Epidemiological studies on dengue virus type 3 in Playa municipality, Havana, Cuba, 2001-2002.

OBJECTIVES: Recognizing the uniqueness of secondary dengue virus (DENV)-1/3 dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) cases at an interval of 24 years, we sought to estimate DENV infections as well as the ratios between mild disease and DHF/DSS by DENV infection sequence in Playa District (Havana, Cuba) during the 2001-2002 outbreak of dengue virus type 3 (DENV-3). METHODS: A retrospective seroepidemiological study was conducted in 2003 in Playa District. Blood samples were collected from a 1% random sample of residents and were studied for the prevalence of dengue neutralizing antibodies. RESULTS: DENV-3 was found to have infected 7.2% (95% confidence interval (95% CI) 6.0-8.4%) of susceptible individuals (the entire cohort), the majority of whom experienced silent infections. Virtually every individual who had a secondary infection in the sequence DENV-1 then DENV-3 became ill, with a ratio of severe to mild cases of 1:35 (95% CI 1:67-1:23). Secondary infections in the sequence DENV-2/3 were less pathogenic than DENV-1/3. Mild disease accompanying secondary DENV2/3 occurred at a ratio of 1:4.49 infections (95% CI 1:5.77-1:3.42) secondary infections. CONCLUSIONS: The results obtained highlight the role of the infecting serotype and also the sequence of the viral infection in the clinical outcome of a dengue infection.

Population structure of the dengue viruses, Aragua, Venezuela, 2006-2007. Insights into dengue evolution under hyperendemic transmission.

During the past three decades there has been a notable increase in dengue disease severity in Venezuela. Nevertheless, the population structure of the viruses being transmitted in this country is not well understood. Here, we present a molecular epidemiological study on dengue viruses (DENV) circulating in Aragua State, Venezuela during 2006-2007. Twenty-one DENV full-length genomes representing all of the four serotypes were amplified and sequenced directly from the serum samples. Notably, only DENV-2 was associated with severe disease. Phylogenetic trees constructed using Bayesian methods indicated that only one genotype was circulating for each serotype. However, extensive viral genetic diversity was found in DENV isolated from the same area during the same period, indicating significant in situ evolution since the introduction of these genotypes. Collectively, the results suggest that the non-structural (NS) proteins may play an important role in DENV evolution, particularly NS1, NS2A and NS4B proteins. The phylogenetic data provide evidence to suggest that multiple introductions of DENV have occurred from the Latin American region into Venezuela and vice versa. The implications of the significant viral genetic diversity generated during hyperendemic transmission, particularly in NS protein are discussed and considered in the context of future development and use of human monoclonal antibodies as antivirals and tetravalent vaccines.

Virus role during intraepidemic increase in dengue disease severity.

Dengue epidemics in Cuba have repeatedly demonstrated a month-to-month increase in clinical severity during secondary infections. The dengue 2 outbreak that occurred in Santiago de Cuba in 1997 was accompanied by the most severe intraepidemic increase in disease severity reported to date. It was initially proposed that the appearance of neutralization escape mutants during the course of the epidemic might explain this phenomenon. Recent studies have revealed that during the course of this epidemic, nucleotide substitutions appeared only in nonstructural (NS) genes, most of which were silent, except for one change in the NS1 gene. To study whether or not variation in the NS1 gene might be associated with increased disease severity during the epidemic, this gene was partially sequenced from 15 isolates obtained at different times during the 1997 epidemic. Early epidemic isolates differed from those obtained later by replacement only of threonine with serine at position 164 in the NS1 protein, an amino acid rarely found in any genotype of dengue 2 virus. All viruses isolated from patients located in Health Districts, where dengue 2 transmissions occurred late in the epidemic, contained Serine at position 164, indicating that this change was fixed within a few months. Here we argue that this single mutation contributes to viral survival or replication efficiency, resulting in enhanced infection in the presence of enhancing antibodies, a phenomenon that we term increased virus "fitness" in contrast to "virulence," an intrinsic property of the virus.

First report on fatal myocarditis associated with adenovirus infection in Cuba.

