Neutralization assay with SARS-CoV-1 and SARS-CoV-2 spike pseudotyped murine leukemia virions.

BACKGROUND: Virus neutralization by antibodies is an important prognostic factor in many viral diseases. To easily and rapidly measure titers of neutralizing antibodies in serum or plasma, we developed pseudovirion particles composed of the spike glycoprotein of SARS-CoV-2 incorporated onto murine leukemia virus capsids and a modified minimal murine leukemia virus genome encoding firefly luciferase. This assay design is intended for use in laboratories with biocontainment level 2 and therefore circumvents the need for the biocontainment level 3 that would be required for replication-competent SARS-CoV-2 virus. To validate the pseudovirion assay, we set up comparisons with other available antibody tests including those from Abbott, Euroimmun and Siemens, using archived, known samples. RESULTS: 11 out of 12 SARS-CoV-2-infected patient serum samples showed neutralizing activity against SARS-CoV-2-spike pseudotyped MLV viruses, with neutralizing titers-50 (NT50) that ranged from 1:25 to 1:1,417. Five historical samples from patients hospitalized for severe influenza infection in 2016 tested negative in the neutralization assay (NT50 < 25). Three serum samples with high neutralizing activity against SARS-CoV-2/MLV pseudoviruses showed no detectable neutralizing activity (NT50 < 25) against SARS-CoV-1/MLV pseudovirions. We also compared the semiquantitative Siemens SARS-CoV-2 IgG test, which measures binding of IgG to recombinantly expressed receptor binding domain of SARS-CoV-2 spike glycoprotein with the neutralization titers obtained in the pseudovirion assay and the results show high concordance between the two tests (R2 = 0.9344). CONCLUSIONS: SARS-CoV-2 spike/MLV pseudovirions provide a practical means of assessing neutralizing activity of antibodies in serum or plasma from infected patients under laboratory conditions consistent with biocontainment level 2. This assay offers promise also in evaluating immunogenicity of spike glycoprotein-based candidate vaccines in the near future.

Neutralization Assay with SARS-CoV-1 and SARS-CoV-2 Spike Pseudotyped Murine Leukemia Virions.

Antibody neutralization is an important prognostic factor in many viral diseases. To easily and rapidly measure titers of neutralizing antibodies in serum or plasma, we developed pseudovirion particles composed of the spike glycoprotein of SARS-CoV-2 incorporated onto murine leukemia virus capsids and a modified minimal MLV genome encoding firefly luciferase. These pseudovirions provide a practical means of assessing immune responses under laboratory conditions consistent with biocontainment level 2.

Transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) to animals: an updated review.

COVID-19 caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) originated in Wuhan (Hubei province, China) during late 2019. It has spread across the globe affecting nearly 21 million people with a toll of 0.75 million deaths and restricting the movement of most of the world population during the past 6 months. COVID-19 became the leading health, economic, and humanitarian challenge of the twenty-first century. In addition to the considerable COVID-19 cases, hospitalizations, and deaths in humans, several cases of SARS-CoV-2 infections in animal hosts (dog, cat, tiger, lion, and mink) have been reported. Thus, the concern of pet owners is increasing. Moreover, the dynamics of the disease requires further explanation, mainly concerning the transmission of the virus from humans to animals and vice versa. Therefore, this study aimed to gather information about the reported cases of COVID-19 transmission in animals through a literary review of works published in scientific journals and perform genomic and phylogenetic analyses of SARS-CoV-2 isolated from animal hosts. Although many instances of transmission of the SARS-CoV-2 have been reported, caution and further studies are necessary to avoid the occurrence of maltreatment in animals, and to achieve a better understanding of the dynamics of the disease in the environment, humans, and animals. Future research in the animal-human interface can help formulate and implement preventive measures to combat the further transmission of COVID-19.

Identification and Mechanism of Action of a Novel Small-Molecule Inhibitor of Arenavirus Multiplication.

