Blood group AB is associated with increased risk for severe dengue disease in secondary infections

Lack of association of ABO and RhD blood groups with COVID-19 mortality: A 2-center cross-sectional study in Saudi Arabia

Several diseases, including both noninfectious diseases and bacterial and viral diseases, are associated with the ABO and RH blood group systems. Previous studies have shown a link between blood type and the probability of coronavirus disease 2019 (COVID-19) infection. In this study, we aimed to explore the correlation between deaths caused by COVID-19 and ABO and RhD blood types in Saudi Arabia. In this cross-sectional observational study, data from COVID-19 patients were collected from 2 major hospitals treating COVID-19 in Riyadh City, Saudi Arabia, between March 2020 and November 2021. The association between ABO and RhD blood types and COVID-19 outcomes was investigated. A total of 2302 real-time polymerase chain reaction-confirmed COVID-19 patients were enrolled in this study; a chi-square test was used to determine the statistical significance of the data. Of the 2302 enrolled patients, 1008 (43.8%) had blood type O, 677 (29.41%) had blood type A, 502 (21.8%) had blood type B, and 115 (5%) had blood type AB. Of the patients, 2143 (93.1%) were RhD-positive. The O-positive blood type had the highest mortality rate among COVID-19-infected patients, whereas the AB-negative type had the lowest. However, statistical analysis revealed no significant correlation between blood type (ABO or RhD) and COVID-19-based susceptibility or mortality. In conclusion, we found no association between ABO and RhD blood types and either susceptibility to or mortality due to COVID-19 in Saudi Arabia.

Relationship between blood group (ABO) and risk of COVID-19 infection in a patient cohort in Tehran, Iran

Background and purpose. Coronavirus (COVID-19) is a contagious disease causing severe acute respiratory syndrome which had a catastrophic effect on the world population and resulted in more than 2.9 million deaths worldwide. Epidemiological investigations have recently announced blood type has an association with the incidence of COVID-19 infection. Consequently, research in this regard can be effective in determining a person's susceptibility to a viral infection. Therefore, we investigated the relationship between blood types and the risk of COVID-19 in patients admitted to Khorshid laboratory, Tehran, Iran. Materials and methods. From January to March 2020, 50 nasal and throat swapb samples of patients' secretions were obtained from patients who were admitted to Khorshid laboratory. They were confirmed to have COVID-19 virus RNA and real-time polymerase chain reaction (PCR)-ABI, and their blood type was determined simultaneously. After collecting data to determine the relationship between COVID-19 infection and blood type, a confidence interval of 90 % was considered using SPSS 16. Results. The mean age of the patients was measured at 38.4±6.3 years. According to PCR results, 100 % of the subjects with COVID-19 showed blood type A. In addition, the ratio of blood type A to the percentage of reference type O was higher (P=0.009). Conclusion. There was a significant relationship between ABO blood type and susceptibility to COVID-19. As the current study suggests, those with blood type A are at a higher COVID-19 infection risk than those with blood type O.

ABO blood groups and the risk of SARS-CoV-2 infection

There is no doubt that genetic factors of the host play a role in susceptibility to infectious diseases. An association between ABO blood groups and SARS-CoV-2 infection as well as the severity of COVID-19 has been suggested relatively early during the pandemic and gained enormously high public interest. It was postulated that blood group A predisposes to a higher risk of infection as well as to a much higher risk of severe respiratory disease and that people with blood group O are less frequently and less severely affected by the disease. However, as to the severity of COVID-19, a thorough summary of the existing literature does not support these assumptions in general. Accordingly, at this time, there is no reason to suppose that knowledge of a patient's ABO phenotype should directly influence therapeutical decisions in any way. On the other hand, there are many data available supporting an association between the ABO blood groups and the risk of contracting SARS-CoV-2. To explain this association, several interactions between the virus and the host cell membrane have been proposed which will be discussed here.

Host Genetic Risk Factors Associated with COVID-19 Susceptibility and Severity in Vietnamese

Since the emergence and rapid transmission of SARS-CoV-2, numerous scientific reports have searched for the association of host genetic variants with COVID-19, but the data are mostly acquired from Europe. In the current work, we explored the link between host genes (SARS-CoV-2 entry and immune system related to COVID-19 sensitivity/severity) and ABO blood types with COVID-19 from whole-exome data of 200 COVID-19 patients and 100 controls in Vietnam. The O blood type was found to be a protective factor that weakens the worst outcomes of infected individuals. For SARS-CoV-2 susceptibility, rs2229207 (TC genotype, allele C) and rs17860118 (allele T) of IFNAR2 increased the risk of infection, but rs139940581 (CT genotype, allele T) of SLC6A20 reduced virus sensitivity. For COVID-19 progress, the frequencies of rs4622692 (TG genotype) and rs1048610 (TC genotype) of ADAM17 were significantly higher in the moderate group than in the severe/fatal group. The variant rs12329760 (AA genotype) of TMPRSS2 was significantly associated with asymptomatic/mild symptoms. Additionally, rs2304255 (CT genotype, allele T) of TYK2 and rs2277735 (AG genotype) of DPP9 were associated with severe/fatal outcomes. Studies on different populations will give better insights into the pathogenesis, which is ethnic-dependent, and thus decipher the genetic factor's contribution to mechanisms that predispose people to being more vulnerable to COVID-19.

Screening for Arboviruses in Healthy Blood Donors: Experience from Karachi, Pakistan (Jul-Dec 2018)

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DENV, WNV and JEV status was investigated in healthy blood donors at the Aga Khan University July to December 2018.

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ELISA for IgM antibodies and RT-PCR for viral RNA detection were performed.

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IgM antibodies for DENV and WNV were positive in 3.9% and JEV in 0.28% of the blood donors.

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Blood donors aged 19 and 30 years and residents of urban areas, of Karachi City were most frequent.

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DENV and WNV seropositivity were significantly associated with residence in Malir District of Karachi.

A Population of CD4+CD8+ Double-Positive T Cells Associated with Risk of Plasma Leakage in Dengue Viral Infection

According to the WHO 2009 classification, dengue with warning signs is at the risk of developing severe form of dengue disease. One of the most important warning signs is plasma leakage, which can be a serious complication associated with higher morbidity and mortality. We report that the frequency of CD4+CD8+ double-positive (DP) T cells is significantly increased in patients at risk of developing plasma leakage. Transcriptomic analysis demonstrated that CD4+CD8+ DP cells were distinct from CD4+ Single Positive (SP) T cells but co-clustered with CD8+ SP cells, indicating a largely similar transcriptional profile. Twenty significant differentially expressed (DE) genes were identified between CD4+CD8+ DP and CD8+ SP cells. These genes encode OX40 and CCR4 proteins as well as other molecules associated with cell signaling on the cell surface (NT5E, MXRA8, and PTPRK). While comparing the profile of gene expression in CD4+CD8+ DP cells from patients with and without warning signs of plasma leakage, similar expression profile was observed, implying a role of CD4+CD8+ DP cells in plasma leakage through a quantitative increase rather than functional alteration. This study provided novel insight into the host immune response during the acute febrile phase of DENV infection and the role of CD4+CD8+ DP T cells in the pathogenesis of plasma leakage.

