Estrelita Janse van Rensburg

An automated genotyping system for analysis of HIV-1 and other microbial sequences

MOTIVATION Genetic analysis of HIV-1 is important not only for vaccine development, but also to guide treatment strategies, track the emergence of new viral variants and ensure that diagnostic assays are contemporary and fully optimized. However, most genotyping methods are laborious and complex, and involve the use of multiple software applications. Here, we describe the development of an automated genotyping system that can be easily applied to HIV-1 and other rapidly evolving viral pathogens. RESULTS The new REGA subtyping tool, developed using Java programming and PERL scripts, combines phylogenetic analyses with boot-scanning methods for the genetic subtyping of full-length and subgenomic fragments of HIV-1. When used to investigate the subtype of previously published reference datasets that were analysed using manual phylogenetic methods, the automated method correctly identified 97.5-100% of non-recombinant and circulating recombinant forms of HIV-1, including 108 full-length, 108 gag and 221 env sequences downloaded from the Los Alamos database.

Rhinovirus Induction of the CXC Chemokine Epithelial-Neutrophil Activating Peptide-78 in Bronchial Epithelium

Epithelial-neutrophil activating peptide-78 (ENA-78) induces neutrophil migration, an early response to viral infection. Rhinovirus serotype 16 (RV16) was used to infect primary bronchial epithelial cells and a cell line (BEAS-2B). Release of ENA-78 protein was measured by enzyme-linked immunosorbent assay, ENA-78 mRNA production was quantified by reverse-transcription polymerase chain reaction, and ENA-78 promoter activity was assessed by use of a promoter construct. After infection with RV16, ENA-78 protein and mRNA increased significantly, and RV16 induced 3-fold increases in ENA-78 gene transcription. Nasal ENA-78 measured in patients with asthma with and without RV infection was more elevated in patients with RV infection present. Our study demonstrates that ENA-78 is produced in bronchial epithelial cells in response to RV16 infection. With other chemokines, it may be an important initiator of neutrophil airway inflammation during RV common colds and thus may play a role in the development of virus-associated airway pathologies.

Variability at Human Immunodeficiency Virus Type 1 Subtype C Protease Cleavage Sites : an indication of viral fitness

ABSTRACT Naturally occurring polymorphisms in the protease of human immunodeficiency virus type 1 (HIV-1) subtype C would be expected to lead to adaptive (compensatory) changes in protease cleavage sites. To test this hypothesis, we examined the prevalences and patterns of cleavage site polymorphisms in the Gag, Gag-Pol, and Nef cleavage sites of C compared to those in non-C subtypes. Codon-based maximum-likelihood methods were used to assess the natural selection and evolutionary history of individual cleavage sites. Seven cleavage sites (p17/p24, p24/p2, NC/p1, NC/TFP, PR/RT, RT/p66, and p66/IN) were well conserved over time and in all HIV-1 subtypes. One site (p1/p6gag) exhibited moderate variation, and four sites (p2/NC, TFP/p6pol, p6pol/PR, and Nef) were highly variable, both within and between subtypes. Three of the variable sites are known to be major determinants of polyprotein processing and virion production. P2/NC controls the rate and order of cleavage, p6gag is an important phosphoprotein required for virion release, and TFP/p6pol, a novel cleavage site in the transframe domain, influences the specificity of Gag-Pol processing and the activation of protease. Overall, 58.3% of the 12 HIV-1 cleavage sites were significantly more diverse in C than in B viruses. When analyzed as a single concatenated fragment of 360 bp, 96.0% of group M cleavage site sequences fell into subtype-specific phylogenetic clusters, suggesting that they coevolved with the virus. Natural variation at C cleavage sites may play an important role, not only in regulation of the viral cycle but also in disease progression and response to therapy.

