V A Govan

University of Cape Town, Cape Town, Province of the Western Cape, South Africa

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Publications (9)19.99 Total impact

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    Vandana A Govan
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    ABSTRACT: Human papillomaviruses (HPVs) are one of the most common sexually transmitted infections and remains a public health problem worldwide. There is strong evidence that HPV causes cervical, vulva and vaginal cancers, genital warts and recurrent respiratory papillomatosis. The current treatments for HPV-induced infections are ineffective and recurrence is common-place. Therefore, to reduce the burden of HPV-induced infections, several studies have investigated the effi cacy of different prophylactic vaccines in clinical human trials directed against HPV types 6, 11, 16, or 18. Notably, these HPV types contribute to a signifi cant proportion of disease worldwide. This review will focus on the published results of Merck & Co's prophylactic quadrivalent recombinant vaccine targeting HPV types 6, 11, 16, and 18 (referred to as Gardasil((R))). Data from the Phase III trial demonstrated that Gardasil was 100% effi cacious in preventing precancerous lesions of the cervix, vulva, and vagina and effective against genital warts. Due to the success of these human clinical trials, the FDA approved the registration of Gardasil on the 8 June 2006. In addition, since Gardasil has been effi cacious for 5 years post vaccination, the longest evaluation of an HPV vaccine, it is expected to reduce the incidence of these type specifi c HPV-induced diseases in the future.
    Therapeutics and Clinical Risk Management 02/2008; 4(1):65-70.
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    ABSTRACT: There is overwhelming evidence that persistent infection with high-risk human papillomaviruses (HR-HPV) is the main risk factor for invasive cancer of the cervix. Due to this global public health burden, two prophylactic HPV L1 virus-like particles (VLP) vaccines have been developed. While these vaccines have demonstrated excellent type-specific prevention of infection by the homologous vaccine types (high and low risk HPV types), no data have been reported on the therapeutic effects in people already infected with the low-risk HPV type. In this study we explored whether regression of CRPV-induced papillomas could be achieved following immunisation of out-bred New Zealand White rabbits with CRPV VLPs. Rabbits immunised with CRPV VLPs had papillomas that were significantly smaller compared to the negative control rabbit group (P < or = 0.05). This data demonstrates the therapeutic potential of PV VLPs in a well-understood animal model with potential important implications for human therapeutic vaccination for low-risk HPVs.
    Virology Journal 01/2008; 5:45. · 2.09 Impact Factor
  • V A Govan, A-L Williamson
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    ABSTRACT: We previously demonstrated in a cottontail rabbit papillomavirus (CRPV) challenge model that recombinant Bacille Calmette-Guerin (rBCG) could potentially be used as a prophylactic vaccine vehicle to deliver papillomavirus proteins. In this study we investigated whether regression of CRPV-induced papillomas could be achieved following immunisation of out-bred New Zealand White rabbits with rBCG expressing CRPVL2, CRPVE2, CRPVE7 or CRPVL2E7E2 proteins. Rabbits immunised with rBCG/CRPVL2E7E2 had papillomas that were largely suppressed and were significantly smaller compared to the rBCG negative control group (P</=0.01). In addition, four of the six rabbits immunised with rBCG/CRPVL2E7E2 had papillomas that completely regressed 1.5 weeks post third immunisation. Rabbits immunised with rBCG/CRPVL2, rBCG/CRPVE7, or rBCG/CRPVE2 had papillomas that were significantly smaller than the negative control rabbits (P</=0.05). The findings in this study suggest that BCG could probably be used as a vaccine delivery vehicle for human papillomavirus proteins as a possible therapeutic vaccine.
