Cytotoxic CD4 T Cells function Dengue Virus Infection Dengue virus has spread through most tropical and subtropical areas of the world and represents a serious public health problem. The control of DENV infection has not yet been fully successful due to lack of effective therapeutics or vaccines. Nevertheless, a better understanding of the immune responses against DENV infection may reveal new strategies for eliciting and improving antiviral immunity. T cells provide protective immunity against various viral infections by generating effector cells that cooperate to eliminate antigens and memory cells that can survive for long periods with enhanced abilities to control recurring pathogens. Following activation, CD8 T cells can migrate to sites of infection and kill infected cells, whereas CD4 T cells contribute to the elimination of pathogens by trafficking to infected tissues and providing help to innate immune responses, B cells, as well as CD8 T cells. However, it is now evident that CD4 T cells can also perform cytotoxic functions and induce the apoptosis of target cells. Importantly, accumulating studies demonstrate that cytotoxic CD4 T cells develop following DENV infections and may play a crucial role in protecting the host from severe dengue disease. Dengue virus is a major public health problem in tropical and subtropical areas with 390 million estimated infections per year. DENV has four serotypes, and infection with one of the serotypes can be asymptomatic or result in a range of diseases spanning from Dengue Fever to Dengue Haemorrhagic Fever and Dengue Shock Syndrome. The more severe forms of DHF and DSS are more likely to develop following secondary infections with a different serotype. Other than supportive care there is currently no specific therapy available for the treatment of dengue diseases. Tremendous efforts have been devoted to the development of DENV vaccines since World War II, and a tetravalent chimeric vaccine, Dengvaxia, has recently been licensed in several countries including Mexico, Brazil, and the Philippines. Regards Alex John Editorial Assiatant Clinical Toxicology