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Kaposi sarcoma-associated herpesvirus (KSHV) is an oncogenic virus that causes Kaposi sarcoma, primary effusion lymphoma and multicentric Castleman disease. A vaccine that prevents KSHV infection or serves in the treatment of KSHV-related diseases represents a critical unmet need, however, the types of immune responses a vaccine should elicit have not been well defined. The gH/gL glycoprotein complex is an important target of KSHV-neutralizing antibodies, but the epitope specificities targeted by these antibodies remain unknown. Here, we isolated 12 gH/gL-specific monoclonal antibodies (mAbs) from KSHV-infected donors and performed structure/function analyses. These mAbs bind recombinant gH/gL with nanomolar affinities and epitope binning analyses revealed that the mAbs bind to 5 epitope clusters on gH/gL. Seven mAbs were able to neutralize KSHV infection of epithelial cell lines. Two potent neutralizing mAbs mapped to the EphA2 binding site as determined by inhibition of the receptor-ligand interaction and negative stain electron microscopy (nsEM) of the mAb/gH/gL complex. The epitopes of other neutralizing mAbs targeting novel sites of vulnerability were determined by a combination of cryogenic electron microscopy and nsEM. Together, these mAbs help to define the relevant epitope targets for KSHV vaccine design, have utility in understanding the role of antibodies in preventing KSHV infection, enable the development of immunotherapy approaches, and provide valuable tools to understand the molecular details of the KSHV entry process. Author summaryKSHV is an oncogenic virus that can cause cancer in infected individuals. The virus is most prevalent in sub-Saharan Africa and in men who have sex with men. It is possible this virus could be prevented with an effective vaccine, however, the immune response to this virus has not been well defined. gH/gL, a protein essential for viral fusion, plays an important role in infection and could be a possible vaccine target. To better understand the antibody response to this protein, we sought to isolate and characterize monoclonal antibodies that can bind gH/gL and neutralize viral infection. In this study, we isolate and characterize twelve monoclonal antibodies that could bind to five different regions of the gH/gL protein. Seven of these antibodies can neutralize infection, with two being able to block the gH/gL EphA2 receptor-ligand interaction.

Autoantibodies against envelope (Env) protein encoded by human endogenous retrovirus group K (HERV-K) are prevalent in rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), but it remains unclear which proviruses are responsible for this autoantigen. It also remains poorly understood how the transcription of HERV-K loci is regulated in cells that can produce Env.ResultsWe aligned our neutrophil RNA sequencing data to the new telomere-to-telomere reference genome and found uniquely mapping transcripts from HERV-K101, K102, K104, K108, K109, K117 and ERVK5, of which only K102, K108, and K109 encode an intact Env. Expression of K102 and K108 were higher in SLE than in healthy donors or RA (padj?<?0.05). Transcripts from these proviruses increased in response to interferon-¦Á in monocytes and neutrophils from RA patients and healthy donors, but not in SLE, presumably because they have chronically elevated type I interferons in vivo. Indeed, HERV-K expression was significantly higher in SLE patients with high type I interferon gene signature. Tumor necrosis factor-¦Á and other cytokines and TLR ligands also induced HERV-K102 and K108 transcripts. Interferon-¦Á also increased detectable Env protein in monocytes, macrophages, and neutrophils from RA patients. Among the genes for epigenetic silencers of HERV-K, only TRIM28 was significantly decreased in SLE patients with high interferons (padj?=?0.00024).ConclusionsOur data establish a role for interferons in maintaining increased HERV-K expression in SLE and suggest that interferons or other cytokines can upregulate HERV-K to similar levels in RA. A transient increase may also accompany normal immune responses, suggesting that endogenous retroviruses may have been co-opted for efficient immune responses.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13100-025-00371-y.

BackgroundIn persons living with HIV, antiretroviral therapy (ART) reduces HIV RNA in their plasma and increases CD4?+?T lymphocytes, thus restoring their immune function and reducing mortality rates.MethodsThe heavy and light chains of B cell receptor (BCR) were amplified, sequenced, analyzed, and determined to be anti-CD4 mAb. The cytotoxicity of NK cells mediated by the anti-CD4 mAb was assessed using CCK-8, flow cytometry, ELISA, and western blotting. Detecting the viability/regulation of CD4 cells involved inhibiting the attachment of autoantibodies against CD4 to crucial receptors and detecting the inhibition of key molecules in B cells to produce anti-CD4 mAb in patients with immune non-responders (INR). Furthermore, through Phage Random Peptide Library Screening, we discovered that the AAPMFHSSVQLP-CD4 peptide has an affinity for the anti-CD4 mAb.ResultsAdministering anti-CD4 mAb enhanced NK cytotoxicity. The simultaneous administration of anti-CD4 mAb alongside GST-CD4 alleviated the harmful impacts of anti-CD4 mAb on the CD3?+?population in humanized mice, and HIV virus (p24). Individuals diagnosed with INR displayed abnormal B cell activity, particularly with elevated BAFFR expression and increased levels of anti-CD4 mAb. Nevertheless, suppression of BAFFR hindered B cell function and decreased the production of anti-CD4 mAb. In HIV-infected individuals, the dysregulation of B-cells led to the production of anti-CD4 mAb, which in turn facilitated NK cell cytotoxicity and the CD4?+?T effect by upregulating the expression of BAFFR.ConclusionThe dysregulation of B-cells in person living with HIV increased the production of anti-CD4 mAb, which in turn promoted NK cell cytotoxicity and the CD4?+?T effect.Supplementary InformationThe online version contains supplementary material available at 10.1186/s10020-025-01286-3. Highlights1) B-cell dysregulation increased anti-CD4 mAb levels.2) B cells are abnormally active in patients with INR.3) Knockdown of BAFFR obviously reduced the secretion of anti-CD4 mAb.Supplementary InformationThe online version contains supplementary material available at 10.1186/s10020-025-01286-3.