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are rarely seen in adult PI, were also observed in these children, although not as
frequently as those involving CD8
cells (Soudeyns et al., 2000b) ( Fig. 7.1).
The functional signi®cance of these CD4
T-cell expansions has not been elu-
cidated. However, in stark contrast with CD8
expansions, these cells exhibited
a high level of polyclonality and an almost total lack of conservation in the
CDR3 layout. Because CD4
T-cell responses are markedly more polyclonal
than those involving CD8
T cells (Maini et al., 1999), these observations are
nevertheless consistent with the possible involvement of these expanded sub-
sets in ongoing antigen-speci®c T-helper responses (Soudeyns et al., 2000a).
Alternatively, the apparent polyclonality might simply re¯ect continual HIV-
mediated depletion and remodelling of the CD4
T-cell compartment.
Effects of Antiretroviral Therapy
The introduction of highly active antiretroviral therapy ( HAART ) has been
credited with the recently recorded declines in the incidence of HIV-related
morbidity and mortality ( Palella et al., 1998). HAART been shown to promote
a variable but signi®cant recovery of immune responsiveness in treated patients
(Autran et al., 1997; Fleury et al., 1998, and references therein). Paradoxically,
the intensity of the CTL response and the frequency of HIV-speci®c Th and
CTLs have been shown to decline following prolonged periods of viral sup-
pression (Gray et al., 1999; Ogg et al., 1999; Pitcher et al., 1999). This was
presumed to represent an indirect result of the e¨ective suppression of viral
replication and concomitant reduction in the amounts of circulating HIV anti-
gens available to prime and maintain high-level immune responses. At the level
of the TCR repertoire, this e¨ect is translated by a signi®cant decline in the
frequency and magnitude of perturbations in the CD8
T-cell subset (Connors
et al., 1997; Gorochov et al., 1998). In contrast, the rate of normalization of the
CD4
T-cell repertoire is variable following introduction of therapy, re¯ecting
g
ÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐÐ
Figure 7.1. Longitudinal analysis of the TCR b chain repertoire in CD4
and CD8
T cells from
a HIV-negative infant born to an HIV-infected mother. The child was followed from birth until 6
months of age. Vertical bars correspond to the relative levels of representation of speci®c TCRBV
families in samples of peripheral blood mononuclear cells (PBMC). Direct staining of PBMCs
was performed using ¯uorescein isothiocyanate (FITC)-labeled monoclonal antibodies (mAbs)
speci®c for TCRBV2S1 (E2.2E7.2), TCRBV3S1 (LE89), TCRBV5S2 (36213), TCRBV8 (56C5),
TCRBV13S1 (IMMU222), TCRBV13S6 (JU74.3), TCRBV17 (E17.5F3.15.13), TCRBV20S1
(ELL1.4), TCRBV21S3 (IG125), and TCRBV22 (IMMU546), obtained from Immunotech
(Marseille, France). FITC-labeled anti-TCRBV6S7 (OT145) and anti-TCRBV12 (S511) were ob-
tained from Endogen (Woburn, MA). Unlabeled mAbs used in indirect staining included anti-
TCRBV5S2-3 (MH3-2), anti-TCRBV9 (MKB1), anti-TCRBV13S2 (13.2), and anti-TCRBV23S1
(HUT78). In these cases, FITC-conjugated goat anti-mouse IgG (Life Technologies, Burlington,
Ontario Canada) was used as a secondary antibody. Cells were counterstained with phycoerythrin
(PE)-conjugated anti-CD4 (top panel ) or anti-CD8 mAbs (bottom panel ) (Becton-Dickinson,
Mountain View, CA). Analysis was performed on 10,000 events, gated according to forward and
side-scatter, on a FACScan driven by the CellQuest software package (Becton-Dickinson). Results
are expressed as percentage of cells in the lymphocyte gate.
