Abstract -1 The immune response occurred in the mice infected with Angiostrongylus cantonensis was mainly humoral immune response. This study was designed to compare the systemic and localized humoral immune responses occurred after primary and secondary infections in C57BL/6J mice. Eight weeks after the primary infection with 20 third-stage larvae, each mouse received a second inoculation of the same dosage. Specific serum IgM, IgG and IgE were found in the second week after primary infection. However, the titers of IgG1 and IgG2b increased at the fourth week after primary infection. Antibodies of these mentioned increased continuously as the progress of infection. On the other hand, the IgM and IgG1 titers increased in brain tissue infusion since the forth week after primary infection, while the titer of IgG start to elevate at the sixth week. Nevertheless, the increase of IgG2B was only noticed at the sixth week and no significant change was observed for IgG2a and IgE. After the secondary infection, serum IgM titers increased while the titer of IgG1 in the brain tissue infusion decreased. Results of Western blot showed that IgG1and IgE in the brain tissue infusion lost the ability to recognize a 42 kDa molecule of the somatic and excreting-secreting antigens of fifth-stage larvae. These variations could be used in the diagnosis of the early stage of mice that re-infected with Angiostrongylus cantonensis. Abstract -2 The radiographic lateral views of the skulls of the mice infected with Angiostrongylus cantonensis were taken. Thus, the parietofrontal index ( PI ) was obtained by measuring and calculating the distances among specific positions on their skulls. Compared with the controls, a significant elevation over the top of the crania of the cases was observed sixty days post-infection. In addition, the phenomenon emerged apparently during the second to the fourth week post-infection. These findings are able to be applied as the external diagnostic references for the infection course of mice infected with Angiostrongylus cantonensis.

Incidence of dengue fever (DF) has been estimated a 30 fold increase in the past 50 years. Clinical manifestations of DF range from a simple febrile illness with physical soreness to life-threatening dengue hemorrhagic fever (DHF). The need for a better classification of the severity in DEN infections has been proposed to clarify the immunopathogenesis for the prevention and management of serious DEN infections. We attempted to investigate whether different mechanisms involved in the varied manifestations of bleeding tendency and vascular leakage in DF. In a hospital-based study, we first compared clinical features as well as laboratory data including virus load, T helper (Th1/Th2) cytokines, and vascular leakage-related mediators between patients with DHF and DF. Moreover, we defined another class of patients associated with bleeding tendency but not fulfilled with DHF criteria, called DF w/B, for a further comparison. The virus load in blood was not significantly different among DF, DHF and DF w/B. DF patients had a higher Th1 cytokine, IFNr, expression (70.0 ¡Ó 10.7 vs. 33.1 ¡Ó 8.0 vs. 33.0 ¡Ó 7.1 pg/ml; DF vs. DF w/B, p = 0.009; DF vs. DHF, p = 0.002), and both DHF and DF w/B patients had a significantly higher IL-10 levels (14.3 ¡Ó 4.1 vs. 26.2 ¡Ó 3.3 vs. 26.0 ¡Ó 3.5 pg/ml; DF vs. DF w/B, p = 0.023; DF vs. DHF, p = 0.016) than DF patients. Both DHF and DF w/B patients also had a higher rate of secondary dengue infection (DF w/B vs. DHF vs. DF: 50.0%, 74.4% and 14.3%¡A p < 0.001). By contrast, DHF but not DF w/B patients had significantly higher vascular leakage-related mediators: sVCAM-1, PGE2 and TNF£\ levels than DF patients. Patients with DF w/B had a higher platelet counts (DF w/B vs. DHF: 66.0 ¡Ó 8.3 vs. 20.7 ¡Ó 2.1 x109/L, p < 0.001) but lower ALT levels than those with DHF (DF w/B vs. DHF: 56.3 ¡Ó 7.7 and 144.7 ¡Ó 20.5 IU/L). This study provides new insight to different immune mechanisms involved in patients with DF, DF w/B, and DHF. DF involves augmented Th1 reaction, and DF w/B involves altered Th2 reaction, but DHF involves both altered Th2 reaction and augmented vascular insult. Clarification of the immune mechanisms among DF, DFw/B and DHF will facilitate certain specific treatment and prevention of DF patients from varied bleeding tendency and vascular leakage manifestations.

La voie de signalisation des récepteurs à domaine de mort (RDM) intervient dans l'hématopoïèse. En effet, l'invalidation de FADD, la molécule adaptatrice des RDM, dans le compartiment lymphocytaire murin résulte en une absence totale de lymphocytes B en périphérie. Nos travaux ont révélé que l'invalidation de la fonction FADD inhibe profondément la production de cellules hématopoïétiques humaines à la fois B et non-B. Ces données suggèrent une implication de FADD dans l'expansion des CSH et des progéniteurs hématopoïétiques humains. Outre les RDM, les récepteurs Toll (TLR), dévolus à la reconnaissance des pathogènes, sont également capables de recruter FADD. Ceci nous a conduit à nous intéresser au rôle des TLR dans l'hématopoïèse humaine. Nous avons montré que les CSH et les progéniteurs hématopoïétiques humains expriment des TLR fonctionnels (TLR1, 2, 3 et 6 notamment). Nos résultats démontrent que la stimulation des TLR sur les CSH et les progéniteurs hématopoïétiques humains est susceptible de remodeler le développement hématopoïétique en favorisant l'engagement myéloïde au détriment du développement lymphocytaire B. Ce processus pourrait contribuer au renforcement du bras de l'immunité innée au cours des infections microbiennes

