Two anti-HIV antibodies together show positive results
In an interesting study, the immune system of monkeys was found
capable of controlling HIV-like virus (Simian-Human Immunodeficiency Virus or
SHIV) when treatment with a combination of two anti-HIV antibodies was started
three days after infection. The immune system of the animals was found to
control the virus even after the anti-HIV antibodies were no longer present in
the monkeys.
In a paper titled ‘Early antibody therapy can induce
long-lasting immunity to SHIV’ published on March 13 in the journal Nature , researchers from the National
Institutes of Health and other institutes infected 13 macaque monkeys with the
SHIV virus. Unlike earlier studies where intervention began late, the
researchers started treating the monkeys with two broadly neutralising HIV
antibodies from the third day of infection. The monkeys were infused with the
two drugs three times over a two-week period.
Compared with controls, six monkeys were able to suppress the
virus for 56 days to even six months; in one monkey, the virus was below
detectable level for 150 days. Once the antibodies level dropped to a “very
low” in the animals, the virus resurfaced. The time taken to rebound was
directly related to the concentration of the neutralising antibodies in the
plasma.
Five to 22 months after the virus resurfaced, the immune system
of the six monkeys spontaneously regained control of the virus and brought it
down to undetectable levels for another five to 13 months. Four other monkeys
could never fully regain complete control of the virus, but the viral load was
at a “very low level” for more than two years. Of the 13 monkeys studied, 10
were able to benefit from two neutralising antibodies administered. A
particular kind of immune cells called CD8+ T cells were found to be higher in all
the animals that were infected with the SHIV virus. To ascertain if CD8+ T
cells were responsible for mediating sustained suppression of virus
replication, the researchers purposely depleted the CD8+ T cells in the six
monkeys. What followed was a sharp increase in the viral load in all the
animals. This helped the researchers conclude that the CD8+ T cells controlled
the virus multiplication following administration of the neutralising
antibodies.
Though SHIV infection in macaque monkeys differs from HIV-1
infection in humans, the researchers suggest that immunotherapy should be
explored to control the spread of virus, contain the damage to CD8+ T cells,
mobilise a robust immune response, and control HIV infection in humans.
Source:THE HINDU,14th March,2017
