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Serological evaluation of Brucella abortus S99 lipopolysaccharide extracted by an optimised method to be applied as a part of a candidate vaccine

Abstract number: P653

Sharifat Salmani A., Siadat S.D., Fallahian M., Ahmadi H., Norouzian D., Aghasadeghi M., Izadi Mobarakeh J., Nejati M., Parivar K., Nejadsattari T., Yaghmaie P.

Objective: Brucellosis is a globally found infectious disease and there is no licensed vaccine against human brucellosis. Brucellae can cause abortion in cattle and a debilitating fever (undulant fever) that may persist intermittently for years in humans. Lipopolysaccharide (LPS) is one of the main virulence factors and LPS-deficient strains have less virulence and intra-cellular survival potency. Wild type Brucellae mainly express smooth LPS (S-LPS) which is the main antigenic and immunogenic structure on the surface of smooth strains of this microorganism. A protective level of anti-Brucella IgG and IgM would be efficient to inhibit the primary infection and decrease the rate of infected Polymorphonuclears and macrophages.

Methods: Following the extraction of B. abortus S99 LPS by an optimised method based on hot phenol-water extraction, biological and biochemical evaluations of the extracted samples, animal models immunised intramuscularly with boosters in 14 and 28 days after the first injection. The animals were bled on the days 0 (before any immunisation and as the negative control), 14 (before the first booster injection), 28 (before the second booster injection) and 42 (two weeks after the second booster injection). The immune sera were separated, pooled and kept in -20°C.

Presence of anti-Brucella antibodiesin the sera of immunised animals demonstrated by Rose Bengal test (RBT), Serum agglutination test (tube agglutination and rapid slide agglutination) and Agarose Gel Immunodiffusion (AGID).

Results: Sera of immunised animals have been reported positive by RBT as a result of B. abortus LPS immunogenicity which we extracted through our optimised method. The highest titer of anti-Brucella antibodies detected two weeks after the third immunisation (assayed by tube agglutination and rapid slide agglutination tests). All of the collected serum samples of immunised animals reacted specifically with the LPS of B. abortus and precipitation lines between B. abortus LPS and immune sera appeared after 30 minutes.

Conclusion: This modified extracted LPS of B. abortus S99 has efficiently promoted the synthesis of high levels of anti-Brucella antibodies. Furthermore, elicited antibodies reacted specifically with the extracted LPS (demonstrated by AGID). Potency of this structure to induce high titers of specific antibodies against Brucella suggests the possible application of this component as a part of a sub-unit or conjugated vaccine for human brucellosis.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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