Takashi Kaneshima

Vaccine efficacy of a cell lysate with recombinant baculovirus-expressed feline infectious peritonitis (FIP) virus nucleocapsid protein against progression of FIP.

Abstract The Type II feline infectious peritonitis virus (FIPV) infection of feline macrophages is enhanced by a monoclonal antibody (MAb) to the S protein of FIPV. This antibody-dependent enhancement (ADE) activity increased with the MAb that showed a neutralizing activity with feline kidney cells, suggesting that there was a distinct correlation between ADE activity and the neutralizing activity. The close association between enhancing and neutralizing epitopes is an obstacle to developing a vaccine containing only neutralizing epitopes without enhancing epitopes. In this study, we immunized cats with cell lysate with recombinant baculovirus-expressed N protein of the Type I FIPV strain KU-2 with an adjuvant and investigated its preventive effect on the progression of FIP. Cats immunized with this vaccine produced antibodies against FIPV virion-derived N protein but did not produce virus-neutralizing antibodies. A delayed type hypersensitivity skin response to N protein was observed in these vaccinated cats, showing that cell mediated immunity against the FIPV antigen was induced. When these vaccinated cats were challenged with a high dose of heterologous FIPV, the survival rate was 75% (6/8), while the survival rate in the control group immunized with SF-9 cell-derived antigen was 12.5% (1/8). This study showed that immunization with the cell lysate with baculovirus-expressed N protein was effective in preventing the progression of FIP without inducing ADE of FIPV infection in cats.

CD8+ T cells from feline immunodeficiency virus (FIV) infected cats suppress exogenous FIV replication of their peripheral blood mononuclear cells in vitro

Summary. 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.

Ability of CD8+ T Cell Anti-Feline Immunodeficiency Virus Activity Correlated with Peripheral CD4+ T Cell Counts and Plasma Viremia

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.

Isolation of Microsporum gallinae from a fighting cock (Gallus gallus domesticus) in Japan

A case of tinea corporis caused by Microsporum gallinae was found in 2011 in Okinawa, located in the southern part of Japan. The patient was a 96-year-old, otherwise healthy, Japanese man, who had been working as a breeder of fighting cocks for more than 70 years. He was bitten on his right forearm by one of the cocks and a few weeks later, two erythematous macules appeared on the right forearm, accompanied by a slight itchy sensation. While the first isolate of this dermatophyte was recovered from the region by Miyasato et al. in 2011, it was not obtained from the same fighting cock owned by the patient. However, frequent exchanges of fighting cocks and special domestic breeds of chickens related to fighting, mating, and/or bird fairs are common among the fans and breeders. We investigated 238 chickens and 71 fighting cocks in Okinawa and in the suburbs of Tokyo (Chiba, Tokyo, Ibaraki, and Sizuoka). One isolate of M. gallinae from a fighting cock in Chiba Prefecture in the Tokyo metropolitan area exhibited a different genotype, with a single base difference from the patient isolate based on the internal transcribed spacer 1-5.8s-ITS2 regions (ITS1-5.8S-ITS2) of the ribosomal RNA gene sequence. The isolation of M. gallinae from a fighting cock on the mainland of Japan is the first such finding in animals in our country.

Immunohistochemical Cross-Reactivity Between Paracoccidioides sp. from Dolphins and Histoplasma capsulatum

Paracoccidioidomycosis ceti is a cutaneous disease of cetaceans caused by uncultivated Paracoccidioides brasiliensis or Paracoccidioides spp. Serological cross-reactions between paracoccidioidomycosis ceti and paracoccidioidomycosis, paracoccidioidomycosis and histoplasmosis, and paracoccidioidomycosis and coccidioidomycosis have been reported before. The present study aimed to detect immunohistochemical cross-reaction between antibodies to Paracoccidioides sp. and Histoplasma capsulatum, and vice versa. Thirty murine sera, obtained from experimental infections of 6 isolates of H. capsulatum, were reacted with paraffin-embedded yeast-form cells of Paracoccidioides sp. derived from a case of paracoccidioidomycosis ceti in Japan. The murine sera were also reacted with human isolates of H. capsulatum yeast cells, with P. brasiliensis yeast cells, and with fungal cells of Coccidioides posadasii. Three dolphins’ sera from cases of paracoccidioidomycosis ceti, two human sera from patients with paracoccidioidomycosis, and a serum from a healthy person with a history of coccidioidomycosis were used in order to determine that the tested fungal cells reacted properly. Sera derived from mice infected with an isolate of H. capsulatum reacted positively against yeast cells of Paracoccidioides sp., yeast cells of P. brasiliensis, and fungal cells of C. posadasii, while those derived from other strains were negative. The present study recorded for the first time the cross-reaction between the yeast cells of H. capsulatum and antibodies against Paracoccidioides spp., the yeast cells of Paracoccidioides sp. and antibodies against H. capsulatum, the yeast cells of Paracoccidioides sp. and antibodies against Coccidioides sp., and fungal cells of C. posadasii and antibodies against Paracoccidioides spp.