The effect of immunization on chemokines and CCR5 and CXCR4 coreceptor functions in SIV binding and chemotaxis

The replication of simian immunodeficiency virus (SIV) in acutely infected CD4+ cells can be inhibited in vitro by CD8-suppressor factors (SF) and beta-chemokines induced by immunization of macaques with SIV gp120 and p27 in Alum. A comparison between intradermal, naso-rectal-i.m. and targeted iliac lymph node (TILN) routes showed that immunization by the TILN route elicited the most significant increase in CD8-SF and the beta-chemokines RANTES, MIP-1alpha and MIP-1beta. Increased CD8-SF and beta-chemokines were induced not only in PBMC but also in iliac lymph nodes and spleen of the TILN immunized macaques. Furthermore, CD8-SF and the concentrations of RANTES, MIP-1alpha and MIP-1beta increased with secondary immunizations, suggesting that memory CD8+ cells are involved. Treatment of CD8+ cell culture supernatant with antibodies to RANTES, MIP-1alpha and MIP-1beta neutralized the CD8-SF activity, indicating that blocking the CCR5 by these ligands played an important part in the CD8-SF activity elicited by TILN immunization. Indeed, blocking CCR5 with monoclonal antibodies inhibited SIV replications and MIP-1beta mediated chemotaxis. In contrast, SDF-1 or MAb to CXCR4 failed to suppress SIV replication. However, SDF-1 was able to induce simian PBMC chemotaxis and MAb to CXCR4 inhibited SDF-1 mediated chemotaxis. These results suggest that immunization in macaques induces CD8-SF and beta-chemokines which may prevent SIV infection by blocking the CCR5 coreceptors both in circulating cells and in the rectal and genital draining lymph node cells.