Mixed feeding confers excess risk of mother-to-child transmission (MTCT) of Human Immunodeficiency Virus (HIV) compared with exclusive breastfeeding (EBF) and exclusive formula feeding (EFF). We undertook a quantitative and qualitative cross-sectional survey to identify the social determinants of mixed feeding among a subset of HIV-infected women enrolled in a MTCT prevention program in Jos, Nigeria. Of the 91 participants, 68(75%) exclusively formula fed, 7(8%) exclusively breastfed, and 16(18%) practiced mixed feeding. Of the mixed feeding women, 7 primarily formula fed and 9 primarily breastfed. Women who primarily formula fed described family pressure as the reason for mixed feeding, whereas women who primarily breastfed indicated insufficient breast milk. In a multivariate analysis, lack of partner support of the feeding decision predicted mixed feeding behavior (OR: 4.2; 95% CI: 1.2-14.9; p=0.03). Disclosure of HIV status was significantly correlated (p<0.001) with partner support. HIV prevention interventions aimed at reducing mixed feeding should encourage supportive partner relationships that facilitate disclosure of HIV status. Attention should also be made to the differing pressures faced by women attempting to exclusively breastfeed and exclusively formula feed.

Thesis (M.D.S.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves.

The number of female veterans is increasing daily. Previous research conducted on veterans has focused primarily on males or with small samples of females. Depression and suicidality are becoming increasingly evident in returning veterans. Toxoplasma gondii is an intracellular parasite that is common in the Middle East and has been reported to cause changes in personality and behavior. The purpose of the current study was to examine relationships between T. gondii antibody titer and socioeconomic variables, dysphoric moods, and risk-taking behaviors in a sample of 70 female veterans. Blood samples were collected and analyzed for T. gondii antibody titer and participants completed a battery of questionnaires, including the Center for Epidemiologic Studies Depression (CES-D) scale, Profile of Mood States (POMS), PTSD Checklist- Military version (PCL-M), Alcohol Use Disorder Identification Test (AUDIT), and a sexual harassment and assault questionnaire. Results of chi-squares showed a relationship between T. gondii titer, ethnicity, marital status, and level of education. Pearson's correlations and t-tests showed relationships between T. gondii titer and POMS depression, confusion, and anger subscales, and total mood disturbance scores.

Interpersonal transport of expiratory droplets and droplet nuclei constitutes a prerequisite for the transmission of pathogens as well as the transmission of respiratory diseases. This study modeled the physical process of interpersonal transport of droplets and droplet nuclei in a ventilated room. The impacts of a number of parameters in three length scales and three corresponding physical processes were analyzed, including dispersion and evaporation of droplets/droplet nuclei at 1 to 100 μm, human exhalation flows and body plumes at 0.1 to 1 m, and the indoor environment at 1 to 10 m. The strong hygroscopicity of the solutes in the droplet is capable of keeping the droplet with an equilibrium size in humid air, larger than that of a dried particle. Mathematical models were developed to predict the droplet nucleus size in both dry air and humid air, by simplifying the composition of one expiratory droplet to NaCl solution and suspended spherical particles. For a droplet with an initial diameter of 100 μm, initial NaCl concentration of 0.9%, and initial solids ratio of 1.8%, the droplet nucleus size was estimated to be 42 μm in an ambient relative humidity of 90% (25°C), which is 30% larger than it was in a relative humidity of 30% (25°C). A numerical model was also developed to predict droplet evaporation and dispersion in a constant turbulent buoyant jet. Droplets with initial sizes larger than 80 μm were predicted to deposit on the floor at a distance of ~1.25 m (~1.7 m for 60 μm) away from the mouth, while droplets with initial sizes less than 40 μm travelled to the end of the jet. A series of experiments was conducted to assess the characteristics of human exhalation airflows and thermal plume, using a full-scale test room and a breathing thermal manikin. The impacts of the ventilation system were illustrated by comparing the velocity distribution of the exhalation airflows and airflows induced by thermal plume. Further experiments employing two breathing thermal manikins were carried out to evaluate the interpersonal transport of the expiratory contaminants that were simulated by tracer gas. When the two manikins with the same heights were standing face to face at a mutual distance of 0.8 m, the exhalation airflows from the mouth of the source manikin could directly travel into the breathing region of the susceptible manikin, resulting in a high exposure. The high exposure decreased sharply with an increase in the mutual distance from 0.5 m to 1.0 m. Between 1.0 m to 3.0 m, the exposure by the susceptible manikin remained at a low and constant level. Numerical simulations considering droplet evaporation and droplet nucleus sizes were carried out; and the impacts of the parameters of droplet initial size, humidity, vicinity, ventilation conditions and synchronization of exhalation were evaluated. Fine droplets and droplet nuclei were predicted to travel toward the upper part of the test room, whereas large droplets tend to be deposited on the floor. With a high relative humidity, 95%, most of the droplets were deposited on the floor within 16 seconds. Meanwhile, all of the droplets evaporated to droplet nuclei and remained suspended in the air when the relative humidity was 35%. Mixing ventilation that supplied fresh air with a ventilation rate of 5.6 h-1 resulted in drafts and strong turbulence, which made droplets and droplet nuclei dispersed in the room. The average vertical position was higher than that when the ventilation rate was 3.0 h-1. Displacement ventilation led to the vertical temperature stratification in the room. The vertical temperature gradient could neutralize the buoyancy force and weaken body plumes and the vertical dispersion of droplets and droplet nuclei. The inhalation of the droplets and droplet nuclei by the susceptible person and the deposition of the droplets and droplet nuclei on the body surface of the susceptible person were investigated at mutual distances of 0.5, 1.0, 1.5 and 3.0 m. For one breath from the source person, 1,600 droplets were released. Three and 9 droplet nuclei were inhaled by the susceptible person at a mutual distance of 0.5 and 1.0 m, respectively. No droplet nuclei were inhaled at 1.5 and 3.0 m. / published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

