Phenotypic and functional analysis of γδ T cells in the pathogenesis of human T-cell lymphotropic virus type 1 infection.

The human T-cell leukemia virus type 1 (HTLV-1) is the cause of serious malignant and inflammatory diseases, including adult T-cell leukemia and lymphoma and tropical spastic paraparesis. The potential protective role of γδ T cells in HTLV-1 infection remains unclear. Here, demonstrate that there is a decrease in the amount of Vγ9Vδ2 T cells in patients with HTLV-1, especially in those with HTLV-1 associated pathologies. This suggests that γδ T cells could be involved in controlling the virus. Indeed, we found that Vγ9Vδ2 T cells, expanded from non-infected individuals, can kill cells expressing the viral proteins HBZ and Tax and this phenotype is reversed in the presence of mevastatin. Cytotoxicity by Vγ9Vδ2 T cells was not associated with an increase of INF-γ production. In sharp contrast, killing by NK cells was reduced by Tax expression. Thus, our study provides initial evidence for a potential protective role of Vγ9Vδ2 T cells against HTLV-1 infection. Therapeutic exploitation of these insights is feasible with current technologies of T-cell therapies and could provide novel tools to prevent and treat HTLV-1-associated malignancies and neurologic complications.

Protein kinase A is involved in the control of morphology and branching during aerobic growth of Mucor circinelloides.

The cAMP signal transduction pathway controls many processes in fungi. The Mucor circinelloides pkaR and pkaC genes, encoding the regulatory (PKAR) and catalytic (PKAC) subunit of the cAMP-dependent protein kinase A (PKA), have been cloned recently. Expression analysis during the dimorphic shift and colony morphology suggested a role for PKAR in the control of morphology and branching. Here strain KFA121, which overexpresses the M. circinelloides pkaR gene, was used to quantify growth and branching under different aerobic growth conditions in a flow-through cell by computerized image analysis. An inverse relationship between the pkaR expression level in KFA121 and the hyphal growth unit length was observed in KFA121, suggesting a central role for PKAR in branching. A biochemical analysis of PKAR using antibodies and enzyme assay demonstrated that the level of PKAR is higher in KFA121 under inducing conditions, i.e. in the presence of high glucose, than in the vector control strain KFA89. Measurement of cAMP binding demonstrated a significant increase (two- to threefold) in PKAR level for KFA121 at the time of germ-tube emission in medium containing 10 g glucose l(-1). The level of PKA activity was determined using kemptide in the same crude cell extracts used to determine cAMP binding. Strain KFA121 showed a twofold increase in PKA activity. An excess of free PKAR subunit over PKA holoenzyme was determined using sucrose gradient centrifugation of extracts from KFA89 and KFA121. The data indicate that cAMP-dependent PKA in M. circinelloides might be down-regulated during hyphal-tube emergence and that an increase in PKAR levels results in increased branching.