Virulence of Japanese Encephalitis Virus Genotypes I and III, Taiwan.

The virulence of genotype I (GI) Japanese encephalitis virus (JEV) is under debate. We investigated differences in the virulence of GI and GIII JEV by calculating asymptomatic ratios based on serologic studies during GI- and GIII-JEV endemic periods. The results suggested equal virulence of GI and GIII JEV among humans.

Distinct expression of interferon-induced protein with tetratricopeptide repeats (IFIT) 1/2/3 and other antiviral genes between subsets of dendritic cells induced by dengue virus 2 infection.

Dengue virus (DENV) infection is an emerging public health hazard threatening inhabitants of the tropics and sub-tropics. Dendritic cells (DCs) are one of the major targets of DENV and the initiators of the innate immune response against the virus. However, current in vitro research on the DENV-DC interaction is hampered by the low availability of ex vivo DCs and donor variation. In the current study, we attempted to develop a novel in vitro DC model using immature DCs derived from the myeloid leukaemia cell line MUTZ-3 (IMDCs) to investigate the DENV-DC interaction. The IMDCs morphologically and phenotypically resembled human immature monocyte-derived dendritic cells (IMMoDCs). However, the permissiveness of IMDCs to DENV2 was lower than that of IMMoDCs. RT-PCR arrays showed that a group of type I interferon (IFN) -inducible genes, especially IFIT1, IFITM1, and IFI27, were significantly up-regulated in IMMoDCs but not in IMDCs after DENV2 infection. Further investigation revealed that IFIT genes were spontaneously expressed at both transcriptional and protein levels in the naive IMDCs but not in the naive IMMoDCs. It is possible that the poor permissiveness of IMDCs to DENV2 was a result of the high basal levels of IFIT proteins. We conclude that the IMDC model, although less permissive to DENV2, is a useful platform for studying the suppression mechanism of DENV2 and we expand the knowledge of cellular factors that modulate DENV2 infection in the human body.

Heat shock cognate protein 70 isoform D is required for clathrin-dependent endocytosis of Japanese encephalitis virus in C6/36 cells.

Japanese encephalitis virus (JEV), one of encephalitic flaviviruses, is naturally transmitted by mosquitoes. During infection, JEV generally enters host cells via receptor-mediated clathrin-dependent endocytosis that requires the 70 kDa heat-shock protein (Hsp70). Heat-shock cognate protein 70 (Hsc70) is one member of the Hsp70 family and is constitutively expressed; thus, it may be expressed under physiological conditions. In C6/36 cells, Hsc70 is upregulated in response to JEV infection. Since Hsc70 shows no relationship with viruses attaching to the cell surface, it probably does not serve as the receptor according to our results in the present study. In contrast, Hsc70 is evidently associated with virus penetration into the cell and resultant acidification of intracellular vesicles. It suggests that Hsc70 is highly involved in clathrin-mediated endocytosis, particularly at the late stage of viral entry into host cells. Furthermore, we found that Hsc70 is composed of at least three isoforms, including B, C and D; of these, isoform D helps JEV to penetrate C6/36 cells via clathrin-mediated endocytosis. This study provides relevant evidence that sheds light on the regulatory mechanisms of JEV infection in host cells, especially on the process of clathrin-mediated endocytosis.

Doxycycline cotherapy with albendazole relieves neural function damage in C57BL/6 and BALB/c mice infected with Angiostrongylus cantonensis.

BACKGROUND: We investigated the effects of combination therapy albendazole and doxycycline in Angiostrongylus cantonensis-infected mice during early and late treatment. MATERIALS AND METHODS: C57BL/6 and BALB/c mice were divided into five groups: (i) uninfected, (ii) infected with A. cantonensis, (iii) infected + 10 mg/kg albendazole, (iv) infected + 25mg/kg doxycycline, and (v) infected + 10 mg/kg albendazole + 25 mg/kg doxycycline. We administered drugs in both early treatments started at 7-day post infections (dpi) and late treatments (14 dpi) to A. cantonensis-infected C57BL/6 and BALB/c mice. To assess the impact of these treatments, we employed the Morris water maze test to evaluate spatial learning and memory abilities, and the rotarod test to measure motor coordination and balance in C57BL/6 mice. Additionally, we monitored the expression of the cytokine IL-33 and GFAP in the brain of these mice using western blot analysis. RESULTS: In this study, A. cantonensis infection was observed to cause extensive cerebral angiostrongyliasis in C57BL/6 mice. This condition significantly affected their spatial learning and memory abilities, as assessed by the Morris water maze test, as well as their motor coordination, which was evaluated using the rotarod test. Early treatment with albendazole led to favorable recovery outcomes. Both C57BL/6 and BALB/c mice express IL-33 and GFAP after co-therapy. The differences of levels and patterns of IL-33 and GFAP expression in mice may be influenced by the balance between pro-inflammatory and anti-inflammatory signals within the immune system. CONCLUSIONS: Combination therapy with anthelmintics and antibiotics in the early stage of A. cantonensis infection, in C57BL/6 and BALB/c mice resulted in the death of parasites in the brain and reduced the subsequent neural function damage and slowed brain damage and neurobehavior impairment. This study suggests a more effective and novel treatment, and drug delivery method for brain lesions that can decrease the neurological damage of angiostrongyliasis patients.

