Vector-mediated gene transfer engenders long-lived neutralizing activity and protection against SIV infection in monkeys

Abstract

Antibodies capable of neutralizing a wide array of HIV isolates are rarely elicited by the adaptive immune response during HIV infection, and it is not known how to elicit such protective antibodies by vaccination. Philip Johnson and his colleagues have circumvented this hurdle through gene transfer technology. They show that it is possible to protect monkeys from SIV infection by administering intramuscular injections of adeno-associated virus vectors that express broadly neutralizing antibodies that can access the circulation ( 841–842 pages 951–954 ). The key to an effective HIV vaccine is development of an immunogen that elicits persisting antibodies with broad neutralizing activity against field strains of the virus. Unfortunately, very little progress has been made in finding or designing such immunogens. Using the simian immunodeficiency virus (SIV) model, we have taken a markedly different approach: delivery to muscle of an adeno-associated virus gene transfer vector expressing antibodies or antibody-like immunoadhesins having predetermined SIV specificity. With this approach, SIV-specific molecules are endogenously synthesized in myofibers and passively distributed to the circulatory system. Using such an approach in monkeys, we have now generated long-lasting neutralizing activity in serum and have observed complete protection against intravenous challenge with virulent SIV. In essence, this strategy bypasses the adaptive immune system and holds considerable promise as a unique approach to an effective HIV vaccine.