UNLABELLED: Several arenaviruses cause hemorrhagic fever disease in humans and represent important public health problems in the regions where these viruses are endemic. In addition, evidence indicates that the worldwide-distributed prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) is an important neglected human pathogen. There are no licensed arenavirus vaccines and current antiarenavirus therapy is limited to the use of ribavirin that is only partially effective. Therefore, there is an unmet need for novel antiarenaviral therapeutics. Here, we report the generation of a novel recombinant LCM virus and its use to develop a cell-based high-throughput screen to rapidly identify inhibitors of LCMV multiplication. We used this novel assay to screen a library of 30,400 small molecules and identified compound F3406 (chemical name: N-[3,5-bis(fluoranyl)phenyl]-2-[5,7-bis(oxidanylidene)-6-propyl-2-pyrrolidin-1-yl-[1,3]thiazolo[4,5-d]pyrimidin-4-yl]ethanamide), which exhibited strong anti-LCMV activity in the absence of cell toxicity. Mechanism-of-action studies revealed that F3406 inhibited LCMV cell entry by specifically interfering with the pH-dependent fusion in the endosome compartment that is mediated by LCMV glycoprotein GP2 and required to release the virus ribonucleoprotein into the cell cytoplasm to initiate transcription and replication of the virus genome. We identified residue M437 within the transmembrane domain of GP2 as critical for virus susceptibility to F3406. IMPORTANCE: Hemorrhagic fever arenaviruses (HFA) are important human pathogens that cause high morbidity and mortality in areas where these viruses are endemic. In addition, evidence indicates that the worldwide-distributed prototypic arenavirus lymphocytic choriomeningitis virus (LCMV) is a neglected human pathogen of clinical significance. Concerns posed by arenavirus infections are aggravated by the lack of U.S. Food and Drug Administration-licensed arenavirus vaccines and current antiarenaviral therapy being limited to the off-label use of ribavirin that is only partially effective. Here we describe a novel recombinant LCMV and its use to develop a cell-based assay suitable for HTS to rapidly identify inhibitors arenavirus multiplication. The concepts and experimental strategies we describe in this work provide the bases for the rapid identification and characterization of novel anti-HFA therapeutics.

Host factors influencing susceptibility to HIV infection and AIDS progression.

Transmission of HIV first results in an acute infection, followed by an apparently asymptomatic period that averages ten years. In the absence of antiretroviral treatment, most patients progress into a generalized immune dysfunction that culminates in death. The length of the asymptomatic period varies, and in rare cases infected individuals never progress to AIDS. Other individuals whose behavioral traits put them at high-risk of HIV transmission, surprisingly appear resistant and never succumb to infection. These unique cases highlight the fact that susceptibility to HIV infection and progression to disease are complex traits modulated by environmental and genetic factors. Recent evidence has indicated that natural variations in host genes can influence the outcome of HIV infection and its transmission. In this review we summarize the available literature on the roles of cellular factors and their genetic variation in modulating HIV infection and disease progression.

Lentiviral vectors interfering with virus-induced CD4 down-modulation potently block human immunodeficiency virus type 1 replication in primary lymphocytes.

CD4 down-modulation is essential for the production of human immunodeficiency virus (HIV) infectious particles. Disease progression correlates with enhanced viral induced CD4 down-modulation, and a subset of long-term nonprogressors carry viruses defective in this function. Despite multiple pieces of evidence highlighting the importance of this function in viral pathogenesis in vivo, to date, HIV-induced CD4 down-modulation has not been used as a target for intervention. We describe here HIV-based vectors that deliver truncated CD4 molecules resistant to down-modulation by the viral products Nef and Vpu. Infection of cells previously transduced with these vectors proceeded normally, and viral particles were released in normal amounts. However, the infectivity of the released virions was reduced 1,000-fold. Lentiviral vectors expressing truncated CD4 molecules were efficient at blocking HIV-1 infectivity and replication in several cell lines and in CD4-positive primary lymphocytes. The findings presented here provide proof-of-principle that approaches targeting the virus-induced CD4 down-modulation may constitute the basis for novel anti-HIV therapies.

Enhanced CD4 down-modulation by late stage HIV-1 nef alleles is associated with increased Env incorporation and viral replication.

