Silvia C. Galvan

Asian-american variants of human papillomavirus type 16 have extensive mutations in the E2 gene and are highly amplified in cervical carcinomas

Human‐papillomavirus (HPV)‐E2 protein is involved in gene‐expression regulation and replication of HPV genome. Disruption of the E2 gene during viral integration has been proposed as a mechanism of tumoral progression, since the expression of E6/E7 viral oncogenes is allowed. However, retention of E1/E2 genes and high viral amplification are frequently found in HPV16‐positive carcinomas of some populations. In this study, we investigated whether retention of E1/E2 and viral amplification are associated with particular HPV16 E2 variants in cervical carcinomas. HPV16 detection, E1/E2 integrity and viral amplification were explored by Southern blot in 123 cervical carcinomas. HPV16 variants were identified by Southern blot and by sequencing E6, L1/MY and E2 regions. Of 46 HPV16‐positive tumors, 34 were positive for E1/E2 and 14 of them showed a variant restriction pattern by mutations in E2. All 14 were Asian‐American (AA) variants and, of 11 sub‐classified, 6 were AA‐a and 5 AA‐c. Two E1/E2‐negative tumors also contained the AA‐c variant, while the remaining HPV16‐positive tumors contained only European variants. The E2 gene of AA variants showed 24 mutations, 19 identical in both sub‐classes. The 24 mutations were distributed throughout the entire gene and 19 result in 18 amino‐acid changes. The AA variants were associated with E1/E2‐positive carcinomas with more than 50 viral copies/cell (p = 0.035). The association of Asian‐American E2 variants with retention of E1/E2 suggests that E2 variation may be an alternative mechanism de‐regulating the expression of viral oncogenes. Int. J. Cancer 83:449–455, 1999.

Multiple human papillomavirus infections are highly prevalent in the anal canal of human immunodeficiency virus-positive men who have sex with men

BackgroundAnal cancer has become one of the most common non-AIDS-defined tumors among Human Immunodeficiency Virus-positive (HIV+) individuals, and a rise in its incidence among HIV+ Men who have Sex with Men (MSM) has been shown, despite the introduction of Highly Active Anti-Retroviral Therapy (HAART). Human Papillomavirus (HPV) infections are highly prevalent among HIV+ MSM and recent studies have shown high rates of HPV-associated anal intraepithelial neoplasia (AIN) and anal cancer among this population.MethodsIn the present study we determined the prevalence and nature of HPV co-infections in the anal canal of 324 HIV+ MSM attending a high specialty medical center in Mexico City, DNA extraction and amplification with generic primers for HPV was performed, followed by detection of specific types and co-infections with INNO-Lipa, and identification of variants by amplification and sequencing of the E6 and LCR region of HPV 16.ResultsWe found a very high prevalence of HPV infections among this cohort (86%), with more than one fourth of them (28%) positive for type 16. Among HPV16-positive patients, European variants were the most prevalent, followed by Asian-American ones. Among these individuals (HPV-16+), we identified co-infections with other 21 HPV types namely; 11, 51, 52, 6, 66, 68, 74, 18, 45, 35, 26, 44, 70, 53, 54, 82, 31, 33, 56, 58, 59.ConclusionsHIV+ MSM show a very high rate of HPV infections in the anal canal and those with type 16 exhibited a multiplicity of associated types. This study emphasizes the need for an early detection of HPV infections among HIV+ MSM in order to establish its utility to prevent anal neoplasia and cancer.

Stagewise decline in the activity of brain protein synthesis factors and relationship between this decline and longevity in two rodent species.

The activities of brain initiation factor 2 and brain elongation factor 1, which function as rate-limiting in total protein synthesis, and estimations of brain weight were followed during postnatal life in the rat and the mouse. Both activities decreased in parallel while cumulative brain weight increased. Three exponential components were required for the mathematical expression of each of the three processes in semilogarithmic plots against time. The acceleration curves for the activities and tissue weight demonstrated a mirror image symmetry. Within the general pattern of diminution with age, the negative acceleration of the activities and the positive acceleration of the brain weight displayed repeated bursts. The activities of both factors could also be arranged into several regression lines in log/log plots against time. Significantly, in these plots, the regression line calculated for the whole set of data for each factor activity showed that the value of the ratio of the slopes (mouse to rat) was inversely related to the square root of the ratio of species longevity and was in agreement with the power law relating life spans of cells to species longevity (Röhme, Proc. Natl. Acad. Sci. U.S.A., 78 (1981) 5009).

