HIV-Inhibiting Chemokines: Critical Host Factors in AIDS

ZRG-1 AARR-02 (01) 2 1R01AI48384-01A1
July 2000 GARZINO-DEMO, A
(and/or to develop assays for the analysis of) beta-chemokine production by
defined subpopulations of T cells rather than to only evaluate bulk peripheral
blood mononuclear cells (PBMCs); (d) that the experimental approach of Specific
Aim 2 may not lead to a definitive answer about the impact of beta-chemokine
levels on selection of (syncitia-inducing) viruses resistant to them. Amongst
these concerns, the current application has satisfactorily addressed (a) and
has provided a rationale for the continued use of bulk PBMCs (c). Explicit
responses have not been made to the concerns raised in (b) and (d). Given these
outstanding concerns, as well as others emphasized by re-review of the proposal
(below), it remains uncertain whether the methodologies and approach of this
study are likely to yield data which will be either interpretable and/or which
will meaningfully resolve the central issues that are raised.
Approach: Although this is an important set of questions, there are serious
problems with the design of this-study, the methods. used for data acquisition,
and the proposed approach towards interpretation of the data. Given the
hypothesis that higher levels of beta-chemokines should be associated with a
slower rate of disease progression, it is remarkable that no information is
provided about the clinical status of\these patients, their CD4 nadirs, and/or
whether they are responding to therapy with effective suppression of peripheral
viremia. From the standpoint of the proposal's underlying hypothesis, it would
seem that the 16 patients not on ARV therapy would be the most important to
follow; yet, no information is provided about the clinical and virologic
characteristics of this group. From the standpoint of any measure of disease
progression (be it by clinical symptoms, AIDS-defining events, or
virologic/immunologic criteria), it is not clear how these (poorly-defined)
groups will be followed: (a) most patients with HIV disease will be symptomatic
prior to the time that a clinical diagnosis of AIDS is made, but no information
is provided about how these symptoms will be assessed; (b) many patients on ARV
therapy, with or without AIDS, will fail such therapy by one criterion or
another (e.g., because of side effects, breakthrough resistance mutations,
etc), but we are not told how such instances of "failure" would be handled over
time; and, also, (c) if the therapy is effective, it would seem that this
selective pressure would confound any attempt to interpret the effects of CCR5
ligands on "disease progression." To further complicate matters, the definition
of "clinical AIDS" excludes those whose CD4 counts are 200 or less, removing
from consideration this important parameter of disease progression (although
the table on p. 42 would suggest that it will be nonetheless tracked). Since
the stated parameters of disease progression are so ill defined (and, indeed,
since it is probable that most of these patients will have well-advanced and/or
adequately-treated disease at the start of the study), it is not evident that
the underlying hypothesis of the proposal (viz-a-viz beta-chemokine production)
can possibly be addressed._______-___ _________ _
A major technical limitation of this proposal is that chemokine levels are
measured (usually by ELISA but sometimes by mRNA amplification) within
stimulated populations of peripheral blood mononuclear cells. The Investigator
lists (on pp. 34-35) five reasons why he has elected to "continue with whole
PBMC rather than to focus on various T cell subsets," but also notes (in
"future studies" on p. 43) that "the most logical question to examine is
whether chemokine levels change because of diminished expression capacity on a
per cell basis or whether there are differences in the representation of

chemokine-secreting subsets in the PBMC population." Put another way, chemokine