Moreover, research in other viral infections have shownCD4+ T cells with cytotoxic phenotype in Dengue Virus and SARS-CoV-2 [16, 42].Interestingly, those cytotoxic CD4+ T cells express chemokine receptors likeCX3CR1, CCL3, CCL4, and CCL5, which suggests recruitment to the infection site[13, 15–17, 42], and in Meckiff et al [42], the SARS-CoV-2-reactive CD4+ CTLsshowed similar UMAP clustering patterns as our study. Here, CCL4 is linked to viral infectious disease.