Department of Biochemistry and Microbiology

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Open Access
Further screening of Venda medicinal plants for activity against HIV type 1 reverse transcriptase and integrase
(2006-03-15) Bessong, Pascal O.; Rojas, Luis B; Obi, Larry C.; Tshisikhawe, Peter M.; Igunbor, Eunice O.
The use of medicinal plants for AIDS-related conditions is common in South Africa. In order to establish an antiviral rationale for the use of these plants we screened fractions of the methanol extracts of medicinal plants for activity against HIV-1 reverse transcriptase (RT) and integrase (IN). The n-butanol fraction obtained from the crude methanol extracts of the roots of Bridelia micrantha (Hochst) Baill. (Euphorbiaceae) was observed to be as the most active inhibiting the RNA-dependent-DNA polymerization (RDDP) activity of HIV-1 RT with an IC50 of 7.3 g/ml. However, it had no activity on the 3’-end processing activity of HIV integrase. Bioassay-guided fractionation of the n-butanol fraction yielded friedelin and -sistosterol, which did not inhibit the RDDP of RT or 3’-end processing functions of IN even at a concentration of 500 M. An uncharacterized fraction obtained in the bioassay-guided fractionating process inhibited the RDDP with an IC50 of 9.6 g/ml, but had no inhibition on IN. Phytochemical screening indicated the presence of flavonoids and tannins in the uncharacterized fraction.
Open Access
Drug Resistance Mutations in Naive HIV-1 South African Patients, and Construction of Molecular Clones to Phenotype Putative Resistance Mutations
(2009-03) Mavhandu, Lufuno Grace; Bessong, P. O.; Rekosh, David; Hammarskjold, Marie-Louise
See the attached abstract below
Open Access
In-vitro bioactivity of fractions from a local medicinal plant on HIV-1 replication, and selected fungal and bacterial pathogens
(2009-03) Mutshembele, Awelani Mirinda; Bessong, Pascal O.; Eloff, Jacobus N.; Obi, Larry
See the attached abstract below.
Open Access
Detection of Cryptosporidium species in stools of HIV/AIDS patients in Bela-Bela, South Africa
(2010-06) Makuwa, Stenly Modupi; Bessong, P. O.; Samie, A.; Potgieter, N.
See the attached abstract below
Open Access
Genetic characterization of human immunodeficiency virus from Northern South Africa
(2012-12-19) Iweriebor, Benson Chuks; Bessong, Pascal Obong; Mphahlele, Jeffrey; Moyo, Sylvester Rodgers
Open Access
Genetic analysis of HIV-1 integrase sequences from treatment naive individuals in Northeastern South Africa
(Molecular Diversity Preservation International (MDPI), 2013-03-01) Bessong, Pascal Obong; Nwobegahay, Julius
Raltegravir, an integrase inhibitor, is not a component of the current South African antiretroviral treatment guidelines, but it could be introduced in the near future as cases of virological failures from current treatment regimens begin to occur. The aim of this study was to analyze the complete HIV integrase gene obtained from individuals at two treatment sites in northeastern South Africa for the presence of Raltegravir associated drug resistant mutations and viral subtypes based on the integrase gene. Examination for mutations against other integrase inhibitors, such as Elvitegravir and Dolutegravir, was also done. Viruses from 127 treatment naive individuals were analyzed. Genetic drug resistance mutations were determined using the Stanford HIV Drug Resistance Interpretation program and the International AIDS society-USA guidelines. Viral subtyping was done by phylogenetic analysis, and recombinants were determined using the REGA, jpHMM and RIP tools. No major resistance mutations were detected. However, 7% of the sequences had minor mutations and polymorphisms. The majority (99%) of the viruses were HIV-1 C. Recombination analysis showed that the polymerase gene of one virus was likely composed of HIV-1 subtype A1 and C sequences. The present study indicates that Raltegravir, Elvitegravir and Dolutegravir resistant mutations may be absent in the study communities and further indicates the presence of recombinant viruses in northeastern South Africa.
Open Access
Immunodulation of inflammation in a murine pnemococcal sepsis model
(2013-10-01) Musie, Mbulaheni Edgar; Bessong, P. O.; Scheld, M. W.
