Mariano Esteban is an internationally recognized scientist with a long experience in molecular basis of pathogenesis by infectious agents. In particular, his group has made important contributions in understanding the life cycle of vaccinia virus, virus-host cell interactions and the mechanism of action of interferons. Mariano Esteban used this knowledge to develop vaccinia virus vectors as candidate vaccines against diseases like AIDS, malaria and leishmaniasis. His group, in collaboration with colleagues in New York, pioneered a heterologous prime/boost approach that has gained acceptance as an immunization protocol against multiple infectious agents. Esteban's group has developed candidate vaccines against HIV/AIDS that are in clinical trials.