Deciphering the Role of Mucosal Immune Responses and the Cervicovaginal Microbiome in Resistance to HIV Infection in HIV-Exposed Seronegative Women
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Identifying correlates of protection in HIV-exposed seronegative (HESN) individuals requires identification of HIV-specific local immune responses. Researchers performed a comprehensive investigation of the vaginal mucosa and cervicovaginal microbiome in HESN women. They found elevated antiviral cytokines, soluble immunoglobulins, activated NK cells, CXCR5+ CD8+ T cells, and T follicular helper cells in HESN women compared to HIV-unexposed healthy women. They also found greater bacterial diversity and increased abundance of Gardnerella species in the mucosa of HESN women.
CD4+ T Cells Are Dispensable for Induction of Broad Heterologous HIV Neutralizing Antibodies in Rhesus Macaques
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Researchers investigated the humoral response in vaccinated rhesus macaques with CD4+ T cell depletion, using the VC10014 DNA protein co-immunization vaccine platform (with gp160 plasmids and gp140 trimeric proteins derived from an HIV-1 infected subject). Both CD4+-depleted and non-depleted animals developed comparable Tier 1 and 2 heterologous HIV-1 neutralizing plasma antibody titers. Thus, primates generate HIV neutralizing antibodies in the absence of robust CD4+ T cell help, which has important implications for vaccine development.
Safety, Pharmacokinetics and Antiviral Activity of PGT121, a Broadly Neutralizing Monoclonal Antibody Against HIV-1: A Randomized, Placebo-Controlled, Phase 1 Clinical Trial
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Researchers carried out a double-blind trial of one administration of the HIV-1 V3-glycan-specific antibody (Ab) PGT121 in HIV-uninfected and HIV-infected adults on antiretroviral therapy (ART), as well as an open-label trial of one infusion of PGT121 in viremic HIV-infected adults not on ART. The investigators observed no treatment-related serious adverse events among the 48 participants, and neutralizing anti-drug Abs were not elicited. PGT121 reduced plasma HIV RNA by a median of 1.77 log in viremic participants.
Prior Infection With SARS-CoV-2 WA1/2020 Partially Protects Rhesus Macaques Against Re-Infection With B.1.1.7 and B.1.351 Variants
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Using the rhesus macaque model, researchers addressed whether natural immunity induced by the original SARS-CoV-2 WA1/2020 strain protects against re-challenge with B.1.1.7 and B.1.351, known as the alpha and beta variants of concern, respectively. The investigators infected rhesus macaques with WA1/2020 and re-challenged them on day 35 with WA1/2020 or with the alpha or beta variants. Natural immunity to WA1/2020 led to robust protection against re-challenge with WA1/2020, partial protection against beta, and an intermediate degree of protection against alpha.
A Large Repertoire of B Cell Lineages Targeting One Cluster of Epitopes in a Vaccinated Rhesus Macaque
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A rhesus macaque that was serially immunized six times with the 8-mer epitope for human monoclonal antibody (mAb) 447-52D—specific to the V3 region of gp120 HIV-1—provided a rare opportunity to study the repertoire of antibodies produced upon vaccination against a particular antigenic site. From a blood sample taken 3 weeks after the last immunization, researchers produced 41 V3-specific recombinant mAbs by single B cell isolation and cloning. Sequence analysis revealed 21 B cell lineages (single and clonally related).
IL-21 Enhances Influenza Vaccine Responses in Aged Macaques with Suppressed SIV Infection
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Aging with HIV is associated with low-grade systemic inflammation, immune senescence, and impaired antibody (Ab) responses to such vaccines as influenza (flu). Researchers investigated the role of interleukin (IL)-21, a CD4 T follicular helper cell regulator, on flu vaccine Ab response in rhesus macaques in the context of age and controlled simian immunodeficiency virus (SIV) mac239 infection.
Circulating Integrin α4β7+ CD4 T Cells Are Enriched for Proliferative Transcriptional Programs in HIV Infection
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HIV preferentially infects α4β7+ CD4 T cells, forming latent reservoirs that contribute to HIV persistence, yet the properties of α4β7+ CD4 T cells are poorly understood. Investigating HIV-infected humans and SHIV-infected rhesus macaques, investigators demonstrated that α4β7+ CD4 T cells in blood are enriched for genes regulating cell cycle progression and cellular metabolism. In contrast, rectal α4β7+ CD4 T cells exhibited a core tissue-residency gene expression program.
PD-1 Blockade and Vaccination Provide Therapeutic Benefit Against SIV by Inducing Broad and Functional CD8+ T Cells in Lymphoid Tissue
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Effective HIV therapies must induce functional CD8+ T cells and clear latent viral reservoirs during antiretroviral therapy (ART). Using a rhesus macaque model, researchers showed that therapeutic vaccination under ART using a CD40L plus TLR7 agonist-adjuvanted DNA/modified vaccinia Ankara vaccine regimen induced robust SIV-specific CD4+ and CD8+ T cell responses.
Blocking α4β7 Integrin Delays Viral Rebound in SHIVSF162P3-Infected Macaques Treated with Anti-HIV Broadly Neutralizing Antibodies
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To explore therapeutic potentials of combining anti-HIV broadly neutralizing antibodies (bNAbs) with α4β7 integrin blockade using the monoclonal antibody Rh-α4β7, investigators treated SHIVSF162P3-infected, viremic macaques with bNAbs only or bNAbs and Rh-α4β7. Treatment with bNAbs alone decreased viremia below 200 copies/ml in eight out of eight macaques, but seven of the monkeys rebounded within 3 weeks. In contrast, three of six macaques treated with both Rh-α4β7 and bNAbs maintained viremia below 200 copies/ml for 21 weeks, whereas three of those monkeys rebounded after 6 weeks.
Cytomegalovirus Mediates Expansion of IL-15-Responsive Innate-Memory Cells with SIV Killing Function
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Researchers investigated the effects of rhesus cytomegalovirus (RhCMV) on the immune system in young rhesus macaques to determine if it could modulate the protection mediated by RhCMV-vectored vaccines. RhCMV was associated with dramatic changes in antigen presenting cells, T cells, and NK cells and marked expansion of innate-memory CD8+ T cells via host interleukin-15 (IL-15) production. The researchers also investigated immune changes following administration of RhCMV 68-1–vectored SIV vaccines, which led to expansion of CD8+ T cells with capacity to inhibit SIV replication ex vivo.