Rajendranath Ramasawmy

Rheumatic Fever and Rheumatic Heart Disease: Genetics and Pathogenesis

Molecular mimicry between streptococcal and human proteins is considered as the triggering factor leading to autoimmunity in rheumatic fever (RF) and rheumatic heart disease (RHD). Here, we present a review of the genetic susceptibility markers involved in the development of RF/RHD and the major immunopathological events underlying the pathogenesis of RF and RHD. Several human leucocyte antigen (HLA) class II alleles are associated with the disease. Among these alleles, HLA‐DR7 is predominantly observed in different ethnicities and is associated with the development of valvular lesions in RHD patients. Cardiac myosin is one of the major autoantigens involved in rheumatic heart lesions and several peptides from the LMM (light meromyosin) region were recognized by peripheral and intralesional T‐cell clones from RF and RHD patients. The production of TNF‐α and IFN‐γ from heart‐infiltrating mononuclear cells suggests that Th‐1 type cytokines are the mediators of RHD heart lesions while the presence of few interleukin‐4 producing cells in the valve tissue contributes to the maintenance and progression of the valvular lesions.

Immunological and non-immunological effects of cytokines and chemokines in the pathogenesis of chronic Chagas disease cardiomyopathy

The pathogenesis of Chagas disease cardiomyopathy (CCC) is not well understood. Since studies show that myocarditis is more frequent during the advanced stages of the disease, and the prognosis of CCC is worse than that of other dilated cardiomyopathies of non-inflammatory aetiology, which suggest that the inflammatory infiltrate plays a major role in myocardial damage. In the last decade, increasing evidence has shown that inflammatory cytokines and chemokines play a role in the generation of the inflammatory infiltrate and tissue damage. CCC patients have an increased peripheral production of the inflammatory Th1 cytokines IFN-gamma and TNF-alpha when compared to patients with the asymptomatic/indeterminate form. Moreover, Th1-T cells are the main producers of IFN-gamma and TNF-alpha and are frequently found in CCC myocardial inflammatory infiltrate. Over the past several years, our group has collected evidence that shows several cytokines and chemokines produced in the CCC myocardium may also have a non-immunological pathogenic effect via modulation of gene and protein expression in cardiomyocytes and other myocardial cell types. Furthermore, genetic polymorphisms of cytokine, chemokine and innate immune response genes have been associated with disease progression. We will review the molecular and immunological mechanisms of myocardial damage in human CCC in light of recent findings.

Association of Mannose-Binding Lectin Gene Polymorphism but Not of Mannose-Binding Serine Protease 2 with Chronic Severe Aortic Regurgitation of Rheumatic Etiology

ABSTRACT N-Acetylglucosamine (GlcNAc) is the major immunoepitope of group A streptococcal cell wall carbohydrates. Antistreptococcal antibodies cross-reactive with anti-GlcNAc and laminin are present in sera of patients with rheumatic fever. The cross-reactivity of these antibodies with human heart valvular endothelium and the underlying basement membrane has been suggested to be a possible cause of immune-mediated valve lesion. Mannose-binding lectin (MBL) encoded by the MBL2 gene, a soluble pathogen recognition receptor, has high affinity for GlcNAc. We postulated that mutations in exon 1 of the MBL2 gene associated with a deficient serum level of MBL may contribute to chronic severe aortic regurgitation (AR) of rheumatic etiology. We studied 90 patients with severe chronic AR of rheumatic etiology and 281 healthy controls (HC) for the variants of the MBL2 gene at codons 52, 54, and 57 by using a PCR-restriction fragment length polymorphism-based method. We observed a significant difference in the prevalence of defective MBL2 alleles between patients with chronic severe AR and HC. Sixteen percent of patients with chronic severe AR were homozygotes or compound heterozygotes for defective MBL alleles in contrast to 5% for HC (P = 0.0022; odds ratio, 3.5 [95% confidence interval, 1.6 to 7.7]). No association was detected with the variant of the MASP2 gene. Our study suggests that MBL deficiency may contribute to the development of chronic severe AR of rheumatic etiology.

