Seroprevalence of Trypanosoma cruzi in Eight Blood Banks in Mexico.

BACKGROUND: The true prevalence of Chagas disease in Mexico is unknown. However, it has been estimated that 1.1-4 million people are infected with Trypanosoma cruzi, which represents a potential risk for transmission of the disease via contaminated blood. AIM OF THE STUDY: To determine the Chagas disease seroprevalence in donors from eight blood banks in the north of Mexico City, and the northeast of the State of Mexico. STUDY DESIGN AND METHODS: Serum samples from blood donors (n = 515,038) were tested to detect the presence of anti-Trypanosoma cruzi antibodies in eight blood banks. The serologic screening test was performed in each of the blood banks. To confirm the seropositive blood donors, only two out of the eight blood banks used a test with a different principle with the aim of identifying anti-Trypanosoma cruzi antibodies. All tests were validated by the Mexican Institute for Epidemiological Diagnosis and Reference. RESULTS: One thousand two hundred and ten blood donors were seropositive for Trypanosoma cruzi, which represents a 0.23% seroprevalence (95% CI 0.22-0.25%). Of the seropositive blood donors, 97.03 % resided in the northeast area of the State of Mexico, Mexico City, and southern part of the State of Hidalgo. CONCLUSIONS: Active transmission of Chagas disease may be occurring in non-endemic regions in the northeast of the State of Mexico.

High prevalence of human papillomavirus type 66 in low-grade cervical lesions of Mexican women.

Our aim was to analyze the prevalence of high-risk human papillomavirus (HR-HPV) and its association with risk factors related to cervical lesions. We used 362 cervical samples from a transversal study to detect nineteen types from the high-risk HPV clade by highly sensitive PCR. Unexpectedly, we found a very high prevalence of HPV type 66 (32.8%), particularly in low-grade squamous intraepithelial lesions. A significant association of HPV66 with previously sexually transmitted disease was observed (p < 0.05). Our results strongly suggest that HPV66 might be indicative of cervical lesions that will not progress to cancer. HPV genotyping by methods that grouped type 66 with other HR-HPV clade types should be interpreted with caution.

Prevalence of oncogenic human papillomavirus in patients with cervical lesion. / Prevalencia del virus del papiloma humano oncogénico en pacientes con lesión cervical.

BACKGROUND: High risk human papillomavirus (hrHPV) infection is associated with the development of cervical cancer (CC) in 99.7%. The prevalence of HPV varies according to the geographic region, lesion degree, method of detection, among other variables. OBJECTIVE: To determine the prevalence of hrHPV and identify some risk factors in a group of women with cervical lesions from Mexico City. MATERIAL AND METHODS: Of 421 women, 310 were included. Questionnaires of risk factors were administered, and cervical samples which included the entire spectrum of cervical lesions according to the Bethesda system were obtained. HPV genotyping was made with INNO-LiPA system. Population characteristics were analyzed with descriptive statistics. Risk factors' odds ratio (OR) was calculated with chi squared using SPSS software, version 24.0. RESULTS: 91.6% of the samples were positive for hrHPV. The prevalent types were 16, 66, 52 and 51. By age group there were not statistically significant differences in the risk of HPV infection. Having had three or more sexual partners increased the risk of infection by hrHPV (OR: 2.99; 95% confidence interval [95% CI]: 1.247.24). Sexually transmitted diseases increased the probability of infection by hrHPV different to types 16, and 18 (OR: 2.47; 95% CI, 1.24-7.24 and 1.50-4.06). CONCLUSIONS: The high prevalence of types 66, 52 and 51 is a finding that has not been described previously in our population. We hope that this study will help to improve health services in order to decrease the incidence of cervical ­cancer.

INTRODUCCIÓN: La infección por el virus del papiloma humano (VPH) de alto riesgo oncogénico (VPHar) se asocia al cáncer cervicouterino en el 99.7% de los casos. La prevalencia de VPH varía según la región geográfica, el grado de lesión y el método de detección, entre otras variables. OBJETIVO: Determinar la prevalencia de VPHar e identificar factores de riesgo en mujeres con lesión cervical de la Ciudad de Mexico. MATERIAL Y MÉTODOS: De 421 mujeres, se incluyeron 310. Se aplicaron cuestionarios y se obtuvieron muestras que incluyeron todo el espectro de las lesiones cervicales según el sistema Bethesda. La tipificación del VPH se hizo mediante el sistema INNO-LiPA. Las características de la población se analizaron con estadística descriptiva. Con la prueba de chi cuadrada se calculó la razón de momios (RM) de los factores de riesgo con el programa SPSS, versión 24.0. RESULTADOS: El 91.6% de las muestras fueron positivas para VPHar. Los VPH prevalentes fueron los tipos 16, 66, 52 y 51. Por edad no hubo significación estadística para riesgo de infección por VPHar. Haber tenido tres o más parejas sexuales elevó el riesgo de infección por HPVar (RM: 2.99; intervalo de confianza del 95 [IC 95%]: 1.247.24). Las infecciones de transmisión sexual favorecieron el riesgo de infección por otros VPHar distintos de los tipos 16 y 18 (RM: 2.47; IC 95%: 1.24-7.24 y 1.50-4.06). CONCLUSIÓN: La elevada prevalencia de VPH 66, 52 y 51 es un hallazgo que no ha sido descrito previamente en nuestra población. Esperamos que este estudio contribuya a mejorar los programas de los servicios de salud dirigidos a disminuir la incidencia de cáncer cervicouterino.