Open Access
Studies on human immunodeficiency virus genetic drug resistance and subtype distribution in Northern South Africa
(2014-01-10) Nwobegahay, Julius; Bessong, Pascal O.; Selabe, Gloria
Open Access
Prevalence and molecular characterization of enteric viruses and their association with malnutrition in children less than two years old in the Vhembe Region of Limpopo Province, South Africa
(2014-01-10) Shivambu, Nurse; Samie, Amidou; Bessong, Pascal
Open Access
Genetic Variants of APOC3 Promoter and HLA-B genes in an HIV Infected Cohort in Northern South Africa: A Pilot Study
(Molecular Diversity Preservation International (MDPI), 2014-06-26) Masebe, Tracy; Bessong, Obong Pascal; Ndip, Roland Ndip; Meyer, Debra
Metabolic disorders and hypersensitivities affect tolerability and impact adherence to highly active antiretroviral therapy (HAART). The aim of this study was to determine the prevalence of C-482T/T-455C variants in the Apolipoprotein C3 (APOC3) promoter gene and Human leukocyte antigen (HLA)-B*57:01, known to impact lipid metabolic disorders and hypersensitivity respectively; and to correlate genotypes with gender, CD4+ cell count and viral load in an HIV infected cohort in northern South Africa. Frequencies of C-482 and T-455 polymorphisms in APOC3 were determined by restriction fragment length polymorphism analysis. Allele determination for HLA-B was performed with Assign SBT software in an HLA library. Analysis of APOC3 C-482 site revealed a prevalence of 196/199 (98.5%) for CC, 1/199 (0.5%) for CT and 2/199 (1.0%) for TT genotype (p = 0.000 with 1° of freedom; χ2 = 126.551). For the T-455 site, prevalences were: 69/199 (35%) for TT and 130/199 (65%) for the CC genotype (p = 0.000 with 1° of freedom; χ2 = 199). There was no association between gender and the presence of −482 (p = 1; χ2 = 0.00001) or −455 genotypes (p = 0.1628; χ2 = 1.9842). There was no significant difference in the increase in CD4+ cell count irrespective of genotypes. Significant increases in CD4+ cell count were observed in males and females considering the −455C OPEN ACCESS Int. J. Mol. Sci. 2014, 15 11404 genotype, but not in males for the −455T genotype. Viral load decreases were significant with the −455C and −482C genotypes irrespective of gender. HLA-B*57:01 was not identified in the study cohort. The apparently high prevalence of APOC3 T-455CC genotype needs confirmation with a larger samples size and triglyceride measurements to support screening of patients to pre-empt HAART associated lipid disorders.
Open Access
Molecular diagnosis and characterization of clinical isolates of entamoeba histolytica, giadia lamblia and cyptosporidium species from the United Arab Emirates and South Africa
(2014-11-03) ElBakri, Ali Mohammed Kamal; Bessong, P. O.; Potgieter, N.; AbuOdeh, R. O
Open Access
Studies on HIV-1 subtype c drug susceptibility : development of a phenotypic resistance assay and evaluation of plant-derived compounds
(2014-11-03) Mavhandu, Lufuno Grace; Bessong, Pascal. Obong; Rekosh, David.; Hammarskjold, Marie-Lou
Open Access
Prevalence and molecular identification of candida oral infections in HIV patients attending treatment centres, Vhembe District, Limpopo Province
(2014-11-03) Mashao, Mmbangiseni Beauty; Samie, A.
Open Access
Expression of an active HIV-1 subtype C protease
(2014-11-03) Tambani, Tshifhiwa; Bessong, Pascal. O.; Tebit, Denis.
Open Access
HIV co-infections with cytomegalovirus, hepatitis c virus and human papillomavirus in northern South Africa
(2014-11-03) Rikhotso, Mikateko; Bessong, P. O.; Tebit, Denis.
Open Access
Molecular detection of norovirus GI ang GII genotypes in children less than two years of age and impact on child growth
(2014-11-03) Moloro, Glenton Thabo; Samie, A.; Bessong, P. O.
Open Access
Characterization of heat shock protein 70-z (PfHsp70-z) from plasmodium falciparium
(2015) Zininga, Tawanda; Shonhai, Addmore; Burger, A.
Malaria is a parasitic disease that accounts for more than 660 thousand deaths annually, mainly in children. Malaria is caused by five Plasmodium species P. ovale, P. vivax, P. malariae, P. falciparum and P. knowlesi. The most lethal cause of cerebral malaria is P. falciparum. The parasites have been shown to up-regulate some of their heat shock proteins (Hsp) in response to stress. Heat shock protein 70 (called DnaK in prokaryotes) is one of the most prominent groups of chaperones whose role is central to protein homeostasis and determines the fate of proteins. Six Hsp70 genes are represented on the genome of P. falciparum. The Hsp70 genes encode for proteins that are localised in different sub-cellular compartments. Of these two occur in the cytosol, PfHsp70-z and PfHsp70-1; two occur in the endoplasmic reticulum, PfHsp70-2 and PfHsp70-y; one in the mitochondria, PfHsp70-3 and one exported to the red blood cell cytosol, PfHsp70-x. PfHsp70-1 is a well characterized canonical Hsp70 involved in prevention of protein aggregation and facilitates protein folding. Little is known about PfHsp70-z. PfHsp70-z was previously shown to be an essential protein implicated in the folding of proteins possessing asparagine rich repeats. However, based on structural evidence PfHsp70-z belongs to the Hsp110 family of proteins and is thought