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The majority of HIV infected individuals fail to produce protective antibodies and have diminished responses to immunization1–3. We report that even though there is an expansion of T follicular helper (Tfh) cells in HIV infected individuals, these are unable to provide adequate B cell help. A higher frequency of PD-L1+ germinal center (GC) B cells from lymph nodes of HIV infected individuals suggested a potential role for PD-1/PD-L1 interaction in regulating Tfh cell function. In fact, engagement of PD-1 on Tfh cells led to a reduction in cell proliferation, activation, ICOS expression and IL-21 cytokine secretion. Importantly, blocking PD-1 signaling enhanced HIV-specific immunoglobulin production in vitro. We further show that at least part of this defect involves IL-21 as addition of this cytokine rescued antibody responses and plasma cell generation. Our results suggest that deregulation of Tfh-mediated B cell help diminishes B cell responses during HIV infection and may be related to PD-1 triggering on Tfh cells. These results show, for the first time, a role for Tfh cell function in HIV pathogenesis and suggest that an alteration in their function could have a significant impact on the outcome and control of HIV infection, future infections and vaccinations.

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Oxidative stress leads to membrane lipid peroxidation, which yields products causing variable degrees of detrimental oxidative modifications in cells. Reactive oxygen species (ROS) are the key regulators in this process and induce lipid peroxidation in Escherichia coli. Application of nonthermal (cold) plasma is increasingly used for inactivation of surface contaminants. Recently, we reported a successful application of nonthermal plasma, using a floating-electrode dielectric-barrier discharge (FE-DBD) technique for rapid inactivation of bacterial contaminants in normal atmospheric air (S. G. Joshi et al., Am. J. Infect. Control 38:293-301, 2010). In the present report, we demonstrate that FE-DBD plasma-mediated inactivation involves membrane lipid peroxidation in E. coli. Dose-dependent ROS, such as singlet oxygen and hydrogen peroxide-like species generated during plasma-induced oxidative stress, were responsible for membrane lipid peroxidation, and ROS scavengers, such as ␣-tocopherol (vitamin E), were able to significantly inhibit the extent of lipid peroxidation and oxidative DNA damage. These findings indicate that this is a major mechanism involved in FE-DBD plasma-mediated inactivation of bacteria.Nonthermal (cold) dielectric-barrier discharge (DBD) atmospheric-pressure plasma is widely under investigation for use as an alternative sterilization and disinfection method in the fields of biology and medicine. Most recently, we demonstrated that Escherichia coli, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus in both their planktonic form and in biofilms are rapidly inactivated by nonthermal DBD plasma using a floating-electrode technique (11). Complete inactivation of E. coli was seen in less than 120 s when E. coli was present in its planktonic form, and complete inactivation occurred in about 180 s when it was in the biofilm form, making this technique attractive for sterilization processes. E. coli is one of the most common Gram-negative bacterial contaminants responsible for hospital-acquired infections (HAI) and one of the most widely studied organisms in the laboratory and therefore is a good choice to track various oxidative-stress pathways.A DBD plasma-generating probe is an apparatus that generates microsecond-long, high-voltage-pulsed cold plasma between the primary electrode covered with a quartz surface and the surface of the biological sample, which serves as a second electrode. The high-voltage electrode is completely covered with a dielectric barrier, which makes it safe for sterilization applications, and the nature of the applied microsecond pulses do not elevate the surface temperature above 28°C. In the floating-electrode DBD (FE-DBD) plasma setup, the second electrode (biological sample) is not grounded and remains at a floating potential. Discharge ignites when the powered electrode approaches the surface to be treated at a distance (discharge gap) less than about 3 mm, depending on the form, duration, and polarity of the driving voltage, and it is safe to apply...

Thermal plasma discharges have been widely used in the past for treatment of living human and animal tissue. However, extensive thermal damage and tissue desiccation occurs due to extreme temperatures. Some solutions have been offered where the temperature is lowered by short current pulses, addition of noble gases, or significant decrease in the size of treatment electrodes. We propose a method of direct treatment of living tissue that occurs at room temperature and pressure without visible or microscopic tissue damage. The presented Floating-Electrode Dielectric Barrier Discharge plasma is proven electrically safe to human subjects and our results show no gross (visual) or histological (microscopic) damage to skin samples in minutes, complete tissue sterilization from skin flora in seconds, and blood clot formation in seconds of electric plasma treatment. We also observe significant hastening of blood clot formation via electric plasma induced catalysis of "natural" processes occurring in human blood. A model describing these processes is offered.