Rickettsia typhi (formerly named Rickettsia mooseri) is a Gram negative,
obligate intracellular bacteria. It is the causative agent of murine typhus or endemic
typhus, which has a worldwide distribution, especially in tropical countries. The main
vector of murine typhus is Xenopsylla cheopis, a rat flea which maintains Rickettsia
typhi in rodents.
Many studies have revealed that bacterial S-layers play many roles such as a
protective coat, a molecular sieve or as a structure involved in cell adhesion and
surface recognition. Rickettsia typhi also posses the S–layers externally to the outer
membrane as encoded by slpT gene, which is translated into Crystalline Surface layer
protein (SLP). In 1996 Hahn and Chang characterized the SlpT protein of Rickettsia
typhi as the protective antigen against murine typhus and also found that it reacted
strongly with antiserum of patient with murine typhus.
The purpose of this research is to select a part of SlpT of Rickettsia typhi to be
cloned. A 400bps piece of SlpT gene encoded for a 10.2 kDa recombinant protein was
cloned. After expression and the purification process, this 10.2 kDa protein was
examined for antigenicity with murine typhus positive antiserum. The final result
showed that this part of SlpT didn’t have enough antigenicity to give a positive
reaction with murine typhus antiserum.