Correlates of immune-mediated protection to most viral and cancer vaccines are still unknown. This impedes the development of novel vaccines to incurable diseases such as HIV and cancer. In this study, we have used functional genomics and polychromatic flow cytometry to define the signature of the immune response to the yellow fever (YF) vaccine 17D (YF17D) in a cohort of 40 volunteers followed for up to 1 yr after vaccination. We show that immunization with YF17D leads to an integrated immune response that includes several effector arms of innate immunity, including complement, the inflammasome, and interferons, as well as adaptive immunity as shown by an early T cell response followed by a brisk and variable B cell response. Development of these responses is preceded, as demonstrated in three independent vaccination trials and in a novel in vitro system of primary immune responses (modular immune in vitro construct [MIMIC] system), by the coordinated up-regulation of transcripts for specific transcription factors, including STAT1, IRF7, and ETS2, which are upstream of the different effector arms of the immune response. These results clearly show that the immune response to a strong vaccine is preceded by coordinated induction of master transcription factors that lead to the development of a broad, polyfunctional, and persistent immune response that integrates all effector cells of the immune system.

There is limited knowledge on the identity of primary CD4⁺ T cell subsets selectively targeted by HIV-1 in vivo. In this study, we established a link between HIV permissiveness, phenotype/homing potential, and lineage commitment in primary CD4⁺ T cells. CCR4⁺CCR6⁺, CCR4⁺CCR6⁻, CXCR3⁺CCR6⁺, and CXCR3⁺CCR6⁻ T cells expressed cytokines and transcription factors specific for Th17, Th2, Th1Th17, and Th1 lineages, respectively. CCR4⁺CCR6⁺ and CXCR3⁺CCR6⁺ T cells expressed the HIV coreceptors CCR5 and CXCR4 and were permissive to R5 and X4 HIV replication. CCR4⁺CCR6⁻ T cells expressed CXCR4 but not CCR5 and were permissive to X4 HIV only. CXCR3⁺CCR6⁻ T cells expressed CCR5 and CXCR4 but were relatively resistant to R5 and X4 HIV in vitro. Total CCR6⁺ T cells compared with CCR6⁻ T cells harbored higher levels of integrated HIV DNA in treatment-naive HIV-infected subjects. The frequency of total CCR6⁺ T cells and those of CCR4⁺CCR6⁺ and CXCR3⁺CCR6⁺ T cells were diminished in chronically infected HIV-positive subjects, despite viral-suppressive therapy. A high-throughput analysis of cytokine profiles identified CXCR3⁺CCR6⁺ T cells as a major source of TNF-α and CCL20 and demonstrated a decreased TNF-α/IL-10 ratio in CXCR3⁺CCR6⁻ T cells. Finally, CCR4⁺CCR6⁺ and CXCR3⁺CCR6⁺ T cells exhibited gut- and lymph node-homing potential. Thus, we identified CCR4⁺CCR6⁺ and CXCR3⁺CCR6⁺ T cells as highly permissive to HIV replication, with potential to infiltrate and recruit more CCR6⁺ T cells into anatomic sites of viral replication. It is necessary that new therapeutic strategies against HIV interfere with viral replication/persistence in discrete CCR6⁺ T cell subsets.

Lactoferrin (Lf), a multifunctional molecule present in mammalian secretions and blood, plays important roles in host defense and cancer. Indeed, Lf has been reported to inhibit the proliferation of cancerous mammary gland epithelial cells and manifest a potent antiviral activity against human immunodeficiency virus and human cytomegalovirus. The Lf‐binding sites on the cell surface appear to be proteoglycans and other as yet undefined protein(s). Here, we isolated a Lf‐binding 105 kDa molecular mass protein from cell extracts and identified it as human nucleolin. Medium–affinity interactions (≈ 240 nm) between Lf and purified nucleolin were further illustrated by surface plasmon resonance assays. The interaction of Lf with the cell surface‐expressed nucleolin was then demonstrated through competitive binding studies between Lf and the anti‐human immunodeficiency virus pseudopeptide, HB‐19, which binds specifically surface‐expressed nucleolin independently of proteoglycans. Interestingly, binding competition studies between HB‐19 and various Lf derivatives in proteoglycan‐deficient hamster cells suggested that the nucleolin‐binding site is located in both the N‐ and C‐terminal lobes of Lf, whereas the basic N‐terminal region is dispensable. On intact cells, Lf co‐localizes with surface nucleolin and together they become internalized through vesicles of the recycling/degradation pathway by an active process. Morever, a small proportion of Lf appears to translocate in the nucleus of cells. Finally, the observations that endocytosis of Lf is inhibited by the HB‐19 pseudopeptide, and the lack of Lf endocytosis in proteoglycan‐deficient cells despite Lf binding, point out that both nucleolin and proteoglycans are implicated in the mechanism of Lf endocytosis.