Urticaria is one of the most common dermatologic problems seen by primary care physicians and often a source of frustration for patient and physician alike. Pinpointing the cause may be challenging—or impossible—because of the many and varied triggers. Drs Krishnaswamy and Youngberg shed light on this common condition, describing the diagnostic considerations in evaluation of acute and chronic cases and discussing the variety of pharmacologic options available.

Mast cells are multifunctional, tissue-dwelling cells capable of secreting a wide variety of mediators. They develop from bone marrow-derived progenitor cells, primed with stem cell factor (SCF), which mediates its actions by interacting with the SCF receptor or c-kit on the cell surface. Mast cells continue their maturation and differentiation in peripheral tissue, developing into two well described subsets of cells, MCT and MCTC cells, varying in content of tryptase and chymase as well as in immunobiology. Mast cells are activated by numerous stimuli, including antigen (acting via the high affinity IgE receptor, Fc?RI), superoxides, complement proteins, neuropeptides and lipoproteins resulting in activation and degranulation. Following activation, these cells express mediators such as histamine, leukotrienes and prostanoids, as well as proteases, and many cytokines and chemokines, pivotal to the genesis of an inflammatory response. Recent data suggests that mast cells may play an active role in such diverse diseases as atherosclerosis, malignancy, asthma, pulmonary fibrosis and arthritis. Mast cells directly interact with bacteria and appear to play a vital role in host defense against pathogens. Drugs, such as glucocorticoids, cyclosporine and cromolyn have been demonstrated to have inhibitory effects on mast cell degranulation or mediator release.

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Bone morphogenetic protein 4 (BMP4) is a potent growth factor that is involved in many important biological processes. Regulation of the level of secreted mature BMP4 determines the biological effects of BMP4 on cells in the local microenvironment. Previous studies suggested that Gremlin, a member of DAN family proteins, antagonizes BMP4 activity by sequestering extracellular BMP4. Herein, we report a novel intracellular regulatory mechanism by which Gremlin interacts with BMP4 precursor, prevents secretion of mature BMP4, and therefore inhibits BMP4 activity more efficiently. Furthermore, we also defined a 30-amino acid peptide sequence within the Gremlin DAN domain that is essential for BMP4 interaction. This novel Gremlin-mediated BMP4 posttranslational regulatory mechanism implies that the level of BMP4 mRNA expression does not truly reflect BMP4 activity when Gremlin and BMP4 are coexpressed within the same cell. Similar regulatory mechanisms may be utilized by other DAN family proteins.

It is widely held that for an HIV-1 vaccine to provide sterilizing immunity, it would need to elicit broadly neutralizing antibodies (bnAbs). However, factors underlying the development of these antibodies are not clear. There is evidence to suggest that in some individuals who develop bnAbs, the development of breadth is influenced by the co-evolution of the transmitted/founder (t/f) virus and earlier strain-specific neutralizing antibody (ssnAb) responses. Here we characterized the viral evolution, ssnAb and bnAbs responses in CAP292, an HIV-1 infected woman who developed bnAb responses from one year post infection. We used single genome amplification (SGA) to characterize viral evolution at four time points: at acute infection; after the development of strain-specific neutralizing responses; at the first detection of the broadly neutralizing antibody response; and lastly, at the peak of the broad response. We identified the t/f virus, and generated chimeric viruses from this to determine the targets of the ssnAb responses. A panel of site-directed mutant viruses were used to map the specificity of the bnAb responses. Our data indicated that infection was most likely founded by a single virus and that the first wave of ssnAbs emerged at 14 weeks post infection (w.p.i), targeting the V1V2 loop of Envelope (Env). A second wave of ssnAbs, possibly targeting the C3V4 region, emerged by 30 w.p.i. Two distinct viral clusters were detected by the time the bnAb response peaked, suggesting the presence of distinct escape pathways. Mapping of the bnAb specificities indicated that CAP292 produced PGT128-like bnAb responses targeted toward the 332 glycan.