Myocarditis is caused frequently by viral infections of the myocardium. In the past, enteroviruses (EV) were considered the most common cause of myocarditis in all age groups. Other viruses that cause myocarditis are adenovirus and influenza viruses. Parvovirus B19 infection is associated sometimes with myocarditis. Members of the Herpesviridae family, cytomegalovirus (CMV), and human herpesvirus 6 (HHV-6) have been associated occasionally with myocarditis. During an atypical outbreak of acute febrile syndrome, eight children, with ages from 5 months to 15 years, died in cardiogenic shock due to myocarditis in July-August 2005, in the city of Havana, Cuba. Nested polymerase chain reaction (nPCR) and nested reverse transcription-PCR (nRT-PCR) were carried out on fresh heart muscle and lung tissue to analyze the genomic sequences of adenovirus, CMV, HHV-6, herpes simplex virus, Epstein-Barr virus (EBV), varizella zoster virus, influenza virus A, B, C, respiratory syncytial virus (RSV) A and B, parainfluenza viruses, rhinoviruses, coronavirus, flaviruses and enteroviruses. Evidence was for the presence of the adenovirus genome in 6 (75%) of the children. Phylogenetic analyses of a conserved hexon gene fragment in four cases showed serotype 5 as the causal agent. No others viruses were detected. Histological examination was undertaken to detect myocardial inflammation. After exclusion of other possible causes of death, the results indicated that viral myocarditis was the cause of death in patients with adenovirus infection.

A myocarditis outbreak with fatal cases associated with adenovirus subgenera C among children from Havana City in 2005.

BACKGROUND: Among multiple causes of acute myocarditis, viral infection, especially that due to enteroviruses and adenoviruses, is the leading cause. In the summer 2005 an outbreak of a febrile syndrome accompanied by acute cardiac decompensation occurred in infants and young children in Havana City. Eleven patients had a rapid evolution of disease and there were 8 fatalities from cardiac failure secondary to myocarditis. OBJECTIVE: The aim of the present study was to determine the etiological agent responsible for this outbreak. STUDY DESIGN: Children admitted to the pediatric hospitals of Havana City from July 3 to August 2 with this clinical presentation were studied. Forty samples of necropsy tissue, cerebrospinal fluid, stools and serum were tested by molecular methods for 14 respiratory viruses, 6 herpesviruses and generic enteroviruses and flavirus and alfaviruses. Viral isolation was performed in A-549 cells. Isolated viruses were typed by sequence analysis. RESULTS: Adenovirus genome was detected in 6 of the 8 fatal cases-the lungs in 5 (63%) and the myocardium in 3 (37%). In two fatal cases, viral genome was detected in both lung and myocardium. Adenovirus was isolated in five fatal cases. In all three non-fatal cases, adenovirus genome was detected and adenovirus was isolated into two. Sequence analysis showed that adenovirus type 5 was the only isolate from fatal cases and adenovirus 1 the only isolate in non-fatal cases. No other viruses were found by PCR or isolation techniques. CONCLUSION: Adenovirus was the etiologic agent implicated in this myocarditis outbreak and adenovirus type 5 was associated with fatal outcome.

Immunogenicity and protective efficacy of a recombinant fusion protein containing the domain III of the dengue 1 envelope protein in non-human primates.

Recombinant fusion proteins containing the aa 286-426 of the dengue envelope protein fused to P64k protein from Neisseria meningitidis have been previously reported. Particularly, the immunogenicity and protective capacity of the dengue 2 recombinant protein was demonstrated in Macaca fascicularis monkeys. Here we evaluate the recombinant fusion protein containing the domain III of the dengue 1 envelope protein (PD10) in non-human primates (M. fascicularis and rhesus monkeys) and compare the effect of aluminum hydroxide and Freund adjuvant on the immunity induced. The PD10 protein emulsified in Freund adjuvant was highly immunogenic in M. fascicularis and rhesus monkeys. Following dengue 1 virus challenge, animals immunized with PD10 in Freund adjuvant were protected from viremia. However, monkeys receiving PD10 in aluminum hydroxide developed a poor antibody response and were not protected from viral challenge. These preliminary experiments are encouraging. Other formulations or vaccine schedules are being studied in an attempt to find regimens that enhance immunological protection.

