The present invention concerns lentiviral vectors enabling the expression of membrane-anchored and secreted antibodies by B cells. This invention results from the development of a new method for adoptive transfer of B-cells transduced with a lentiviral vector (LV) conditionally expressing the secreted or the membrane-anchored form (BCR) of a transgenic immunoglobulin of interest, depending on the maturation status of transduced B-cells. Engineered B-cells producing an ectopic immunoglobulin of interest for ex vivo active immunotherapy, allow long-term memory immune response.