Anti-Interleukin-23 Autoantibodies in Adult-Onset Immunodeficiency.

BACKGROUND: Autoantibodies against interleukin-12 (anti-interleukin-12) are often identified in patients with thymoma, but opportunistic infections develop in only some of these patients. Interleukin-12 (with subunits p40 and p35) shares a common subunit with interleukin-23 (subunits p40 and p19). In a patient with disseminated Burkholderia gladioli infection, the identification of both anti-interleukin-23 and anti-interleukin-12 prompted further investigation. METHODS: Among the patients (most of whom had thymoma) who were known to have anti-interleukin-12, we screened for autoantibodies against interleukin-23 (anti-interleukin-23). To validate the potential role of anti-interleukin-23 with respect to opportunistic infection, we tested a second cohort of patients with thymoma as well as patients without either thymoma or known anti-interleukin-12 who had unusual infections. RESULTS: Among 30 patients with anti-interleukin-12 who had severe mycobacterial, bacterial, or fungal infections, 15 (50%) also had autoantibodies that neutralized interleukin-23. The potency of such neutralization was correlated with the severity of these infections. The neutralizing activity of anti-interleukin-12 alone was not associated with infection. In the validation cohort of 91 patients with thymoma, the presence of anti-interleukin-23 was associated with infection status in 74 patients (81%). Overall, neutralizing anti-interleukin-23 was detected in 30 of 116 patients (26%) with thymoma and in 30 of 36 patients (83%) with disseminated, cerebral, or pulmonary infections. Anti-interleukin-23 was present in 6 of 32 patients (19%) with severe intracellular infections and in 2 of 16 patients (12%) with unusual intracranial infections, including Cladophialophora bantiana and Mycobacterium avium complex. CONCLUSIONS: Among patients with a variety of mycobacterial, bacterial, or fungal infections, the presence of neutralizing anti-interleukin-23 was associated with severe, persistent opportunistic infections. (Funded by the National Institute of Allergy and Infectious Diseases and others.).

Reappraisal of Idiopathic CD4 Lymphocytopenia at 30 Years.

BACKGROUND: Idiopathic CD4 lymphocytopenia (ICL) is a clinical syndrome that is defined by CD4 lymphopenia of less than 300 cells per cubic millimeter in the absence of any primary or acquired cause of immunodeficiency. Some 30 years after its original identification, ICL has remained a disease of obscure cause, with limited evidence with respect to its prognosis or management, despite diagnostic and therapeutic innovations. METHODS: We evaluated the clinical, genetic, immunologic, and prognostic characteristics of 108 patients who were enrolled during an 11-year period. We performed whole-exome and targeted gene sequencing to identify genetic causes of lymphopenia. We also performed longitudinal linear mixed-model analyses of T-cell count trajectories and evaluated predictors of clinical events, the response to immunization against coronavirus disease 2019 (Covid-19), and mortality. RESULTS: After the exclusion of patients with genetic and acquired causes of CD4 lymphopenia, the study population included 91 patients with ICL during 374 person-years of follow-up. The median CD4+ T-cell count among the patients was 80 cells per cubic millimeter. The most prevalent opportunistic infections were diseases related to human papillomavirus (in 29%), cryptococcosis (in 24%), molluscum contagiosum (in 9%), and nontuberculous mycobacterial diseases (in 5%). A reduced CD4 count (<100 cells per cubic millimeter), as compared with a CD4 count of 101 to 300 cells, was associated with a higher risk of opportunistic infection (odds ratio, 5.3; 95% confidence interval [CI], 2.8 to 10.7) and invasive cancer (odds ratio, 2.1; 95% CI, 1.1 to 4.3) and a lower risk of autoimmunity (odds ratio, 0.5; 95% CI, 0.2 to 0.9). The risk of death was similar to that in the age- and sex-adjusted general population, but the prevalence of cancer was higher. CONCLUSIONS: Among the study patients, ICL continued to be associated with increased susceptibility to viral, encapsulated fungal, and mycobacterial diseases, as well as with a reduced response to novel antigens and an increased risk of cancer. (Funded by the National Institute of Allergy and Infectious Diseases and the National Cancer Institute; ClinicalTrials.gov number, NCT00867269.).

Inflammasome activation in patients with Kaposi sarcoma herpesvirus (KSHV)-associated disorders.