The association of ABO blood group with the asymptomatic COVID-19 cases in India

The COVID-19 pandemic resulted in multiple waves of infection worldwide. The large variations in case fatality rate among different geographical regions suggest that the human susceptibility against this virus varies substantially. Several studies from different parts of the world showed a significant association of ABO blood group and COVID-19 susceptibility. It was demonstrated that individuals with blood group O are at the lower risk of coronavirus infection. To establish the association of ABO blood group in SARS-CoV-2 susceptibility, we for the first time analysed SARS-CoV-2 neutralising antibodies among 509 individuals, collected from three major districts of Eastern Uttar Pradesh region of India. Interestingly, we found neutralising antibodies in a significantly higher percentage of people with blood group AB (0.36) followed by B (0.31), A (0.22) and lowest in people with blood group O (0.11). We further estimated that people with blood group AB are at comparatively higher risk of infection than other blood groups. Thus, among the asymptomatic SARS-CoV-2 recovered people blood group AB has highest, whilst individuals with blood group O has lowest risk of infection.

ABO and Rhesus Blood Groups in Acute Puumala Hantavirus Infection

Puumala hantavirus (PUUV) causes hemorrhagic fever with renal syndrome. We aimed to evaluate whether ABO and rhesus blood groups associate with the susceptibility or the severity of PUUV infection. We analyzed blood groups in 289 adult patients treated in Tampere University hospital due to PUUV infection during the years 1982–2017. Patients’ blood group distribution was compared to that of healthy, voluntary blood donors living in the Tampere University Hospital responsibility area (n = 21,833). The severity of PUUV infection, as judged by the severity of acute kidney injury (AKI), thrombocytopenia, inflammation, capillary leakage, and the length of hospital care, was analyzed across the groups. The ABO and rhesus blood group distributions did not differ between the patients and blood donors. Patients with non-O blood groups had lower systolic blood pressure compared to patients with blood group O, but there was no difference in other markers of capillary leakage or in the severity of AKI. Minor deviations in the number of platelets and leukocytes were detected between the O and non-O blood groups. To conclude, patients with blood group O may be less susceptible to hypotension, but otherwise blood groups have no major influences on disease susceptibility or severity during acute PUUV infection.

Impact of ABO and Rhesus blood groups on COVID-19 susceptibility and severity: A case-control study

Early evidence from China suggested that blood groups may be involved in susceptibility to COVID‐19. Several subsequent studies reported controversial results. We conducted a retrospective matched case‐control study that aims to investigate the association between blood groups and the risk and/or severity of COVID‐19. We compared the blood groups distribution of 474 patients admitted to the hospital for COVID‐19 between March 2020 and March 2021, to that of a positive control group of outpatients infected with COVID‐19 and matched them for sex and age, as well as to the distribution in the general population. Three hundred and eighteen HC+ pairs with available blood group information were matched. The proportion of group A Rh+ in hospitalized patients (HC+) was 39.9% (CI 35.2%–44.7%), compared to 44.8% (CI 39.8%–49.9%) and 32.3% in the positive outpatient controls (C+) and the general population (C−), respectively. Both COVID‐19‐positive groups (HC+ and C+) had significantly higher proportions of group A Rh+ compared to the general population (p = 0.0019 and p < 0.001, respectively), indicating that group A Rh+ increases susceptibility to COVID‐19. Although blood group A Rh+ was more frequent in the outpatients C+ compared to the hospitalized group HC+, the association did not reach statistical significance, indicating that blood group A Rh+ is not associated with severity. There was no significant relationship between COVID‐19 and other blood groups. Our findings indicate that blood group A Rh+ increases the susceptibility for COVID‐19 but is not associated with higher disease severity.

Clinical spectrum and predictors of severity of dengue among children in 2019 outbreak: a multicenter hospital-based study in Bangladesh

BACKGROUND

The mosquito-borne arboviral disease dengue has become a global public health concern. However, very few studies have reported atypical clinical features of dengue among children. Because an understanding of various spectrums of presentation of dengue is necessary for timely diagnosis and management, we aimed to document the typical and atypical clinical features along with predictors of severity among children with dengue during the largest outbreak in Bangladesh in 2019.

METHODS

We conducted a cross-sectional study between August 15 and September 30, 2019. in eight tertiary level hospitals in Dhaka city. Children (aged < 15 years) with serologically confirmed dengue were conveniently selected for data collection through a structured questionnaire. Descriptive, inferential statistics, and multivariable logistic regression were used to analyze data.

RESULTS

Among the 190 children (mean age 8.8 years, and male-female ratio 1.22:1) included in the analysis, respectively 71.1 and 28.9% children had non-severe and severe dengue. All children had fever with an average temperature of 103.3 ± 1.2 F (SD). Gastrointestinal symptoms were the most common associated feature, including mostly vomiting (80.4%), decreased appetite (79.5%), constipation (72.7%), and abdominal pain (64.9%). Mouth sore, a less reported feature besides constipation, was present in 28.3% of children. Atypical clinical features were mostly neurological, with confusion (21.3%) being the predominant symptom. Frequent laboratory abnormalities were thrombocytopenia (87.2%), leucopenia (40.4%), and increased hematocrit (13.4%). Age (AOR 0.86, 95%CI 0.75-0.98, p = 0.023), mouth sore (AOR 2.69, 95%CI 1.06-6.96, p = 0.038) and a decreased platelet count (< 50,000/mm3) with increased hematocrit (> 20%) (AOR 4.94, 95%CI 1.48-17.31, p = 0.01) were significant predictors of severity.

CONCLUSIONS

Dengue in children was characterized by a high severity, predominance of gastrointestinal symptoms, and atypical neurological presentations. Younger age, mouth sores, and a decreased platelet with increased hematocrit were significant predictors of severity. Our findings would contribute to the clinical management of dengue in children.

Plasma leakage in dengue: a systematic review of prospective observational studies

Plasma leakage is a precursor to life-threatening complications of dengue, but this group is poorly defined and not often reported in literature. Patients with Dengue haemorrhagic fever (DHF) as defined in the 1997 World Health Organization classification are often reported, and they all have plasma leakage, but some patients with plasma leakage do not meet the definition of DHF. The study aims to estimate the frequency of plasma leakage and DHF (as a surrogate of plasma leakage) in dengue and its variations based on virus serotype, geography, patient gender and pre-existing immunity to dengue. PUBMED, Scopus, EMBASE, CINAHL and Web of Science were searched for prospective observational studies reporting on plasma leakage or DHF. Quality of data was assessed using the NIH quality assessment tool for cohort studies. Forty-three studies that recruited 15,794 confirmed dengue patients were eligible. Cumulative frequency of plasma leakage was 36.8% (15 studies, 1642/4462, 95% CI 35.4-38.2%), but surprisingly the estimated cumulative frequency of DHF was higher (45.7%, 32 studies, 4758/10417, 95% CI 44.7-46.6%), indicating that current medical literature over-reports DHF or under-reports plasma leakage. Therefore, a reliable estimate for the proportion of dengue patients developing plasma leakage cannot be derived from existing medical literature even after applying rigorous inclusion criteria to select homogenous studies. Plasma leakage is an important marker of "at-risk" dengue patients and standardizing its definition, diagnosis and reporting should be a priority in research and global policy.

