Dear Editor,
We read the publication on “Molecular characterization and phylogenetic analysis of Chikungunya virus (CHIKV) from Delhi, India” with great interest. Tandel et al1 concluded that “Actively searching for the potential epidemic causing mutations and reporting of novel mutations may help in better understanding and probably forecasting of future CHIKV outbreaks and its nature.” We agree that the molecular characterization study is useful in epidemiological aspect. The study also gives the new information on microbiological genetics if a new mutation is detected. Nevertheless, whether the study is useful for prediction of outbreak should be discussed. Indeed, mutation of the virus can occur at any times. Numerous mutations can be expected but the clinical problem is observable only if a sense mutation occurs. The molecular characterization study with additional phylogenetic analysis can help determine the occurrence of mutation, which might be a new one, and compare the similarity with the known virus. Nevertheless, the process cannot help predict the possible pathological function due to mutation at all. If one would like to assess the function of the new mutation, a further expressional analysis study is required. In addition, the host and environmental factors might also influence the virus. Butt et al.2 recently noted that “although mutation pressure dominates codon usage in CHIKV, patterns of codon usage in CHIKV are also under the influence of natural selection from its hosts and geography.”
Conflicts of interest
The authors have none to declare.
References
- 1.Tandel K., Kumar M., Shergill S.P.S., Sahai K., Gupta R.M. Molecular characterization and phylogenetic analysis of Chikungunya virus from Delhi, India. Med J Armed Forces India. 2019 Jul;75:266–273. doi: 10.1016/j.mjafi.2018.02.004. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Butt A.M., Nasrullah I., Tong Y. Genome-wide analysis of codon usage and influencing factors in chikungunya viruses. PLoS One. 2014 Mar 4;9 doi: 10.1371/journal.pone.0090905. [DOI] [PMC free article] [PubMed] [Google Scholar]
References
Reply.
We thank the readers for the keen interest shown in the article.
Aedes albopictus is widespread in India, with an especially high density of mosquitoes in South India. Humans are the major reservoir of chikungunya virus (CHIKV) for mosquitoes, which transmit the disease by biting an infected person to others. Thus, the onset and extent of the CHIKV epidemic in India are a prospective threat. Our review of literature showed that outbreaks in the ocean regions, which were unprecedented in magnitude, were due to a mutation in the E1 protein of CHIKV (A226V), which helped in the adaptation of the virus to A. albopictus.1, 2, 3
Recently, a study on mosquitoes (A. albopictus) using both wild (E1: 226A) and mutant (E1: A226V) viruses revealed that the mutant strain is better adapted and possesses higher epidemic potential with increased transmissibility. The E1: A226V mutation in CHIKV results in increased fitness in A. albopictus mosquitoes with respect to midgut infectivity, dissemination to the salivary glands, and transmission of vertebrate species.4
The aforementioned facts from the article quoted make it clear that E1:A226V mutation can cause outbreaks of a higher magnitude than in previous years. This underscores the requirement improving the surveillance systems to include screening for and expression analysis of the mutations observed.
References
- 1.Singh R.K., Tiwari S., Mishra V.K., Tiwari R., Dhole T.N. Molecular epidemiology of Chikungunya virus: mutation in E1 gene region. J Virol Methods. 2012;185:213–220. doi: 10.1016/j.jviromet.2012.07.001. [DOI] [PubMed] [Google Scholar]
- 2.Mishra B., Ratho R.K. Chikungunya re-emergence: possible mechanisms. Lancet. 2006;368:918. doi: 10.1016/S0140-6736(06)69370-7. [DOI] [PubMed] [Google Scholar]
- 3.Schuffenecker I., Iteman I., Michault A. Genome microevolution of Chikungunya viruses causing the Indian Ocean outbreak. PLoS Med. 2006;3:e263. doi: 10.1371/journal.pmed.0030263. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Tsetsarkin K.A., Vanlandingham D.L., McGee C.E., Higgs S. A single mutation in Chikungunya virus affects vector specificity and epidemic potential. PLoS Pathog. 2007;3 doi: 10.1371/journal.ppat.0030201. [DOI] [PMC free article] [PubMed] [Google Scholar]