Antibody-dependent enhancement of dengue 2 virus in people of white descent in Cuba

The innate immune response following multivalent dengue vaccination and implications for protection against dengue challenge

Understanding the immune response to dengue virus (DENV) is essential for developing a dengue vaccine that is protective against all 4 DENV serotypes. We evaluated the immune response after vaccination (live attenuated tetravalent dengue vaccine TV005 or trivalent admixture) and after challenge with DEN2Δ30 (Tonga/74) to better understand the importance of homotypic immunity in vaccine protection. Significant increases in IP-10 expression were observed following receipt of either the trivalent or tetravalent vaccine. After challenge, a large increase in IP-10 expression was observed in the placebo and trivalent admixture groups but not in the tetravalent vaccine group. MCP-1, IL-1RA, and MIP-1β exhibited a similar pattern as IP-10. These results demonstrate protective effects of trivalent and tetravalent vaccines against DENV and suggest that the tetravalent vaccine has a better protective effect compared with the trivalent admixture. We also explored the postvaccination and postchallenge immune response differences between Black and White participants. White participants responded to vaccine differently than Black participants; Black participants receiving trivalent and tetravalent vaccines responded strongly and White participants responded only transiently in trivalent group. In response to challenge, White participants elicited a stronger response than Black participants. These results may explain why White participants may have a more vigorous DENV immune response than Black participants, as reported in literature.

Unusual clinical manifestations of dengue disease - Real or imagined?

The disease caused by each of the four serotypes of dengue virus (DENV) have plagued humans since last century. Symptoms of dengue virus (DENV) infection range from asymptomatic to dengue fever (DF) to severe dengue disease (SDD). One third of the world's population lives in regions with active urban DENV transmission, and thousands of serologically naïve travelers visit these areas annually, making a significant portion of the human population at risk of being infected. Even though lifelong immunity to the homotypic serotype is achieved after a primary DENV infection. Heterotypic DENV infections may be exacerbated by a pre-existing immune memory to the primary infection and can result in an increased probability of severe disease. Not only, age, comorbidities and presence of antibodies transferred passively from dengue-immune mother to infants are considered risk factors to dengue severe forms. Plasma leakage and multiple organ impairment are well documented in the literature, affecting liver, lung, brain, muscle, and kidney. However, unusual manifestation, severe or not, have been reported and may require medical attention. This review will summarize and discuss the increasing reports of unusual manifestations in the clinical course of dengue infection.

Dengue expansion in Africa-not recognized or not happening?

Addressing this expansion is essential before control and prevention of dengue are implemented.

An expert conference on Dengue in Africa was held in Accra, Ghana, in February 2013 to consider key questions regarding the possible expansion of dengue in Africa. Four key action points were highlighted to advance our understanding of the epidemiology of dengue in Africa. First, dengue diagnostic tools must be made more widely available in the healthcare setting in Africa. Second, representative data need to be collected across Africa to uncover the true burden of dengue. Third, established networks should collaborate to produce these types of data. Fourth, policy needs to be informed so the necessary steps can be taken to provide dengue vector control and health services.

Extensive haemorrhagic necrosis of liver is an unpredictable fatal complication in dengue infection: a postmortem study

Background

Dengue infection carries a potential risk of death despite stringent management of plasma leak and haemorrhage. It appears that the extent of liver dysfunction determines the outcome.

Methods

We present a postmortem study of five patients, died of dengue shock syndrome who had markedly elevated liver enzymes and irreparable circulatory failure.

Results

All were females with a median age of 46 years (range 20–50 years). All had positive NS1 and IgM. Clinically, one patient developed severe degree of hepatic encephalopathy whilst three patients developed uncontrollable bleeding manifestations. Dengue virus was detected in three liver specimens by reverse transcription PCR. Histology of the liver revealed massive necrosis with haemorrhages in these patients with evidence of micro and macrovesicular steatosis with significant periportal inflammatory infiltrate. No significant ischaemic changes or necrosis was observed in the other organs.

Conclusions

Severe haemorrhagic necrosis of the liver was the cause of death in these patients probably due to direct viral infection. Predilection for severe liver disease remains unknown. Therefore, it is prudent to think beyond plasma leak as the main pathology of dengue infection and attempts should be made to develop other treatment modalities to prevent and manage unforeseen fatal complications of dengue infection.

Evaluation of an inactivated Ross River virus vaccine in active and passive mouse immunization models and establishment of a correlate of protection

Ross River Virus has caused reported outbreaks of epidemic polyarthritis, a chronic debilitating disease associated with significant long-term morbidity in Australia and the Pacific region since the 1920s. To address this public health concern, a formalin- and UV-inactivated whole virus vaccine grown in animal protein-free cell culture was developed and tested in preclinical studies to evaluate immunogenicity and efficacy in animal models. After active immunizations, the vaccine dose-dependently induced antibodies and protected adult mice from viremia and interferon α/β receptor knock-out (IFN-α/βR(-/-)) mice from death and disease. In passive transfer studies, administration of human vaccinee sera followed by RRV challenge protected adult mice from viremia and young mice from development of arthritic signs similar to human RRV-induced disease. Based on the good correlation between antibody titers in human sera and protection of animals, a correlate of protection was defined. This is of particular importance for the evaluation of the vaccine because of the comparatively low annual incidence of RRV disease, which renders a classical efficacy trial impractical. Antibody-dependent enhancement of infection, did not occur in mice even at low to undetectable concentrations of vaccine-induced antibodies. Also, RRV vaccine-induced antibodies were partially cross-protective against infection with a related alphavirus, Chikungunya virus, and did not enhance infection. Based on these findings, the inactivated RRV vaccine is expected to be efficacious and protect humans from RRV disease.

