[Multidirectional effect of MIF and sodium polyprenyl phosphate on the course of experimental flavivirus infection in mice].

AIM: Study of macrophage migration inhibiting factor (MIF) effect after intracerebral administration on the course of experimental infection induced in mice by tick borne encephalitis virus (TEV), and study of sodium polyprenyl phosphate (PPP) and/or antibodies against MIF on the course of this infection against the background of MIF administration. MATERIALS AND METHODS: Phosprenil preparation was used as a source of PPP. PPP was administered intracerebrally. MIF--human recombinant (R&D, USA), mice--Balb/c line. RESULTS: In the sera of mice infected with TEV, MIF production stimulation was detected at days 8 through 10 after the infection--against the background of clinical signs presentation of tick borne encephalitis (TE). Administration of PPP to infected mice, on the contrary, resulted in MIF production suppression at the specified period. After administration of 20 ng of MIF to mice, lethality increased by 40% and average life span decreased by 2.3 days. Thus, MIF at high doses caused an increase of infection course severity, induced by TEV in mice, and administration of 60 microg of PPP resulted in the protection from infection in 100% of cases. Intracerebral administrationto mice of antibodies against MIF resulted in a decrease of lethality indicator up to 26% as compared with control and an increase of averagelife span by 5.5 days. During simultaneous administration into the brain of infected mice of MIF, PPP and antibodies against MIF, prevention of MIF-induced increase of TE course severity was registered. CONCLUSION: The data obtained allow to conclude that MIF may serve as an indicator of TE course severity, and possible prognostic indicator of meningo-encephalitic form development in humans.

Control of CD56 expression and tumor cell cytotoxicity in human Vgamma2Vdelta2 T cells.

BACKGROUND: In lymphocyte subsets, expression of CD56 (neural cell adhesion molecule-1) correlates with cytotoxic effector activity. For cells bearing the Vgamma2Vdelta2 T cell receptor, isoprenoid pyrophosphate stimulation leads to uniform activation and proliferation, but only a fraction of cells express CD56 and display potent cytotoxic activity against tumor cells. Our goal was to show whether CD56 expression was regulated stochastically, similar to conventional activation antigens, or whether CD56 defined a lineage of cells committed to the cytotoxic phenotype. RESULTS: Tracking individual cell clones defined by their Vgamma2 chain CDR3 region sequences, we found that CD56 was expressed on precursor cytotoxic T cells already present in the population irrespective of their capacity to proliferate after antigen stimulation. Public T cell receptor sequences found in the CD56+ subset from one individual might appear in the CD56- subset of another donor. The commitment of individual clones to CD56+ or CD56- lineages was stable for each donor over a 1 year interval. CONCLUSION: The ability to express CD56 was not predicted by TCR sequence or by the strength of signal received by the TCR. For gammadelta T cells, cytotoxic effector function is acquired when cytotoxic precursors within the population are stimulated to proliferate and express CD56. Expression of CD56 defines a committed lineage to the cytotoxic phenotype.

Preferential recognition of a microbial metabolite by human Vgamma2Vdelta2 T cells.

Human Vgamma2Vdelta2 T cells are stimulated by prenyl pyrophosphates, such as isopentenyl pyrophosphate (IPP), and play important roles in mediating immunity against microbial pathogens and have potent anti-tumor activity. (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP) has been identified as a metabolite in the 2-C-methyl-D-erythritol-4 phosphate (MEP) pathway for isoprenoid biosynthesis that is used by many bacteria and protozoan parasites. We find that HMBPP is the major Vgamma2Vdelta2 T-cell antigen for many bacteria, including Mycobacterium tuberculosis, Yersinia enterocolitica and Escherichia coli. HMBPP was a 30 000-fold more potent antigen than IPP. Using mutant bacteria, we show that bacterial antigen levels for Vgamma2Vdelta2 T cells are controlled by MEP pathway enzymes and find no evidence for the production of 3-formyl-1-butyl pyrophosphate. Moreover, HMBPP reactivity required only germ line-encoded Vgamma2Vdelta2 TCR elements and is present at birth. Importantly, we show that bacterial HMBPP levels correlated with their ability to expand Vgamma2Vdelta2 T cells in vivo upon engraftment into severe combined immunodeficiency-beige mice. Thus, the production of HMBPP by a microbial-specific isoprenoid pathway plays a major role in determining whether bacteria will stimulate Vgamma2Vdelta2 T cells in vivo. This preferential stimulation by a common microbial isoprenoid metabolite allows Vgamma2Vdelta2 T cells to respond to a broad array of pathogens using this pathway.

Crucial role of TCR gamma chain junctional region in prenyl pyrophosphate antigen recognition by gamma delta T cells.

Human gamma delta T cells recognize prenyl pyrophosphate Ags and their analogues in a V gamma 2V delta 2 TCR-dependent manner. Few data are available regarding the TCR structural requirements for recognition of such prenyl pyrophosphate Ags by gamma delta T cells. Presently, we made chain pair switch, chimeric, and site mutant gamma delta TCRs and transfected them into TCR- mutant Jurkat T cells to examine the effects of changing the TCR gamma junctional region sequences on reactivity to prenyl pyrophosphate Ags. Substitution of the TCR gamma junctional region (N and J) sequences from an Ag-reactive TCR with TCR gamma junctional region sequences from an Ag-nonreactive TCR abrogated reactivity to the prenyl pyrophosphate Ag isopentenyl pyrophosphate and to its synthetic analogue ethyl pyrophosphate but not to a mycobacterial supernatant containing a mixture of prenyl pyrophosphate Ags. Substitution of only the TCR gamma N nucleotide region with that from this Ag-nonreactive TCR destroyed reactivity to isopentenyl pyrophosphate and to the mycobacterial supernatant. Substitution of the entire V delta 2 chain from the Ag-reactive TCR with a V delta 1 chain from an Ag-nonreactive TCR yielded a prenyl pyrophosphate Ag-nonreactive TCR. Thus, using TCR mutagenesis and TCR transfectants, we show that gamma delta TCR reactivity to prenyl pyrophosphate Ags is dependent upon the junctional region of the TCR gamma chain and upon pairing of V gamma 2 and V delta 2 TCR chains. These structural requirements of TCR gamma delta recognition of prenyl pyrophosphates distinguish this reactivity from that of protein superantigens and emphasize the importance of the TCR gamma CDR3 loop and adjacent residues.