The Adames strain of Punta Toro virus (PTV-A) causes acute hepatic disease in hamsters and mice similar to that seen in natural Rift Valley fever virus (RVFV) infection, while the Balliet strain (PTV-B) is apathogenic. The ability of PTV-A to suppress the interferon (IFN) response has been demonstrated in hamsters and is thought to be a contributing factor to PTV-A's pathogenicity in hamsters. PTV-B is not assumed to exhibit this IFN-antagonistic activity, as it stimulates production of significantly higher IFN-β levels. To elucidate the role of IFN in resistance of mice to PTV-B infection, we utilized mice deficient in a critical IFN signaling protein, STAT-1. We found that these mice were drastically more susceptible to PTV-B, which caused 100% lethality compared to 0% in their wild-type counterparts. STAT-1 deficient mice were also more susceptible to PTV-A, as these mice succumbed to infection significantly earlier than wild-type mice (p=0.0058). We sought to determine whether PTV-A's IFN-antagonistic mechanism is functional in mice by examining expression of IFN-β in primary macrophages infected with either strain. We found that IFN-β protein concentration is higher in samples taken from PTV-B-infected cells. We employed quantitative PCR arrays specific to IFN signaling and response pathways to evaluate changes in gene expression throughout the course of infection with either virus strain. We found several genes with differentially regulated expression between PTV-A- and PTV-B-infected macrophages, including Ifnβ1 and multiple Ifnα subtypes. Also, several genes coding for inflammatory and chemotactic molecules, Cxcl11, Cxcl10, Cxcl9, Vcam1, and Il6, demonstrated increased expression in PTV-B samples compared to PTV-A. Of particular interest, Isg20, a 3'-5' exonuclease with specificity for single-stranded RNA, was stimulated ~2-fold higher by PTV-B, and Iigp1, from the family of GTPases associated with host defense against intracellular pathogens, was stimulated ~2.7-fold higher by PTV-B. The individual functions of each of these genes in mouse resistance to PTV-B could be a focus of future studies to better understand essential host defense mechanisms to phleboviral infection.

Diss. (sammanfattning) Umeå : Umeå universitet, 2010. / Härtill 4 uppsatser.

Call number: LD2668 .T4 1960 N53

No description available.

Asthma and hayfever are common diseases in children and adults. There have been dramatic increases in the prevalence of allergic diseases over the last 25 years. Either the environment has become more toxic or the population more susceptible. Concern has been expressed that cultivation of oilseed rape leads to seasonal epidemics of respiratory symptoms in populations living near the crop. In order to investigate this apparently widespread problem a combined epidemiological and environmental study was carried out. A cross sectional study was conducted to determine the prevalence of symptoms in a rape growing area compared with a non-rape area. Detailed environmental sampling and a small case-control study to investigate atopy and bronchial reactivity were also conducted. There have been dramatic changes in the Western diet over the last 30 years, with the diet including progressively less fresh food containing antioxidants. It is possible that these changes have increased the susceptibility of the populations to potentially harmful substances. A case-control study was conducted to test the hypothesis that a diet low in antioxidants is a factor in the expression of allergic diseases. Seasonal symptoms were found to be widespread in both rape growing and non-rape growing areas, with only a very small excess of seasonal symptoms occurring in rape growing areas. Little evidence of allergy to oilseed rape, which is consistent with the low levels of pollen recorded, was found. However, there was an increase in bronchial reactivity during the flowering season, especially among cases. This could be a result of non-specific irritation due to terpenes released from the crop.

