Determinants of memory in experimental filarial infections in mice

In this communication, we examine the determinants and duration of memory responses against filarial parasites using an intraperitoneal mouse model of Brugia pahangi infection. We assessed the role of T cells in the memory response against B. pahangi larvae by transferring splenic T cells from wild-type mice primed with L3 into T-cell-deficient mice. We found that mice reconstituted with primed T cells cleared intraperitoneal infections with infective larvae in an accelerated manner. To determine the components that may be responsible for the memory response, we transferred unfractionated T cells or purified CD4 ⁺ T cells or CD8⁺ T cells from BALB/cByJ mice primed a month earlier with L3 into T-cell-deficient BALB/c TCRβ ^-/- mice. Recipients were challenged 10 days after adoptive transfer. Our data demonstrated that while either CD4⁺ or CD8⁺ T cells are able to confer some level of protection, both are required for an optimal recall response. To evaluate the longevity of the memory response, we primed several groups of wild-type mice at different times over a year. These mice were then challenged with a single injection of B. pahangi L3. The gap between the priming and second injections of larvae ranged between 4 and 60 weeks. We found that the memory responses in BALB/cByJ mice lasted over a year whereas those in C57BL/6 mice waned more rapidly.