19 Aug 2008
research publications and abstracts are listed in ascending order, starting in
1983. Each listed Bruce E. Ivins as a lead or contributing author. This
section continues with publications from 1991 to 1999.
click to return to 1-10 of Ivins' publications.
11. Iacono-Connors LC, Welkos SL, Ivins BE, Dalrymple JM.
Protection against anthrax with recombinant virus-expressed protective antigen
in experimental animals. Infect Immun. 59(6):1961-5, 1991.
Abstract: We previously described the cloning and expression of the
protective antigen (PA) gene of Bacillus anthracis in both vaccinia virus and a
baculovirus. The antigenicity of the PA products was characterized. PA expressed
recombinant vaccinia viruses elicited a partial protective immune response
against a lethal B. anthracis spore challenge in guinea pigs and mice. The WR
strain vaccinia virus recombinant (WR-PA) protected 60% of male mice and 50% of
guinea pigs. WR-PA elicited high anti-PA antibody titers in mice but not in
guinea pigs. Connaught strain vaccinia virus recombinants failed to protect any
immunized animals. PA purified from baculovirus recombinant-infected cultures
plus adjuvant partially protected male CBA/J mice and completely protected
female Hartley guinea pigs from challenge. Both the recombinant and
nonrecombinant PA preparations combined with adjuvant elicited high anti-PA
antibody titers in Hartley guinea pigs and CBA/J mice. These data demonstrate
that the recombinant baculovirus- and vaccinia virus-produced PAs were
immunogenic in both guinea pigs and mice, that the baculovirus-PA recombinant
was a useful source of immunogenic PA, and that vaccinia virus-PA
recombinants may be feasible live anthrax vaccine candidates worthy of
consideration for further development as live vaccines.
12. Ivins BE, Welkos SL, Little SF, Crumrine MH,
Nelson GO. Immunization against anthrax with Bacillus anthracis protective
antigen combined with adjuvants. Infect Immun. 60(2):662-8, 1992.
Abstract: The protective efficacy of immunization against anthrax with
Bacillus anthracis protective antigen (PA) combined with different adjuvants was
tested in Hartley guinea pigs and CBA/J and A/J mice. Adjuvant components
derived from microbial products that were tested included threonyl-muramyl
dipeptide (threonyl-MDP); monophosphoryl lipid A (MPL); trehalose dimycolate (TDM);
and the delipidated, deproteinized, cell wall skeleton (CWS) from either
Mycobacterium phlei or the BCG strain of Mycobacterium bovis. Non-microbially
derived adjuvants tested included aluminum hydroxide and the lipid amine
CP-20,961. In guinea pigs, all adjuvants and adjuvant mixtures enhanced antibody
titers to PA as well as survival after a parenteral challenge of virulent B.
anthracis Ames spores. In contrast, PA alone or combined with either aluminum
hydroxide or CP-20,961 failed to protect mice. Vaccines containing PA combined
with threonyl-MDP or MPL-TDM-CWS protected a majority of female CBA/J mice.
Statistical analysis of survival data in the guinea pigs indicated that PA-MPL-CWS
and PA-MPL-TDM-CWS were more efficacious than the currently licensed human
13. Friedlander AM, Welkos SL, Pitt ML, Ezzell JW, Worsham
PL, Rose KJ, Ivins BE, Lowe JR, Howe GB, Mikesell P, et al. Postexposure
prophylaxis against experimental inhalation anthrax. J Infect Dis.167(5):1239-43,
Abstract: Inhalation anthrax is a rare disease that is almost invariably
fatal. This study determined whether a prolonged course of postexposure
antibiotics with or without vaccination would protect monkeys exposed to a
lethal aerosol dose of Bacillus anthracis when the antibiotic was discontinued.
Beginning 1 day after exposure, groups of 10 animals were given penicillin,
ciprofloxacin, doxycycline, doxycycline plus vaccination, vaccination alone, or
saline. Antibiotics were
administered for 30 days and then discontinued. Vaccine was given on days 1 and
15. Two animals died of causes other than anthrax and were not included in the
statistical analysis. Nine of 10 controls and 8 of 10 animals given only vaccine
died. Each antibiotic regimen completely protected animals while on therapy and
provided significant long-term protection upon discontinuance of the drug
(penicillin, 7 of 10 survived, P < .02; ciprofloxacin, 8 of 9 survived, P <
doxycycline, 9 of 10 survived, P < .002; doxycycline plus vaccination, 9 of 9
survived, P < .0002). Protection against rechallenge was provided by combining
postexposure antibiotic treatment with vaccination.