Evaluation of Envelope Vaccines Derived from the South African Subtype C Human Immunodeficiency Virus Type 1 TV1 Strain

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) subtype C infections are on the rise in Sub-Saharan Africa and Asia. Therefore, there is a need to develop an HIV vaccine capable of eliciting broadly reactive immune responses against members of this subtype. We show here that modified HIV envelope (env) DNA vaccines derived from the South African subtype C TV1 strain are able to prime for humoral responses in rabbits and rhesus macaques. Priming rabbits with DNA plasmids encoding V2-deleted TV1 gp140 (gp140TV1ΔV2), followed by boosting with oligomeric protein (o-gp140TV1ΔV2) in MF59 adjuvant, elicited higher titers of env-binding and autologous neutralizing antibodies than priming with DNA vaccines encoding the full-length TV1 env (gp160) or the intact TV1 gp140. Immunization with V2-deleted subtype B SF162 env and V2-deleted TV1 env together using a multivalent vaccine approach induced high titers of oligomeric env-binding antibodies and autologous neutralizing antibodies against both the subtypes B and C vaccine strains, HIV-1 SF162 and TV1, respectively. Low-level neutralizing activity against the heterologous South African subtype C TV2 strain, as well as a small subset of viruses in a panel of 13 heterologous primary isolates, was observed in some rabbits immunized with the V2-deleted vaccines. Immunization of rhesus macaques with the V2-deleted TV1 DNA prime/protein boost also elicited high titers of env-binding antibodies and moderate titers of autologous TV1 neutralizing antibodies. The pilot-scale production of the various TV1 DNA vaccine constructs and env proteins described here should provide an initial platform upon which to improve the immunogenicity of these subtype C HIV envelope vaccines.

Risk for HIV-1 infection associated with a common CXCL12 (SDF1) polymorphism and CXCR4 variation in an African population.

CXC chemokine ligand 12 (CXCL12), or stromal cell-derived factor 1 (SDF1), is the only known natural ligand for the HIV-1 coreceptor, CXC chemokine receptor 4 (CXCR4). A single nucleotide polymorphism (SNP) in the CXCL12 gene (SDF1-3′A) has been associated with disease progression to AIDS in some studies, but not others. Mutations in the CXCR4 gene are generally rare and have not been implicated in HIV-1/AIDS pathogenesis. This study analyzed the SDF1-3′A SNP and performed mutation screening for polymorphic markers in the CXCR4 gene to determine the presence or absence of significant associations with susceptibility to HIV-1 infection. The study consisted of 257 HIV-1-seropositive patients and 113 HIV-1-seronegative controls representing a sub-Saharan African population belonging to the Xhosa ethnic group of South Africa. The SDF1-3′A SNP was associated with an increased risk for HIV-1 infection (P = 0.0319) whereas no significant association was observed between the occurrence of the SDF1-3′A SNP and increased or decreased plasma levels of CXCL12. Comprehensive mutation analysis of the CXCR4 gene confirmed a high degree of genetic conservation within the coding region of this ancient population.

Genetic Analysis of the Complete gag and env Genes of HIV Type 1 Subtype C Primary Isolates from South Africa

South Africa has one of the fastest growing HIV-1 epidemics, with an estimated 4.7 million people infected. To better understand the genetic diversity of this epidemic and its potential impact on vaccine development, we have cloned and sequenced the complete gag and env genes of 13 primary virus isolates. Phylogenetic analysis of our sequences and 69 complete env genes from the Los Alamos and GenBank databases revealed multiple subclusters within subtype C. The V3 loop region was relatively conserved in all our strains when compared with other subtypes, but the region immediately downstream was highly variable. No intersubtype recombinant forms were observed when comparing the gag and env sequences. Characterization of the complete gag and env genes enabled us to select specific strains for further vaccine development.

Phylogenetic diversity and low level antiretroviral resistance mutations in HIV type 1 treatment-naive patients from Cape Town, South Africa

We analyzed the HIV-1 pol gene from patients in Cape Town to determine the genetic diversity of HIV-1 in the region and to assess the baseline HIV-1 resistance level of treatment-naive patients. Plasma was collected prior to the national antiretroviral therapy (ART) program. RNA was extracted, followed by RT-PCR and automated DNA sequencing of the viral protease (PR) and reverse transcriptase (RT) coding region. Genotyping was done through phylogenetic analysis. The sequences were inspected for resistance-associated mutations against PR and RT inhibitors. A total of 140 pol sequences were analyzed, of which 133 (95%) belong to HIV-1 subtype C, five (3.6%) were subtype B, and one each was subtype G and CRF02_AG. Five sequences (3.6%) had resistance-associated mutations. These include three (2.1%) NNRTI mutations. With the progression of the national ART program, it is important to monitor the resistance profile of naive and treatment-experienced patients.

