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Session 135
Poster Abstracts Prevention of Mother-to-Child Transmission Thursday, 1:30 - 3:30 pm Hall B |
Background: Newborns < 72 hours of age born to
HIV-1-infected women were enrolled in PACTG 326, a randomized, placebo-controlled,
double-blind study. The vaccine was a live recombinant canarypox ALVAC-HIV
vCP1452 (1452) (Aventis Pasteur) vaccine expressing HIV-1 env, gag, nef, and pol
genes with an AIDSVAX B/B (B/B) (VaxGen) boost. Vaccination at birth has the
potential to reduce breast milk transmission.
Methods: We enrolled 30
mother-infant pairs into 1 of 4 cohorts: 1452 alone; 1452 + B/B; saline placebo;
and saline placebo and alum placebo. Saline
placebo or 1452doses were given at 0, 4, 8, and 12 weeks post-birth with the
first dose given within 72 hours of birth. Those receiving B/B or alum placebo
received them at weeks 8 and 12. Antibodies to gp120, DP31, and RT were measured
by validated ELISA. DP31, a gp41 peptide absent in the vaccine, was used as a
control for maternal antibodies. Neutralizing
antibodies to HIV-1MN were also measured.
Results:
Interim
analyses demonstrate that 2 weeks post the last vaccination (1452 + B/B), 82%
of subjects had anti-gp120 responses, whereas only 55% had anti-DP31 responses.
By 12 weeks post-vaccination (6 months post birth), DP31 antibodies declined to
13%, but the anti-gp120 responses persisted in 100% of subjects with a previous
positive response. In addition, anti-RT antibody responses were present in 37%
of subjects at 12 weeks post-vaccination. Quantitative ELISA titers and
antibody half-life will be part of the unblinded data analysis. The overall
antibody response rates are higher in the B/B group as shown in the table below
(number positive/number tested). In the 1452 + B/B group, of the 7 subjects
that were DP31 negative at week 24, all were gp120 antibody positive and 43% of
those had neutralizing activity.
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1452 |
1452 + B/B |
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Week |
DP31 |
GP120 |
RT |
DP31 |
GP120 |
RT |
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0 |
100% (11/11) |
100% (11/11) |
100% (10/10) |
82% (9/11) |
100% (11/11) |
100% (11/11) |
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14 |
67% (6/9) |
78% (7/9) |
82% (9/11) |
55% (6/11) |
82% (9/11) |
73% (8/11) |
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24 |
50% (3/6) |
40% (4/10) |
25% (3/12) |
13% (1/8) |
100% (9/9) |
37% (4/11) |
Conclusions: Antibody responses were present in vaccinated
infants and could be differentiated from passively acquired maternal antibodies.
These interim blinded data indicate that in addition to being safe, this
combination prime boost strategy, vCP1452 and AIDSVAX B/B, elicited
vaccine-directed binding and neutralizing antibodies in infants.
Keywords: Antibody; Vaccine; Newborn
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