Three viral proteins participate in the down-modulation of CD4 in human immunodeficiency virus type 1 (HIV-1)-infected cells. The underlying mechanisms have been extensively investigated. However, the physiological relevance of this phenomenon remains poorly understood. To address the role of CD4 down-modulation in HIV-1 pathogenesis in vivo, we have characterized the functional properties of nef alleles isolated from seven HIV-1-infected patients at either the stage of AIDS (late alleles) or during the asymptomatic phase of infection (early alleles). HIV-1 variants carrying these nef alleles showed striking differences in CD4 down-modulation, virus infectivity, and replication properties. Infection of T cells with late strains resulted in production of viral particles with enhanced infectivity, as compared with variants carrying early nef alleles. These differences in infectivity were observed only when viruses were produced in cells with high levels of the viral receptor, suggesting a functional link between CD4 levels and the ability of Nef to down-modulate CD4 and to enhance viral infectivity. Similarly, late nef alleles were substantially more active than early nef genes in stimulating HIV-1 replication in high CD4-positive cells, including primary lymphocytes, but not in cells expressing low levels of the CD4 receptor. Single-round assays showed that differences in infectivity between late and early strains are largely reduced when evaluated in target cells with high levels of CD4, suggesting that the inhibitory effect occurs at the entry step. Supporting this, enhanced CD4 down-modulation by late nef alleles was associated with higher levels of envelope incorporation into viral particles, a phenomenon that likely accounted for the augmented infectivity. Our data suggest a mechanistic link between the Nef-mediated CD4 down-modulation and the enhancement of replication in CD4-positive lymphocytes. As progression to disease occurs, HIV-1 Nef variants with enhanced ability to down-modulate CD4 are selected. These strains efficiently overcome the deleterious effects of CD4 and replicate more aggressively in CD4-positive primary lymphocytes. These results highlight the importance of the virus-induced CD4 down-modulation in HIV-1 pathogenesis.

The physiological relevance of CD4 receptor down-modulation during HIV infection.

Upon binding to the CD4 receptor the HIV envelope protein undergoes conformational changes that culminate in the fusion of the viral and cellular membranes. A few hours later, a sophisticated set of processes is initiated to ensure the down-modulation of the viral receptor. Three viral proteins participate in this process: Nef, Env, and Vpu, suggesting that this function is critical for virus replication. The mechanisms of action of these proteins have been extensively characterized. However, the physiological relevance of the virus-induced CD4 down-modulation remains a focus of controversy, and the impact of this function on the viral life cycle has been underestimated. This review summarizes current hypotheses explaining why HIV needs to reduce expression of its own receptor, and discusses the experimental evidence supporting them. Recent findings indicate that efficient CD4 down-modulation is essential for the production of infectious particles, and highlight the importance of this function in HIV pathogenesis in vivo. Progression to disease correlates with enhanced viral induced CD4 down-modulation, and a subset of long-term nonprogressors carry viruses defective in this function. To date, the HIV-induced CD4 down-modulation has not been targeted for therapeutic intervention. Addressing the reasons why this function is so critical and understanding the interplay between viral and host factors governing surface expression of CD4 may provide clues for the development of new antiviral strategies.

Human immunodeficiency virus type 1 Vpr protein does not modulate surface expression of the CD4 receptor.

The CD4 receptor is required for the entry of human immunodeficiency virus (HIV) into target cells. It has long been known that Nef, Env, and Vpu participate in the removal of the viral receptor from the cell surface. Recently, it has been proposed that the HIV type 1 (HIV-1) Vpr protein may also play a role in the downmodulation of CD4 from the surfaces of infected cells (L. Conti, B. Varano, M. C. Gauzzi, P. Matarrese, M. Federico, W. Malorani, F. Belardelli, and S. Gessani, J. Virol. 74:10207-10211, 2000). To investigate the possible role of Vpr in the downregulation of the viral receptor Vpr alleles from HIV-1 and simian immunodeficiency virus were transiently expressed in transformed T cells and in 293T fibroblasts, and their ability to modulate surface CD4 was evaluated. All Vpr alleles efficiently arrested cells in the G(2) stage of the cell cycle. However, none of the tested Vpr proteins altered the expression of CD4 on the cell surface. In comparison, HIV-1 Nef efficiently downmodulated surface CD4 in all the experimental settings. Transformed T cells and primary lymphocytes were challenged with wild-type, Nef-defective, and Vpr-defective viruses. A significant reduction in the HIV-induced downmodulation of surface CD4 was observed in viruses lacking Nef. However, Vpr-deletion-containing viruses showed no defect in their ability to remove CD4 from the surfaces of infected cells. Our results indicate that Vpr does not play a role in the HIV-induced downmodulation of the CD4 receptor.