Niveles de óxido nítrico en monos Macacus irus inoculados con virus dengue / Serum nitric oxide in Macacus irus monkeys inoculated with dengue virus

Objetivo: partiendo de que los anticuerpos preexistentes en la infección secundaria por dengue suprimen la acción de moléculas con acciones antivirales como el óxido nítrico, se determinó el comportamiento de esa molécula en suero de monos Macacus irus inoculados con virus dengue 2 como infección primaria y en monos con una infección secuencial dengue 4-dengue2. Métodos: los niveles de óxido nítrico referidos como niveles de nitritos fueron detectados mediante la reacción de Griess. Resultados: los niveles máximos de óxido nítrico se detectaron en los animales que sufrieron una infección primaria a partir del séptimo día posinoculación, a diferencia de los monos con infección secundaria en que no se obtuvieron niveles mayores de 100 µM. Conclusiones: al parecer existe una asociación entre la infección secundaria y la inhibición de la producción del óxido nítrico.

Objective: To determine the action of nitric Oxide (NO) in serum samples of dengue 2 inoculated Macacus irus monkeys as primary infection and in dengue 4 -dengue 2 inoculated monkeys as secondary infection, taking into account that preexisting antibodies in secondary dengue infection elicit the action of antiviral molecules such as nitric oxide. Methods: NO levels referred as nitrite levels were detected by Griess colorimetric reaction. Results: The highest nitric oxide levels were detected in those animals with primary infection seven days after inoculation monkeys whereas those monkeys with secondary infection did not show NO levels over 100 µM. Conclusions: Our results suggest that there seems to be a relationship between secondary infection and NO production inhibition.

Niveles de óxido nítrico en monos Macacus irus inoculados con virus dengue / Serum nitric oxide in Macacus irus monkeys inoculated with dengue virus

Objetivo: partiendo de que los anticuerpos preexistentes en la infección secundaria por dengue suprimen la acción de moléculas con acciones antivirales como el óxido nítrico, se determinó el comportamiento de esa molécula en suero de monos Macacus irus inoculados con virus dengue 2 como infección primaria y en monos con una infección secuencial dengue 4-dengue2. Métodos: los niveles de óxido nítrico referidos como niveles de nitritos fueron detectados mediante la reacción de Griess. Resultados: los niveles máximos de óxido nítrico se detectaron en los animales que sufrieron una infección primaria a partir del séptimo día posinoculación, a diferencia de los monos con infección secundaria en que no se obtuvieron niveles mayores de 100 µM. Conclusiones: al parecer existe una asociación entre la infección secundaria y la inhibición de la producción del óxido nítrico(AU)

Objective: To determine the action of nitric Oxide (NO) in serum samples of dengue 2 inoculated Macacus irus monkeys as primary infection and in dengue 4 -dengue 2 inoculated monkeys as secondary infection, taking into account that preexisting antibodies in secondary dengue infection elicit the action of antiviral molecules such as nitric oxide. Methods: NO levels referred as nitrite levels were detected by Griess colorimetric reaction. Results: The highest nitric oxide levels were detected in those animals with primary infection seven days after inoculation monkeys whereas those monkeys with secondary infection did not show NO levels over 100 µM. Conclusions: Our results suggest that there seems to be a relationship between secondary infection and NO production inhibition(AU)

Primary and secondary infections of Macaca fascicularis monkeys with Asian and American genotypes of dengue virus 2

The goal of this study was to compare the immune response and the protection capacity induced by the dengue virus 2 (DENV-2) American and Asian genotypes in Macaca fascicularis monkeys. Animals were infected with American or Asian DENV-2 strains and challenged 1 year later with a DENV-2 Asian genotype strain. The viremia and monkey antibody levels were similar for the different strains after primary and secondary infection; however, the functionality of the antibody response was different. A limited viral replication was demonstrated after the secondary infection in all the monkeys. No virus was isolated in tissue culture, while reverse transcription-PCR showed a late positive reaction in four of five challenged monkeys. The immunoglobulin M response pattern and the detection of antibodies to specific proteins by Western blotting supported the protection data. Despite the demonstration of the protective effect after homologous challenge, a strong anamnestic antibody response was observed(AU)

Anamnestic antibody response after viral challenge in monkeys immunized with dengue 2 recombinant fusion proteins.

