Abstract Book Vol. 2 [International Conference on AIDS (14th: 2002: Barcelona, Spain)]

12 Abstracts WePeA5736-WePeA5739

XIV International AIDS Conference

was strongly correlated with fractional replacement rates for pooled cell subset
data (r2=0.407, p<0.001, n=50). As with Ki67 expression, labeling with deuterium
showed no change in production of CD8+ T cell subsets.
Conclusions: TCH failure was longitudinally associated with decreased numbers
of proliferating naive CD4+ T cells and recent thymic emigrants. Among CD8+ T
cells, the number of proliferating cells did not increase after TCH failure to compensate for cell loss. These data suggest that TCH failure is due, at least in part,
to insufficient T cell production and proliferation.
Presenting author: pratip chattopadhyay, 615 north wolfe street, baltimore, md -
21205, room 4613, hygiene, United States, Tel.: [phone], Fax: [phone], E-mail: [email protected]
WePeA5736 The depletion of CD4 cells by HIV is explained by a
two stage mechanism: regulated cell activation
followed by cell infection
C. Fraser1, N.M. Ferguson1, C.A. Donnelly', R. Coutinho2, F. Miedema3,
J. Goudsmit4, J. Lange4, R.M. Anderson1, F de Wolf4. 1Imperial College
Faculty of Medicine, Department of Infectious Disease Epidemiology, Imperial
College Faculty of Medicine, St Marys Campus, Norfolk Place, London W2 1PG,
United Kingdom; 2Municipal Health Service, Amsterdam, The Netherlands;
3Sanquin, Division CLB, Amsterdam, The Netherlands; 4Academic Medical
Centre, Amsterdam, The Netherlands
Background The mechanism by which HIV infection results in the depletion of
CD4+ T cells remains controversial. We present and test a novel mathematical
model of CD4 cell depletion that relates current knowledge of viral dynamics to
the observed trends in HIV pathogenesis. We test the hypothesis that the dominant route of CD4 cell death is by a two-stage process of regulated cell activation
followed by infection rather than by direct infection of predominantly resting cells.
Methods The model is fitted to data from 155 patients in the Amsterdam Seroconverters Cohort with documented seroconversion and followed regularly since
1983 using a Markov chain Monte Carlo algorithm.
Results The model fit the patient data well in both pre- and post-antiviral treatment phases. We estimate that 89% [87%-92%] (maximum likelihood and 95%
credibility interval) of total CD4 cell destruction occurs via the two-stage mechanism (activation-infection), with the remaining fraction arising from direct infection. This latter fraction increases from 0.56% [0.43%-0.71%] when log10 viral
load (LVL) per mL peripheral blood (PB) is 1 to 95% [94%-97%] when LVL is 7.
The LVL at which both mechanisms contribute equally is 5.7 [5.6-5.8]. We also
estimate 0.08% [0.07%-0.09%] cells are replaced by thymic emigrants daily, 0.9
[0.6-1.4] CD4 cells per day per kL PB are sensitised to infection by activation. The
infection rate of depends sigmoidally on LVL with threshold value 3.4 [3.3-3.6] and
the rate of direct infection is 1.8 [1.4-2.1] x109 per virion per cell per day.
Conclusions We have demonstrated that our model of cell destruction can explain the long-term trends of CD4 cell destruction and reconstitution in HIV pathogenesis and treatment. We have found that the dominant route of destruction
during the asymptomatic period is cell activation prior to infection, though direct
infection also plays a role in hastening disease progression.
Presenting author: Christophe Fraser, Department of Infectious Disease Epidemiology, Imperial College Faculty of Medicine, St Mary's Campus, Norfolk
Place, London W2 1PG, United Kingdom, Tel.: [phone], Fax: +44 20
7402 2150, E-mail: [email protected]
WePeA5737 CD40-activated macrophages become highly
susceptible to X4 strains of human
immunodeficiency virus Type 1
Y. Bakril, A. Mannioui1, F. Sanchez2, L. Ylisastigui 2, J.C. Gluckman2,
A. Beniouad'. 'Faculte des sciences, Rabat, Morocco; 21NSERM EPI 0013,
Paris, France
Background: Macrophages are cells of immune system that are part of the viral
reservoir persistence of HIV-1 in vivo. Even though macrophages express CD4,
CCR5, and CXCR4, they allow replication of R5 and dual-tropic R5X4 but not X4
HIV-1 strains. Activating cells of the immune system may stimulate HIV-1 replication and contribute to select pathogenic variants in vivo.
Methods: We examined the possible effect of a major pathway of immune activation, CD40 interaction with its ligand (CD40L), on the susceptibility of monocytederived macrophages (MDMs) to various HIV-1 strains. MDMs were exposed to
HIV-1 Bal, HIV-1Lai or X4 primary isolates in the presence or not of CD40LT
and/or kinase inhibitors or SDF-1. Viral p24 in cell-free supernatants was assessed by ELISA. HIV-DNA was detected by nested PCR, ERK1/ERK2 activation
was determined by immunoblot analysis and cytokines in culture supernatants
were measured by ELISA.
Results: Stimulation of MDMs with CD40L led to reduced replication of R5 HIV1Ba-L, whereas this strongly enhanced the replication of X4 HIV-1Lai as well as
of X4 primary isolates, and this was associated with strong cytopathic effects.

