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

12th World AIDS Conference

Abstracts 11214-11218 25

macaques. After the early phase of infection, some animals maintained a cellassociated viremia and progressed to AIDS whereas for others, virus isolation
was intermittent or not possible. Those macaques remained asymptomatic for
years and the virus carried the original BK28 nef sequence. At later time when
virus replication resumed the nef ORF has a precise insertion of one nucleotide
restoring a SIVmac239-like carboxyl extremity. The expression of this domain is
associated with several SIVmac239-like mutations in position 19, 144, 196, 227
and 260 of the Nef protein. In macaques that maintained a high viral load the
same insertion had occurred already during the first month of infection
Our analysis shows that the C terminal domain of Nef protein contributes to
the full expression of its functions necessary to maintain a high level of virus
replication in vivo.
209* /11214 Viral dynamics in neonatal macaques after oral
inoculation with HIV-2287: Implications for human
transmission
Arnd Martin Herz1, C. Sherbert2, A. Schmidt2, M.B. Agy2, M.N. Robertson3,
P.D. Greenberg3, W.R. Morton2. 'Children's Hospital and Medical Center,
Seattle, WA; 2Regional Primate Research Center, Seattle, WA; 3University of
Washington, Seattle, WA, USA
Background: Fifty - 70% of human infants acquire HIV infection at the time
of parturition, possibly by swallowing infected maternal secretions. HIV-2287, a
derivative of human isolate HIV-2EHO, is pathogenic in adult macaques when administered by mucosal routes. Oral instillation of HIV- 2287 to neonatal macaques
provides a unique model of peri-partum maternal-fetal transmission. An understanding of viral dynamics in early neonatal HIV infection will be crucial to the
design of human anti-retroviral regimens to prevent neonatal transmission.
Methods: A previous titration study determined an animal infectious dose
(AID) for vaginal and rectal exposure in juvenile macaques corresponding to 103
TCID5o. In this study 3 neonatal and 1 juvenile macaca nemestrina were orally,
non- traumatically exposed to 103 or 104 TCIDso of HIV-2287. Viral load was
initially monitored daily by plasma RT-PCR; other monitoring included: weekly
complete blood count/cellular subtypes, quantitative HIV-2 viral cultures, and
monthly HIV-specific serology. Lymph node biopsies obtained 2-3 weeks after
acute infection and tissue from the time of necropsy were analyzed for viral
presence by RT-PCR, DNA-PCR, and viral culture.
Results: In mucosally infected animals, regardless of age or route of exposure,
HIV-specific RNA in plasma is first detected between days 6 and 10. Viral load
peaks between days 14 and 21 and declines moderately thereafter. None of
the animals orally exposed to 103 TCID5o, but 100% of the animals exposed to
104 TCID5o, became HIV-2 infected after exposure. This demonstrates an AID
corresponding to 104 TCID50 for oral exposure of neonatal animals. All infected
neonates developed prompt CD4 depletion. Both uninfected animals could subsequently be infected by re-inoculation with a higher dose or different mucosal route.
Conclusion: Viral replication in neonatal macaques after oral exposure to
HIV-2287 is rapid, with evidence of disseminated infection (by plasma RT-PCR) by
6-10 days and peak viremia by 14-21 days. HIV-infection is inoculum-dependent,
but contrary to experience with SIV, oral exposure with HIV-2287 is less infectious
in neonatal macaques than HIV-2287 by other mucosal routes in juvenile animals.
Human implications of this study suggest that anti-retroviral intervention in the
newborn must to be rapid and potent.
1215 Vaginal transmission of HIV-1 in Hu-PBL-SCID mice
Richard B. Markham1, Kristen V. Khanna', K. Whaley', L. Zeitlin2, D. Ford1.
1Johns Hopkins University, G 15 N Wolfe, Street, Baltimore, MD 21205;
2Reprotect, LLG, Baltimore MD, USA
Objective: To develop an animal model of vaginal transmission of HIV-1 which
can be used to study mechanisms of transmission and intervention strategies.
Methods: Using a SCID-Hu-PBL mouse model of HIV-1 infection, we studied
hormonal status, the necessity for cell-associated virus, and viral phenotype as
variables in the vaginal transmission of HIV-1 SCID mice reconstituted intraperitoneally at Day 0 with 5 x 107 human PBMC were administered progestin (5
mg, subcutaneously) and seven days later were inoculated vaginally with varying
doses of cell-free HIV-1 or different numbers of cultured PBMC that had been
infected with either SI or NSI strains of HIV-1. Cells or virus were inoculated into
anaesthetized mice in a volume of 30 plI using a pipette tip, with care being taken
not to traumatize vaginal tissue. Two weeks post-inoculation, mice were euthanized and peritoneal cells were collected by lavage. Polymerase chain reaction
and culture (p24 antigen detection) were performed to assay for the presence of
HIV-1.
Results: Neither progestin-treated nor untreated mice could be infected by
intravaginal inoculation of up to 106 TCID50 of cell free HIVBa-L. Infection was
established with HIVea-L-infected PBMC in progestin-treated mice in a dosedependent manner. Transmission using NSI (HIVBa-L) virus infected cells was
significantly more efficient than that using SI (HIVMN) virus infected cells, but at
high cell inocula infection could be established with SI variants

