Elimination of
viral infections is dependent on rapid recruitment and activation of leukocytes with
antiviral activities to infected areas.
Chemokines constitute a class of
cytokines that have regulatory effects on leukocyte migration and activity. In this study we have studied the role of
CC chemokine receptor 1 (CCR1) and CCR5 in host defense during a generalized herpes simplex virus type 2 (HSV-2)
infection. Whereas both 4- and 8-week-old CCR1(-/-) mice resembled wild-type mice (C57BL/6) with respect to defense against the
infection, significantly higher virus titers were seen in the livers and brains of 4-week-old CCR5(-/-) mice. At the age of 8 weeks, CCR5(-/-) were indistinguishable from wild-type mice and cleared the
infection from liver and spleen. Although 4-week-old CCR5(-/-) mice were able to recruit natural killer (NK) cells to the site of
infection, these cells had reduced cytotoxic activity compared to NK cells from wild-type mice. This was not due to lower production of alpha/
beta interferon or
interleukin-12, two well-described activators of cytotoxic activity in NK cells. We also noted that the spleens of young CCR5(-/-) mice did not increase in size during
infection as did the spleens of wild-type and CCR1(-/-) mice. This observation was accompanied by impaired proliferation of CCR5(-/-) splenocytes (SCs) ex vivo. Moreover, migration of CD8(+) T cells to the liver in response to
infection was impaired in CCR5(-/-) mice, and adoptive transfer of SCs from CCR5(-/-) mice infected for 6 days into newly infected wild-type mice did not improve
antiviral activity in the liver, in contrast to what was seen in mice receiving immune SCs from wild-type mice. Altogether, this study shows that CCR5 plays an age-dependent role in host defense against HSV-2 by supporting both the innate and adaptive immune response.