MOLECULAR CHARACTERIZATION OF IS1301 IN AN EMERGENT CLONE OF SEROGROUP C NEISSERIA MENINGITIDIS
Neisseria meningitidis is a leading cause of invasive meningococcal disease and humans are the only known host. The administration of meningococcal vaccines has reduced the number of meningococcal cases and carriage rates in humans. Current vaccine strategies target important immunological determinants. Insertion sequence 1301 (IS1301) has been shown to facilitate evasion of the host immune response by disrupting antigen expression. The public health importance of this study is in the design of future vaccines against N. meningitidis and in understanding the emergence of new clones.
In the 1990s there was an increase in serogroup C meningococcal disease in Maryland that was associated with antigenic shift at the fetA gene. The isolates were characterized as either an early clone or late clone based on the outer membrane protein sequence profiles. The 2:P1.5,2:F.1-30 sequence profile is classified as an early clone while the 2:P1.5,2:F.3-6 sequence profile is classified as a late clone. Previous studies determined that the late clone contained IS1301, while the early clone did not. The goal of this present study is to characterize the IS1301 insertion sites in the late clone to determine if this genetic element contributed to clonal emergence. Early and late clone isolates were characterized by DNA sequence analysis of the housekeeping gene, fumC. A single nucleotide polymorphism characteristic of the hypervirulent ET-15 clone was identified in the late clone isolates. Southern blot analysis using an IS1301 probe revealed a heterogeneous population with multiple insertion sites, ranging from five to ten insertions, within the serogroup C late clone genomes. Of note was a high molecular weight triplet banding pattern common to the majority of isolates.
Several different IS1301 specific, PCR-based strategies were performed in an attempt to clone the IS1301 elements corresponding to the bands of the IS1301 triplet. In addition, whole genome sequence analysis was performed on one of the late clone isolates. Initial whole genome analysis demonstrates IS1301 integration within an opacity-associated protein (Opa), which promotes adherence to host cells. Further investigations are necessary to determine the effect of IS1301 insertion on antigenic variation.
Advisor:Lee H Harrison; Elodie Ghedin; Jeremy Martinson; Paul Kinchington
School:University of Pittsburgh
School Location:USA - Pennsylvania
Source Type:Master's Thesis
Keywords:infectious diseases and microbiology
Date of Publication:09/28/2008