Analysis of CpG methylation sites and CGI among human papillomavirus DNA genomes

BackgroundThe Human Papillomavirus (HPV) genome is divided into early and late coding sequences, including 8 open reading frames (ORFs) and a regulatory region (LCR). Viral gene expression may be regulated through epigenetic mechanisms, including cytosine methylation at CpG dinucleotides. We have analyzed the distribution of CpG sites and CpG islands/clusters (CGI) among 92 different HPV genomes grouped in function of their preferential tropism: cutaneous or mucosal. We calculated the proportion of CpG sites (PCS) for each ORF and calculated the expected CpG values for each viral type.ResultsCpGs are underrepresented in viral genomes. We found a positive correlation between CpG observed and expected values, with mucosal high-risk (HR) virus types showing the smallest O/E ratios. The ranges of the PCS were similar for most genomic regions except E4, where the majority of CpGs are found within islands/clusters. At least one CGI belongs to each E2/E4 region. We found positive correlations between PCS for each viral ORF when compared with the others, except for the LCR against four ORFs and E6 against three other ORFs. The distribution of CpG islands/clusters among HPV groups is heterogeneous and mucosal HR-HPV types exhibit both lower number and shorter island sizes compared to cutaneous and mucosal Low-risk (LR) HPVs (all of them significantly different).ConclusionsThere is a difference between viral and cellular CpG underrepresentation. There are significant correlations between complete genome PCS and a lack of correlations between several genomic region pairs, especially those involving LCR and E6. L2 and L1 ORF behavior is opposite to that of oncogenes E6 and E7. The first pair possesses relatively low numbers of CpG sites clustered in CGIs while the oncogenes possess a relatively high number of CpG sites not associated to CGIs. In all HPVs, E2/E4 is the only region with at least one CGI and shows a higher content of CpG sites in every HPV type with an identified E4. The mucosal HR-HPVs show either the shortest CGI size, followed by the mucosal LR-HPVs and lastly by the cutaneous viral subgroup, and a trend to the lowest CGI number, followed by the cutaneous viral subgroup and lastly by the mucosal LR-HPVs.

Phenetic variation in Trypanosoma (schizotrypanum) cruzi isolates

Abstract 1. 1. Thirteen isoenzyme loci were analyzed electrophoretically for each of 13 isolates obtained from Argentina. Costa Rica, Mexico and Venezuela to determine both genetic distance and time of evolutionary divergence between these populations. 2. 2. The isolates from Costa Rica, Mexico and Venezuela appeared as a very homogeneous group and differed from those from Argentina. 3. 3. The tentative values for polymorphism, heterozygosity and number of alleles per locus were higher for the isolates from Argentina than the corresponding values for the other isolates.

Vaccines against human papillomavirus: perspectives for controlling cervical cancer

Prophylactic vaccines against human papillomavirus (HPV) are on the market and will certainly reduce the incidence of genital warts and the risk of developing cervical cancer. In addition, they will contribute to reducing anal as well as head and neck cancers. However, effort should be made in the short term in order for these vaccines to have a real impact in the developing world, where almost 80% of cervical cancer cases occur. Since the available vaccines include only two of the HPV types found in cancers (approximately 70%), improvements in current mass screening programs – with the use of molecular techniques – must be made, particularly in developing countries. Therapeutic vaccines have been designed to control advanced lesions and residual illness and, although success has usually been obtained in animal models, clinical studies have not yet provided the anticipated results. Finally, the next generations of prophylactic HPV vaccines will probably include subunit vaccines, transgenic bacteria and plants, among others, and could represent useful and cheaper alternatives for reducing cervical cancer, particularly in the developing world.