The replication of X4 strains that was induced by CD40 ligation was inhibited by
stromal cell-derived factor 1, an indication of the restricted usage of CXCR4 as
virus coreceptor in this case. CD40L induced the activation of mitogen-activated
protein kinases ERK1/ERK2 and stimulated MDM to secrete RANTES (regulated
upon activation, normal T-cell expressed and secreted), macrophage inflammatory protein la, (MIP-l1a), MIP-1b, interleukin 6 (IL-6), IL-lb and tumor necrosis
factor a.

Conclusion: From this data, it may be hypothesized that activated macrophages
represent a favorable environment for the replication of classically T lymphocytetropic X4 variants and, thus, may contribute significantly to the selection of such
variants at late stages of clinical HIV-1 infection.
Presenting author: Abdelaziz Benjouad, Departement de Biologie, Lab.
Biochimie-Immunologie, Faculte des sciences Rabat, Avenue Ibn Batouta, Morocco, Tel.: [phone], Fax: [phone], E-mail: [email protected].
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WePeA5738 Activation of monocytes by desialylation promotes
infection with R5 HIV-1 BaL
N.M. Stamatos1, J.B. Mitchell2, S. Curreli2, D. Zella2, A.S. Cross3. 1Institute of
Human Virology and Div of Infectious Diseases/Univ of Maryland Med. Ctr.,
Baltimore, MD, United States; 2Institute of Human Virology/Univ of Maryland,
Baltimore, United States; 3Div of Infectious Diseases/Univ of Maryland Med.
Ctr., Baltimore, United States
Background: Differentiation of peripheral blood monocytes into macrophages or
immature dendritic cells establishes a permissive state for growth of HIV-1.
Monocytes express increased endogenous sialidase activity as they differentiate.
We determined whether desialylation of glycoconjugates on the surface of undifferentiated monocytes enhanced their permissivity for infection with R5 HIV-1
BaL.
Methods: Peripheral blood mononuclear cells (PBMCs) or purified monocytes
were desialylated with microbial neuraminidase (NANase) prior to exposure to
R5 HIV-1 BaL. Infected cells were maintained in culture in RPMI medium/10%
FCS without exogenous growth factors to minimize cell activation. Viral growth
was determined by the amount of p24 Ag released into culture medium.
NANase-treated monocytes were also evaluated for changes in activation of extracellular signal-regulated kinase 1/2 (ERK 1/2), cytokine production and surface
expression of HLA-DR.
Results: Desialylation of PBMCs with NANase prior to exposure to HIV-1 BaL
resulted in a large increase in production of viral p24 Ag compared to mocktreated cells. Enhanced viral growth occurred predominantly in NANase-treated
monocytes as cells were maintained in medium without exogenous IL-2. Infection
of purified monocytes with HIV-1 BaL was also enhanced following desialylation
when infected monocytes were subsequently cocultured with autologous lymphocytes. Desialylation of purified monocytes with NANase activated MAP kinase
ERK 1/2 and led to increased production of proinflammatory cytokines IL-6, TNFu and IL-1 and to enhanced expression of surface activation marker HLA-DR.
Neither enhancement in viral growth nor increased activation of monocytes was
detected when NANase was heat-inactivated or specifically inhibited with 2,3 -dehydro-2-desoxy-N-acetyl-neuraminic acid prior to use.
Conclusions: Undifferentiated monocytes were activated by desialylation and
became permissive for infection with HIV-1.
Presenting author: Nicholas Stamatos, Institute of Human Virology, 725 West
Lombard Street, Baltimore Maryland 21201, United States, Tel.: [phone],
Fax: [phone], E-mail: [email protected]
WePeA5739 The distribution of HIV-1 target cells and keratin in
the human penis
S.G. McCoombe1, RP.U. Cameron2, R.V. Short3. 1Dept. of Zoology/Dept of
Microbiology and Immunology, University of Melbourne, Parkville, Vic., Australia;
2Dept. of Microbiology and Immunology, University of Melbourne; 3Dept of
Obstetrics and Gynaecology, University of Melbourne, Melbourne, Australia
Background: Little is known about where HIV-1 enters the human penis, but
the protective effect of male circumcision suggests that the foreskin is involved.
Langerhans cells that contain specific HIV-1 receptors are located in the foreskin, glans penis and frenulum, but an overlying layer of keratin could prevent
viral contact with these receptors. We have therefore studied the distribution of
Langerhans cells, dendritic cells and T-cells, and the relative thickness of the keratin layer, in the glans penis and foreskin to determine how HIV-1 could enter the
penis.
Methods: Uncircumcised penises were obtained from formalin-fixed cadavers,
and a specific histochemical stain was used to measure keratin thickness on
the foreskin and glans penis. Langerhans cell, dendritic cell and T-cell density,
location and morphology were studied using varying immunohistochemical techniques on fresh-frozen penile sections obtained following routine adult circumcision or at autopsy.
Results: The mean thickness of the keratin layer on the inner surface of the foreskin and the frenulum was significantly less than that on the outer foreskin or the
glans penis. Langerhans cells in the epithelium of the inner foreskin and frenulum
were closer to the surface than in the epithelium of the outer foreskin.
Conclusions: The most important route for HIV-1 entry into the penis of uncircumcised men is probably via superficial Langerhans cells on the inner aspect

of the foreskin and the frenulum where the keratin layer is the thinnest. The protective effect of male circumcision can be best explained by the removal of many
readily accessible HIV-1 receptor sites in the foreskin.
Presenting author: Scott McCoombe, Dept. of Zoology, The University of Melbourne, Parkville, Victoria, 3010, Australia, Tel.: [phone], Fax: +61 3
8344 7909, E-mail: [email protected]