Human immunodeficiency virus type 1 (HIV-1)-specific broadly neutralizing monoclonal antibodies (bNAbs) have to date shown transient viral suppression when administered as monotherapy or as a cocktail of two antibodies^1,2,3,4. A combination of three bNAbs provides improved neutralization coverage of global viruses, which may more potently suppress viral escape and rebound^5,6,7. Here we performed an open-label, two-part study evaluating a single intravenous dose of HIV-1 bNAbs, PGT121, PGDM1400 and VRC07-523LS, in six adults without HIV in part 1 and a multicenter trial of up to six monthly infusions of these three bNAbs in 12 people living with HIV with an antiretroviral therapy (ART) interruption in part 2. The primary endpoints were safety, tolerability and pharmacokinetics, and the secondary endpoints in part 2 were antiviral activity following ART discontinuation, changes in CD4⁺ T cell counts and development of HIV-1 sequence mutations associated with bNAb resistance. The trial met its prespecified endpoints. The bNAb treatment was generally safe and well tolerated. In part 2, 83% of participants (10 of 12) maintained virologic suppression for the duration of antibody therapy for at least 28 weeks, and 42% of participants (5 of 12) showed virologic suppression for at least 38–44 weeks, despite the decline of serum bNAb concentrations to low or undetectable levels. In exploratory analyses, early viral rebound in two individuals correlated with baseline resistance to PGT121 and PGDM1400, whereas long-term virologic control in five individuals correlated with reduced immune activation, T cell exhaustion and proinflammatory signaling following bNAb therapy. Our data show the potential of a triple bNAb cocktail to suppress HIV-1 in the absence of ART. ClinicalTrials.gov registration: NCT03721510.

Long COVID (LC) involves a spectrum of chronic symptoms after acute severe acute respiratory syndrome coronavirus 2 infection. Current hypotheses for the pathogenesis of LC include persistent virus, tissue damage, autoimmunity, endocrine insufficiency, immune dysfunction and complement activation. We performed immunological, virological, transcriptomic and proteomic analyses from a cohort of 142 individuals between 2020 and 2021, including uninfected controls ( n = 35), acutely infected individuals ( n = 54), convalescent controls ( n = 24) and patients with LC ( n = 28). The LC group was characterized by persistent immune activation and proinflammatory responses for more than 180 days after initial infection compared with convalescent controls, including upregulation of JAK-STAT, interleukin-6, complement, metabolism and T cell exhaustion pathways. Similar findings were observed in a second cohort enrolled between 2023 and 2024, including convalescent controls ( n = 20) and patients with LC ( n = 18). These data suggest that LC is characterized by persistent activation of chronic inflammatory pathways, suggesting new therapeutic targets and potential biomarkers of disease.

Interleukin-10 (IL-10) is an immunosuppressive cytokine that signals through STAT3 to regulate T follicular helper (Tfh) cell differentiation and germinal center formation. In SIV-infected macaques, levels of IL-10 in plasma and lymph nodes (LNs) were induced by infection and not normalized with antiretroviral therapy (ART). During chronic infection, plasma IL-10 and transcriptomic signatures of IL-10 signaling were correlated with the cell-associated SIV-DNA content within LN CD4⁺ memory subsets, including Tfh cells, and predicted the frequency of CD4⁺ Tfh cells and their cell-associated SIV-DNA content during ART, respectively. In ART-treated rhesus macaques, cells harboring SIV-DNA by DNAscope were preferentially found in the LN B cell follicle in proximity to IL-10. Finally, we demonstrated that the in vivo neutralization of soluble IL-10 in ART-treated, SIV-infected macaques reduced B cell follicle maintenance and, by extension, LN memory CD4⁺ T cells, including Tfh cells and those expressing PD-1 and CTLA-4. Thus, these data support a role for IL-10 in maintaining a pool of target cells in lymphoid tissue that serve as a niche for viral persistence. Targeting IL-10 signaling to impair CD4⁺ T cell survival and improve antiviral immune responses may represent a novel approach to limit viral persistence in ART-suppressed people living with HIV.

CD4⁺ T cell help is critical for optimal CD8⁺ T cell memory differentiation and maintenance in many experimental systems. In addition, many reports have identified reduced primary CD8⁺ T cell responses in the absence of CD4⁺ T cell help, which often coincides with reduced Ag or pathogen clearance. In this study, we demonstrate that absence of CD4⁺ T cells at the time of adenovirus vector immunization of mice led to immediate impairments in early CD8⁺ T cell functionality and differentiation. Unhelped CD8⁺ T cells exhibited a reduced effector phenotype, decreased ex vivo cytotoxicity, and decreased capacity to produce cytokines. This dysfunctional state was imprinted within 3 d of immunization. Unhelped CD8⁺ T cells expressed elevated levels of inhibitory receptors and exhibited transcriptomic exhaustion and anergy profiles by gene set enrichment analysis. Dysfunctional, impaired effector differentiation also occurred following immunization of CD4⁺ T cell–deficient mice with a poxvirus vector. This study demonstrates that following priming with viral vectors, CD4⁺ T cell help is required to promote both the expansion and acquisition of effector functions by CD8⁺ T cells, which is accomplished by preventing immediate dysfunction.

The mpox outbreak of 2022-2023 involved rapid global spread in men who have sex with men. We infected 18 rhesus macaques with mpox by the intravenous, intradermal, and intrarectal routes and observed robust antibody and T cell responses following all three routes of infection. Numerous skin lesions and high plasma viral loads were observed following intravenous and intradermal infection. Skin lesions peaked on day 10 and resolved by day 28 following infection. On day 28, we re-challenged all convalescent and 3 naive animals with mpox. All convalescent animals were protected against re-challenge. Transcriptomic studies showed upregulation of innate and inflammatory responses and downregulation of collagen formation and extracellular matrix organization following challenge, as well as rapid activation of T cell and plasma cell responses following re-challenge. These data suggest key mechanistic insights into mpox pathogenesis and immunity. This macaque model should prove useful for evaluating mpox vaccines and therapeutics.

Bacille Calmette-Guerin (BCG), an attenuated whole cell vaccine based on Mycobacterium bovis, is the only licensed vaccine against Mycobacterium tuberculosis (Mtb), but its efficacy is suboptimal and it fails to protect against pulmonary tuberculosis. We previously reported that Mtb lacking the virulence genes lprG and rv1410c (ΔLprG) was highly attenuated in immune deficient mice. In this study, we show that attenuated ΔLprG Mtb protects C57BL/6J, Balb/cJ, and C3HeB/FeJ mice against Mtb challenge and is as attenuated as BCG in SCID mice. In C3HeB/FeJ mice, ΔLprG vaccination resulted in innate peripheral cytokine production and induced high polyclonal PPD-specific cytokine-secreting CD4⁺ T lymphocytes in peripheral blood. The ΔLprG vaccine afforded protective efficacy in the lungs of C3H/FeJ mice following both H37Rv and Erdman aerosolized Mtb challenges. Vaccine efficacy correlated with antigen-specific PD-1-negative CD4⁺ T lymphocytes as well as with serum IL-17 levels after vaccination. We hypothesize that induction of Th17 cells in lung is critical for vaccine protection, and we show a serum cytokine biomarker for IL-17 shortly after vaccination may predict protective efficacy.