Kaposi sarcoma herpesvirus (KSHV)-associated disorders include Kaposi sarcoma (KS), primary effusion lymphoma (PEL), KSHV-associated multicentric Castleman disease (MCD) and KSHV-inflammatory cytokine syndrome (KICS). PEL, MCD, and KICS are associated with elevated circulating inflammatory cytokines. However, activation of the inflammasome, which generates IL-1 and IL-18 via active caspase-1/4/5, has not been evaluated in patients with KAD. Here we report that patients with HIV and one or more KAD present with higher plasma levels of IL-18 and increased caspase-1/4/5 activity in circulating monocytes as compared to HIV-negative healthy volunteers (HV) or people with HIV without KAD (PWH). Within KAD subtypes, KICS and MCD shared enhanced caspase-1/4/5 activity and IL-18 production when compared to HV and PWH, while patients with PEL showed remarkably high levels of inflammasome complex formation (known as apoptosis-associated speck-like protein containing a caspase recruitment domain (CARD) (ASC)-speck). Moreover, caspase-1/4/5 activity and IL-18 plasma levels correlated with KSHV viral load, indicating KSHV-driven inflammasome activation in KAD. Accordingly, factors released by KSHV-latently infected cells triggered inflammasome activation and cytokine production in bystander monocytes, in vitro. Finally, both supervised and unsupervised analyses with inflammasome measurements and other inflammatory biomarkers demonstrate a unique inflammatory profile in patients with PEL, MCD, and KICS as compared to KS. Our data indicate that detrimental inflammation in patients with KAD is at least partially driven by KSHV-induced inflammasome activation in monocytes, thus offering novel approaches to diagnose and treat these complex disorders.

SARS-CoV-2 infection perturbs the gastrointestinal tract and induces modest microbial translocation across the intestinal barrier.

SARS-CoV-2 infects via the respiratory tract, but COVID-19 includes an array of non-respiratory symptoms, among them gastrointestinal (GI) manifestations such as vomiting and diarrhea. Here we investigated the GI pathology of SARS-CoV-2 infections in rhesus macaques and humans. Macaques experienced mild infection with USA-WA1/2020 and shed viral RNA in the respiratory tract and stool, including subgenomic RNA indicative of replication in the GI tract. Intestinal immune cell populations were disturbed, with significantly fewer proliferating (Ki67+) jejunal B cells in SARS-CoV-2-infected macaques than uninfected ones. Modest translocation of bacteria/bacterial antigen was observed across the colonic epithelium, with a corresponding significant increase in plasma soluble CD14 (sCD14) that may be induced by LPS. Human plasma demonstrated significant decreases in interleukin (IL)-6 and sCD14 upon recovery from COVID-19, suggesting resolution of inflammation and response to translocated bacteria. sCD14 significantly positively correlated with zonulin, an indicator of gut barrier integrity, and IL-6. These results demonstrate that GI perturbations such as microbial translocation can occur in even mild SARS-CoV-2 infections and may contribute to the COVID-19 inflammatory state.IMPORTANCEThis study investigates gastrointestinal (GI) barrier disruption in SARS-CoV-2 infections and how it may contribute to disease. We observed bacteria or bacterial products crossing from the colon interior (the lumen) to the lamina propria during SARS-CoV-2 infection in macaques. Bacteria/bacterial products are tolerated in the lumen but may induce immune responses if they translocate to the lamina propria. We also observed a significant increase in soluble CD14, which is associated with an immune response to bacterial products. In addition, we observed that humans recovering from COVID-19 experienced a significant decrease in soluble CD14, as well as the inflammatory marker interleukin (IL)-6. IL-6 and sCD14 correlated significantly across macaque and human samples. These findings suggest that SARS-CoV-2 infection results in GI barrier disruption that permits microbial translocation and a corresponding immune response. These findings could aid in developing interventions to improve COVID-19 patient outcomes.

Residual immune dysfunction under antiretroviral therapy.

The usage of combination antiretroviral therapy in people with HIV (PWH) has incited profound improvement in morbidity and mortality. Yet, PWH may not experience full restoration of immune function which can manifest with non-AIDS comorbidities that frequently associate with residual inflammation and can imperil quality of life or longevity. In this review, we discuss the pathogenesis underlying chronic inflammation and residual immune dysfunction in PWH, as well as potential therapeutic interventions to ameliorate them and prevent incidence or progression of non-AIDS comorbidities. Current evidence advocates that early diagnosis and prompt initiation of therapy at high CD4 counts may represent the best available approach for an improved immune recovery in PWH.