Conclusion: HIV-1-infected cells, but not cell-free virus, can transmit infection
by the vaginal route in progestin-treated Hu-PBL-SCID mice. The pattern of viral
phenotype selection in transmission parallels that observed in the clinical setting.
This animal system which models sexual transmission of HIV-1 should prove
useful for the development of strategies for the interruption of sexual transmission
of HIV-1 and for elucidating transmission mechanisms.
|11216 1Proliferation and apoptosis-related gene expression in
experimental AIDS-related simian lymphoma
Peter Biberfeld', E. Castanos-Velez', T. Heiden2, M. Ekman', J. Lawrence1,
B. Tribukait2, G. Biberfeld3. 1'mmunopathology Lab., Karolinska Institute,
Karolinska Hospital S-17176 Stockholm; 2Med. Radiology, Karolinska Institute,
Stockholm; 3Swedish Institute for Inf. Dis. Control, Stockholm, Sweden
A simian analogue to human AIDS was induced in cynomolgus monkeys injected
with simian immunodeficiency virus (SIVsm). Approximately 40% of the animals
developed disseminated high grade malignant non-Hodgkin lymphoma (sARL).
Studies of 24 such lymphomas showed that all were extranodal, high grade malignant, of B-cell origin and included monoclonal as well as polyclonal proliferations.
Tumor infiltrating TIA-1+ T lymphocytes and CD68+ macrophages were usually
abundant. Expression of a simian homologue to EBV-EBER was demonstrated
in 23/24 cases. Ploidy studies showed that these lesions were nearly to diploid
(D.I. = 1.0). Apoptosis was an uncommon finding in the tumors and in most
of the cases, tumor cells were shown to be highly proliferative as indicated by
Ki67 expression and S phase and G2 analysis. The antiapoptotic factors Bcl-2
and Mcl-1 were variably expressed by the tumor cells in most of the cases but
mutant p53 was not. However the proapoptotic factors Bax and Bak were usually
also demonstrable in the lymphoma cells, suggesting their functional inhibition
by Bcl-2. The results suggest a relationship between Bcl-2 expression and EBV
infection and a negative correlation between Bcl-2 expression and p53 activation.
These tumors showed a high homogeneity regard to extracellular matrix proteins
(ECM) and cell adhesion molecules (CAM) expression, displaying strong positivity for p1 (CD29) and a4 (CD49d) integrin subunits in the tumor as well as in
infiltrating non-tumoral cells but negativity for the /2 (CD18), aL (CD11a), avM
(CD11b) and ax (CD11c) integrin subunits. The similarity at the molecular level of
this simian experimental lymphoma model and human AIDS related lymphomas
is strongly emphasised by these findings.
Conclusions: AIDS-related B-cell lymphomagenesis can be studied experimentally in non-human, SIV infected, primates, particularly with regard to EBV
association, lymphoma cell proliferation, expression of antiapoptotic genes and
adhesion molecules in relation to decreased immunity.
S11217 Natural host resistance to SIV-induced AIDS: Complexity
of viral load and tissue tropism in African green monkeys
Jonathan Allan', S. Broussard2, K.L. Leighton2, S. Ahuja3, S. Staprans4,
M. Feinberg5. 17620 NW Loop 410, San Antonio, Texas 78227-5301; 2SW
Foundation for Biomedical Research, San Antonio, TX; 3Univ. Texas Hlth. Sci.
Ctr San Antonio, San Antonio, TX; 4Gladstone Inst. Virol. and Immun., San
Francisco, CA; 5Emory University, Atlanta, GA, USA
Objectives: To compare host and viral specific parameters in SIVagm infected
African green monkeys and rhesus macaques for clues in understanding differences in their susceptibility to SIV pathogenesis.
Methods: Quantitative competitive RT-PCR was used to determine viral load
in plasma and CSF of infected monkeys. In addition, we amplified and sequenced
viral DNA from brain and lymph node of a naturally infected AGM. Tissue variants
were also compared for chemokine receptor usage.
Results: High viral loads were detected in three naturally infected African
green monkeys (-106 RNA) eq./ml). In contrast, only low levels of proviral DNA
were found in the peripheral blood lymphocytes (<1 DNA copies/105 cells). The
numbers of SIVagm infected cells in both lymphoid and non-lymphoid tissues
was also relatively low ranging from 67 to 670 DNA copies/105 cells in the lymph
node with the highest levels detected in gastrointestinal tract respectively. Viral
RNA (>105 RNA eq./ml) was also detected in cerebrospinal fluids of 2 monkeys
coinciding with the isolation of cell-free SIVagm from the CNS. Sequence analysis
of amplified V2-V5 env gene fragments shows a large degree of amino acid diversity (14%) among viruses isolated from different tissues of a naturally infected
monkey. Brain derived SIVagm (sab-4br) replicated in 293 cells transfected with
CCR5, but not CCR2b. Finally, addition of sCD4 to SIVagm allowed infection of
CCR5 cells lacking CD4 expression.
Conclusions: The disparity between high viral loads of circulating cell-free
virus both in plasma and CSF coupled with only low numbers of infected cells
in tissue compartments commonly associated with HIV-1 suggests fundamental
differences in host-viral interactions leading to the apathogenic state in green
monkeys.

I112188 Enhanced pathogenicity of SHIV HXBc2 following whole
blood passage in Macaca nemestrina
Michael B. Agy, J. Thompson, R.F. Grant, E.M. Coon, E.E. Finn, B.J. Kennedy,
W.R. Morton. Univ. of WA Regional Primate Research Center, Box 357330,
Seattle, WA 98195, USA
Objective and Background: To develop an acutely pathogenic SHIV isolate to
be used as a macaque challenge virus in vaccine and drug efficacy studies and

Vaginal inoculum
1.00 ( 106 huPBMC
0.25 x 106 huPBMC
0.05, 106 huPBMC

No. mice p24 positive/no, mice inoculated
NSI (HIVBa-L) SI (HIVMN) p value
5/5 1/5 0.05
4/5 0/5 0.05
1/5 0/5 NS