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

108 Abstracts 13114-13117

12th World AIDS Conference

Methods: The HIV-1 serotype was determined of 441 HIV+ serum samples
from asymptomatic pregnant women and blood donors collected in the years
1989, 1994 and 1997. V3 serotyping was chosen as a first step method since
HIV-genetic subtyping is not feasible in large samples collections. The correlation
of V3 serology and sequencing (350 bp env) is only 72%, but a good correlation
was shown between the amino acid structure of the V3 loop and the serological
result (98%).
Results: The serotype prevalence among pregnant women under 20 years
(considered as seroconverters within the last 3 years) remained between 1989
and 1997 almost stable: mean prevalence A 35.0%; C 51.1%; D 13.9%. By
including older age groups into the analysis, we observed in specimens collected
1996 a shit within the age specific serotype prevalence of A and C. Serotype
C dropped from 51.5% (age 16-18) to 49.0% (age 19-21) to 36.1% (age 22-25)
to 34.3% (age 26-30) and 36,2% (age over 30). In contrast the prevalence of
A rose from 33% to 40.8% to 41.7% to 48.6% and 48.3% (same age groups).
The prevalence old remained with 12-17% almost stable. A similar trend was
observed in the years 1989 and 1994.
Conclusions: Since the subtype distribution among new infections remained
stable since 1989 one would expect an equal subtype distribution in all age
groups. This observed change of the subtype distribution by age group could be
explained, if subtypes differ in respect to pathogenicity and progression to death.
We therefore hypothesize that in the Mbeya Region serotype C has a faster
disease progression than serotypes A and D.
I13114 Decline in the prevalence and incidence of HIV-1 infection
in population-based studies in Bukoba Urban, Kagera,
Tanzania
Gideon Kwesigabo', J. Killewo', C. Makwayal, W. Urassal, F. Mhalu1,
G. Biberfeld2, A. Sandstrom3. 1Muhimbili University, College of Health Sciences,
PO. Box 65015, Dar Es Salaam, Tanzania; 2Karolinska Institute, Stockholm;
3Umea University, Umea, Sweden
Objective: To monitor the trend of HIV-1 infection in the Bukoba urban area of
Kagera, Tanzania.
Design: Cross-sectional and prospective cohort studies.
Methods: A random population sample obtained through multistage cluster
sampling techniques was established in 1987 and assessed for HIV-1 seroconversion in 1989. In 1993 and 1996 new randomly selected population samples
were established and also followed up for HIV-1 seroconversion. These three
study populations at recruitment formed the basis for the prevalence estimates
while the HIV-1 seronegative individuals formed the population at risk for seroconversion and hence yielded the person-years of observation. From all consenting
individuals, blood samples were drawn and tested for HIV-1 antibodies by two
anti-HIV enzyme-linked immunosorbent assays (ELISA). In the studies done in
1987 and 1989 all ELISA-reactive sera were tested by a Western blot (WB) assay
while in the subsequent studies sera showing repeatedly discordant results in the
two ELISAs were subjected to WB analysis.
Results: There was a significant decline in both the prevalence and incidence
of HIV-1 infection in the studied populations. The age adjusted prevalence decreased from 24.2% (n = 553) in 1987 to 18.2% (n = 649) in 1993 and 12.8%
(n = 1276) in 1996 (p = 0.0001). The observed decline in prevalence was most
pronounced among younger males and females (15-24). Only seven new cases
were found in 1996, based on a 3-year follow-up of 380/531 seronegative persons. This implies a decreased incidence from 47.5/1000 pyrs in 1987-1989 (337
pyrs studied) to 5.6/1000 pyrs in 1993-1996 (1243 pyrs studied).
Conclusion: A reduction in both prevalence and incidence of HIV-1 infection
has been shown. This favourable development in Kagera may represent a true
reduction in HIV-1 transmission resulting from a change in behaviour and/or
depletion of the susceptible population due to deaths or migration. The paper
discusses the possible reasons for the observed decline.
13115 V3 of HIV-1 subtype C is over-represented in intersubtype
A, C and D recombinant genotypes from perinatally
infected infants in Tanzania
Boris Renjifo1, D. Mwakgile2, G. Msamanga2, B. Chaplin1, F. Bannberg',
P. Shah1, D. Spiegelman3, D. Hunter3, W. Fawzi3, M. Essex1. 1'Harvard AIDS
Institute 651 Huntington Av. FXB 310, Boston, MA; 3Harvard School of Public
Health, Boston, MA, USA; 2Muhimbili Medical Centre, Dar Es Salaam, Tanzania
Background: We found that HIV-1 subtype C and intersubtype recombinant
genotypes are expanding in Dar es Salaam where HIV-1 subtypes A and D were
once the only subtypes present in the general population. The virus subtype
detected in the infants represents the presence of that virus subtype in the
mothers.
Objective: Given the role of the V3 region in cell tropism and possibly transmission, we attempted to establish whether the V3 region from different subtypes had
the same probability of being present in recombinant genomes from perinatally
infected infants.
Methods: Phylogenetic and recombinant analysis were done on envelope

clones (C2-V5) from 140 infected infants from Dar es Salaam, Tanzania.
Results: Out of 140 envelopes, 53 (39%) were classified as subtype A, 36
(26%) were classified as subtype C, 27 (19%) were classified as subtype D and
24 (17%) were classified as intersubtype recombinants. Recombinants involving
subtype C sequences were found more frequently than recombinants involving
subtype A or subtype D. Twenty of 24 (83%) recombinants have subtype C

