Vaccine for genital herpes moving closer

A vaccine offering protection against genital herpes in women who are seronegative to both HSV-1 and HSV-2 is in the advanced stages of development. However, it is unlikely that an effective vaccine offering protection for a wider population (ie males and females who are HSV-1 positive) will be developed until we have a better understanding of the way the immune system responds to HSV and in particular, the differences in response between males and females, according to researchers in Australia.

A number of potential vaccines against herpes have been developed and although they have shown promise in animal studies, in some cases, they have proved less effective in clinical trials. A team of researchers from Sydney and Westmead reviewed the history of HSV vaccine development to date in order to assess what further improvements might be required in order to make current vaccines effective for a wide population. While vaccines have successfully been introduced for a wide range of diseases, HSV presents a number of specific challenges. These include the fact that the virus establishes latency in neurons (ie once it has entered the body, it lies dormant in neuron cells, waiting to be reactivated), meaning that it is protected against immune eradication. In addition, HSV possesses many other strategies for evading or delaying the immune response.

A number of potential vaccine candidates have been developed over the past two decades but have shown varying levels of efficacy. In the initial stages, these included more traditional approaches such as live-attenuated viral vaccines (viruses that are mutated to be less virulent than the parent agent), killed (inactivated) vaccines and subunit vaccines containing purified virus. More recently, interest has focused on novel approaches such as recombinant HSV proteins, synthetic peptides and DNA vaccines.

As reported previously on the IHA website (newsdesk January and July 2003) a large-scale study is currently under way to evaluate the efficacy of a vaccine against genital herpes, called Herpevac, in women who test negative for HSV-1 and HSV-2. Earlier trials had shown that the vaccine appears to be effective in this specific group of the population, but does not offer protection for males or for women who had previously tested positive for HSV-1.

The researchers conclude that while important progress has been made in terms of developing a potential vaccine against genital herpes, further study of the immune response induced by HSV infections is needed in order to fully understand the requirements for an effective vaccination strategy. In particular, gender specific differences in various immune parameters need to be examined more closely.

Reference

Vaccination Strategies for Genital Herpes and Neonatal HSV. Herpes 11:1 2004