Evaluation of KIR3DL1/KIR3DS1 allelic polymorphisms in Kenyan children with endemic Burkitt lymphoma

Endemic Burkitt lymphoma (eBL) is a fast-growing germinal center B cell lymphoma, affecting 5-10 per 100,000 children annually, in the equatorial belt of Africa. We hypothesize that co-infections with Plasmodium falciparum (Pf) malaria and Epstein-Barr virus (EBV) impair host natural killer (NK) and T cell responses to tumor cells, and thus increase the risk of eBL pathogenesis. NK cell education is partially controlled by killer immunoglobulin-like receptors and variable expression of KIR3DL1 has been associated with other malignancies. Here, we investigated whether KIR3D-mediated mechanisms contribute to eBL, by testing for an association of KIR3DL1/KIR3DS1 genotypes with the disease in 108 eBL patients and 99 healthy Kenyan children. KIR3DL1 allelic typing and EBV loads were assessed by PCR. We inferred previously observed phenotypes from the genotypes. The frequencies of KIR3DL1/KIR3DL1 and KIR3DL1/KIR3DS1 did not differ significantly between cases and controls. Additionally, none of the study participants was homozygous for KIR3DS1 alleles. EBV loads did not differ by the KIR3DL1 genotypes nor were they different between eBL survivors and non-survivors. Our results suggest that eBL pathogenesis may not simply involve variations in KIR3DL1 and KIR3DS1 genotypes. However, considering the complexity of the KIR3DL1 locus, this study could not exclude a role for copy number variation in eBL pathogenesis.

Interplay between IL-10, IFN-γ, IL-17A and PD-1 Expressing EBNA1-Specific CD4+ and CD8+ T Cell Responses in the Etiologic Pathway to Endemic Burkitt Lymphoma

Simple Summary

Endemic Burkitt lymphoma (eBL) is a common pediatric cancer in sub-Saharan Africa. The incidence of this aggressive B-cell cancer is linked to Plasmodium falciparum (Pf) malaria and Epstein–Barr virus (EBV) co-infections during childhood. Most eBL tumors contain EBV and are characterized by the Epstein–Barr Nuclear Antigen 1 (EBNA1) latency I pattern of viral gene expression. The aim of our study was to compare the phenotypes and functions of CD4⁺ and CD8⁺ T cell responses to EBNA1 in children diagnosed with eBL and in healthy EBV-seropositive children to highlight differences that contribute to the balance between anti-viral immunity and eBL pathogenesis.

Abstract

Children diagnosed with endemic Burkitt lymphoma (eBL) are deficient in interferon-γ (IFN-γ) responses to Epstein–Barr Nuclear Antigen1 (EBNA1), the viral protein that defines the latency I pattern in this B cell tumor. However, the contributions of immune-regulatory cytokines and phenotypes of the EBNA1-specific T cells have not been characterized for eBL. Using a bespoke flow cytometry assay we measured intracellular IFN-γ, IL-10, IL-17A expression and phenotyped CD4⁺ and CD8⁺ T cell effector memory subsets specific to EBNA1 for eBL patients compared to two groups of healthy children with divergent malaria exposures. In response to EBNA1 and a malaria antigen (PfSEA-1A), the three study groups exhibited strikingly different cytokine expression and T cell memory profiles. EBNA1-specific IFN-γ-producing CD4⁺ T cell response rates were lowest in eBL (40%) compared to children with high malaria (84%) and low malaria (66%) exposures (p < 0.0001 and p = 0.0004, respectively). However, eBL patients did not differ in CD8⁺ T cell response rates or the magnitude of IFN-γ expression. In contrast, eBL children were more likely to have EBNA1-specific CD4⁺ T cells expressing IL-10, and less likely to have polyfunctional IFN-γ⁺IL-10⁺ CD4⁺ T cells (p = 0.02). They were also more likely to have IFN-γ⁺IL-17A⁺, IFN-γ⁺ and IL-17A⁺ CD8⁺ T cell subsets compared to healthy children. Cytokine-producing T cell subsets were predominantly CD45RA⁺CCR7⁺ T_NAIVE-LIKE cells, yet PD-1, a marker of persistent activation/exhaustion, was more highly expressed by the central memory (T_CM) and effector memory (T_EM) T cell subsets. In summary, our study suggests that IL-10 mediated immune regulation and depletion of IFN-γ⁺ EBNA1-specific CD4⁺ T cells are complementary mechanisms that contribute to impaired T cell cytotoxicity in eBL pathogenesis.