Biochemical and proteomic analysis of spliceosome factors interacting with intron-1 of human papillomavirus type-16.

The human papillomavirus type 16 (HPV-16) E6/E7 spliced transcripts are heterogeneously expressed in cervical carcinoma. The heterogeneity of the E6/E7 splicing profile might be in part due to the intrinsic variation of splicing factors in tumor cells. However, the splicing factors that bind the E6/E7 intron 1 (In-1) have not been defined. Therefore, we aimed to identify these factors; we used HeLa nuclear extracts (NE) for in vitro spliceosome assembly. The proteins were allowed to bind to an RNA/DNA hybrid formed by the In-1 transcript and a 5'-biotinylated DNA oligonucleotide complementary to the upstream exon sequence, which prevented interference in protein binding to the intron. The hybrid probes bound with the nuclear proteins were coupled to streptavidin magnetic beads for chromatography affinity purification. Proteins were eluted and identified by mass spectrometry (MS). Approximately 170 proteins were identified by MS, 80% of which were RNA binding proteins, including canonical spliceosome core components, helicases and regulatory splicing factors. The canonical factors were identified as components of the spliceosomal B-complex. Although 35-40 of the identified factors were cognate splicing factors or helicases, they have not been previously detected in spliceosome complexes that were assembled using in vivo or in vitro models.

A few nucleotide polymorphisms are sufficient to recruit nuclear factors differentially to the intron 1 of HPV-16 intratypic variants.

The HPV-16 E6/E7 genes, which contain intron 1, are processed by alternative splicing and its transcripts are detected with a heterogeneous profile in tumours cells. Frequently, the HPV-16 positive carcinoma cells bear viral variants that contain single nucleotide polymorphisms into its DNA sequence. We were interested in analysing the contribution of this polymorphism to the heterogeneity in the pattern of the E6/E7 spliced transcripts. Using the E6/E7 sequences from three closely related HPV-16 variants, we have shown that a few nucleotide changes are sufficient to produce heterogeneity in the splicing profile. Furthermore, using mutants that contained a single SNP, we also showed that one nucleotide change was sufficient to reproduce the heterogeneous splicing profile. Additionally, a difference of two or three SNPs among these viral sequences was sufficient to recruit differentially several splicing factors to the polymorphic E6/E7 transcripts. Moreover, only one SNP was sufficient to alter the binding site of at least one splicing factor, changing the ability of splicing factors to bind the transcript. Finally, the factors that were differentially bound to the short form of intron 1 of one of these E6/E7 variants were identified as TIA1 and/or TIAR and U1-70k, while U2AF65, U5-52k and PTB were preferentially bound to the transcript of the other variants.

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

BACKGROUND: The 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. RESULTS: CpGs 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). CONCLUSIONS: There 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.

The HPV-16 E7 oncoprotein is expressed mainly from the unspliced E6/E7 transcript in cervical carcinoma C33-A cells.

The HPV-16 E6/E7 early transcripts are first produced as bicistronic or polycistronic mRNAs, and about 90% of the original pre-mRNA is spliced to produce three new alternative mRNAs. HPV-16 spliced transcripts are expressed heterogeneously in tumors and cell lines. Our results suggest that suboptimal splicing acceptor sites in E6/E7 intron 1 and the differential expression of splicing factors are involved in the production of the heterogeneous splicing profile in cell lines. The unspliced pre-mRNA and the alternative spliced transcripts contribute differentially to the production of E7 in stably transfected C33-A cells. The highest level of E7 was produced from the least prevalent transcript, the unspliced E6/E7(pre-mRNA). The order of relative expression of E7 was unspliced E6/E7(pre-mRNA) > E6*I/E7 > E6*II/E7. Our findings suggest that E6/E7 alternative splicing may be a mechanism for differential expression of the E6 and E7 oncoproteins, which also affects the expression of their targets, the proteins p53 and pRb.

The intron 1 of HPV 16 has a suboptimal branch point at a guanosine.

The branch point sequence (BPS) of intron 1 of the HPV-16 was determined via RT-PCR in a cell free system, using lariat intermediates obtained by in vitro splicing reactions. We used synthetic E6/E7 transcripts and HeLa nuclear protein extracts to obtain the splicing intermediates. Then, a divergent oligonucleotide primer set, pairing on the lariat RNA that encompassed the 2'-5' phosphodiester bond formed between the 5' end of the intron and the BPS, was used for cDNA synthesis and PCR amplification. Subsequent RT-PCR assays revealed four splicing intermediates, made up of a major intermediary corresponding to the BPS and four cryptic branched sequences. Only intermediates bound at the 5' end of the intron are probably the authentic branch point sequence, and all of them branch at guanosine 328 instead of the typical adenosine. Unusually, the BPS of intron 1 of HPV-16 is a suboptimal sequence (AGUGAGU) that differs from the eukaryotic consensus BPS, which correlates with the splicing profile observed for early transcripts of HPV-16 in tumors and tumor derived cell lines. The implications of this unusual branch point sequence for splicing of the HPV-16 pre-mRNA are discussed.