The very word “micro-bicides” can give the reader pause, but the term refers to agents composed of microorganisms (invisible to the eye) that are used to kill unwanted pests, like viruses invading human bodies. HIV is one such virus badly in need of a microbicide to block its spread.
A microbicide comes in the form of a gel like Vaseline and one form that has been developed to block HIV is applied to a woman’s vaginal area.
Researchers testing this vaginal microbicide say it is based on a new type of anti-HIV drug, and in their tests they used monkeys. This is standard procedure – test first on monkey, which are animals biologically similar in many ways to humans – and if results are promising, proceed to tests on human beings.
The anti-HIV microbicide gel used on monkeys was found to provide the animals with “significant protection” against infection with a virus similar to HIV, according to a study reported at the International Microbicides Conference in Pittsburgh.
The gel used in the study is the first to contain what is called an “integrase inhibitor,” one of the latest additions to the arsenal of drugs for the treatment of HIV, but just one of the many compounds or drug combinations that researchers are hoping will be useful for HIV prevention.
Microbicides are substances designed to prevent the sexual transmission of HIV when applied to the body (topically) on the inside of vagina, whereas oral PrEP is an approach involving the use of ARVs drugs by HIV-negative people to reduce their risk of acquiring HIV.
The monkey trials were conducted by the U.S. Centres for Disease Control and Prevention. The study is the first of a gel with an integrase inhibitor, and these results support further evaluation of integrase inhibitors to examine whether they can be used to prevent transmission of HIV in uninfected individuals, in addition to their current use as treatment for HIV-infected individuals.
According to the study, “Integrase inhibitors, the latest weapon in the HIV treatment armamentarium, stop HIV from incorporating its genetic information into the DNA of an infected T cell, essentially heading off HIV’s master plan to hijack all future generations of cells. They are intended to be used in combination with other ARVs that target different steps in the HIV life cycle. Studies have found that integrase inhibitors can suppress a virus that is resistant to some of these other ARVs.”
During the study the gel was applied to three female monkeys twice a week for seven weeks. Thirty minutes after each gel application, the animals were exposed to HIV, for a total of 14 exposures.
A fourth monkey received a placebo gel in the same manner. A placebo is a “fake” drug that has no active ingredients, and might as well be water, but it is used to see how “doing nothing” compares to the effects if any of the experimental drug.
Two of the three monkeys that received the active gel remained uninfected after seven weeks of being exposed to HIV. The third monkey, however, became infected halfway through the process, after seven exposures.
Meanwhile, the monkey that received a placebo gel became infected after the third exposure.
“Importantly, the animal that became infected while using the active gel had no evidence of drug resistant virus even after continuing the gel regimen for an additional 15 weeks. This is significant because one of the concerns with ARV-containing gels is that the inadvertent use of these gels in someone who is HIV-infected could allow the virus to become resistant and limit treatment options in the future,” the report said.
So far, so good, but as the researchers noted; “While the results are promising, additional studies will be needed before deciding whether to advance this particular vaginal gel to trials in humans.”
Other microbicides are also being tested. One is a drug named L’644, which may prevent HIV from fusing to a healthy cell in order to infect it, was found in laboratory tests to be more effective than drugs in the same class of antiretroviral drugs called fusion inhibitors. Fusion inhibitors work by blocking the interaction between a small protein on the HIV virus and proteins on the host cell, leaving the virus without a way to fasten itself to the host cell.
Researchers from St. George’s, University of London, in the U.K., in collaboration with the International Partnership for Microbicides, want to examine the potential of L’644 for possible development as a microbicide for preventing the sexual transmission of HIV.
The way HIV takes over a body is by latching onto a healthy cell, copying its genetic material, and using the cell to make new versions of HIV that will then spread out and infect other cells. An experimental drug called darunavir attacks an enzyme in HIV, without which the virus cannot copy a healthy cell’s genetic material.
According to researchers, “Darunavir was one of three (medicines) tested for their ability to prevent infection of T cells, HIV’s primary target. Darunavir and the two others, ritonovir and lopinavir, also were tested with both cell types together as a model of infection of T cells. That is because dendritic cells are used by HIV for the free ride they can provide to reach T cells.” The researchers measured effectiveness of each drug by looking to see whether or not they prevented new virus particles from being made. All three drugs were able to inhibit the replication of HIV in both cell types alone as well as in the two-cell model of infection, with darunavir outperforming the other two. But the combination of darunavir and dapivirine proved most effective and showed the best promise for further development as a microbicide.
Fuente: Swazi Observer