COVID-19 and blood groups: A six-months observational study in Ferrara, Italy

The current literature still gives a little information about the relationships between the ABO blood group system and the immune response to the virus or the different disease outcomes. Hypothesizing the presence of a predisposition by some blood groups to COVID-19, we searched for differences between patients towards the different outcomes of disease.We enrolled 330 inpatients with a diagnosis of COVID-19, determining both their ABO blood group system and Rh factor, collecting demographic, clinical and laboratory data. We searched for relationships with COVID-19 outcomes within an observation period of 180 days (Intensification of Care - IoC, Inhospital death, 180-days mortality). The most frequent ABO blood group was A (45.8%); a minor part was represented by group O (38.8%), B (11.5%), AB (3.9%). As for the Rh factor, 86.7% of patients were Rh-positive. There were no significant differences between blood groups and Rh factors as for age, length of hospital stays (LoS), or Charlson Comorbidity Index (CCI), nor we found significant relationships between the ABO groups and COVID-19 outcomes. A significant relation was found between AB group and IoC (p=0.03) while as for the Rh factor, the patients with Rh factor positive died with less frequency during the stay (p=0.03). Cox regression analyses showed substantial differences in the survival functions concerning the Rh factors. The Rh factor seems to be involved in the 180-day prognosis. The survival functions of patients with Rh factor positive show, in fact, significantly better curves when compared to those with Rh factor negative.

Potential association of COVID-19 and ABO blood group: An Indian study

Coronavirus disease 2019 (COVID-19) transmits from person to person mainly through respiratory droplets and coughing. Infection severity ranges from asymptomatic and mild infection to those with moderate and severe symptoms which may lead to multiple organ failure and mortality. Infection severity largely depends on individual's immune response, age and co-morbidities. Present study categorized COVID-19 infected patients based on their infection severity and linked COVID-19 severity with age, gender and ABO blood group types. Clinical details of 383 COVID-19 patients were collected from Rajiv Gandhi Super Specialty hospital (RGSSH), India; divided into three groups; mild, moderate and severe patients, based on their symptoms. Present analysis revealed that age plays major role in infection severity, as the symptoms are more severe in patients above 45 years. Infection rate was higher in males compared to females. Most patients with A(+ve) and B(+ve) blood group were severely affected compared to those of blood group type O(+ve) and AB(+ve). O(+ve) blood group was least represented in severe patients. Present findings could be helpful in generating awareness amongst the population regarding susceptibility towards the COVID-19 infection. This supportive information would help clinicians and health workers to propose new strategies and tactical solution against COVID-19 infection.

Dengue and the Lectin Pathway of the Complement System

Dengue is a mosquito-borne viral disease causing significant health and economic burdens globally. The dengue virus (DENV) comprises four serotypes (DENV1-4). Usually, the primary infection is asymptomatic or causes mild dengue fever (DF), while secondary infections with a different serotype increase the risk of severe dengue disease (dengue hemorrhagic fever, DHF). Complement system activation induces inflammation and tissue injury, contributing to disease pathogenesis. However, in asymptomatic or primary infections, protective immunity largely results from the complement system’s lectin pathway (LP), which is activated through foreign glycan recognition. Differences in N-glycans displayed on the DENV envelope membrane influence the lectin pattern recognition receptor (PRR) binding efficiency. The important PRR, mannan binding lectin (MBL), mediates DENV neutralization through (1) a complement activation-independent mechanism via direct MBL glycan recognition, thereby inhibiting DENV attachment to host target cells, or (2) a complement activation-dependent mechanism following the attachment of complement opsonins C3b and C4b to virion surfaces. The serum concentrations of lectin PRRs and their polymorphisms influence these LP activities. Conversely, to escape the LP attack and enhance the infectivity, DENV utilizes the secreted form of nonstructural protein 1 (sNS1) to counteract the MBL effects, thereby increasing viral survival and dissemination.

An Unknown Risk Factor for Sepsis in Very Low Birth Weight Preterms: ABO Blood Groups (BGaPS Study)

OBJECTIVE

There is insufficient study of the association of blood groups with neonatal diseases. The aim of this study was to evaluate the blood groups associated with sepsis and blood groups in preterm infants.

STUDY DESIGN

This retrospective study was conducted between January 1, 2010 and November 31, 2018 in the neonatal intensive care unit (NICU). This study was done in single-center tertiary NICU. Infants born at gestational age (GA) <32 weeks with birth weight (BW) <1,500 g were included in the study.

RESULTS

A total of 2,548 infants were included. The culture-proven sepsis ratio (30.2%) was the lowest in the O blood group and the highest in the AB blood group (37.5%) (p = 0.045). Meningitis ratio (6.5%) was significantly higher, and hospital stay (64.1 ± 33.9 days) was significantly longer in B blood group (respectively, p = 0.005, p < 0.001). In the AB blood group, GA (27.68 ± 1.12 weeks) was the lowest and early onset sepsis (EOS) (40.1%) and mortality (28.9%) ratio were found to be statistically higher (p < 0.001 for all groups). The AB group was significantly related to higher frequency of EOS (odds ratio [OR] = 2.93, 95% confidence interval [CI] = 1.68-5.12, p = 0.000), in addition to mortality (OR = 1.1, 95% CI = 0.55-2.19, p = 0.001). The O group was found to be associated with lower risk of late onset sepsis (LOS) (OR = 1.67, 95% CI = 1.06-3.058, p = 0.003) according to the model with corrected risk factor including GA, BW, and time of hospitalization.

CONCLUSION

Our study was the first study showing a relationship between certain blood groups and EOS/LOS in premature infants as well as meningitis.

Association of Blood Subgroups With PCR Test Positivity and Lung Involvement in Patients With COVID-19

Objective The goal of this study was to investigate whether blood group type caused susceptibility to COVID-19 infection. Methods Two hundred and eleven consecutive patients admitted with various symptoms associated with COVID-19 were included. We compared the AB0 and Rh subgroup distributions between patients with a positive polymerase chain reaction (PCR) test result and the patients without. We compared the AB0 and Rh subgroup distributions between patients with lung involvement and patients without. Additionally, comparisons were performed between the patients both with positive PCR result and lung involvement, and the patients with a negative PCR result. Results No significant difference of ABO and Rh subgroup distributions was evident between patients with and without a positive PCR test result (p=0.632 and p=0.962). No significant difference of ABO and Rh subgroup distributions was evident between the patients with and without lung involvement (p=0.097 and p=0.797). No significant difference of ABO and Rh subgroup distributions was evident among patients both with PCR positivity and lung involvement, patients with only PCR positivity, and the patients with negative PCR test results (p=0.3 and p=0.993). Conclusion All blood group types seem to have an equal risk of COVID-19 infection. Everyone should follow the precautions to avoid the COVID-19 infection.