Epigenetics and animal virus infections

Epigenetics, modifications of the genome, heritable during celldivision, that do not involve changes in DNA sequences includeseveral mechanisms mainly: histone modifications, DNA methy-lation and related modifications, non-coding RNAs (ncRNAs)and others that regulate gene expression.The past two decades has seen an explosion of interestfor revealing mechanisms that control epigenetic modifications,mainly based on the influence they have on chromatin struc-tureandtheirimpactinbiologicalprocessessuchasprogrammedDNA rearrangements, imprinting, germ line silencing, devel-opmentally cued stem cell division, and overall chromosomalstability and identity. It has also become obvious that epigenet-ics changes are fundamental in the interplay between viruses andtheir host cells. Generally speaking, when retroviruses and DNAviruses integrate their genomes into the host genome, they canstay latent by silencing their genes or can be productive by acti-vatingthem,andviralgeneexpressioncanberegulatedjustlikeasthe host. In fact, viral DNA uses host transcription factors as wellas epigenetic regulators, in such a way that the effect of viral epi-geneticcontrolofitsowngeneexpressionalsoextendstoregulatehost gene expression. At the same time cells use similar mech-anisms, transcription factors and epigenetic modifications, inorder to try to eliminate viral infections. In summary, epigeneticmechanisms are involved in most of the virus-cell interactions.The goal of this special issue is to bring together key exper-imental and theoretical research linking state-of-the-art knowl-edge of epigenetic mechanisms involved in regulating virus-cellinteractions.This e-book is a compilation of 12 articles. Two of them aremethodological, one on the use of new technologies devoted toidentify methylated CpG sites on virus genomes and the other ongenome-wide mapping of DNase I hypersenitive sites associatedwith gene expression. Three articles describe original researchinvolvingSV40minichromosomes,DNAmethylationfluctuationand the Toll-like receptor pathways. Seven are review articles,including two mini-reviews on Epigenetic Mechanisms associ-ated to Hepatitis B Virus (HBV) and fundamental topics as DNAmethylation,histonemodificationsandviralstrategiesagainstthehost immune system in Epstein B Virus; cell differentiation ofthe immune system as a tool for epigenetic studies; epigeneticmechanisms associated to virotherapy, and finally on the recog-nition of DNA viruses and cell damage by histones.ThearticlefromSunetal.(2014),isamethodologyarticledes-ignatingtherelativeadvantagesoftheNGStechnologycomparedto pyrosequencing for studying viral DNA methylation. The ana-lytical procedure they used provided further information relatedto HPV methylation on a single cell basis, showing that there areHPV 16 genomic sequences in cells which are mostly methylatedwhile in others they are unmethylated (methylation mosaic).Replication of SV40minichromosomes can serve as an epige-netic switch in which newly replicated chromatin can be epige-neticallymodifiedinresponsetospecificsignalssuchasT-antigenbindingtositeI.Thisepigeneticswitchseemstoensurethatnewlyreplicated minichromosomes do not activate early transcriptionat late times in infection. In addition, this epigenetic switch maycontrol the relative pool sizes of transcribing, replicating, andencapsidating SV40minichromosomes. In an original researcharticle, Kallestad et al. (2013), shows that in cells containingSV40minichromosomes, histone modifications associated withchromatin repression can differ significantly depending uponwhether the chromatin is being repressed, undergoes transcrip-tion or replication.The review from Russ et al. (2013), describes advantages ofstudying the immune system for epigenetic regulation of celldifferentiation, in particular how T cell identity or plasticity iscontrolled. The authors focus some of the key findings and gen-eral themes emerging from the studies of T cell differentiation,as well as the utility of the immune system as a tool for studyingdifferentiation and development.Histonesareessentialcomponentsofchromatinstructure,andhistone modification plays an important role in various cellularfunctions including transcription, gene silencing, and immunity.Inaddition,histonesalsoplaydistinctrolesinextrachromosomalsettings. Kobiyama et al. (2013), in their review describe the roleof histone H2B as a sensor for dsDNA aberrantly present withinthe cells. According to the results included, extracellular andextrachromosomal histones alert cells to dangerous situations,such as infection, apoptosis, DNA breaks, and cell injury.Hepatitis B virus (HBV) infection is a global health problemcausing a wide spectrum of liver diseases, including acute andchronicinfection.AcuteHBVinfectionseitherresolveorprogressto chronic hepatitis, cirrhosis, and hepatocellular carcinoma.Because for most patients, available therapies do not lead tothe termination of HBV infection, improving our understanding