Emergence of Dengue 4 as Dominant Serotype During 2017 Outbreak in South India and Associated Cytokine Expression Profile

Abstract

Dengue virus (DENV) infection is prevalent in tropical and subtropical regions of the world, which is fatal if untreated symptomatically. Emergence of new genotype within serotypes led to enhanced severity. The objective of the study is to identify the molecular characteristics of the DENV circulated during 2017 outbreak in Tamil Nadu, India, and to investigate the role of inflammatory cytokines in different “serotypes” and in “dengue severity”. A total of 135 suspected samples were tested for DENV infection using IgM, IgG, and qPCR assay; where 76 samples were positive for DENV and analyzed for 12 inflammatory cytokines using ELISA. Serotyping shows 14 DENV-1, 22 DENV-2, 7 DENV-3, and 33 DENV-4, where DENV-4 was predominant. Among 76, 42 isolates were successfully sequenced for C-prM region and grouped. A lineage shift was observed in DENV-4 genotype. Irrespective of serotypes, IFNγ was significantly elevated in all serotypes than control as well as in primary infection than secondary, indicating its role in immune response. GM-CSF and IP-10 were significantly elevated in secondary infection and could be used as prognostic biomarkers for secondary infection. Our observation shows differential cytokine expression profile varied with each serotype, indicating serotype/genotype-specific viral proteins might play a major role in dengue severity. DENV-4 as dominant serotype was reported in Tamil Nadu for the first time during an outbreak with a mixed Th1/Th17 cytokine expression profile that correlated with disease severity. We conclude it is essential to identify circulating viral genotype and their fitness by mutational analysis to correlate with disease severity and immune status, as this correlation will be helpful in diagnostics and therapeutics applications.

Evolutionary dynamics of dengue virus in India

“…Most of the subsequent spread of DENV4-I was restricted to Southeast Asian countries. Although it was introduced in India around 1945, there has been a significant increase in reported DENV4-I sequences from 2015 onwards, especially in South India (Fig 1) [28,60]. It is possible that it remained undetected due to underreporting of mild infections since the primary cases of DENV4 have been reported to cause mild disease [61,62].…”

“…DENV4 is emerging as one of the dominant serotypes in South India (Fig 1B) [28,60]. High divergence in the DENV4-Id lineage in India is largely restricted to immunodominant E and NS2A proteins, again pointing to immune evasion driving its emergence.…”

The Role of Growth Factors in the Pathogenesis of Dengue: A Scoping Review

“…A total of 15 studies analyzed GM-CSF, and 12 found increased levels in dengue patients, half of whom had severe dengue, in contrast with nonsevere dengue and/or healthy controls [ 12 , 37 , 38 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 ], including 1 study in children only [ 48 ]. The increase in GM-CSF levels is evident mainly in the critical phase [ 12 , 37 , 38 , 46 , 52 ], and elevated GM-CSF levels are associated with clinical manifestations of severe dengue, such as cavitary effusion [ 46 ], hypotension [ 45 ], and encephalitis [ 48 ].…”

“…The increase in GM-CSF levels is evident mainly in the critical phase [ 12 , 37 , 38 , 46 , 52 ], and elevated GM-CSF levels are associated with clinical manifestations of severe dengue, such as cavitary effusion [ 46 ], hypotension [ 45 ], and encephalitis [ 48 ]. Furthermore, the expression of GM-CSF varied between the primary and secondary infections for each serotype; the upregulation of GM-CSF was found in primary DENV-1 and secondary DENV-2 infections [ 47 ]. However, three studies found no significant difference between secondary and primary infection, with or without plasma leakage, or during co-infection with malaria [ 29 , 54 , 55 ].…”

“…Macrophages stimulated by GM-CSF are more susceptible to DENV infection, release more inflammatory cytokines when infected, and their supernatant is a potent inducer of vascular permeability in HMEC-1 cell culture [ 84 ]. In addition, another study found that GM-CSF and IFN-γ show antagonistic expression: high levels of GM-CSF antagonized the signals induced by IFN-γ in secondary DENV infections [ 47 ].…”