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

278 Abstracts 21197-21200

12th World AIDS Conference

for vaccine development. The objective of this study is to determine whether antibody responses to HIV-1 can be broadened by DNA prime/protein boost vaccine
regimens that use envelope (Env) immunogens derived from subtype B and E
HIV-1 strains.
Methods: The plasmids used for immunizations express Env gp120 from
two non-synctium inducing (NSI) primary isolates, the clade B strain, HIV- 1us4
(pCMVKA 120us4), and the Thai subtype E strain, HIV-1CM235 (pCMV6a120CM235).
The two Env protein vaccines used were Chiron's rgp120SF2 and rgp120CM235
derived from the subtype B (SI), HIV-1SF2, and the subtype E (NSI), HIV-1cM235,
respectively. The protein immunogens were injected with the MF59 adjuvant and
are identical to those currently employed in human clinical trials in the US and
Thailand. Groups of 8 guinea pigs received intramuscular (IM) DNA immunizations at 0 and 6 weeks with one or both plasmids, followed by a single IM boost
at 12 weeks with one or both protein vaccines. Additional groups received one
or both of the gp120 proteins alone. Serum antibody responses to gp120 were
measured by subtype B and E-specific ELISA, and neutralizing responses were
measured against HIV-1 strains representing each subtype.
Results: Anti-gpl20 antibody responses were observed in all animals following two immunizations with Env-expressing plasmid DNA using either the
pCMVKA120us4 or pCMV6a120CM235 plasmid, or both plasmids combined. Subtype-specific ELISA titers ranged from 10-3 to 10-4 and were consistently higher
against the subtype represented by the immunogen. Both ELISA and neutralizing
antibody responses were increased 1-2 logs following a single protein boost
to levels that were comparable to those observed after multiple rgp120/MF59
protein immunizations alone. Results so far indicate that animals immunized with
the subtype B immunogens produced neutralizing antibodies against subtype
B strains, while those immunized with subtype E showed broader neutralizing
responses against both subtype B and E HIV-1 strains. Furthermore, the antibody
responses against the combined subtype B and E immunogens appear to be at
least additive.
Vaccine strategies that employ DNA priming and protein boosting with envelope immunogens derived from multiple HIV-1 subtypes may provide a means of
inducing neutralizing antibody responses against diverse HIV-1 isolates.
21197 1 The effect of HIV-specific immunization in subjects with
other subtype HIV-1 infection in Thailand: One year
interim report
Vina Churdboonchart1, A. Limsuwan1, R. Moss2, W. Sirawaraporn1,
B. Smutharaks', R. Sutthent1, R. Trauger2. 1Dept of Pathobiology, Fac of
Science, Mahidol University Rama 6 Rd. Bangkok, Thailand; 2The Immune
Response Corporation Carlsbad CA, USA
Objective: To examine the effect of immunizations with an inactivated
gpl20-depleted HIV-1 Immunogen (REMUNE ") in Thai subjects infected with
HIV-1 type "E" infection.
Design: Open label long term immunization.
Methods: Thirty HIV+ volunteers with CD4 cell counts >300 cells//il and a
mean CD4 count of 451 cells/mm3 were recruited into the study. Each volunteer
received intramuscular injections of REMUNE"T into the belly of the triceps muscle
for four months at four-week intervals to test safety of the vaccine. Follow up
program was scheduled for two years and the first year follow up study was done
with immunizations scheduled at three month intervals (Week 24, 36, 48, and
60). Clinical assessment was performed at each visit, including medications and
adverse events, vital signs, body weight, CD4 and CD8 cell counts, CD4 and
CD8 percent, and CD4/CD8 ratio.
Results: Subtype analysis indicated 29 of the 30 volunteers were infected with
subtype E with only 1 volunteer infected with subtype B. Subjects had a significant
increase in CD4% (p = 0.0002), CD8% (p = 0.001), and body weight (p = 0.008)
compared to preimmunization levels. Significant decline in viral plasma RNA was
shown in the NASBA analysis. HHV8 analysis showed positive results in 12 volunteers (40%) with highly positive results in 3 cases and no indication of progression
to AIDS was noted. Western Blot analysis demonstrated an increase in either the
repertoire or the intensity of the serological response to HIV in 28 cases.
Conclusion: The vaccine was well tolerated with no serious adverse events
reported. Cross subtype reactivity by Western Blot showed increased HIV-specific humoral immune responses and significant increases in body weight and
other immunological markers. This data suggests that REMUNET" is safe and
immunogenic in HIV+ Thai subjects infected with subtype E.
549*/21198 Protective T-cell mediated immunity induced by a
consecutive HIV-1 DNA and avipox vaccine
regimen
Stephen Kent1, A. Zhao2, E.M. Dax3, J.D. Chandler2, H.L. Robinson6,
D.B. Boyle4, I.A. Ramshaw5. 1Macfarlane Burnet Centre for Medical Research,
PO Box 254, Fairfield 3078; 2APRU, Macfarlane Burnet Centre, Fairfield, VIC;
3National Serologic Reference Laboratory, Fairfield, VIC; 4AAHL, CSIRO,
Geelong, VIC; sJCSMR, Australian National University, Canberra, ACT,
Australia; 6Univ. Massachusetts Medical Center, Worcester, MA, USA

