Nucleotide excision repair (NER) in Escherichia coli repairs DNA by incising the damaged strand o... more Nucleotide excision repair (NER) in Escherichia coli repairs DNA by incising the damaged strand on the 3′ and 5′ sides of the lesion within pyrimidine dimers and DNA cross-linking adducts. Cross-linking adducts belong to a class of chemical damage to DNA that prevent strand separation, and thus, replication and transcription. For this reason, cross-linking agents such as mitomycin C (MC) have been used in cancer chemotherapy. The mechanisms involved in MC binding to DNA have already been defined; however, the repair of these lesions is not fully understood. Our goal was to study the repair of MC DNA lesions in E. coli cells. Several bacterial strains with specific mutations were tested for cellular inactivation and kinetics of DNA repair through analysis of DNA sedimentation profiles in alkaline sucrose gradients. The results obtained show that uVrB mutants are extremely sensitive to MC in contrast to the other isogenic uVrA and uVrC mutant strains. uVrB mutant strains are unable to repair DNA strand breaks produced by MC. Thus, UvrB might play a NER-uncoupled role in the repair of lesions induced by MC in vivo, different from its role on the repair of lesions produced by UV-C. Also it is suggested that a modified NER system is taking place in the repair of MC-adducts.
The detection rate of Epstein-Barr virus (EBV) is higher in people living with human immunodefici... more The detection rate of Epstein-Barr virus (EBV) is higher in people living with human immunodeficiency virus (HIV). In an attempt to contribute to our epidemiological understanding of this coinfection and to investigate the activity of EBV in normal oral mucosa, we performed a cross-sectional study with HIV-positive patients. Oral smears from 145 HIV-positive patients were collected between March 2010 and March 2011. Nested polymerase chain reaction (PCR) and reverse transcriptase-PCR (RT-PCR) were used to genotype EBV and to detect EBNA-2 expression, respectively. EBV DNA was detected in 48.3% of the study participants, of whom 32.85% were EBV-1 and 45.71% were EBV-2 carriers. Additionally, 14.28% were coinfected with both types. EBNA-2 mRNA was expressed in 45.7% of the EBV -positive samples, including 20.0% with EBV-1 only, 20.0% with EBV-2 only and 1.4% with both genotypes. Immune status affected the overall EBV infection, and EBV-2 positivity was significantly correlated with sexual lifestyle of the participants. EBV co-infection with both viral types was dependent upon HIV viral load and the activity of the EBNA-2 gene. We report a high prevalence of active EBV in the oral mucosa of asymptomatic HIV-seropositive individuals. This study addresses the need for monitoring and treatment of HIV-infected patients with EBV reactivation.
Human papillomavirus type 53 (HPV 53), which belongs to genus Alpha, species A6, has spread among... more Human papillomavirus type 53 (HPV 53), which belongs to genus Alpha, species A6, has spread among women worldwide. Although it is classified as a probably high risk type, the association between HPV 53 and the development of neoplastic cervical disease is unclear, and HPV 53 is known to be genomically diverse. We investigated 15 cases of HPV 53 genital infection in women living in the state of Rio de Janeiro that were not associated with severe intraepithelial cervical neoplasia. To trace HPV 53 variants in this geographic area, we characterized the L1, E6 and E7 genes from these isolates, and undertook a phylogenetic analysis based on multiple alignment of their L1 sequences. After amplification and sequence analysis, we identified seven different L1-E6-E7 variants and a L1 co-infected isolate, which taken together had base pair changes at 29 different positions. The co-infected sample presented overlapped peaks at two positions. We also detected two new E6 genomic variants. Several base pair changes in the E6 region resulted in amino acid changes, three of which were non-conservative. The E7 gene was the most conserved sequence among those studied; in contrast, the E6 sequence reached a maximum difference of 2.79%. None of the HPV 53 isolates corresponded to the reference type. Dichotomical branching characteristic of HPV 53 was observed in all of the trees constructed, as well as in the concatenated phylogenetic tree. Probably, these variants pointing to evolutionary process, but they not appear to keep an increasing of pathogenesis Despite the limited number of samples analyzed in our work, we noticed that the same variant was found in more than one woman. Therefore, it is possible that such variants have been circulating in the female population in the state of Rio de Janeiro for a longer time or that due to host or genetic viral factors, these variants can spread more rapidly than others.
Background The aim of this study was to determine the prevalence and relationship of human papill... more Background The aim of this study was to determine the prevalence and relationship of human papillomavirus (HPV) genotypes in cervical samples from 140 human immunodeficiency virus (HIV)-seropositive women routinely attending an outpatient public gynecological service in the state of Rio de Janeiro, Brazil. Methods MY09/11 consensus primers were used to detect generic HPV DNA. HPV typification was performed by restriction fragment length polymorphism analysis following polymerase chain reaction amplification. Results The overall HPV prevalence was 60.0%. The identification of 24 different HPV genotypes including uncommon types was performed. A9 oncogenic genotypes were present in 54.02% of HIV-positive women. Abnormal cervical lesions, the time since HIV diagnosis and the number of sexual partners contributed independently to the high oncogenic HPV prevalence. The oncogenic and nononcogenic group were similarly affected by risk factors in contrast to negative HPV women. The frequency of multiple infections was 20%; furthermore, all of them presented at least one oncogenic type.
