Abstract
ABSTRACT It was compared the antibody response of sows immunized with two experimental vaccines produced with L.interrogans, serovar Canicola, strain LO-4, isolated in Brazil.One of the vaccines was the usual bacterin (whole culture inactivated with phenol and adjuvanted with aluminum hydroxide -WC-AlOH3) and the other one was a subunit vaccine produced with a lipopolysaccharide (LPS) fraction extracted from the bacteria outer envelop and with the lipid A, also extracted from the leptospira wall as adjuvant (LPS-MPLA). Experiment was as follows: group 1 (n = 11), not immunized control, group 2, (n = 11): two immunization with 30 days interval of LPS-MPLA vaccine and group 3 (n = 11): two immunization with 30 days interval of WC-AlOH3 vaccine All three groups were simultaneously immunized, independently of pregnancy stage. Both agglutinin and neutralizing post vaccination antibodies levels were measured respectively by the microscopic sera agglutination with live antigens test (MAT) and the in vitro leptospira growth inhibition test (GIT). Sera collections were performed each 30 days during four months after the first vaccination. Non vaccinated control group animals presented no agglutinating antibodies against Canicola serovar during the whole experiment. At 32 and 68 post vaccination days the agglutinating antibodies levels of group 2 (LPS-MPLA) were significantly higher than the observed in group 3 (WC AlOH3), respectively, p = 0.013 and p = 0.031. The differences observed in the growth inhibition antibodies titers of the two vaccines tested were not significant (p > 0.05). Despite the peak of post-vaccination agglutinins have been registered at 68 days after first immunization, higher levels growth inhibition antibodies were detected at 30 days of first vaccination. Subunit vaccine presented the same immunogenic capacity for the production of neutralizing antibodies as the whole culture one.
Highlights
Vaccines used in swine leptospirosis control are inactivated cultures of Pomona, Icterohaemorrhagiae, Hardjo, Canicola, Grippotyphosa and Bratislava serovars
Agglutinating antibodies On the 32nd post vaccination day the proportion of reactant animals immunized with the WC-AlOH3 vaccine was 0/11 and to the LPS-monophosforil A lipid (MPLA) vaccine it was 6/11, with an arithmetic mean titer of 0.91 and titer standard error of 1.047
In the blood collections performed at 68 and 123 days, the differences observed between the LPS-MPLA subunit vaccine and the WC-AlOH3 were not significant (p > 0.05)
Summary
Vaccines used in swine leptospirosis control are inactivated cultures of Pomona, Icterohaemorrhagiae, Hardjo, Canicola, Grippotyphosa and Bratislava serovars. These bacterins do not induce cross protection against different pathogenic leptospira serogroups. These vaccines protect only against clinical illness, but do not impair the kidney infection (Branger et al, 2005). Leptospira subunit vaccines could be an option for the prevention of leptospirosis, since they are usually constituted by antigens that can stimulate immune response, such as lipopolysaccharide (LPS) and its glycolipids, lipoproteins, membrane proteins, phospholipids and peptidoglycan (Cinco et al, 1996). Midwintwer et al (1990) detected immune response in hamsters using Pomona and Hardjo LPSderived immunoconjugates anti-leptospira vaccines, with the maximal production of agglutinin titers between the sixth and tenth post vaccination weeks. Sonrier et al (2000) observed complete protection against homologous serovars and partial protection against heterologous ones in hamsters treated with leptospira LPS
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