Cuban dengue vaccine is in preclinical studies

Darwin imagined. We impose on natural selection, we focus on the survival of the poor. Manipulate genes and proteins. Human intervention on laws of nature mark milestones in a path in which, increasingly, technology, socialized, replaces random. The famous English scientist discovered by evolutionary mechanism is modified under the influence of devices that change the "fate" of the "chosen" to perish.

Vaccines are one of these. Major epidemics have been controlled with your application, even long before the birth of genetic engineering and biotechnology. But microorganisms also continue to evolve and adapt to new conditions. Survival is the essence of life challenge. That cross kicks the struggle between the two universes, the molecules and cells and organisms. Thus, as the dengue virus have been able to take advantage.

Widespread in tropical ecosystems overflowing borders, this pathogen causes disease from human contact with one or more of its four serotypes (1, 2, 3 and 4) at different time spaces. Each infection with one of them is unique, but if after months or years (even 20), the person comes in contact with another is able to develop the most dangerous form of evil.
So a second infection has been associated with severe disease of the call (or hemorrhagic) dengue. Its ability to cause death within hours has been the trigger for alarm and subsequent call to prevent transmission of the virus among humans by Aedes aegypti and Aedes albopictus mosquitoes. On the table then follows the need for a tetravalent immunogen capable of immunizing against all four serotypes of dengue.

But this quest has passed with difficulties, not least because there is no ideal to evaluate vaccine candidates animal model, plus a tetravalent formulation that achieves lasting protection against all four serotypes should be obtained. And it must be so, -says Dr. Maria Guadalupe Guzman, head of the Department of Virology, Institute of Tropical Medicine Pedro Kouri (IPK) -, because otherwise the same vaccine could result in the immunized called immunoamplification effect.
"When this phenomenon occurs, the first antibody binds to the second infection and facilitates virus entry into cells, so that many of these are infected and viremia is greater. This process leads to vascular permeability (the capillaries open and fluid out) and, therefore, we are witnessing the development of severe or hemorrhagic form, "said Guzman, who has devoted his scientific career to the study of dengue.

The Cuban candidate

Currently exist in the world several immunogens against dengue virus, in the process of preclinical and clinical development. In this last phase the Cuban vaccine (recombinant subunit) *, derived from a national joint project between IPK and the Center for Genetic Engineering and Biotechnology (ICGEB) is.

According Alyenis Izquierdo, Master in Virology and head of the Laboratory of Dengue Vaccine IPK, for the construction of vaccine researchers have focused on a region of the envelope protein of the virus, specifically in the domain III, a region identified as inducing neutralizing immune response and also has ** serotype specificity.

"It means that if immunized with domain III of dengue 1 virus should be obtained antibody response rather specific serotype 1 (and equal to each), which could reduce the risk that the person will develop the phenomenon of immunoamplification when suffering from an infection by a heterologous serotype. "

Early studies by the Cuban group consisted of domain III fused to a carrier protein (p64k) obtained in the IGBC to make more immunogenic in that region of the virus.

Thus investigations with monovalent formulations (each of the serotypes), first in mice and monkeys then started. He even came to the tetravalent formulation, but with this candidate down the levels of protection when mixed with the adjuvant for humans. There was then a change in strategy.

"Substituting the carrier protein (P64k) that has been used before for virus capsid (very potent inducer of cellular response) and merge with each domain III of dengue serotypes (1, 2, 3, 4) . So, domain III-capsid virus 1 virus capsid domain III-2 virus capsid domain III-3 and III-capsid domain virus 4 ".
Of each of these monovalent formulations have been made in the murine model evaluations known. The results? "Very good levels of immunogenicity and protective response (cellular and antibody) from about 90 percent, even with adjuvant for human incorporated. Right now we are in phase assay analysis with tetravalent in mice. "

Moreover, refers Dr. Guzman, are already made constructions tetravalent prepared for testing in non-human primates which is the next stage to work with mice and prior to study in humans. "Now is transitioning this future work with monkeys. "

