Browsing by Author "Engelbrecht, S."
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- ItemCharacterisation of new full-length HIV-1 subtype D viruses from South Africa(2004-12) Loxton, Andre Gareth; Janse van Rensburg, E.; Engelbrecht, S.ENGLISH ABSTRACT: The first episode of HIV-1 in South Africa was documented in 1982. Homosexual transmission of the virus was the predominate mode of transmission in an epidemic of mainly HIV-1 subtype Band D infections. To date, no full-length sequences of Subtype D strains from South Africa has been reported. Here we describe the characterization and some of the unique features of the Tygerberg HIV-1 subtype D strains. A near full-length 9 kb fragment was obtained through a one step PCR using high molecular weight DNA. Cloning was done successfully with the pCR-XLTapa cloning kit. Large quantities of plasmid DNA was grown and sequenced on both strands of the DNA. ORF determination and subtyping was followed by standard phylogenetic methods to construct evolutionary phylogenetic trees. Subtyping and similarity plots revealed that the sequences from Tygerberg are pure subtype D. All the Tygerberg strains had intact genes with no premature stop codons. At the tip of the V3 loop, the Tygerberg strains have the GOGO motif. R214 has a more variable vpu gene than the rest of the Tygerberg strains, but is still subtype D in this region. No premature stop codons have been observed in the tat gene and the glycosilation of the strains are less than the subtype D consensus. We are the first to report full-length sequences of HIV-1 subtype D strains from South Africa. The sequences represent non-mosaic genomes of subtype D. Our results confirm that the subtype D sequences from the beginning of the HIV-1 epidemic differ from the Subtype D sequences from recent isolates.
- ItemIsolation of a new human herpesvirus producing a lytic infection of helper (CD4) T-lymphocytes in peripheral blood lymphocyte cultures. Another cause of acquired immunodeficiency(Health & Medical Publishing Group, 1988-12) Becker, W. B.; Engelbrecht, S.; Becker, M. L. B.; Piek, C.; Robson, B. A.; Wood, L.; Jacobs, P.A new human helper (CD4) T-lymphotropic herpesvirus (HTLHV) was first isolated in February 1985 from the cultured peripheral blood lymphocytes (PBL) of a patient with the acquired immunodeficiency syndrome, and subsequently from the PBL of 1 patient with hairy cell leukaemia and 2 patients with lymphoproliferative disease associated with human T-lymphotropic virus type I infection. The viruses could be serially subcultured in umbilical cord PBL cultures in which they infected helper (CD4) T-lymphocytes producing multinucleate giant cells with intranuclear inclusions followed by cell lysis. Electron microscopy of infected cultures revealed that the isolates were herpesviruses. Specific DNA probing showed that the 4 isolates were related to one another but were distinct from cytomegalovirus, Epstein-Barr virus, Herpes-virus hominis types 1 and 2, and varicella-zoster virus. HTLHV lyses the same target cell as human immunodeficiency virus in PBL cultures suggesting that it may have a similar potential to cause acquired immune deficiency. The development of an unequivocally diagnostic serological test is a priority, so that the epidemiology and pathogenesis of HTLHV infection can be studied.
- ItemIsolation of human T-lymphotropic virus type I (HTLV-I) from a black South African with Kaposi's sarcoma(Health & Medical Publishing Group, 1988) Becker, W. B.; Botha, M. C.; Engelbrecht, S.; Becker, M. L. B.Serological evidence for HTLV-I infection in the South African population has now been confirmed by the isolation of the virus from the peripheral blood lymphocytes of an adult Tsonga male. The subject was an indigenous black man from the south-eastern Transval who had suffered from Kaposi's sarcoma for a decade and in whom serum antibodies against HTLV-I were demonstrated. T-lymphocyte cell lines were established from his peripheral blood lymphocytes and shown to be productively infected with HTLV-I as evidenced by: the characteristic cell morphology; the typical morphogenesis on ultrathin section electron microscopy; the viral genome in DNA extracted from the cell lines; characteristic reverse transcriptase activity and viral specific proteins in the cell cultrue supernatant fluids. Spread of infection occurs through sexual intercourse, from mother to child, and by blood transfusion. Donated blood should be screened to contain the spread of HTLV-I infection.
- ItemNeutralization of HIV-1 subtypes: Implications for vaccine formulations(1998) Smith, T.L.; Van Rensburg, E. J.; Engelbrecht, S.More than 20.8 million people are infected with HIV in sub-Saharan Africa, with South Africa having one of the fastest growing HIV-1 epidemics, where an estimated 2.4 million people were infected. Thirty-two sera from 25 patients were tested for their ability to neutralize HTLV-III(B) (IIIB) and four primary isolates representing subtypes B, C, D, and a recombinant gag C/env B type. A CEM-SS cell line-based assay was used and the neutralizing titer was defined as the reciprocal of the highest dilution giving a 50% reduction in p24 antigen production. All isolates were neutralized better by subtype-specific sera, except for the C4714 strain, which was neutralized by both subtype B and C sera. C4714 was neutralized by 18/25 (72%) sera, IIIB by 19/32 (59%) sera, D482 by 7/31(23%) sera, B3245 by 6/29 (21%) sera, and the recombinant B/C1491 isolate by 4/25 (16%) sera. Five sera were unable to neutralize any of the isolates. The V3 region of the isolates used in the neutralization assay was amplified by PCR, directly sequenced, and analyzed to reveal variability between the consensus HIV-1 sequences and the isolates. HIV-1 strain C4714 was neutralized more effectively with the sera tested than the IIIIB laboratory strain. Variability in the amino acid sequence of the V3 region, which can alter the conformation of the V3 loop secondary structure, can influence the neutralization of a particular viral isolate. Vaccine formulations should be broadened to include multiple subtypes, especially C subtypes, which is rapidly spreading worldwide.