Oestrogen controls Foxp3 expression in regulatory T cells (Treg cells) via a mechanism thought to involve oestrogen receptor alpha (ERα), but the molecular basis and functional impact of ERα signalling in Treg cells remain unclear. We report that ERα ligand oestradiol (E2) is significantly increased in human cervical cancer (CxCa) tissues and tumour-infiltrating Treg cells (CD4+CD25hiCD127low), whereas blocking ERα with the antagonist ICI 182,780 abolishes FOXP3 expression and impairs the function of CxCa infiltrating Treg cells. Using a novel approach of co-immunoprecipitation with antibodies to E2 for capture, we identified binding of E2:ERα complexes to FOXP3 protein in CxCa-derived Treg cells. Chromatin immunoprecipitation analyses of male blood Treg cells revealed ERα occupancy at the FOXP3 promoter and conserved non-coding DNA elements 2 and 3. Accordingly, computational analyses of the enriched regions uncovered eight putative oestrogen response elements predicted to form a loop that can activate the FOXP3 promoter. Together, these data suggest that E2-mediated ERα signalling is critical for the sustenance of FOXP3 expression and Treg cell function in human CxCa via direct interaction of ERα with FOXP3 promoter. Overall, our work gives a molecular insight into ERα signalling and highlights a fundamental role of E2 in controlling human Treg cell physiology.

Intratumoral Teffs represented functionally active subsets of both TH1 and TH2 that were not anergic but were suppressed by multiple Treg subsets, which comprised FOXP3 + Tregs and Tregs secreting transforming growth factor β1 and IL-10. These results imply that the microenvironment of cervical carcinomas harbored both TH1 and TH2 subsets of CD4 Teffs that were functionally active but were perhaps unable to perform because of the overpowering effect of Tregs.

Cervical tumor LCs lacked TLR9 expression and were functionally anergic to all the 3: TLR7, TLR8, and TLR9 ligands, which may play a crucial role in immune tolerance. The exact location of block(s) in TLR7 and TLR8 signaling needs to be investigated, which would have important immunotherapeutic implications.

Background:Antemortem diagnosis of cerebral toxoplasmosis, the second most common opportunistic infection (OI) in HIV-infected individuals in developing countries is a challenge.Materials and Methods:Toxoplasma gondii (T.gondii) -specific serology and nested polymerase chain reaction (nPCR) were evaluated in sera and ventricular/lumbar cerebrospinal fluid (CSF) of 22 autopsy confirmed cases of cerebral toxoplasmosis with HIV and 17 controls. Frequency of concomitant T.gondii infection was investigated in 17 cases of HIV-associated tuberculous meningitis (TBM).Results:The sensitivity, specificity, and positive and negative predictive values of T. gondii IgG on CSF (ventricular and lumbar) and sera was 100% in histology proven cerebral toxoplasmosis (concentrations: 258 ± 50, 231 ± 36, and 646 ± 243 IU/mL, respectively); majority (94%) being high avidity type, suggesting reactivation/reinfection. The sensitivity of B1 nPCR was 100% on ventricular CSF, whereas it was only 77% on lumbar CSF. Based on histology, nPCR, and IgG serology, T. gondii co-infection with TBM was observed in 65% (11/17) of cases.Discussion and Conclusion:CSF IgG serology and nPCR are tests with high sensitivity and specificity for the diagnosis of cerebral toxoplasmosis. TBM and cerebral toxoplasmosis can coexist and should be considered in the background of HIV infection in developing countries.

