Interaction between HIV-1 Tat and EBV Zta favours immune escape of B cells by downregulating HLA-ABC expression

Both Human immunodeficiency virus (HIV) and Epstein-Barr virus (EBV) are associated with an increased risk of malignancies. People living with HIV frequently have EBV reactivation and develop EBV-associated B-cell malignancies. In this study, we aimed to uncover the involvement of HIV-1 and EBV co-existence in the development of B-cell malignancies. We studied two viral transcriptional activators (HIV-1 Tat and EBV Zta) and their possible interaction since they both have cell-penetration domains and can be found simultaneously in the blood or cells of people with HIV. We found that Tat and Zta directly bound each other in human B cells, T cells, and blood serum. Using RNA-sequencing, we found that combined Tat and Zta action in B cells differed from a simple combination of two proteins. A subset of genes, activated by Tat or Zta alone, that trigger an immune response and antigen presentation in B cells, remained unchanged when two proteins were combined. B cells, treated or transfected with Tat and Zta, exhibited a substantial decrease in HLA-ABC (MHC class I) expression, a critical component of the antigen processing and presentation pathway. HLA-ABC downregulation induced by Tat and Zta interaction conferred protection against cytotoxic T cell recognition of EBV-infected B cells. Tat and Zta interaction was also observed in serum from an HIV-positive individual. To conclude, we demonstrated for the first time the direct interaction between HIV-1 Tat and EBV Zta; this interaction can bring about immune evasion of EBV-infected or transformed B cells. Purified B cells or BLAS cells were treated with Tat (250 ng/ml ~ 25 μM), Zta (1 µg/ml ~ 37 μM) or Tat and Zta (at 250 ng/ml and 1 µg/ml, respectively) or left untreated. 6 h and 48h later cells were collected and RNA was extracted using a NucleoSpin RNA isolation kit (Macherey-Nagel, Germany) following manufacturer’s instructions. Total RNA from BLAS cell lines was also isolated using the NucleoSpin RNA kit following the manufacturer's instructions. Each condition was performed and analyzed in triplicates. The cDNA libraries were constructed and sequenced in Novogene, China.