Researchers from the schools of
Public Health and
Medicine used positron emission tomography scans to
identify sites of replicating HIV in the lymphatic system
of people recently infected with the virus. PET scan
imaging is typically used to detect tumors. The researchers
believe PET scans could lead to greater understanding of
HIV disease and new methods for treating the infection.
Their findings are published in the Sept. 20 edition of
According to the study, the PET scans recorded
activation of the lymph nodes, which are involved in the
body's immune response. Activation was most notable in
lymph nodes in upper torso and neck areas of the body among
participants recently infected with HIV. Nodes in the lower
torso were involved to a lesser extent. Participants who
were infected with HIV for a longer period and remained
asymptomatic with low viral loads also had lymph node
activation in the neck, upper torso and pelvic areas. The
Johns Hopkins researchers observed a tight correlation
between the viral replication and the lymph node activity
on the PET signal.
Lead author Sujatha Iyengar and senior investigator
David Schwartz propose that PET scans could be used to
locate the specific nodes where HIV is replicating and
remove them or target them with radiation.
"Although many systemic sites from which latent virus
could be reactivated would be left, reactivation might not
occur for months or years after removal of the active
nodes, thereby allowing extended interruption of treatment
for the disease," said Schwartz, who is an associate
professor with the School of Public Health's
Molecular Microbiology and Immunology. "Despite the
systemic nature of HIV infection, the sites of viral
replication appear remarkably restricted to limited
anatomic locations at any given time. This suggests micro
environmental niche selection in true Darwinian fashion."
Iyengar, a research associate with Public Health's
Department of Molecular Microbiology and Immunology, said,
"Equally important for the future of this technology is the
observation that immune responses to vaccines can be
anatomically localized and measured in normal individuals.
This could be invaluable in the evaluation of new vaccines
and routes of administration."
For the study, the researchers used PET scans to
examine 23 HIV-positive people, 12 of whom had recently
been infected and 11 of whom had been infected for a long
period of time. None of the participants had any signs of
disease or illness. The researchers also scanned eight
noninfected individuals as a control group. They were given
influenza vaccine to stimulate lymph node activation.
The study, "Anatomical loci of HIV-associated immune
activation and association of viraemia," was written by
Iyengar, Bennett Chin, Joseph B. Margolick, Beulah P.
Sabundayo and Schwartz.
Funding for the study was provided by grants from the
National Institutes of Health, the Center for AIDS Research
and the Alternatives Research Development Fund.