Expanding role of T-cell costimulators in regulatory T-cell function: recent advances in accessory molecules expressed on both regulatory and nonregulatory T cells.

A subpopulation of T cells harbors a suppressor phenotype and can significantly dampen autoreactive CD4+ and CD8+ T-cell responses. These regulatory T (Treg) cells, which can arise naturally in the thymus and encompass a CD25+CD4+ T-cell repertoire or be antigenically induced, are central players in the maintenance of self-tolerance. A plethora of O-cell costimulatory and accessory receptor molecules expressed by Treg and/or non-regulatory T cells, such as GITR, OX40, and CTLA-4, are involved in modulating the pathogenesis of numerous autoimmune disorders, transplant rejection, and tumor immunity, as well as the control of infections. Exciting new evidence shows that O-cell costimulators, some of which are identified as hopeful discriminative Treg-cell markers, appear to mediate Treg-cell homeostasis and function. Understanding the biological significance of the O-cell costimulatory molecules and the accessory molecules expressed by Treg cells is a prerequisite to better characterizing this regulatory T-cell population. We provide a synopsis of the current understanding of several costimulatory molecules that can orchestrate the function of both naturally arising and antigen-inducible Treg cells.

Animals↗

PubMed2003

OX40 (CD134) and OX40 ligand interaction plays an adjuvant role during in vivo Th2 responses.

The role of OX40-OX40 ligand (OX40L) interaction in Th cell differentiation remains contentious. In vitro studies have revealed a Th2-biased effect by OX40 signals in T cells. However, in vivo studies demonstrated that OX40-OX40L interaction is involved in responses either Th1 or Th2, or both, which appears to be dependent on the experimental conditions used. We document in our report Th cell differentiation in OX40L-deficient and OX40L-transgenic (Tg) mice in response to protein antigens (Ag) and to Leishmania major (L. major) infection. Upon immunization with protein Ag, we demonstrate the adjuvant effect of OX40 signals during in vivo Th2 responses. However, adjuvant treatment to mice ameliorates the Th2-specific effect of OX40-OX40L interaction and rather induces concurrent promotion of both Th1 and Th2 responses via OX40 signals. Thus, previous reports showing promotion of Th1 response by OX40-OX40L interaction may in actual fact be affected by the adjuvant effects mediated by the various experimental conditions. Indeed, constitutive OX40-OX40L interactions in OX40L-Tg mice converted the normally resistant C57BL/6 strain, into a susceptible status following L. major infection due to an extraordinary elevated Th2 response. These results provide convincing evidence demonstrating that the OX40-OX40L interaction is paramount in the development of Th2 responses in vivo.

Animals↗

PubMed2002

Constitutive OX40/OX40 ligand interaction induces autoimmune-like diseases.

The interaction between OX40 and OX40 ligand (OX40L) is suggested to provide T cells with an effective costimulatory signals during T cell-APC interaction. To examine the in vivo effect of constitutive OX40/OX40L interaction during immune regulation, we report the establishment of OX40L-transgenic (OX40L-Tg) mice that constitutively express OX40L on T cells. Markedly elevated numbers of effector memory CD4(+) T cells, but not CD8(+) T cells, were observed in the secondary lymphoid organs of OX40L-Tg mice. Upon immunization with keyhole limpet hemocyanin in the absence of adjuvant, profound T cell proliferative responses and cytokine productions were seen in the OX40L-Tg mice as compared with wild-type mice. Furthermore, in OX40L-Tg mice administrated with superantigen, this constitutive OX40/OX40L interaction on CD4(+) T cells completely prevented normal in vivo clonal T cell deletion. Interestingly, OX40L-Tg mice on the C57BL/6 background spontaneously developed interstitial pneumonia and inflammatory bowel disease that was accompanied with a significant production of anti-DNA Ab in the sera. Surprisingly, these diseases were not evident on the OX40L-Tg mice on the BALB/c strain. However, such inflammatory diseases were successfully reproducible in recombination-activating gene (RAG)2-deficient mice upon transfer of OX40L-Tg CD4(+) T cells. Blockade of OX40/OX40L interaction in the recipient RAG2-deficient mice completely prevented disease development. The present results orchestrated in this study indicate that OX40/OX40L interaction may be a vital link in our understanding of T cell-mediated organ-specific autoimmunity.

Adoptive Transfer↗

PubMed2002

Consequences of OX40-OX40 ligand interactions in langerhans cell function: enhanced contact hypersensitivity responses in OX40L-transgenic mice.

Langerhans cells (LC) represent the dominant antigen-presenting cells (APC) in the epidermis and thus play an important role in cutaneous immune responses to approaching pathogens. These responses are mediated by several costimulatory molecules after antigenic challenge. OX40 ligand (OX40L), a member of TNF superfamily, is expressed on several APC such as splenic dendritic cells (DC) and activated B cells. This molecule has been reported to provide potent costimulation in APC-T cell interactions upon binding to its cognate receptor, OX40, on activated T cells. Little is known, however, regarding OX40L expression and function on LC. In the present study, we report the expression of both OX40L and OX40 on differentiated LC derived from draining lymph nodes in the FITC-sensitized mice. During contact hypersensitivity responses, OX40L-deficient mice demonstrated a significant reduction in both hapten-induced ear swelling and hapten-specific T cell responses despite intact migratory responses. Conversely, these responses were markedly increased in two different OX40L-transgenic strains with variations in OX40L overexpression. In the LC-induced MLR, OX40L-deficient and OX40L-overexpressing LC were capable of reducing and elevating the responses of allogeneic CD4+ T cells, respectively. Thus the requirement of OX40L during the antigen presentation function of LC in T cell priming is here demonstrated.

Animals↗