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The Friend retroviral (FV) model is used here to investigate the role of CD4 T (Th) cells in recovery from acute FV infection. Depletion of Th cells in high recovery mice leads to fatal erythroleukemia owing to high viral load. CD8 T-cell dependent early recovery from FV infection is Th cell-independent but long-term maintenance of effector and memory CD8 T cells requires Th cell help. Moreover, Th cell help is essential for production of neutralizing antibodies by B cells in response to FV. The peak FV-specific Th cell responses is far greater in magnitude in high recovery mice than intermediate recovery mice, which differ in their MHC-II background. Effector Th cells are able to produce anti-viral IFN- to reduce viral load only until 3 weeks post infection and subsequently lose their anti-viral effector functions due to the presence of Regulatory T (Treg) cells. Depletion of Treg cells increases the frequency of IFN- producing FV-specific Th cells and decreases the viral load further in the infected mice. Considered together, our findings imply that therapeutic manipulation of Treg / Th - cell number and/or function could improve immune control of retroviral infections.

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Dr. Savita Nair is currently a Research Associate in the lab of Dr. Luis J. Sigal at Fox Chase Cancer Center, Philadelphia; USA. She earned her PhD degree under the mentorship of Dr. Ulf Dittmer from University of Duisburg-Essen, Essen; Germany in 2009. The focus of Dr. Nair´s research for the past 12 years is Infection and Immunity.

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