Prevalence of feline viral antibodies in random-source laboratory cats

Over a period of 1973 to 1979, a serologic survey of virus infections was conducted on feline sera collected in four universities which located in different prefectures; Obihiro, Saitama, Kanagawa and Tokyo. A significant hemagglutination-inhibition (HI) antibody titer of 1 : 8 or higher to feline panleukopenia virus (FPLV) was detected in 130 (58%) of the 226 sera used. No remarkable difference in the HI antibody prevalence in cats to FPLV was recognized by years or localities. Of a total of 188 cats tested, 99 (53%) presented positive serum neutralizing (SN) antibody titers to the No. 1 strain of feline calicivirus (FCV). Especially in Kanagawa, 17 (77%) of the 22 cats had positive SN titers. However, only 42 (22%) of the 188 sera showed positive SN titers to the Kyoritsu strain of FCV. Such lower positivity in the cats was observed with 13% in the SN test to human reovirus type 3 (Reo-3). The incidence of positive SN antibodies to feline rhinotracheitis virus (FRV) also remained in low values of 20 to 27% with the exception of high percentage of 86 in Tokyo. The dissemination of FPLV, FRV, FCV and Reo-3 was briefly discussed in relation with the age distribution of viral antibodies in cats.     

Studies of respiratory disease in random-source laboratory dogs: viral infections in unconditioned dogs.

A prospective study was conducted to identify the viruses causing respiratory diseases in unconditioned, random-source dogs. During the quarantine period, respiratory disease occurred in 86 of 167 (52%) dogs, and 34 (21%) died. Most affected dogs had a distemper-like illness which required extensive and prolonged care. Histopathologic studies confirmed the diagnosis of canine distemper in 10 of 12 (83%) fatal infections examined. Sixty-seven of 91 (74%) dogs which arrived without canine distemper antibody became ill, and 30 (32%) died. In contrast, only 16 of 67 (24%) dogs with canine distemper antibody had respiratory disease, and only 3 (4%) died. Parainfluenza SV5 and canine adenovirus--type II were recovered from 27 of 54 and 22 of 54 sick dogs, respectively. Canine herpesviruses, canine coronaviruses, and canine parvoviruses were less frequently isolated. Increased antibody titers to SV5 were found consistently, and rises in titer to the other viruses were demonstrated. Many of the sick dogs were infected with two or more viruses. Although several viral agents were detected during these epizootics, prevention of canine distemper appeared to be the key to controlling severe, prolonged, and often fatal respiratory disease.     

Serologic and virologic surveys on feline herpesvirus and feline calicivirus infections in cats for experimental use

Serologic survey and virus isolation of feline herpesvirus (FHV) and feline calicivirus (FCV) were performed on cats used for research at the Laboratory Animal Research Centre, The University of Tsukuba, over the period from 1978 to 1981. Of the 507 mature and immature cats, 4 months old or older, 102 (20.1%) had HI antibody against FHV and 412 (81.3%) SN antibody against FCV. Some 23 (16.2%) and 76 (53.5%) kittens among 142 younger than 4 months had antibodies against FHV and FCV, respectively. Both the antibodies in kittens were considered to be maternally derived. The FCV antibody rate was especially high in cats weighing 2.5 kg (males) and 2.0 kg (females) or more, which were regarded as 8 to 10 months of age. An attempt was made to isolate the viruses from the oropharynx and conjunctiva of clinically healthy mature or immature cats and kittens. As the result, either one or both of the viruses were isolated from 31 of 75 mature and immature cats, and isolation rates of FHV and FCV were 6.7% and 36.0%, respectively. On the other hand, no virus was detectable in 16 kittens.     

Prevalence of feline leukemia virus infection in random source laboratory cats

Three years of quarantine data involving the prevalence of Feline Leukemia Virus (FeLV) in laboratory cats (Felis catus) was evaluated. Testing was performed using a commercially available ELISA system. Annual prevalence of infection ranged from 5.4 to 10.7% of the 937 cats tested. Results obtained with the enzyme linked immunosorbent assay (ELISA) system compared well with tests performed using an immunofluorescent antibody assay system (IFA). Seasonal periodicity was noted with higher infection rates among animals received in April. Holding period at the supplier and gender did not influence disease prevalence. The availability of a simple test system, the unacceptability of FeLV infected cats for research, the danger of transmission and a higher prevalence of infection than earlier reports indicated that supplier and user evaluation of research cats for FeLV would be prudent.     

Isolation of feline parvovirus from peripheral blood mononuclear cells of cats in northern Vietnam.

Feline parvovirus (FPV) was isolated rather frequently from the peripheral blood mononuclear cells (PBMCs) of cats in northern Vietnam by coculturing with MYA-1 cells (an interleukin-2-dependent feline T lymphoblastoid cell line) or Crandell feline kidney (CRFK) cells (a feline renal cell line). Efficiency of virus isolation was higher in MYA-1 cells than in CRFK cells. Interestingly, among the 17 cats from which FPV was isolated, 9 cats were positive for virus neutralizing (VN) antibody against FPV, indicating that FPV infected PBMCs and was not eliminated from PBMCs even in the presence of VN antibodies in the cats.     