Immune responses to SARS-CoV-2 mRNA vaccination in people with idiopathic CD4 lymphopenia.

BACKGROUND: The immunogenicity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccines is variable in individuals with different inborn errors of immunity or acquired immune deficiencies and is yet unknown in people with idiopathic CD4 lymphopenia (ICL). OBJECTIVE: We sought to determine the immunogenicity of mRNA vaccines in patients with ICL with a broad range of CD4 T-cell counts. METHODS: Samples were collected from 25 patients with ICL and 23 age- and sex-matched healthy volunteers (HVs) after their second or third SARS-CoV-2 mRNA vaccine dose. Anti-spike and anti-receptor binding domain antibodies were measured. T-cell receptor sequencing and stimulation assays were performed to quantify SARS-CoV-2-specific T-cell responses. RESULTS: The median age of ICL participants was 51 years, and their median CD4 count was 150 cells/µL; 11 participants had CD4 counts ≤100 cells/µL. Anti-spike IgG antibody levels were greater in HVs than in patients with ICL after 2 and 3 doses of mRNA vaccine. There was no detectable significant difference, however, in anti-S IgG between HVs and participants with ICL and CD4 counts >100 cells/µL. The depth of spike-specific T-cell responses by T-cell receptor sequencing was lower in individuals with ICL. Activation-induced markers and cytokine production of spike-specific CD4 T cells in participants with ICL did not differ significantly compared with HVs after 2 or 3 vaccine doses. CONCLUSIONS: Patients with ICL and CD4 counts >100 cells/µL can mount vigorous humoral and cellular immune responses to SARS-CoV-2 vaccination; however, patients with more severe CD4 lymphopenia have blunted vaccine-induced immunity and may require additional vaccine doses and other risk mitigation strategies.

Prolonged Mpox Disease in People With Advanced HIV: Characterization of Mpox Skin Lesions.

We report 3 complicated and prolonged cases of mpox in people with advanced human immunodeficiency virus (HIV) not on antiretroviral therapy (ART) at mpox diagnosis. Multiple medical countermeasures were used, including prolonged tecovirimat treatment and immune optimization with ART initiation. Immunofluorescence of skin biopsies demonstrated a dense immune infiltrate of predominantly myeloid and CD8+ T cells, with a strong type I interferon local response. RNAscope detected abundant replication of monkeypox virus (MPXV) in epithelial cells and dendritic cells. These data suggest that prolonged mpox in people with advanced HIV may be due to ongoing MPXV replication, warranting aggressive medical countermeasures and immune optimization.

Transcriptionally Active Defective HIV-1 Proviruses and Their Association With Immunological Nonresponse to Antiretroviral Therapy.

A subset of antiretroviral therapy-treated persons with human immunodeficiency virus (HIV), referred to as immunological nonresponders (INRs), fails to normalize CD4+ T-cell numbers. In a case-control study involving 26 INRs (CD4 < 250 cells/µL) and 25 immunological responders (IRs; CD4 ≥ 250 cells/µL), we evaluated the potential contribution of transcriptionally competent defective HIV-1 proviruses to poor CD4+ T-cell recovery. Compared to the responders, the INRs had higher levels of cell-associated HIV RNA (P = .034) and higher percentages of HLA-DR+ CD4+ T cells (P < .001). While not encoding replication-competent viruses, the RNA transcripts frequently encoded HIV-1 Gag-p17 and Nef proteins. These transcripts and/or resulting proteins may activate pathway(s) leading to the immunological nonresponse phenotype.

Treatment of Relapsing HPV Diseases by Restored Function of Natural Killer Cells.

Human papillomavirus (HPV) infections underlie a wide spectrum of both benign and malignant epithelial diseases. In this report, we describe the case of a young man who had encephalitis caused by herpes simplex virus during adolescence and currently presented with multiple recurrent skin and mucosal lesions caused by HPV. The patient was found to have a pathogenic germline mutation in the X-linked interleukin-2 receptor subunit gamma gene (IL2RG), which was somatically reverted in T cells but not in natural killer (NK) cells. Allogeneic hematopoietic-cell transplantation led to restoration of NK cytotoxicity, with normalization of the skin microbiome and persistent remission of all HPV-related diseases. NK cytotoxicity appears to play a role in containing HPV colonization and the ensuing HPV-related hyperplastic or dysplastic lesions. (Funded by the National Institutes of Health and the Herbert Irving Comprehensive Cancer Center Flow Cytometry Shared Resources.).

