Monozygotic twins with a severe form of Alagille syndrome and phenotypic discordance

Alagille syndrome is an autosomal dominant disorder affecting multiple organ systems, predominantly the liver, heart, skeleton, eye, face, and kidney. The phenotype in Alagille syndrome is highly variable both within and between families. We report monozygotic twins with Alagille syndrome concordant for a mutation in Jagged1 but discordant for clinical phenotype. The twins' monozygosity was confirmed by molecular testing. A de novo splice site mutation was identified in exon 6 (1329 + 2T --> G) in both children. Both twins display a severe form of Alagille syndrome; however, one twin has a severe pulmonary atresia with mild liver involvement, while the other has tetralogy of Fallot and severe hepatic involvement, which has required liver transplantation. Potential mechanisms for phenotypic variability among monozygotic twins are discussed. This is the first reported case of discordance in phenotype in monozygotic twins with Alagille syndrome. This case implies that genotypic variations alone do not explain the clinical variability seen in Alagille syndrome and supports the contributory role of nongenetic factors in phenotype determination.     

Molecular characterization of two soybean-infecting begomoviruses from India and evidence for recombination among legume-infecting begomoviruses from South [corrected] South-East Asia

The complete nucleotide sequences of two soybean-infecting begomoviruses have been determined from central and southern parts of India. Sequence analyses show that the isolate from central India is a strain of Mungbean yellow mosaic India virus (MYMIV) and the southern Indian isolate is a strain of Mungbean yellow mosaic virus (MYMV). Multiple DNA B components could be detected with the soybean strain of Mungbean yellow mosaic virus species. The nucleotide sequence similarity between the DNA A components of the two isolates is higher (82%) than that between the corresponding DNA B components (71%). Analyses of the common region of the genomic components of these two virus isolates indicate considerable divergence in the origin of replication (ori), which did not impair their infectivity as demonstrated for the central Indian isolate by agroinfection with partial tandem repeats (PTRs) of the genomic components. Detailed sequence and phylogenetic analyses reveal the distribution and possible recombination events among legume-infecting begomoviruses from South-East Asia.     

Pyocyanin from Pseudomonas aeruginosa inhibits prostacyclin release from endothelial cells.

Pseudomonas aeruginosa pneumonia causes a vasculitis of small pulmonary arteries. While the fully developed lesion demonstrates vessel wall necrosis, the early lesion is remarkable for preservation of viable endothelium despite vessel wall invasion by bacteria. Pyocyanin, an exoproduct of P. aeruginosa, markedly inhibited prostacyclin production by pulmonary artery endothelial cells without causing cell lysis. Pyocyanin might after vascular homeostasis in the absence of cytolysis.     

Protection against virulent Mycobacterium avium infection following DNA vaccination with the 35-kilodalton antigen is accompanied by induction of gamma interferon-secreting CD4(+) T cells

Mycobacterium avium is an opportunistic pathogen that primarily infects immunocompromised individuals, although the frequency of M. avium infection is also increasing in the immunocompetent population. The antigen repertoire of M. avium varies from that of Mycobacterium tuberculosis, with the immunodominant 35-kDa protein being present in M. avium and Mycobacterium leprae but not in members of the M. tuberculosis complex. Here we show that a DNA vector encoding this M. avium 35-kDa antigen (DNA-35) induces protective immunity against virulent M. avium infection, and this protective effect persists over 14 weeks of infection. In C57BL/6 mice, DNA vaccines expressing the 35-kDa protein as a cytoplasmic or secreted protein, both induced strong T-cell gamma interferon (IFN-gamma) and humoral immune responses. Furthermore, the antibody response was to conformational determinants, confirming that the vector-encoded protein had adopted the native conformation. DNA-35 immunization resulted in an increased activated/memory CD4(+) T-cell response, with an accumulation of CD4(+) CD44(hi) CD45RB(lo) T cells and an increase in antigen-specific IFN-gamma production. The protective effect of the DNA-35 vectors against M. avium infection was comparable to that of vaccination with Mycobacterium bovis BCG and significantly greater than that for previous treated infection with M. avium. These results illustrate the importance of the 35-kDa protein in the protective response to M. avium infection and indicate that DNA vaccination successfully promotes a sustained level of protection during chronic M. avium infection.     

