Hilda Montero

Rotavirus Infection Induces the Phosphorylation of eIF2α but Prevents the Formation of Stress Granules

ABSTRACT Early during the infection process, rotavirus causes the shutoff of cell protein synthesis, with the nonstructural viral protein NSP3 playing a vital role in the phenomenon. In this work, we have found that the translation initiation factor 2α (eIF2α) in infected cells becomes phosphorylated early after virus infection and remains in this state throughout the virus replication cycle, leading to a further inhibition of cell protein synthesis. Under these restrictive conditions, however, the viral proteins and some cellular proteins are efficiently translated. The phosphorylation of eIF2α was shown to depend on the synthesis of three viral proteins, VP2, NSP2, and NSP5, since in cells in which the expression of any of these three proteins was knocked down by RNA interference, the translation factor was not phosphorylated. The modification of this factor is, however, not needed for the replication of the virus, since mutant cells that produce a nonphosphorylatable eIF2α sustained virus replication as efficiently as wild-type cells. In uninfected cells, the phosphorylation of eIF2α induces the formation of stress granules, aggregates of stalled translation complexes that prevent the translation of mRNAs. In rotavirus-infected cells, even though eIF2α is phosphorylated these granules are not formed, suggesting that the virus prevents the assembly of these structures to allow the translation of its mRNAs. Under these conditions, some of the cellular proteins that form part of these structures were found to change their intracellular localization, with some of them having dramatic changes, like the poly(A) binding protein, which relocates from the cytoplasm to the nucleus in infected cells, a relocation that depends on the viral protein NSP3.

Rotavirus Nonstructural Protein NSP3 Is Not Required for Viral Protein Synthesis

ABSTRACT Initiation is the rate-limiting step in protein synthesis and therefore an important target for regulation. For the initiation of translation of most cellular mRNAs, the cap structure at the 5′ end is bound by the translation factor eukaryotic initiation factor 4E (eIF4E), while the poly(A) tail, at the 3′ end, is recognized by the poly(A)-binding protein (PABP). eIF4G is a scaffold protein that brings together eIF4E and PABP, causing the circularization of the mRNA that is thought to be important for an efficient initiation of translation. Early in infection, rotaviruses take over the host translation machinery, causing a severe shutoff of cell protein synthesis. Rotavirus mRNAs lack a poly(A) tail but have instead a consensus sequence at their 3′ ends that is bound by the viral nonstructural protein NSP3, which also interacts with eIF4GI, using the same region employed by PABP. It is widely believed that these interactions lead to the translation of rotaviral mRNAs, impairing at the same time the translation of cellular mRNAs. In this work, the expression of NSP3 in infected cells was knocked down using RNA interference. Unexpectedly, under these conditions the synthesis of viral proteins was not decreased, while the cellular protein synthesis was restored. Also, the yield of viral progeny increased, which correlated with an increased synthesis of viral RNA. Silencing the expression of eIF4GI further confirmed that the interaction between eIF4GI and NSP3 is not required for viral protein synthesis. These results indicate that NSP3 is neither required for the translation of viral mRNAs nor essential for virus replication in cell culture.

Stress granules in the viral replication cycle.

As intracellular parasites, viruses require a host cell in order to replicate. However, they face a series of cellular responses against infection. One of these responses is the activation of the double-stranded RNA (dsRNA)-activated protein kinase R (PKR). PKR phosphorylates the α subunit of eukaryotic translation initiation factor 2 (eIF2α), which in turn results in global protein synthesis inhibition and formation of stress granules (SGs). Recent studies have shown that SGs can interfere with the replicative cycle of certain viruses. This review addresses how viruses have evolved different control strategies at the SG level to ensure an efficient replication cycle during the cellular stress response triggered by the viral infection.

Characterization of an influenza A virus in Mexican swine that is related to the A/H1N1/2009 pandemic clade

In the spring of 2009, swine-origin influenza H1N1pdm09 viruses caused the first influenza pandemic of this century. We characterized the influenza viruses that circulated early during the outbreak in Mexico, including one newly sequenced swine H1N1pdm09 virus and three newly sequenced human H1N1pdm09 viruses that circulated in the outbreak of respiratory disease in La Gloria, Veracruz. Phylogenetic analysis revealed that the swine isolate (A/swine/Mexico/4/2009) collected in April 2009 is positioned in a branch that is basal to the rest of the H1N1pdm09 clade in two (NP and PA) of the eight single-gene trees. In addition, the concatenated HA-NA and the complete whole-genome trees also showed a basal position for A/swine/Mexico/4/2009. Furthermore, this swine virus was found to share molecular traits with non-H1N1pdm09 H1N1 viral lineages. These results suggest that this isolate could potentially be the first one detected from a sister lineage closely related to the H1N1pdm09 viruses.

