Interleukin-22 (IL-22) is a cytokine with epithelial reparative and regenerative properties that is produced by Th22 cells and by other immune cell subsets. Therefore, we explored the hypothesis that disruption of the gut barrier during HIV infection involves dysregulation of these cells in the gastrointestinal mucosa. Sigmoid IL-22-producing T cell and Th22 cells were dramatically depleted during chronic HIV infection, epithelial integrity was compromised, and microbial translocation was increased. These alterations were reversed after long-term antiretroviral therapy. While all mucosal IL-22-producing T-cell subsets were also depleted very early during HIV infection, at these early stages IL-22 production by non-T-cell populations (including NKp44+ cells) was increased and gut epithelial integrity was maintained. Circulating Th22 cells expressed a higher level of the HIV co-receptor/binding molecules CCR5 and α4β7 than CD4+ T-cell subsets in HIV-uninfected participants, but this was not the case after HIV infection. Finally, recombinant IL-22 was protective against HIV and tumor necrosis factor-α-induced gut epithelial damage in a validated in vitro gut epithelial system. We conclude that reduced IL-22 production and Th22 depletion in the gut mucosa are important factors in HIV mucosal immunopathogenesis.

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CD8+ cytotoxic T lymphocytes (CTL) are adept at killing virally infected cells and cancer cells and releasing cytokines (e.g. IFN-γ) to aid this response. However, during cancer and chronic viral infections, such as with Human Immunodeficiency Virus, this CTL response is progressively impaired due to a process called T-cell exhaustion. Previous work has shown that the glycoprotein, T-cell immunoglobulin and mucin domain-containing protein 3 (Tim-3) plays a functional role in establishing T-cell exhaustion. Tim-3 is highly upregulated on virus and tumor antigen-specific CD8+ T-cells and antagonizing Tim-3 helps restore function of CD8+ T cells. However, very little is known of how Tim-3 signals in CTLs. In this study, we assessed the role of Tim-3 at the immunological synapse as well as its interaction with proximal TCR signaling molecules in primary human CD8+ T cells. Tim-3 was found withinCD8+T cell lipid rafts at the immunological synapse. Blocking Tim-3 resulted in a significantly greater number of stable synapses being formed between Tim-3hi CD8+T cells and target cells, suggesting that Tim-3 plays a functional role in synapse formation. Further, we confirmed that Tim-3 interacts with Lck, but not the phospho-active form of Lck. Finally, Tim-3 colocalizes with receptor phosphatases CD45 and CD148, an interaction that is enhanced in the presence of the Tim-3 ligand, galectin-9. Thus, Tim-3 interacts with multiple signaling molecules at the immunological synapse and characterizing these interactions could aid in the development of therapeutics to restore Tim-3-mediated immune dysfunction.

Cytotoxic CD8 + T cells (CTLs) contain virus infections through the release of granules containing both perforin and granzymes. T cell ‘exhaustion’ is a hallmark of chronic persistent viral infections including HIV. The inhibitory regulatory molecule, T cell Immunoglobulin and Mucin domain containing 3 (Tim-3) is induced on HIV-specific T cells in chronic progressive infection. These Tim-3 expressing T cells are dysfunctional in terms of their capacities to proliferate or to produce cytokines. In this study, we evaluated the effect of Tim-3 expression on the cytotoxic capabilities of CD8 + T cells in the context of HIV infection. We investigated the cytotoxic capacity of Tim-3 expressing T cells by examining 1) the ability of Tim-3 + CD8 + T cells to make perforin and 2) the direct ability of Tim-3 + CD8 + T cells to kill autologous HIV infected CD4 + target cells. Surprisingly, Tim-3 + CD8 + T cells maintain higher levels of perforin, which was mainly in a granule-associated (stored) conformation, as well as express high levels of T-bet. However, these cells were also defective in their ability to degranulate. Blocking the Tim-3 signalling pathway enhanced the cytotoxic capabilities of HIV specific CD8 + T cells from chronic progressors by increasing; a) their degranulation capacity, b) their ability to release perforin, c) their ability to target activated granzyme B to HIV antigen expressing CD4 + T cells and d) their ability to suppress HIV infection of CD4 + T cells. In this latter effect, blocking the Tim-3 pathway enhances the cytotoxcity of CD8 + T cells from chronic progressors to the level very close to that of T cells from viral controllers. Thus, the Tim-3 receptor, in addition to acting as a terminator for cytokine producing and proliferative functions of CTLs, can also down-regulate the CD8 + T cell cytotoxic function through inhibition of degranulation and perforin and granzyme secretion.

