Asplenic individuals are known to be at increased risk of infection with encapsulated bacteria. Recent United Kingdom recommendations stated that this at-risk group should receive one dose of the meningococcal serogroup C conjugate (MCC) vaccine. However, the immune response of asplenic individuals to MCC vaccine is unknown. The immune response of asplenics (n ‫؍‬ 130) to immunization with the MCC vaccine was investigated. Asplenic individuals had a significantly lower geometric mean titer (GMT) (157.8; 95% confidence interval [CI], 94.5 to 263.3) of bactericidal antibody in serum (SBA) than an age-matched control group (n ‫؍‬ 48) (1448.2; 95% CI, 751.1 to 2792.0). However, 80% of asplenic individuals achieved the proposed protective SBA titer of >8. No differences were observed between the two groups in the serogroup C-specific immunoglobulin G geometric mean concentration. A significant reduction in SBA GMT or the number of responders achieving an SBA titer of >8 was observed if the reason for splenectomy was a medical cause or if MCC vaccination occurred <10 years after splenectomy. Individuals (n ‫؍‬ 29) who did not achieve an SBA titer of >16 were offered a second dose of MCC vaccine. Analysis of the SBA response revealed that 61% (14 of 23) of the individuals who received a second dose achieved a protective titer. In total, 93% of asplenic individuals achieved a titer of >8 following MCC vaccination (one or two doses combined). We recommend that, following vaccination of asplenics, either the level of functional antibody should be determined, with a second dose of MCC vaccine offered to nonresponders, or two doses of MCC vaccine should be routinely offered.Asplenic individuals are at an increased risk of infection from encapsulated bacteria, including Neisseria meningitidis (9, 15). Overwhelming postsplenectomy infection has a high mortality rate, between 40% and 70% (7). Immunization with the 23-valent pneumococcal plain polysaccharide and Haemophilus influenzae type b (Hib) conjugate (29) vaccines is recommended for individuals with functional or anatomic asplenia. In 2001, the United Kingdom Department of Health extended this recommendation to include vaccination with meningococcal serogroup C conjugate (MCC) vaccine, although no data on immune responses are available to date for MCC vaccines in this group (6).Various studies have provided conflicting evidence on the immune response to polysaccharide antigens in asplenic individuals (12, 21), and the limitations of plain polysaccharide vaccines are well documented (13,17,18,29). Meningococcal serogroup C plain polysaccharide vaccines are not immunogenic in those under the age of 2 years (13, 17), and repeated doses can lead to hyporesponsiveness (2,13,18,29). MCC vaccines that have been shown to be highly immunogenic and to generate immune memory in all age groups from infants to adults are now available (10, 25-29). MCC vaccines have been shown to be efficacious in all the age groups targeted during the vaccination campaign initiated in 1999 in the Uni...

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Phage display is the most widely used method for selecting binding molecules from recombinant antibody libraries. However, validation of the phage antibodies often requires early production of the cognate full-length immunoglobulin G (IgG). The conversion of phage library outputs to a full immunoglobulin via standard subcloning is time-consuming and limits the number of clones that can be evaluated. We have developed a novel system to convert scFvs from a phage display vector directly into IgGs without any in vitro subcloning steps. This new vector system, named pMINERVA, makes clever use of site-specific bacteriophage integrases that are expressed in E. coli and intron splicing that occurs within mammalian cells. Using this system, a phage display vector contains both bacterial and mammalian regulatory regions that support antibody expression in E. coli and mammalian cells. A single-chain variable fragment (scFv) antibody is expressed on the surface of bacteriophage M13 as a genetic fusion to the gpIII coat protein. The scFv is converted to an IgG that can be expressed in mammalian cells by transducing a second E. coli strain. In that strain, the phiC31 recombinase fuses the heavy chain constant domain from an acceptor plasmid to the heavy chain variable domain and introduces controlling elements upstream of the light chain variable domain. Splicing in mammalian cells removes a synthetic intron containing the M13 gpIII gene to produce the fusion of the light chain variable domain to the constant domain. We show that phage displaying a scFv and recombinant IgGs generated using this system are expressed at wild-type levels and retain normal function. Use of the pMINERVA completely eliminates the labor-intensive subcloning and DNA sequence confirmation steps currently needed to convert a scFv into a functional IgG Ab.