Infectious diseases control is one of the most important medical issues since the outbreak of SARS. The Hong Kong and China governments are awaked from the miserable event and a series of reforms relevant to infection control and public hygiene are thus established in order to face further challenges and potential threat in the future. In terms of strengthening health care system, re-orientation of healthy public policy, increment of community participation, building personal health skills as well as reinforcement of global communication and cooperation, there are drastically improvements regarding capacity for combating hazards due to emergence of novel infectious agents and diseases in both regions. This literature review aims to portrait current operating measures for infection control and public health practices in Hong Kong and the mainland China, and provides evaluation of the effectiveness and feasibility of these activities. / published_or_final_version / Public Health / Master / Master of Public Health

Cannabinoids suppress Th1 immunity in a variety of models including infection with the intracellular pathogen Legionella pneumophila (Lp). To examine the cellular mechanism of this effect, mouse bone marrow-derived dendritic cells (DCs) were studied following infection and drug treatment. DCs produced high levels of IL-12p40 following Lp infection. THC suppressed this cytokine response in a concentration-dependent manner and the endocannabinoids 2-arachidonoyolglycerol and virodhamine less potently suppressed cytokine production. DCs expressed mRNA for cannabinoid receptor 1 (CB1), CB2, and transient receptor potential vanilloid type 1 (TRPV1); furthermore, inhibition of Gi signaling by adding pertussis toxin completely attenuated the suppression induced by low concentrations of THC but not at high concentrations. In addition, the THC suppression was partially attenuated in DC cultures from CB1 and CB2 knockout mice and in cultures from normal mice co-treated with THC and cannabinoid receptor antagonists. Cytokine suppression was not attenuated by pretreatment with the TRPV1 antagonist capsazepine, suggesting that Gi signaling and cannabinoid receptors, but not TRPV1, are involved in THC-induced suppression of DC potential to polarize the development of naïve T cells to be Th1 cells. Besides IL-12, THC suppressed other DC polarizing characteristics such as the expression of MHC class II and co-stimulatory molecules CD86 and CD40, as well as the Notch ligand Delta 4. However, THC treatment did not affect other DC functions such as intracellular killing of Lp and Lp-induced apoptosis. Testing the capacity of THC to suppress DC polarizing function with T cells showed that DCs infected in vitro with Lp were able to immunize mice when injected prior to a lethal Lp infection; however, the immunization potential along with Th1 cytokine production was attenuated by THC treatment of the cells at the time of in vitro infection. In addition, THC-treated and Lp-infected DCs poorly stimulated primed splenic CD4 T cells in culture to produce IFN-gamma (IFN-y); however, this stimulating deficiency was reversed by adding recombinant IL-12p40 protein to the cultures. In conclusion, the data suggest that THC inhibits Th1 polarization by targeting essential DC functions such as IL-12p40 secretion and the maturation and expression of co-stimulatory and polarizing molecules.

The Gram-negative bacterium Legionella pneumophila is an intracellular parasite of aquatic protozoa. It exhibits a distinct dimorphic lifecycle that alternates between vegetative replicative form (RF) and infectious cyst-like form (CLF). Inadvertent inhalation of aerosolized CLFs by immunocompromised individuals leads to an infection in alveolar macrophages causing Legionnaires' disease. To further study a Legionella infection the use of the multicellular organism Caenorhabditis elegans was done. Differential Interference Contrast (DIC) microscopy of live L. pneumophila infected nematodes shows Legionella-containing vacuoles (LCVs) with motile forms. Transmission Electron Microscopy (TEM) defined the ultrastructure of L. pneumophila forms found in the primary infection site of the intestinal lumen and the secondary infection site in the gonadal tissues. These findings suggest the possible intracellular replication cycle of Legionella occurring in the gonadal tissues of the nematode. Providing insight and a plausible evolutionary origin of the ability of L. pneumophila to manipulate the macrophage innate immune system. / October 2014