BAT1, a Putative Anti-Inflammatory Gene, Is Associated with Chronic Chagas Cardiomyopathy

BACKGROUND It is not understood why only a subset of individuals infected with Trypanosoma cruzi develop chronic Chagas cardiomyopathy (CCC). Patients with CCC display high levels of circulating proinflammatory cytokines. Heart-infiltrating lymphocytes from patients with CCC also express proinflammatory cytokines (tumor necrosis factor- alpha and interferon- gamma ) that are detectable in biopsy samples and surgical heart-tissue samples. BAT1, a putative anti-inflammatory gene, presents functional polymorphisms in its promoter region that influence its transcriptional level. METHODS We assessed, by polymerase chain reaction restriction fragment-length polymorphism analysis, BAT1 variants in the promoter region at positions -22C/G and -348C/T in 154 patients with CCC and in 76 T. cruzi-infected but asymptomatic (ASY) patients. RESULTS Of the patients with CCC, 16% were homozygous for the -22C allele, compared with 4% of the ASY patients (P=.004; odds ratio [OR], 4.7 [95% confidence interval {CI}, 1.4-16]). A similar trend was observed for the -348C homozygotes (P=.01; OR, 1.9 [95% CI, 1.0-3.5]). Susceptibility to CCC was conferred by the C variants at nt -22 (P=.003; OR, 1.8 [95% CI, 1.2-2.8]) and at nt -348 (P=.02; OR, 1.7 [95% CI, 1.0-2.8]). CONCLUSIONS BAT1 variants previously associated with reduced expression of HLA-B-associated transcript 1 are predictive of the development of CCC. These variants may be less efficient in down-regulating inflammatory responses and may contribute to the elevated production of proinflammatory cytokines in patients with CCC.

Identification of Oropouche Orthobunyavirus in the cerebrospinal fluid of three patients in the Amazonas, Brazil.

Oropouche fever is the second most frequent arboviral infection in Brazil, surpassed only by dengue. Oropouche virus (OROV) causes large and explosive outbreaks of acute febrile illness in cities and villages in the Amazon and Central-Plateau regions. Cerebrospinal fluid (CSF) samples from 110 meningoencephalitis patients were analyzed. The RNA extracted from fluid was submitted to reverse transcription-polymerase chain reaction and sequencing to identify OROV. Three CSF samples showed the presence of OROV causing infection in the central nervous system (CNS). These patients are adults. Two of the patients had other diseases affecting CNS and immune systems: neurocysticercosis and acquired immunodeficiency syndrome, respectively. Nucleotide sequence analysis showed that the OROV from the CSF of these patients belonged to genotype I. We show here that severe Oropouche disease is occurring during outbreaks of this virus in Brazil.

Simultaneous circulation of all four dengue serotypes in Manaus, State of Amazonas, Brazil in 2011

INTRODUCTION Manaus, the capital city of the state of Amazon with nearly 2 million inhabitants, is located in the middle of the Amazon rain forest and has suffered dengue outbreaks since 1998. METHODS In this study, blood samples were investigated using reverse transcriptase-polymerase chain reaction (RT-PCR), aimed at identifying dengue virus serotypes. RESULTS Acute phase sera from 432 patients were tested for the presence of dengue virus. Out of the 432 patients, 137 (31.3%) were found to be positive. All the four dengue virus serotypes were observed. CONCLUSIONS The simultaneous circulation of the four dengue serotypes is described for the first time in Manaus and in Brazil.

Detection of Herpesvirus, Enterovirus, and Arbovirus infection in patients with suspected central nervous system viral infection in the Western Brazilian Amazon

Acute infections of the central nervous system (CNS) can be caused by various pathogens. In this study, the presence of herpesviruses (HHV), enteroviruses (EVs), and arboviruses were investigated in CSF samples from 165 patients with suspected CNS viral infection through polymerase chain reaction (PCR) and reverse transcriptase PCR. The genomes of one or more viral agents were detected in 29.7% (49/165) of the CSF samples. EVs were predominant (16/49; 32.6%) followed by Epstein‐Barr virus (EBV) (22.4%), Varicella‐Zoster virus (VZV) (20.4%), Cytomegalovirus (CMV) (18.4%), herpes simplex virus (HSV‐1) (4.1%), (HSV‐2) (4.1%), and the arboviruses (14.3%). Four of the arboviruses were of dengue virus (DENV) and three of oropouche virus (OROV). The detection of different viruses in the CNS of patients with meningitis or encephalitis highlight the importance of maintaining an active laboratory monitoring diagnostics with rapid methodology of high sensitivity in areas of viral hyperendemicity that may assist in clinical decisions and in the choice of antiviral therapy. J. Med. Virol. 86:1522–1527, 2014.

