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The adhesin complex protein (ACP) of Neisseria meningitidis is a new adhesin with vaccine potential.

Hung MC, Heckels JE, Christodoulides M - MBio (2013)

Bottom Line: ACP functioned as an adhesin, as demonstrated by reduced adherence of acp knockout (MC58 ΔACP) meningococci to human cells in vitro and the direct surface binding of rACP and by the ability of anti-rACP sera to inhibit adherence of wild-type bacteria.Infections caused by Neisseria meningitidis serogroup B are still significant causes of mortality and morbidity worldwide, and broadly protective vaccines of defined antigen composition are not yet licensed.We also report that a recombinant ACP protein vaccine induces murine antibodies that significantly kill meningococci expressing different ACP.

View Article: PubMed Central - PubMed

Affiliation: Neisseria Research Group, Clinical and Experimental Sciences, Sir Henry Wellcome Laboratories, University of Southampton, Faculty of Medicine, Southampton General Hospital, Southampton, United Kingdom.

ABSTRACT

Unlabelled: The acp gene encoding the 13-kDa adhesin complex protein (ACP) from Neisseria meningitidis serogroup B strain MC58 was cloned and expressed in Escherichia coli, and the purified recombinant ACP (rACP) was used for immunization studies. Analysis of the ACP amino acid sequences from 13 meningococcal strains, isolated from patients and colonized individuals, and 178 strains in the Bacterial Isolate Genome Sequence (BIGS) database showed the presence of only three distinct sequence types (I, II, and III) with high similarity (> 98%). Immunization of mice with type I rACP in detergent micelles and liposomes and in saline solution alone induced high levels of serum bactericidal activity (SBA; titers of 1/512) against the homologous strain MC58 and killed strains of heterologous sequence types II and III with similar SBA titers (1/128 to 1/512). Levels of expression of type I, II, or III ACP by different meningococcal strains were similar. ACP functioned as an adhesin, as demonstrated by reduced adherence of acp knockout (MC58 ΔACP) meningococci to human cells in vitro and the direct surface binding of rACP and by the ability of anti-rACP sera to inhibit adherence of wild-type bacteria. ACP also mediated the invasion of noncapsular meningococci into human epithelial cells, but it was not a particularly impressive invasin, as the internalized bacterial numbers were low. In summary, the newly identified ACP protein is an adhesin that induces cross-strain bactericidal activity and is therefore an attractive target antigen for incorporation into the next generation of serogroup B meningococcal vaccines.

Importance: Infections caused by Neisseria meningitidis serogroup B are still significant causes of mortality and morbidity worldwide, and broadly protective vaccines of defined antigen composition are not yet licensed. Here, we describe the properties of the adhesin complex protein (ACP), which we demonstrate is a newly recognized molecule that is highly conserved and expressed to similar levels in meningococci and facilitates meningococcal interactions with human cells. We also report that a recombinant ACP protein vaccine induces murine antibodies that significantly kill meningococci expressing different ACP. Taken together, these properties demonstrate that ACP merits serious consideration as a component of a broadly protective vaccine against serogroup B meningococci.

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ELISA reactivity of antisera raised against different rACP formulations. Anti-rACP sera were reacted against (A) rACP and (B) MC58 OM. The columns represent the geometric means of reciprocal ELISA titers (n = 5 animals per group), and the error bars show the 95% confidence limits. No reactivity against either rACP or homologous OM was observed with sera from sham immunized animals. NMS, Normal Mouse Serum.
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fig2: ELISA reactivity of antisera raised against different rACP formulations. Anti-rACP sera were reacted against (A) rACP and (B) MC58 OM. The columns represent the geometric means of reciprocal ELISA titers (n = 5 animals per group), and the error bars show the 95% confidence limits. No reactivity against either rACP or homologous OM was observed with sera from sham immunized animals. NMS, Normal Mouse Serum.

Mentions: Purified rACP was used for immunization studies, and murine humoral immune responses were investigated initially by an enzyme-linked immunosorbent assay (ELISA) of rACP (Fig. 2A). High titers of antibodies that reacted with rACP protein were raised using all the different adjuvant and delivery systems. The rACP adsorbed to Al(OH)3 induced statistically higher mean titers (133,000) than rACP in saline solution (22,000), in ZW 3-14 micelles (10,000), or in liposomes (8,600) (P < 0.05). The addition of MonoPhosphoryl Lipid A (MPLA) into ZW 3-14 micelles and liposomes increased mean antibody titers to 49,000 and 41,000, respectively, but these values did not reach statistical significance compared to mixtures without MPLA (P > 0.05). In addition, immunization with MC58 OM on Al(OH)3 also induced antibodies that reacted with rACP (Fig. 2A). All of the antisera raised to formulations containing rACP reacted with ACP present in MC58 OM, but there were no significant differences between the different adjuvant groups (P > 0.05) (Fig. 2B). As expected, significantly higher (P < 0.05) anti-OM antibody titers were induced by immunization with OM than with rACP preparations.