Apoptosis of Ascogregarina taiwanensis (Apicomplexa: Lecudinidae), which failed to migrate within its natural host.

Sexual reproduction of Ascogregarina taiwanensis (Apicomplexa: Lecudinidae), a parasite specific to the mosquito Aedes albopictus, in Malpighian tubules is initiated by the entry of the trophotozoites developed in the midgut shortly after pupation (usually <5 h). However, only a low proportion of trophozoites are able to migrate; others end up dying. In this study, we demonstrated that those trophozoites that failed to migrate eventually died of apoptosis. Morphological changes such as shrinkage, chromatin aggregations and formation of blunt ridges on the surface were seen in moribund trophozoites. In addition, DNA fragmentation of trophozoites isolated from the midgut of pupae was demonstrated by the presence of DNA ladders, Annexin V staining and TUNEL assays. Detection of caspase-like activity suggests that apoptosis of those trophozoites may have occurred through a mechanism of an intrinsic or mitochondrial-mediated pathway. Although apoptosis has been observed in various protozoan species, it is not clear how apoptosis in single-celled organisms might result from evolution by natural selection. However, we speculate that apoptosis may regulate the parasite load of A. taiwanensis within its natural mosquito host, leading to an optimized state of the survival rate for both parasite and host.

Japanese encephalitis virus induces matrix metalloproteinase-9 expression via a ROS/c-Src/PDGFR/PI3K/Akt/MAPKs-dependent AP-1 pathway in rat brain astrocytes.

BACKGROUND: Japanese encephalitis virus (JEV) infection is a major cause of acute encephalopathy in children, which destroys central nervous system (CNS) cells, including astrocytes and neurons. Matrix metalloproteinase (MMP)-9 has been shown to degrade components of the basal lamina, leading to disruption of the blood-brain barrier (BBB) and to contribute to neuroinflammatory responses in many neurological diseases. However, the detailed mechanisms of JEV-induced MMP-9 expression in rat brain astrocytes (RBA-1 cells) are largely unclear. METHODS: In this study, the effect of JEV on expression of MMP-9 was determined by gelatin zymography, western blot analysis, RT-PCR, and promoter assay. The involvement of AP-1 (c-Jun and c-Fos), c-Src, PDGFR, PI3K/Akt, and MAPKs in these responses were investigated by using the selective pharmacological inhibitors and transfection with siRNAs. RESULTS: Here, we demonstrate that JEV induces expression of pro-form MMP-9 via ROS/c-Src/PDGFR/PI3K/Akt/MAPKs-dependent, AP-1 activation in RBA-1 cells. JEV-induced MMP-9 expression and promoter activity were inhibited by pretreatment with inhibitors of AP-1 (tanshinone), c-Src (PP1), PDGFR (AG1296), and PI3K (LY294002), and by transfection with siRNAs of c-Jun, c-Fos, PDGFR, and Akt. Moreover, JEV-stimulated AP-1 activation was inhibited by pretreatment with the inhibitors of c-Src, PDGFR, PI3K, and MAPKs. CONCLUSION: From these results, we conclude that JEV activates the ROS/c-Src/PDGFR/PI3K/Akt/MAPKs pathway, which in turn triggers AP-1 activation and ultimately induces MMP-9 expression in RBA-1 cells. These findings concerning JEV-induced MMP-9 expression in RBA-1 cells imply that JEV might play an important role in CNS inflammation and diseases.

A genome-sequence survey for Ascogregarina taiwanensis supports evolutionary affiliation but metabolic diversity between a Gregarine and Cryptosporidium.

