Ultra-Violet Light Emission from HPV-G Cells Irradiated with Low Let Radiation From 90Y; Consequences for Radiation Induced Bystander Effects

In this study, we aimed to establish the emission of UV photons when HPV-G cells and associated materials (such as the cell substrate and cell growth media) are exposed to low LET radiation. The potential role of UV photons in the secondary triggering of biological processes led us to hypothesize that the emission and absorption of photons at this wavelength explain some radiation induced “bystander effects” that have previously been thought to be chemically mediated. Cells were plated in Petri-dishes of two different sizes, having different thicknesses of polystyrene (PS) substrate, and were exposed to β-radiation from ⁹⁰Y produced by the McMaster Nuclear Reactor. UV measurements were performed using a single photon counting system employing an interference-type filter for selection of a narrow wavelength range, 340±5 nm, of photons. Exposure of the cell substrates (which were made of polystyrene) determined that UV photons were being emitted as a consequence of β particle irradiation of the Petri-dishes. For a tightly collimated β-particle beam exposure, we observed 167 photons in the detector per unit μCi in the shielded source for a 1.76 mm thick substrate and 158 photons/μCi for a 0.878 mm thick substrate. A unit μCi source activity was equivalent to an exposure to the substrate of 18 β-particles/cm² in this case. The presence of cells and medium in a Petri-dish was found to significantly increase (up to a maximum of 250%) the measured number of photons in a narrow band of wavelengths of 340±5 nm (i.e. UVA) as compared to the signal from an empty control Petri-dish. When coloured growth medium was added to the cells, it reduced the measured count rate, while the addition of transparent medium in equal volume increased the count rate, compared to cells alone. We attribute this to the fact that emission, scattering and absorption of light by cells and media are all variables in the experiment. Under collimated irradiation conditions, it was observed that increasing cell density in medium of fixed volume resulted in a decrease in the observed light output. This followed a roughly exponential decline. We suggest that this may be due to increased scattering at the cell boundary and absorption of the UV in the cells. We conclude that we have measured UVA emitted by cells, cell medium and cell substrates as a consequence of their irradiation by low LET β-particle radiation. We suggest that these secondary UV photons could lead to effects in non-targetted cells. Some effects that had previously been attributed to a chemically mediated “bystander effect” may in fact be due to secondary UV emission. Some radiation bystander effect studies may require re-interpretation as this phenomenon of UV emission is further investigated.     

A Qualitative Analysis of Vaccine Safety Perceptions and Concerns Among Caretakers in Uganda

Parents and caretakers of young children often have concerns about vaccine safety and adverse events following immunization (AEFI). Little is known about vaccine safety perceptions in Uganda and their influence on parental decision-making about infant immunization. The study objectives were: to identify community sources of information on immunization, vaccine safety and AEFI; determine caretakers?? knowledge of immunization; identify community concerns/fears about immunization and AEFI and their influence on caretakers?? decisions to vaccinate; and obtain an understanding of knowledge, perceptions, and experience of health care workers (HCWs) and policy administrators on vaccine safety and AEFI. Twelve focus group discussions with 136 caretakers who were very or somewhat concerned about vaccine safety and 25 key informant interviews were conducted in two districts (1 urban and 1 rural) with district authorities and health facility staff as well as national level decision-makers between December and April 2006. Content analysis was used to analyze the results. The main themes identified related to general lack of information among caretakers about immunization, perceived immunization benefits, immunization concerns, and misconceptions. Specific caretaker concerns related to vaccine administration, immunization services and vaccine safety. Experiences with AEFI and concerns about vaccine safety negatively affected caretakers?? decisions to vaccinate their children, notably in rural areas. HCWs demonstrated knowledge about AEFI and their management although incidences reported to facilities were rare. Inadequate communication between HCWs and caretakers was noted. Concerns and misconceptions about vaccination still exist among caretakers in Uganda and influence decisions to vaccinate. Effective inter personal communication initiated by HCWs towards caretakers is needed.     

Kinetics of Epstein-Barr Virus (EBV) Neutralizing and Virus-Specific Antibodies after Primary Infection with EBV

Prospective studies of antibodies to multiple Epstein-Barr virus (EBV) proteins and EBV neutralizing antibodies in the same individuals before, during, and after primary EBV infection have not been reported. We studied antibody responses to EBV in college students who acquired primary EBV infection during prospective surveillance and correlated the kinetics of antibody response with the severity of disease. Neutralizing antibodies and enzyme-linked immunosorbent assay (ELISA) antibodies to gp350, the major target of neutralizing antibody, reached peak levels at medians of 179 and 333 days after the onset of symptoms of infectious mononucleosis, respectively. No clear correlation was found between the severity of the symptoms of infectious mononucleosis and the peak levels of antibody to individual viral proteins or to neutralizing antibody. In summary, we found that titers of neutralizing antibody and antibodies to multiple EBV proteins increase over many months after primary infection with EBV.