Peptide-induced immune protection of CD8+ T cell-deficient mice against Friend retrovirus-induced disease

Abstract

CD8+ CTLs and virus-neutralizing antibodies have been associated with spontaneous and vaccine-induced immune control of retroviral infections. We previously showed that a single immunization with an env gene-encoded CD4+ T cell epitope protected mice against fatal Friend retrovirus infection. Here, we analyzed immune cell components required for the peptide-induced anti-retroviral protection. Mice lacking CD8+ T cells were nevertheless protected against Friend virus infection, while mice lacking B cells were not. Virus-producing cells both in the spleen and bone marrow decreased rapidly in their number and became undetectable by 4 weeks after infection in the majority of the peptide-immunized animals even in the absence of CD8+ T cells. In the vaccinated animals the production and class switching of virus-neutralizing and anti-leukemia cell antibodies were facilitated; however, virus-induced erythroid cell expansion was suppressed before neutralizing antibodies became detectable in the serum. Further, the numbers of virus-producing cells in the spleen and bone marrow in the early stage of the infection were smaller in the peptide-immunized than in unimmunized control mice in the absence of B cells. Thus, peptide immunization facilitates both early cellular and late humoral immune responses that lead to the effective control of the retrovirus-induced disease, but CD8+ T cells are not crucial for the elimination of virus-infected cells in the peptide-primed animals.

Persistence of Viremia and Production of Neutralizing Antibodies Differentially Regulated by PolymorphicAPOBEC3andBAFF-RLoci in Friend Virus-Infected Mice

“…Two days later, the cells were washed twice with phosphatebuffered balanced salt solution (PBBS) and fixed with methanol. F-MuLVinfected cell foci were stained with monoclonal Ab (MAb) 720 (41), which detects the F-MuLV env gene product, and visualized by using biotinylated anti-mouse immunoglobulin (Ig) Ab and avidin-biotinylated peroxidase complex (Vector Laboratories, Burlingame, CA) as described previously (17,27,41). The foci were counted under a magnifier, and the F-MuLV titers of plasma samples were calculated as focus-forming units (FFU) per ml.…”

“…The in vitro assays for quantitative measurement of F-MuLV-neutralizing Abs have been described elsewhere in detail (17,27,47). Mice were bled, and the sera were separated and heat inactivated at 56°C for 30 min.…”

“…However, the mechanisms by which the polymorphisms at the APOBEC3 locus, which encodes the intracellular cytidine deaminase protein, may affect the production of virus-neutralizing Abs remain unclear. Further, the relationship between the production of virus-neutralizing Abs and control of viremia also remains uncertain, as the reduction in the number of virusproducing cells can be observed prior to the detection of virusneutralizing Abs in the serum of vaccinated animals (17,27). The possible causative relationships between the production of virus-neutralizing Abs and clearance of viremia are important, especially because the original Rfv3 phenotypes were defined by the persistence of viremia at PIDs Ͼ30 (4, 5), while the polymorphisms in the genetic markers linked with the APOBEC3 locus affect serum titers of virus-neutralizing Abs at PID 15 (16).…”

Premature Terminal Exhaustion of Friend Virus-Specific Effector CD8+ T Cells by Rapid Induction of Multiple Inhibitory Receptors

“…Abs to the following molecules were purchased from BD Biosciences (CD3, CD4, CD8, Ter119, and CD11b), BioLegend (CD43 [1B11], CD25, PD-1, CD69, CD62L, CD122, CD127, Tim-3, LAG-3, CTLA-4, FasL, TRAIL, PD-L1, PD-L2, CD11c, and FoxP3), or Invitrogen (Carlsbad, CA; granzyme B). Purified anti-F-MuLV gp70 mAb, clone 720 (19), was labeled with biotin by NHS-PEG 4 -Biotin (Thermo Scientific, Waltham, MA), as described (31). Labeled streptavidin was purchased from BioLegend.…”

“…After being washed and fixed with methanol on the second day of coculturing, cells were stained with biotinylated 720 mAb, and F-MuLV-infected foci were visualized using an Elite ABC Kit (Vector Laboratories, Burlingame, CA), as described (31).…”