Antibody-Induced Internalization of the Human Respiratory Syncytial Virus Fusion Protein.

Respiratory syncytial virus (RSV) infections remain a major cause of respiratory disease and hospitalizations among infants. Infection recurs frequently and establishes a weak and short-lived immunity. To date, RSV immunoprophylaxis and vaccine research is mainly focused on the RSV fusion (F) protein, but a vaccine remains elusive. The RSV F protein is a highly conserved surface glycoprotein and is the main target of neutralizing antibodies induced by natural infection. Here, we analyzed an internalization process of antigen-antibody complexes after binding of RSV-specific antibodies to RSV antigens expressed on the surface of infected cells. The RSV F protein and attachment (G) protein were found to be internalized in both infected and transfected cells after the addition of either RSV-specific polyclonal antibodies (PAbs) or RSV glycoprotein-specific monoclonal antibodies (MAbs), as determined by indirect immunofluorescence staining and flow-cytometric analysis. Internalization experiments with different cell lines, well-differentiated primary bronchial epithelial cells (WD-PBECs), and RSV isolates suggest that antibody internalization can be considered a general feature of RSV. More specifically for RSV F, the mechanism of internalization was shown to be clathrin dependent. All RSV F-targeted MAbs tested, regardless of their epitopes, induced internalization of RSV F. No differences could be observed between the different MAbs, indicating that RSV F internalization was epitope independent. Since this process can be either antiviral, by affecting virus assembly and production, or beneficial for the virus, by limiting the efficacy of antibodies and effector mechanism, further research is required to determine the extent to which this occurs in vivo and how this might impact RSV replication.IMPORTANCE Current research into the development of new immunoprophylaxis and vaccines is mainly focused on the RSV F protein since, among others, RSV F-specific antibodies are able to protect infants from severe disease, if administered prophylactically. However, antibody responses established after natural RSV infections are poorly protective against reinfection, and high levels of antibodies do not always correlate with protection. Therefore, RSV might be capable of interfering, at least partially, with antibody-induced neutralization. In this study, a process through which surface-expressed RSV F proteins are internalized after interaction with RSV-specific antibodies is described. One the one hand, this antigen-antibody complex internalization could result in an antiviral effect, since it may interfere with virus particle formation and virus production. On the other hand, this mechanism may also reduce the efficacy of antibody-mediated effector mechanisms toward infected cells.

Effects of interactions among wave aberrations on optical image quality.

Wave aberrations degrade the optical quality of the eye relative to the diffraction limit, but there are situations in which having slightly aberrated optics can provide some relative visual benefits. This fact led us to consider whether interactions among aberrations in the eye's wavefront produce an advantage for image quality relative to wavefronts with randomized combinations of aberrations with the same total RMS error. Total ocular wave aberrations from two experimental groups and corneal wave aberrations from one group were measured and expressed as Zernike polynomial expansions through the seventh-order. In a series of Monte Carlo simulations, modulation transfer functions (MTFs) for the measured wave aberrations were compared to distributions of artificial MTFs for wavefronts created by randomizing the sign or orientation of the aberrations, while maintaining the RMS error within each Zernike order. In a control condition, "synthetic" model eyes were produced by choosing each individual aberration term at random from individuals in the experimental group, and again MTFs were compared for original and randomized signs. Results were summarized by the MTF ratio: real MTF/mean simulated MTF, as a function of spatial frequency. For a 6mm pupil, the mean MTF ratio for total ocular aberrations was greater than 1.0 up to 60 cycles per degree, suggesting that the eye's aberrations are not independent and that there may be a positive functional consequences to their interrelations. This positive relation did not hold for corneal aberrations alone, or for the synthetic eyes.

Age-related changes in monochromatic wave aberrations of the human eye.

PURPOSE: To investigate the relations between age and the optical aberrations of the whole eye. The eye's optical quality, as measured by the modulation transfer function (MTF), degrades with age, but the MTF does not provide a means to assess the contributions of individual aberrations, such as coma, spherical aberration, and other higher order aberrations to changes in optical quality. The method used in this study provides measures of individual aberrations and overall optical quality. METHODS: Wave aberrations in 38 subjects were measured psychophysically using a spatially resolved refractometer. Data were fit with Zernike polynomials up to the seventh order to provide estimates of 35 individual aberration terms. MTFs and root mean square (RMS) wavefront errors were calculated. Subjects ranged in age from 22.9 to 64.5 years, with spherical equivalent corrections ranging from +0.5 to -6.0 D. RESULTS: Overall RMS wavefront error (excluding tilts, astigmatism, and defocus) was significantly positively correlated with age (r = 0.33, P = 0.042). RMS error for the highest order aberrations measured (fifth through seventh order) showed a strong positive correlation with age (r = 0.57, P = 0.0002). Image quality, as quantified by the MTF, also degraded with age. CONCLUSIONS: Wave aberrations of the eye increase with age. This increase is consistent with the loss of contrast sensitivity with age observed by other investigators.