Fulminant hepatitis in dengue haemorrhagic fever

Dengue virus is estimated to cause over 100 million infections throughout the world annually. While dengue infections can have a wide range of infections, atypical manifestations have been described. These involve the central nervous system, cardiac alterations and hepatitis. Here, we highlight a case of dengue haemorrhagic fever (DHF) with fulminant hepatitis. A 55-year-old male was admitted for 16 days, developing severe thrombocytopenia as low as 6x10(9)/L, haematocrit of 48% with transaminitis: ALT: 3,515 U/L, AST: 12,541 U/L, GGT: 1,094 U/L. Subsequent investigations excluded any occult liver lesions, hepatitis A, B and C, Wilson's disease, Epstein-Barr virus and Cytomegalo virus as possible causes. His dengue PCR was positive. His condition subsequently improved with supportive treatment. Liver injury from dengue virus is mediated by its direct infection of hepatocytes and kupffer cells. While mild to moderate elevations of serum aminotransferases (ALT and AST<5X normal) are common in dengue virus infection, liver failure rarely dominate the clinical picture. Liver dysfunction was commoner in DHF, with case reports indicating that severe hepatic dysfunction (ALT and AST>10X normal) was seen with DHF associated with spontaneous bleeding tendencies. Overall prognosis depends on age and other concomitant co-morbidities. We seek to review the literature on dengue infections with hepatitis and discuss issues pertaining to pathophysiology of liver impairment in dengue, the frequency of transaminitis associated with DHF and the overall prognosis.

Race: a risk factor for dengue hemorrhagic fever

Cuban DHF/DSS outbreaks have provided evidence of a reduced risk of people of Negroid race for DHF/DSS compared to those of Caucasoid race. These observations from Cuban dengue outbreaks have significant epidemiological interest, as the differences in susceptibility to DHF/DSS among racial groups in Cuba coincide with that reported in African and Black Caribbean populations. In this article, we review the literature on race as a risk factor for DHF/DSS and discuss recent results from ongoing studies. Taking into consideration the origins of contemporary Cuban inhabitants, we propose that the Cuban, Caribbean Black and African populations share a common gene pool that could explain, at least partially, the low incidence of dengue hemorrhagic fever in Cuba and Caribbean and African countries. The central role played by immunological mechanisms in the pathogenesis of DHF/DSS has led us to consider that the polymorphic genes associated with the immune response must be carefully considered among those human genes regulating dengue disease severity that might be distributed unequally in Blacks and Whites.

Dengue and dengue haemorrhagic fever

The incidence and geographical distribution of dengue have greatly increased in recent years. Dengue is an acute mosquito-transmitted viral disease characterised by fever, headache, muscle and joint pains, rash, nausea, and vomiting. Some infections result in dengue haemorrhagic fever (DHF), a syndrome that in its most severe form can threaten the patient's life, primarily through increased vascular permeability and shock. The case fatality rate in patients with dengue shock syndrome can be as high as 44%. For decades, two distinct hypotheses to explain the mechanism of DHF have been debated-secondary infection or viral virulence. However, a combination of both now seems to be the plausible explanation. The geographical expansion of DHF presents the need for well-documented clinical, epidemiological, and virological descriptions of the syndrome in the Americas. Biological and social research are essential to develop effective mosquito control, medications to reduce capillary leakage, and a safe tetravalent vaccine.

Dengue: A Literature Review and Case Study of Travelers from the United States, 1986-1994

Dengue fever is an acute, mosquito-transmitted viral disease characterized by fever, headache, arthralgia, myalgia, rash, nausea, and vomiting. Infections are caused by any of four virus serotypes (DEN-1, DEN-2, DEN-3, and DEN-4). The incidence of dengue is increasing in most tropical areas throughout the world (Fig. 1). Although dengue is not endemic in the continental United States, Hawaii, or Alaska, more than 500 laboratory-positive cases of introduced dengue were reported from 1977 through 1994 in U.S. residents who visited dengue-endemic areas throughout the world.1-4 In addition, two competent mosquito vectors (Aedes aegypti and Aedes albopictus) are found in the southeastern United States, and both could possibly transmit an introduced virus. In Hawaii, Ae. albopictus is the dominant mosquito on all islands; Ae. aegypti has only focal distribution on Molokai and the Kona coast of Hawaii. Economic, political, technologic, ecologic, and demographic changes have brought about the emergence of new microbial diseases, as well as an increase in the incidence of previously known infections. The increase in dengue activity in Asia, Africa, and the Americas represents a pandemic that is being facilitated by increased air travel; global urbanization; population growth; greater abundance of disposable, nondegradable containers that can serve as Aedes production sites; and lack of effective mosquito control programs.5,6 This report summarizes information about risk factors for severe disease, recent dengue outbreaks throughout the world, and cases of dengue virus infection in travelers who have been diagnosed on return to the United States.

Dengue haemorrhagic fever and dengue shock syndrome: are they tumour necrosis factor-mediated disorders?

A consecutive series of 24 patients with clinical features of primary dengue infection and 22 controls (14 patients with viral fever of unknown origin and 8 healthy subjects) were assayed for serum levels of tumour necrosis factor (TNF). The acute sera of the 24 patients with clinical dengue infection were positive for dengue virus-specific IgM antibody. Clinically, 8 had dengue fever (DF), 14 dengue haemorrhagic fever (DHF) and 2 dengue shock syndrome (DSS). All 16 patients with DHF/DSS had significantly elevated serum TNF levels but the 8 DF patients had TNF levels equivalent to that in the 22 controls. A case is made for augmented TNF production having a role for the pathophysiological changes observed in DHF/DSS and mediator modulation as a possible therapeutic approach to treatment.