    Virus Research 07/2007; 127(1):43-8. · 2.75 Impact Factor
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    ABSTRACT: Infection with high-risk human papillomavirus (HR-HPV) is a necessary but not a sufficient event in the development of cervical cancer, as most infections regress without intervention. Thus, genetic host factors and cellular immune responses could be potential modifiers for the risk of developing cervical cancer. In particular, p53 is considered as the most critical tumour suppressor gene and is involved in regulating cell division. The polymorphism on p53, which encodes either a proline or an arginine amino acid residue at codon 72, has been reported as a possible risk factor for cervical disease. This polymorphism has been shown to differentially affect the efficiency of degradation of p53 protein mediated by HR-HPV E6 oncoprotein. Women with histologically proven cancer of the cervix (n = 111) and hospital-based controls (n = 143) were included in this study. The patients and controls were from the Western Cape Province in South Africa. Genotyping of the p53 polymorphism was conducted using polymerase chain reaction and restriction fragment-length polymorphism method. The distributions of the allelic frequencies were stratified in both patients and controls into two South African ethnic population groups. In this study, we observed no association between the distribution of p53 polymorphism and susceptibility to cervical cancer in the Western Cape Province populations (P = 0.466). However, the frequency of the Pro/Pro residue at codon 72 was increased in the South African population when compared to Caucasians, Indians and Portuguese population groups. Notably, as the distribution of the Pro/Pro at codon 72 of p53 gene was significantly different (P < 0.05) between the control groups of South Africa and other population groups. This result suggests that ethnic disparity may influence the levels of p53 produced.
    International Journal of Immunogenetics 06/2007; 34(3):213-7. · 1.36 Impact Factor
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    ABSTRACT: The native cottontail rabbit papillomavirus (CRPV) L1 capsid protein gene was expressed transgenically via Agrobacterium tumefaciens transformation and transiently via a tobacco mosaic virus (TMV) vector in Nicotiana spp. L1 protein was detected in concentrated plant extracts at concentrations up to 1.0 mg/kg in transgenic plants and up to 0.4 mg/kg in TMV-infected plants. The protein did not detectably assemble into viruslike particles; however, immunoelectron microscopy showed presumptive pentamer aggregates, and extracted protein reacted with conformation-specific and neutralizing monoclonal antibodies. Rabbits were injected with concentrated protein extract with Freund's incomplete adjuvant. All sera reacted with baculovirus-produced CRPV L1; however, they did not detectably neutralize infectivity in an in vitro assay. Vaccinated rabbits were, however, protected against wart development on subsequent challenge with live virus. This is the first evidence that a plant-derived papillomavirus vaccine is protective in an animal model and is a proof of concept for human papillomavirus vaccines produced in plants.
    Clinical and Vaccine Immunology 09/2006; 13(8):845-53. · 2.60 Impact Factor
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    ABSTRACT: Recombinant Bacille Calmette-Guerin (rBCG) could potentially be the vaccine vehicle of choice to deliver foreign antigens from multiple pathogens. In this study we have used the cottontail rabbit papillomavirus (CRPV) rabbit model to provide a "proof of concept" that immunisation with rBCG expressing the CRPV major capsid protein, L1 (rBCG/CRPVL1), will protect outbred New Zealand White rabbits against CRPV challenge. Rabbits immunised with rBCG/CRPVL1 (10(7) cfu/ml) were protected 5 weeks post-CRPV challenge. Rabbits immunised with rBCG/CRPVL1 (10(5) cfu/ml) had papillomas, which were smaller and took longer to appear than the control rabbits. None of the negative control rabbits vaccinated with rBCG expressing an irrelevant gene or PBS were protected from CRPV challenge. Sera from rabbits immunised with rBCG/CRPVL1 (10(7) cfu/ml) were able to neutralise 54.5% of CRPV at serum dilutions of 1:200. These results provide evidence that BCG could potentially be used as a vaccine delivery vehicle for human papillomavirus proteins as a possible prophylactic vaccine.