Human papilloma virus types in the oral and cervical mucosa of HIV‐positive South African women prior to antiretroviral therapy

BACKGROUND To evaluate the prevalence of human papilloma virus (HPV) infection and types in the oral and cervix mucosa of treatment-naïve HIV-1-positive women with CD4 counts less than 300 cells per ml with no HPV-associated oral lesions. METHODS Oral epithelium was harvested from the buccal mucosa and lateral borders of the tongue and cervical samples were collected from the endocervical area of 30 women, 22-64 years old. Cytobrush Plus cell collectors were used for sampling both anatomical areas. Genital pathology, obstetric and gynaecological history, co-morbid disease, hormone therapy, sexual behavior and smoking history were assessed via physical examination and clinical interviews. Special investigations included cervical Papanicolau smears, CD4 counts and HIV-1 viral loads. The linear array HPV test was used to determine HPV genotypes present in the specimens. RESULTS Oral HPV were identified in 20% (n = 6) of the patients, of which two had infection with two HPV types. Genital HPV was found in 96.7% (n = 29) of the women, of which only 14 had cytological abnormalities on Papanicolau smear. Infection with multiple HPV types were present in 93.1% (n = 27) of the patients, with an average of four HPV types per individual. CONCLUSIONS South African HIV-positive women with CD4 counts less than 300 cells per ml have a significant risk of cervical HPV strains and multiple strain infection of the cervix. The prevalence of HPV in normal oral mucosa was low but high-risk types were present. Limited correlation between oral HPV types and those identified in the cervical mucosa was found.

Characterization and phylogenetic analysis of South african HIV-1 subtype C accessory genes

To acquire new knowledge about the genetic diversity and potential impact on vaccine strategies of HIV-1 subtype C in South Africa, we have characterized the vif, vpr, and vpu genes of 15 isolates. Phylogenetic analysis of the genomic fragment encompassing these genes revealed subtype C subclusters, suggesting close relatedness with subtype C strains from other geographic locations and excluded isolation of South African strains. The putative T155 phosphorylation site in the C terminal of Vif was absent in all subtype C sequences. Variation in the predicted amino acid sequences of the three genes further showed strong correlation with other subtype C sequences.

Detection and subtyping of human herpesvirus-8 in renal transplant patients before and after remission of Kaposi's sarcoma

BACKGROUND Kaposis sarcoma (KS) is a complication of renal transplantation. If the human herpesvirus-8 (HHV-8) causes KS, the virus should be present in all KS lesions and be drastically reduced or cleared from involved tissue on remission of the KS. METHODS Fourteen renal transplant patients with cutaneous KS, including autopsy material from two cases, were investigated for the presence of HHV-8. A second skin biopsy was taken from 11 survivors, after remission of KS, from normal skin in the same anatomical region as the first biopsy. Remission was induced by reduction or cessation of immunosuppression. A peripheral blood sample was collected simultaneously with the repeat biopsy. A nested polymerase chain reaction assay was used to detect HHV-8 DNA in the biopsy tissue and peripheral blood mononuclear cells followed by direct sequencing of polymerase chain reaction product to detect any nucleotide changes. RESULTS HHV-8 DNA was detected in all the cutaneous KS and all the visceral KS samples, as well as a number of KS-free organs including the thyroid, salivary gland, and myocardium that have not been described before. Mutations in the viral DNA could be demonstrated in all patients. The mutations found were related more to that seen in AIDS-KS cases than that found in African endemic KS cases. HHV-8 sequences could be detected in follow-up frozen skin biopsies of five patients but were negative in the equivalent formalin-fixed specimens. Viral DNA was also detected in 2 of 11 peripheral blood mononuclear cell samples collected at the time of the follow-up skin biopsies. CONCLUSION Reduction or withdrawal of immunosuppression allows the immune system to recover sufficiently to reduce viral replication with subsequent viral persistence and low grade viral replication that coincides with clinical remission of the KS lesions. This provides further evidence for the important etiological role played by HHV-8 in the pathogenesis of posttransplant KS.