Relationship between ABO blood group distribution and clinical characteristics in patients with COVID-19

OBJECTIVE

To explore ABO blood group distribution and clinical characteristics in patients with COVID-19.

METHODS

The clinical data of 187 patients with COVID-19 seen between January 20, 2020 and March 5, 2020 at the First Hospital of Changsha were retrospectively analyzed. The differences in the ABO blood group distribution between COVID-19 patients and the control group (1991 cases) were analyzed. The relationship between blood type and clinical characteristics was analyzed.

RESULTS

Of the 187 patients with COVID-19, 69 had type A (36.90%), 63 had type B (33.69%), 41 had type O (21.92%), and 14 had type AB blood (7.49%). The proportion of patients with type A blood in the COVID-19 group was significantly higher than that in the control group (36.90% vs. 27.47%, P = 0.006), while the proportion of patients with type O blood in the COVID-19 group was significantly lower than that in the control group (21.92% vs. 30.19%, P = 0.018). The risk of COVID-19 was higher for individuals with blood group A than for those with blood group O (OR = 1.849, 95% CI = 1.228-2.768, P = 0.003). The risk of COVID-19 was higher for patients with blood group A than for those with a blood group other than A (OR = 1.544, 95% CI = 1.122-2.104, P = 0.006). Patients with blood group O had a lower risk of COVID-19 than non-O blood group patients (OR = 0.649, 95% CI = 0.457-0.927, P = 0.018). The ABO blood group distribution was related to COVID-19 status.

CONCLUSIONS

Patients with blood group A had an increased risk for infection with SARS-CoV-2, whereas blood group O was associated with a decreased risk, indicating that certain ABO blood groups were correlated with SARS-CoV-2 susceptibility. Blood type was related to some clinical characteristics of patients with COVID-19.

Association of dengue disease severity and blood group: A systematic review and meta-analysis

Dengue disease encompasses various clinical manifestations including dengue fever (DF) and dengue hemorrhagic fever (DHF). In this article, we aimed to systematically review and analyze the association between different blood groups and severity of dengue. We searched nine databases for eligible papers reporting prevalence, distribution, and frequency of blood group type among dengue patients. Network meta-analysis using R software was used to analyze the data. Of a total of 63 reports screened, we included 10 studies with total sample size 1977 patients (1382 DF and 595 DHF). Blood group O was found to have the worst outcome with the highest risk of developing DF (P-score = 0.01) followed by group B (P-score = 0.34), group A (P-score = 0.64), and group AB (P-score = 1), respectively. Blood group O also had the worst outcome with highest risk of developing DHF (P-score = 0.1) followed by group B (P-score = 0.29), group A (P-score = 0.61), and group AB (P-score = 1), respectively. There was a significant increase (P-value <.001) in the overall odds risk of dengue infection among patients with Rhesus-positive blood groups [OR = 540.03; (95% CI = 151.48-1925.18)]. However, there was no significant difference in the odds risk of DF when compared to DHF according to Rhesus status (P-value = .954). This study identified the O blood group as a potential risk factor in predicting clinical severity in dengue patients which may be helpful in evaluating patients for their likely need for critical care.

Association of ABO blood groups with dengue fever and its complications in a tertiary care hospital

CONTEXT:

Dengue fever (DF) has been steadily increasing in India with outbreaks in certain areas taking the proportion of epidemics. Along with secondary dengue, several risk factors predispose to dengue hemorrhagic fever and dengue shock syndrome. Very few studies associating the relationship between dengue and its severity with ABO blood group have been documented.

AIMS:

The aim of this study was to determine the association between distribution of ABO Rh blood groups and DF and DF with thrombocytopenia.

SETTINGS AND DESIGN:

This was a retrospective descriptive study conducted at the clinical laboratory of the department of microbiology.

MATERIALS AND METHODS:

Dengue patients whose case record contained information on blood group were screened for details of blood group and confirmed dengue diagnosis. Randomly 384 case records were selected. These were divided into two groups; Group 1 included DF cases (platelet count >20,000) and Group 2 included DF cases with thrombocytopenia (platelet count <20,000). Control group consisted of patients other than dengue, whose blood grouping had been done; randomly 390 were selected and analyzed.

STATISTICAL ANALYSIS USED:

P value was calculated using the Chi-square test. Odds ratio were calculated using the Fisher's exact test.

RESULTS:

DF was higher in 23% of individuals with AB blood group as compared to 8.5% of controls (P = 0.0004), whereas patients with blood group O were significantly less affected with DF (P = 0.0048). Disease severity was not associated with any of the blood groups.

CONCLUSIONS:

Individuals with AB blood group are more prone to DF, whereas individuals with blood group O are less prone.

A cross-sectional study of acute dengue infection in paediatric clinics in Cameroon

BACKGROUND

Dengue fever is the world's fastest spreading mosquito borne viral infection. It is prevalent throughout both subtropical and tropical region, and affects over 128 countries. Dengue virus (DENV) infection poses a serious global public health challenge to three billion people, resulting in approximately 200 million cases of morbidity and 50,000 cases of mortality annually. In Cameroon like in most sub-Saharan African countries, DENV infection occur concurrently with other infectious diseases whose symptoms often overlap, rendering differential diagnosis challenging. This study aims at determining the frequency of acute dengue among febrile children under 15 years attending hospitals in some areas of Cameroon.

METHODS

A total of 961 children under the age of 15 were recruited in a cross-sectional study using systematic sampling technique and by selecting each subject out of the three. The study was conducted in 10 public health centers in Cameroon. Demographic data and risk factors of the subjects were obtained using well-structured questionnaires. Dengue virus NS1 antigen, IgM and IgG were analysed using a Tell me fast® Combo Dengue NS1-IgG/IgM Rapid Test. An in-house ELISA test for dengue specific IgM antibody was equally performed for confirmation. Descriptive statistical analysis was performed using Graph pad version 6.0.

RESULTS

A prevalence of 6.14% acute dengue virus infection was observed among children with febrile illness with a significant difference (p = 0.0488) between males (4.7%) and females (7.7%). In addition, children who reportedly were unprotected from vectors, showed a comparatively higher prevalence of the disease seropositivity than those practicing protective measures.

CONCLUSION

DENV infection therefore is an important cause of fever among children in Cameroon. Thus, there is a need to include differential screening for DENV infections as a tool in the management of fever in children in the country.