The adhesin complex protein (ACP) of Neisseria meningitidis is a new adhesin with vaccine potential.

Hung MC, Heckels JE, Christodoulides M - MBio (2013)

ELISA reactivity of antisera raised against different rACP formulations. Anti-rACP sera were reacted against (A) rACP and (B) MC58 OM. The columns represent the geometric means of reciprocal ELISA titers (n = 5 animals per group), and the error bars show the 95% confidence limits. No reactivity against either rACP or homologous OM was observed with sera from sham immunized animals. NMS, Normal Mouse Serum.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3585444&req=5

fig2: ELISA reactivity of antisera raised against different rACP formulations. Anti-rACP sera were reacted against (A) rACP and (B) MC58 OM. The columns represent the geometric means of reciprocal ELISA titers (n = 5 animals per group), and the error bars show the 95% confidence limits. No reactivity against either rACP or homologous OM was observed with sera from sham immunized animals. NMS, Normal Mouse Serum.
Mentions: Purified rACP was used for immunization studies, and murine humoral immune responses were investigated initially by an enzyme-linked immunosorbent assay (ELISA) of rACP (Fig. 2A). High titers of antibodies that reacted with rACP protein were raised using all the different adjuvant and delivery systems. The rACP adsorbed to Al(OH)3 induced statistically higher mean titers (133,000) than rACP in saline solution (22,000), in ZW 3-14 micelles (10,000), or in liposomes (8,600) (P < 0.05). The addition of MonoPhosphoryl Lipid A (MPLA) into ZW 3-14 micelles and liposomes increased mean antibody titers to 49,000 and 41,000, respectively, but these values did not reach statistical significance compared to mixtures without MPLA (P > 0.05). In addition, immunization with MC58 OM on Al(OH)3 also induced antibodies that reacted with rACP (Fig. 2A). All of the antisera raised to formulations containing rACP reacted with ACP present in MC58 OM, but there were no significant differences between the different adjuvant groups (P > 0.05) (Fig. 2B). As expected, significantly higher (P < 0.05) anti-OM antibody titers were induced by immunization with OM than with rACP preparations.

Bottom Line: ACP functioned as an adhesin, as demonstrated by reduced adherence of acp knockout (MC58 ΔACP) meningococci to human cells in vitro and the direct surface binding of rACP and by the ability of anti-rACP sera to inhibit adherence of wild-type bacteria.Infections caused by Neisseria meningitidis serogroup B are still significant causes of mortality and morbidity worldwide, and broadly protective vaccines of defined antigen composition are not yet licensed.We also report that a recombinant ACP protein vaccine induces murine antibodies that significantly kill meningococci expressing different ACP.

View Article: PubMed Central - PubMed

Affiliation: Neisseria Research Group, Clinical and Experimental Sciences, Sir Henry Wellcome Laboratories, University of Southampton, Faculty of Medicine, Southampton General Hospital, Southampton, United Kingdom.

ABSTRACT

Unlabelled: The acp gene encoding the 13-kDa adhesin complex protein (ACP) from Neisseria meningitidis serogroup B strain MC58 was cloned and expressed in Escherichia coli, and the purified recombinant ACP (rACP) was used for immunization studies. Analysis of the ACP amino acid sequences from 13 meningococcal strains, isolated from patients and colonized individuals, and 178 strains in the Bacterial Isolate Genome Sequence (BIGS) database showed the presence of only three distinct sequence types (I, II, and III) with high similarity (> 98%). Immunization of mice with type I rACP in detergent micelles and liposomes and in saline solution alone induced high levels of serum bactericidal activity (SBA; titers of 1/512) against the homologous strain MC58 and killed strains of heterologous sequence types II and III with similar SBA titers (1/128 to 1/512). Levels of expression of type I, II, or III ACP by different meningococcal strains were similar. ACP functioned as an adhesin, as demonstrated by reduced adherence of acp knockout (MC58 ΔACP) meningococci to human cells in vitro and the direct surface binding of rACP and by the ability of anti-rACP sera to inhibit adherence of wild-type bacteria. ACP also mediated the invasion of noncapsular meningococci into human epithelial cells, but it was not a particularly impressive invasin, as the internalized bacterial numbers were low. In summary, the newly identified ACP protein is an adhesin that induces cross-strain bactericidal activity and is therefore an attractive target antigen for incorporation into the next generation of serogroup B meningococcal vaccines.

Importance: Infections caused by Neisseria meningitidis serogroup B are still significant causes of mortality and morbidity worldwide, and broadly protective vaccines of defined antigen composition are not yet licensed. Here, we describe the properties of the adhesin complex protein (ACP), which we demonstrate is a newly recognized molecule that is highly conserved and expressed to similar levels in meningococci and facilitates meningococcal interactions with human cells. We also report that a recombinant ACP protein vaccine induces murine antibodies that significantly kill meningococci expressing different ACP. Taken together, these properties demonstrate that ACP merits serious consideration as a component of a broadly protective vaccine against serogroup B meningococci.

Show MeSH
Related in: MedlinePlus