The frequency of Toxoplasma gondii (Tgondii) infections was investigated during febrile episodes in nonstem cell transplant patients with haematological malignancies (HM). One hundred and sixty-two febrile episodes in 125 HIV-negative patients with HM undergoing treatment at Kidwai Memorial Institute of Oncology, Bangalore, India comprised the study group. Plasma from anticoagulated whole blood was used for amplifying the B1 gene of T. gondii by nPCR. Specific antibodies to T. gondii (IgM and IgG) were tested using commercial kits. Corticosteroid and cotrimoxazole usage during these episodes was 50 and 41%, respectively. Twenty-two of the febrile episodes (14%) were positive for T. gondii; nine of which did not have any other concomitant infecting pathogen and were seen in symptomatic patients. While majority of these (13%) were 'Toxoplasma infection', there was a single case of 'probable Toxoplasma disease' (0.6%). In four of the fatal febrile episodes, T. gondii was the causative agent; two of which did not have any other concomitant infection. None of the patients had undergone stem cell transplantation.

Sasikumar et al.: A novel peptide therapeutic targeting PD1 immune checkpoint with equipotent antagonism of both ligands and a potential for better management of immune-related adverse events.

BackgroundThere has been a dramatic increase in T cell receptor (TCR) sequencing spurred, in part, by the widespread adoption of this technology across academic medical centers and by the rapid commercialization of TCR sequencing. While the raw TCR sequencing data has increased, there has been little in the way of approaches to parse the data in a biologically meaningful fashion. The ability to parse this new type of 'big data' quickly and efficiently to understand the T cell repertoire in a structurally relevant manner has the potential to open the way to new discoveries about how the immune system is able to respond to insults such as cancer and infectious diseases.

e17581 Background: BXCL701 (talabostat previously PT100) is an oral small molecule inhibitor of DPP4, DPP8 and DPP9, which trigger macrophage cell death via pyroptosis resulting in proinflammatory stimulation of the innate immunity pathway. Expression of PD-L1 correlates with amplification of DPP8 and DPP9. In syngeneic animal models, significant tumor responses were observed when BXCL701 was used with checkpoint inhibition. In a prior clinical study, BXCL701 at a total daily dose of 0.6mg (as 0.3mg BID) demonstrated single agent activity in 2 pts with Stage IV melanoma (unpublished). Methods: In this multi-center study, eligible patients (pts) had progressing mCRPC (PCWG3), at least 1 line of systemic therapy and ≤ 2 lines of cytotoxic chemotherapy for mCRPC, no prior anti-PD-1/PD-L1 or other T-cell directed anti-cancer therapy, and an ECOG PS of ≤ 2. Pts received fixed dose pembro (200mg IV q21 days) with escalating doses of BXCL701 (0.4mg and 0.6mg PO QD days 1-14 of 21-day cycles) using a 3X3 design. The key endpoints were safety and identification of the recommended phase 2 dose (RP2D) for the combination. Composite response (RECIST, PSA, CTC), plasma drug concentration and change in relevant immune effector cytokines were also evaluated. Results: Six pts were treated at 2 BXCL701 dose levels of 0.4mg qd (n = 3) and 0.6mg qd (n = 3), with 5 pts having adeno, 1 pt having mixed adeno and SC-NEPC. Prior tx included ADT (n = 6), 2nd generation androgen signaling inhibitors (n = 4), chemo (n = 4), RT (n = 5). Among 3 pts at the BXCL701 dose level of 0.6mg, 1 pt had a DLT of Grade 3 syncope (C1D6) and 1 pt had fatal acidosis (C3D8). A dose-dependent increase in pts with low-grade on-target clinical effects was observed. In the 0.4mg qd cohort 1 pt had lower extremity (LE) edema. Whereas in the 0.6mg qd cohort, all pts had events consistent with cytokine release: 3 had hypotension and 2 pts each had dizziness and LE edema. The 0.6mg/day dose level was expanded using a split dose strategy to improve tolerability while maintaining the daily dose previously associated with objective responses. BXCL701 was quantifiable in plasma. Conclusions: BXCL701 0.4 mg QD on days 1 to 14 of 21-day cycle plus pembrolizumab 200 mg IV on day 1 every 21 days was well tolerated in pts with mCRPC. A dose-dependent increase in on-target clinical effects expected with cytokine upregulation was seen. The final dose expansion using the split dose for the RP2D, plasma drug concentrations and relevant biomarkers will be presented. Clinical trial information: NCT03910660 .