Preparation and Evaluation of a New Lipopolysaccharide-based Conjugate as a Vaccine Candidate for Brucellosis.
OBJECTIVE
Development of an efficacious vaccine against brucellosis has been a challenge for scientists for many years. At present, there is no licensed vaccine against human brucellosis. To overcome this problem, currently, antigenic determinants of Brucella cell wall such as Lipopolysaccharide (LPS) are considered as potential candidates to develop subunit vaccines.


METHODS
In this study, Brucella abortus LPS was used for conjugation to Neisseria meningitidis serogroup B outer membrane vesicle (OMV) as carrier protein using carbodiimide and adipic acid-mediated coupling and linking, respectively. Groups of eight BALB/c mice were injected subcutaneously with 10 μg LPS alone, combined LPS + OMV and conjugated LPS-OMV on 0 days, 14 days, 28 days and 42 days. Anti-LPS IgG was measured in serum.


RESULTS
The yield of LPS to OMV in LPS-OMV conjugate was 46.55%, on the basis of carbohydrate content. The ratio for LPS to OMV was 4.07. The LPS-OMV conjugate was the most immunogenic compound that stimulated following the first injection with increased IgG titer of ∼5-fold and ∼1.3-fold higher than that produced against LPS and LPS in noncovalent complex to OMV (LPS + OMV), respectively. The highest anti-LPS IgG titer was detected 2 weeks after the third injection (Day 42) of LPS-OMV conjugate. The conjugated compound elicited higher titers of IgG than LPS + OMV, that showed a 100-120-fold rise of anti-LPS IgG in mice.


CONCLUSIONS
These results indicate that our conjugated LPS-OMV can be used as a brucellosis vaccine, but further investigation is required.
Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran ; Department of Microbiology, Pasteur Institute of Iran, Tehran, Iran.
Seyed Davar
SD
Siadat
Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran.
Farzam
F
Vaziri
Department of Microbiology, Iran University of Medical Sciences, Tehran, Iran.
Mamak
M
Eftekhary
Department of Microbiology, Pasteur Institute of Iran, Tehran, Iran.
Maryam
M
Karbasian
Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
Arfa
A
Moshiri
Department of Hepatitis & AIDS, Pasteur Institute of Iran, Tehran, Iran.
Mohammad R
MR
Aghasadeghi
Department of Microbiology, Iran University of Medical Sciences, Tehran, Iran.
Mehdi S
MS
Ardestani
Department of Microbiology, Pasteur Institute of Iran, Tehran, Iran.
Meghdad Abdollahpour
MA
Alitappeh
Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran.
Amin
A
Arsang
Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran.
Abolfazl
A
Fateh
Department of Bacteriology, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
Shahin Najar
SN
Peerayeh
Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran.
Ahmad R
AR
Bahrmand
brucellosis; conjugate vaccine; lipopolysaccharide; outer membrane vesicle; vaccine candidate