Browsing by Author "Muturi, Margaret Wangui"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Determination of CD8+-cell responses in a high risk HIV negative population
    (2011-08-23) Muturi, Margaret Wangui
    Naturally acquired cellular immunity in individuals who have been exposed to HIV-1 but have remained uninfected may hold clues for the design of an effective HIV vaccine. IFNy Elispot has emerged as one of the widely used assay to monitor HIV-specific immune responses. It is becoming the assay of choice for evaluation of HIV-vaccine-induced cell-mediated immune responses in many clinical trials. The objective of this study was to investigate the CTL responses of high risk HIV seronegative individuals to HIV A and RENTA vaccine peptides. The study further sought to investigate whether it was possible to recruit, sample, counsel and follow-up a cohort of high risk seronegative volunteers over a duration time in preparation for vaccine trials. To achieve these objectives, 30 volunteers filled a questionnaire, were counseled, tested for HIV status, recruited and enrolled in a 15 month study.The thirty exposed seronegative (ES) volunteers reported frequent unprotected sex with people of unknown HIV-1 status at enrollment. Every 3 months the volunteers were seen at the KAVI Kangemi clinic where blood samples were taken for the determination of the CTL responses, their HIV status was re-checked, filled questionnaire to assess the changes in their risky sexual behaviour. It was possible to recruit and follow-up the 30 volunteers for the entire duration of the study. All the thirty samples did not show HIV-1 specific T cell responses to both RENTA and HIV-A peptides using the ex vivo Elispot assay during the four time points (months 0, 3, 6 and 9). To investigate whether these results were truly negative, samples from 5 seronegative discordant couples were used. There were no HIV-1 specific CD8+ IFNy T cell responses in the HIV negative spouse. To investigate whether the ex vivo Elispot was unable to detect the responses, cultured Elispot assay was applied to the samples. They all tested positive with variations between peptide pools and individuals. The fact that cultured Elispot detected the responses from the 5 seronegative spouses of HIV infected partners and from 12 of the thirty means that the ex vivo Elispot assay was not sensitive enough to detect responses to the tested vaccine peptides. Cultured Elispot expands the memory CTL thus enhancing the detection of the responses. Using this method it was possible to demonstrate that HIV-1 specific CD8+ IFNy T cell responses exist in high risk exposed seronegative individuals. Pool 90 gave positive responses with all the samples. It would appear that combining the pools of peptides would elicit consistent CD8+ IFNy T cell responses and therefore make a better vaccine candidate. The results suggest that there is need to exercise very stringent criteria for enrolling high risk exposed seronegative participants to any study group meant to investigate immunological parameters related to HIV exposure.
  • Thumbnail Image
    Item
    The Role of Schistosoma mansoni Eggs in Immune Protection against Plasmodium berghei Infected Mice
    (2014-02-17) Nyangahu, David Donald; Muturi, Margaret Wangui; Ochola, Lucy
    The co-occurrence of malaria and schistosomiasis is common in tropical regions of the world. Malaria induces a strong Th1 response while schistosomiasis skews the response to a Th2. Several studies demonstrate a non consistent effect of schistosomiasis infection on progression of malaria. On one hand, schistosomiasis infections protect against cerebral malaria while on the other hand, they are associated with increased malaria severity. This study examined the role of Schistosoma mansoni eggs on Plasmodium berghei malaria progression in BALB/c mice. The objectives were to determine the changes in Th1, Th2 cytokines and IgG levels which are markers associated with malaria and schistosomiasis protection and also determine if S. mansoni eggs lead to protection from P. berghei malaria. Two groups of mice were used: the experimental group and the control group. The experimental group was injected with a triple dose of S. mansoni eggs at ten day interval before being challenged with P. berghei. The control group was infected with P. berghei only. Five mice from both groups were euthanized at each time point (day 3, 6, 9 and 12 post challenge with P. berghei) and the spleen and serum collected. Five mice from each group were monitored throughout the experiment. Parasitaemia was monitored daily using Giemsa stained blood smears. The results showed that the experimental mice exhibited lower levels of P. berghei parasitaemia (15.52%) as compared to the controls (23.06%). However the difference was not significant (p>0.05). IgG levels were found to be higher in the experimental mice compared to controls due to stimulation by soluble egg antigen (SEA). The differences in IgG levels between the two study groups was not significant (p>0.05). The levels of IFN- γ and IL-4 were higher in the experimental mice than the control group though the difference was not significant (p=0.213). The levels of IgG and IL-4 in experimental mice could be responsible for the delay in death reported in these mice and enhanced survivorship. In conclusion, S. mansoni eggs did not induce significant differences in cytokine and IgG levels; nevertheless they contributed to delaying death in the experimental mice by two days by enhancing levels of IgG and IL-4. These findings provide a pointer for further research in this field using higher animal model such as the non human primates for a better understanding of the immunomodulatory role of schistosoma eggs on progression of malaria.
  • Thumbnail Image
    Item
    Seroprevalence and Genotypic Characterization of HBV among Low Risk Voluntary Blood Donors in Nairobi, Kenya
    (Springer Nature, 2020) Aluora, Patrick Okoti; Muturi, Margaret Wangui; Gachara, George
    Background: Hepatitis B virus (HBV) causes signifcant morbidity and mortality globally primarily due to its ability to cause hepatitis, liver cirrhosis and hepatocellular carcinoma. The Kenya National Blood Transfusion Services screens for Hepatitis B antibodies using the chemiluminescent microparticle immunoassay method. This test does not inform on the genotypic characteristics of the virus or the actual presence of the virus in blood. This study therefore sought to determine the serologic and genotypic profles of HBV circulating among the voluntary blood donors in Nairobi. Methods: Blood samples were collected in plain and EDTA vacutainers and tested for the Hepatitis B surface antigen (HBsAg). HBV DNA was then extracted from plasma, its overlapping P/S gene amplifed and sequenced. The resulting sequences were used to analyze for the circulating genotypes and mutations within the P and S genes. Bivariate statistical analysis was used to determine the association between demographic factors and HBV infection. Results: A seroprevalence of 2.3% (n=7) was reported. The age group 19–28 years was signifcantly associated with HBV infection. Nine samples were positive for HBV DNA; these included 2 HBsAg positive samples and 7 HBsAg negative samples. Genotype A, sub genotype A1 was found to be exclusively prevalent while a number of mutations were reported in the “a” determinant segment of the major hydrophilic region of the S gene associated with antibody escape. RT mutations including mutation rt181T in the P gene conferring resistance against Lamivudine and other ʟ-nucleoside drugs were detected. Conclusion: There is a high prevalence of occult HBV infections among these blood donors and therefore the testing platform currently in use requires revision. Keywords: Occult HBV infection, Hepatitis, Liver cirrhosis, Hepatocellular carcinoma, Mutations, Escape mutations, Undetectable