Association of ABO Blood Group and Body Mass Index: A Cross-Sectional Study from a Ghanaian Population

ABO blood group and body mass index (BMI) have individually been appraised as risk factors for certain diseases. From statistical perspective, it may be important to examine the relationship between the ABO blood antigen and BMI. This cross-sectional study involved 412 participants aged 18 to 46 at the Kwame Nkrumah University of Science and Technology (KNUST), Kumasi. Weight and height of participants were measured for BMI calculation; blood group determination was done using antisera. Blood group O was the most prevalent (51.2%), while Rhesus-positive individuals constituted 90.3%. 6.3% of the participants were obese, while 18.7% were overweight. There was significant (p=0.006) higher prevalence of obesity in females (10.3%) than in males (3.4%). The study did not observe any significant difference by association of ABO blood group with gender (p=0.973), BMI (p=0.307), or Rhesus status (p=0.723). Regarding gender (p=0.400) and BMI (p=0.197), no statistically significant difference was observed between Rhesus blood groups. The prevalence of overweight, obesity, blood type O, and rhesus positive observed among students in this study is largely similar to what has been reported in published studies in Ghana and from other countries. Overweight and obesity were not associated with ABO blood groups or Rhesus in this study.

Blood group AB is associated with severe forms of dengue virus infection

Several viral and host factors are believed to contribute to the development of severe forms of dengue such as dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) following a dengue virus (DENV) infection. The pathogenesis of DHF/DSS is not fully understood, however, host factors like ABO blood groups have been shown to contribute to the severity of DENV infection. The present study investigated the association of blood groups with severity of DENV infection in the northern region of Sri Lanka. The blood-groups of 405 patients positive for DENV NS1 antigen and anti-DENV IgM/IgG were determined using the standard haemagglutination assay recommended by the national blood bank/s. The occurrence of severe dengue in patients with certain blood groups was significantly different (p < 0.001) to those with other blood groups. Patients with AB blood group had more than 2.5 times higher risk of developing DHF than those with other blood groups. On the other hand, patients with blood group O were significantly under represented for DHF relative to the proportion of this blood group in the general population. Thus dengue patients with blood group O appear to have a low risk of developing DHF than those with other blood groups.

Blood type biochemistry and human disease

Associations between blood type and disease have been studied since the early 1900s when researchers determined that antibodies and antigens are inherited. In the 1950s, the chemical identification of the carbohydrate structure of surface antigens led to the understanding of biosynthetic pathways. The blood type is defined by oligosaccharide structures, which are specific to the antigens, thus, blood group antigens are secondary gene products, while the primary gene products are various glycosyltransferase enzymes that attach the sugar molecules to the oligosaccharide chain. Blood group antigens are found on red blood cells, platelets, leukocytes, plasma proteins, certain tissues, and various cell surface enzymes, and also exist in soluble form in body secretions such as breast milk, seminal fluid, saliva, sweat, gastric secretions, urine, and amniotic fluid. Recent advances in technology, biochemistry, and genetics have clarified the functional classifications of human blood group antigens, the structure of the A, B, H, and Lewis determinants and the enzymes that produce them, and the association of blood group antigens with disease risks. Further research to identify differences in the biochemical composition of blood group antigens, and the relationship to risks for disease, can be important for the identification of targets for the development of nutritional intervention strategies, or the identification of druggable targets. WIREs Syst Biol Med 2016, 8:517-535. doi: 10.1002/wsbm.1355 For further resources related to this article, please visit the WIREs website.

Blood group A and D negativity are associated with symptomatic West Nile virus infection

BACKGROUND

West Nile virus (WNV) infection is mostly asymptomatic (AS) but 20% of subjects report WNV fever and 1% of patients experience neurologic diseases with higher rates in elderly and immunosuppressed persons. With no treatment and no vaccine to prevent the development of symptomatic (S) infections, it is essential to understand prognostic factors influencing S disease outcome. Host genetic background has been linked to the development of WNV neuroinvasive disease. This study investigates the association between the ABO and D blood group status and WNV disease outcome.

STUDY DESIGN AND METHODS

The distribution of blood groups was investigated within a cohort of 374 WNV+ blood donors including 244 AS and 130 S WNV+ blood donors. Logistic regression analyses were used to examine associations between A, B, O, and D blood groups and WNV clinical disease outcome.

RESULTS

S WNV+ donors exhibited increased frequencies of blood group A (S 47.6%, AS 36.8%, p = 0.04; odds ratio [OR], 1.56; 95% confidence interval [CI], 1.01-2.40) and D- individuals (S 21.5%, AS 13.1%, p = 0.03; OR, 1.82; 95% CI, 1.04-3.18).

CONCLUSION

The findings suggest a genetic susceptibility placing blood group A and D- individuals at risk for the development of S disease outcome after WNV infection.

Association of ABO Blood Group Phenotype and Allele Frequency with Chikungunya Fever

Background. The objective of this study was to investigate the association of the ABO blood group phenotype and allele frequency with CHIK fever. Methods. A rural community survey in Southern Thailand was conducted in August and September 2010. A total of 506 villagers were enrolled. Cases were defined as individuals having anti-CHIK IgG by hemagglutination ≥1 : 10. Results. There were 314 cases (62.1%) with CHIK seropositivity. Females were less likely to have positive anti-CHIK IgG with odds ratio (OR) (95% CI) of 0.63 (0.43, 0.93). All samples tested were Rh positive. Distribution of CHIK seropositivity versus seronegativity (P value) in A, B, AB, and O blood groups was 80 versus 46 (0.003), 80 versus 48 (0.005), 24 versus 20 (0.55), and 130 versus 78 (<0.001), respectively. However, chi-square test between ABO and CHIK infection showed no statistical significance (P = 0.76). Comparison of the ABO blood group allele frequency between CHIK seropositivity and seronegativity was not statistically significant. Conclusion. This finding demonstrated no association of the ABO blood group phenotypes and allele frequencies with CHIK infection.

ABO blood groups and susceptibility to brucellosis

The relationship between blood groups and some infections such as norovirus, cholera, and malaria has been reported. Despite the importance of brucellosis, there is a lack of data on the relationship between blood groups and brucellosis. Thus, in this study, we examined the relationship between blood groups and brucellosis. In this case-control study, the blood groups of 100 patients with brucellosis and 200 healthy individuals were studied. Exclusion criteria for the control group consisted of a positive Coombs Wright test or a history of brucellosis. The chi-square test was used to compare qualitative variables between the two groups. The variables that met inclusion criteria for the regression model were entered into the logistic regression model. A total of 43% patients were female and 57% male; 27% were urban and 73% rural. Regression analysis showed that the likelihood of brucellosis infection was 6.26 times more in people with blood group AB than in those with blood group O (P<0.001). However, Rh type was not associated with brucellosis infection. Thus, there is a relationship between blood group and brucellosis. People with blood group AB were susceptible to brucellosis, but no difference was observed for brucellosis infection in terms of blood Rh type.