Introduction Although adolescents have the highest force of Mycobacterium tuberculosis infection1 and rapidly increasing burden of tuberculosis (TB) disease through 10–19 years of age,2 there are few studies on adolescent Mycobacterium tuberculosis infection, transmission, and TB disease in the WHO African region. Adolescents in the high TB burden countries of Africa are therefore an important, but neglected risk group for global TB control efforts. Adolescents spend a considerable amount of their time in school classrooms, but there is paucity of data on classroom risk of Mycobacterium tuberculosis transmission. To the best of our knowledge, no published study has conducted measurement of air quality and air sampling for Mycobacterium tuberculosis DNA in school classrooms, a novel approach that may support targeted TB disease case–finding strategies which may be more efficient than symptom–based TB screening in the congregate school setting. The overall aims of this PhD project were: 1) To conduct a systematic review of adolescent latent TB infection (LTBI) and TB disease prevalence, and to examine the relationship between adolescent Mycobacterium tuberculosis infection and TB disease rates, in high TB burden African countries. 2) To describe temporal changes in prevalence of LTBI among adolescents living in a single TB endemic South African community, across two time periods spanning the decade 2005–2015. 3) To describe temporal changes in adolescent TB disease notification rates in the same community for the decade 2005–2015. 4) To determine classroom ventilation risk for Mycobacterium tuberculosis transmission in tandem with a pilot study of air sampling for Mycobacterium tuberculosis DNA; and to investigate the operational feasibility and yield of a pragmatic, symptom–based approach to TB disease surveillance in high schools. Methods To achieve Aim 1, we performed a bibliographic database search for studies conducted and published between 1990 and 2018 on prevalence of adolescent (10–19 years) LTBI and TB disease in high TB burden African countries. We calculated the ratio between the number of Mycobacterium tuberculosis infections based on Annual Risk of TB Infection (ARTI) estimates and the number of microbiologically–confirmed TB disease cases per year, and compared the observed ratio to the expected ratio of 8–12 published by Styblo et al.3 To achieve Aim 2, we collected adolescent LTBI (defined by positive QuantiFERON® –TB Gold In–Tube test) prevalence data from eight South African high schools, spanning the decade 2005–2015, from databases of an adolescent cohort study (2005–2007) and an adolescent vaccine trial (2014–2015). We used the two–sample test of equality of proportions to compare changes in LTBI prevalence over the two periods. To achieve Aim 3, we collected adolescent TB disease notification data from the same community (using an electronic tuberculosis disease register) for the decade 2005–2015 and we used the Mann–Kendall test to explore temporal changes in notification rates. To achieve Aim 4, we conducted a cross sectional study of 72 classrooms occupied by 1,836 high school learners, in addition to 7 comparator clinic spaces selected for high a priori risk of Mycobacterium tuberculosis transmission, and performed ventilation (carbon dioxide concentration) measurement to define spaces with high ventilation risk (>1,000 ppm) and ddPCR air sampling for Mycobacterium tuberculosis DNA, with active TB symptom screening among learners. Results 1) There is paucity of data on adolescent LTBI and TB disease prevalence in high TB burden African countries (1990–2018). Based on the limited available data, both LTBI (16%–55%)4–8 and TB disease prevalence rates are high (180–679 cases per 100,000),6–10 but corresponding infection–to–disease ratios are inconsistently low compared to that expected from Styblo's Rule.3 2) Overall adolescent LTBI prevalence remained high and relatively unchanged (44–49%) between 2005– 2015. 11 However, although average LTBI prevalence was unchanged in lower socio–economic quintile schools, prevalence increased in highest socio–economic quintile schools (from 20% to 38%).11 3) Adolescent TB disease notification rates fell 45% (662 to 361 per 100,000) in the same community over the same period. Despite this decrease, recent TB disease prevalence remains high and is three– fold higher in older (15–19 years) than younger (10–14 years) adolescents (566 vs. 151 per 100,000 in 2015). 4) More than one–third of 72 high school classrooms were inadequately ventilated and one–fifth of classrooms had evidence of airborne Mycobacterium tuberculosis DNA detected by ddPCR air sampling. The average risk of inhaling 1 Mycobacterium tuberculosis DNA copy was similar between clinics and classrooms. Across all classrooms the average risk of a classroom occupant inhaling 1 Mycobacterium tuberculosis DNA copy over 1 lesson (35 minutes) was 0.71%; and the estimated risk over 1 academic year was 100%. However, yield from symptom–based TB screening was low, consistent with the presence of undiagnosed subclinical TB cases and risk of ongoing transmission in the school setting. Conclusion Despite the encouraging decline in adolescent TB disease notification rates observed between 2005–2015 in the study area, adolescent LTBI prevalence remains high, consistent with ongoing medium–term transmission. The relatively high proportion of inadequately ventilated classrooms would place learners at high risk of Mycobacterium tuberculosis transmission if exposed to an infectious occupant. This risk appears material, given the proportion of classrooms with a positive ddPCR air filtrate sample and the estimated cumulative risk of inhaling of at least one copy of Mycobacterium tuberculosis DNA. The presence of previously undiagnosed TB cases among learners is inferred from our classroom ddPCR air sampling data, which further suggest that pragmatic school–based TB symptom screening is an inefficient surveillance strategy that likely missed learners with subclinical TB. Improved ventilation in school classrooms is a low–cost intervention that may reduce the risk of TB transmission in schools. New and more efficient targeted TB disease case–finding strategies are needed for congregate settings, including schools, in high TB burden countries. Based on our preliminary data, classroom ddPCR air sampling for Mycobacterium tuberculosis DNA appears feasible for this purpose, but requires further research to optimise diagnostic accuracy and demonstrate cost–effectiveness and public health value in high TB burden countries.