Objectives: HIV-specific T cell responses are widely viewed as essential to tile
efficacy of HIV-1 vaccines. Recombinant DNA and avipox virus (rAPV) vaccine
vectors are, separately, the leading safe vaccine vectors with the potential to
induce cell-mediated immunity to HIV-1. We assessed cytotoxic T lymphocyte
(CTL) and T-helper (Th) responses in macaques after sequential HIV-1 DNA

and rAPV vaccination and assessed whether protective immunity from HIV-1
challenge was induced.
Methods: HIV-1 env/gag DNA was administered epidermally to 4 M. nemestrina
by gene gun. rAPV encoding env and gag/pol were used to boost the immunised
macaques. Immunised and control animals were challenged IV with -100 monkey infectious doses of autologous macaque-PBMC grown homologous HIV-1LAI.
Quantitative HIV-specific CTL, Th and antibody responses were assessed preand post-challenge.
Results: All HIV-1 DNA/rAPV vaccinated macaques animals evaluated developed HIV-specific CTL and Th responses after DNA vaccination which were
significantly enhanced (up to 20-fold) after rAPV boosting, with the CTL precursor
frequency reaching 1/104 PBMC. HIV-specific Th responses, but not antibody
responses, induced by the HIV-1 DNA vaccinations were also augmented by
tile rAPV vaccinations and cytokine analyses showed that the Th response was
predominantly of a Thl phenotype. All 4 unimmunised control animals, but no
vaccinated animals, became acutely infected with HIV-1 following challenge,
as assessed by seroconversion and serial plasma HIV-1 RNA and PBMC and
lymph node HIV-1 DNA analyses. Interestingly, the HIV-specific CTL activities
were further augmented (2-4 fold) in the vaccinated animals within the first few
weeks following HIV-1 challenge, suggesting that tile CTL induced by the vaccine
recognised the challenge inoculum.
Conclusion: A novel vaccine regimen of consecutive DNA and rAPV immunisations induced HIV-1 specific CTL and Thl responses which prevented HIV-1
infection of macaques. CTL responses were boosted further by viral exposure,
a potentially attractive mechanism to both recognise divergent HIV-1 strains and
maintain immunity to HIV-1. This vaccine strategy could represent the basis of a
safe and effective regimen for the induction of cell-mediated immunity to HIV-1.
496*/21199 A Phase I trial of vaccinia-env/gag/pol (TBC-3B)
given by alternative routes, boosted with rgpl20
Michael C. Keefer1, M.J. McElrath2, K. Weinhold3, G.J. Gorse4, M. Mulligan5,
D. Francis6, D. Panicali7. 1601 Elmwood Avenue Box 689 Rochester New YOrk
14642; 2University of Washington, Seattle WA; 3Duke University Durham, NC;
4St Louis University, St. Louis, MO; 5University of Alabama Birmingham,
Birmingham, AL; 6 Vaxgen Inc, San Francisco, CA; 7Therion Biologics Corp,
Cambridge, MA, USA
Objectives: To define the safety and immunogenicity of TBC-3B (Therion Biologics) given by scarification (scar), intradermal injection (id), or subcutaneous
injection (sq), boosted with rgpl20 MN (VaxGen, Inc.) in healthy HIV-1 negative,
