Herpes simplex viruses, circulate in human population in two serotypes, namely HSV-1 and HSV-2. These DNA viruses are very common and cause a variety of persistent and recurrented diseases.

Abstract

III

Abstract

Herpes simplex viruses, circulate in human population in two serotypes, namely HSV-1 and HSV-2. These DNA viruses are very common and cause a variety of persistent and recurrented diseases.

HSV-1 is responsible of cold sore, a disease tipically characterized by facial febrile vescicles, HSV-2 cause a similar disease in genital organs.

In the last years this distinction has become confusing due to the changes in sexual behaviour, to an extent that HSV-1 isolation from genital lesions is now a common event. Also, their incidence is steadily increasing. In the last 25 years the genital herpes infections increased of 30% and now ranks as fifth amongst sexually transmitted diseases.

Prophylactic vaccines inducing strong cell-mediated responses appear to be the most effective means to contain virus dissemination and disease.

Unfortunately in spite of countless attempts, no anti-HSV vaccine is available to date.

On these premises, the aim of this work was the development of a HSV vaccine built on a third generation, self-inactivating, lentiviral vector.

To increase safety and minimize the generation of infectious particles, the virion, containing the vaccine vector, is produced by a split-component system in which the viral proteins are provided by three plasmids (envelope, packaging and vector construct)

As a further safety measure, the vector itself was produced from the feline immunodeficiency virus (FIV), a lentivirus similar to human immunodeficiency virus (HIV) from which highly efficient vectors were derived, but that neither infects nor causes diseases in humans.

The HSV immunogen consisted of the HSV-1 glycoprotein B (gB), a surface receptor with a high immunogenic potential, that was cloned into the FIV- derived vector.

Of note, HSV-1 gB has been shown to induce cross-protection also against

HSV-2. For this reason, this protein seemed a suitable candidate as a vaccine

against both serotypes.

Abstract

IV

Vaccine vectors were characterized in vitro for their ability to transfect and transduce several cell types and to stably express gB. The selected vaccine was then tested for ability to induce cell-mediated immune responses into C57BL/6 mice.

Vaccination induced a gB-specific CD8

T-cell immune response that was absent in the control mice inoculated with an empty vector. Furthermore, the specific immune response was long-lasting and increased over time.

This vector is now being tested for protection against a fully virulent HSV-1 challenge.

These results will be of guidance for further improvements of the vaccine.