We have performed a whole-genome-sequence survey for the gregarine, Ascogregarina taiwanensis and herein describe both features unique to this early diverging apicomplexan and properties that unite it with Cryptosporidium, the Coccidia, and the Apicomplexa. Phylogenetic trees inferred from a concatenated protein sequence comprised of 10,750 amino acid positions, as well as the large subunit rRNA genes, robustly support phylogenetic affinity of Ascogregarina with Cryptosporidium at the base of the apicomplexan clade. Unlike Cryptosporidium, Ascogregarina possesses numerous mitochondrion-associated pathways and proteins, including enzymes within the Krebs cycle and a cytochrome-based respiratory chain. Ascogregarina further differs in the capacity for de novo synthesis of pyrimidines and amino acids. Ascogregarina shares with Cryptosporidium a Type I fatty acid synthase and likely a polyketide synthase. Cryptosporidium and Ascogregarina possess a large repertoire of multidomain surface proteins that align it with Toxoplasma and are proposed to be involved in coccidian-like functions. Four families of retrotransposable elements were identified, and thus, retroelements are present in Ascogregarina and Eimeria but not in other apicomplexans that have been analyzed. The sum observations suggest that Ascogregarina and Cryptosporidium share numerous molecular similarities, not only including coccidian-like features to the exclusion of Haemosporidia and Piroplasmida but also differ from each other significantly in their metabolic capacity.

Autoimmunity-related demyelination in infection by Japanese encephalitis virus.

Japanese encephalitis (JE) virus is the most common cause of epidemic viral encephalitis in the world. The virus mainly infects neuronal cells and causes an inflammatory response after invasion of the parenchyma of the brain. The death of neurons is frequently observed, in which demyelinated axons are commonly seen. The mechanism that accounts for the occurrence of demyelination is ambiguous thus far. With a mouse model, the present study showed that myelin-specific antibodies appeared in sera, particularly in those mice with evident symptoms. Meanwhile, specific T cells proliferating in response to stimulation by myelin basic protein (MBP) was also shown in these mice. Taken together, our results suggest that autoimmunity may play an important role in the destruction of components, e.g., MBP, of axon-surrounding myelin, resulting in demyelination in the mouse brain after infection with the JE virus.

Life as a Vector of Dengue Virus: The Antioxidant Strategy of Mosquito Cells to Survive Viral Infection.

Dengue fever is a mosquito-borne viral disease of increasing global importance. The disease has caused heavy burdens due to frequent outbreaks in tropical and subtropical areas of the world. The dengue virus (DENV) is generally transmitted between human hosts via the bite of a mosquito vector, primarily Aedes aegypti and Ae. albopictus as a minor species. It is known that the virus needs to alternately infect mosquito and human cells. DENV-induced cell death is relevant to the pathogenesis in humans as infected cells undergo apoptosis. In contrast, mosquito cells mostly survive the infection; this allows infected mosquitoes to remain healthy enough to serve as an efficient vector in nature. Overexpression of antioxidant genes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), glutaredoxin (Grx), thioredoxin (Trx), and protein disulfide isomerase (PDI) have been detected in DENV2-infected mosquito cells. Additional antioxidants, including GST, eukaryotic translation initiation factor 5A (eIF5a), and p53 isoform 2 (p53-2), and perhaps some others, are also involved in creating an intracellular environment suitable for cell replication and viral infection. Antiapoptotic effects involving inhibitor of apoptosis (IAP) upregulation and subsequent elevation of caspase-9 and caspase-3 activities also play crucial roles in the ability of mosquito cells to survive DENV infection. This article focused on the effects of intracellular responses in mosquito cells to infection primarily by DENVs. It may provide more information to better understand virus/cell interactions that can possibly elucidate the evolutionary pathway that led to the mosquito becoming a vector.

Upregulation of a novel eukaryotic translation initiation factor 5A (eIF5A) in dengue 2 virus-infected mosquito cells.

