Research on Late-Cycle Chlamydial Gene ExpressionGeneral

Ms Gugu Mzobe.Ms Gugu Mzobe.

Mid and late-cycle chlamydial gene expression levels are different to the published research conducted in HeLa cells at 37degC, a UKZN doctoral study found.

Presenting her findings at the College of Health Sciences Research Symposium, Ms Gugu Mzobe said the study also found that ‘temperature has an effect on the level of gene chlamydial gene expression when grown in keratinocytes (human skin cells)’.

Titled: “Temporal Gene Expression of Chlamydia Trachomatis in Keratinocytes at 37degC Versus 33degC”, the study aimed to investigate chlamydial gene expression in a keratinocyte cell line at both core (37°C) and skin (33°C) temperature in an attempt to understand what happens in vivo.

Mzobe looked at the changes in gene expression associated with chlamydial differentiation and replication in human skin cells at 37degC (temperature of the inguinal lymph nodes) and 33degC (temperature of human skin. Keratinocytes are the first port of entry for Chlamydia trachomatis of the lymphogranuloma venereum (LGV) biovar which causes LGV. LGV is an invasive, sexually transmitted disease of humans which begins as an ulcer in the genital region. 

‘LGV penetrates the breaks in the dermis and underlying tissues and migrates to the inguinal lymph nodes where it causes lymphadenopathy,’ Mzobe explained. 

According to Mzobe, this ground breaking study provided powerful findings about gene products that regulate the different stages of the chlamydial developmental cycle in keratinocytes.

‘This is the first study to investigate chlamydial gene expression in keratinocytes, which are the first target of infection for organisms of the LGV biovar,’ she declared.

The study showed a different pattern of expression to that which occurs in HeLa or Hep2 cell lines which are the cell line most commonly used for chlamydial gene expression studies.  This was the case even though these are not the wild type host LGV pathogenesis and gene expression studies are usually performed in cells which are not the native host cells, ‘The initial site of infection, the skin, and the secondary site of infection, the inguinal lymph nodes, have different temperatures,’  she said.

The temperature of human skin is 33degC, while the temperature of the inguinal lymph nodes is 37degC.  She said previous studies have only focused on the latter temperature – 37degC. 

‘Joubert and Sturm (2011) have demonstrated that C. trachomatis does infect keratinocytes in vitro both at 37degC and 33degC, although they replicate much faster at 37degC than at 33degC,’ she stated.

She said the model was used to investigate changes in gene expression associated with chlamydial differentiation and replication in keratinocytes at 37degC and 33degC.

The lab based study was performed on adult human skin cells (HaCaT cells), chlamydial reference strain (L2), clinical isolate from patients presenting in the primary stage of LGV at the Prince Cyril Zulu Communicable Diseases Clinic in Durban. E strain was isolated by Maleka and coworkers (1996) in the laboratory from a male patient presenting at the same clinic with urethritis.

Mzobe, a PhD student in the School of Laboratory Medicine and Medical Sciences under the Discipline of Medical Microbiology and Infection Control, is currently working on her thesis.

Born in Ndwedwe, Mzobe loves research and it keeps her going. ‘I’m the first grandchild at home to go to university. My grandmother and my late grandfather were always a great inspiration for me to go this far with my studies.’

Nombuso Dlamini