A large part of rare diseases are caused by genetic factors, making them difficult to be cured using the conventional small or large molecular drugs. Nevertheless, the gene therapy could potentially correct such absence or abnormality of body functions caused by certain genetic disorders, thus bringing better quality of life to those rare-disease patients. Currently, many clinical trials of gene therapies are carried out, and some gene therapies have already been available on the market. The viral vectors are commonly used for the gene delivery. In this paper, a variety of viral vectors for the clinical gene delivery are discussed, including the adeno-associated virus (AAV), the retrovirus, and the lentivirus, focusing on their researches, applications, and developments in clinical trials of rare diseases. Furthermore, the advantages and disadvantages of the viral vectors are evaluated, and the potential applications, as well as the research directions of gene therapies are suggested.

rare diseases  /  viral vectors  /  gene delivery  /  gene therapy