Optimal leaf sequencing with elimination of tongue-and-groove underdosage

The individual leaves of a multileaf collimator (MLC) have a tongue-and-groove or stepped-edge design to minimize leakage radiation between adjacent leaves. This design element has a drawback in that it creates areas of underdosages in intensity-modulated photon beams unless a leaf trajectory is specifically designed such that for any two adjacent leaf pairs, the direct exposure under the tongue-and-groove is equal to the lower of the direct exposures of the leaf pairs. In this work, we present a systematic study of the optimization of a leaf sequencing algorithm for segmental multileaf collimator beam delivery that completely eliminates areas of underdosages due to tongue-and-groove or stepped-edge design of the MLC. Simultaneous elimination of tongue-and-groove effect and leaf interdigitation is also studied. This is an extension of our previous work (Kamath et al 2003a Phys. Med. Biol. 48 307) in which we described a leaf sequencing algorithm that is optimal for monitor unit (MU) efficiency under most common leaf movement constraints that include minimum leaf separation. Compared to our previously published algorithm (without constraints), the new algorithms increase the number of sub-fields by approximately 21% and 25%, respectively, but are optimal in MU efficiency for unidirectional schedules.     

Dendritic cells infected with Mycobacterium bovis bacillus Calmette Guerin activate CD8(+) T cells with specificity for a novel mycobacterial epitope

Although CD4(+) T cells are essential for protective immunity against Mycobacterium tuberculosis infection, recent reports indicate that CD8(+) T cells may also play a critical role in the control of this infection. However, the epitope specificity and the mechanisms of activation of mycobacteria-reactive CD8(+) T cells are poorly characterized. In order to study the CD8(+) T cell responses to the model mycobacterial antigen, MPT64, we used recombinant vaccinia virus expressing MPT64 (VVWR-64) and a panel of MPT64-derived peptides to establish that the peptide MPT64(190-198) contains an H-2D(b)-restricted CD8(+) T cell epitope. A cytotoxic T lymphocyte response to this peptide could be demonstrated in M. bovis bacillus Calmette Guerin (BCG)-infected mice following repeated in vitro stimulation. When bone marrow-derived dendritic cells (DC) were infected with BCG, the expression of MHC class I molecules by DC was up-regulated in parallel with MHC class II and B7-2, whereas CD1d expression level was not modified. Moreover, BCG-infected DC activated MPT64(190-198)-specific CD8(+) T cells to secrete IFN-gamma, although with a lower efficacy than VVWR-64-infected DC. The production of IFN-gamma by MPT64(190-198)-specific CD8(+) T cells was inhibited by antibodies to MHC class I, but not to CD1d. These data suggest that mycobacteria-specific CD8(+) T cells are primed during infection. Therefore, anti-mycobacterial vaccine strategies targeting the activation of specific CD8(+) T cells by DC may have improved protective efficacy.     

Optimal number of pinholes in multi-pinhole SPECT for mouse brain imaging--a simulation study

This study simulates a multi-pinhole single-photon emission computed tomography (SPECT) system using the Monte Carlo method, and investigates different multi-pinhole designs for quantitative mouse brain imaging. Prior approaches investigating multi-pinhole SPECT were not often optimal, as the number and geometrical arrangement of pinholes were usually chosen empirically. The present study seeks to optimize the number of pinholes for a given pinhole arrangement, and also for the specific application of quantitative neuroreceptor binding in the mouse brain. An analytical Monte Carlo simulation based method was used to generate the projection data for various count levels. A three-dimensional ordered-subsets expectation-maximization algorithm was developed and used to reconstruct the images, incorporating a realistic pinhole model for resolution recovery and noise reduction. Although artefacts arising from overlapping projections could be a major problem in multi-pinhole reconstruction, the cold-rod phantom study showed minimal loss of spatial resolution in multi-pinhole systems, compared to a single-pinhole system with the same pinhole diameter. A quantitative study of neuroreceptor binding sites using a mouse brain phantom and low activity (37 MBq) showed that the multi-pinhole system outperformed the single-pinhole system by maintaining the mean and lowering the variance in the measured uptake ratio. Multi-pinhole collimation can be used to reduce the injected dose and thereby reduce the radiation exposure to the animal. Results also suggest that the nine-pinhole configuration shown in this paper is a good choice for mouse brain imaging.     

Role of antibodies in immunity to Bordetella infections

The persistence of Bordetella pertussis and B. parapertussis within vaccinated populations and the reemergence of associated disease highlight the need to better understand protective immunity. The present study examined host immunity to bordetellae and addressed potential concerns about the mouse model by using a comparative approach including the closely related mouse pathogen B. bronchiseptica. As previously observed with B. pertussis, all three organisms persisted throughout the respiratory tracts of B-cell-deficient mice, indicating that B cells are required for bacterial clearance. However, adoptively transferred antibodies rapidly cleared B. bronchiseptica but not human pathogens. These results obtained with the mouse model are consistent with human clinical observations, including the lack of correlation between antibody titers and protection, as well as the limited efficacy of intravenous immunoglobulin treatments against human disease. Together, this evidence suggests that the mouse model accurately reflects substantial differences between immunities to these organisms. Although both B. pertussis and B. parapertussis are more closely related to B. bronchiseptica than they are to each other, they share the ability to resist rapid clearance from the lower respiratory tract by adoptively transferred antibodies, an adaptation that correlates with their emergence as human pathogens that circulate within vaccinated populations.