"Previously evaluated in this primate the domain III-dengue 2 and worked formulation" says Alyenis. "There were humoral, cellular secretion of gamma interferon and protection. The monkeys were immunized and then challenged with the normal strain of dengue-2 were protected. "

Ensures Dr. Guzman, also director of Dengue Collaborating Center of the World Health Organization, this strategy of combining the domain III and capsid dengue vaccine, is originally from Cuba and "only we are developing a preparation with this structure ".
The latest proposal

After numerous phase III studies (to measure effectiveness) Sanofi Pasteur, the vaccines division of the multinational French pharmaceutical Sanofi-Aventis, the world's third largest, has at present the most advanced immunizing candidate against dengue.

Tetravalent prepared is based on the skeleton of the yellow fever vaccine and the insertion in some of its genetic dengue gene (the envelope proteins and the viral membrane) areas.

A first study in humans with this immunogen, reported in late 2012 in the Lancet, covered about four thousand Thai children. The efficacy of the vaccine was low: 35 percent for dengue 2 and about 60 to 70 percent for the other three serotypes.

"This was an unexpected shock," says Dr. Guzman. However, "more recent studies in several countries (Vietnam, Mexico, Colombia, Puerto Rico) show improved protection indicators of this vaccine (66 percent), although dengue II remain low."

But even if it is implemented, we must have the production capacity has disclosed the French pharmaceutical firm: "hundred million vaccines". However, two thousand 500 million people worldwide are at risk of being infected with dengue virus, as published by WHO in its World Health Statistics 2014.

Other tetravalent dengue vaccines undergoing clinical trials are Inviragen and NIH (National Institute of Health), US, and a recombinant that have developed in Hawaii. The first is originally from the University of Thailand; is based on an attenuated dengue virus II to that sheath and removed and put the membrane 3. Thus with the four combinations. Inviragen made genetic constructs and graduated. The NIH also has a candidate attenuated by molecular biology and Hawaiian is a recombinant vaccine based on the virus envelope.
The team of the Department of Virology of the IPK has starred in major advances in the understanding of dengue worldwide. Among them, epidemiological and virological observations made in Cuba, have concluded that individuals europoide descent are at greater risk of developing DHF. We have seen Dr. Guzman explains that there are links between ethnicity of the individual and the group of genes associated with susceptibility or resistance to suffer the severe form of the disease.

Another element that the group appreciates linked to the severity of epidemics, in terms of hemorrhagic cases against total cases, has to do with the changes that the virus undergoes in those episodes. This analysis will be complemented with studies of quasi-species or population of viral particles of the same serotype, but different, accompanying the infectious process. "Its scope in the clinical evolution is part of an international collaborative project that we are developing with the Pasteur Institute."

To the extent that dengue has been gaining more space on a global scale has been perceived that the disease is being associated with organ damage (myocarditis, encephalitis, hepatitis, neurologic manifestations). In this sense, the team headed by Dr. Guzman has done pioneering research of follow people who suffered two ways in which the pathology is presented.

The first job lasted six months and found that some of the participants held symptomatology always associated with dengue (fatigue, irritability, joint pain). A second investigation covered a period of two years and included the practice of some immune markers in addition to the clinical evaluation of the patient. According to this poll, he explains there seems to be a phenomenon of autoimmunity leading to maintain over time a certain symptoms, most often in women. Now we have another such study in progress, together with the Salvador Allende Hospital.

Systematic scientific work led by IPK in Cuba also resulted in the reclassification in 2009-2010 accepted by WHO for this disease: dengue and severe dengue (the former is dengue and DHF).

Cuba played a leading role in this change that conceptualizes better patient management and identification of when a case can evolve to gravity, says Dr. Guzman. "Warning signs (persistent vomiting, abdominal pain or long decay) of severe forms alert the clinician that person has to be entered, when the body becomes hydrated and kept under strict surveillance."

* The recombinant proteins are obtained from a different cell to the original cell line.

** In the presence of neutralizing antibodies must be protection.

From: http://www.cubadebate.cu