This study identifies mechanisms mediating responses to immune checkpoint inhibitors using mouse models of triple-negative breast cancer. By creating new mammary tumor models, we find that tumor mutation burden and specific immune cells are associated with response. Further, we developed a rich resource of single-cell RNA-seq and bulk mRNA-seq data of immunotherapy-treated and non-treated tumors from sensitive and resistant murine models. Using this, we uncover that immune checkpoint therapy induces T follicular helper cell activation of B cells to facilitate the anti-tumor response in these models. We also show that B cell activation of T cells and the generation of antibody are key to immunotherapy response and propose a new biomarker for immune checkpoint therapy. In total, this work presents resources of new preclinical models of breast cancer with large mRNA-seq and single-cell RNA-seq datasets annotated for sensitivity to therapy and uncovers new components of response to immune checkpoint inhibitors.

Herpes simplex virus (HSV) infection is a classic example of latent viral infection in humans and

The effect of glycoprotein K (gK) overexpression on herpes simplex virus type 1 (HSV-1) infection in two different strains of mice was evaluated using a recombinant HSV-1 virus that expresses two additional copies of the gK gene in place of the latency-associated transcript (LAT). This mutant virus (HSV-gK ؉ T-cell response. Taken together, these results strongly suggest that increased gK levels promote eye disease and chronic infection in infected mice.

Herpes simplex virus type 1 (HSV-1) is a large (152-kb) double-stranded DNA virus with neurotropic properties. HSV-1 establishes lifelong latent infections in host sensory neurons. This virus is wide spread in the general population. When the eye is infected, the virus travels up nerves and establishes latent infection in neurons of the trigeminal ganglia (TG). During neuronal latency, HSV-1 has no apparent impact on the infected individual. The latent virus can reactivate at various times throughout the life of the individual. This occurs through a mechanism(s) that is currently not completely understood. HSV-1 reactivation in the TG results in virus returning to the eye via the same route previously used to get from the eye to the TG. At the eye, reactivated HSV-1 can produce recurrent disease. Recurrent HSV-1 infection in the eye can cause corneal scarring leading to loss of vision. As a result, HSV-1 is one of the most common infectious causes of corneal blindness in the developed world.During neuronal latency, LAT (latency-associated transcript) is the only abundantly transcribed viral gene (30, 37). The primary LAT transcript is ca. 8.3 kb long (7, 45) and overlaps two viral genes, ICP0 and ICP34.5, in an antisense direction (30,37). A very stable intron, the 2-kb LAT is spliced from the primary transcript (9) and is the major LAT RNA detected during latency (7,33,36,(42)(43)(44).LAT enhances the induced and spontaneous reactivation phenotypes in the rabbit ocular model (12, 21) and the induced reactivation phenotype in mice (1a, 6, 19, 26, 31, 35). The reduced reactivation phenotypes of LAT Ϫ mutants does not necessarily imply that LAT is directly involved in the molecular mechanism of HSV-1 reactivation from latency. LAT might enhance reactivation by increasing the initial amount of latency established and/or by maintaining a high level of latently infected neurons. The larger pool of latently infected neurons and/or the larger pool of neurons containing high copy numbers of the HSV-1 genome would be expected to increase reactivation. Several reports have, in fact, shown that in experimentally infected animals more neurons become latently infected with LAT ϩ viruses compared to LAT Ϫ viruses (29,31,40). In addition, we have recently shown that LAT has anti-* Corresponding author. Mailing address:

A hallmark of infection with herpes simplex virus type 1 (HSV-1) is the establishment of latency in ganglia of the infected individual. During the life of the latently infected individual, the virus can occasionally reactivate, travel back to the eye, and cause recurrent disease. Indeed, a major cause of corneal scarring (CS) is the scarring induced by HSV-1 following reactivation from latency. In this study, we evaluated the relationship between the amount of CS and the level of the HSV-1 latency-associated transcript (LAT) in trigeminal ganglia (TG) of latently infected mice. Our results suggested that the amount of CS was not related to the amount of virus replication following primary ocular HSV-1 infection, since replication in the eyes was similar in mice that did not develop CS, mice that developed CS in just one eye, and mice that developed CS in both eyes. In contrast, mice with no CS had significantly less LAT, and thus presumably less latency, in their TG than mice that had CS in both eyes. Higher CS also correlated with higher levels of mRNAs for PD-1, CD4, CD8, F4/80, interleukin-4, gamma interferon, granzyme A, and granzyme B in both cornea and TG. These results suggest that (i) the immunopathology induced by HSV-1 infection does not correlate with primary virus replication in the eye; (ii) increased CS appears to correlate with increased latency in the TG, although the possible cause-and-effect relationship is not known; and (iii) increased latency in mouse TG correlates with higher levels of PD-1 mRNA, suggesting exhaustion of CD8 ؉ T cells.