Abstract The first cases of COVID-19, caused by the virus called SARS-CoV-2, were recorded in Wuhan, China, in December 2019; however, its transmission ability caused for the infection to be practically present throughout the world six months later. The origin of the virus appears to be zoonotic; it has been proposed that it comes from a bat and that it may have had an intermediate host that led to its introduction in the human population. SARS-CoV-2 is an enveloped virus, with a positive single-stranded RNA genome, and it binds to the angiotensin-converting enzyme, present in susceptible cells, to infect the human respiratory system. Although other coronaviruses have been previously known, they have not had the same impact, and, therefore, research on pharmacological treatments is not sufficiently developed to face the current challenge. Almost since the beginning of the epidemic, several molecules have been proposed for the treatment of infection; however, there is not yet a drug available with sufficient effectiveness for treatment. This review describes SARS-CoV-2 main characteristics, its replicative cycle, its possible origin and some advances in the development of antiviral treatments.

Resumen Los primeros casos de COVID-19, causada por el virus denominado SARS-CoV-2, se registraron en Wuhan, China, en diciembre de 2019; sin embargo, su capacidad de transmisión ocasionó que seis meses después la infección prácticamente estuviera presente en todo el mundo. El origen del virus parece ser zoonótico; se propone que proviene del murciélago y podría haber tenido un hospedero intermediario que llevó a su introducción en la población humana. SARS-CoV-2 es un virus envuelto, con genoma de ARN de cadena sencilla en sentido positivo y se ancla a la enzima convertidora de angiotensina, presente en las células susceptibles para infectar el sistema respiratorio de los humanos. Aunque previamente se han conocido otros coronavirus, no han tenido el mismo impacto, por lo que la investigación en tratamientos farmacológicos no tiene el desarrollo suficiente para afrontar el reto actual. Casi desde el comienzo de la epidemia se han propuesto moléculas para el tratamiento de la infección, sin embargo, aún no se cuenta con un fármaco con suficiente efectividad terapéutica. En esta revisión se describen las características principales de SARS-CoV-2, su ciclo replicativo, su posible origen y algunos avances en el desarrollo de tratamientos antivirales.

OBJECTIVE: To identify the prevalence and factors associated with cervical human papillomavirus infection in women with systemic lupus erythematosus METHODS: This cross-sectional study collected traditional and systemic lupus erythematosus-related disease risk factors, including conventional and biologic therapies. A gynecological evaluation and cervical cytology screen were performed. Human papillomavirus detection and genotyping were undertaken by PCR and linear array assay. RESULTS: A total of 148 patients were included, with a mean age and disease duration of 42.5±11.8 years and 9.7±5.3 years, respectively. The prevalence of squamous intraepithelial lesions was 6.8%. The prevalence of human papillomavirus infection was 29%, with human papillomavirus subtype 59 being the most frequent. Patients with human papillomavirus were younger than those without the infection (38.2±11.2 vs. 44.2±11.5 years, respectively; p = 0.05), and patients with the virus had higher daily prednisone doses (12.8±6.8 vs. 9.7±6.7 mg, respectively; p = 0.01) and cumulative glucocorticoid doses (14.2±9.8 vs. 9.7±7.3 g, respectively; p = 0.005) compared with patients without. Patients with human papillomavirus infection more frequently received rituximab than those without (20.9% vs. 8.5%, respectively; p = 0.03). In the multivariate analysis, only the cumulative glucocorticoid dose was associated with human papillomavirus infection. CONCLUSIONS: The cumulative glucocorticoid dose may increase the risk of human papillomavirus infection. Although rituximab administration was more frequent in patients with human papillomavirus infection, no association was found. Screening for human papillomavirus infection is recommended in women with systemic lupus erythematosus.