BACKGROUND: Dengue virus, a mosquito-borne flavivirus, is the etiological agent of dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. It generally induces apoptosis in mammalian cells, but frequently results in persistent infection in mosquito cells. That mechanism remains to be explored. In turn, a genomic survey through subtractive hybridization (PCR-select cDNA subtraction) was conducted in order to find gene(s) that may play a role in interactions between the virus and its host cells. RESULTS: Through this technique, we identified a novel eukaryotic translation initiation factor 5A (eIF5A) which is upregulated in Aedes albopictus-derived C6/36 cells infected by the type 2 dengue (Den-2) virus. The full-length of the identified eIF5A gene consisted of 1498 bp of nucleotides with a 41.39% G+C content, and it possessed a higher similarity and shorter evolutionary distance with insects than with other organisms. Upregulation of eIF5A in response to Den-2 virus infection was validated at both the RNA and protein levels. This phenomenon was also observed by confocal microscopy. In addition, cell death obviously occurred when eIF5A activity was inhibited in C6/36 cells even when they were infected by the virus. However, viral multiplication was not obviously affected in infected C6/36 cells when eIF5A activity was reduced. CONCLUSIONS: Taken together, we postulated that eIF5A plays a role in preventing mosquito cells from death in response to Den-2 viral infection, thus facilitating continued viral growth and potential persistent infection in mosquito cells. It would be worthwhile to further investigate how its downstream factors or cofactors contribute to this phenomenon of dengue infection.

Cell-to-Cell Spread of Dengue Viral RNA in Mosquito Cells.

Dengue virus (DENV) is an important mosquito-borne arbovirus that is particularly prevalent in tropical and subtropical areas of the world. The virus is generally ingested with a blood meal, replicates in host tissues, and disseminates into salivary glands for transmission to the next host. Membrane-bound vacuoles carrying DENV particles have been documented in mosquito cells and play a role in the cell-to-cell transmission of DENV2. C189 is one member of the tetraspanin family and generally increases its expression as one component of the vacuoles (C189-VCs) within C6/36 cells infected with DENV2. In the present study, we have further demonstrated via sucrose gradient centrifugation as well as magnetic immune isolation (MI) that the RNA of DENV2 was eventually carried by C189-VCs. In addition, viral RNA was shown to spread from donor to recipient cells in a coculture assay even when 20 mM NH4Cl was added to inhibit virus replication in the culture. In an alternate assay using the transwell system, viral RNA was only detected in recipient cells in the absence of 40 mM NH4Cl, suggesting that cell-cell contact is required for the intercellular spread of DENV2. In turn, the formation of viral synapse (VS) derived from aggregates of viral particles was frequently observed at sites of cell contact. Taken together, the formation of C189-VCs in C6/36 cells is induced by DENV2 infection, which may serve as a vehicle for transferring virions and also viral RNA to neighboring cells by cell-to-cell transmission after cell-cell contact. This finding provides insight into the understanding of viral spread between mosquito cells. It may also elucidate the benign persistent infection in mosquito cells and efficient dissemination of DENV infection within a mosquito vector.

Mosquito larvicidal activities of extractives from black heartwood-type Cryptomeria japonica.

The purpose of this study is to determine the larvicidal activities of ethanolic extracts from leaves, wood, and bark of black heartwood-type Cryptomeria japonica against fourth-instar larvae of mosquitoes Aedes aegypti and Aedes albopictus. Among three ethanolic extracts from C. japonica, wood extract exhibited the best larvicidal activity against A. aegypti and A. albopictus with LC(50) values of 63.2 and 93.8 microg/ml, respectively. Four major compounds, including ferruginol, epi-cubebol, cubebol, and isopimarol, were isolated from wood extract, and it was demonstrated that cubebol exhibited the best activity against A. aegypti and A. albopictus with LC(50) values of 60.1 and 50.0 microg/ml, respectively. Our findings showed that the wood extract and cubebol from C. japonica have good potential as a source for natural larvicides.

Insecticidal activities of leaf and twig essential oils from Clausena excavata against Aedes aegypti and Aedes albopictus larvae.

BACKGROUND: The current study investigates, for the first time, the mosquito larvicidal activities of leaf and twig essential oils from Clausena excavata Burm. f. and their individual constituents against Aedes aegypti L. and Aedes albopictus Skuse larvae. The yields of essential oils obtained from hydrodistillation were compared, and their constituents were determined by GC-MS analyses. RESULTS: The LC(50) values of leaf and twig essential oils against fourth-instar larvae of Ae. aegypti and Ae. albopictus were 37.1-40.1 microg mL(-1) and 41.1-41.2 microg mL(-1) respectively. This study demonstrated that C. excavata leaf and twig essential oils possess mosquito larvicidal activity, inhibiting the growth of mosquito larvae for both species at a low concentration. In addition, results of larvicidal assays showed that the effective constituents in leaf and twig essential oils were limonene, gamma-terpinene, terpinolene, beta-myrcene, 3-carene and p-cymene. The LC(50) values of these constituents against both mosquito larvae were below 50 microg mL(-1). Among these effective constituents, limonene had the best mosquito larvicidal activity, with LC(50) of 19.4 microg mL(-1) and 15.0 microg mL(-1) against Ae. aegypti and Ae. albopictus larvae respectively. CONCLUSION: The findings suggested that the essential oils from Clausena excavata leaf and twig and their effective constituents may be explored as a potential natural larvicide.

