Once I complete all the studies I can do with cells, I
will have to do my next group of studies using animals. This is done to test
the safety in a living organism (cells can only tell me so much) and provides a
more real world study system. With no idea on the safety of my compounds, I can’t
do any work using humans, which is kind of a problem when studying HIV. As
stated in its’ name, HIV is the HUMAN immunodeficiency virus. This means that
HIV only infects humans. There are other types of immunodeficiency viruses
(like simian immunodeficiency virus), but using SIV in primates, or a hybrid
SIV/HIV in primates has not had good translation to work with HIV in humans,
because there are a lot of differences between SIV and HIV. This has been a
challenge many researchers have tried to solve, and recently success has been
observed with humanized mouse models of HIV.
Before I go further I should warn you that these mice
involve some very controversial stuff. First off, working with mice, which is
always a touchy area. To humanize a mouse you need to perform a minor surgery
on them and carefully monitor the mice post-surgery to make sure they don’t
develop infections or are in pain. And, to humanize the mouse you use human
fetal tissue, which can only be obtained from aborted fetuses that are donated
to research. If you have any issues with any of these things, I would suggest
you stop reading now.
Each humanized mouse has to be created individually. This
is a very lengthy process. You begin with a mouse that, through a combination
of genetic defects, does not have an immune system. There are several different
types of immunodeficient mice you can use for humanization. I will be using the
NOD/SCID/IL2rgamma-/- mouse. That is a fancy name for a mouse that has a severe
immune deficiency and is unable to make any functional immune cells. You have
to be very careful with these mice, because if they get any sort of infection
their body can’t fight it so they will likely die. Their water and food is
specially sterilized, their lungs are monitored for infection every other
month, and sentinel mice are used to monitor for any other infections.
When the mice are 8 weeks old they have a surgery to
implant human fetal liver and thymus under the kidney capsule. They also
receive an IV injection of human fetal stem cells (which can be derived from
the liver). The human stem cells will allow the development of all the human
immune cells, and the liver/thymus allows the T cells of the immune system to mature
properly. Because you use bone marrow (the stem cells), liver and thymus, these
mice are called BLT mice. Twelve weeks after the surgery you take blood samples
from the mice and check that all the immune cells are present. If so, the mice
can be used for infection with HIV.
The BLT mice have been shown to be susceptible to vaginal
infection with HIV, and the infection course is very similar to what is
observed in humans. Whenever I’ve presented my research I’ve been asked how
exactly you give a mouse HIV vaginally. The mouse is put under anesthesia, then
a small instrument is inserted into the vagina and HIV in saline is deposited.
The mouse is held in an inverted position so the saline doesn’t drip out. After
a few minutes, the mouse can be woken up from anesthesia. Blood samples can be
taken each week to determine HIV infection.
Today I am heading to a collaborators’ lab for 2 weeks to
receive the surgical training I need to be able to make BLT mice. These mice
will provide me with a lot of information about the “real world” uses of my
compounds. I have to do everything perfectly for this mouse experiment, because
it is really expensive. With the costs of my training trip, buying the mice,
housing the mice, buying reagents and materials, and equipment rental costs,
the 45-60 mouse cohort I can make from one set of donor organs will cost $20,000
or more.
Christina
No comments:
Post a Comment