Bridging the Gap: Conference Record [Abstract book, International Conference on AIDS (12th: 1998: Geneva, Switzerland)]

518 Abstracts 31116-31120

12th World AIDS Conference

(J. Acquired Immune Defic. Syndr. Hum. Retrovirol. 16/5, 1997, p. 333-339). We
examined production of antibodies against the non-structural HIV antigen nef by
intestinal biopsies from HIV-infected individuals.
Methods: We screened supernatants of short-term cultured intestinal biopsies,
saliva and plasma from 14 male patients infected with HIV-1 [10 with AIDS, mean
age: 44 years (32-60)], for nef-specific IgG, IgA, and IgM by Western blot.
Results: We identified nef-specific IgG, IgA, and IgM antibodies recognizing a
30 kD protein in biopsy supernatants, saliva, and plasma of HIV-infected patients
(table).
Table: nef-Specific IgG, IgA, and IgM antibodies in supernatants of short-term cultured intestinal biopsies, saliva, and plasma of HIV-infected patients.
Specimen nef-Specific antibodies
IgG IgA Igm
Biopsy supernatant 7/14 (50%) 7/14(50%) 1/14 (7%)
Saliva 5/14 (35%) 9/14 (64%) 1/14(7%)
Plasma 14/14 (100%) 10/14(71%) 4/14 (28%): number of positive patients/patients tested
Conclusions: In contrast to most structural HIV proteins, nef induces a strong
mucosal immune response in the majority of patients. Nef-specific secretory IgA
may reduce mucosal HIV load and nef-induced intestinal damage in HIV infection.
31116 1 Effects of HIV on immune responses in children with
thymic dysfunction - Immunodeficiency or tolerance?
Athena Kourtis', D.M. Thea2, F.K. Lee1, S. Nesheim1, A.J. Nahmias'. 'Dept of
Pediatrics, Emory University, 69 Butler St, Atlanta GA 30303; 2Harvard Institute
for International Dev, Cambridge, MA, USA
Background: We previously reported (New EngI J Med, 335:1431, 1996) that
about 15% of HIV infected infants, who are more likely to develop rapid disease
progression, have evidence of thymic dysfunction (TD+). More recently, we noted
that TD+ infants who were infected in utero had the most rapid progression. It
was of interest to study immune responses to HIV antigens in such TD+ infants,
with the possibility that HIV strains with the ability to affect thymopoiesis might
induce tolerance to viral epitopes.
Methods: Infants between 8-24 months of age were selected to allow for the
infants' ability to respond to HIV and to circumvent most of the transplacental
antibodies; 13 were identified to be TD+ and 51 were TD-. All these infants
were tested by Western Blot (WB). A variable number had other tests performed,
including antibody-secreting (ASC) and IgG-secreting (IgSC) cells- using the
ELISPOT assay, and serum IgG determinations. PCR positivity in the first week
of life was used as a marker of in utero infection.
Results: 8/13 (61%) TD+ and 2/51 (4%) of the TD- infected children had
4-9 bands missing on WB (P < 0.001), with most of the other infants having no
missing bands, and only a few lacking 1 or 2 bands. Six of the 13 TD+ infants
had been tested in the first week of life; of these, both in utero infected infants
and 2/4 of intrapartum infected ones had at least 4 WB bands missing. Two of the
TD+ infants (no early PCR results available) were agammaglobulinemic. None of
8 TD+ and 17/21 TD- infants had ASC to HIV antigens.
Conclusions: These findings indicate the early inability of TD+, in contrast to
TD-, infants to respond immunologically to HIV antigens. This may be a result
of total agammaglobulinemia, of suppression of CD4-related B cell antibody responses, and possibly to tolerance-pointing to the need of investigating further
these effects at the T cell level.
S31117 | Humoral immune response in Brazilian individuals
infected with different HIV-1 strains
Vera Bongertz2, M.L. Guimardes2, M.G. Morgado2, M.F.G. Soares-da-Costa2,
V.G.V. Santos', F.I. Bastos3. The HEC/AIDS Clinical Research Group, Hospital
Evandro Chagas, IOC - FIOCRUZ, Rio de Janeiro; 2Lab AIDS, Dpto. Imunologia,
IOC - FIOCRUZ, Rio de Janeiro; 3CICT - FIOCRUZ, Rio de Janeiro, RJ, Brazil
Objective: Evaluate the extent of antibody cross-reactivity against genetically
different HIV-1 subtypes/variants circulating in Rio de Janeiro, RJ, Brazil.
Methods: Seroreactivity of 63, 41 and 17 plasma of individuals infected with
respectively clade B, the Brazilian B" variant and clade F HIV-1 was tested against
homologous and heterologous biotinylated synthetic peptides corresponding to
the V3 loop. Neutralization (plasma from 29 B, 22 B" and 7 F) of primary HIV-1
(14 B, 11 B" and 2 F primary HIV-1 isolates) infection of normal human PBMC.
Results: While binding studies indicated a lower recognition of the B" peptide
by B plasma (P = 0.007), and of B (p < 0.0001) or F peptide (p = 0.002) by B"
plasma, no such difference was observed in neutralization assays:,0 Binding m '1 Neutralization U 's
C/ l.-.l B" % l B"