ON and OFF S-cone pathways have different long-wave cone inputs.

Three experiments compared thresholds for S-cone increments and decrements under steady and transient adaptation conditions, to investigate whether stimuli of both polarities are detected by the same cone-opponent psychophysical mechanism. The results could not be accounted for by a standard model of the S-cone detection pathway [Polden & Mollon (1980) Proceedings of the Royal Society of London, B, 210, 235-272]. In particular, a transient tritanopia detection paradigm that measured threshold elevation following the offset of long-wavelength fields produced different field sensitivities for S-cone increment and decrement tests. The decrement field sensitivity function was shifted to shorter wavelengths relative to the increment function. L-cone opponency is apparently stronger for S-cone increments than for decrements. The most plausible substrates of the two different psychophysical detection mechanisms are the ON and OFF channels. The results suggest that S-ON (bistratified) and S-OFF ganglion cells receive different relative amounts of L- and M-cone input.

Cadmium-its in vivo detection in man.

Neutron capture gamma-ray analysis has been applied to the in vivo detection of Cd in man. The technique was designed for the screening of industrial workers at risk. The limit of sensitivity in a liver-sized phantom is 0-5 ppm for a dose of 0-4 rad. Reproducibility and the effects of positional uncertainties have been investigated. A number of cadavers were studied to establish normal limits prior to commencement of a programme of clinical investigation. A patient with known Cd poisoning was estimated to contain 65-110 ppm of Cd in his liver. A liver dose of 0-05 rad was required.

Measurement of liver-cadmium concentrations in patients and industrial workers by neutron-activation analysis.

A new, rapid, non-invasive technique for measuring tissue-cadmium concentrations in patients and industrial workers has been designed and developed with a view to studying the cadmium content of the liver. The method utilises the principle of neutron-activation analysis whereby the specific changes produced by the inter action of nuclei and neutrons are analysed. Liver-cadmium content has been studied in cadavers and in four men with known of suspected cadmium poisoning. The patients all showed very high liver-cadmium levels of between 35 and 200 p.p.m. compared with under 1.0 p.p.m. in non-exposed subjects. The dose of radiation used in clinical studies was 0.4-1.0 rem and the detection limit of cadmium was 1.0 p.p.m.

Measurement of dietary cadmium absorption in humans.

Total body counting was used to determine cadmium absorption in 14 healthy subjects and in 1 patient with an ileostomy. Breakfast was extrinsically tagged with 115mCdCl2, and a poorly absorbed marker, 51CrCl3, was added to determine the point of complete elimination of unabsorbed radiocadmium from the gastrointestinal tract. The 51Cr was not an ideal marker: fecal excretion of radiocadmium continued beyond the point at which chromium was completely eliminated from the body, Nevertheless, it was helpful in six subjects in identifying the presence of unabsorbed radiocadmium still in transit in the lumen of the gastrointestinal tract 3--5 wk after the test meal. The average body retention of radiocadmium determined between 7 and 14 d after the disappearance of the chromium marker from the body was 4.6 +/- 4.0% (SD), with a range of 0.7--15.6%. The biological half-time of absorbed radiocadmium in one of the subjects was 100 d.

Increased dietary cadmium absorption in mice and human subjects with iron deficiency.

In mice fed a low iron diet, the addition of low levels of cadmium chloride (10 micrometer) to the drinking water impaired growth and accentuated the development of anemia. Cadmium had no effect on mice given a similar diet supplemented with iron. Iron deficiency increased the concentration of cadmium in the duodenal mucosa, the transfer of cadmium to the body from the intestinal tract, and the deposition of absorbed cadmium in the kidneys. In human subjects, the average absorption of 25 microgram of cadmium, labeled with 115mCd, from a test meal was 8.9 +/- 2.0% (mean +/- SE) in 10 people with low body iron stores (serum ferritin less than 20 ng per ml) and 2.3 +/- 0.3% in 12 subjects with normal iron stores (serum ferritin greater than 23 ng per ml). The biological half-time of the radiocadmium in 3 of the subjects ranged from 90 to 202 days. Thus, the intestinal adaptive response to iron deficiency in both experimental animals and human subjects leads to the increased absorption of cadmium, a potentially toxic element.