The human dengue challenge experience at the Walter Reed Army Institute of Research

Recent discordance between measured levels of serotypes of dengue virus neutralizing antibody and clinical outcomes suggests a need to reevaluate the process of prescreening dengue vaccine candidates to better predict their clinical benefit before initiation of large-scale human vaccine trials. In the absence of a reliable animal model for dengue, a human dengue virus challenge model (ie, a controlled live dengue virus infectious challenge study) may prove useful and timely to elucidate mechanisms that underlie protection (as well as virulence), thus facilitating down-selection of vaccine candidates before beginning advanced field trials. Dengue challenge studies were safely used in prior decades to study the vector biology, clinical spectrum of illness, and reactogenicity of candidate live dengue virus vaccines of uncertain attenuation. Redeveloping the human dengue challenge model following current regulatory guidance, good manufacturing practice, and good clinical practice could streamline and accelerate vaccine development by offering a time- and resource-efficient method to evaluate the safety and potential efficacy of dengue vaccine and therapeutic candidates. In this article, the development of such a challenge model and its subsequent application is summarized from 2 recent reports.

Polymorphism of DC-SIGN (CD209) promoter in association with clinical symptoms of dengue fever

C-type lectin DC-SIGN receptor, encoded by CD209, plays a key role in the infection of dendritic cells by dengue virus (DENV). Because the -336A/G SNP (rs4804803) polymorphism in the promoter of CD209 modulates DC-SIGN expression, we investigated the putative association of this polymorphism with DENV infection and its pathogenesis. A control sample of 72 individuals, rigorously selected through a clinical investigation for absence of past dengue fever (DF) was compared to a sample of 168 patients (156 classical DF; 12 dengue hemorrhagic fever), all residents from Pará, Brazil. However, the prevalence of symptoms showed a trend higher in the AA genotype (Wilcoxon test; Z=2.02; p=0.04). Hence, our findings indicate that the G allele downregulates the spectrum of symptoms during the early acute phase of DENV infection, putatively decreasing the viremia, as suggested in the literature.

ABO blood groups of residents and the ABO host choice of malaria vectors in southern Iran

Recent epidemiological evidences revealed the higher prevalence of 'O' blood group in the residents of malaria-endemic areas. Also some data indicated preference of mosquitoes to 'O' group. The aim of this study was to determine ABO group ratio in the residents as well as ABO group preference of Anopheles in two malaria endemic areas in south of Iran. Agglutination method was used for ABO typing of residents. Field blood fed Anopheles specimens were tested against vertebrate DNA using mtDNA-cytB PCR-RFLP and then the human fed specimens were tested for ABO groups using multiplex allele-specific PCR. A total of 409 human blood samples were identified, of which 150(36.7%) were 'O' group followed by 113(27.6%), 109(26.7%), and 37(9.0%) of A, B, and AB groups respectively. Analyzing of 95 blood fed mosquitoes revealed that only four Anopheles stephensi had fed human blood with A(1), B(1), and AB(2) groups. Result of this study revealed high prevalence of O group in south of Iran. To our knowledge, it is the first ABO molecular typing of blood meal in mosquitoes; however, due to low number of human blood fed specimens, ABO host choice of the mosquitoes remains unknown. This study revealed that ABO blood preference of malaria vectors and other arthropod vectors deserves future research.

The Higher Frequency of Blood Group B in a Brazilian Population with HIV Infection

OBJECTIVE

To analyze the frequency of and odds for and against HIV infection based on ABO blood type in a large sample of blood donors.

BACKGROUND

Coevolution between pathogens and hosts may explain the ABO system of polymorphisms. HIV-infected cells add ABO(H) blood group antigens to the viral envelope. Naturally occurring antibodies against ABO(H) antigens that are present in normal human sera are able to neutralize ABO-expressing HIV in vitro. Blood donors are ideal for studying blood groups and HIV infection in vivo because all donors are routinely typed and tested.

METHODS

All blood donors who donated blood between 1994 and 2010 were tested for HIV (ELISA antibody tests and Western blot test or immunofluorescence testing) and were ABO typed (direct and reverse grouping tests). HIV infection based on the ABO blood group was analyzed using the chi-square test and game theory.

RESULTS

The total number of examined blood donors during this period was 271,410, of whom 389 were infected with HIV. B-group donors were more infected than non-B donors (p= 0.006).

CONCLUSIONS

A more restricted antigen recognition capacity of anti-Galα1-3Gal in blood groups AB and B and a weaker antigen-binding capacity of anti-A antibodies may contribute to a higher frequency of HIV infection in blood group B.

Can non-human primates serve as models for investigating dengue disease pathogenesis?

Dengue Virus (DV) infects between 50 and 100 million people globally, with public health costs totaling in the billions. It is the causative agent of dengue fever (DF) and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), vector-borne diseases that initially predominated in the tropics. Due to the expansion of its mosquito vector, Aedes spp., DV is increasingly becoming a global problem. Infected individuals may present with a wide spectrum of symptoms, spanning from a mild febrile to a life-threatening illness, which may include thrombocytopenia, leucopenia, hepatomegaly, hemorrhaging, plasma leakage and shock. Deciphering the underlining mechanisms responsible for these symptoms has been hindered by the limited availability of animal models that can induce classic human pathology. Currently, several permissive non-human primate (NHP) species and mouse breeds susceptible to adapted DV strains are available. Though virus replication occurs in these animals, none of them recapitulate the cardinal features of human symptomatology, with disease only occasionally observed in NHPs. Recently our group established a DV serotype 2 intravenous infection model with the Indian rhesus macaque, which reliably produced cutaneous hemorrhages after primary virus exposure. Further manipulation of experimental parameters (virus strain, immune cell expansion, depletion, etc.) can refine this model and expand its relevance to human DF. Future goals include applying this model to elucidate the role of pre-existing immunity upon secondary infection and immunopathogenesis. Of note, virus titers in primates in vivo and in vitro, even with our model, have been consistently 1000-fold lower than those found in humans. We submit that an improved model, capable of demonstrating severe pathogenesis may only be achieved with higher virus loads. Nonetheless, our DV coagulopathy disease model is valuable for the study of select pathomechanisms and testing DV drug and vaccine candidates.

High content screening of a kinase-focused library reveals compounds broadly-active against dengue viruses

Dengue virus is a mosquito-borne flavivirus that has a large impact in global health. It is considered as one of the medically important arboviruses, and developing a preventive or therapeutic solution remains a top priority in the medical and scientific community. Drug discovery programs for potential dengue antivirals have increased dramatically over the last decade, largely in part to the introduction of high-throughput assays. In this study, we have developed an image-based dengue high-throughput/high-content assay (HT/HCA) using an innovative computer vision approach to screen a kinase-focused library for anti-dengue compounds. Using this dengue HT/HCA, we identified a group of compounds with a 4-(1-aminoethyl)-N-methylthiazol-2-amine as a common core structure that inhibits dengue viral infection in a human liver-derived cell line (Huh-7.5 cells). Compounds CND1201, CND1203 and CND1243 exhibited strong antiviral activities against all four dengue serotypes. Plaque reduction and time-of-addition assays suggests that these compounds interfere with the late stage of viral infection cycle. These findings demonstrate that our image-based dengue HT/HCA is a reliable tool that can be used to screen various chemical libraries for potential dengue antiviral candidates.