Porcine rubulavirus (PoRV) is an emerging virus causing meningo-encephalitis and reproductive failures in pigs. Little is known about the pathogenesis and immune evasion of this virus; therefore research on the mechanisms underlying tissue damage during infection is essential. To explore these mechanisms, the effect of PoRV on the transcription of interferon (IFN) pathway members was analyzed in vitro by semi-quantitative RT-PCR. Ten TCID50 of PoRV stimulated transcription of IFNα, IFNβ, STAT1, STAT2, p48 and OAS genes in neuroblastoma cells, whereas infection with 100 TCID50 did not stimulate transcription levels more than non-infected cells. When the cells were primed with IFNα, infection with 1 TCDI50 of PoRV sufficed to stimulate the transcription of the same genes, but 10 and 100 TCID50 did not modify the transcription level of those genes as compared with non-infected and primed controls. MxA gene transcription was observed only when the cells were primed with IFNα and stimulated with 10 TCID50, whereas 100 TCID50 of PoRV did not modify the MxA transcription level as compared to non-infected and primed cells. Our results show that PoRV replication at low titers stimulates the expression of IFN-responsive genes in neuroblastoma cells, and suggest that replication of PoRV at higher titers inhibits the transcription of several members of the IFN pathway. These findings may contribute to the understanding of the pathogenesis of PoRV.

Avian influenza viruses produce mainly respiratory and intestinal diseases. Their relevance in the generation of pandemic strains has led to a large amount of research to understand their distribution in nature, as well as the relations that become established for the effective transmission among different hosts. Waterfowl have been recognized as their natural reservoir and they play an important role in the propagation and generation of the diversity of these viruses. The emergence of new influenza viruses with pandemic potential among the human population (H5N1 of avian origin or recombinant H1N1 with avian segments) point our lack of information on many aspects of the ecology and epidemiology of these viruses in their natural hosts to enable the implementation of more effective prevention and control measures. In this review, we attempt to make a critical essay on the current state of knowledge on the biotic and abiotic factors that influence the ecology and epidemiology of the influenza A viruses in wild birds.

Los virus influenza ocasionan enfermedades respiratorias e intestinales. Su importancia en la generación de cepas pandémicas ha conducido a la realización de intensa investigación científica para entender y conocer su distribución en la naturaleza, así como las relaciones que se establecen para la transmisión efectiva entre diferentes hospederos. Las aves acuáticas principalmente del orden Anseriformes, se han reconocido como el reservorio de estos virus y tienen una participación crucial en la propagación y generación de diversidad de estos virus. La emergencia de nuevos virus influenza con potencial pandémico entre la población humana (H5N1 de origen aviar y el actual virus pandémico H1N1 que presenta segmentos aviares), resalta la falta de información sobre muchos aspectos de la ecología y epidemiología de estos virus en sus hospederos naturales, que permitan la implementación de medidas más efectivas de prevención y control. En esta contribución revisamos el estado del arte del conocimiento sobre los factores bióticos y abióticos que influyen en la ecología y epidemiología de los virus influenza en aves silvestres.

Cervical cancer is an important health problem in women living in developing countries. Infection with some genotypes of human papillomavirus (HPV) is the most important risk factor associated with cervical cancer. Little information exists about HPV genotype distribution in rural and suburban regions of Mexico. Thus, we determined the prevalence of HPV genotypes in women from Tlaxcala, one of the poorest states in central Mexico, and we evaluated age infection prevalence and risk factors associated with cervical neoplasm. A cross-sectional study was conducted in 236 women seeking gynecological care at the Mexican Institute for Social Security in Tlaxcala, Mexico. Cervical scrapings were diagnosed as normal, low-grade, and high-grade squamous intraepithelial lesions (LGSIL, HGSIL). Parallel samples were used to detect HPV genotypes by PCR assays using type-specific primers for HPV 6, 11, 16, 18, and 31. An epidemiological questionnaire was applied. Prevalence of HPV infection was 31.3%. From the infected samples, prevalence of HPV 16 was 45.9%; HPV 18, 31.1%; HPV 31, 16.2%; HPV 6, 10.8%; HPV 11, 6.7%. With regard to age, the highest HPV prevalence (43.5%) was found in the 18- to 24-year-old group and the lowest (19%) in the 45- to 54-year-old group. None of the risk factors showed association with cervical neoplasia grade. HPV 16 was the most common in cervical lesions. HPV was present in 22% of normal samples and, of these, 82.6% represented high-risk HPVs. Tlaxcala showed HPV prevalence comparable to that of the largest cities in Mexico, with higher prevalence for HPV 31.

