Browsing by Author "Kituyi, Sarah N."

Now showing 1 - 6 of 6
  • No Thumbnail Available
    Item
    Geographic Distribution of Rabies Virus and Genomic Sequence Alignment of Wild and Vaccine Strains, Kenya
    (UoEm, 2024-08-08) Wambugu, Evalyne N.; Kimita, Gathii; Kituyi, Sarah N.; Washington, Michael A.; Masakhwe, Clement; Mutunga, Lucy M.; Jaswant, Gurdeep; Thumbi, S.M.; Schaefer, Brian C.; Waitumbi, John N.
    Rabies, a viral disease that causes lethal encephalitis, kills ≈59,000 persons worldwide annually, despite availability of effective countermeasures. Rabies is endemic in Kenya and is mainly transmitted to humans through bites from rabid domestic dogs. We analyzed 164 brain stems collected from rabid animals in western and eastern Kenya and evaluated the phylogenetic relationships of rabies virus (RABV) from the 2 regions. We also analyzed RABV genomes for potential amino acid changes in the vaccine antigenic sites of nucleoprotein and glycoprotein compared with RABV vaccine strains commonly used in Kenya. We found that RABV genomes from eastern Kenya overwhelmingly clustered with the Africa-1b subclade and RABV from western Kenya clustered with Africa-1a. We noted minimal amino acid variances between the wild and vaccine virus strains. These data confirm minimal viral migration between the 2 regions and that rabies endemicity is the result of limited vaccine coverage rather than limited efficacy.
  • Thumbnail Image
    Item
    In vitro anti-cancer efficacy and phyto-chemical screening of solvent extracts of Kigelia africana (Lam.) Benth
    (Heliyon, 2020) Mukavi, Justus Wambua; Mayeku, Philip Wafula; Nyaga, Justin M.; Kituyi, Sarah N.
    Background and objectives: Kigelia africana is a medicinal plant growing naturally in many parts of Africa. In Kenya, a water concoction of the plant is used to treat breast and prostate cancers. Laboratory data on its anti-cancer activity and active principles is limited, hence no scientific rationale for its medicinal use. This study reports on in-vitro toxic activities of dichloromethane and methanol extracts of the plant against human breast cancer cells and phytochemical screening of the two extracts. Methodology: Plant extracts were obtained by sequential solvent extraction of dry plant material (stem bark) using analytical grade dichloromethane: methanol (1:1) and methanol (Sigma Aldrich). In-vitro anti-cancer activities of the extracts were determined using the suphorhodamine (SRB) assay against a human breast cancer cell line (HCC 1937). Preliminary Thin layer chromatography of plant extracts was done using POLYGRAM® SIL G/UV254 plates (Merck) to establish presence of different classes of secondary metabolites. Results: In-vitro cytotoxic activities of the two extracts were significantly different (P ¼ 0.05). The methanol extract exhibited higher activity (IC50 ¼ 55.01 μg/ml). Phyto-chemical screening of the two extracts revealed the presence of terpenoids, phenols, steroids 26.02 μg/ml) compared to that of dichloromethane: methanol (1:1) (IC50 ¼ and flavonoids. Conclusion: The high in-vitro anti-cancer activities of solvent extracts of Kigelia africana justify its use in traditional medicine to manage breast cancer. Phytochemical analysis of the extracts reveal similar profiles hence the differences in their anti-cancer activities can be attributed to quantitative variations of various classes of secondary metabolites.
  • No Thumbnail Available
    Item
    March 2019 dengue fever outbreak at the Kenyan south coast involving dengue virus serotype 3, genotypes III and V
    (Plos, 2022-03) Muthanje, Eric M.; Kimita, Gathii; Nyataya, Josphat; Njue, Winrose; Mulili, Cyrus; Mugweru, Julius; Mutai, Beth; Kituyi, Sarah N.; Waitumbi, John
    The first description of a disease resembling dengue fever (DF) was in the 15 century slave trade era by Spanish sailors visiting the Tanzania coast. The disease, then associated with evil spirits is now known to be caused by four serotypes of dengue virus (DENV1-4) that are transmitted by Aedes mosquitoes. Kenya has experienced multiple outbreaks, mostly associated with DENV-2. In this study, plasma samples obtained from 37 febrile patients during a DF outbreak at Kenya’s south coast in March 2019 were screened for DENV. Total RNA was extracted and screened for the alpha- and flavi-viruses by real-time polymerase chain reaction (qPCR). DENV-3 was the only virus detected. Shotgun metagenomics and targeted sequencing were used to obtain DENV whole genomes and the complete envelope genes (E gene) respectively. Sequences were used to infer phylogenies and time-scaled genealogies. Following Maximum likelihood and Bayesian phylogenetic analysis, two DENV-3 genotypes (III, n = 15 and V, n = 2) were found. We determined that the two genotypes had been in circulation since 2015, and that both had been introduced independently. Genotype III’s origin was estimated to have been from Pakistan. Although the origin of genotype V could not be ascertained due to rarity of these sequences globally, it was most related to a 2006 Brazilian isolate. Unlike genotype III that has been described in East and West Africa multiple times, this was the second description of genotype V in Kenya. Of note, there was marked amino acid variances in the E gene between study samples and the Thailand DENV-3 strain used in the approved Dengvaxia vaccine. It remains to be seen whether these variances negatively impact the efficacy of the Dengvaxia or future vaccines.
