Dengue vaccine: local decisions, global consequences

Implementation of IFPTML Computational Models in Drug Discovery Against Flaviviridae Family

The Flaviviridae family consists of single-stranded positive-sense RNA viruses, which contains the genera Flavivirus, Hepacivirus, Pegivirus, and Pestivirus. Currently, there is an outbreak of viral diseases caused by this family affecting millions of people worldwide, leading to significant morbidity and mortality rates. Advances in computational chemistry have greatly facilitated the discovery of novel drugs and treatments for diseases associated with this family. Chemoinformatic techniques, such as the perturbation theory machine learning method, have played a crucial role in developing new approaches based on ML models that can effectively aid drug discovery. The IFPTML models have shown its capability to handle, classify, and process large data sets with high specificity. The results obtained from different models indicates that this methodology is proficient in processing the data, resulting in a reduction of the false positive rate by 4.25%, along with an accuracy of 83% and reliability of 92%. These values suggest that the model can serve as a computational tool in assisting drug discovery efforts and the development of new treatments against Flaviviridae family diseases.

Diagnostic Performance of Dengue Virus Envelope Domain III in Acute Dengue Infection

Dengue, one of the most prevalent illnesses caused by dengue viruses that are members of the genus Flavivirus, is a significant global health problem. However, similar clinical symptoms and high antigenic homologies with other Flaviviruses in the endemic area pose difficulties for differential diagnosis of dengue from other arbovirus infections. Here, we investigated four types of recombinant envelope protein domain III (DV-rED III) derived from four dengue virus (DENV) serotypes for diagnostic potential in detecting IgM in acute phase (mainly 2–3 days after onset of fever). Each independent DV-1, -3, and -4-rED III-ELISA showed less than 60% sensitivity, but the combined results of DV-1, -3, and -4-rED III-ELISA led to sensitivity of 81.82% (18/22) (95% CI, 59.72 to 94.81) and 100% specificity (46/46) (95% CI, 92.29 to 100.00) as each antigen compensated the other antigen-derived negative result. In conclusion, the independent combination of data derived from each recombinant antigen (DV1-, DV3-, and DV4-rED III) showed comparable efficacy for the detection of IgM in patients with acute-phase dengue infection.

Assessment of benefits and risks associated with dengue vaccination at the individual and population levels: a dynamic modeling approach

BACKGROUND

A case-cohort study, using a novel assay and data from three dengue vaccine efficacy trials, highlighted differences in vaccination outcomes according to baseline serostatus. Based on these results, we explored, with a model, the benefits and risks associated with vaccination.

RESEARCH DESIGN AND METHODS

Parameters of a previously developed transmission model were estimated with subject-level data from a case-cohort study. The model was used to assess vaccination outcomes for a range of transmission settings over 5-30 years, with or without indirect protection.

MAIN OUTCOME MEASURES

Symptomatic dengue cases, dengue hospitalizations, and severe dengue cases.

RESULTS

The model is consistent with previous results indicating a transitory period at increased risk for dengue-seronegative vaccine recipients (setting-dependent duration) and long-term benefits for dengue-seropositive recipients. At the population level, benefits to seropositive individuals over 10 years outweighed the risk to those seronegative in moderate to high transmission settings (≥50% seropositivity at age 9), especially in high transmission settings (no excess hospitalizations in dengue-seronegative for ≥80% seropositivity at age 9). Results were more favorable when longer time horizons or indirect protection were considered.

CONCLUSIONS

Results indicate a public health benefit associated with dengue vaccination especially in high-transmission settings, even with the initial excess risks to dengue-seronegative patients which diminish over time.

Elimination of Falciparum Malaria and Emergence of Severe Dengue: An Independent or Interdependent Phenomenon?

The global malaria burden, including falciparum malaria, has been reduced by 50% since 2000, though less so in Sub-Saharan Africa. Regional malaria elimination campaigns beginning in the 1940s, up-scaled in the 1950s, succeeded in the 1970s in eliminating malaria from Europe, North America, the Caribbean (except Haiti), and parts of Asia and South- and Central America. Dengue has grown dramatically throughout the pantropical regions since the 1950s, first in Southeast Asia in the form of large-scale epidemics including severe dengue, though mostly sparing Sub-Saharan Africa. Globally, the WHO estimates 50 million dengue infections every year, while others estimate almost 400 million infections, including 100 million clinical cases. Curiously, despite wide geographic overlap between malaria and dengue-endemic areas, published reports of co-infections have been scarce until recently. Superimposed acute dengue infection might be expected to result in more severe combined disease because both pathogens can induce shock and hemorrhage. However, a recent review found no reports on more severe morbidity or higher mortality associated with co-infections. Cases of severe dual infections have almost exclusively been reported from South America, and predominantly in persons infected by Plasmodium vivax. We hypothesize that malaria infection may partially protect against dengue – in particular falciparum malaria against severe dengue – and that this inter-species cross-protection may explain the near absence of severe dengue from the Sub-Saharan region and parts of South Asia until recently. We speculate that malaria infection elicits cross-reactive antibodies or other immune responses that infer cross-protection, or at least partial cross-protection, against symptomatic and severe dengue. Plasmodia have been shown to give rise to polyclonal B-cell activation and to heterophilic antibodies, while some anti-dengue IgM tests have high degree of cross-reactivity with sera from malaria patients. In the following, the historical evolution of falciparum malaria and dengue is briefly reviewed, and we explore early evidence of subclinical dengue in high-transmission malaria areas as well as conflicting reports on severity of co-morbidity. We also discuss examples of other interspecies interactions.