Mycobacterial Immune Reconstitution Inflammatory Syndrome in HIV is Associated With Protein-Altering Variants in Hemophagocytic Lymphohistiocytosis-Related Genes.

People with HIV (PWH) and mycobacterial infections can develop immune reconstitution inflammatory syndrome (IRIS) after starting antiretroviral therapy. The pathophysiology of mycobacterial-IRIS overlaps with primary hemophagocytic lymphohistiocytosis (pHLH). To assess possible genetic predisposition to IRIS, protein-altering variants in genes associated with HLH were evaluated in 82 PWH and mycobacterial infections who developed IRIS (n = 56) or did not develop IRIS (n = 26). Protein-altering variants in cytotoxicity genes were found in 23.2% of IRIS patients compared to only 3.8% of those without IRIS. These findings suggest a possible genetic component in the risk of mycobacterial IRIS in PWH. Clinical Trials Registration. NCT00286767, NCT02147405.

Severe Mycobacterial Immune Reconstitution Inflammatory Syndrome (IRIS) in Advanced Human Immunodeficiency Virus (HIV) Has Features of Hemophagocytic Lymphohistiocytosis and Requires Prolonged Immune Suppression.

BACKGROUND: People with HIV and mycobacterial infections can develop immune reconstitution inflammatory syndrome (IRIS) after starting antiretroviral therapy (ART). Severe mycobacterial IRIS has an overlapping clinical phenotype with hemophagocytic lymphohistiocytosis (HLH). We evaluated the pathophysiologic similarities between mycobacterial IRIS and HLH to identify clinical and immune predictors of mycobacterial IRIS severity. METHODS: HLH criteria were applied to a longitudinal cohort of 80 patients with HIV (CD4 <100 cells/µL) and mycobacterial infections. Participants were subdivided into IRIS meeting HLH criteria (HLH-IRIS), IRIS without HLH (IRIS), and those without IRIS (non-IRIS). Clinical outcomes were evaluated by regression analyses. Soluble biomarkers and T-cell subsets were assessed at baseline and IRIS-equivalent time points. RESULTS: HLH-IRIS patients required corticosteroids more frequently (OR: 21.5; 95%CI: 5.6-114.8) and for longer duration (21.2; 95%CI: 10.7-31.7 weeks) than those not meeting HLH criteria. Utilizing decision tree analyses, hemoglobin <9.2 g/dL was the best predictor of HLH-IRIS before ART, whereas ferritin, CXCL9 and sCD25 were most diagnostic for HLH at IRIS onset. At the IRIS timepoint, but not baseline, HLH-IRIS patients had lower regulatory and higher activated T cells along with greater production of IFNγ-IL-18 axis biomarkers compared with both IRIS and non-IRIS groups. Principal component analysis corroborated the distinct clustering of HLH-IRIS patients. CONCLUSIONS: Severe mycobacterial IRIS and HLH have an overlapping pathogenesis involving IFNγ and unopposed T-cell activation causing severe inflammatory disease clinically distinguished by hyperferritinemia (hyperferritinemic IRIS [FIRIS]). Hemoglobin, ferritin, CXCL9, and sCD25 identify high-risk patients and may improve risk stratification and therapeutic strategies for mycobacterial IRIS.

Clinical, Virologic, and Immunologic Evaluation of Symptomatic Coronavirus Disease 2019 Rebound Following Nirmatrelvir/Ritonavir Treatment.

