CD4 and infection: In this study, we generated antigen-specific CD4+ Tfh memory cells using heterologous priming with either intranasal (i.n.)infection with acute lymphocytic choriomeningitis virus (LCMV) or intramuscular (i.m.)immunization with adjuvanted recombinant glycoprotein from LCMV (rGP) prior to intranasal infection with a recombinant mouse-adapted PR8 strain engineered to carry the CD4-immunodominant LCMVgp61-80 epitope (PR8-HA-GP61-80).