Development of a pseudotyped-lentiviral-vector-based neutralization assay for chikungunya virus infection.

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus that causes chikungunya fever in Africa, South Asia, and Southeast Asia. Because the mosquito vector Aedes albopictus is present in habitats across Europe, North America, and East Asia, CHIKV has become a serious worldwide public health concern. Infection with CHIKV typically causes fever, rash, myalgia, and arthralgia. One of the important questions yet to be answered is how the host immune system is involved in the development of this disease. In this study, we prepared a CHIKV-pseudotyped lentiviral vector for use in a safe and convenient neutralization (NT) assay and analyzed its efficacy. The CHIKV-pseudotyped lentiviral vector was prepared by cotransfection with plasmids encoding the CHIKV glycoproteins E3, E2, 6k, and E1, packaging elements, and a luciferase reporter. This alternative to native CHIKV can be safely handled in a biosafety level 2 facility. The NT assay was optimized using sera from CHIKV-immunized mice and then applied to human patient sera. The majority of the serum samples from patients with chikungunya in Thailand showed robust neutralization activities, with titers that were tightly correlated with those determined by a conventional NT assay. Moreover, there was a strong correlation with the CHIKV antibody titers as determined by enzyme-linked immunosorbent assay. Thus, the CHIKV-pseudotyped-lentiviral-vector-based NT assay system is a powerful tool for examining the neutralization activity of patient sera, which will lead to a better understanding of the immune responses involved in CHIKV infection.