How do disease-causing pathogens act inside our bodies? How do we study mechanisms of infection and immunity in various human diseases? Using human patients as lab rats is not possible, and thus researchers have come up with a better way of using actual lab rats to study infectious diseases.
Implanting Human Immune Responses in Mice
The efficacy of a vaccine on humans could be better studied if tested on an organism that resembled humans closely. It was in 2006 that mice were first ‘humanized’. Mice were implanted with human liver and thymus tissue, and hematopoietic stem cells. These mice were called BLT mice — Bone marrow, Liver and Thymus. The thymus and the liver are the centers of the immune system response; the thymus serves as the ‘training ground’ for immune T-cells. The implanted stem cells recognize the human immune tissues in the mice and lead to formation of human-like immune cells (called T-cells).
How Do Human Cells Respond to a Virus in a Mouse Body?
Though these mice contained human immune system cells, it was not known if the response of these cells inside a mouse body would mimic human responses. This would be essential to study human diseases. To study this, Boston researchers infected these mice with the virus HIV-1 and characterized the responses of these mice. They found that the immune system of these mice behaved in a way very similar to that of humans upon HIV infection. In addition, humans with a certain type of immune cells can recognize the virus better and live longer on infection. Now, mice with these cells also showed the same behaviour compared to other mice.
A large percentage of failures in human trials arise because of vaccines behave differently in the human body compared to other organisms. Using BLT mouse models that accurately reflect human immune system responses could weed out many of these false positives and speed up biomedical research.