Benefits and drawbacks

The use of viruses as tracers has its benefits and its drawbacks. As such, there are some applications in which viruses are an excellent tracer, and other applications in which there are better methods to use.

Benefitsedit

One of the benefits of using viral tracers is the ability of the virus to jump across synapses. This allows for tracing of microcircuitry as well as projection studies. Few molecular tracers are able to do this, and those that can usually have a decreased signal in secondary neurons. Therefore, another benefit of viral tracing is the ability of viruses to self-replicate. As soon as the secondary neuron is infected, the virus begins multiplying and replicating. There is no loss of signal as the tracer propagates through the brain.

Drawbacksedit

Although some characteristics of viruses present a number of advantages in tracing, others present potential problems. As they propagate through the nervous system, the viral tracers infect neurons and ultimately destroy them. Therefore, the timing of tracer studies must be precise to allow adequate propagation before neural death occurs. The viruses can be not only harmful to neural tissue, but also harmful to the body at large. Therefore, it has been difficult to find viruses perfectly suited for the task. A virus used for tracing should ideally be just infectious enough to give good results, but not so much as to destroy neural tissue too quickly or pose unnecessary risks to those exposed. Another drawback is that viral neuronal tracing currently requires the additional step of attaching fluorescent antibodies to the viruses to visualise the path. In contrast, most molecular tracers are brightly colored and can be viewed with the naked eye, without additional modification.