Feline immunodeficiency virus (FIV) isolates from domestic cats have been classified into five subtypes, designated A, B, C, D and E. Although many FIV-infected cats may have frequent contact with multiple strains of FIV, they usually become infected with a single FIV subtype. In the present study, we demonstrate that peripheral blood mononuclear cells (PBMC) of FIV infected cats were resistant to exogenous FIV (second virus) replication in vitro and that the resistance of these PBMC was mediated by CD8+ T cells. In cats with a low anti-FIV activity of CD8+ T cells, the proviral DNA of the second virus inoculated into PBMC was detected intracellularly, and both the second and the originally infecting strain (original virus) were produced in the culture supernatant. In contrast, in cats with a high anti-FIV activity of CD8+ T cells, both the proviral DNA of the second virus and the original virus were detected in PBMC intracellularly, but neither virus was produced in the culture supernatant. However, when PBMCs from these cats were depleted of CD8+ T cells, the RNA of both viruses was detected in the culture supernatant. These results suggest that CD8+ T cells inhibit the late phase of FIV replication after viral integration. Moreover, the inhibition was also effective against FIV strains of different subtypes from that of the original strain. It appears that the CD8+ T cell-mediated immune response plays important roles in the maintenance of an asymptomatic state in FIV-infected cats and their resistance to superinfection.

Antibodies to Encephalitozoon cuniculi were examined by enzyme-linked immunosorbent assay using E. cuniculi PTP2 recombinant protein and by Western blot analysis on a total of 472 dog serum samples that had been collected in Japan. Of these samples, 21.8% (103/472) had antibodies against E. cuniculi. Each of 5 serum samples that showed high (>1.0) or low (<0.1) OD value was selected randomly and further examined by Western blot using E. cuniculi-native antigens. All samples with high OD values reacted with specific E. cuniculi proteins, including an antigen of approximately 35 kDa corresponding with PTP2; sera with low OD values did not recognize this E. cuniculi band. This study is the first to demonstrate the prevalence of E. cuniculi infection in dogs in Japan.

In the host defense mechanism against feline immunodeficiency virus (FIV) infection, CD8+ T cells specifically attack virus‐infected cells and suppress the replication of the virus in a non‐cytolytic manner by secreting soluble factors. In this study, we measured CD8+ T cell anti‐FIV activity in 30 FIV‐infected cats. We investigated its relationship with the number of peripheral blood lymphocytes, particularly the CD4+ T cell and CD8+ T cell counts, and the relationship between anti‐FIV activity and the number of T cells of CD8α+βlo and CD8α+β− phenotypes. A clearly significant correlation was observed between anti‐FIV activity and the number of CD4+ T cells. A weaker anti‐FIV activity was associated with a greater decrease in the number of CD4+ T cells. However, there was no significant correlation between anti‐FIV activity and the number of B or CD8+ T cells. Compared with SPF cats, FIV‐infected cats had significantly higher CD8α+βlo T cell and CD8α+β− T cell counts, but, no significant correlation was observed between these cell counts and anti‐FIV activity. This anti‐FIV activity significantly correlated with plasma viremia, which was detected in cats with a weak anti‐FIV activity. These results suggest that the anti‐FIV activity of CD8+ T cells plays an important role in plasma viremia and the maintenance of CD4+ T cells in the body. It is unlikely that CD8α+βlo or CD8α+β− T cells appearing after FIV infection represent a phenotype of CD8+ cells with anti‐FIV activity.

This study investigated the correlation between the body surface temperature (BST) and core body temperature of ewes and changes in BST during the prepartum stage in pregnant ewes. Four non-pregnant adult ewes were used in the first experiment. The BST of the upper neck, vaginal temperature (VT), and ambient temperature (AT) were measured every 10 min for seven days and analyzed for correlations. The mean (± SD) BST and VT of ewes during the study period were 35.4 ± 1.7°C and 39.1 ± 0.4°C, respectively, with a correlation of r = 0.62, P < 0.001. This finding suggested that the BST was associated with core body temperature in ewes. In the subsequent experiment, seven pregnant ewes in their third trimester were used to evaluate changes in BST measured at the upper neck 72 h before parturition. The mean BST at –24–0 h (0 h = time of parturition) was significantly lower than that at –72– –48 h and –48– –24 h (P < 0.05). The BST tended to decrease toward parturition; all BST measurements at –16– –3 h were significantly lower than those at –72 h (P < 0.05). A clear circadian rhythm in the BST was observed at two days and the day before parturition and an unclear circadian rhythm was observed on the day of parturition. Therefore, these findings indicate that the BST also decreases before parturition, as do vaginal and rectal temperatures.

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