Steffanie Sabbaj

People with HIV (PWH) exhibit persistent immune activation despite effective antiretroviral therapy, contributing to risk of non-AIDS-associated comorbidities such as cancer. Cell populations reflecting immune remodeling trajectories preceding malignancy are poorly characterized. Using peripheral blood mononuclear cells from an adult cohort (25–65 yr), we quantified the tetraspanin CD151 on T cells in people without HIV (PWOH), PWH without documented cancer during follow-up, and PWH who subsequently developed a non-AIDS-defining cancer (PWHc), with samples collected a median of 5 yr prior to cancer diagnosis. In PWOH, CD4+CD151+ T cell frequencies increased with age, consistent with physiologic immune aging. In contrast, elevated CD4+CD151+ frequencies were observed at younger ages in both HIV-positive groups, with the typical age-associated increase attenuated. Notably, frequencies were highest in PWHc. CD151 expression was not associated with increased CD25 or CD69, indicating that expansion was not explained by generalized T cell activation. Instead, CD4+CD151+ T cells were enriched for granzyme B and localized predominantly to CD28− effector memory (CD45RA−CCR7−) compartments, consistent with a cytotoxic CD4+ (cCD4) phenotype. Single-cell RNA sequencing of 1 participant per group identified a cCD4+ transcriptional cluster enriched in the PWHc sample. Here, we report that CD151 identifies a cCD4 T cell lineage that accumulates with age in PWOH but appears prematurely expanded in virally suppressed PWH, particularly in PWHc. These findings support CD151+cCD4 T cell expansion as a feature of altered immune remodeling detectable years before cancer diagnosis, suggesting a potential role in mechanisms linking chronic immune dysregulation to malignancy risk in PWH.

This study aimed to better understand the importance of CD8 T cell responses in protective immunity to chlamydia. In women evaluated for reinfection at a 3-month follow-up visit after treatment for chlamydia, the presence or magnitude of Chlamydia trachomatis-specific CD8 interferon-gamma (IFN-γ) responses to Momp and Pgp3 peptide pools was not associated with reinfection status, despite having an increased frequency of responses compared to C. trachomatis CD4-specific T cells. However, reinfected women with detectable interferon-gamma (IFN-γ)-producing CD8 T cells had lower C. trachomatis bacterial load compared to women without these CD8 T cell responses. Moreover, the frequency of IFN-γ-producing CD8 T cells was inversely associated with C. trachomatis bacterial load. We further determined that C. trachomatis-specific IFN-γ-producing CD8 T cells were predominately late differentiated effector memory T cells that re-expressed CD45RA (Temra; CCR7-CD45RA+) or effector memory T cells (Tem; CCR7-CD45RA-). Together, these data support the concept that CD8 T cells may contribute to protective immunity against chlamydia in women.

While the role of breast milk antibodies to protect infants from human cytomegalovirus (HCMV) has been investigated, the role of T-cells has received little attention. We compared the frequency of memory T-cell populations in breast milk between mothers of infants who acquired breast milk HCMV (transmitters) and those with uninfected infants (nontransmitters). Nontransmitter mothers had an increased frequency of CD8+ effector memory T-cells (Tem) in their breast milk. In addition, we describe tissue-resident memory T cells (Trm) in breast milk and demonstrate most were Tem. We present data that nontransmitter mothers have increased frequency of CD8+ Trm in their breast milk when compared to transmitters and that Trm frequency is inversely correlated with breast milk HCMV viral load. Lastly, using scRNA-seq analysis we identified a unique population of T-cells in nontransmitters and demonstrate that these cells comprise CD8+ Trm. These studies suggest that CD8+ Trm may play a role in preventing viral transmission via breast milk to infants.

With advances in HIV treatment, people with HIV (PWH) are living longer but experience aging-related comorbidities, including cognitive deficits, at higher rates than the general population. Previous studies have shown alterations in lysosomal proteins in blood from PWH with severe dementia. However, these markers have not been evaluated in PWH with milder neurocognitive impairment. We sought to determine whether levels of the lysosomal cysteine protease cathepsin B (CatB) and its endogenous inhibitor cystatin B (CysB) were altered in PWH with neurocognitive impairment and whether antiretroviral therapy (ART) further influenced these levels. Peripheral blood mononuclear cells were obtained from the tenofovir arm of a multicenter clinical trial in which ART-naive, HIV+ participants received treatment for 48 weeks (ACTG A5303, NCT01400412). PWH were divided by neurocognitive status (eg, with or without neurocognitive impairment) before ART initiation. Intracellular levels of CatB and CysB were measured in T cells and monocytes by means of flow cytometry. Levels of CysB were significantly decreased in both CD4⁺ T cells and CD8⁺ T cells after 48 weeks of ART in HIV+ participants without neurocognitive impairment but not in participants with neurocognitive impairment. Levels of CysB were increased in CD14⁺ monocytes from the participants with neurocognitive impairment after ART. Levels of CysB and CatB positively correlated regardless of HIV, neurocognitive status, or exposure to ART. These findings suggest that CysB has the potential to provide mechanistic insight into HIV-associated neurocognitive disorders or provide a molecular target for systemic monitoring or treatment of neurocognitive impairment in the context of ART and should be investigated further.

