The clonality of a random sample of 102 invasive pneumococcal serotype 3 strains isolated from Gauteng Province during January 2000 to December 2003 was investigated. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) revealed a heterogeneous population with several PFGE clusters and sequence types (STs). The largest PFGE cluster comprised 36/102 (35%) isolates including seven that belonged to ST458, a clone that is not common in other parts of the world. The global clone (ST180) which is common in the United States and other countries was found in a cluster that represented only 14/102 (14%) of isolates examined. The first multidrug-resistant pneumococcal serotype 19A strain that was isolated in South Africa in 1977 was compared with invasive serotype 19A multidrug-resistant strains isolated in South Africa during June 1999 to December 2004. PFGE analysis of these isolates demonstrated clonal diversity among the isolates. MLST of 16 randomly selected isolates revealed several STs, none of which was the same ST as the 1977 clone. Both serotype 3 and 19A were not associated with increased mortality or HIV seropositivity compared to other serotypes.

The aim of this investigation was to clone, characterize and express the gene that encodes the outer capsid protein, VP2, of African horsesickness virus (AHSV), with a view to the evaluation of this protein as a subunit vaccine. The VP2 gene of AHSV serotype 3 (AHSV-3) was cloned as incomplete cDNA fragments of the genome segment 2 double-stranded (ds)RNA, sequenced in its entirety and compared with previously published cognate sequences of AHSV-4, Epizootic hemorrhagic disease virus (EHDV)-l and various bluetongue virus (BTV) serotypes. AHSV-3 genome segment 2 was shown to be 3221 nucleotides in length, encoding a protein of 1057 amino acids with a 50.5% identity to AHSV-4 VP2. Two areas of high variability (approximately 65%) were identified adjacent to the conserved termini. The N-proximal region (amino acids 128-309) exhibited significant hydrophilicity, suggesting a possible role in the determination of the serotype-specific immune response. Orbivirus interserogroup comparisons of VP2 amino acid sequences revealed extreme variability, although an overall structural conservation was demonstrated. Oligonucleotide primers derived from the AHSV-3 genome segment 2 terminal nucleotide sequences were used for PCR amplification and cloning of full length segment 2 cDNA. The cloned gene was expressed in a baculovirus expression system and the expressed VP2 protein was shown to react specifically with anti AHSV-3 serum in Western blots. Although the yields of VP2 in the baculovirus system were low, due to a possible toxic effect on the host cells, sufficient antigen was obtained for further future investigations into the efficacy of VP2 as a possible subunit vaccine against AHSV. / Dissertation (MSc)--University of Pretoria, 2010. / Genetics / unrestricted