Chronic HDV/HBV co-infection: Predictors of disease stage – a case series of HDV-3 patients

BACKGROUND & AIMS Chronic HDV/HBV co-infection is perhaps the most intriguing amongst all viral hepatitis. Only few studies focus deeply on this topic, particularly with patients infected with HDV-3. This study aimed to identify predictors of advanced disease, examining a cross-sectional data of 64 patients. METHODS Histological grading was used to characterize the disease stages and viral loads were tested as predictors of necroinflammatory activity and fibrosis. RESULTS We identified three HDV/HBV co-infection patterns: patients with predominant HDV replication (56.3%), patients with similar viral loads of both viruses (40.6%), and patients with predominant HBV replication (3.1%). Mean HDV-RNA showed a positive trend regarding inflammatory activity and grade of fibrosis. HDV viral load correlated positively with serum levels of liver enzymes and inversely with platelets count. HBV viral load showed no correlation with any of the above parameters. Advanced fibrosis was associated with age, splenomegaly, and HDV viral load of more than 2 log10. Multiple logistic regression confirmed the independent effect of HDV viral predominance. Advanced necroinflammatory activity was independently associated with HDV viral load and splenomegaly. CONCLUSIONS HDV may possibly play an important and direct role in the establishment of necroinflammatory activity and fibrosis. Data show an indigenous HDV genotype, HDV-3, similar to those described in the Amazon region.

Molecular markers of susceptibility to ocular toxoplasmosis, host and guest behaving badly.

Infection with Toxoplasma gondii results in retinochoroiditis in 6% to 20% of immunocompetent individuals. The outcome of infection is the result of a set of interactions involving host genetic background, environmental, and social factors, and the genetic background of the parasite, all of which can be further modified by additional infections or even reinfection. Genes that encode several components of the immune system exhibit polymorphisms in their regulatory and coding regions that affect level and type of expression in response to stimuli, directing the immune response into different pathways. These variant alleles have been associated with susceptibility to immune-mediated diseases and with severity of pathology. We have investigated polymorphisms in several of these genes, identified as candidates for progression to retinochoroiditis caused by toxoplasmosis, namely chemokine (C-C motif) receptor 5 (CCR5), toll-like receptor-2 (TLR2), and TLR4. Furthermore, because interleukin-12 (IL-12) has been shown to be fundamental both in mice and in man to control a protective response against T. gondii, molecules that have a key function in IL-12 production will be emphasized in this review, in addition to discussing the importance of the genetic background of the parasite in the establishment of ocular disease.

Clinical and Virological Descriptive Study in the 2011 Outbreak of Dengue in the Amazonas, Brazil

Background Dengue is a vector-borne disease in the tropical and subtropical region of the world and is transmitted by the mosquito Aedes aegypti. In the state of Amazonas, Brazil during the 2011 outbreak of dengue all the four Dengue virus (DENV) serotypes circulating simultaneously were observed. The aim of the study was to describe the clinical epidemiology of dengue in Manaus, the capital city of the state of the Amazonas, where all the four DENV serotypes were co-circulating simultaneously. Methodology Patients with acute febrile illness during the 2011 outbreak of dengue, enrolled at the Fundação de Medicina Tropical Dr. Heitor Viera Dourado (FMT-HVD), a referral centre for tropical and infectious diseases in Manaus, were invited to participate in a clinical and virological descriptive study. Sera from 677 patients were analyzed by RT-nested-PCRs for flaviviruses (DENV 1–4, Saint Louis encephalitis virus-SLEV, Bussuquara virus-BSQV and Ilheus virus-ILHV), alphavirus (Mayaro virus-MAYV) and orthobunyavirus (Oropouche virus-OROV). Principal Findings Only dengue viruses were detected in 260 patients (38.4%). Thirteen patients were co-infected with more than one DENV serotype and six (46.1%) of them had a more severe clinical presentation of the disease. Nucleotide sequencing showed that DENV-1 belonged to genotype V, DENV-2 to the Asian/American genotype, DENV-3 to genotype III and DENV-4 to genotype II. Conclusions Co-infection with more than one DENV serotype was observed. This finding should be warning signs to health authorities in situations of the large dispersal of serotypes that are occurring in the world.