Transient Nature of Long-Term Nonprogression and Broad Virus-Specific Proliferative T-Cell Responses with Sustained Thymic Output in HIV-1 Controllers

HIV-1(+) individuals who, without therapy, conserve cellular anti-HIV-1 responses, present with high, stable CD4(+) T-cell numbers, and control viral replication, facilitate analysis of atypical viro-immunopathology. In the absence of universal definition, immune function in such HIV controllers remains an indication of non-progression.CD4 T-cell responses to a number of HIV-1 proteins and peptide pools were assessed by IFN-gamma ELISpot and lymphoproliferative assays in HIV controllers and chronic progressors. Thymic output was assessed by sjTRECs levels. Follow-up of 41 HIV-1(+) individuals originally identified as "Long-term non-progressors" in 1996 according to clinical criteria, and longitudinal analysis of two HIV controllers over 22 years, was also performed. HIV controllers exhibited substantial IFN-gamma producing and proliferative HIV-1-specific CD4 T-cell responses to both recombinant proteins and peptide pools of Tat, Rev, Nef, Gag and Env, demonstrating functional processing and presentation. Conversely, HIV-specific T-cell responses were limited to IFN-gamma production in chronic progressors. Additionally, thymic output was approximately 19 fold higher in HIV controllers than in age-matched chronic progressors. Follow-up of 41 HIV-1(+) patients identified as LTNP in 1996 revealed the transitory characteristics of this status. IFN-gamma production and proliferative T-cell function also declines in 2 HIV controllers over 22 years.Although increased thymic output and anti-HIV-1 T-cell responses are observed in HIV controllers compared to chronic progressors, the nature of nonprogressor/controller status appears to be transitory

Acquisition of pneumococci specific effector and regulatory Cd4+ T cells localising within human upper respiratory-tract mucosal lymphoid tissue

The upper respiratory tract mucosa is the location for commensal Streptococcus (S.) pneumoniae colonization and therefore represents a major site of contact between host and bacteria. The CD4(+) T cell response to pneumococcus is increasingly recognised as an important mediator of immunity that protects against invasive disease, with data suggesting a critical role for Th17 cells in mucosal clearance. By assessing CD4 T cell proliferative responses we demonstrate age-related sequestration of Th1 and Th17 CD4(+) T cells reactive to pneumococcal protein antigens within mucosal lymphoid tissue. CD25(hi) T cell depletion and utilisation of pneumococcal specific MHCII tetramers revealed the presence of antigen specific Tregs that utilised CTLA-4 and PDL-1 surface molecules to suppress these responses. The balance between mucosal effector and regulatory CD4(+) T cell immunity is likely to be critical to pneumococcal commensalism and the prevention of unwanted pathology associated with carriage. However, if dysregulated, such responses may render the host more susceptible to invasive pneumococcal infection and adversely affect the successful implementation of both polysaccharide-conjugate and novel protein-based pneumococcal vaccines

Exposure to Apoptotic Activated CD4+ T Cells Induces Maturation and APOBEC3G- Mediated Inhibition of HIV-1 Infection in Dendritic Cells

Dendritic cells (DCs) are activated by signaling via pathogen-specific receptors or exposure to inflammatory mediators. Here we show that co-culturing DCs with apoptotic HIV-infected activated CD4+ T cells (ApoInf) or apoptotic uninfected activated CD4+ T cells (ApoAct) induced expression of co-stimulatory molecules and cytokine release. In addition, we measured a reduced HIV infection rate in DCs after co-culture with ApoAct. A prerequisite for reduced HIV infection in DCs was activation of CD4+ T cells before apoptosis induction. DCs exposed to ApoAct or ApoInf secreted MIP-1α, MIP-1β, MCP-1, and TNF-α; this effect was retained in the presence of exogenous HIV. The ApoAct-mediated induction of co-stimulatory CD86 molecules and reduction of HIV infection in DCs were partially abrogated after blocking TNF-α using monoclonal antibodies. APOBEC3G expression in DCs was increased in co-cultures of DCs and ApoAct but not by apoptotic resting CD4+ T cells (ApoRest). Silencing of APOBEC3G in DC abrogated the HIV inhibitory effect mediated by ApoAct. Sequence analyses of an env region revealed significant induction of G-to-A hypermutations in the context of GG or GA dinucleotides in DNA isolated from DCs exposed to HIV and ApoAct. Thus, ApoAct-mediated DC maturation resulted in induction of APOBEC3G that was important for inhibition of HIV-infection in DCs. These findings underscore the complexity of differential DC responses evoked upon interaction with resting as compared with activated dying cells during HIV infection

Improved thymic function in exclusively breastfed infants is associated with higher interleukin 7 concentrations in their mothers' breast milk.

BACKGROUND: In rural Gambians, the season of birth strongly predicts adult mortality. Those born during the harvest season have longer life spans than do those born during the hungry season, and the deaths associated with infectious diseases suggest permanent early-life influences on immunity. Thymic measurements showed significantly smaller thymuses in infants born during the hungry season than in those born during the harvest season. The differences were greatest at 8 wk of age, a time when all infants were exclusively breastfed, which suggests the involvement of breast milk factors. OBJECTIVE: This study tested whether thymic size differences reflect thymic output and ascertained whether thymic output is associated with breast milk interleukin 7 (IL-7) concentrations. DESIGN: We studied thymic size and output in a prospective cohort of 138 Gambian infants born in either the hungry or the harvest season by measuring signal-joint T cell receptor-rearrangement excision circles (sjTRECs) at birth and at 8 wk of age. IL-7 concentrations in breast milk were measured by using an enzyme-linked immunosorbent assay. RESULTS: By age 8 wk, those born in the hungry season had significantly lower sjTREC counts than did those born in the harvest season (0.97 and 2.12 sjTRECs/100 T cells, respectively; P = 0.006). At 1 wk postpartum, the breast milk of mothers of infants born in the hungry season had significantly lower IL-7 than did that of mothers of infants born in the harvest season (79 and 100 pg/mL, respectively; P = 0.02). The findings were similar at 8 wk postpartum. CONCLUSION: These data show a plausible pathway linking external seasonal insults to mothers with thymic development in their infants, which suggests possible implications for long-term programming of immunity

Effect of blockage of CTLA-4 and PDL-1 on CD25^hi cells their suppression of anti-pneumococcal proliferative responses by CD4⁺ cells.