BACKGROUND: Nirmatrelvir/ritonavir, the first severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) protease inhibitor, reduces the risk of hospitalization and death by coronavirus disease 2019 (COVID-19) but has been associated with symptomatic rebound after therapy completion. METHODS: Six individuals with relapse of COVID-19 symptoms after treatment with nirmatrelvir/ritonavir, 2 individuals with rebound symptoms without prior antiviral therapy and 7 patients with acute Omicron infection (controls) were studied. Soluble biomarkers and serum SARS-CoV-2 nucleocapsid protein were measured. Nasal swabs positive for SARS-CoV-2 underwent viral isolation and targeted viral sequencing. SARS-CoV-2 anti-spike, anti-receptor-binding domain, and anti-nucleocapsid antibodies were measured. Surrogate viral neutralization tests against wild-type and Omicron spike protein, as well as T-cell stimulation assays, were performed. RESULTS: High levels of SARS-CoV-2 anti-spike immunoglobulin G (IgG) antibodies were found in all participants. Anti-nucleocapsid IgG and Omicron-specific neutralizing antibodies increased in patients with rebound. Robust SARS-CoV-2-specific T-cell responses were observed, higher in rebound compared with early acute COVID-19 patients. Inflammatory markers mostly decreased during rebound. Two patients sampled longitudinally demonstrated an increase in activated cytokine-producing CD4+ T cells against viral proteins. No characteristic resistance mutations were identified. SARS-CoV-2 was isolated by culture from 1 of 8 rebound patients; Polybrene addition increased this to 5 of 8. CONCLUSIONS: Nirmatrelvir/ritonavir treatment does not impede adaptive immune responses to SARS-CoV-2. Clinical rebound corresponds to development of a robust antibody and T-cell immune response, arguing against a high risk of disease progression. The presence of infectious virus supports the need for isolation and assessment of longer treatment courses. CLINICAL TRIALS REGISTRATION: NCT04401436.

Polyfunctional Antigen Specific CD4+ T cell Responses in Patients With Human Immunodeficiency Virus/AIDS and Histoplasmosis Immune Reconstitution Inflammatory Syndrome.

In the combination antiretroviral era, there are limited data regarding the pathogenesis of histoplasmosis immune reconstitution inflammatory syndrome (IRIS) in people with human immunodeficiency virus (HIV). We immunologically characterized 10 cases of histoplasmosis, 4 of whom developed histoplasmosis IRIS. CD4+ T cells in histoplasmosis IRIS demonstrated a significant polyfunctional cytokine response to histoplasma antigen.

Classical complement and inflammasome activation converge in CD14highCD16- monocytes in HIV associated TB-immune reconstitution inflammatory syndrome.

Inflammasome-derived cytokines, IL-1ß and IL-18, and complement cascade have been independently implicated in the pathogenesis of tuberculosis (TB)-immune reconstitution inflammatory syndrome (TB-IRIS), a complication affecting HIV+ individuals starting antiretroviral therapy (ART). Although sublytic deposition of the membrane attack complex (MAC) has been shown to promote NLRP3 inflammasome activation, it is unknown whether these pathways may cooperatively contribute to TB-IRIS. To evaluate the activation of inflammasome, peripheral blood mononuclear cells (PBMCs) from HIV-TB co-infected patients prior to ART and at the IRIS or equivalent timepoint were incubated with a probe used to assess active caspase-1/4/5 followed by screening of ASC (apoptosis-associated speck-like protein containing a CARD domain) specks as a readout of inflammasome activation by imaging flow cytometry. We found higher numbers of monocytes showing spontaneous caspase-1/4/5+ASC-speck formation in TB-IRIS compared to TB non-IRIS patients. Moreover, numbers of caspase-1/4/5+ASC-speck+ monocytes positively correlated with IL-1ß/IL-18 plasma levels. Besides increased systemic levels of C1q and C5a, TB-IRIS patients also showed elevated C1q and C3 deposition on monocyte cell surface, suggesting aberrant classical complement activation. A clustering tSNE analysis revealed TB-IRIS patients are enriched in a CD14highCD16- monocyte population that undergoes MAC deposition and caspase-1/4/5 activation compared to TB non-IRIS patients, suggesting complement-associated inflammasome activation during IRIS events. Accordingly, PBMCs from patients were more sensitive to ex-vivo complement-mediated IL-1ß secretion than healthy control cells in a NLRP3-dependent manner. Therefore, our data suggest complement-associated inflammasome activation may fuel the dysregulated TB-IRIS systemic inflammatory cascade and targeting this pathway may represent a novel therapeutic approach for IRIS or related inflammatory syndromes.

Hyperinflammatory Syndromes After Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Messenger RNA vaccination in Individuals With Underlying Immune Dysregulation.