Tuberculosis predominantly manifests in the form of a pulmonary infection, but may spread out into other parts of the body and is then referred to as extrapulmonary tuberculosis (EPTB). One form of EPTB is an infection of the central nervous system (brain & spinal cord), CNS-TB. Although CNS-TB is relatively rare, accounting for about 5% of EPTB, it is characterised by high morbidity and mortality, particularly for children and immunosuppressed individuals. To examine the effects of a Mycobacterium tuberculosis infection of neural tissue, researchers have hitherto relied on two animal models namely, in vivo intracranial infections or in vitro culturing with dissociated neural cells. Both models have yielded crucial insights concerning CNS-TB but each have limitations e.g. lack of access to the brain during infection in vivo and absence of the 3D organizational tissue structure in vitro. This study investigated the effect of the vaccine strain for tuberculosis, Bacille Calmette-Guerin (BCG) on neural tissue using the model of organotypic hippocampal slice cultures; an in vitro model that overcomes the previously mentioned obstacles. The study sought to expound on immunological and electrophysiological responses to the infection. A viable and moderate BCG infection was established in the hippocampal slice cultures, confirmed by colony forming units enumeration and immunohistochemistry. However, immunological analysis using ELISA found that BCG infection did not change the production levels of cytokines and elicit a distinguishable immune response. To examine the neuronal function during BCG infection, whole-cell patch clamp technique was applied to the hippocampal slice cultures. The neuronal intrinsic properties were not significantly different between infected and non-infected slices. However, tuberculin PPD (M. tuberculosis extract) moderately and transiently had a depolarizing effect when 'puffed' directly onto neurons. In conclusion, organotypic slice cultures are suitable for the investigation of cellular interactions and neural functions in CNS-TB, and the neuronal impact of PPD warrants further investigation.

The aim of the current study is the characterisation (primarily pathological, but with clinical correlation) of the germ cell tumours seen in the Pathology Department of the Red Cross Childrens Hospital since its inception in 1956 (through to the year 1995, date of commencement of the study). Study population: Infants and children from birth to 13 years of age (of all population groups, but predominantly those from the disadvantaged black and mixed race communities of the Greater Cape Town metropolitan area).

Tuberculosis of the central nervous system (CNS TB) is the severest form of tuberculosis. It is classified as extra-pulmonary tuberculosis due to dissemination of Mycobacterium tuberculosis (Mtb) bacilli from the lung to the brain. It affects mostly children and immune suppressed individuals and high incidents of death occur as a result of missed diagnosis and delayed treatment. Therefore, the is a need for improved therapeutic strategy and a better understanding of the CNS immunity; investigate cells targeted for infection, their respective response to infection and interaction with different cell types to the overall protection of the CNS - as accumulating evidence indicates a dynamic neuronal lymphocyte interplay that defines outcomes of diseases. A novel observation was previously made, that neurons are infected by Mtb during in vitro and in vivo infection. The aim of this study was to further characterize neural responses induced by mycobacteria using hippocampal primary neuron cultures, infected with H37RV and BCG. Secondly, this study investigated the importance of interaction between neurons and immune cells in immunity against mycobacterial challenge using an optimised neuron T cell co-culture model. Investigation included identifying the production levels of neuronal cell surface markers and cytokines induced by Mtb. In flowcytometry and ELISA analyses, infection exhibited a robust inflammatory response with increased neuronal production of cytokines such as IL1β, IL6, TNF and regulatory cytokine IL10 in vitro and in vivo. Neuronal MHC class I expression was upregulated by infection, suggesting possible antigen dependent interactions between neuron and CD8+ T cells. In co-cultures, neurons induced expression of Tbet, RorγT and Gata3 T cell transcription factors through direct contact with T cells. These data highlighted the likelihood of neurons activating T cells upon mycobacterial stimulations. It may potentially be utilised to broaden the understanding of CNS immunity under pathological conditions and possibly lead to identification of novel immunomodulatory targets that could be exploited for new rapid sensitive diagnostics and early opportune intervention against CNS TB – reducing morbidity and mortality associated with the disease.