sequences, 17 of 24 (71%) have subtype D sequences and 6 of 24 (25%) have
subtype A sequences. Subtype C (V3) was found in 18 of 20 recombinants
containing subtype C sequences. Subtype D (V3) was found in 0 of 17 recombinants carrying subtype D sequences and subtype A (V3) was detected in 6 of
8 recombinants involving subtype A sequences. The differences in V3 subtype
frequency in the recombinants was significant when we compared subtype C to
subtype D (Fisher exact test, p < 0.001), or subtype C against subtype D and A
(p < 0.001). This difference was not observed when we compared subtype C and
subtype A.
Conclusion: These results suggest that HIV-1 subtype C has recently demonstrated a selective advantage for preferential spread in Tanzania. We also found
evidence that the V3 of gp120 may be an important region for providing this
selective advantage.
13116 1 Sexual risk behaviors, knowledge, and attitudes in a
population-based probability sample of Dar es Salaam,
Tanzania: Results from the voluntary HIV counseling and
testing study (VHCTS)
Thomas Coates', Japhet Killewo2, S. Gregorich', G. Sangiwa2. ' UCSF Center
for AIDS Prevention Studies 74 New Montgomery San Francisco, CA, USA;
2Muhimbili University College Dar Es Salaam, Tanzai
Objectives: To estimate and describe the level of sexual risk behavior, HIV
transmission knowledge and related attitudes in the population of Dar Es Salaam,
Tanzania. To empirically assess the need and demand for voluntary HIV counseling & testing (VCT) services in the population of Dar es Salaam. To complement
the findings of the VHCTS-a multi-site randomized controlled trial of the efficacy
of VCT as a preventive intervention.
Methods: A multistage area sampling design was developed. Dar es Salaam is
administratively divided into districts, wards, and ten-cells. Of the 32 urban wards,
10 were selected with probability proportional to estimated size. Within each
selected ward, 20 ten-cells were selected at random. Within selected ten-cells,
5 households (HH) were selected at random and within each HH one eligible
member was selected at random as the respondent.
Results: 859 (86%) of all interviews were completed. We will present data
regarding participants' demographics, sexual history, current sexual behaviors,
condom use, HIV transmission knowledge, HIV transmission attitudes, and HIV
testing history. Reports on sexual behaviors include prevalence of protected and
unprotected sexual intercourse with both "primary" and other partners. We will
also compare these data to those from participants in the VHCTS.
These are unique data that exist only for a few countries. This population-based
probability sample is important in: (1) mapping sexual risk behaviors in Dar es
Salaam, (2) providing a population-based comparison to the risk-profiles of participants in the VHCTS, which has already demonstrated the efficacy of VCT as
a preventive intervention, (3) informing policy decisions regarding the delivery of
HIV-related services in Dar es Salaam-specifically, decisions regarding the need
for services and their optimal placement.
S13117 HIV-1 subtype and shedding of cervicovaginal HIV-1 DNA
during pregnancy
Grace John, J. Neilson, P. Lewis, J. Overbaugh, R.W. Nduati,
D.A. Mbori-Ngacha, J. Kreiss. Bpx 359909 IARPT, Univ. of Washington, Seattle,
WA 98195, USA
Objective: To determine the relationship between HIV-1 subtype and clinical
characteristics, plasma viral load, and prevalence of genital provirus in a cohort
of pregnant women.
Methods: HIV-1 seropositive pregnant women in an ongoing breast feeding
study were enrolled during pregnancy and an interview and physical examination
were conducted. Blood was collected for CD4 counts and plasma viral load.
Subtype was determined using the heteroduplex mobility assay (HMA). Cervical
and vaginal specimens were collected for HIV-1 DNA detection.
Results: HIV-1 subtype was determined for 305 women, of whom 74% were
subtype A, 21% subtype D, and 5% subtype C. Women with subtype C had
a higher lifetime number of sexual partners, with 93% reporting more than 3
partners (versus 76% of women with other subtypes, p = 0.01). Women with
subtype C were significantly more immunosuppressed (mean CD4 count 460)
than women with other subtypes (D: CD4 596, and A: CD4 632 (p = 0.002)).
The mean plasma viral load was highest for women with subtype C and lowest
for subtype D (252, 899 copies/mi for subtype C, 157, 886 c/ml for A, and 99,
654 c/ml for D (p = 0.05 for D vs non-D)). Cervical and vaginal HIV-1 DNA
detection were significantly associated with having a higher plasma viral load.
While cervical HIV-1 provirus shedding did not differ between subtypes, there
were marked differences in vaginal shedding. In a multivariate analysis adjusting
for plasma viral load, women with subtype C were significantly more likely to have
detectable vaginal HIV-1 DNA (OR 4.3, 1.3-14), while women with subtype D was
associated with the lowest prevalence of vaginal HIV-1 DNA (0.02, 0.07-0.7).
Conclusions: Subtype C was associated with increased and subtype D with

decreased vaginal HIV-1 DNA detection. Subtype-related differences in genital
shedding of HIV-1 provirus may influence likelihood of heterosexual or vertical
transmission.