The blood-brain barrier in the cerebrum is the initial site for the Japanese encephalitis virus entering the central nervous system.

Japanese encephalitis (JE) virus is a member of the encephalitic flaviviruses and frequently causes neurological sequelae in a proportion of patients who survive the acute phase of the infection. In the present study, we molecularly identified viral infection in the brain of mice with rigidity of hindlimbs and/or abnormal gait, in which JE virus particles appeared within membrane-bound vacuoles of neurons throughout the central nervous system. Deformation of tight junctions (TJs) shown as dissociation of endothelial cells in capillaries, implying that the integrity of the blood-brain barrier (BBB) has been compromised by JE virus infection. BBB permeability evidently increased in the cerebrum, but not in the cerebellum, of JE virus-infected mice intravenously injected with the tracer of Evans blue dye. This suggests that the permeability of the BBB differentially changed in response to viral infection, leading to the entry of JE virions and/or putatively infected leukocytes from the periphery to the cerebrum as the initial site of infection in the central nervous system (CNS). Theoretically, the virus spread to the cerebellum soon after the cerebrum became infected.

Larvicidal activity of tectoquinone isolated from red heartwood-type Cryptomeria japonica against two mosquito species.

Mosquito larvicidal activities of methanolic extracts from different plant parts of red heartwood-type Cryptomeria japonica D. Don against the fourth-instar larvae of Aedes aegypti and Aedes albopictus were examined. Results of mosquito larvicidal tests demonstrated that the n-hexane fraction of C. japonica sapwood methanolic extract had an excellent inhibitory effect against the larvae of A. aegypti and A. albopictus and its LC50 values were 2.4 and 3.3 microg/ml, respectively, in 24h. Following the bioactivity-guided fractionation procedure, the active constituent isolated from C. japonica sapwood was characterized as tectoquinone by spectroscopic analyses. The LC50 values of tectoquinone against A. aegypti and A. albopictus in 24h were 3.3 and 5.4 microg/ml, respectively. In addition, comparisons of mosquito larvicidal activity of anthraquinone congeners demonstrated that anthraquinone skeleton with a methyl group at C-2 position, such as tectoquinone, exhibited the strongest mosquito larvicidal activity. Results of this study show that the methanolic extract of C. japonica sapwood may be considered as a potent source and tectoquinone as a new natural mosquito larvicidal agent.

Dengue outbreaks and the geographic distribution of dengue vectors in Taiwan: A 20-year epidemiological analysis.

Dengue fever is an important mosquito-borne viral infectious disease that mostly occurs in tropical and subtropical areas of the world. According to epidemiological data from the Center for Disease Control of Taiwan, more than 98.62% of outbreaks of indigenous total dengue cases were reported in the southern part of Taiwan. Southern Taiwan is an aggregate area encompassing Tainan, Kaohsiung, and Pingtung, all of which are located below the Tropic of Cancer (23º35'N). With a few exceptions, dengue outbreaks mainly occur in southern Taiwan which is highly associated or overlaps with the prevalence of Aedes aegypti. A.aegypti is presumed to be absent from the northern part of Taiwan, while Aedes albopictus breeds in areas throughout the island. According a collection of 20 years of epidemiological data from Taiwan, the inability of A. aegypti to survive the winter weather in northern Taiwan may account for its restricted geographical distribution and that of dengue outbreaks it transmits. A.aegypti, unlike temperate strains of A. albopictus, lacks embryonic diapause signaled by a short photoperiod which thus reduces its cold-hardiness. Therefore it is intolerant of low temperatures that frequently accompany rains and unable to survive during winter in the northern part of Taiwan.

A novel p53 paralogue mediates antioxidant defense of mosquito cells to survive dengue virus replication.