Rift Valley fever virus (RVFV) is a Phlebovirus member of the Bunyaviridae family and it is the causative agent of Rift Valley fever (RVF), a mosquito-borne viral zoonotic disease that poses a significant threat to domestic ruminants and human health in Africa. The RVFV is an encapsulated, negative-sense, single-stranded RNA virus with a tripartite segmented genome, containing L (large), M (medium) and S (small) segments. The S segment codes for two proteins, namely the nucleocapsid (N) protein and non-structural protein (NSs). There is evidence that the NSs protein is involved in virulence by blocking the expression of the interferon beta (IFN-β) promoter. It has been recently demonstrated that the SAP30-NSs-YY1 multiprotein complex represses the IFN-β promoter. Consequently, the interferon expression is blocked, allowing virus to replicate. A total of 45 isolates of RVFV recovered over a period of 53 years in 14 African countries, Madagascar and Saudi Arabia were characterized by full sequencing of the S segment of the virus. This data was added to another 27 strains of RVFV available on GenBank for phylogenetic analysis using MEGA4, giving a total of 72 strains analyzed. Alignments were made of the entire S segment, the NSs gene, the N gene, and their deduced amino acid sequences. The laboratory strains, clone 13, MP12 and Smithburn, were also included in the alignments. Two isolates were passaged ten times through two different amplification systems to asses the potential for sequence variation to occur in the original material through routine laboratory manipulations. Sequencing data was generated from the virus RNA present in the original clinical specimens and from the extracted RNA from the tenth passage of virus in each amplification system. The results showed 100% homology for each respective isolate, demonstrating that the RVFV S segment remained stable during ten serial passages in different propagation systems. Phylogenetic analysis was conducted on the naturally occurring RVFV strains (n = 72) and the findings indicate that circulating strains are compartmentalized and belong to one of three major lineages, namely Egyptian, western African, and central, eastern and southern African. The strains clustered in the Egyptian lineage had an average p-distance of 1.0%, the western African strains 0.9%, and the central, southern and eastern African strains 2.0%. The overall average p-distance was 2.5%, with a range from 0 to 4.1%. For the N gene, the range was from 0 to 4.2%, with an average of 2.2%. For the N protein, the range was from 0 to 2%, with an average of 0.2%. The NSs gene had a range of 0 to 4.6%, with an average of 2.4%. The NSs protein had a range of 0 to 3.8%, with an average of 1.7%. The intergenic region (IGR) had a range of 0 to 9.2%, with an average of 4.8%. Results of the study suggest that RVF outbreaks can result from either the rapid spread of a single strain over vast distances or from an increased activity of a strain circulating at an endemic level within an area/region during prolonged dry periods. Sequencing alignment showed that the length of the S segment ranged from 1690 to 1692 nucleotides. This difference in length was due to insertions and deletions found in the IGR, which is also the region with the most sequence divergence (4.8%). Both the NSs and N genes had neither insertions nor deletions, and were both found to be stable, though the NSs gene was slightly more variable than the N gene (2.5% versus 2.2%) The deduced amino acid sequences of the NSs protein were considerably more variable than that of the N protein (1.7% versus 0.2%). Alignment of the NSs protein demonstrated that the 5 cysteine residues at positions 39, 40, 150, 179 and 195, are highly conserved among the isolates analyzed. These residues are important for conservation of the three-dimensional structure of the protein and the formation of filamentous structures observed in cells infected with natural strains of RVFV. The NSs protein is now implicated as the major factor of virulence and that its pathogenicity is associated with the blocking of interferon production. Therefore, any amino acid changes that result in changes to the filamentous structure of the NSs protein might impact on the binding kinetics between the NSs protein, SAP30 (Sin3A Associated Protein 30) and YY1 (Yin Yang-1). There were 6 amino acid changes in the NSs-SAP30 binding domain, with one being unique to the live-attenuated Smithburn vaccine strain. Generated sequencing data contributes to global phylogenetic characterization of RVFV isolates and and molecular epidemiology of the virus. In addition, findings of this study will further aid investigation on reassortment events occurring between strains of RVFV and genetically related viruses, the role of the NSs protein in the replicative cycle of the virus, the pathogenic effects of the NSs protein within the RVFV-infected host cells, and might help to identify molecular basis of RVFV virulence.

A dissertation submitted to the Faculty of Health Sciences University of the Witwatersrand, Johannesburg for the degree of Master of Science. / The Special Pathogens Unit (SPU) of the National Institute for Virology has diagnosed a total of 158 cases of Crimean-Congo haemorrhagic fever (CCHF) from the time that the disease was first recognized in South Africa in 1981 up until the end of 2000. The virus has a propensity to cause nosocomial infections, and consequently rapid diagnosis is important for the isolation of the patient and the institution of barrier-nursing to protect medical staff and the community at large. Thus it is essential that the SPU should have the latest diagnostic and research tools available. Diagnosis of CCHF is generally confirmed by isolation of the virus, detection of viral RNA amplified by reverse transcriptase polymerase chain reaction (RT-PCR), demonstration of seroconversion or a >4-fold increase in IgG antibody titre, or detection of specific IgM antibody activity. Virus can be isolated in 1-6 days in cell culture, but the method is less sensitive for the isolation of low concentrations of virus than the use of suckling mice which, however, takes 7-9 days.

