Cervical cancer is the second most common cancer among women worldwide and human papillomavirus (HPV) is a prerequisit for the development of this cancer. HPV belongs to the Papillomaviridae family and infects the basal layer of epithelial cells where it generally progresses into warts or condylomas. HPV can only reproduce in differentiating epithelia and it is therefore difficult to study the natural infection of HPV. More than 100 HPV types exist and they are divided into different genera based on their L1 open reading frame sequence. Most of the HPV types in the alpha-papillomavirus genus infect the mucosal epithelium while HPVs from the beta-papillomavirus genus usually infect cutaneous epithelial cells. Presently, it is not known what decides the anatomical tropism and our aim was to study determinants of this tropism. By using HPV virus like particles (VLP) and pseudovirus we found that VLPs from the two alpha-papillomaviruses HPV-6 and HPV-16 interacted with cell-surface heparan sulfate (HS) for initial attachment. When we labelled HPV VLPs with a fluorescent dye to study internalization HPV-6 was more strongly inhibited than HPV-16. Furthermore, a pseudovirus infection assay demonstrated that the beta-papillomavirus HPV-5 was less dependent on HS for infection than HPV-16. By analyzing the isoelectric point (p1) of the HPV L1 capsid protein we found that alpha HPV types were more positively charged than beta HPV types. Also, HPV-6 had a higher positive charge than HPV-16. Thus, the inhibition of the negatively charged heparin against HPV infection was clearly related to the charge of the HPV L1 capsid. This suggested that the initial interaction could be one of the determinants of tropism although not the sole factor. Lactoferrin is a protein found in milk, saliva, semen, tear fluid and endocervical secretions that has antiviral activities. Both human and bovine lactoferrin inhibited HPV infection but we found no significant differences in inhibition of alpha- and beta-papillomavirus infection. We could however demonstrate that different lactoferricins, small peptide derivates from the N-terminal part of lactoferrin, were able to inhibit HPV infection. This antiviral activity depended on lactoferricin peptide, HPV type and cell origin. The regulation of HPV gene expression in the host cell could also determine HPV tropism. The HPV long control region (LCR) contains cis-responsive elements that regulate HPV transcription and the epithelial tropism of HPV is determined by epithelial specific constitutive enhancers in the LCR. It has been hypothesized that the combination of transcription factors in the host cell determines the cell-type-specific expression. In cells with a skin origin the HPV-5 LCR was twice as efficient in transcriptional activation compared to HPV-16 LCR, while in cervical cells the HPV-16 LCR was almost twice as effective in activating transcription compared to HPV-5 LCR. To conclude, alpha- and beta-papillomaviruses differed regarding their ability to infect cells and regulate viral gene expression. These abilities corresponded with their natural host cells and suggested that HPV anatomical tropism could be determined at several steps in the HPV life cycle.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-06-28T18:01:45Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) AnaPavla_Tese.pdf: 2030041 bytes, checksum: d62d754a4e28b637ecec9ecbd30a1fb2 (MD5) / Made available in DSpace on 2016-06-28T18:01:45Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) AnaPavla_Tese.pdf: 2030041 bytes, checksum: d62d754a4e28b637ecec9ecbd30a1fb2 (MD5) Previous issue date: 2015-02-25 / CAPES / Cerca de 265 mil mulheres morrem todos os anos vítimas de câncer cervical. Infecções persistentes causadas por Papilomavírus humano de alto risco oncogênico (HR HPVs) é uma condição necessária, porém não suficiente para o desenvolvimento de lesões cervicais e câncer cervical. Dessa forma, diversos fatores ambientais e genéticos estão envolvidos na carcinogênese cervical. Dentre os fatores genéticos, as variantes genéticas dos HR HPVs parecem estar relacionados com o risco de infecções persistentes e desenvolvimento de lesões e câncer cervical. Assim, o presente estudo investigou: 1) A variabilidade genética de um fragmento do gene L1 dos HPV16, 31, 53, 54, 56, 58, 61, 62, 66, 70 e 81 em amostras biológicas de pacientes oriundos dos Estados de Pernambuco, Alagoas e Sergipe, Nordeste do Brasil; 2) A variabilidade genética da LCR dos HR HPVs 16, 31 e 58 oriundas de pacientes dos Estados de Pernambuco, Alagoas e Sergipe, Nordeste do Brasil; 3) Uma possível associação entre os polimorfismos virais do gene L1 e o risco para desenvolver lesões cervicais nas pacientes do Nordeste do Brasil. Para tanto, a detecção do DNA viral foi realizada em amostras biológicas de 784 pacientes. Os fragmentos parciais do gene L1 e da LCR dos HPVs mencionados foram sequenciados. Análises in silico de possíveis epitopos de células B e de células T foram efetuadas nas regiões de mutação não-sinônima no gene L1. Além disso, análises