The suitability of dengue 2 envelope domain III recombinant fusion proteins [(fusion (PD5) and insertion (PD3) variants)] for inducing functional antibodies and a protective immune response in nonhuman primates has been reported. However, the evaluation of the antibody response after immunization did not correlate with the protection data as measured by viremia detection. Here, we characterized the anamnestic immune response after viral challenge in monkeys immunized with the dengue 2 recombinant proteins in an attempt to define correlates of protection useful for vaccine studies. Monkeys immunized with PD5 (most protected group) exhibited an earlier increase in the anti-DENV-2 IgM response after challenge compared to control animals. Hemagglutination-inhibiting (HAI) antibodies were increased significantly earlier in PD5-immunized animals compared to those immunized with PD3. The fully protected monkeys showed the earliest HAI antibody response. These results underline the usefulness of the anamnestic antibody response for supporting protection data. The induction of an early HAI and IgM antibody response after challenge suggest a protective role against dengue virus (DENV) infection in monkeys, supporting their use as correlates of protection in vaccine studies.

Primary and secondary infections of Macaca fascicularis monkeys with Asian and American genotypes of dengue virus 2.

The goal of this study was to compare the immune response and the protection capacity induced by the dengue virus 2 (DENV-2) American and Asian genotypes in Macaca fascicularis monkeys. Animals were infected with American or Asian DENV-2 strains and challenged 1 year later with a DENV-2 Asian genotype strain. The viremia and monkey antibody levels were similar for the different strains after primary and secondary infection; however, the functionality of the antibody response was different. A limited viral replication was demonstrated after the secondary infection in all the monkeys. No virus was isolated in tissue culture, while reverse transcription-PCR showed a late positive reaction in four of five challenged monkeys. The immunoglobulin M response pattern and the detection of antibodies to specific proteins by Western blotting supported the protection data. Despite the demonstration of the protective effect after homologous challenge, a strong anamnestic antibody response was observed.

Biological and Molecular Properties of Dengue 2 Strains Isolated during the DHF/DSS Cuban Epidemic, 1981.

To study some biological and molecular properties of nine DENV-2 strains isolated during the 1981 Cuban epidemic, temperature sensitivity, viral plaque size, the kinetic of virus replication in newborn mice inoculated by intracerebral route, the influence of pH medium on virus-cell attachment phase and the restriction enzyme pattern were studied. Strains were classified in two patterns according to temperature sensitivity, plaque size, and virus replication in mouse brain and cell culture and restriction enzymatic pattern the changes observed differentiate clearly the strains isolated at the beginning and at the end of the epidemic suggesting that viruses with different characteristics circulated.

Amino acid changes in the recombinant Dengue 3 Envelope domain III determine its antigenicity and immunogenicity in mice.

The immunogenicity of the Envelope fragment from amino acid 284 to 426 of Dengue viruses, obtained as fusion proteins with P64k in Escherichia coli, has been previously tested by our group. Here, we studied two fusion proteins with P64k carrying the Envelope fragment from two strains of Dengue 3: H87 prototype strain (PD9) and an isolate from the Nicaragua 1994 outbreak (PD18). Sequence comparison of the Dengue Envelope fragments showed four amino acid differences. Only PD18 reacted with human antisera and induced a higher functional immune response in mice than PD9. Moreover, mice immunized with PD18 were less susceptible to Dengue 3 administered intracerebrally than those immunized with PD9. The results reveal that not all sequences of the Dengue Envelope fragment, at least in the context of P64k, are antigenic and generate a functional immune response against the native virus. This finding has direct implications for the design of vaccines based on fragments of the Envelope protein.

A recombinant fusion protein containing the domain III of the dengue-2 envelope protein is immunogenic and protective in nonhuman primates.

We have previously reported the construction and evaluation in mice of recombinant fusion proteins formed by a fragment (aa 286-426) of the dengue envelope protein and the P64k protein from Neisseria meningitidis. In this work we describe the immunization of Macaca fascicularis monkeys with two variants of these proteins [PD3 (insertion variant) and PD5 (fusion variant)] corresponding to serotype 2. Four doses of the proteins adjuvated in Freund's adjuvant were administered and the kinetics of antibody induction was monitored by ELISA and neutralization tests. Monkeys receiving PD3 or PD5 developed functional antibodies (Abs) in a dose-dependent manner. Following challenge with 5 log PFU of wild type dengue-2 virus (DEN2), animals immunized with PD5 were protected from developing viremia. These results constitute a proof-of-concept demonstrating that a fragment of the dengue envelope protein, containing the domain III and produced as a recombinant fusion protein in Escherichia coli, induces functional and protective immunity in a nonhuman primate model.