Mosquito cells allow dengue viruses (DENVs) to undergo replication without causing serious deleterious effects on the cells, leading to advantages for dissemination to other cells. Despite this, increased accumulation of reactive oxygen species (ROS) is usually detected in C6/36 cells with DENV2 infection as shown in mammalian cells. Uniquely, oxidative stress caused by the ROS is alleviated by eliciting antioxidant defense which leads to protection of mosquito cells from the infection. In the present study, a novel p53 paralogue (p53-2) was identified and proved to be regulated in C6/36 cells with DENV2 infection. With a gene-knockdown technique, p53-2 was demonstrated to transcribe catalase which plays a critical role in reducing ROS accumulation and the death rate of infected cells. Ecologically, a higher survival rate of mosquito cells is a prerequisite for prosperous production of viral progeny, allowing infected mosquitoes to remain healthy and active for virus transmission.

Functional determinants of NS2B for activation of Japanese encephalitis virus NS3 protease.

Japanese encephalitis virus (JEV) is a mosquito-borne flavivirus, causing severe central nerve system diseases without specific treatments. The NS2B-NS3 protease of flaviviruses mediates several cleavages on the flavivirus polyprotein, being believed to be a target for antiviral therapy. NS2B is the cofactor of the viral serine protease, correlating with stabilization and substrate recognition of the NS3 protease. In this study, we investigate the functional determinants in the JEV NS2B for the activation of the NS3 protease. Cis- and trans-cleavage assays of the deletions at the N-terminal of NS2B demonstrated that the NS2B residues Ser(46) to Ile(60) were the essential region required for both cis and trans activity of the NS3 protease. In addition, alanine substitution at the residues Trp53, Glu55, and Arg56 in NS2B significantly reduced the cis- and trans-cleavage activities of the NS3 protease. Sequence alignment and modeled structures suggested that functional determinants at the JEV NS2B residues Ser46 to Ile60, particularly in Trp53, Glu55 and Arg56 could play an important configuration required for the activity of the flavivirus NS3 protease. Our results might be useful for development of inhibitors that block the interaction between NS2B and NS3.

A novel tetraspanin C189 upregulated in C6/36 mosquito cells following dengue 2 virus infection.

Dengue (Den) viruses cause apoptosis in mammalian cells, but usually result in high progeny yields without evident damage in mosquito cells. By using subtractive hybridization, 13 potentially virus-induced genes were selected in Den-2 virus-infected Aedes albopictus C6/36 cells. Based on semi-quantitative and real-time RT-PCR, one novel gene, named C189, was significantly upregulated in infected C6/36 cells. Its full-length of 678 nucleotides (nt) was determined by a combination of 5'- and 3'-RACE products. After alignment, C189 was classified as a member of the tetraspanin superfamily that typically has 2 short cytoplasmic sequences, 4 transmembrane domains, as well as small and large extracellular regions (EC1 and EC2). It contains the hallmark CCG motif in the EC2 region and additional 17 conserved nucleotides as do other tetraspanins. C189 was not upregulated by inoculation of UV-inactivated Den-2 virus to C6/36 cells. This suggests that tetraspanin upregulation is not related to virus binding to the cell surface, and that C189 does not function as a receptor for dengue virus entry. On the other hand, overexpression of C189 was concurrent with viral proteins, targeting the plasma membrane of C6/36 cells infected with Den-2 virus. It is presumably beneficial or essential for cell-to-cell spread of the virus due to the role of tetraspanins demonstrated in intercellular adhesion.

The p53 gene with emphasis on its paralogues in mosquitoes.

The p53 gene is highly important in human cancers, as it serves as a tumor-suppressor gene. Subsequently, two p53 homologues, i.e., p73 and p63, with high identity of amino acids were identified, leading to construction of the p53 family. The p53 gene is highly important in human cancer because it usually transcribes genes that function by causing apoptosis in mammalian cells. In contrast, p63 and p73 tend to be more important in modulating development than inducing cell death, even though they share similar protein structures. Relatively recently, p53 was also identified in mosquitoes and many other insect species. Uniquely, its structure lacks the sterile alpha motif domain which is a putative protein-protein interaction domain and exclusively exists at the C-terminal region in p73 and p63 in mammals. A phylogenetic analysis revealed that the p53 gene derived from mosquitoes is composed of two paralogues, p53-1 and p53-2. Of these, only p53-2 is responsively upregulated by dengue 2 virus (DENV2) in C6/36 cells which usually survive the infection. This indicates that the p53 gene is closely related to DENV infection in mosquito cells. The specific significance of p53-2's involvement in cell survival from virus-induced stress is described and briefly discussed in this report.