Lancet Infect Dis 7: 306C307. is a viral illness characterized by acute fever coupled with incapacitating, often chronic, arthralgia. Although the fever subsides in 7C10 days, the joint pain varies in intensity and can persist from 3 months to more than 2 years postinfection (reviewed in ref 1). Before 2005, CHIKF disease manifestations were poorly characterized and clinical features were characterized mainly based on reports documented in the 1970s.2 Since 2005, the etiologic agent, chikungunya virus (CHIKV), has spread and devastated millions throughout the Indian Ocean islands, Europe, India,3C5 and other parts of Asia, and more recently, the South Pacific region and Americas (reviewed in ref 6C8). Chikungunya virus was endemic in India at least since 1958 and probably caused periodic outbreaks much earlier,9 causing epidemics every two to three decades10C12 with relatively few cases reported during interepidemic periods. The first Indian outbreak was documented in 1963 in Calcutta (now Kolkata),13 followed by Picroside II epidemics in Tamil Nadu, Andhra Pradesh, and Maharashtra14,15; the last outbreak during the twentieth century was recorded in Maharashtra in 1973.16 Picroside II Then, India again experienced major outbreaks from 2005 Picroside II to 2010.17C20 After 2010, the country experienced a drastic decline in the number of reported cases,20,21 raising the question of whether this infection was at the end of its transmission wave in India. However, in 2016, India reeled under a massive outbreak, with 64,057 cases confirmed across the country.20 We conducted a prospective study to investigate the evolution of CHIKV in India since 2010. As part of this study, we previously performed a detailed analysis of the medical, serological, and virological aspects of CHIKF in individuals between 2010 and 2013.11 Clinical aspects of the CHIKF outbreak in 2016 have also been recently reported.12 During the analysis of the samples from your 2016 outbreak, we were intrigued from the distinctions in disease results between 2010 and 2016 outbreaks. To study these putative variations between the 2010 and 2016 outbreaks in greater detail, we carried out detailed, comparative analyses of the viremia, antibody development, neutralization patterns, and sequelae intensities. We also sequenced the complete genomes of several isolates collected during each outbreak and recognized sequence variants that correlated with disease end result. We then compared the pathogenesis of the 2010C2016 outbreak viruses in type I interferon receptorCdeficient (A129) and immunocompetent C57BL/6J mice. Our results demonstrate special features in the neutralization patterns of human being antibodies induced during the two outbreaks, which may Picroside II possess implications for pathogenesis. We also recognized a correlation between strain-specific mutations and sequelae. Finally, pathogenicity studies using mouse models exposed a strain-dependent pattern in virulence. MATERIALS AND METHODS Study site. A prospective study to evaluate the development of CHIKV in India was carried out in New Delhi (28.6139N, 77.2090E). Samples were collected in the Vardhman Mahavir Medical College and Safdarjung Hospital (VMMC and SH), a teaching institution and a multispecialty hospital with 1,600 mattresses that serves as a referral hospital during outbreak situations. Study design, participants, and medical assessment. Samples were collected from a cohort of individuals with laboratory-confirmed acute CHIKF, who wanted care at the hospital during the 2010 and 2016 outbreaks during the prospective study.11,12 Confirmation of all recruited individuals in various wards and outpatient departments was carried out on the basis of qualitative IgM ELISA and reverse transcription polymerase chain reaction (RT-PCR) for patient sera collected until day time 5 post-onset of fever. Medical histories, including signs and symptoms, and laboratory findings during the acute phase of illness were Rabbit Polyclonal to Pim-1 (phospho-Tyr309) recorded in the medical report form (CRF) utilized for downstream analyses. Wherever possible, a follow-up was performed 12 weeks after the acute episode by a qualified rheumatologist, and a visual analogue score (VAS) was assigned on a level of 1C10 on the basis of questions related to the intensity of pain posed to the individuals. Once confirmed and recruited, the patient sera were transferred to the laboratory for semiquantitative IgM and IgG analysis along with their neutralizing capacities, and Detection of CHIKV by reverse transcriptionCquantitative polymerase chain reaction (RT-qPCR) and further experiments is as detailed in Number 1. Open in a separate window Number 1. Study design. Study design, inclusive of stepwise quantity of Picroside II samples available and tests.