<p>Purified CD25^hi cells were preblocked with anti-human CTLA-4 or anti-human PDL-1 blocking antibodies or isotype control (IgG) antibodies and added back to CD25^hi depleted MNCs (i.e. CD25^- cells) at the same original proportion and then stimulated with SPNT over 8 days and CD4⁺ cells proliferation analysed. Graph shows the mean percentage of proliferating CD4⁺ cells post SPNT stimulation in the anti-human CTLA-4 (<b>a</b>) or anti-human PDL-1 preblocked CD25^hi cells (<b>b</b>) groups (<i>n</i> = 5 each group). (*  = <i>p</i> <0.05).</p

Inhibitory action of anti-pneumococcal responses by regulatory T cells.

<p>Inhibition of mucosal CD4⁺ T cell anti-pneumococcal responses to Ply (<b>a</b>) and SPNT (<b>b</b>) but not to flu (<b>c</b>) by CD25^hi regulatory T cells in subjects above 16 years old as indicated by increased cell proliferation following depletion of CD25^hi cells from tonsil MNC population is observed. Subjects (<i>n</i> = 50) were grouped into those aged less than 17 yrs, 17 to 25 yrs and >25 yrs. Individual subject's proliferative response pre and post CD25^hi cell depletion are shown with a connecting dashed grey line, while solid black bars and black dashed line represent mean proliferative values for undepleted and CD25^hi cell depleted populations. (*  = <i>p</i> <0.05).</p

Effect of restoration/addition of Tregs (CD25^hi) cells back into CD25^hi cell depleted MNC samples on proliferative responses by pneumococcal specific CD4⁺ T cells.

<p>Tonsil MNCs were depleted of CD25^hi cells and left or CD25^hi cells added back at the original proportion (∼10%) or at three fold the original proportion (i.e. 30%). Cells were obtained from individuals (<b>a</b>) >16years (<i>n</i> = 5) and stimulated with SPNT, (<b>b</b>) <17 years (<i>n</i> = 3) and stimulated with SPNT or individuals (<b>c</b>) >16 years and stimulated with flu (<i>n</i> = 5). Percentage of proliferating CD4⁺ cells are shown for each individual (open circles) as well as mean (black bars) proliferation in undepleted or CD25^hi depleted or CD25^hi depleted with CD25^hi added back at the original proportion or CD25^hi depleted with CD25^hi added back at three times the original proportion. (*  = <i>p</i> <0.05).</p

Mucosal CD4 T cell responses to pneumococci during aging and its relation with CAP rates.

<p>(<b>a</b>) Mucosal CD4 T cell responses to pneumococcal peptide antigen display gradual age-related increases from early childhood until mid-20's and remain relatively constant until mid-life. Tonsil MNCs from subjects (<i>n</i> = 80) between the ages of 2 to 39 years and grouped into five age groups were assessed for their CD4 T cell proliferative responses to <i>Strep. Pneumoniae</i> Ply (circles, solid grey line of best fit), SPNT (square, dashed black line of best fit) and flu (triangle, black line of best fit) peptides, error bars show SEM. (<b>b</b>) Graph for data observed by Myles <i>et al</i> showing the trend (black crosses, dashed black line of best fit) of incidence rates of CAP per person/year in the UK at different age groups between 1991-2003 (<i>n</i> = 56332, R² = 0.97) in relation to the trend (grey circles, solid grey line of best fit) of mean total (to Ply and to SPNT) anti-pneumococcal CD4 T cell proliferative responses between the ages of 2 to 39 years old (R² = 0.93). Graph for CAP data was generated with permission from P.R. Myles.</p

Anti-pneumococcal CD4 T cells proliferative responses in adult tonsils and blood during <i>in vitro</i> pneumococcal peptide antigen challenge.

<p>(<b>a</b>) A typical FACS plot for CFSE staining within CD4⁺ cells post simulation with flu or SPNT compared to unstimulated (media alone) cells. (<b>b</b>) Purified tonsil MNCs (<i>n</i> = 8) were stimulated over 9 days with flu or recombinant Ply peptides, or D39 bacterial SPNT or media. CD4⁺ cells identified by FACS staining were assessed for their proliferative responses by CFSE staining. Percent of proliferating CD4⁺ cells post flu, Ply or SPNT stimulation were all significantly higher than media control (*  = <i>p</i> <0.05). (<b>c</b>) Greater proliferative responses to pneumococcal peptides by tonsil compared to blood CD4⁺ cells. Tonsil MNCs and PBMCs from the same individuals (<i>n</i> = 5), were purified and stimulated <i>in vitro</i> with flu, Ply or SPNT and CD4⁺ cell proliferation assessed after 9 days. No significant difference was observed between tonsil (open bars) and blood (filled bars) CD4⁺ responses to flu but were significant to SPNT (*  =  <i>p</i> <0.05) and almost significant (#  =  <i>p</i> 0.06) for Ply. Values were calculated with the background (i.e. media alone) proliferation subtracted. Error bars show the SEM.</p