When a Cuban strain goes up a gear

CRF19 is the result of the genetic recombination of two other strains of HIV. And, of course, considering its virulence, it is characterised by a particularly high replication speed.  What’s even more surprising is that CRF19 causes a rapid deterioration of the immune status particularly in patients with a high blood concentration of a chemokine known as RANTES. “And yet, RANTES, a product of the inflammation, naturally binds to mucous membrane T lymphocyte receptors which are precisely those used by HIV”, Michel Moutschen explains. “In these patients, since RANTES is already occupying the receptors essential for the replication of HIV in mucous membrane T lymphocytes, considerable selective pressure occurs allowing the short-term use of the receptors of the other T lymphocytes in the body”, the scientist continues. The reason why these Cuban patients show high levels of RANTES in the blood remains unknown. However, according to scientists, these people may have been subject to a systemic inflammation which is itself linked to the presence of CRF19 in their body. “The mere presence of the HIV strain may have stimulated the inflammation and thus provoked the production of RANTES. This scenario, which is counterproductive for the virus in the beginning, ultimately opens the way for it to infect the whole body rapidly. It's a sort of vicious circle”, Michel Moutschen sums up.

While cases of the disease’s rapid progression have been observed in other parts of the world, the specialists are generally unaware of the reasons behind this progression. It can be linked to the viral strain and/or the host. “The genetics of individuals play a major role in the way the virus progresses in the body. According to their genetic make-up, an individual may be more vulnerable or more resistant to HIV. The virus’ strain isn’t the only factor to enter into the equation”, Michel Moutschen indicates. “For the first time, the present study has enabled us to relate virological properties to a rapid clinical progression of the disease. Out of the 50 Cuban patients studied presenting a rapid progression of the HIV infection, ten of them were infected by the CRF19 strain. This is statistically highly significant and sufficient to attribute particular properties to this strain. However, the 40 other patients show that other factors must be present”.

Early treatment of the infection to stall the virus

According to Michel Moutschen, the main message to remember following the results of this study is that anyone infected by HIV must be treated as soon as possible. “Currently, in Belgium and in many other countries, we don’t start treating patients until their concentration of CD4 T lymphocytes falls below a certain threshold. Before that, the treatment isn’t reimbursed”, the professor explains. “This decision is based on the fact that we presume that the speed of progression to AIDS is known and constant. So we wait a while, perhaps to make savings or to prevent the patient from getting tired of taking their medication...”. In Cuba, following the conclusions of the present study, the authorities have decided to significantly raise the threshold determining when HIV-infected patients should be treated.

The Cuban example proves that things can deteriorate much faster than previously thought and that new more aggressive strains can appear at any time. Hence the interest of providing treatment as soon as the infection is detected. “The good news is that the CRF19 strain identified in Cuban patients isn’t, in principle, resistant to the antiretroviral drugs used to slow down HIV infection”, Michel Moutschen adds. HIV strains mutate and always try to find new target cells. It is therefore vital to keep an eye on them because they may still have some surprises in store for us. All the more so since the majority of knowledge acquired until now on HIV particularly concerns subtype B, which is found in Europe, rather than the strains present on the other continents.