A subset of COVID-19 patients exhibit post-acute sequelae of COVID-19 (PASC), but little is known about the immune signatures associated with these syndromes. We investigated longitudinal peripheral blood samples in 50 individuals with previously confirmed SARS-CoV-2 infection, including 20 who experienced prolonged duration of COVID-19 symptoms (lasting more than 30 days; median = 74 days) compared with 30 who had symptom resolution within 20 days. Individuals with prolonged symptom duration maintained antigen-specific T cell response magnitudes to SARS-CoV-2 spike protein in CD4 ⁺ and circulating T follicular helper cell populations during late convalescence, while those without persistent symptoms demonstrated an expected decline. The prolonged group also displayed increased IgG avidity to SARS-CoV-2 spike protein. Significant correlations between symptom duration and both SARS-CoV-2–specific T cells and antibodies were observed. Activation and exhaustion markers were evaluated in multiple immune cell types, revealing few phenotypic differences between prolonged and recovered groups, suggesting that prolonged symptom duration is not due to persistent systemic inflammation. These findings demonstrate that SARS-CoV-2–specific immune responses are maintained in patients suffering from prolonged post–COVID-19 symptom duration in contrast to those with resolved symptoms and may suggest the persistence of viral antigens as an underlying etiology.

The biomolecular mechanisms controlling latent HIV-1 infection, despite their importance for the development of a cure for HIV-1 infection, are only partially understood. For example,ex vivostudies have recently shown that T cell activation only triggered HIV-1 reactivation in a fraction of the latently infected CD4+ T cell reservoir, but the molecular biology of this phenomenon is unclear. We demonstrate that HIV-1 infection of primary T cells and T cell lines indeed generates a substantial amount of T cell receptor (TCR)/CD3 activation-inert latently infected T cells. RNA-level analysis identified extensive transcriptomic differences between uninfected, TCR/CD3 activation-responsive and -inert T cells, but did not reveal a gene expression signature that could functionally explain TCR/CD3 signaling inertness. Network analysis suggested a largely stochastic nature of these gene expression changes (transcriptomic noise), raising the possibility that widespread gene dysregulation could provide a reactivation threshold by impairing overall signal transduction efficacy. Indeed, compounds that are known to induce genetic noise, such as HDAC inhibitors impeded the ability of TCR/CD3 activation to trigger HIV-1 reactivation. Unlike for transcriptomic data, pathway enrichment analysis based on phospho-proteomic data directly identified an altered TCR signaling motif. Network analysis of this data set identified drug targets that would promote TCR/CD3-mediated HIV-1 reactivation in the fraction of otherwise TCR/CD3-reactivation inert latently HIV-1 infected T cells, regardless of whether the latency models were based on T cell lines or primary T cells. The data emphasize that latent HIV-1 infection is largely the result of extensive, stable biomolecular changes to the signaling network of the host T cells harboring latent HIV-1 infection events. In extension, the data imply that therapeutic restoration of host cell responsiveness prior to the use of any activating stimulus will likely have to be an element of future HIV-1 cure therapies.

SARS-CoV-2 causes a wide spectrum of clinical manifestations and significant mortality. Studies investigating underlying immune characteristics are needed to understand disease pathogenesis and inform vaccine design. In this study, we examined immune cell subsets in hospitalized and nonhospitalized individuals. In hospitalized patients, many adaptive and innate immune cells were decreased in frequency compared with those of healthy and convalescent individuals, with the exception of an increase in B lymphocytes. Our findings show increased frequencies of T cell activation markers (CD69, OX40, HLA-DR, and CD154) in hospitalized patients, with other T cell activation/exhaustion markers (PD-L1 and TIGIT) remaining elevated in hospitalized and nonhospitalized individuals. B cells had a similar pattern of activation/exhaustion, with increased frequency of CD69 and CD95 during hospitalization followed by an increase in PD1 frequencies in nonhospitalized individuals. Interestingly, many of these changes were found to increase over time in nonhospitalized longitudinal samples, suggesting a prolonged period of immune dysregulation after SARS-CoV-2 infection. Changes in T cell activation/exhaustion in nonhospitalized patients were found to positively correlate with age. Severely infected individuals had increased expression of activation and exhaustion markers. These data suggest a prolonged period of immune dysregulation after SARS-CoV-2 infection, highlighting the need for additional studies investigating immune dysregulation in convalescent individuals.

