Antiretroviral therapy started during the first
several days after infection limited dissemination of an HIV-like virus
throughout the body and establishment of cellular and tissue reservoirs in
monkeys, but it did not prevent the virus from coming back after stopping
treatment, according to research presented at the 21st Conference on
Retroviruses and Opportunistic Infections (CROI) earlier this month in Boston.
Afam Okoye and colleagues from the Vaccine and Gene Therapy Institute in
Florida and the Oregon Health and
Science University looked at the effect of early treatment on viral
reservoirs in rhesus macaque monkeys infected with SIV – a primate virus
similar to HIV – when antiretroviral therapy (ART) was started either prior to
peak viral replication, at or near the time of peak viral replication, or
during early chronic infection.
From the very earliest stages of infection, HIV replicates and 'seeds'
itself in cellular reservoirs including long-lived memory T-cells as well as
anatomical reservoirs such as the brain and gut. As part of the research
towards a cure for HIV, researchers have explored whether antiretroviral drugs
started very soon after infection can limit this process.
A group of people living with HIV in France, known as the VISCONTI
cohort, appear to be controlling HIV on their own after interrupting ART that
was started during very early infection, and a baby started on treatment within
about 30 hours after birth shows no
signs of ongoing infection despite being off ART for 2 years.
These and other cases suggest that reservoirs established early during
acute infection – prior to peak viral replication – "may be quantitatively
and qualitatively different from those established later in chronic infection
and perhaps be more amenable to cure," the researchers noted as
Previous research in monkeys indicated that the size of the SIV
reservoir in peripheral blood mononuclear cells (PBMCs) and tissues increases
significantly between day 7 and day 10 after infection, and that the viral
reservoir seeded during early acute infection is largely made up of CD4 memory
T-cells, including central, transitional and effector memory cells.
In this study, monkeys were started on multidrug therapy at day 7 (n=2),
day 10 (n=2) or day 42 (n=18) after being intravenously exposed to SIV. ART
consisted of tenofovir and FTC (the drugs in Truvada), the integrase inhibitor dolutegravir (Tivicay) and ritonavir-boosted darunavir
The researchers measured SIV viral load in blood plasma, cell-associated
virus in PBMCs, and SIV in bone marrow, small intestine mucosa or gut tissue
and lymph node biopsy samples at various time points.
ART initiation prior to peak viral replication
led to lower peak plasma viral load and earlier viral suppression.
In the two monkeys treated from day 7, plasma viral load continued to
rise after ART initiation, peaked by day 12, then declined to an undetectable
level (<30 copies/ml) after six weeks on ART. In the two macaques started on
treatment at day 10, plasma viral load peaked on day 12 and did not become
undetectable until 18 weeks on ART.
Among the 18 monkeys treated later, plasma viral load peaked between 12
and 14 days, and some animals did not achieve complete viral suppression even
after 32 weeks of treatment.
SIV DNA (viral genetic material) in PBMCs and
tissues increased exponentially between 7 to 10 days after infection. However,
early ART decreased SIV DNA levels in circulating lymphocytes and all tested tissues. After 32 weeks, mean
SIV DNA levels in PBMCs were 2.5 log for those started on ART at day 7, 3.5 log
for those started at day 10 and 4.4 log for those started at day 42.
was undetectable by co-culture in all monkeys started on ART at day 7 or day
10, but detected in all those started at day 42. However,
even in monkeys treated early, viral rebound occurred soon after stopping ART,
indicating that replication-competent virus is still present. In addition,
transferring lymph nodes from infected monkeys treated at day 7 to
treatment-naive animals resulted in productive infection, again showing that
infectious virus is present.
"Early ART, when initiated prior to peak virus
replication, limits systemic virus dissemination and seeding of the reservoir
in peripheral and extra-lymphoid mucosal compartments," the researchers
"A delay as short as three days during the
'hyperacute' phase can result in 1-2 logs higher tissue-based reservoir size,
once therapy is started and maintained," they continued. "Reservoirs
established during acute infection are capable of inducing rapid viremia in
naive animals and viral rebound following ART cessation."
"Aggressive monitoring for acute infection with
immediate introduction of ART could profoundly influence treatment outcomes and enhance viral
eradication strategies," they suggested.
Speaking from the audience, Deborah Persaud from Johns Hopkins – who at
last year's CROI first reported on the apparently functionally cured
Mississippi baby and this year described another baby in Long Beach who also
appears free of HIV, though this child remains on ART – suggested that starting
treatment seven days after exposure is perhaps already too late. "This is
relevant to perinatal infection, to not just minimize but block establishment
of reservoirs," she said.
At a press conference following his presentation, Okoye acknowledged
that to achieve the best results, "we may have to treat within 36