Highly pathogenic avian influenza virus (HPAI) H5N1 is a global threat due to its zoonotic and pandemic potential. Then, concern arises and the need to have early detection tools to minimize the impact on human and animal health. In this work, a molecular detection method was implemented to detect matrix (M), hemagglutinin (H5) and neuraminidase (N1) genes of HPAI avian influenza virus H5N1, based on real time RT-PCR (RRT-PCR). Positive controls were constructed from reference RNA viral A/Vietnam/1203/2004 (H5N1), cloned into plasmidic vectors and sequenced. Assay detection sensitivity was assessed with standard curves for each gene. Assay sensitivity was 10² DNA copies/μl in all cases. Curves showed amplification efficiency higher than 90% and R²>0.99. This method could be useful for bird monitoring campaigns and as a screening procedure for clinical samples.

El virus de la influenza aviar H5N1 de alta patogenicidad mantiene el alerta mundial debido a su potencial zoonótico y pandémico. Surge entonces la necesidad de contar con herramientas para la detección temprana y de esta forma reducir el impacto potencial a la salud humana y animal. En este estudio se estandarizó un método de detección molecular de los genes de la matriz (M), hemaglutinina (H5) y neuraminidasa (N1) del virus de la influenza aviar H5N1 de alta patogenicidad de linaje asiático, mediante transcripción-reversa y reacción en cadena de la polimerasa en tiempo real (RRT-PCR). A partir de un ARN viral de referencia cepa A/Vietnam/1203/2004 (H5N1) se construyeron controles positivos mediante clonación de productos de PCR. Los estándares de naturaleza plasmídica se emplearon en la obtención de curvas estándar para determinar los límites de detección de la técnica. La sensibilidad observada para todos los genes analizados fue de 10² copias de ADN/μL. Las curvas mostraron una eficiencia superior al 90%, y R²>0,99. Este método puede ser útil en las campañas de monitoreo del virus en aves migratorias, así como para el tamizaje de muestras clínicas de humanos, en una emergencia de salud.

La sialilación alterada que se ha detectado durante la transformación maligna, en los tumores con invasión y metástasis ha sido asociada con un incremento en la transcripción de sialiltransferasas (STs). En carcinoma escamoso cervical invasor ha sido detectado un incremento en la expresión del ARNm de STs (ST3Gal III y ST6Gal I). Un estudio realizado en muestras de cérvix mostró un ligero incremento en la expresión de ácido siálico en lesiones inflamatorias benignas y un incremento moderado en neoplasia severa, con respecto al tejido normal, sin embargo, a la fecha la expresión alterada de STs en la neoplasia intraepitelial cervical no ha sido evaluada. Este estudio tuvo como finalidad investigar los cambios en el nivel de transcripción de tres STs (ST3Gal III, ST3Gal IV y ST6Gal I) en la neoplasia intraepitelial cervical (NIC). Para ello se analizaron 35 biopsias de cérvix clasificadas como: normal, NIC 1, NIC 2 y NIC 3, mediante ensayos semicuantitativos de RT-PCR. El nivel de transcripción de las tres STs se incrementó en las muestras con diagnóstico de neoplasia intraepitelial cervical con respecto al tejido normal, con una diferencia significativa de p < 0.001 (Mann-Whitney U test) para todas las enzimas. Nuestros resultados sugieren que la expresión alterada de las STs: ST3Gal III, ST3Gal IV y ST6Gal I, en la neoplasia intraepitelial cervical puede tener un papel importante durante la transformación maligna y estar relacionada con los incrementos en la expresión de ácido siálico detectado en tejido con neoplasia cervical.

Altered sialylation observed during oncogenic transformation, tumor metastases and invasion, has been associated with enhanced sialyltransferases (STs) transcription. Increased mRNA expression of STs (ST6Gal I, ST3Gal III) has been detected in invasive cervical squamous cell carcinoma. A study of the sialic acid concentration in local tissue of cervix and in serum showed a slight elevation in benign inflammatory lesions and a moderate elevation in severe neoplasia, but to date, altered expression of STs in cervical intraepithelial neoplasia has not yet been evaluated. This study investigates the changes in mRNA expression of three STs (ST6Gal I, ST3Gal III, and ST3Gal IV) in cervical intraepithelial lesions (CIN). Alterations of these STs mRNA expression were examined in 35 cervix specimens classified as normal, CIN 1, CIN 2 and CIN 3, by semiquantitative reverse transcription-polymerase chain reaction. mRNA expression of the three STs was enhanced in CIN 1, CIN 2 and CIN 3 with respect to normal tissue, with a significant difference of p < 0.001 (Mann-Whitney U test) for all the enzymes. Our results suggest that altered expression of ST3Gal III, ST3Gal IV and ST6Gal I in CIN could play an important role during malignant transformation and could be related with the enhanced sialic acid expression detected in neoplasic tissues.