Ivins BE, Fellows PF, Nelson GO. Efficacy of a
standard human anthrax vaccine against Bacillus anthracis spore challenge in
guinea-pigs.Vaccine 12(10):872-4, 1994.
Abstract: The efficacy of an anthrax vaccine licensed for human use, MDPH-PA,
was tested in guinea-pigs intramuscularly challenged with 10, 100 or 1000 LD50
of spores from two virulent strains of Bacillus anthracis, Vollum 1B and Ames.
As demonstrated in other investigations, immunization with MDPH-PA provided
better protection against challenge with the Vollum 1B strain than with the Ames
strain, although vaccine efficacy against the Ames strain was better than
previously reported. Enzyme-linked immunosorbent assay of serum antibody titres
to B. anthracis protective antigen showed that there was no significant
correlation between survival and antibody titres.
15. Little SF, Ivins BE,
Fellows PF, Friedlander AM. Passive protection by polyclonal antibodies against
Bacillus anthracis infection in guinea pigs. Infect Immun. 65(12):5171-5,
Abstract: The protective effects of polyclonal
antisera produced by injecting guinea pigs with protective antigen (PA), the
chemical anthrax vaccine AVA, or Sterne spore vaccine, as well as those of
toxin-neutralizing monoclonal antibodies (MAbs) produced against PA, lethal
factor, and edema factor, were examined in animals infected with Bacillus
anthracis spores. Only the anti-PA polyclonal serum significantly protected the
guinea pigs from death, with 67% of infected animals surviving. Although none of
the MAbs was protective, one PA MAb caused a significant delay in time to death.
Our findings demonstrate that antibodies produced against only PA can provide
passive protection against anthrax infection in guinea pigs.
16. Ivins BE, Pitt ML, Fellows PF, Farchaus JW, Benner
GE, Waag DM, Little SF, Anderson GW Jr, Gibbs PH, Friedlander AM. Comparative
efficacy of experimental anthrax vaccine candidates against inhalation anthrax
in rhesus macaques. Vaccine 16(11-12):1141-8, 1998.
Abstract: The authors examined the efficacy of
Bacillus anthracis protective antigen (PA) combined with adjuvants as vaccines
against an aerosol challenge of virulent anthrax spores in rhesus macaques.
Adjuvants tested included i) aluminum hydroxide (Alhydrogel), ii) saponin QS-21
and iii) monophosphoryl lipid A (MPL) in squalene/lecithin/Tween 80 emulsion (SLT).
Animals were immunized once with either 50 micrograms of recombinant PA plus
adjuvant, or with Anthrax Vaccine Adsorbed (AVA), the licensed human anthrax
vaccine. The serological response to PA was measured by enzyme linked
immunosorbent assay. Lymphocyte proliferation and serum neutralization of in
vitro lethal toxin cytotoxicity were also assayed. In all vaccine groups,
anti-PA IgM and IgG titers peaked at 2 weeks and 4-5 weeks postimmunization,
respectively. Five weeks postimmunization, animals in all vaccine groups
demonstrated PA-specific lymphocyte proliferation and sera that neutralized in
vitro cytotoxicity. Six weeks after immunization, the animals were challenged by
aerosol with approximately 93 LD50 of virulent anthrax spores. Animals were bled
daily for 1 week to monitor bacteremia, and deaths were recorded. Anti-PA ELISA
titers in all groups of immunized animals were
substantially increased 2 weeks after challenge. One dose of each vaccine
provided significant protection (> 90%) against inhalation anthrax in the rhesus
17. Singh Y, Ivins BE,
Leppla SH. Study of immunization against anthrax with the purified recombinant
protective antigen of Bacillus anthracis. Infect Immun. 66(7): 3447-8,
Abstract: Protective antigen (PA) of anthrax
toxin is the major component of human anthrax vaccine. Currently available human
vaccines in the United States and Europe consist of alum-precipitated
supernatant material from cultures of toxigenic, nonencapsulated strains of
Bacillus anthracis. Immunization with these vaccines requires several boosters
and occasionally causes local pain and edema. We previously described the
biological activity of a nontoxic mutant of PA expressed in Bacillus subtilis.
In the present study, we evaluated the efficacy of the purified mutant PA
protein alone or in combination with the lethal factor and edema factor
components of anthrax toxin to protect against anthrax. Both mutant and native
PA preparations elicited high anti-PA titers in Hartley guinea pigs. Mutant PA
alone and in combination with lethal factor and edema factor completely
protected the guinea pigs from B. anthracis spore challenge. The results suggest
that the mutant PA protein may be used to develop an effective recombinant
vaccine against anthrax.