Dengue, a re-emergent human disease that places nearly half of the world's population at risk, threatens to further expand in geographical distribution. The lack of an available effective dengue vaccine has encouraged the search for antiviral drugs as an alternative approach. In recent years, drug discovery through high-throughput screening has become a trend in the search for dengue antivirals. In this study, we developed an image-based dengue high-throughput/high-content assay using prevalent viral strains of three dengue serotypes (DENV1, DENV2 and DENV3) isolated from dengue outbreaks in South America and a laboratory-adapted strain of DENV4. We demonstrated the usefulness of our image-based dengue HT/HCA in identifying potential dengue antivirals by screening a small subset of chemical compounds for inhibition of dengue virus infection in a human-derived host cell line (Huh-7.5), and partially characterized their activities against dengue infection in a mosquito host cell line (C6/36), a distantly-related virus (hepatitis C virus), and an unrelated virus that is transmitted by the same mosquito vector (chikungunya virus).

Severe dengue is associated with consumption of von Willebrand factor and its cleaving enzyme ADAMTS-13

Background

Thrombocytopenia, bleeding and plasma leakage are cardinal features of severe dengue. Endothelial cell activation with exocytosis of Weibel-Palade bodies (WPBs) may play an etiological role in this condition.

Methods and Principal Findings

In a cohort of 73 Indonesian children with dengue hemorrhagic fever (DHF), of which 30 with dengue shock syndrome (DSS), we measured plasma levels of the WPB constituents von Willebrand factor antigen (VWF:Ag), VWF propeptide and osteoprotegerin (OPG), together with activity levels of the VWF-cleaving enzyme ADAMTS-13 and the amount of VWF in a platelet binding conformation (VWF activation factor). Compared with healthy controls (n = 17), children with DHF/DSS had significantly higher levels of VWF:Ag, VWF propeptide and OPG and decreased ADAMTS-13 activity. The VWF activation factor was also significantly higher in DHF/DSS and highest in children who died. There were significant differences in the kinetics of the various WPB constituents: VWF propeptide and OPG levels decreased toward discharge, while VWF:Ag levels were lower than expected at enrollment with plasma levels increasing toward discharge. Moreover, VWF propeptide levels correlated better with markers of disease severity (platelet count, liver enzymes, serum albumin and pleural effusion index) than corresponding VWF levels. Together, these findings suggest that there is consumption of VWF in DHF/DSS. In 4 out of 15 selected children with low ADAMTS-13 levels on admission, we found a remarkable reduction in the large and intermediate VWF multimers in the discharge blood samples, consistent with an acquired von Willebrand disease.

Conclusion

These findings suggest that severe dengue is associated with exocytosis of WPBs with increased circulating levels of VWF:Ag, VWF propeptide and OPG. High circulating levels of VWF in its active conformation, together with low ADAMTS-13 activity levels, are likely to contribute to the thrombocytopenia and complications of dengue. During the convalescence phase, qualitative defects in VWF with loss of larger VWF multimers may develop.

Severe dengue infections are characterized by thrombocytopenia, clinical bleeding and plasma leakage. Activation of the endothelium, the inner lining of blood vessels, leads to the secretion of storage granules called Weibel Palade bodies (WPBs). We demonstrated that severe dengue in Indonesian children is associated with a strong increase in plasma levels of the WPB constituents von Willebrand factor (VWF), VWF propeptide and osteoprotegerin (OPG). An increased amount of the hemostatic protein VWF was in a hyperreactive, platelet binding conformation, and this was most pronounced in the children who died. VWF levels at enrollment were lower than expected from concurrent VWF propeptide and OPG levels and VWF levels did not correlate well with markers of disease severity. Together, this suggests that VWF is being consumed during severe dengue. Circulating levels of the VWF-cleaving enzyme ADAMTS-13 were reduced. VWF is a multimeric protein and a subset of children had a decrease in large and intermediate VWF multimers at discharge. In conclusion, severe dengue is associated with exocytosis of WPBs with consumption of VWF and low ADAMTS-13 activity levels. This may contribute to the thrombocytopenia and complications of dengue.

Histo-blood group gene polymorphisms as potential genetic modifiers of the development of coronary artery lesions in patients with Kawasaki disease

Abnormal immunological responses to certain microbial agents may play a crucial role in the pathogenesis of Kawasaki disease (KD). The association studies between histo-blood group genes (Lewis and ABO blood types) and various types of infectious diseases or vasculopathy have been carried out based on the fact that glycosylated antigens could directly mediate microbial infections. We attempted to clarify the role of blood type antigens in the development of KD and coronary artery lesions in KD patients. The subjects included 164 KD patients enrolled from 1998 to 2003 (1st group), 232 patients from 2004 to 2009 (2nd group), and 223 healthy children and 118 patients with growth hormone deficiency as controls. The genotyping of the FUT2 and FUT3 genes, and ABO genotypes, was determined with the TaqMan SNP assay and allele-specific polymerase chain reaction. No significant differences were observed in the genotypes and allele frequencies of the FUT2 and FUT3 genes between the groups. The frequency of the BB blood genotype was significantly higher in KD patients with coronary artery lesions in the 1st and 2nd groups than in the controls (17% and 14% vs. 5%, P = 0.0020). This is the first report to investigate the roles of ABO and Lewis blood types in the development of KD, and in the formation of coronary artery lesions in KD patients. These data suggest that the ABO blood type may play a role in the development of coronary artery lesions in KD patients.

Host genetic susceptibility to severe dengue infection

Epidemiological evidence indicates that host genetic factors are relevant and predispose DHF/DSS development. Here, we review the host genetic studies concerning human leucocyte antigens, antibody receptors, immune/inflammatory mediators, attachment molecules, cytokines and other factors exerting an immunoregulatory effect as well as the current genome-wide association studies. We also discuss some viewpoints on future challenges related to the design of safe and effective prevention and treatment options.

Dengue: a continuing global threat

Dengue fever and dengue haemorrhagic fever are important arthropod-borne viral diseases. Each year, there are ∼50 million dengue infections and ∼500,000 individuals are hospitalized with dengue haemorrhagic fever, mainly in Southeast Asia, the Pacific and the Americas. Illness is produced by any of the four dengue virus serotypes. A global strategy aimed at increasing the capacity for surveillance and outbreak response, changing behaviours and reducing the disease burden using integrated vector management in conjunction with early and accurate diagnosis has been advocated. Antiviral drugs and vaccines that are currently under development could also make an important contribution to dengue control in the future.

An outbreak of dengue fever in St. Croix (US Virgin Islands), 2005

Background

Periodic outbreaks of dengue fever occur in the United States Virgin Islands. In June 2005, an outbreak of dengue virus (DENV) serotype-2 with cases of dengue hemorrhagic fever (DHF) was detected in St. Croix, US Virgin Islands. The objective of this report is to describe this outbreak of DENV-2 and the findings of a case-control study examining risk factors for DHF.

