Respiratory Syncytial Virus Infections in Infants: Detel1ninants of Clinical Severity

In 1955 a virus was isolated by Morris et al. from a chimpanzee with an upper respiratory tract infection. This apparently new virus was originally called chimpanzee coryza agent. Soon aftclwards, when it was isolated from children with respiratory disease, it became clear that this virus was a major human pathogen. The virus was from then onward called respiratory syncytial virus (RSV) because of its ability to caLise respiratory disease and to induce large syncytia in cell culture. RSV is now known as the single most common cause of severe respiratory tract infection in childhood. In fact up to 70% of hospital admissions of infants for respiratory infections during the winter season may be caused by RSV alone. Soon after RSV was found to be a significant cause of morbidity and 1ll00iaiity in childhood the search for a vaccine began. During the sixties a formalin inactivated RSV (FI-RSV) candidate vaccine, known as "lot 100", was developed and administered to children of two to seven years old. This vaccine, in stead of protecting vaccinees against RSV infection, predisposed for more severe disease upon natural infection in the following RSV season. Hospitalization rates were as high as 80% and two of the vaccinces died. At this moment, despite considerable research efforts, no licensed vaccine is available against this important pathogen. Development ofa vaccine against RSV is one of the priorities of the Global Program for Vaccines of the World Health Organization

G protein variation in respiratory syncytial virus group A does not correlate with clinical severity

Respiratory syncytial virus group A strain variations of 28 isolates from The Netherlands collected during three consecutive seasons were studied by ana

Patient-to-patient spread of a single strain of Corynebacterium striatum causing infections in a surgical intensive care unit

Over a 12-month period, Corynebacterium striatum strains were isolated from clinical specimens from 14 patients admitted to a surgical intensive care unit. These isolates were identical by morphology and biotype and displayed the same antibiogram. Ten isolates were found to be the sole possible pathogen. These 10 isolates were from six patients, three of whom had signs of infection at the time of positive culture. Further typing was performed by random amplification of polymorphic DNA analysis, by which all strains were identical and were found to differ to various degrees from reference strains and from isolates found in clinical samples from other wards. In a case-control study the only independent risk factor for acquiring the strain was intubation for longer than 24 h (odds ratio, 20.09; 95

Identification of a common HLA-DP4-restricted T-cell epitope in the conserved region of the respiratory syncytial virus G protein

The cellular immune response to respiratory syncytial virus (RSV) is important in both protection and immunopathogenesis. In contrast to HLA class I, HLA class II-restricted RSV-specific T-cell epitopes have not been identified. Here, we describe the generation and characterization of two human RSV-specific CD4(+)-T-cell clones (TCCs) associated with type 0-like cytokine profiles. TCC 1 was specific for the matrix protein and restricted over HLA-DPB1*1601, while TCC 2 was specific for the attachment protein G and restricted over either HLA-DPB1*0401 or -0402. Interestingly, the latter epitope is conserved in both RSV type A and B viruses. Given the high allele frequencies of HLA-DPB1*0401 and -0402 worldwide, this epitope could be widely recognized and boosted by recurrent RSV infections. Indeed, peptide stimulation of peripheral blood mononuclear cells from healthy adults resulted in the detection of specific responses in 8 of 13 donors. Additional G-specific TCCs were generated from three of these cultures, which recognized the identical (n = 2) or almost identical (n = 1) HLA-DP4-restricted epitope as TCC 2. No significant differences were found between the capacities of cell lines obtained from infants with severe (n = 41) or mild (n = 46) RSV lower respiratory tract infections to function as antigen-presenting cells to the G-specific TCCs, suggesting that the severity of RSV disease is not linked to the allelic frequency of HLA-DP4. In conclusion, we have identified an RSV G-specific human T helper cell epitope restricted by the widely expressed HLA class II alleles DPB1*0401 and -0402. Its putative role in protection and/or immunopathogenesis remains to be determined

QCD Loop Corrections to Top Production and Decay at e^+ e^- Colliders

We present a computation of QCD next-to-leading order virtual corrections to the top production and decay process at linear colliders. The top quarks are allowed to be off-shell and the production and decay subprocesses are treated together, thus allowing for interference effects. The framework employed for our computation is the double pole approximation (DPA). We describe the implementation of this approximation for the top production and decay process and compare it with the implementation of DPA for the evaluation of QED corrections to the W pair production at LEP II. Similarities and differences between the two cases are pointed out. One result of interest is the incomplete cancelation of interference corrections. Other results include values for the total NLO top production cross section, and the impact the nonfactorizable (interference) corrections have on the top invariant mass distribution.Comment: 27 pages, 8 ps figures; reference added to introductio

Generalized Parton Distributions at x->1

Generalized parton distributions at large $x$ are studied in perturbative QCD approach. As $x\to 1$ and at finite $t$, there is no $t$ dependence for the GPDs which means that the active quark is at the center of the transverse space. We also obtain the power behavior: $H_q^\pi(x,\xi,t)\sim (1-x)^2/(1-\xi^2)$ for pion; $H_q(x,\xi,t)\sim (1-x)^3/(1-\xi^2)^2$ and $E_q(x,\xi,t)\sim (1-x)^5/(1-\xi^2)^3f(\xi)$ for nucleon, where $f(\xi)$ represents the additional dependence on $\xi$.Comment: 7 pages, 2 figure

Nuclear effects in the Drell-Yan process at very high energies

We study Drell-Yan (DY) dilepton production in proton(deuterium)-nucleus and in nucleus-nucleus collisions within the light-cone color dipole formalism. This approach is especially suitable for predicting nuclear effects in the DY cross section for heavy ion collisions, as it provides the impact parameter dependence of nuclear shadowing and transverse momentum broadening, quantities that are not available from the standard parton model. For p(D)+A collisions we calculate nuclear shadowing and investigate nuclear modification of the DY transverse momentum distribution at RHIC and LHC for kinematics corresponding to coherence length much longer than the nuclear size. Calculations are performed separately for transversely and longitudinally polarized DY photons, and predictions are presented for the dilepton angular distribution. Furthermore, we calculate nuclear broadening of the mean transverse momentum squared of DY dileptons as function of the nuclear mass number and energy. We also predict nuclear effects for the cross section of the DY process in heavy ion collisions. We found a substantial nuclear shadowing for valence quarks, stronger than for the sea.Comment: 46 pages, 18 figures, title changed and some discussion added, accepted for publication in PR

The First Magnetic Fields

We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark-hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars is discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early generation of stars or active galactic nuclei can be dispersed into the intergalactic medium.Comment: Accepted for publication in Space Science Reviews. Pdf can be also downloaded from http://canopus.cnu.ac.kr/ryu/cosmic-mag1.pd