Immunodiagnostics of Lyme neuroborreliosis

Lyme borreliosis (LB) is caused by spirochetes that are part of the Borrelia burgdorferi sensu lato (s.l.) complex group. The most prevalent manifestation of LB is characterized by a red, migrating skin lesion, also known as erythema migrans. If left untreated, then B. burgdorferi s.l. can disseminate through the body and infect other body parts such as the joints, the nervous system (Lyme neuroborreliosis (LNB)), the heart and/or other parts of the skin, although for the majority of cases LB resolves without treatment. The diagnosis of LB is based on the presence of clinical symptoms and, for most Lyme manifestations, should be supported by laboratory tests. The most widely used laboratory test is based on the detection of Borrelia-specific antibodies. The utility of antibody detection to support the diagnosis of LB, however, is hampered by a low sensitivity of antibody detection early in the infection, and the persistence of antibodies after a cleared infection. The research conducted in this thesis focused on the humoral and the cellular immune response to investigate whether LB diagnostics can be improved. As clear case-definitions are available for active LNB, well-defined patients with LNB were used as a proxy for patients with active LB.The research in this thesis has provided more insight into the added value and the pitfalls of laboratory tests for the diagnosis of LNB. It shows that the interferon-gamma enzyme-linked immunospot assay cannot be used for the diagnosis of LNB. Furthermore, it demonstrates the added value of elevated levels of the B-cell chemokine (C-X-C motif) ligand 13 in the cerebrospinal fluid for the diagnosis of LNB and that more research is necessary to investigate if an international reference standard can be established. Additionally, the research in this thesis underlines that a thorough validation of serological tests is important before its use in diagnostics and it illustrates that antibiotic treatment of an infection with B. burgdorferi s.l. is associated with discordant serological test results. The most important finding of the research conducted in this thesis; however, is the proposal of a diagnostic algorithm for LNB diagnostics. Such an algorithm should include tests that consider both the humoral as well as the cellular immune response as both may contribute to the diagnosis of LNB. By covering different aspects of the immune system, a concrete and feasible tool is provided that can better discriminate between an active and a previous infection with B. burgdorferi s.l., which and this will improve LNB diagnostics.Regionale Maatschap Medische Microbiologie en Immunologie Utrecht; Maatschap Neurologie Diakonessenhuis; Stichting Medicina et Scientia; Diakonessenhuis Onderzoeksfonds;LUMC / Geneeskund

The HI Environment of Nearby Lyman-alpha Absorbers

We present the results of a VLA and WSRT search for HI emission from the vicinity of seven nearby clouds, which were observed in Lya absorption with HST toward Mrk335, Mrk501 and PKS2155-304. We searched a volume of 40' x 40' x 1000 km/s. The HI mass sensitivity (5 sigma) varies from 5x10^6 to 5x10^8 Msun. We detected HI emission in the vicinity of four out of seven absorbers. The closest galaxy is a small dwarf galaxy at a projected distance of 68/h kpc from the sight line toward Mrk335. It has the same velocity (V=1970 km/s) as one of the absorbers, and has an HI mass of only 4x10^7 Msun. We found a more luminous galaxy at the velocity (V=5100 km/s) of one of the absorbers toward PKS2155-304, 230/h kpc from the sight line. Two other, stronger absorbers toward PKS2155-304 at V=17,000 km/s are associated with a loose group of three bright spiral galaxies, at projected distances of 300 to 600/h kpc. These results support the conclusion that most nearby Lya forest clouds trace the large-scale structures outlined by optically luminous galaxies. We do not find any evidence for a physical association between an absorber and its closest galaxy.Comment: 4 Tables, 11 Figures, to be published in Astron J. (Oct 1996) Vol 11

A circumnuclear disk of atomic hydrogen in Centaurus A

We present new observations, performed with the Australia Telescope Compact Array, of the HI absorption in the central regions of Centaurus A. For the first time, absorption is detected against the radio core at velocities blueshifted with respect to the systemic velocity. Moreover, the data show that the nuclear redshifted absorption component is broader than reported before. With these new results, the kinematics of the HI in the inner regions of Cen A appears very similar to that observed in emission for the molecular circumnuclear disk. This suggests that the central HI absorption is not, as was previously claimed, evidence of gas infall into the AGN, but instead is due to a cold, circumnuclear disk.Comment: Accepted for publication in A&A Letter, 4 pages, 2 figure

N(HI) and jet power/emission in AGNs

Neutral hydrogen (HI) 21 cm absorption has been detected against more and more powerful radio jets. In this work, based on the Guppta et al. 2006a sample, we present our preliminary study of the correlations between the HI column density N(HI) and the jet power, N(HI) versus the low frequency luminosity at 408MHz, and N(HI) versus the radio luminosity at 1400MHz.Comment: 3 pages, 1 figures, Multiwavelength Variability of Blazars Guangzhou, China, Sept. 22-24, 2010; will be published by JA

Mycobacterium tuberculosis Beijing genotype emerging in Vietnam.

To assess whether the Mycobacterium tuberculosis Beijing genotype is emerging in Vietnam, we analyzed 563 isolates from new cases by spoligotyping and examined the association between the genotype and age, resistance, and BCG vaccination status. Three hundred one (54%) patients were infected with Beijing genotype strains. The genotype was associated with younger age (and hence with active transmission) and with isoniazid and streptomycin resistance, but not with BCG vaccination

A large HI cloud near the centre of the Virgo cluster

We report the discovery of a large HI cloud in the central regions of the Virgo cluster. It is 110 x 25 kpc in size and contains 3.4 x 10^8 Msol of HI. The morphology and kinematics of this cloud strongly suggest that it consists of HI removed from the galaxy NGC 4388 by ram-pressure stripping. It is more likely the result of an interaction of the ISM of NGC 4388 with the hot halo of the M86 group and not with the ICM centred on M87. The large extent of the plume suggests that gas stripped from cluster galaxies can remain neutral for at least 10^8 yr. Locally, the column density is well above 10^20 cm^-2, suggesting that the intra-cluster HII regions known to exist in Virgo may have formed from gas stripped from cluster galaxies. The existence of the HI plume suggests that stripping of infalling spirals contributes to the enrichment of the ICM. The HI object in the Virgo cluster recently reported by Minchin et al. may have a similar origin and may therefore not be a ``dark galaxy''.Comment: Accepted for publication in A&A. 5 pages, 2 figures. Version with high-resolution figures at http://www.astron.nl/~oosterlo/n438