Sperm
Cells, in Addition to Semen, May Play a Role in Sexual
Transmission of HIV
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| SUMMARY:
It is well known that semen can transmit
HIV during
sexual activity, but sperm cells themselves
appear able to capture and transport the
virus to vulnerable dendritic cells, according
to study results published in the November
23, 2009 Journal of Experimental Medicine.
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By
Liz Highleyman
Semen,
which is the major route of HIV transmission worldwide,
contains 3 major sources of infectious virus: free
virions (virus particles), infected leukocytes (white
blood cells), and spermatozoa-associated virions,
Ana Ceballos from the Universidad de Buenos Aires
in Argentina and colleagues noted as background.
The
investigators focused on the interaction of HIV-1
with human spermatozoa (individual sperm cells) and
dendritic cells, a type of immune system cell that
captures invading pathogens and presents them for
recognition by T-cells.
The
authors reported that heparan sulfate is expressed
on spermatozoa and plays an important role in enabling
the HIV envelope to attach to the sperm cell surface.
This spermatozoa-attached virus can then be efficiently
transmitted to dendritic cells, macrophages, and T-cells.
CD4 and DC-SIGN receptors on dendritic cells were
required for transmission, suggesting that the cells
capture the virus by binding to sperm, rather than
by engulfing or ingesting them.
Interaction
of spermatozoa with dendritic cells not only leads
to the transmission of HIV and the internalization
of the spermatozoa, they continued, but also results
in the maturation of dendritic cells and production
of interleukin 10 (IL-10), a cytokine that plays a
role in suppressing inflammation, which might help
the virus to spread.
The
researchers determined that the binding of HIV to
spermatozoa and the subsequent transmission of virus
to dendritic cells was strongly enhanced at low (acidic)
extracellular pH values similar to those found in
the vagina after sexual intercourse.
"Our
observations support the notion that far from being
a passive carrier, spermatozoa acting in concert with
dendritic cells might affect the early course of sexual
transmission of HIV-1 infection," the investigators
concluded.
Centro
Nacional de Referencia para el SIDA, Facultad de Medicina,
Universidad de Buenos Aires, Buenos Aires, Argentina;
Instituto de Investigaciones Hematológicas,
Academia Nacional de Medicina, Buenos Aires, Argentina;
Instituto Médico Halitus, Buenos Aires, Argentina;
Instituto de Biología y Medicina Experimental,
Buenos Aires, Argentina; Institut National de la Sante
et de la Recherche Medicale, Immunite et Cancer, Institut
Curie, Paris, France.
12/15/09
Reference
A
Ceballos, F Remes Lenicov, J Sabatté, and others.
Spermatozoa capture HIV-1 through heparan sulfate
and efficiently transmit the virus to dendritic cells.
Journal of Experimental Medicine 206(12): 2717-2733
(Abstract).
November 23, 2009.