Nucleotide excision repair (NER) in Escherichia coli repairs DNA by incising the damaged strand o... more Nucleotide excision repair (NER) in Escherichia coli repairs DNA by incising the damaged strand on the 3′ and 5′ sides of the lesion within pyrimidine dimers and DNA cross-linking adducts. Cross-linking adducts belong to a class of chemical damage to DNA that prevent strand separation, and thus, replication and transcription. For this reason, cross-linking agents such as mitomycin C (MC) have been used in cancer chemotherapy. The mechanisms involved in MC binding to DNA have already been defined; however, the repair of these lesions is not fully understood. Our goal was to study the repair of MC DNA lesions in E. coli cells. Several bacterial strains with specific mutations were tested for cellular inactivation and kinetics of DNA repair through analysis of DNA sedimentation profiles in alkaline sucrose gradients. The results obtained show that uVrB mutants are extremely sensitive to MC in contrast to the other isogenic uVrA and uVrC mutant strains. uVrB mutant strains are unable to repair DNA strand breaks produced by MC. Thus, UvrB might play a NER-uncoupled role in the repair of lesions induced by MC in vivo, different from its role on the repair of lesions produced by UV-C. Also it is suggested that a modified NER system is taking place in the repair of MC-adducts.
The detection rate of Epstein-Barr virus (EBV) is higher in people living with human immunodefici... more The detection rate of Epstein-Barr virus (EBV) is higher in people living with human immunodeficiency virus (HIV). In an attempt to contribute to our epidemiological understanding of this coinfection and to investigate the activity of EBV in normal oral mucosa, we performed a cross-sectional study with HIV-positive patients. Oral smears from 145 HIV-positive patients were collected between March 2010 and March 2011. Nested polymerase chain reaction (PCR) and reverse transcriptase-PCR (RT-PCR) were used to genotype EBV and to detect EBNA-2 expression, respectively. EBV DNA was detected in 48.3% of the study participants, of whom 32.85% were EBV-1 and 45.71% were EBV-2 carriers. Additionally, 14.28% were coinfected with both types. EBNA-2 mRNA was expressed in 45.7% of the EBV -positive samples, including 20.0% with EBV-1 only, 20.0% with EBV-2 only and 1.4% with both genotypes. Immune status affected the overall EBV infection, and EBV-2 positivity was significantly correlated with sexual lifestyle of the participants. EBV co-infection with both viral types was dependent upon HIV viral load and the activity of the EBNA-2 gene. We report a high prevalence of active EBV in the oral mucosa of asymptomatic HIV-seropositive individuals. This study addresses the need for monitoring and treatment of HIV-infected patients with EBV reactivation.
Human papillomavirus type 53 (HPV 53), which belongs to genus Alpha, species A6, has spread among... more Human papillomavirus type 53 (HPV 53), which belongs to genus Alpha, species A6, has spread among women worldwide. Although it is classified as a probably high risk type, the association between HPV 53 and the development of neoplastic cervical disease is unclear, and HPV 53 is known to be genomically diverse. We investigated 15 cases of HPV 53 genital infection in women living in the state of Rio de Janeiro that were not associated with severe intraepithelial cervical neoplasia. To trace HPV 53 variants in this geographic area, we characterized the L1, E6 and E7 genes from these isolates, and undertook a phylogenetic analysis based on multiple alignment of their L1 sequences. After amplification and sequence analysis, we identified seven different L1-E6-E7 variants and a L1 co-infected isolate, which taken together had base pair changes at 29 different positions. The co-infected sample presented overlapped peaks at two positions. We also detected two new E6 genomic variants. Several base pair changes in the E6 region resulted in amino acid changes, three of which were non-conservative. The E7 gene was the most conserved sequence among those studied; in contrast, the E6 sequence reached a maximum difference of 2.79%. None of the HPV 53 isolates corresponded to the reference type. Dichotomical branching characteristic of HPV 53 was observed in all of the trees constructed, as well as in the concatenated phylogenetic tree. Probably, these variants pointing to evolutionary process, but they not appear to keep an increasing of pathogenesis Despite the limited number of samples analyzed in our work, we noticed that the same variant was found in more than one woman. Therefore, it is possible that such variants have been circulating in the female population in the state of Rio de Janeiro for a longer time or that due to host or genetic viral factors, these variants can spread more rapidly than others.
Background The aim of this study was to determine the prevalence and relationship of human papill... more Background The aim of this study was to determine the prevalence and relationship of human papillomavirus (HPV) genotypes in cervical samples from 140 human immunodeficiency virus (HIV)-seropositive women routinely attending an outpatient public gynecological service in the state of Rio de Janeiro, Brazil. Methods MY09/11 consensus primers were used to detect generic HPV DNA. HPV typification was performed by restriction fragment length polymorphism analysis following polymerase chain reaction amplification. Results The overall HPV prevalence was 60.0%. The identification of 24 different HPV genotypes including uncommon types was performed. A9 oncogenic genotypes were present in 54.02% of HIV-positive women. Abnormal cervical lesions, the time since HIV diagnosis and the number of sexual partners contributed independently to the high oncogenic HPV prevalence. The oncogenic and nononcogenic group were similarly affected by risk factors in contrast to negative HPV women. The frequency of multiple infections was 20%; furthermore, all of them presented at least one oncogenic type.
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Papers by Larissa Santos