CROI 2015 Program and Abstracts

Abstract Listing

Poster Abstracts

Results: SIV RNA was detected in all the animals euthanized at 6 and 10 dpi using both qRT-PCR and ISH, however, SIV RNA was only detected in 2 and 1 out of 3 animals at 3 dpi using qRT-PCR and ISH respectively. Transcriptome analysis showed that hosts had clear responses, with 103, 366 and 1350 differentially expressed genes (DEGs) at 3 dpi, 6 dpi and 10 dpi, respectively. Pathway analysis of DEGs at 6 dpi and 10 dpi pointed to the activation of pyroptosis in addition to innate immune response and inflammation pathways. Multiple genes in pyroptosis pathway were significantly up-regulated in expression. The active form of capase-1, the hallmark of pyroptosis activation, was quantified in CD4 + T cells in rectal draining LNs using flowcytometry. Concurrent with loss of CD4 + T cells in draining LNs after early infection, the level of caspase-1 + CD4 + T cells significantly increased, indicating that the pyroptosis mediated CD4 + T cell death occurs in vivo in early SIV infected lymphatic tissues. Conclusions: This study shows robust host responses to early SIV infection, the activation of pyroptosis pathway, and CD4 + T cell loss mediated by pyroptosis in lymphatic tissues in vivo . Since CD4 + T cell loss and immune activation are the hallmarks of HIV pathogenesis, the CD4 + T cell loss mediated by pyroptosis and associated immune activation in vivo in early SIV infection identified in this study opens a new avenue to design interceptive strategy to prevent CD4 + T cell death. 325 Fibrosis in Lymphoid Tissue Is AssociatedWith Peripheral Blood Regulatory T Cells Julie C. Gaardbo 1 ; Patricia S. Nielsen 2 ; Lise Mette R. Gjerdrum 3 ; Karoline Springborg 4 ; Elisabeth Ralfkiær 4 ; Henrik Ullum 4 ; Åse Andersen 4 ; Susanne D. Poulsen 4 Dr. Susanne D Poulsen, sdn@dadlnet.dk 1 University of Copenhagen, Rigshospitalet, Copenhagen, Denmark; 2 Aarhus University Hospital, Denmark, Aarhus, Denmark; 3 Bispebjerg Hospital, University Hospital of Copenhagen, Denmark, Copenhagen, Denmark; 4 Rigshospitalet, University of Copenhagen, Copenhagen, Denmark Background: HIV may damage the structure in lymphoid tissue replacing the functional space with collagen. Regulatory T cells (Tregs) have anti-inflammatory properties exerting their function in part by secretion of transforming growth factor beta (TGF-b) which is known to induce fibrosis. In pathogenic SIV infection tissue fibrosis induced by TGF-b1-postive Tregs has been demonstrated. Thus, Tregs may participate in the pathogenesis leading to fibrosis in lymphoid tissue in HIV infection as well. We hypothesized that lymphoid tissue fibrosis was associated with percentage of peripheral blood Tregs and the level of immune activation. Methods: Tonsil biopsies from 27 HIV-infected patients were examined. All patients had been on cART for a minimum of two years, had CD4 nadir <250 cells/ m L, and HIV RNA had been ≤ 20 copies/mL for at least two years prior to inclusion in the study. Automated image analysis of tricrome-stained, paraffin-embedded tonsil biopsies determined the amount of fibrosis where A fibrosis was the area of fibrous connective tissue and A lesion the area of the lesion including all tissue elements except epithelia, large lymphocyte clusters, and erythrocytes (see figure). Based on fibrosis index patients were divided into two groups with low fibrosis (n=13) and high fibrosis (n=14). Tregs (CD4+CD25+CD127 low FoxP3+) and activated cells (CD4+CD38+HLA-DR+) were determined in peripheral blood using flow cytometry. Differences between groups were analysed using Mann-Whitney U-test. Results are given as median (IQR). Results: The groups of patients with low fibrosis vs. high fibrosis were similar in regard to age, sex, current CD4 and CD8 cell counts, and CD4 nadir. The group with low fibrosis displayed lower percentage of Tregs compared to the group with high fibrosis (4.8% (4.4-6.9) vs. 6.9% (5.6-8.4), P=0.0186). This was accompanied by lower percentage activated CD4+ cells in low fibrosis vs. high fibrosis (1.5% (1.0-2.2) vs. 2.5% (1.8-4.2), P=0.0319).

Poster Abstracts

Conclusions: Patients with low amount of fibrosis in tonsil tissue also exhibited low percentage Tregs and immune activation, suggesting Tregs to be involved in the pathogenesis of fibrosis in HIV-infected patients on cART 326 Decreased T FR /T FH Ratio in SIV-Infected Rhesus Macaques Ankita Chowdhury ; Perla Del Río-Estrada; Steven Bosinger; Guido Silvestri Emory University, Atlanta, GA, US Background: T follicular helper cells (T FH ) are critical for the development and maintenance of germinal centers (GC) and the humoral immune response. During chronic stages of HIV/SIV infection T FH cells accumulate, possibly as a result of antigenic persistence. The SIV/HIV-associated T FH expansion may also reflect a lack of regulation by suppressive follicular regulatory CD4 + T cells (T FR ) . T FR cells are natural regulatory T cells (T REG ) that migrate into the follicle and, similarly to T FH cells, up-regulate CXCR5, Bcl6 and PD1. Methods: Lymph node (LN) biopsies were obtained from SIV-infected and uninfected rhesus macaque (RM), as well as HIV-infected humans. T FR cells were identified by flow cytometry and immunohistochemistry. Cell-associated viral DNA was measured by RT-PCR and next-generation RNA sequencing was performed on sorted populations from uninfected and SIV-infected RM by Illumina. Results: We identified T FR cells as CD4 + , Foxp3 + , CXCR5 + , PD1 + and Bcl6 + within LN of both humans and RM and confirmed their localization within the GC by immunohistochemistry. RNA sequencing showed that T FR cells share a T FH and T REG transcriptional profile with intermediate expression of FoxP3, Bcl6, PRDM1, IL-10 and IL-21. In

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CROI 2015