Although antiretroviral therapy can suppress HIV-1 infection to undetectable levels of plasma viremia, integrated latent HIV-1 genomes that encode replication competent virus persist in resting CD4+ T cells. This latent HIV-1 reservoir represents a major barrier to a cure. Currently, there are substantial ongoing efforts to identify therapeutic approaches that will eliminate or reduce the size of this latent HIV-1 reservoir. In this regard, a sensitive assay which can accurately and rapidly quantify inducible replication competent latent HIV-1 from resting CD4+ T cells is essential for HIV-1 eradication studies. Here we describe a reporter cell-based assay to quantify inducible replication competent latent HIV-1. This assay has several advantages over existing technology in that it: (i) is sensitive; (ii) requires only a small blood volume; (iii) is faster, less labor intensive, and less expensive, and (iv) can be readily adapted to a high-throughput format. Using this assay we show that the size of the inducible latent HIV-1 reservoir in aviremic participants on therapy is approximately 70-fold larger than previous estimates.

Plasma viral load and CD4 counts are effective for clinical monitoring, but they do not give a full representation of HIV-1 quasispecies in cellular reservoirs, the major repository of replication-competent HIV-1 in infected individuals. We sought to develop a diagnostic system that might stimulate the replication-competent HIV-1 reservoirs for enhanced clinical monitoring, including selection of antiretroviral regimens. Whole-blood samples from 45 HIV-infected individuals were collected into 1 ViraStim HIV-1 activation tube and 1 EDTA tube. Samples were tested for viral load and cell type-specific HIV-1 replication. Further, 7 matched activated/nonactivated samples were sequenced using the Trugene HIV-1 genotyping kit. The percentage of patients with replication-competent virus in peripheral blood mononuclear cells (PBMCs) varied, depending on the baseline plasma viral load in the EDTA tubes. Six out of 24 patients with a starting plasma viral load of <20 copies/ml (cp/ml), 6 out of 8 patients with starting viral loads of >20 and <1,000 cp/ml, and 8 out of 13 patients with starting viral loads of >1,000 all showed increases in viral replication of >5-fold. These increases came from cellular reservoirs in blood as determined by simultaneous ultrasensitive subpopulation staining/hybridization in situ (SUSHI). When resistance genotypes in plasma from activation tubes were compared to those from EDTA tubes for 7 patients, all patients showed additional mutations in the activation tube, while 3 patients demonstrated additional genotypic resistance determinants. We show that HIV-1 viral replication can be stimulated directly from infected whole blood. The sequencing results showed that 3 of 7 cases demonstrated additional drug resistance following stimulation.

Comparing the IncellPREP homogenization and FNA demonstrated a strong correlation (r - 0.8) for expression of PD-L1. We compared PD-L1 expression by flow cytometry using a 1 % cutoff for positivity in the tumor cell population and a 1 % cutoff of cells with at least 1+ intensity in immunohistochemically stained tissue sections as positive. Ten of 12 lung tumor samples were concordant while 2 were discordant. PD-L1 expression by flow cytometry varied widely (1.2-89.4 %) even in the positive concordant cases. In addition, PD-L1 expression in the aneuploid tumor population did not necessarily agree with the expression in the diploid tumor population. Fine, unequivocal quantification of PD-L1 on tumor and immune cells in NSCLC may allow for better prediction of response to therapies. The present study also offers a technology that can create a universal sample type from either FNA or fresh tissue.

The nonsubjective OncoTect iO Lung Assay has been shown to be at least as accurate and sensitive as IHC for the detection of PD-L1 expression while providing additional information to guide treatment.

114 Background: Research into causality of head and neck squamous cell carcinoma (HNSCC) has found a link to HPV infections affiliated with better survival than tobacco associated HNSCC. Currently, p16 immunohistochemistry is used as a predictive biomarker for HPV infection in HNSCC. We were interested in looking at an additional biomarker, HPV E6,E7 mRNA overexpression by flow cytometry, to see if it correlated with p16 status. Each test looks at a different marker of HPV infection, p16 as a surrogate of E7 activity, and E6,E7 mRNA overexpression as a marker of transcriptionally active and integrated virus. Currently p16 positive samples are confirmed with an ISH assay. Additionally, we looked at the PD-L1 expression in these tumors to see if it correlated with HPV mRNA overexpression. Advances in immuno-oncology have brought immunotherapy to the forefront of cancer treatment including HNSCC. Methods: Swabs were collected from Institut Gustave Roussy patients with lesions of the oral pharynx. Swabs were placed into a vial with a proprietary fixation solution and shipped overnight for processing. Upon receipt, samples were passed through a 35 uM filter to remove aggregates. Cells underwent in situ hybridization with E6, E7 mRNA probes (HPV OncoTect), were labeled with PD-L1 Ab, and then stained with a cell cycle dye identify single nucleated cells prior to analysis on the flow cytometer. FFPE biopsy tissue of the lesion was tested with p16 IHC. Positive samples were confirmed by ISH. Results: We analyzed samples from 27 patients with oral cancer with the combined E6, E7 mRNA/PD-L1 assay by flow cytometry and p16/ISH. Concordance between HPV E6,E7 mRNA positive results and p16 positive confirmed by ISH was 74%. Interestingly, PD-L1 expression was seen only in samples without HPV infection (according to HPV E6,E7 mRNA flow result). Samples are still being accrued and updated data will be presented at the meeting. Conclusions: Here we report a novel assay to quantify both HPV E6, E7 mRNA and PD-L1 simultaneously in single cells from head and neck squamous cell carcinoma. In addition, the ability to characterize both E6,E7 mRNA expression and PD-L1 in one test can provide clinicians with insight into treatment options.