The development of effective severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) messenger RNA (mRNA) vaccines has been a significant accomplishment. Adverse events are extremely rare, but continued surveillance is important, especially in at-risk populations. In 5 patients with preexisting immune dysregulation, hyperinflammatory syndromes, including hemophagocytic lymphohistiocytosis, developed after SARS-CoV-2 mRNA vaccination. Early recognition of this rare condition is essential.

Clinical and Immunologic Predictors of Mycobacterium avium Complex Immune Reconstitution Inflammatory Syndrome in a Contemporary Cohort of Patients With Human Immunodeficiency Virus.

BACKGROUND: People with human immunodeficiency virus (HIV) can present with new or worsening symptoms associated with Mycobacterium avium complex (MAC) infection shortly after antiretroviral therapy (ART) initiation as MAC immune reconstitution inflammatory syndrome (MAC-IRIS). In this study, we assessed the utility of several laboratory tests as predictors of MAC-IRIS. METHODS: People with HIV with clinical and histologic and/or microbiologic evidence of MAC-IRIS were identified and followed up to 96 weeks post-ART initiation within a prospective study of 206 ART-naive patients with CD4 <100 cells/µL. RESULTS: Fifteen (7.3%) patients presented with MAC-IRIS within a median interval of 26 days after ART initiation. Patients who developed MAC-IRIS had lower body mass index, lower hemoglobin levels, higher alkaline phosphatase (ALP), and increased CD38 frequency and mean fluorescence intensity on CD8+ T cells at the time of ART initiation compared with non-MAC IRIS patients. A decision tree inference model revealed that stratifying patients based on levels of ALP and D-dimer could predict the likelihood of MAC-IRIS. A binary logistic regression demonstrated that higher levels of ALP at baseline were associated with increased risk of MAC-IRIS development. CONCLUSIONS: High ALP levels and increased CD8+ T-cell activation with low CD4 counts at ART initiation should warrant suspicion for subsequent development of MAC-IRIS.

Preserved Mucosal-Associated Invariant T-Cell Numbers and Function in Idiopathic CD4 Lymphocytopenia.

BACKGROUND: Mucosal-associated invariant T (MAIT) cells constitute a subset of unconventional, MR1-restricted T cells involved in antimicrobial responses as well as inflammatory, allergic, and autoimmune diseases. Chronic infection and inflammatory disorders as well as immunodeficiencies are often associated with decline and/or dysfunction of MAIT cells. METHODS: We investigated the MAIT cells in patients with idiopathic CD4+ lymphocytopenia (ICL), a syndrome characterized by consistently low CD4 T-cell counts (<300 cell/µL) in the absence of HIV infection or other known immunodeficiency, and by susceptibility to certain opportunistic infections. RESULTS: The numbers, phenotype, and function of MAIT cells in peripheral blood were preserved in ICL patients compared to healthy controls. Administration of interleukin-7 (IL-7) to ICL patients expanded the CD8+ MAIT-cell subset, with maintained responsiveness and effector functions after IL-7 treatment. CONCLUSIONS: ICL patients maintain normal levels and function of MAIT cells, preserving some antibacterial responses despite the deficiency in CD4+ T cells. CLINICAL TRIALS REGISTRATION: NCT00867269.

The Complement Pathway Is Activated in People With Human Immunodeficiency Virus and Is Associated With Non-AIDS Comorbidities.

Unbiased plasma proteomics in a matched case-control study of treated people with human immunodeficiency virus (PWH) revealed the complement cascade as being among the top pathways enriched in PWH. Specific complement components, namely C5, associated significantly with non-AIDS comorbidity prevalence, and did so more strongly than previously established predictive biomarkers.

Disseminated Mycobacterium marinum in Human Immunodeficiency Virus Unmasked by Immune Reconstitution Inflammatory Syndrome.

Distinguishing disseminated Mycobacterium marinum from multifocal cutaneous disease in persons with human immunodeficiency virus/AIDS can present a diagnostic challenge, especially in the context of immune reconstitution inflammatory syndrome (IRIS). In this work, we demonstrate the utility of flow cytometry and whole genome sequencing (WGS) to diagnose disseminated M. marinum unmasked by IRIS following initiation of antiretroviral therapy. Flow cytometry demonstrated robust cytokine production by CD4 T cells in response to stimulation with M. marinum lysate. WGS of isolates from distinct lesions was consistent with clonal dissemination, supporting that preexisting disseminated M. marinum disease was uncovered by inflammatory manifestations, consistent with unmasking mycobacterial IRIS.