in silico dos sítios de ligação dos fatores transcricionais foram realizadas em regiões de alteração nucleotídica da LCR. Foram detectados 23 tipos de HPVs: HPVs 6, 11, 16, 18, 31, 33, 35, 39, 45, 52, 53, 54, 56, 58, 61, 62, 66, 70, 72, 81, 82, 83 e 84. Com relação ao gene L1 dos HPV analisados, foram detectadas 98 mutações, sendo 96/98 substituições de bases, 1/98 deleção e 1/98 inserção de nucleotídeo. Dentre estas alterações nucleotídicas no gene L1, 29,6% são mutações não sinônimas. Ademais, 18,36% das variações detectadas no gene L1 estavam inseridas em epitopos de células B, 25,5% inseridos em regiões de MHC Classe I e 18,36% inseridos em regiões de MHC Classe II. Um total de 8,1% das variações genéticas observadas no gene L1 dos HPV estudados foram descritos pela primeira vez na literatura. Em relação a LCR, foram detectadas 95 mutações, sendo 88/95 substituições de bases, 5/98 deleções e 2/95 inserções de nucleotídeos. Um total de 51,5% das mutações detectadas estão inseridas em sítios de ligação dos fatores transcricional celular e/ou viral. Além disso, 3,1% das variações genéticas encontradas na LCR foram descritas pela primeira vez na literatura. As análises filogenéticas mostraram a presença das variantes A e D do HPV16, A e C do HPV31 e A, B, C e D do HPV58 circulante no Nordeste do Brasil. Com relação a repercussão biológica das mutações do gene L1 do HPV16, não foram observadas associações significativas (p>0.05) entre os polimorfismos do gene L1 e o risco para desenvolver lesões cervicais. Entretanto, a combinação de determinados alelos destes polimorfismos virais está fortemente associada com o risco de desenvolver lesão cervical. Assim, a detecção das principais variantes e de alterações nucleotídicas com potencial impacto biológico circulantes no Nordeste Brasileiro é importante face as diferenças na patogenicidade dos HPVs. / Approximately 265 thousand women die every year from cervical cancer. Persistent infections caused by high oncogenic risk Human papillomavirus (HR HPV) are necessary but not sufficient condition for the development of cervical lesions and cervical cancer. Therefore, several environmental and genetic factors are involved in cervical carcinogenesis. Concerning the genetic factors, variants of HR HPV seem to be related to the risk of persistent infections and the development of lesions and cervical cancer. In this sense, the present study aimed to investigate: 1) The genetic variability of a L1 gene fragment from HPV16, 31, 53, 54, 56, 58, 61, 62, 66, 70 and 81 in biological samples of patients from Pernambuco, Alagoas and Sergipe states, Northeastern Brazil; 2) The genetic variability of the LCR of HR HPVs 16, 31 and 58 of patients from from Pernambuco, Alagoas and Sergipe states, Northeastern Brazil; 3) Possible association between the viral polymorphisms of the L1 gene and the risk to develop cervical lesions in patients from the Brazilian Northeast. To achieve that, viral DNA detection was performed in biological samples from 784 patients. Partial fragments of the L1 gene and the LCR of the abovementioned HPVs were sequenced. In silico predictions of possible B cells and T cells epitopes were performed in regions of non-synonymous mutation of the L1 gene. Moreover, in silico predictions of the binding sites of transcriptional factors were performed in nucleotide change regions within LCR. Twenty-three HPV types were detected: HPVs 6, 11, 16, 18, 31, 33, 35, 39, 45, 52, 53, 54, 56, 58, 61, 62, 66, 70, 72, 81, 82, 83 e 84. Regarding the L1 gene from the analyzed HPVs, 98 mutations were detected, in which 96 are nucleotide substitutions, 1 is deletion and 1 is nucleotide insertion. Among these nucleotide changes in the L1 gene, 29.6% are non-synonymous mutations. Moreover, 18.36% of the nucleotide changes are located in B cell epitopes, 25.5% located in MHC Class I regions and 18.36% located in MHC Class II regions. Finally, 8.1% of the genetic variations in the L1 gene of the studied HPVs were observed for the first time. Concerning LCR, 95 mutations were detected, in which 88 are nucleotide substitutions, 5 are deletions and 2 are nucleotide insertions. A total of 51.5% of the detected mutations are located in binding sites of cellular and/or viral transcriptional factors. Additionally, 3.1% of the genetic variations found in LCR were described for the first time. Phylogenetic analisys showed the presence of A and D variants of the HPV16, A and C variants of the HPV31, and A, B, C and D variants of the HPV58 circulating in the Brazilian Northeast. In regard to the biological repercussion of the L1 gene mutations of the HPV16, no significant associations were observed (p>0.05) between L1 gene polymorphism and the risk to develop cervical lesions. However, the combination of certain alleles from these viral polymorphisms is firmly associated to the risk to develop cervical lesion. Thus, the detection of the main circulating variants with potential biological impact in the Brazilian Northeast is important in view of the differences in the pathogenicity of the HPV.