Program Supplement [International Conference on AIDS (14th: 2002: Barcelona, Spain)]

Poster Exhibitions
Track A
LBPEA9001
Myeloid and plasmacytoid circulating dendritic cell numbers
are already decreased in the first nine days after rectal SIV
infection in rhesus monkeys
Petitprez, Karine, Kahi, Sandrine, Jacques, Sebastien, Andrieu,
Muriel, Pretet, Jean-Luc, Hosmalin, Anne, Butor, Cecile (France)
Background: Dendritic cells (DC) are absolutely required to
activate naive T cells and they induce crucial early innate
immune responses. Two major populations are found in the
blood: myeloid CDiic+ DC, which secrete IL-12, and
plasmacytoid CD123 (IL-3-R)+ DC, which secrete type I
interferons, strong antiviral cytokines. We found that
circulating DC numbers were dramatically decreased in HIV
patients during primary infection (26 to 57 days post infection)
(Pacanowski, Blood, 2001; 9:3016). Here we quantify DC in the
very first days of rectal SIV infection in rhesus macaques.
Methods: 16 rhesus monkeys infected by the rectal route with
lo or ioo AID5o SIVmac251 were compared with io healthy
animals. DC populations were quantified in blood samples
from 16 hours to 9 days post infection (p.i.) using rare event
analysis by flow cytometry.
Results: The proportion of myeloid DC among peripheral blood
mononuclear cells was decreased significantly as early as 24
hours p.i. in the SIV infected monkeys compared to the healthy
animals (p=o.02). The proportion of plasmacytoid DC was also
decreased between 16 and 48 hours p.i. (p=o.o5).
Conclusion: We demonstrate for the first time that peripheral
blood DC are decreased as early as 24 hours post rectal SIV
infection, a good animal model for sexual transmission of H IV.
Corresponding author: Petitprez, Karine, DPT Immunology,
Cochin Institute, 27 Rue Fg St Jacques, 75014 Paris, France,
Tel: + 33 1 40516522, Fax: + 33 140516535,
Email: [email protected]
LBPEA90021
HIV-1 proteases from african viral subtypes: genetic diversity
and resistance mutations
Velazquez-Campoy, Adrian, Vega, Sonia, Freire, Ernesto
(United States)
The vast majority of HIV-1 infections worldwide are caused by
the C and A viral subtypes rather than the B subtype prevalent
in the United States and Western Europe. Genomic differences
between subtypes give rise to sequence variations in the
encoded proteins, including those identified as targets for
antiretroviral therapies. We present a complete thermodynamic
dissection of the differences between proteases from different
subtypes and the effects of the V82F/184V drug-resistant
mutation within the framework of the B, C and A subtypes.
These studies involved four inhibitors in clinical use (indinavir,
saquinavir, nelfinavir and ritonavir) and a second-generation
protease inhibitor (KNI-764). Naturally occurring amino acid
polymorphisms found in proteases from C and A subtypes
lower the binding affinity of existing clinical inhibitors by
factors ranging between 2 - 7.5. The pre-existing lower affinity
in the C and A subtypes significantly amplify the effects of the

drug-resistant mutation. Relative to the wild-type B subtype
protease, the V82F/184V resistant mutation within the C and A
subtypes lowers the binding affinity of inhibitors by factors
ranging between 40 and 3000. When the enzyme kinetic
properties (kcat and KM) are included in the analysis, the
biochemical fitness of the C and A subtype drug-resistant
mutants can be up to looo-fold higher than that of the wildtype B subtype protease in the presence of the studied
inhibitors. From a thermodynamic standpoint, the combined
effects of the drug-resistant mutations and the natural amino
acid polymorphisms on the Gibbs energy are additive, and
involve significant alterations in the enthalpy and entropy
changes for inhibitor binding. At the biochemical level, the
combined effects of naturally existing polymorphisms and drug
resistant mutations might have important consequences on
the viability of current HIV-1 protease inhibitors. Supported by
grants from the National Institutes of Health GM57144.
Corresponding author: Velazquez-Campoy, Adrian, Department
of Biology, The Johns Hopkins University, 34oo00 N. Charles St.,
Baltimore MD 21218, United States, Tel: [phone],
Fax: [phone], Email: [email protected]
[LBPEA90031
Crystal structure of a broadly neutralizing human monoclonal
antibody Fab to HIV-1 and proposition of its receptor-induced
epitope on gp120o
Darbha, Ramalakshmi, Phogat, Sanjay, Labrijn, Aran, Shu,
Yuuei, Gu, Yijun, Andrykovitch, Michelle, Zhang,
Mei-Yun, Pantophlet, Ralph, Burton, Dennis, Dimitrov
Dimiter, ji, Xinhua (United States)
Background: HIV entry into host cells is initiated by formation
of a complex between the viral envelope glycoprotein gpl2o,
the primary receptor CD4 and a coreceptor (typically CCR5 or
CXCR4). Recently, a novel broadly neutralizing human
monoclonal antibody Fab to HIV-1, X5, was isolated from a
phage display library using gpl2o-CD4-CCR5 trimolecular
complexes as screening agents (M. Moulard, S. Phogat, Y. Shu,
A. Labrijn, X. Xiao, J. Binley, M.-Y. Zhang, I. Sidorov, C. Broder, J.
Robinson, P. Parren, D. Burton, and D. Dimitrov 2002, PNAS,
99, 6913-6918). Of the currently known human monoclonal
antibodies with broad neutralizing activity, Fab X5 is the only
one that exhibits increased binding to gp120o in the presence of
CD4 and CCR5.
Methods and Results: The crystal structure of Fab X5 was
solved at 1.9 A resolution. The antibody combining site
features a long (22 amino acids) CDR H3 with a protruding
hook-shaped motif that may play a critical role in gpl2o
binding. Docking models of Fab X5 and the known gpl2o core
structures of HxBc2 and YU2 provide an indication of how X5
may interact with the gpl2o-CD4 complex. These models are
currently being investigated by X5 binding studies to a large
panel of gp120o mutants.
Conclusions: The findings further our understanding of
conserved, receptor-induced epitopes on gpi2o and may
provide a template for the design of small-molecule inhibitors
of viral entry.
Corresponding author: Dimitrov, Dimiter, Bldg 469 Rm 246,
Miller Dr., NCI-Frederick, Frederick, MD 21702, United States,
Tel: +i 301 846 1352, Fax: +i 301 846 6189,
Email: [email protected]

Program Supplement