vaccinia-naive volunteers.
Design: Prospective, randomized, double-blind, controlled trial.
Methods: TBC-3B, a live recombinant vaccinia virus expressing env and
gag/pol genes of HIV-1 strain IIIB, was given at a dose of 3.67 x 106 pfu on day
0 by scar, id, or sq, and followed by TBC-3B at the same dose (scar) or a 100 x
higher dose (id and sq) at 2 months. Licensed vaccinia without the HIV insert
(DryVax, Wyeth) was the control for each group (n = 2 each). Subsequently, all
volunteers will be boosted intramuscularly with rgpl20 MN/alum (or alum control
alone) at 8 and 12 months. Enrollment was staggered for interval safety assessments, starting with the scar group, followed by a portion of the id and sq groups
(n = 5 each). Blood was obtained 2 weeks after each vaccination for assessment
of immunogenicity (binding/neutralizing antibody, T-cell memory, CTL).
Results: Thirty-six volunteers were vaccinated; 12 by each route. Twelve of
12, 4/5, and 3/5 had typical clinical takes after the first dose by scar, id, and
sq, respectively. The local/systemic reactions associated with the escalated dose
TBC-3B boost by id and sq were no greater than those after the initial dose. Two
weeks after the 2 month dose, HIV-1 Western blots were positive in 0/10, 4/6
and 2/6 and HIV-1 ELISAs were positive in 0/8, 3/4, and 2/3 subjects in the scar,
id, and sq groups, respectively. Additional immunogenicity results, including CTL
assessments, are pending.
Conclusion: TBC-3B administered by scar, id, and sq to vaccinia-naive, HIVnegative volunteers is well tolerated, even when given as a 100x higher dose
boost. HIV-1 Western blot and ELISA responses were seen early in the id and sq
groups, but not in the scar group. Additional safety and immunogenicity data will
be presented.
548* / 21200 Recombinant vaccine-induced protection against
the highly pathogenic SIVmac251 dependence on
route of challenge exposure
Geneoveffa Franchini.
NIH NCI DBS BRL Bldg. 37 Rm. 6B-18, Bethesda, MD 20817, USA
Vaccine protection from infection and/or disease induced by the highly pathogenic
simian immunodeficiency virus strain (SIVmac251) in the rhesus macaque model
is a challenging task. Thus far, the only approach that has been reported to
protect a fraction of macaques from infection following intravenous challenge with
SIVmac251 was use of a live attenuated SIV vaccine. In the present study, the gag,
pol, and env genes of SIVK6w were expressed in the NYVAC vector, a geneti
cally engineered derivative of the vaccinia virus Copenhagen strain that displays
a highly attenuated phenotype in humans. In addition, the a and /f chains of
interleukin (IL)-12, as well as the IL-2 gene, were expressed in separate NYVAC
vectors and inoculated intramuscularly, in conjunction with or separate from the
NYVAC-SIV vaccine, in 40 macaques. The overall cytotoxic T-lymphocyte (CTL)
response was higher, at the expense of proliferative and humoral responses,
in animals immunized with NYVAC-SIV and NYVAC-IL-12 than in animals im