18. Zaucha GM, Pitt LM, Estep J, Ivins BE, Friedlander
AM. The pathology of experimental anthrax in rabbits exposed by inhalation and
subcutaneous inoculation. Arch Pathol Lab Med.122(11):982-92, 1998.
Abstract: OBJECTIVE: Although rhesus monkeys are considered to be an
appropriate model for inhalational anthrax in humans, an alternative for vaccine
and therapeutic efficacy studies is desirable. This study characterized the
pathology of lethal anthrax in rabbits challenged by subcutaneous inoculation
and aerosol exposure. MATERIALS AND METHODS: New Zealand white rabbits were
exposed by subcutaneous inoculation or aerosol to lethal doses of Bacillus
anthracis spores. RESULTS: The pathology of anthrax in rabbits exposed by either
route was similar, with principal findings occurring in the spleen, lymph nodes,
lungs, gastrointestinal tract, and adrenal glands. The cardinal changes were
hemorrhage, edema, and necrosis, with bacilli and limited leukocytic
infiltration. Features that depended on the route of exposure included
mediastinitis in aerosol-exposed rabbits, a primary dermal lesion after
subcutaneous inoculation, and differences in the pattern of lymph node
involvement. Lesions observed in rabbits were comparable to those of
inhalational anthrax in humans and rhesus monkeys. Noteworthy differences
included the lack of leukocytic infiltration in brain and meningeal lesions, the
relatively mild mediastinal lesions, and a lower incidence of anthrax-related
pneumonia in rabbits compared with humans. These differences may be attributed
to the greater susceptibility of rabbits to anthrax. Increased susceptibility is
associated with both reduced leukocytic response to the bacilli and a more rapid
progression to death, which further limits development of leukocytic infiltrates
in response to the basic lesions of hemorrhage and necrosis. Primary pneumonic
foci of inhalational anthrax, which may be influenced by preexisting pulmonary
lesions in humans, were not observed in our rabbits, which were free of
preexisting pulmonary disease. CONCLUSION: Anthrax in rabbits may provide
a useful model for evaluating prophylaxis and therapy against inhalational
anthrax in humans.
19. Little SF, Ivins BE. Molecular pathogenesis of
Bacillus anthracis infection. Microbes Infect. 1(2):131-9, 1999.
This review summarizes the current knowledge pertaining to the pathogenesis of
infection with Bacillus anthracis relative to the two exotoxins and the capsule.
Emphasis is given to the structure and activities of the individual components
the exotoxins, their interaction with cells, and the response of macrophages to
lethal toxin. Finally, results from vaccination studies are reviewed.
20. Pitt ML, Little S,
Ivins BE, Fellows P, Boles J, Barth J, Hewetson J, Friedlander
AM. In vitro correlate of immunity in an animal model of inhalational anthrax.
J Appl Microbiol. 87(2):304, 1999.
Abstract: The incidence of anthrax in humans is extremely low. Human
vaccine efficacy studies for inhalational anthrax cannot be conducted. The
identification of a correlate of protection that predicts vaccine efficacy is
crucial for determining the immune status of immunized humans. This surrogate
marker of immunity can only be established by using an appropriate animal model.
Numerous studies showed that protective antigen (PA) is the principle protective
antigen in naturally- or vaccine-induced immunity. However, attempts to
correlate the quantity of anti-PA antibodies with protective immunity in the
guinea pig model for anthrax and various vaccine formulations have failed. In
these studies, we used the licensed anthrax vaccine adsorbed (AVA) in rabbits.
Groups of New Zealand white rabbits, 10 or 20 per group, were immunized
intramuscularly (two doses, 4 weeks apart) with varying doses of AVA, ranging
from a human dose to 1:256 dilution in sterile phosphate-buffered saline (PBS).
Control rabbits received PBS/Alhydrogel according to the same schedule. Each
rabbit was bled 2 weeks after the second dose, and antibody levels to PA
measured by both the quantitative anti-PA IgG ELISA and the toxin-neutralizing
antibody (TNA) assay. Rabbits were aerosol-challenged 10 weeks from day 0 with a
lethal dose of Ames spores. All the rabbits that received the undiluted and 1:4
dilution of vaccine survived, whereas those receiving the higher dilutions of
vaccine (1:16, 1:64 and 1:256) had deaths in their groups. All the controls
died. Rabbit survival was compared with the antibody response. Statistical
models were used to test for significance of the peak antibody responses to
predict survival. Results showed that both the amount of anti-PA IgG and
TNA titres present in the sera at the time of the peak antibody response were
significant (P < 0.0001) predictors of survival. These results demonstrate that
the humoral immune response to AVA can predict protection in the rabbit model of
click to continue to 21-30 of Ivins' publications.