Human Papillomavirus Type 16 L1/L2 VLP Experimental Internalisation by Human Peripheral Blood Leukocytes

Human papillomavirus (HPV) accounts for hundreds of thousands of new cases of cervical cancer yearly, and half of these women die of this neoplasia. This study investigates the possibility of HPV16 to infect human peripheral blood leukocytes in ex vivo assays. We have developed a leukocyte separation method from heparinized blood samples aiming cellular integrity and viability. We have expressed humanized L1 and L2 viral capsid proteins in HEK293T epithelial human cells, transiently transfecting them with vectors encoding humanized HPVL1 and L2 genes. Recombinant L1/L2 capsid proteins and structured virus-like particles interacted with human peripheral blood mononuclear cells – lymphocytes and monocytes – and were internalised through a pathway involving CD71 transferrin receptors. This was observed, at a percentile of about 54% T-CD4, 47% T-CD8, 48% B-CD20, and 23% for monocytes-CD14. The group of polymorph nuclear cells: neutrophils-eosinophils-basophils group did not internalise any VLPs. Blockage assays with biochemical inhibitors of distinct pathways, like chlorpromazine, rCTB, filipin, nystatin, liquemin, and sodium azide also evidentiated the occurrence of virus-like particles’ indiscriminate entrance via membrane receptor on mononuclear cells. This study shows that HPV16 L1/L2 VLPs can interact with the plasma membrane surface and successfully enter lymphocytes without requiring a specific receptor.