Antibodies treatment can clear infection for SHIV-exposed infant macaques

22nd March 2016 (Last Updated March 22nd, 2016 18:30)

Scientists at the Oregon National Primate Research Centre have revealed that infant rhesus macaques exposed to an HIV-like virus when treated with antibodies can clear the infection.

The Oregon National Primate Research Centre has revealed that infant rhesus macaques exposed to an HIV-like virus can clear the infection when treated with antibodies.

According to a study, infants exposed to SHIV, a chimeric simian virus bearing the HIV envelope protein, have been completely free of the virus when treated with antibodies within 24 hours of the exposure.

The research, which is a key development in the HIV scientific community, has been published in Nature Medicine.

Nonhuman primates infected with SHIV can transfer the virus to their young through milk feeding.

"We were not convinced an antibody treatment could completely clear the virus after exposure. We were delighted to see this result."

Similarly, HIV can be transmitted from a mother to her child through breastfeeding as well as during childbirth.

Since 1994, the rate of HIV transmission from mother to child has reduced from 25% to less than 2% as a result of measures such as Cesarean section delivery, antiretroviral therapy (ART), and formula feeding rather than breastfeeding.

In spite of this significant reduction, nearly 200,000 children are infected with the virus each year worldwide.

The rate of HIV transmission is higher in developing countries where ART is not easily available.

National Primate Research Centre director Nancy Haigwood and colleagues applied the anti-HIV-1 human neutralising monoclonal antibodies (NmAb) subcutaneously on the first, fourth, seventh and tenth day the macaques were orally exposed to SHIV.

On the first day, the SHIV virus was found in multiple body tissues in macaques that did not receive antibody treatment.

The researchers observed the immediate result of a single dose of antibodies at the beginning of the infection, with a marked difference between treated and non-treated macaques.

An early short-term treatment of antibodies significantly cleared the virus from the infected body by day 14.

Haigwood said: "We knew going into this study that HIV infection spreads very quickly in human infants during mother-to-child transmission.

"So we knew that we had to treat the infant rhesus macaques quickly but we were not convinced an antibody treatment could completely clear the virus after exposure. We were delighted to see this result."

In humans, HIV usually spreads quickly to local draining lymph nodes before spreading throughout the entire body of the infected person after a week of exposure.

Unlike with humans, virus replication is observed in lymphatic tissues 24 hours after exposure to the virus and is not locally restricted.

According to the study, antibodies that are administered subcutaneously are quickly distributed to blood and tissues, and maintain neutralising activity at various sites.

It also reveals that antibodies can effectively remove the virus, which is a different mechanism than that of ART, which is a combination of a range of antiretroviral medicines used to reduce the rate at which HIV replicates itself in the body.

The researchers recommended that human babies should be treated with ART during the few days after delivery, the last month of gestation and during breastfeeding time frames.

Clinical trial in which HIV-infected infants are treated with antibodies are currently being carried out in the US and South Africa.

The trials followed a Phase I clinical trial that revealed the antibodies to be safe and well-tolerated in HIV-negative adults.