Fragment of tegument protein pp65 of human cytomegalovirus induces autoantibodies in BALB/c mice.

INTRODUCTION: Human cytomegalovirus (HCMV) infection has been implicated in the development of autoimmunity, including systemic lupus erythematosus (SLE). Previously we reported that HCMV phosphoprotein 65 (pp65) could induce early onset of autoantibody and glomerulonephritis on lupus-prone NZB/W mice. This study further examined whether the B cell epitope(s) in pp65 is able to drive the development of autoantibody. METHODS: Sera from SLE patients or HCMVpp65-immunized mice were analyzed for anti-nuclear antibody by immunoblotting, enzyme-linked immunosorbent assay (ELISA), immunofluorescent stain and Crithidia luciliae stain. The deposition of immunoglobulin to the kidney was also examined by immunofluorescent stain. The interactions between pp65 sub-fragment to cellular proteins were revealed by yeast two-hybrid analyses. RESULTS: Our results showed that most SLE patients possessed antibodies to the C-terminal half of the HCMVpp65 antigen. Of these positive sera, 73% were also positive to the pp65336-439 sub-fragment. The immunization of pp65336-439 induced formation of multiple anti-nuclear antibodies, including anti-chromatin, anti-centriole, anti-mitotic spindle type I/II (MSA I/II) and a significant elevation of anti-double-stranded DNA (anti-dsDNA) antibodies on BALB/c mice. Yeast two-hybrid analyses revealed the binding of pp65336-439 sub-fragment to cellular proteins. Immunoglobulin deposition on glomeruli was also detected on pp65336-439-immunized mice. CONCLUSIONS: Our data suggested that HCMVpp65336-439 sub-fragment may induce cross-reactive antibodies to several nuclear antigens, which could contribute to the development of autoimmunity in genetic-suspected individuals.

Early infection termination affects number of CD8+ memory T cells and protective capacities in listeria monocytogenes-infected mice upon rechallenge.

Here, we reevaluate the effects of early termination of infection on primary T cell expansion, subsequent memory cell development, and protective immunity. Using a murine Listeria monocytogenes (LM) infection model, we found the primary expansions of both CD4(+) and CD8(+) T cells were affected even when ampicillin was given as late as 60 h postinfection (p.i.). Subsequent development of CD8(+) memory T cells was also impaired, although to a lesser extent, and only mice that received ampicillin at 24 h p.i. revealed a significant decrease in memory CD8(+) T cells. Upon rechallenge with 1 x 10(5) CFU of LM, all ampicillin-treated mice cleared LM as effectively, and they generated similar amounts of Ag-specific CD8(+) T cells as with untreated mice. However, mice that received ampicillin at 24 h p.i. lost their protective abilities when rechallenged with 7.5 x 10(5) CFU of LM. Ampicillin treatment also revealed early down-regulation of B7.1 and B7.2, but not CD40, on dendritic cells 72 h p.i. Our results have several important implications: 1) they argue against the hypothesis that brief exposure of T cells to an Ag is sufficient for full-fledged primary T cell responses and subsequent memory T cell development in vivo; 2) they suggest the existence of a reservoir of memory T cells, more than the immune system can possibly expand during secondary infection; and 3) they suggest that protective capacity is correlated with the number of preexisting memory T cells and that secondary expanding T cells play a limited role, at least in murine LM infection.

Characterization of early gamma interferon (IFN-gamma) expression during murine listeriosis: identification of NK1.1+ CD11c+ cells as the primary IFN-gamma-expressing cells.

Though it is well established that gamma interferon (IFN-gamma) is crucial to the early innate defense of murine listeriosis, its sources remain controversial. In this study, intracellular cytokine staining of IFN-gamma-expressing splenocytes early after Listeria monocytogenes infection revealed that NK1.1(+), CD11c(+), CD8(+) T, and CD4(+) T cells expressed IFN-gamma 24 h after infection. Contrary to the previous report, most IFN-gamma(+) dendritic cells (DC) were CD8alpha(-) DC. Unexpectedly, almost all CD11c(+) IFN-gamma-expressing cells also expressed NK1.1. These NK1.1(+) CD11c(+) cells represented primary IFN-gamma-expressing cells after infection. In situ studies showed these NK1.1(+) CD11c(+) cells were recruited to the borders of infectious foci and expressed IFN-gamma. A significant NK1.1(+) CD11c(+) population was found in uninfected spleen, lymph node, blood, and bone marrow cells. And its number increased significantly in spleen, lymph node, and bone marrow after L. monocytogenes infection. Using interleukin-12 (IL-12) p40(-/-) mice, IFN-gamma expression was found to be largely IL-12 p40 dependent, and the number of IFN-gamma-expressing cells was only about one-third of that of wild-type mice. Moreover, the IFN-gamma expression was absolutely dependent on live L. monocytogenes infection, as no IFN-gamma was detected after inoculation of heat-killed L. monocytogenes. Our findings not only provide an insight into IFN-gamma expression after in vivo infection but may also change the current perceptions of DC and natural killer cells.

Visible-light-induced bactericidal activity of a nitrogen-doped titanium photocatalyst against human pathogens.

The antibacterial activity of photocatalytic titanium dioxide (TiO(2)) substrates is induced primarily by UV light irradiation. Recently, nitrogen- and carbon-doped TiO(2) substrates were shown to exhibit photocatalytic activities under visible-light illumination. Their antibacterial activity, however, remains to be quantified. In this study, we demonstrated that nitrogen-doped TiO(2) substrates have superior visible-light-induced bactericidal activity against Escherichia coli compared to pure TiO(2) and carbon-doped TiO(2) substrates. We also found that protein- and light-absorbing contaminants partially reduce the bactericidal activity of nitrogen-doped TiO(2) substrates due to their light-shielding effects. In the pathogen-killing experiment, a significantly higher proportion of all tested pathogens, including Shigella flexneri, Listeria monocytogenes, Vibrio parahaemolyticus, Staphylococcus aureus, Streptococcus pyogenes, and Acinetobacter baumannii, were killed by visible-light-illuminated nitrogen-doped TiO(2) substrates than by pure TiO(2) substrates. These findings suggest that nitrogen-doped TiO(2) has potential application in the development of alternative disinfectants for environmental and medical usages.