Classical dengue hemorrhagic fever resulting from two dengue infections spaced 20 years or more apart: Havana, Dengue 3 epidemic, 2001-2002.

OBJECTIVE: To report the clinical, laboratory and sonographic findings in 76 adult cases of dengue hemorrhagic fever (DHF). PATIENTS AND METHODS: A dengue 3 epidemic occurred in Havana City from June 2001 to March 2002. 12,889 cases were reported, with 81 DHF cases. From this, 76 serologically confirmed cases were studied descriptively. RESULTS: Bronchial asthma and white race were important risk factors for the severe form of the disease. Fever (100%), headache (92.1%), myalgia (76.3%), arthralgia (73.7%) and retro-orbital pain (57.7%) were the most frequent general symptoms. Vomiting and abdominal pain were observed in 59.2% and 48.6% of cases, respectively. The most common bleeding site was the vagina (64%), followed by the skin (55.2%). Eighteen patients (23.6%) had shock syndrome. Laboratory findings included thrombocytopenia (100%), hemoconcentration (93.4%), an increase in liver enzymes (82.8%), and leukopenia (71%). Ultrasound detected thickening of the gallbladder wall in 35.1%, pleural effusion in 20.3%, and splenomegaly in 12.9% of cases. CONCLUSION: These findings contribute to a better understanding of the clinical aspects of DHF in adult patients due to the dengue 3 virus.

PCR detection of dengue virus using dried whole blood spotted on filter paper.

Whole blood dried onto filter paper constitutes a potentially useful material for molecular testing of viruses, including dengue. In order to assess the stability of viral RNA, we carried out dengue-RNA detection in whole blood infected with dengue virus that had been previously spotted onto filter paper. Filter papers were stored at room temperature, 4 and -70 degrees C and processed for PCR assay at intervals of 2, 4, 6 and 9 weeks. Our results demonstrated that dengue-RNA was stable in filter paper for 9 weeks at all tested temperatures. Furthermore, we evaluated these conditions using frozen sera and dried blood samples onto filter paper from 52 patients with confirmed clinical diagnosis of dengue infection. PCR results showed a 100% specificity and 93% sensitivity for dried blood samples. This storage method facilitates the transportation and analysis by nucleic acid amplification techniques even when freezing conditions are not available.

Role of the virology diagnosis laboratory in the surveillance of rubella virus Cuba 1988/2000.

In Cuba, on the basis of Measles Elimination Program, the incidence of this disease decline, and was necessary to test rubella virus as a possible etiology agent that produce fever and rash illness. To reach this goal, Cuba developed rubella elimination strategies with integrated epidemiologic and laboratory surveillance. In the country, the vaccination program against rubella started in 1982 by vaccinating 12-14 years old females, with a special surveillance program with laboratory study of all suspected cases. Through 1988-2000, the Serology Diagnosis Laboratory in the Virology Branch of Pedro Kouri Institute had the responsibility to do the measles and rubella surveillance and play a key roll in the elimination strategies of these diseases. For confirmation of all suspected cases, 8566 serum samples with the suspected diagnosis of measles or rubella from different provinces in Cuba were studied in the laboratory using different techniques as haemagglutination inhibition test (HIA), ultra micro analytic assay (UMA); and in 1995 by the newly introduced IgM ELISA, which was used taken only one sample in the acute phase of the disease. These techniques allowed knowing that the annual number of reported rubella cases in the country decreased substantially after the implementation, in 1986, of the second vaccine policy, that of vaccinating women of childbearing age. However, in 1989, was detected an outbreak of rubella virus infection that had occurred in young adults male 15-19 age groups in Matanzas' province. The last three indigenous cases of this disease were confirmed by our laboratory in 1995, after national vaccine coverage over 95%.

Dengue 3 epidemic, Havana, 2001.

In June 2001, dengue transmission was detected in Havana, Cuba; 12,889 cases were reported. Dengue 3, the etiologic agent of the epidemic, caused the dengue hemorrhagic fever only in adults, with 78 cases and 3 deaths. After intensive vector control efforts, no new cases have been detected.