A thesis submitted to the Faculty of Medicine, University o-f the Witwatersrand, Johannesburg, ■for the degree o-f Master o-f Science. Johannesburg, 1990. / In this thesis the role of essential fatty acids (EFAs) in thermoregulation and the polyunsaturates (PUFA) in the genesis of fever is investigated. Although recognised, that metabolites of arachidonic acid are involved in the biochemical sequences leading to fever, it is also acknowledged that fever response depends on lipid mobilisation. However, the exact biochemical mechanisms involved in this event remain unknown to date. In order to investigate a relation between serum lipids and fever, rabbits were subjected to dietary manipulation (deficient, or excessive EFA diet) and their hyperthermic responses to intravenous injections of (a) human leucocyte pyrogen (HLP); (b) endotoxin (Salmonella Thyphosa); and (c) cerebroventricular injections of prostaglandin E2» were compared with rabbits fed on a normal diet / IT2018

Enteric fever continues to affect people living in endemic settings substantially causing at least 20 million cases of febrile illnesses every year with 1% mortality. Over the last decade there has been considerable debate surrounding the burden and disease profile of enteric fever in the paediatric population. This is partially due to the similarity of the clinical features of paediatric enteric fever to most other febrile illness seen in endemic settings. The treatment of enteric fever is proving to be a challenge with the emergence of antimicrobial resistant strains, particularly the 4.3.1 genotype (H58 haplotype), which is spreading rapidly. Multi-drug resistant (MDR) enteric fever, defined as infection with typhoidal Salmonellae that exhibit a combined resistance to ampicillin, cotrimoxazole and chloramphenicol emerged in the 1990s and was mediated primarily via the 4.3.1 genotype population through the horizontal acquisition of antimicrobial resistance determinants. Subsequently, fluoroquinolones became the drug of choice and the treatment of enteric fever following which fluoroquinolone resistance emerged, again through the 4.3.1 genotype. However, these antimicrobial trends may not be uniform across endemic regions and an understanding of these differing patterns as well the temporal changes in these trends are important in planning treatment strategies. In the short and medium term work needs to be focused on achieving the greatest benefits from the prudent use of the recently WHO pre-qualified Vi-TT conjugate vaccine candidate. Whilst the long term vision towards eradicating enteric fever needs to focus on better understanding the underlying the biology of this disease through the use of contemporary technologies while simultaneously improving infrastructure for the provision of clean water, adequate sanitation and hygiene. This thesis aims to age-characterise the disease burden of typhoid fever in endemic regions of South and South-East Asia as well as the African continent. Following this, the molecular epidemiology of enteric fever in two endemic settings in the Indian subcontinent is delineated with a keen focus on the 4.3.1 genotype (H58) population as well the phenotypic patterns and molecular determinants of antimicrobial resistance. This thesis finally systematically reviews the global trends of antimicrobial resistance of S. Typhi isolates over time both from a phenotypic and molecular perspective. The key results from this thesis include; the age stratification of disease occurrence in endemic regions which showed a substantial proportion occurs in the youngest age group in both Africa and Asia, the uniform dominance of 4.3.1 genotypes conferring a high degree of fluoroquinolone resistance contrary to earlier suggestions of younger children being more susceptible to a broader range of infecting genotypes, the dissimilarities between the antimicrobial resistance carrying capabilities of lineage I and lineage II strains of the 4.3.1 genotype as well as novel AMR gene arrangements and finally the temporal trends of AMR in S. Typhi which were different between Asia an Africa. The high prevalence of lineage I strains in Africa and South-East Asia in contrast to the high prevalence of lineage II strains in the Indian subcontinent reflect the antimicrobial selection pressures as well the evolutionary characteristics of circulating pathogen populations in these regions. The implications of the data reported in this thesis have implications for treatment and prevention strategies. For the first time in history an opportunity has risen to effectively vaccinate the youngest age group (0-4 years) from typhoid through the Vi-TT conjugate vaccine. As highlighted in this thesis the youngest age group (0-4 years) have a high disease occurrence in endemic areas as seen in a meta-analysis as well as through data from two endemic sites collated and reported in this thesis. The older age groups also suffer greatly from this disease calling for a broad based vaccine strategy. The implications for treatment of enteric fever are however more relevant in the immediate term which suggest that in endemic regions in Asia, fluoroquinolones have little role to play in treatment protocols while fluoroquinolones are still relevant in the African setting. In Asia, reverting back to former first-line antimicrobials might be an option but the possibility of re-emergence of widespread resistance to these currently sensitive antimicrobials is very high exemplifying the ability of S. Typhi to adapt to changing antimicrobial pressures.

Thesis (M.Sc.( Medical Sciences)) --University of the North, 1983 / Refer to the document