T cell Ig mucin domain-containing molecule 3 (Tim-3) is a glycoprotein found on the surface of a subset of CD8+ and Th1 CD4+ T cells. Elevated expression of Tim-3 on virus-specific T cells during chronic viral infections, such as HIV-1, hepatitis B virus, and hepatitis C virus, positively correlates with viral load. Tim-3+ cytotoxic T cells are dysfunctional and are unable to secrete effector cytokines, such as IFN-γ and TNF-α. In this study, we examined potential inducers of Tim-3 on primary human T cells. Direct HIV-1 infection of CD4+ T cells, or LPS, found to be elevated in HIV-1 infection, did not induce Tim-3 on T cells. Tim-3 was induced by the common γ-chain (γc) cytokines IL-2, IL-7, IL-15, and IL-21 but not IL-4, in an Ag-independent manner and was upregulated on primary T cells in response to TCR/CD28 costimulation, as well as γc cytokine stimulation with successive divisions. γc cytokine-induced Tim-3 was found on naive, effector, and memory subsets of T cells. Tim-3+ primary T cells were more prone to apoptosis, particularly upon treatment with galectin-9, a Tim-3 ligand, after cytokine withdrawal. The upregulation of Tim-3 could be blocked by the addition of a PI3K inhibitor, LY 294002. Thus, Tim-3 can be induced via TCR/CD28 costimulation and/or γc cytokines, likely through the PI3K pathway.

Type 1 long-interspersed nuclear elements (L1s) are autonomous retrotransposable elements that retain the potential for activity in the human genome but are suppressed by host factors. Retrotransposition of L1s into chromosomal DNA can lead to genomic instability, whereas reverse transcription of L1 in the cytosol has the potential to activate innate immune sensors. We hypothesized that HIV-1 infection would compromise cellular control of L1 elements, resulting in the induction of retrotransposition events. Here, we show that HIV-1 infection enhances L1 retrotransposition in Jurkat cells in a Vif-and Vpr-dependent manner. In primary CD4؉ cells, HIV-1 infection results in the accumulation of L1 DNA, at least the majority of which is extrachromosomal. These data expose an unrecognized interaction between HIV-1 and endogenous retrotransposable elements, which may have implications for the innate immune response to HIV-1 infection, as well as for HIV-1-induced genomic instability and cytopathicity. L 1 element DNA sequences comprise approximately 17% of the human genome (1, 2). Although the bulk of these sequences are in the form of short 5= truncated insertions, an estimated 100 full-length intact elements are present (3, 4). These intact L1 elements represent the only retrotransposons encoded by the human genome known to be capable of autonomous replication (4-7). Full-length L1 elements are ϳ6 kb in length, comprising a 5=-untranslated region (5=UTR) two open reading frames (ORF1 and ORF2) and a 3=UTR ending in a poly(A) tail (8). ORF1 encodes a 40-kDa protein with RNA chaperone activity, while ORF2 encodes a 150-kDa protein which possesses the reverse transcriptase (RT) and endonuclease functions required for retrotransposition (6,(9)(10)(11)(12)(13)(14)(15)(16)(17). Productive retrotransposition is thought to occur by a mechanism termed target-primed reverse transcription (TPRT), where reverse transcription is primed against genomic DNA at the insertion site and thus occurs in concert with integration (18)(19)(20).Several cases of genetic disease have been traced to gene disruptions caused by L1 retrotransposition events in germ line cells, and L1 retrotransposition in somatic cells has been implicated in oncogenesis and cancer progression (21-26). L1 retrotransposition may also play a role in normal physiology. Previous studies have demonstrated the ability for tagged, engineered L1 elements to retrotranspose in neural progenitor cells, and this, supported by quantitative PCR (qPCR) data showing elevated copy numbers of L1 elements in the adult human brain, has led to the suggestion that L1 retrotransposition may play a role in the generation of neuronal somatic mosaicism (27, 28). The vast amount of L1 element sequence fixed in the human genome has, however, presented a technical challenge to the isolation of novel endogenous L1 genomic insertions in somatic cells.Although TPRT appears to be the primary mechanism by which novel genomic L1 insertions are generated, there is considerable evidence that cytosolic...

In perinatally HIV-1-infected newborns, initiation of cART within 72 hours of birth may significantly reduce the size of the HIV-1 reservoirs. Cessation of cART may be necessary to determine whether functional HIV cure can be achieved in such children.

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