Age-specific seroprevalence of dengue infection in Hong Kong

A newly developed dengue virus vaccine (chimeric yellow fever virus-tetravalent dengue vaccine [CYD-TDV]) has recently been licensed for clinical use. The World Health Organization recommends vaccination for populations with seroprevalence of at least 70% to maximize public health impact. This study aimed to delineate the seroprevalence of dengue infection in Hong Kong. A total of 105 972 serum samples submitted for clinical testing during the period 2013-2015 were age-stratified and sex-stratified. For each year of collection, 25 samples were randomly selected from each age-sex group. Altogether, 2100 samples were tested for the dengue immunoglobulin G (IgG) antibody using a non-type-specific ELISA kit. The overall dengue IgG-positive rate was 4.6% and showed no significant change over the 3 years. The positive rate was not associated with sex, but a steep rise in seroprevalence for persons above 65 years (32.7%) was observed. The low dengue seroprevalence in Hong Kong does not support implementation of a national immunization program. Majority of the population in Hong Kong are susceptible to dengue infection, and a substantial proportion of persons older than 65 years could acquire secondary infection and are prone to develop severe dengue.

Estimation of expected dengue seroprevalence from passive epidemiological surveillance systems in selected areas of Argentina: A proxy to evaluate the applicability of dengue vaccination

BACKGROUND

Current recommendations about dengue vaccination by the World Health Organization depend on seroprevalence levels and serological status in populations and individuals. However, seroprevalence estimation may be difficult due to a diversity of factors. Thus, estimation through models using data from epidemiological surveillance systems could be an alternative procedure to achieve this goal.

OBJECTIVE

To estimate the expected dengue seroprevalence in children of selected areas in Argentina, using a simple model based on data from passive epidemiological surveillance systems.

METHODS

A Markov model using a simulated cohort of individuals from age 0 to 9 years was developed. Parameters regarding the reported annual incidence of dengue, proportion of inapparent cases, and expansion factors for outpatient and hospitalized cases were considered as transition probabilities. The proportion of immune population at 9 years of age was taken as a proxy of the expected seroprevalence, considering this age as targeted for vaccination. The model was used to evaluate the expected seroprevalence in Misiones and Salta provinces and in Buenos Aires city, three settings showing different climatic favorability for dengue.

RESULTS

The estimates of the seroprevalence for the group of 9-year-old children for Misiones was 79% (95%CI:46-100%), and for Salta 22% (95%CI:14-30%), both located in northeastern and northwestern Argentina, respectively. Buenos Aires city, from central Argentina, showed a likely seroprevalence of 7% (95%CI: 3-11%). According to the deterministic sensitivity analyses, the parameter showing the highest influence on these results was the probability of inapparent cases.

CONCLUSIONS

This model allowed the estimation of dengue seroprevalence in settings where this information is not available. Particularly for Misiones, the expected seroprevalence was higher than 70% in a wide range of scenarios, thus in this province a vaccination strategy directed to seropositive children of >9 years should be analyzed, including further considerations as safety, cost-effectiveness, and budget impact.

Broad-spectrum agents for flaviviral infections: dengue, Zika and beyond

Infections with flaviviruses, such as dengue, West Nile virus and the recently re-emerging Zika virus, are an increasing and probably lasting global risk. This Review summarizes and comments on the opportunities for broad-spectrum agents that are active against multiple flaviviruses. Broad-spectrum activity is particularly desirable to prepare for the next flaviviral epidemic, which could emerge from as-yet unknown or neglected viruses. Potential molecular targets for broad-spectrum antiflaviviral compounds include viral proteins, such as the viral protease or polymerase, and host targets that are exploited by these viruses during entry and replication, including α-glucosidase and proteins involved in nucleoside biosynthesis. Numerous compounds with broad-spectrum antiviral activity have already been identified by target-specific or phenotypic assays. For other compounds, broad-spectrum activity can be anticipated because of their mode of action and molecular targets.