Expression of human T-cell leukemia virus type 1 (HTLV-1) is regulated both by the HTLV-1 Tax transactivator and by cellular transcriptional factors binding to the viral long terminal repeat (LTR), suggesting that cellular signals may play a role in regulating viral expression. Treatment of cells chronically infected with HTLV-1, which express low levels of HTLV-1 RNAs and Tax protein, with phorbol esters (i.e., phorbol12-myristate 13- acetate [PMA]), phytohemagglutinin (PHA), sodium butyrate, or combinations of cytokines resulted in induction of HTLV- 1 gene expression. PMA or PHA treatment following cotransfection of HTLV-1 Tax expression plasmids resulted in synergistic activation of HTLV-1 LTR-directed gene expression, apparently involving tyrosine ki- nase- mediated pathways. These results suggest that cellular activation stimuli may cooperate with HTLV-1 Tax to enhance expression of integrated HTLV-1 genomes and thus may play a role in the pathogenesis of HTLV-1 disease.

Background

This study aimed to analyze the clinical features, causative pathogens, neuro-imaging findings, and therapeutic outcomes of bacterial brain abscess in patients with nasopharyngeal carcinoma (NPC) following radiotherapy.

Methods

NPC patients with bacterial brain abscess were evaluated. Their clinical data were collected over a 22-year period. For comparison, the clinical features, causative pathogens, neuro-imaging findings, and therapeutic outcomes between NPC and non-NPC patients were analyzed.

Results

NPC accounted for 5.7% (12/210) of the predisposing factors, with Viridans streptococci and Staphylococcus aureus as the two most common causative pathogens. Significant statistical analysis between the two groups (NPC and non-NPC patients) included chronic otitis media (COM) as the underlying disease, post-radiation necrosis by neuro-imaging, and the temporal lobe as the most common site of brain abscesses. The fatality rate in patients with and without NPC was 16.7% and 20.7%, respectively.

Conclusions

NPC patients with bacterial brain abscess frequently have COM as the underlying disease. Neuro-imaging often reveals both post-radiation necrosis and the temporal lobe as the most common site of brain abscesses, the diagnosis of which is not always a straightforward process. Radiation necrosis can mimic brain abscess on neuro-imaging and pose significant diagnostic challenges. Early diagnosis and treatment is essential for survival.