Cell surface CD4 interferes with the infectivity of HIV-1 particles released from T cells.

The CD4 protein is required for the entry of human immunodeficiency virus (HIV) into target cells. Upon expression of the viral genome, three HIV-1 gene products participate in the removal of the primary viral receptor from the cell surface. To investigate the role of surface-CD4 in HIV replication, we have created a set of Jurkat cell lines which constitutively express surface levels of CD4 comparable to those found in peripheral blood lymphocytes and monocytes. Expression of low levels of CD4 on the surface of producer cells exerted an inhibitory effect on the infectivity of HIV-1 particles, whereas no differences in the amount of cell-free p24 antigen were observed. Higher levels of cell surface CD4 exerted a stronger inhibitory effect on infectivity, and also affected the release of free virus in experiments where the viral genomes were delivered by electrotransfection. The CD4-mediated inhibition of HIV-1 infectivity was not observed in experiments where the vesicular stomatitis virus G protein was used to pseudotype viruses, suggesting that an interaction between CD4 and gp120 is required for interference. In contrast, inhibition of particle release by high levels of cell-surface CD4 was not overcome by pseudotyping HIV-1 with foreign envelope proteins. Protein analysis of viral particles released from HIV-infected Jurkat-T cells revealed a CD4-dependent reduction in the incorporation of gp120. These results demonstrate that physiological levels of cell-surface CD4 interfere with HIV-1 replication in T cells by a mechanism that inhibits envelope incorporation into viral membranes, and therefore provide an explanation for the need to down-modulate the viral receptor in infected cells. Our findings have important implications for the spread of HIV in vivo and suggest that the CD4 down-modulation function may be an alternative target for therapeutic intervention.

La edad materna avanzada como factor de riesgo de morbimortalidad materna y perinatal / Advanced maternal age as a risk factor for maternal and perinatal morbidity and mortality

Objetivos: Conocer el riesgo para el parto y la morbimortalidad maternoperinatal en la gestante añosa. Diseño: estudio clínico retrospectivo de corte transversal. Material y método: gestante de 35 años o mayor atendida en el Hospital San Juan de Dios del Callao, entre enero de 1990 y diciembre de 1991. Se compara los resultados del parto y la morbimortalidad maternoperinatal con los de la gestante menor de 35 años atendida en el mismo lapso. Resultados: De 10 445 partos, 744 correspondieron a gestantes añosas (7,1 por ciento). Hubo significativamente más partos distócicos en las gestantes añosas (19,2 por ciento vs 10,6 por ciento), incluyendo presentaciones podálica (7,3 por ciento), transversa (0,9 por ciento) y otras raras (0,6 por ciento), habiéndose atendido más partos podálicos por vía vaginal (6,1 por ciento vs 2 por ciento); la incidencia de cesáreas fue 11 por ciento. La cesárea por cesareada anterior fue la causa más frecuente en ambos grupos. La tasa de mortalidad materna fue 397 por 100 000 nv en la gestante mayor y 41 por 100 000 nv en la menor de 35 años, diferencia de significancia estadística. En la madre añosa, la mortalidad perinatal se debió con mayor frecuencia a la asfixia severa (30 por ciento), prematuridad (16,6 por ciento) y malformaciones congénitas (13,3 por ciento). La tasa de mortalidad perinatal en gestantes añosas fue 39,7 por ciento 1000 nv, y en menores de 35 años 24,8 por 1000 nv, diferencia estadísticamente significativa. La tasa global de mortalidad perinatal fue 27,8 por 1000 nv. Conclusiones: La gestante de 35 años o más tiene riesgo reproductivo alto y requiere de buena orientación preconcepcional, control prenatal con enfoque de riesgo y descarte de malformaciones fetales, parto institucionalizado y monitorización materna y perinatal pre, intra y posparto.