Background Over the past few years, Genome Wide Association Studies (GWAS) have identified thousands of genetic variants that are associated with a wide range of complex traits, and have provided valuable insights as far as their genetic architectures are concerned. In malaria studies too, GWAS has been successful and a number of genetic variants have been identified. Despite the success, the complete aetiology of malaria, and many complex traits in general, remains poorly understood. A key concern is that the missing heritability remains too large, with some of the variants identified in some populations failing to replicate using independent study populations. Indeed comparable sources have revealed that the statistical power of association studies can be improved either via genotypes imputation approaches or by treating the whole genome of an individual as a risk predictor using Polygenic Risk Scores (PRS). However, imputation remains at modest in Africa populations with few (or no) studies (study) have evaluated the potential of imputation tools in African populations. On the other hand, although the utility of PRS has been shown in other studies, it has neither been assessed in African population nor applied in an infectious disease, like malaria. Methodology We evaluated the performance of five popular genotypes imputation methods (IMPUTE4, minimac 4, IMPUTE2, minimac3 and BEAGLE4) using case control datasets that mimics African populations, European populations and the admixed populations simulated with FractalSIM. We assessed imputation performance based on internal imputation quality metrics and the genotypes concordance. We applied the best imputation tool based on the assessment results to impute raw genotypes data of severe malaria case control studies from MalariaGEN of three African populations: Kenya, The Gambia and Malawi. Similarly, we obtained summary statistics of the same datasets, and imputed the summary statistics with ImpG. We performed an association on the imputed raw genotypes, and compared the association results with that of ImpG based imputation. Additionally, we performed meta-analysis with METASOFT, and compared the meta-analysis result of ImpG based imputation and that from imputed raw genotypes associations. Finally, we assessed five PRS methods (PRSice, LDpred(p+t), PRSoS, PLINK and PRScS) in predicting genetic risk in African population, and applied the best PRS method to predict the genetic risk of severe malaria. Results IMPUTE2 recorded the best performance based on imputation accuracy and concordance for the African (accuracy=80.21% and concordance=99.2%) and the admixed samples (accuracy=69.46% and concordance=90.92%) for variants with MAF>0.05. Other tools recorded similar accuracy and concordance although BEAGLE 4 recorded the lowest concordance and accuracy across all the African and admixed datasets. For the real genotypes data, no SNP attained the genome wide significant threshold of 5.0 × 10−8 for Malawi and the Gambia datasets. However, for the Kenyan dataset, 9 SNPs on chromosome 11 were significantly associated with severe malaria. 3 of these SNPS were located on the HBG2 genes and the remaining 6 had not been reviewed. No SNP attained the genome wide threshold for the ImpG imputed summary statistics for all the populations. For IMPUTE2 based meta-analysis, only one SNP rs12295158 located on the HBB region was significant across all the meta-analysis model (with P-value of 2.88 × 10−12 for fixed (FE), 2.88 × 10−12 random (RE) and 9.64 × 10−12 binary effect (BE) respectively). On the other hand ImpG based meta-analysis, two SNPs were signicant across all the meta-analysis model (rs183731078 located on RFX3 with P-values of 8.40 × 10−9 , 8.40 × 10−9 , 4.47 × 10−8 for FE, RE and BE respectively, and rs8096513 located on DLGAP1 1.43 × 10−9 , 1.43 × 10−9 , 1.01 × 10−8 with P-value for FE, RE and BE respectively). Pathway enrichment and analysis of these genes revealed that both of these genes are associated with malaria. Finally, for the PRS, PRSoS recorded the best performance based on Nargalkerke's R 2 (0.01736) and area under curve (AUC) (0.511). Other PRS methods recorded slightly similar results with PLINK recording the least. The odds of having severe malaria was estimated as 2.869, and a unit change of PRS scores was associated with -5.143 change in odds of having severe malaria with P-value of 0.0193 at α = 0.05. However, the scores could only explain 1.28% of the phenotypic variance. Conclusion Our results provide foundation for future studies in genetics, especially in African population, where the best performing imputation tool remains a mystery. Moreover, our results have demonstrated the potential of application of PRS in infectious diseases.