to serve as a nucleotide exchange factor (NEF) of PfHsp70-1. The main aim of this study is to elucidate the functional roles of PfHsp70-z as a chaperone and its interaction with PfHsp70-1. In the current study, PfHsp70-z was cloned and expressed in E. coli JM109 cells. This was followed by its purification using nickel chromatography. The expression of PfHsp70-z in parasites cultured in vitro was investigated and its association with PfHsp70-1 was explored using a co-immuno precipitation assay. PfHsp70-z expression in malaria parasites is up regulated by heat stress and the protein is heat stable based on investigations conducted using Circular Dichroism. Furthermore, the direct interaction between recombinant forms of PfHsp70-z and PfHsp70-1 were investigated using slot blot and surface plasmon resonance assays. PfHsp70-z was observed to exhibit ATPase activity. In addition, the direct interaction between PfHsp70-z and PfHsp70-1 is promoted by ATP. Based on limited proteolysis and tryptophan fluorescence analyses, PfHsp70-z binds ATP to assume a unique structural conformation compared to the conformation of the protein bound to ADP or in nucleotide-free state. PfHsp70-z was able to suppress the heat-induced aggregation of malate dehydrogenase and luciferase in vitro. Interestingly, while ATP appears to modulate the conformation of PfHsp70-z, the chaperone function of PfHsp70-z was not influenced by ATP. Altogether, these findings suggest that Characterization of Heat Shock Protein 70-z (PfHsp70-z) from Plasmodium falciparum iii PfHsp70-z serves as an effective peptide substrate holding chaperone. In addition, PfHsp70-z may also serve as the sole nucleotide exchange factor of PfHsp70-1. The broad spectrum of functions of this protein, could explain this PfHsp70-z is an essential protein in malaria parasite survival. This is the first study to show that PfHsp70-z possess independent chaperone activity and that it interacts with its cytosolic counterpart, PfHsp70-1 in a nucleotide dependent fashion. Furthermore, the study shows that PfHsp70-z is a heat stable molecule and that it is capable of forming high order oligomers.
Open Access
Pathogen-specific burdens of community diarrhoea in developing countries: a multisite birth cohort study (MAL-ED)
(Lancet Glob Health, 2015) Platts-Mills, James A.
Background Most studies of the causes of diarrhoea in low-income and middle-income countries have looked at severe disease in people presenting for care, and there are few estimates of pathogen-specifi c diarrhoea burdens in the community. Methods We undertook a birth cohort study with not only intensive community surveillance for diarrhoea but also routine collection of non-diarrhoeal stools from eight sites in South America, Africa, and Asia. We enrolled children within 17 days of birth, and diarrhoeal episodes (defi ned as maternal report of three or more loose stools in 24 h, or one loose stool with visible blood) were identifi ed through twice-weekly home visits by fi eldworkers over a follow-up period of 24 months. Non-diarrhoeal stool specimens were also collected for surveillance for months 1–12, 15, 18, 21, and 24. Stools were analysed for a broad range of enteropathogens using culture, enzyme immunoassay, and PCR. We used the adjusted attributable fraction (AF) to estimate pathogen-specifi c burdens of diarrhoea. Findings Between November 26, 2009, and February 25, 2014, we tested 7318 diarrhoeal and 24 310 non-diarrhoeal stools collected from 2145 children aged 0–24 months. Pathogen detection was common in non-diarrhoeal stools but was higher with diarrhoea. Norovirus GII (AF 5·2%, 95% CI 3·0–7·1), rotavirus (4·8%, 4·5–5·0), Campylobacter spp (3·5%, 0·4–6·3), astrovirus (2·7%, 2·2–3·1), and Cryptosporidium spp (2·0%, 1·3–2·6) exhibited the highest attributable burdens of diarrhoea in the fi rst year of life. The major pathogens associated with diarrhoea in the second year of life were Campylobacter spp (7·9%, 3·1–12·1), norovirus GII (5·4%, 2·1–7·8), rotavirus (4·9%, 4·4–5·2), astrovirus (4·2%, 3·5–4·7), and Shigella spp (4·0%, 3·6–4·3). Rotavirus had the highest AF for sites without rotavirus vaccination and the fi fth highest AF for sites with the vaccination. There was substantial variation in pathogens according to geography, diarrhoea severity, and season. Bloody diarrhoea was primarily associated with Campylobacter spp and Shigella spp, fever and vomiting with rotavirus, and vomiting with norovirus GII. Interpretation There was substantial heterogeneity in pathogen-specifi c burdens of diarrhoea, with important determinants including age, geography, season, rotavirus vaccine usage, and symptoms. These fi ndings suggest that although single-pathogen strategies have an important role in the reduction of the burden of severe diarrhoeal disease, the eff ect of such interventions on total diarrhoeal incidence at the community level might be limited.
Open Access
Application of cloning in the detection of HIV-1 and drug resistant minority populations
(2015-01-14) Hatyoka, Luiza Miyanda; Bessong, T. M.; Masebe, Tracy. M.
Open Access
Screening of herbal preparation (Pheko) for anti HIV-1 replication properties
(2015-01-14) Matume, Nontokozo Daphney; Bessong, P. O.; Sekhoacha, M.