Methodology/Principal Findings

This is the largest dengue outbreak ever recorded in St. Croix, with 331 suspected dengue cases reported island-wide during 2005 (62.2 cases/10,000 population); 54% were hospitalized, 21% had at least one hemorrhagic manifestation, 28% had thrombocytopenia, 5% had DHF and 1 patient died. Eighty-nine laboratory-positive hospitalized patients were identified. Of these, there were 15 (17%) who met the WHO criteria for DHF (cases) and 74 (83%) who did not (controls). The only variable significantly associated with DHF on bivariate or multivariable analysis was age, with an adjusted odds ratio (95% confidence interval) of 1.033 (1.003,1.064).

Conclusions/Significance

During this outbreak of DENV-2, a high proportion of cases developed DHF and increasing age was significantly associated with DHF.

Association between nutritional status and severity of dengue infection in children in El Salvador

Clinical observations and some studies suggest that dengue virus infection is more severe among children with better nutritional status. We examined the nutritional status of children in El Salvador and its relationship between this and the severity of dengue infection. Z-scores for weight-for-age, height-for-age, and body mass index (BMI)-for-age of children with dengue fever (66), dengue hemorrhagic fever (62), and healthy controls (74) were compared. There were no differences in weight-for-age or BMI-for-age Z-scores between the three groups. Children with dengue fever had a greater height-for-age than healthy controls but no significant differences in rates of stunting. There was no difference in height between children with dengue fever and dengue hemorrhagic fever. Excess nutrition does not appear to be a risk factor for severe forms of dengue infection in El Salvador, nor does malnutrition appear to be predictive of good outcomes.

Serotype-specific differences in the risk of dengue hemorrhagic fever: an analysis of data collected in Bangkok, Thailand from 1994 to 2006

Background

It is unclear whether dengue serotypes differ in their propensity to cause severe disease. We analyzed differences in serotype-specific disease severity in children presenting for medical attention in Bangkok, Thailand.

Methodology/Principal Findings

Prospective studies were conducted from 1994 to 2006. Univariate and multivariate logistic and multinomial logistic regressions were used to determine if dengue hemorrhagic fever (DHF) and signs of severe clinical disease (pleural effusion, ascites, thrombocytopenia, hemoconcentration) were associated with serotype. Crude and adjusted odds ratios were calculated. There were 162 (36%) cases with DENV-1, 102 (23%) with DENV-2, 123 (27%) with DENV-3, and 64 (14%) with DENV-4. There was no significant difference in the rates of DHF by serotype: DENV-2 (43%), DENV-3 (39%), DENV-1 (34%), DENV-4 (31%). DENV-2 was significantly associated with increased odds of DHF grade I compared to DF (OR 2.9 95% CI 1.1, 8.0), when using DENV-1 as the reference. Though not statistically significant, DENV-2 had an increased odds of total DHF and DHF grades II, III, and IV. Secondary serologic response was significantly associated with DHF (OR 6.2) and increased when considering more severe grades of DHF. DENV-2 (9%) and -4 (3%) were significantly less often associated with primary disease than DENV-1 (28%) and -3 (33%). Restricting analysis to secondary cases, we found DENV-2 and DENV-3 to be twice as likely to result in DHF as DEN-4 (p = 0.05). Comparing study years, we found the rate of DHF to be significantly less in 1999, 2000, 2004, and 2005 than in 1994, the study year with the highest percentage of DHF cases, even when controlling for other variables.

Conclusions/Significance

As in other studies, we find secondary disease to be strongly associated with DHF and with more severe grades of DHF. DENV-2 appears to be marginally associated with more severe dengue disease as evidenced by a significant association with DHF grade I when compared to DENV-1. In addition, we found non-significant trends with other grades of DHF. Restricting the analysis to secondary disease we found DENV-2 and -3 to be twice as likely to result in DHF as DEN-4. Differences in severity by study year may suggest that other factors besides serotype play a role in disease severity.

The four dengue viruses (DENV) represent the most common human arbovirus infections in the world and are currently a challenging problem, particularly in the tropical and subtropical regions of Asia and the Americas. Infection with DENV may produce symptoms of varying severity. While access to care, appropriate interventions, host genetic factors, and previous exposure to DENV are all known to affect the outcome of the infection, it is not entirely understood why some individuals develop more severe disease. It has been hypothesized that the four dengue serotypes differ in disease severity and clinical manifestations. This analysis assessed whether there were significant differences in severity of disease caused by the dengue serotypes in a pediatric population in Thailand. We found significant and non-significant correlations between dengue serotype 2 infection and more severe dengue disease. We also found that individual serotypes varied in disease severity between study years, perhaps supporting the hypothesis that the particular sequences of primary and secondary DENV infections influence disease severity.

HLA and other gene associations with dengue disease severity

Large case control gene association studies have been performed on cohorts of dengue virus (DENV) infected patients identified in mainland Southeast Asia, South Asia and the Caribbean. Candidate genes that have shown statistically significant associations with DENV disease severity encode HLA molecules, cell receptors for IgG (FcGII), vitamin D and ICAM3 (DCSIGN or CD209), pathogen recognition molecules such as mannose binding lectin (MBL), blood related antigens including ABO and human platelet antigens (HPA1 and HPA2). In ethnic Thais with secondary infections a variety of HLA class I alleles (HLA-A 0203, 0207, A11, B 15, B 44, B 46, B 48, B 51, B 52), DCSIGN promoter polymorphisms and the AB blood group, independently associate with either susceptibility or resistance to dengue fever (DF) and the more severe dengue hemorrhagic fever (DHF). There is also evidence that some HLA associations with disease severity correlate with the DENV serotype inducing secondary infections. Taken together, there is now evidence that allelic variants of multiple gene loci involved in both acquired and innate immune responses contribute significantly to DENV disease outcome and severity. Further analysis of the genetic basis of severe DENV disease in different at risk populations may contribute to the development of new preventative and therapeutic interventions.

MBL2 gene polymorphisms protect against development of thrombocytopenia associated with severe dengue phenotype

Dengue disease can clinically evolve from an asymptomatic and mild disease, known as dengue fever (DF), to a severe disease known as dengue hemorrhagic fever (DHF). Recent evidence has shown how host genetic factors can be correlated with severe dengue susceptibility or protection. Many of these genes, such as CD209, TNF-a, vitamin D receptor, and FC gamma receptor IIA, are components of the innate immune system, suggesting that innate responses might have a role in dengue pathogenesis. MBL2 gene polymorphisms have been shown to modulate susceptibility or protection in many viral diseases. We investigated the involvement of MBL2 gene in the dengue clinical outcome through the analysis of MBL2 exon 1 polymorphisms (at codons 52, 54, and 57) known to be associated with reduced serum levels of the MBL protein. The genotypes of 110 well-characterized dengue-positive patients were statistically analyzed to establish possible correlations between MBL2 polymorphisms and parameters such as sex, type of infection (primary or secondary response), race/ethnicity, course of infection, and age. We found significant correlations between wild-type AA MBL2 genotype and age as associated risk factors for development of dengue-related thrombocytopenia.