  • No Thumbnail Available
    Item
    Molecular Phylogeny of Selected Kenyan Eucalyptus Species Inferred from MatK, rbcL and TrnL-F Genes and Their Suitability for Power Transmission Poles
    (MDPI, 2022-04) Chebet, Daisy; Musila, Fredrick M.; Kituyi, Sarah N.; Muthike, George M.; Kaigongi, Magrate M.
    Genus Eucalyptus belongs to the family Myrtaceae and consists of more than 900 species, various hybrids and varieties. The major species that are grown in Kenya are Eucalyptus grandis, E. globulus, E. saligna and E. camaldulensis. Most Eucalyptus species are highly dependent on rainfall and this is challenged by climatic changes owing to global warming making it difficult to effectively match the availability of mature trees and the market demand especially for use as power transmission poles. With the widespread availability of other naturally occurring Eucalyptus species such as E. camaldulensis and E. globulus, it becomes important to determine the genetic diversity and to analyze the phenotypic traits of these species for suitability as power transmission poles in order to counter the overdependence on E. grandis. Phenotypic traits investigated included measuring total tree height and diameter at breast height (DBH), while molecular data were obtained from sequencing MatK, rbcL and TrnL-F genes from selected species and evolutionary analyses such as nucleotide substitution rates, base composition disparity indices, evolutionary divergence, nucleotide diversity indices and phylogeny construction were conducted in MEGA 11. Significant differences in DBH and height among Eucalyptus species were observed when the phenotypic data were subjected to ANOVA. In this study, E. robusta, E. paniculata, E. maculata, E. dunnii, E. camaldulensis and E. citriodora are fit to be used as power transmission poles but they are limited by their short height. However, E. tereticornis and E. glaucina have the desired DBH and height and hence can be used as substitutes for E.grandis. Generally, the molecular phylogeny study has shown that the studied Eucalyptus species are closely related and form various monophyletic clades which can be attributed to the short genetic distances, low substitution rates, low nucleotide bias disparity indices and low diversity scores. Further phylogenetic and gene expression studies involving more Eucalyptus species are needed to better understand Eucalyptus phylogeny, and diversity and identify species with similar genetic make-up to that of E. grandis which has been used extensively for the provision of electricity transmission poles.
  • Thumbnail Image
    Item
    Uncovering disease determinants of Covid-19 through analysis of its molecular evolution
    (African Journal of Biological Sciences, 2020-07) Muthanje, Eric M.; Amwoma, Joseph G.; Kituyi, Sarah N.
    Covid-19 was first reported in Wuhan China but has now spread globally with overwhelming impacts on human health and health systems. The disease is caused by the SARs-Cov-2 which is related to the SARs-Cov-1 that causes SARs. There is evidence suggesting that the virus originated from the Rhinolophilid bats and has subsequently undergone recombination to allow for a natural selection for a human host and it is thought that the recombination might have occurred either prior or upon infection of the human host. These events of natural selection are presumed to have hastened human to human transmission. However, analyses of sequences from Covid-19 isolates from China and across the globe point to a unique case scenario that may suggest selection and evolution of the virus upon infection of the human host. In this paper we have examined the role of the human ACE-2 receptor in determining the predisposition to Covid-19 and analyzed Covid-19 sequences deposited in the virus database from around the globe to provide evidence that the disease burden is different across regions and among individuals as determined by the genetics of the virus and that the virus is rapidly evolving across regions and populations. Our phylogenetics data confirms that all strains circulating around the globe are related to the strains from China, the origin of the virus and further depicts varying degrees of similarity and disparity which suggests that the virus is mutating. While the USA has already been shown to have sequences closely related to the Wuhan sequences, here we report that the sequences from Spain and Africa are distantly related to the Wuhan sequences. Owing to the unique presentation of the disease in regions across the globe, the summary presented here informs of the need to tailor the management of the disease as dictated by viral and host genetic factors and the observed regional burden of the disease.
  • Thumbnail Image
    Item
    Uncovering disease determinants of Covid-19 through analysis of its molecular evolution
    (2020-07) Muthanje, Eric M.; Amwoma, Joseph G.; Kituyi, Sarah N.
    Covid-19 was first reported in Wuhan China but has now spread globally with overwhelming impacts on human health and health systems. The disease is caused by the SARs-Cov-2 which is related to the SARs-Cov-1 that causes SARs. There is evidence suggesting that the virus originated from the Rhinolophilid bats and has subsequently undergone recombination to allow for a natural selection for a human host and it is thought that the recombination might have occurred either prior or upon infection of the human host. These events of natural selection are presumed to have hastened human to human transmission. However, analyses of sequences from Covid-19 isolates from China and across the globe point to a unique case scenario that may suggest selection and evolution of the virus upon infection of the human host. In this paper we have examined the role of the human ACE-2 receptor in determining the predisposition to Covid-19 and analyzed Covid-19 sequences deposited in the virus database from around the globe to provide evidence that the disease burden is different across regions and among individuals as determined by the genetics of the virus and that the virus is rapidly evolving across regions and populations. Our phylogenetics data confirms that all strains circulating around the globe are related to the strains from China, the origin of the virus and further depicts varying degrees of similarity and disparity which suggests that the virus is mutating. While the USA has already been shown to have sequences closely related to the Wuhan sequences, here we report that the sequences from Spain and Africa are distantly related to the Wuhan sequences. Owing to the unique presentation of the disease in regions across the globe, the summary presented here informs of the need to tailor the management of the disease as dictated by viral and host genetic factors and the observed regional burden of the disease.