B B" F B B F
Conclusions: Similar neutralization susceptibility of B and B" HIV-1 isolates to
B, B" or F plasma despite significant differences in V3 peptide binding confirm the
importance of non-V3 epitopes in neutralization of Brazilian primary HIV-1 isolates

and indicate a similar susceptibility to neutralization of the HIV-1 subtypes/variant
circulating in Rio de Janeiro, RJ, Brazil.
Financed by PIAF/FIOCRUZ-MS; CNPq 529022/95-6, UNDP/World Bank
063/94.
31118 Mechanism(s) of HIV neutralization by specific antibodies
Catherine Spenlehauer, C. Moog, A. Kirn, A.M. Aubertin. Unite Inserm
74-Institute de Virologie 3 Rue koeberle 67000 Strasbourg, France
How do antibodies neutralize HIV and inhibit the productive infection of target
cells? Several mechanisms of action have been proposed that include impairment
of the binding to the receptor and/or the co-receptor, or interference with postbinding events necessary for the entry of the, virus. Understanding them may
provide useful informations to improve vaccinal strategies with aim of inducing
efficient neutralizing antibodies (NAb).
In order to examine the steps of the viral cycle affected by NAb, we first studied
the kinetic of action of neutralizing sera by adding them at various times before
and after the adsorption of the virus on the target cells. The autologous neutralization of primary isolates and the neutralization of the T-cell line adapted (TCLA)
strain HIV-1MN were compared. For HIV-1MN, a preincubation of the virus with
the sera was required to achieve neutralization. In contrast, this preincubation
was not necessary for primary isolates, as the autologous virus could still be
neutralized when adding the sera after adsorption on the target cells. Further
extensive studies of the steps involved in neutralization, including fusion and
penetration of the virus have been carried out. They highlight differences in the
mechanisms of action of NAb according to the virus used, and emphasizes the
discrepancy that exists between TCLA strains and primary isolates. Indeed, these
two types of viruses already contrast by their sensitivity to neutralization and by
the involvement of qualitatively different NAb.
Altogether our results suggest that TCLA strains are predominantly neutralized
through an inhibition of their binding to the target cell, whereas for primary isolates,
NAb may also affect post-binding events. By strengthening differences between
laboratory and field HIV-1 isolates, these observations assert the need to further
focus studies on primary isolates representative of the viruses found in infected
individuals.
31119| Characterization of salivary derived HIV-1 specific IgA
antibodies
Pia Skott1, E. Lucht2, I. Julander3, J. Dillner1, E. Bjorling'. 1MTC, Karolinska
Institute, Box 280, 17177 Stockholm; 2Dental Clin. for Inf Disease, 3Dept. of Inf
Disease, Huddinge Hospital, Stockholm, Sweden
Aims: To investigate the antigenic sites of the env-protein of HIV-1 that are
important for slgA antibody binding. And further to explore the possible role and
importance of IgA in neutralisation of HIV-1 at mucosal sites using saliva as a
model for the general secreted response.
Material and Methods: 45 HIV-1 infected patients and 15 controls were enrolled in this study.
Total levels of slgA was quantified by radial immunodiffusion and limiting diluting
ELISA. The antigenic sites were mapped using synthetic peptides representing
the amino acids in the envelope encoded proteins. The specificity experiments
were performed by ELISA and RIPA using insolubilized Artocarpus Integrifolia on
a 4% beaded agarose on a lectin column and to purify IgA from saliva. These
purified antibodies were also tested for their ability to neutralize HIV-1 in vitro.
Results: Total levels of sIgA in saliva could be correlated to levels of CD4+
cells. A persistant HIV-1 specific sIgA-response could be detected to a majority
of the peptides tested with the patient reactivity level ranging from 12-57%. For
the peptides mimicking regions in the env glycoproteins the saliva derived sIgA
antibodies reacted preferentially to the V4 region. In the V3 region we could
define a more C-terminal epitope for sIgA antibody binding as compared to the
antibodies of IgG isotype. Neutralization experiments are under investigation.
Conclusions: In this study we show a correlation between total IgA levels in
saliva and the levels of CD4+ cells. A difference in antigenic sites important for
antibody binding was shown between HIV-1 specific IgA and IgG antibodies.
599*/31120 HIV-specific cytotoxic T lymphocytes (CTLs) in
Thai exposed uninfected (EU) female sex workers
(FSWs) are directed to multiple regions of HIV-1
subtype E
Busarawan Sriwanthana1, K.B. Bond1, T.W. Hodge1, C.P. Pau1, T.D. Mastro2,
N.L. Young2, K. Limpakarnjanarat2. 1 1600 Clifton Road MS-A25, Center for
Disease Control (CDC) Atlanta GA 30333, USA; 2HIV/AIDS Collaboration,
Nonthaburi, Thailand
Background: The mechanisms by which individuals who are highly exposed to
HIV but remain uninfected (EU) are poorly understood. Previous studies have
identified HIV-specific CTLs and nonexpression of CCR5 as factors. We investi
gated the importance of these factors in explaining apparent resistance to HIV in
a cohort of EU FSWs in northern Thailand, a region where HLA-A11 and HLA-A2
are the dominant HLA types.
Methods: FSWs were defined as EU if they had worked >3 years in high-risk
brothels, were HSV-2 and syphilis positive, and were repeatedly HIV-seronegative and HIV PCR-negative. HIV-negative and unexposed persons from northern
Thailand of similar HLA- A types were used as controls. Frozen PBMC were