Clinical Characteristics and Genetic Variability of Human Rhinovirus in Mexico

Human rhinovirus (HRV) is a leading cause of acute respiratory infection (ARI) in young children and infants worldwide and has a high impact on morbidity and mortality in this population. Initially, HRV was classified into two species: HRV-A and HRV-B. Recently, a species called HRV-C and possibly another species, HRV-D, were identified. In Mexico, there is little information about the role of HRV as a cause of ARI, and the presence and importance of species such as HRV-C are not known. The aim of this study was to determine the clinical characteristics and genetic variability of HRV in Mexican children. Genetic characterization was carried out by phylogenetic analysis of the 5′-nontranslated region (5′-NTR) of the HRV genome. The results show that the newly identified HRV-C is circulating in Mexican children more frequently than HRV-B but not as frequently as HRV-A, which was the most frequent species. Most of the cases of the three species of HRV were in children under 2 years of age, and all species were associated with very mild and moderate ARI.

eIF4E as a Control Target for Viruses

Translation is a complex process involving diverse cellular proteins, including the translation initiation factor eIF4E, which has been shown to be a protein that is a point for translational regulation. Viruses require components from the host cell to complete their replication cycles. Various studies show how eIF4E and its regulatory cellular proteins are manipulated during viral infections. Interestingly, viral action mechanisms in eIF4E are diverse and have an impact not only on viral protein synthesis, but also on other aspects that are important for the replication cycle, such as the proliferation of infected cells and stimulation of viral reactivation. This review shows how some viruses use eIF4E and its regulatory proteins for their own benefit in order to spread themselves.

Viral coinfection in acute respiratory infection in Mexican children treated by the emergency service: A cross-sectional study

BackgroundAcute respiratory infections (ARIs) cause illness. Children under five years of age are highly vulnerable to these infections. Viral coinfection or multiple viral infection is a variable that can have a significant impact on the evolution of these diseases.MethodsThis cross-sectional study was carried out in Mexican children (under five years of age) who had an ARI and who were treated by an emergency service in a hospital in Guadalajara, Jalisco, Mexico. The viral etiology, as well as the presence of multiple viral infections, was determined. A structured questionnaire was used to obtain demographic and clinical information. Odds ratio (OR) was calculated, and univariate and multivariate analyses using logistic regression were performed.ResultsIn the study population, metapneumovirus (hMPV) was the most frequent virus (22%), followed by adenovirus (hAD) (16%), respiratory syncytial virus (RSV) (14%), rhinovirus (hRV) (12%), bocavirus (hBoV) (9%), influenza virus (IF) (7%), and parainfluenza (PIF) (4%). The frequency of viral coinfections was 31.62%, and multiple logistic regression analysis revealed that hMPV, RSV, PIF, and hBoV were independently associated with multiple viral infection. No difference was found in the clinical manifestation of children with simple and multiple infections. Simple hMPV infection was associated with patients who presented with severe ARI. Using a multivariate analysis, we found that overcrowding is associated with coinfection when the viral etiology was hRV (OR = 2.56, 95% confidence interval (CI) 1.07 to 6.13), IF (OR = 2.56, 95% CI 1.07 to 6.13), PIF (OR = 2.96, 95% CI 1.15 to 7.65), hAD (OR = 2.56, 95% CI 1.07 to 6.13), and hBoV (OR = 2.9, 95% CI 1.14 to 7.34).ConclusionsViral coinfections are frequent in children requiring treatment by an emergency service. However, the severity of ARI is similar to that of children with a simple infection. The hMPV is common and may confer a significant disease burden in the Mexican population. Finally, overcrowding is a housing characteristic that favors the development of coinfections.

Risk factors associated with gastric cancer in Mexico: education, breakfast and chili

BACKGROUND AND AIM the aim of the study was to use a validated questionnaire to identify factors associated with the development of gastric cancer (GC) in the Mexican population. METHODS the study included cases and controls that were paired by sex and ± 10 years of age at diagnosis. In relation to cases, 46 patients with a confirmed histopathological diagnosis of adenocarcinoma-type GC, as reported in the hospital records, were selected, and 46 blood bank donors from the same hospital were included as controls. The previously validated Questionnaire to Find Factors Associated with Gastric Cancer (QUFA-GC©) was used to collect data. Odds ratio (OR) and 95% confidence interval (IC) were estimated via univariate analysis (paired OR). Multivariate analysis was performed by logistic regression. A decision tree was constructed using the J48 algorithm. RESULTS an association was found by univariate analysis between GC risk and a lack of formal education, having smoked for ≥ 10 years, eating rapidly, consuming very hot food and drinks, a non-suitable breakfast within two hours of waking, pickled food and capsaicin. In contrast, a protective association against GC was found with taking recreational exercise and consuming fresh fruit and vegetables. No association was found between the development of GC and having an income that reflected poverty, using a refrigerator, perception of the omission of breakfast and time period of alcoholism. In the final multivariate analysis model, having no formal education (OR = 17.47, 95% CI = 5.17-76.69), consuming a non-suitable breakfast within two hours of waking (OR = 8.99, 95% CI = 2.85-35.50) and the consumption of capsaicin ˃ 29.9 mg capsaicin per day (OR = 3.77, 95% CI = 1.21-13.11) were factors associated with GC. CONCLUSIONS an association was found by multivariate analysis between the presence of GC and education, type of breakfast and the consumption of capsaicin. These variables are susceptible to intervention and can be identified via the QUFA-GC

4EBP1 Is Dephosphorylated by Respiratory Syncytial Virus Infection

Respiratory syncytial virus (RSV) requires protein biosynthesis machinery to generate progeny. There is evidence that RSV might alter some translation components since stress granules are formed in their host cells. Consistent with these observations, we found that RSV induces dephosphorylation of 4EBP1 (eIF4E-binding protein), an important cellular translation factor. Our results show no correlation between the 4EBP1 dephosphorylation time and the decrease in the global rate of protein synthesis. Interestingly, treatment with rapamycin stimulates virus generation. The results suggest that RSV is a virus that still contains unknown mechanisms involved in the translation of their mRNAs through the alteration or modification of some translation factors, such as 4EBP1, possibly to favor its replicative cycle.