Summary
In July 1982, the occurrence of three cases of acquired immunodeficiency syndrome
(AIDS) in men with haemophilia was an immediate signal to Oscar Ratnoff that AIDS
was transmissible through blood products. Work that he led provided important and
clear indication that the AIDS agent was transmissible through pooled plasma products
and had rapidly infected many men who had haemophilia. Before the blood supply was
protected, the risk for infection in haemophilia was related directly to the intensity
of therapy with pooled anti-haemophilic factor concentrates. Studies performed among
the small proportion of haemophiliacs who remained uninfected despite heavy exposure
to these plasma products revealed that the rare protective genotype – homozygosity
for the 32 base pair deletion in the CCR5 gene was heavily concentrated in this population.
Among those who did not have this protective genotype, a state of diminished immune
activation distinguished these high risk uninfected haemophiliacs from haemophiliacs
who later acquired human immunodeficiency virus (HIV) infection and from healthy uninfected
controls. Immune activation state may not only predict risk for HIV acquisition but
also appears to be an important predictor and likely determinant of HIV disease progression.
The potential drivers of immune activation in chronic HIV infection include HIV itself,
other co-infecting pathogens, homeostatic responses to cytopenia as well as the recently
recognised phenomenon of translocation of microbial products across a damaged gut
mucosal surface. This latter process is particularly compelling as clinical studies
have shown a good relationship between indices of microbial translocation and markers
of both immune activation and T cell homeostasis in chronic HIV infection. More recently,
we have also found evidence that these microbial products also may drive a heightened
tendency to thrombus formation in HIV infection via induction of monocyte tissue factor
expression. Thus systemic exposure to microbial elements that are translocated through
a gut mucosa damaged in the first few weeks of HIV infection may contribute to the
pathogenesis of both immune deficiency and the heightened risk for vascular events
that have been noted in persons with HIV infection.
Keywords
Infectious diseases - immunity - viral infection