In bacteria, the intracellular levels of metals are mediated by tightly controlled acquisition and efflux systems. This is particularly true of copper, a trace element that is universally toxic in excess. During infection, the toxic properties of copper are exploited by the mammalian host to facilitate bacterial clearance. To better understand the role of copper during infection, we characterized the contribution of the cop operon to copper homeostasis and virulence in Streptococcus pneumoniae. Deletion of either the exporter, encoded by copA, or the chaperone, encoded by cupA, led to hypersensitivity to copper stress. We further demonstrated that loss of the copper exporter encoded by copA led to decreased virulence in pulmonary, intraperitoneal, and intravenous models of infection. Deletion of copA resulted in enhanced macrophage-mediated bacterial clearance in vitro. The attenuation phenotype of the copA mutant in the lung was found to be dependent on pulmonary macrophages, underscoring the importance of copper efflux in evading immune defenses. Overall, these data provide insight into the role of the cop operon in pneumococcal pathogenesis.

We have been studying the effects of tobacco glycoprotein (TGP), a polyphenol-rich glycoprotein isolated from cured tobacco leaves, on the immune system. We have shown previously that mice immunized with TGP produce preferentially antibodies of the IgE isotype and that TGP is a T cell-independent B cell mitogen for mice, which stimulates B cell proliferation and B cell differentiation into Ig-secreting cells. We report herein that TGP stimulates a significant increase in [3H]TdR incorporation by human PBL and by human cord blood lymphocytes. The magnitude of the proliferative response of PBL to TGP does not correlate with the donor's titer of IgE antibodies to TGP, as assayed by a wheal and flare response after an i.d. injection of TGP, neither does it correlate with the donor's smoking history. [3H]TdR uptake is not observed before day 5 of culture, and the response peaks between days 5 and 10 of culture. Analysis of the cellular basis for the proliferative response suggests that T cells are proliferating. Two-parameter analysis by flow cytometry shows that CD3+, CD4+, and CD8+ cells are in the S + G2 + M phases, but not Ig-bearing cells or monocytes. A significant increase in HLA-DR (Ia)-bearing cells is observed on cells in all of the cell cycle phases. This increase coincides with cells entering the S phase. No increase is observed in the expression of the IL-2-R as assayed by the anti-Tac antibody. TGP also stimulates human PBL to differentiate and to produce Ig of the IgM, IgG, and IgA isotypes, without stimulating a detectable B cell proliferative response. The proliferative response of PBL is clearly due to TGP and not to contamination with LPS, because by the limulus amebocyte assay the TGP preparation contains less than 2% LPS, which could not account for the stimulation observed.