Abstract A60: Transcriptional profile of CD56negCD16pos Natural Killer cells within endemic Burkitt lymphoma

Endemic Burkitt lymphoma (eBL), the most common pediatric cancer in equatorial Africa, has long been associated with two etiologic agents: Epstein-Barr virus (EBV) and Plasmodium falciparum malaria. On the other hand, Natural Killer (NK) cells are essential in the clearance of infected cells as well as play a critical role in tumor immunosurveillance. Despite chronic viral infections as HIV, HCV, which have been found to promote the expansion of a CD56 (negative) NK cell subset with impaired effector function, previous cancer studies have been limited to investigations of CD56dimCD16pos NK cells. We previously published that eBL children had significantly more CD56negCD16pos NK cells compared to age-matched healthy children from a low and high malaria transmission area. Here, we characterized this CD56negCD16pos NK subset using histology staining, multicolor flow cytometry, and RNA-sequencing. We found CD56negCD16pos NK cells to be morphologically similar to CD56dimCD16pos NK cells but had higher expression of FCGR3B (CD16b) (p=0.000008) and MPEG1 (Perforin 2) (p=0.0000007), and lower expression of KLRF1 (NKp80), IL18RAP and IL18R1 (IL18 receptor) (p=0.000003, p=0.000003 and p=0.00005, respectively). Phenotypically, CD56negCD16pos NK cells share characteristics of adaptive NK cells; however, they differ from “memory-like” NK cells, with consistent expression of NKG2C/CD57, lower expression of NKp46 and CD160, and higher expression of KIR3DL1 compared to CD56dimCD16pos NK cells. Finally, higher plasma levels of IL-12p70 and IL-2 (known to help NK cell activation and proliferation) and IL-6 and MIP1a were found in healthy compared to eBL children. Together, these findings suggest that the expansion of CD56negCD16pos NK cells could help explain diminished tumor immunosurveillance and might be a mechanism by which EBV-infected cells evades NK-cell mediated immunity.

Citation Format: Catherine S. Forconi, Cliff Oduor, John M. Ong’echa, Jeff Bailey, Ann M. Moormann. Transcriptional profile of CD56negCD16pos Natural Killer cells within endemic Burkitt lymphoma [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr A60.

Comparison of HPV detection in HIV-infected and HIV-uninfected Kenyan women with or without cervical dysplasia

e17015

Background: Cervical cancer, a malignancy caused by human papillomavirus (HPV) infection, is the most common malignancy in women living in sub-Saharan African countries including Kenya. HIV co-infection accelerates the natural course of cervical cancer. To determine the specific HPV type distribution in HIV-infected women compared to HIV-uninfected women, with and without evidence of cervical dysplasia. Methods: Demographic information, behavioral data, and a cervical swab were collected from women 18 and 45 years of age, HIV-infected or HIV-uninfected, who presented for cervical cancer screening at Moi Referral and Teaching Hospital in Eldoret, Kenya. Women were triaged based on the presence or absence of cervical dysplasia. HPV testing was performed using the Roche Linear Array Assay. Results were compared between women with or without HIV co-infection and between those with or without cervical dysplasia, using Chi-square tests or Fisher’s exact tests. Results: 223 women had normal VIAs. All had HPV testing, 221 had valid results: 115 HIV-infected women (mean age 37 years) and 106 HIV-uninfected (mean age 33 years). 175 women had abnormal VIAs. 143 women had HPV testing performed, 140 had valid results: 70 HIV-infected women (mean age 38.5 years) and 70 HIV-uninfected (mean age 31.3 years). Greater than 90% of all HIV-infected women in both projects were receiving anti-retroviral therapy at enrollment. HPV of any type was detected in 48% of all women with normal VIA vs. 61% of women with abnormal VIA (P = 0.018). High risk (HR)-HPV was detected in 38% of all women with normal VIA vs. 51% of all women with abnormal VIA (P = 0.012). HIV-uninfected women with normal VIA had significantly lower detection of all HPV (P = 0.026), high risk-HPV (P = 0.018), IARC high risk-HPV (P = 0.047), A9 types (P = 0.050), and individual types HPV 16 (P = 0.0274), HPV 18 (P = 0.007), and HPV 51 (P = 0.009) than HIV-uninfected women with abnormal VIA. Among HIV-infected women, there was no difference in detection of any group of HPV types or individual types with respect to VIA results. Conclusions: HIV-uninfected women without cervical dysplasia had lower detection of oncogenic HPV than HIV-uninfected women with dysplasia. In contrast, HPV detection did not differ among HIV-infected women between those with or without cervical dysplasia. In addition, VIA appears to lack specificity for HPV-associated cervical dysplasia, as 39% of women with abnormal VIA examinations did not have any HPV detected, and 49% of women with abnormal VIA examinations did not have any HR-HPV detected.