Tetraspanins are a family of proteins with an array of functions that are well studied in cancer biology, but their importance in immunology is underappreciated. Here we establish the tetraspanin CD151 as a unique marker of T-cell activation and, in extension, an indicator of elevated, systemic T-cell activity. Baseline CD151 expression found on a subset of T-cells was indicative of increased activation of the MAPK pathway. Following TCR/CD3 activation, CD151 expression was upregulated on the overall T-cell population, a quintessential feature of an activation marker. CD151+ T-cell frequencies in the spleen, an organ with increased immune activity, were twice as high as in paired peripheral blood samples. This CD151+ T-cell frequency increase was not paralleled by an increase of CD25 or CD38, demonstrating that CD151 expression is regulated independently of other T-cell activation markers. CD151+ T-cells were also more likely to express preformed granzyme B, suggesting that CD151+ T cells are pro-inflammatory. To this end, HIV-1 patients on antiretroviral therapy who are reported to exhibit chronically elevated levels of immune activity, had significantly higher CD4+CD151+ T-cell frequencies than healthy controls, raising the possibility that proinflammatory CD151+ T cells could contribute to the premature immunological aging phenotype observed in these patients.

Although the ability of HIV-1 to reside in a latent state in CD4+ T cells constitutes a critical hurdle to a curative therapy, the biomolecular mechanisms by which latent HIV-1 infection is established and maintained are only partially understood. E x vivo studies have shown that T cell receptor/CD3 stimulation only triggered HIV-1 reactivation in a fraction of the latently infected CD4+ T cell reservoir, suggesting that parts of the T cell population hosting latent HIV-1 infection events are altered to be TCR/CD3-activation-inert. We provide experimental evidence that HIV-1 infection of primary T cells and T cell lines indeed generates a substantial amount of TCR/CD3 activation-inert latently infected T cells. HIV-1 induced host cell TCR/CD3 inertness is thus a conserved mechanism that contributes to the stability of latent HIV-1 infection. Proteomic and genome-wide RNA-level analysis comparing CD3-responsive and CD3-inert latently HIV-1 infected T cells, followed by software-based integration of the data into protein-protein interaction networks (PINs) suggested two phenomena to govern CD3-inertness: (i) the presence of extensive transcriptomic noise that affected the efficacy of CD3 signaling and (ii) defined changes to specific signaling pathways. Validation experiments demonstrated that compounds known to increase transcriptomic noise further diminished the ability of TCR/CD3 stimulation to trigger HIV-1 reactivation. Conversely, targeting specific central nodes in the generated PINs such as STAT3 improved the ability of TCR/CD3 activation to trigger HIV-1 reactivation in T cell lines and primary T cells. The data emphasize that latent HIV-1 infection is largely the result of extensive, stable biomolecular changes to the signaling network of the host T cells harboring latent HIV-1 infection events. In extension, the data imply that therapeutic restoration of host cell TCR/CD3 responsiveness could enable gradual reservoir depletion without the need for therapeutic activators, driven by cognate antigen recognition. AUTHOR SUMMARY: A curative therapy for HIV-1 infection will at least require the eradication of a small pool of CD4+ helper T cells in which the virus can persist in a latent state, even after years of successful antiretroviral therapy. It has been assumed that activation of these viral reservoir T cells will also reactivate the latent virus, which is a prerequisite for the destruction of these cells. Remarkably, this is not the case and following application of even the most potent stimuli that activate normal T cells through their T cell receptor, a large portion of the latent virus pool remains in a dormant state. Herein we demonstrate that a large part of latent HIV-1 infection events reside in T cells that have been rendered activation inert by the actual infection event. We provide a systemwide, biomolecular description of the changes that render latently HIV-1 infected T cells activation inert and using this description, devise pharmacologic interference strategies that render initially activation inert T cells responsive to stimulation. This in turn allows for efficient triggering of HIV-1 reactivation in a large part of the latently HIV-1 infected T cell reservoir.