A point mutation from guanine (G) to adenine (A) at nucleotide position 1081 in the hemagglutinin-neuraminidase (HN) gene has been associated with neurovirulence of Urabe AM9 mumps virus vaccine. This mutation corresponds to a glutamic acid (E) to lysine (K) change at position 335 in the HN glycoprotein. We have experimentally demonstrated that two variants of Urabe AM9 strain (HN-A1081 and HN-G1081) differ in neurotropism, sialic acidbinding affinity and neuraminidase activity. In the present study, we performed a structure-function analysis of that amino acid substitution; the structures of HN protein of both Urabe AM9 strain variants were predicted. Based on our analysis, the E/K mutation changes the protein surface properties and to a lesser extent their conformations, which in turn reflects in activity changes. Our modeling results suggest that this E/K interchange does not affect the structure of the sialic acid binding motif; however, the electrostatic surface differs drastically due to an exposed short alpha helix. Consequently, this mutation may affect the accessibility of HN to substrates and membrane receptors of the host cells. Our findings appear to explain the observed differences in neurotropism of these vaccine strains.

El Rubulavirus porcino causa un síndrome neurológico y reproductivo en cerdos, hasta ahora reportado sólo en México. Los virus aislados se agrupan de acuerdo con los síntomas principales observados durante los brotes en: a) neutrópicos en lechones, b) neurotrópicos en lechones/gonadotrópicos en adultos y c) gonadotrópicos en adultos. En este trabajo se estudiaron tres cepas: La Piedad Michoacán (LPM) y Producción Animal "Cerdos" 1 (PAC1) y 3 (PAC3), ubicadas respectivamente en cada grupo. Las propiedades estudiadas se relacionan principalmente con dos proteínas de la envoltura viral, la hemaglutinina-neuraminidasa (HN) y la proteína de fusión (F). Se cuantificaron el efecto citopático y las actividades de hemólisis, hemaglutinación (HA) y neuraminidasa (NA). En cultivo celular la cepa PAC1 presentó una mayor actividad fusogénica, sin embargo PAC3 presentó la mayor actividad citolítica. La cepa PAC3 fue la primera en ser detectada en sobrenadante de células infectadas (HA, NA y genoma), lo que muestra que sus viriones son liberados al medio antes que las otras dos cepas. PAC3 tuvo las actividades más altas de HA y NA, sin embargo, PAC1 presentó una mayor termoestabilidad en estas actividades de HN y un perfil de substrato algo distinto de los observados para LPM y PAC3. Estos datos sugieren que la actividad de NA está relacionada con la virulencia del RVP.

Biological characterization of three natural isolates of the porcine rubulavirus (Mexico). Porcine rubulavirus (PoRV) produces a neurological and reproductive syndrome in pigs called the blue-eye disease, known only from Mexico. Several isolates were grouped by the main symptoms presented during outbreaks: a) neurotropic in piglets, b) broadly neurotropic in piglets and gonadotropic in adults, and c) gonadotropic in adults. We studied some biological properties of three strains, which fall in one of each virus group: La Piedad Michoacán (LPM) and Producción Animal Cerdos 1 (PAC1) and 3 (PAC3), respectively. The analyzed viral properties are mainly related with the trans-membrane hemagglutinin-neuraminidase (HN) and fusion (F) proteins, such as cytopathic effect, hemolysis, hemagglutinating (HA) and neuraminidase (NA) activities. In the infection assays PAC1 strain presented the highest fusogenicity level; however, the most cytolytic strain was PAC3. In addition, HA and NA activities and viral genome of PAC3 strain was detected in supernatants during cell infection earlier than in the other two strains, which shows that PAC3 virions release from the host cell earlier than LPM and PAC1. Experimental determination in purified viruses shows that PAC3 presented a higher HA and NA activities; however, PAC1 shows other interesting properties, such as a high thermostability of HN and differences about substrate profile respect to LPM and PAC3. Our data suggest that NA activity is associated with the virulence of RVP. Rev. Biol. Trop. 56 (2): 487-499. Epub 2008 June 30.