Author(s)

Suchada Sukhumvittaya¹, Silawun Ampol¹, Kovit Pattanapanyasat², Wannee Kantakamalakul^1*

¹Department of Microbiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
²Center of Excellence for Flow Cytometry, Office for Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.

Smallpox eradication was successful via prophylactic administration of live attenuated vaccinia virus. As a result of the discontinuation of the smallpox immunization program, many individuals are now susceptible to smallpox virus infection should it be used as a biological weapon. Presently, only individuals at high risk for exposure are required to receive smallpox vaccine, such as laboratory personnel that handle variola/vaccinia virus. This study endeavored to investigate a one-year period of vaccinia virus-specific T cell responses using polychromatic flow cytometry and neutralizing (Nt) antibody responses using plaque reduction neutralization test (PRNT) in individuals receiving primary immunization (n = 5) with ACAM2000^TM smallpox vaccine. Functional and phenotypic profiles of vaccinia virus-specific T cell responses were characterized. Each single functional measurement {CD107a/b expression, production of interferon g (IFN-g), macrophage inflammatory protein 1b (MIP-1b), interleukin 2 (IL-2), and tumor necrosis factor a (TNF-a)} demonstrated that vaccinia virus-specific CD8⁺ T cells were functional at least one time point after vaccination (p ≤ 0.05). However, vaccinia virus-specific CD4⁺ T cells were functional only for MIP-1b production (p ≤ 0.05). Vaccinia virus-specific CD8⁺ T cells induced in these individuals showed increased polyfunctionality in at least 2 phenotypes relative to pre-vaccination (p ≤ 0.05). Although only three of five individuals (60%) showed positive Nt antibody (titer ≥ 20) at first month after vaccination, all five individuals (100%) demonstrated Nt antibody at 2 months, post-immunization. Interestingly, all vaccinees could retain the Nt antibody for 6 months after primary vaccination. In conclusion, ACAM2000^TM smallpox vaccine induced both polyfunctional T cell-and Nt antibody-responses in primary immunized individuals.

Smallpox Vaccine, Primary Immunization, T Cell, Neutralizing Antibody

Sukhumvittaya, S. , Ampol, S. , Pattanapanyasat, K. and Kantakamalakul, W. (2016) Polyfunctional T Cell and Neutralizing Antibody Responses to ACAM2000^TM Smallpox Vaccine Immunization in Primary-Vaccinated Individuals. Advances in Microbiology, 6, 169-177. doi: 10.4236/aim.2016.63017.