    Vaccine 04/2006; 24(12):2087-93. · 3.49 Impact Factor
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    ABSTRACT: Cervical cancer is due to infection with specific high-risk types of human papillomavirus (HPV). Although the incidence of genital HPV infection in various population groups is high, most of these regress without intervention. Investigating genetic host factors and cellular immune responses, particularly cytokines, could help to understand the association between genital HPV infection and carcinogenesis. The tumor necrosis factor alpha (TNF-alpha) cytokine plays an important role in all stages of cervical cancer and has the ability to induce the regression of human tumors. Therefore the aim of the study was to investigate the allelic distribution of -308 TNF-alpha gene polymorphism in South African women with cervical cancer compared to control women. Included in our study were women with histologically proven cancer of the cervix (n = 244) and hospital-based controls (n = 228). All patients and controls were from mixed race and black population groups in South Africa. The detection of a bi-allelic -308 (A/G) polymorphism in the promoter region of TNF-alpha was investigated using the amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) technique. The distributions of the allelic frequencies were stratified in both patients and controls into two South African ethnic population groups. In this study we observed no association between the distribution of -308 TNF-alpha polymorphism and the risk of developing cervical cancer even after combining the data from the two ethnic populations (X2 = 2.26). In addition, using the chi-squared test we found no significant association between the known risk factors for cervical cancer and the allele distribution of -308 TNF-alpha. However, the frequency of the rare high-producing allele -308A of TNF-alpha was significantly lower in the South African population when compared to Caucasians and Chinese population groups. We demonstrated no association between -308 TNF-alpha polymorphism and the risk of cervical cancer among two South African ethnic population groups. However, as the distribution of the -308A TNF-alpha was notably different between the control groups of South Africa and other population groups this result suggests that ethnic disparity may influence the levels of TNF-alpha produced.
    BMC Cancer 02/2006; 6:24. · 3.33 Impact Factor
  • V A Govan
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    ABSTRACT: High-risk human papillomaviruses (HR-HPVs) are one of the most devastating oncogenic viruses worldwide and have been causally linked with the development of human cervical cancer. Several prophylactic and therapeutic clinical HPV vaccine trials are in progress. Although prophylactic vaccines are useful in preventing the incidence of cervical cancer, the elimination of existing HPV infections needs to be addressed, because cervical cancer is the leading female cancer in developing countries. Several different and encouraging strategies have been investigated in a preclinical and clinical setting for the treatment and elimination of existing HPV-induced infection. This review summarizes the therapeutic clinical trials and the different preclinical research strategies that are under investigation whereby HR-HPV E6 and E7 oncogenes are delivered in a nucleic acid form, in viral and bacterial vectors, or as peptide- and protein-based vaccines.
    Annals of the New York Academy of Sciences 12/2005; 1056:328-43. · 4.38 Impact Factor
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    ABSTRACT: BACKGROUND: The failure of specific types of human papillomaviruses (HPV) to raise effective immune responses may be important in the pathogenesis of cervical cancer, the second most common cancer in South African women. Polymorphisms of a number of cytokine genes have been implicated in inducing susceptibility or resistance to cancers caused by infectious agents owing to their role in determining host immune response. Polymorphisms of IL-10 and IFN-gamma genes are believed to influence the expression and/or secretion levels of their respective cytokines. METHODS AND RESULTS: In this study, women with histologically proven cancer of the cervix (n = 458) and hospital-based controls (n = 587) were investigated for bi-allelic -1082 (A/G) polymorphisms of IL-10 and the bi-allelic +874(A/T) polymorphisms of IFN-gamma. In addition, the distributions of the allelic frequencies were stratified in both the African and mixed race population groups of South Africa. We found striking differences in the allele distribution of IFN-gamma (X2 = 0.02) among the two ethnic groups. A significant increase in the allele distribution of the IFN-gamma AA genotype was found in the African group compared to the mixed population group (OR, 0.5; 95% CI, 0.2-1.0). For IL-10 there were no significant allelic differences between the two South African ethnic groups. Furthermore, when the ethnic groups were combined the IL-10 allelic frequencies in the combined South African data were similar to those observed in an Oriental population from Southern China and in an Italian population. However, the allele frequencies of the IFN-gamma genotype among the two South African ethnic groups were different when compared to an Italian Caucasoid group. While crude analysis of these data showed both statistically significantly increased and diminished risks of cervical cancer among high producers of INF-gamma and low producers of IL-10 respectively, these associations were no longer significant when the data were adjusted for confounding factors. CONCLUSION: These findings demonstrate a clear correlation between ethnicity and IFN-gamma polymorphism across different population groups. However, these differences in ethnicity and gene polymorphisms in the aforementioned cytokines are suggested not to influence the development of invasive cervical cancer but may represent an important susceptibility biomarker for other diseases and should be explored further.
    Journal of Carcinogenesis 06/2003; 2(1):3.