Replication of canine herpesvirus: I. Synthesis of viral deoxyribonucleic Acid

This paper reports the results of two series of experiments. The first series indicated that deoxyribonucleic acid (DNA) extracted from partially purified canine herpesvirus virions is characterized by a high guanine plus cytosine molar base ratio (65 to 67 mole%), similar to the DNA of herpes simplex virus. In the second series of experiments it was estimated, on the basis of uptake of tritiated thymidine, that in dog kidney cells canine herpesvirus-DNA synthesis starts at 4 hr and continues until 16 hr after infection. Treatment of infected cells with puromycin during the first 4 hr of infection blocks the onset of viral DNA synthesis, whereas, after this time the uptake of thymidine is unaffected.     

Histopathology of feline panleukopenia in domestic cats.

Histopathological observations were carried out on 17 domestic cats naturally affected with feline panleukopenia. Principal lesions were found in the intestine, bone marrow, and lymphoid organs. Intestinal lesions were characterized by degenerative changes accompanied by the appearance of intranuclear inclusion bodies in the epithelial cells of the crypts. In contrast to the crypts, the villi were seldom involved. Hypoplasia, parenchymal degeneration, and activation of the reticuloendothelial system were observed in the bone marrow and lymphoid organs. Intranuclear inclusion bodies were found occasionally also in the reticular and parenchymal cells of the bone marrow, lymphoid organs, liver, adrenals, and pancreas. Most of the inclusion bodies were amphophilic when stained with hematoxylin and eosin and occupied the whole area of the nucleus without producing any zone of clear halo. While cells bearing inclusion bodies underwent degenerative changes constantly in the intestinal crypts, the formation of inclusion body was not accompanied by the degeneration of corresponding cells in any other organ. Pathological changes as mentioned above were considered to be closely related to the systemic infection of feline panleukopenia virus.     

Evaluation of tri-combinant vaccine for feline herpesvirus, calicivirus and panleukopenia virus infections in Japanese native cats

Tri-combinant vaccine consisting of attenuated feline herpesvirus (FHV) and feline calicivirus (FCV) and inactivated feline panleukopenia virus (FPLV), were evaluated for safety and efficacy, using Japanese native cats and the viral strains isolated in Japan. Thirty-eight 9- to 12-week-old kittens were inoculated intramuscularly and subcutaneously with the vaccine. Consequently, no adverse reaction was found, and protective efficacy was confirmed by challenge tests with the virulent strains of each virus. Serum-neutralizing antibodies against FCV and FPLV were maintained for at least one year after vaccination, whereas antibody against FHV disappeared in two cases at 24 weeks after vaccination. Application of this vaccine seemed effective for control of feline viral disease in cats for experimental use.     

Prevalence of feline immunodeficiency virus and feline leukemia virus infections in random-source cats.

Retroviral serologic profiles were generated for 506 random-source cats (Felis catus) that were received by our facility during a twenty-month period. Feline leukemia virus antigens were detected in plasma samples from 26 (5.1%) of the cats. Antibodies to feline immunodeficiency virus were present in 24 (4.7%) of the samples tested. A single cat (0.2%) was positive for both viruses. Neither gender nor vendor correlation with retroviral seropositivity could be demonstrated.     

Biosynthesis of glycoproteins E and I of feline herpesvirus: gE-gI interaction is required for intracellular transport.

The biosynthesis of glycoproteins E and I of feline herpesvirus was studied by using the vaccinia virus vTF7-3 expression system. gE and gI were synthesized as N-glycosylated, endoglycosidase H (EndoH)-sensitive precursors with Mrs of 83,000 and 67,000, respectively. When coexpressed, gE and gI formed sodium dodecyl sulfate-sensitive hetero-oligomeric complexes that were readily transported from the endoplasmic reticulum (ER). Concomitantly, the glycoproteins acquired extensive posttranslational modifications, including O glycosylation, leading to an increase in their apparent molecular weights to 95,000 and 80,000 to 100,000 for gE and gI, respectively. In the absence of gE, most gI remained EndoH sensitive. Only a minor population became EndoH resistant, but these molecules were processed aberrantly as indicated by their Mrs (100,000 to 120,000). By immunofluorescence microscopy, gI was detected primarily in the ER but also at the plasma membrane. gE, when expressed by itself, remained EndoH sensitive and was found only in the ER and the nuclear envelope. These results were corroborated by studying the biosynthesis of gE in feline herpesvirus (FHV)-infected cells. In cells infected with wild-type FHV, gE acquired the same co- and posttranslational modifications as during vTF7-3-driven expression. However, an FHV mutant lacking gI failed to produce mature gE. We conclude that gE is retained in the ER, presumably by associating with molecular chaperones, and becomes transport competent only when in a complex with gI.     

A review of allergic respiratory disease in laboratory animal workers.

There is increased recognition of hypersensitivity lung disease among workers with laboratory animals as an occupational disease. Symptoms of asthma in 44 of 78 workers with laboratory animal dander allergy reflected the serious consequences of this occupational ailment. Affected employee profiles induced family history of atopy; immediate (Type I) allergic reaction; symptoms of rhinitis, asthma, and cough; hypersensitivity to one or more species, most often rats, mice, and rabbits. Diagnosis depends on history and physical, radiologic, and laboratory examinations, including skin tests with relevant antigens. Control and treatment depend on environmental change (reemployment or reduction of antigen contact); mechanical devices (masks and filters); chemotherapy (bronchodilators, steroids), prophylaxis and immunotherapy (hyposensitization). Standardization of medico-legal criteria covering occupational asthma is needed.     

Studies of the effect of acemannan on retrovirus infections: clinical stabilization of feline leukemia virus-infected cats.

Feline leukemia is a disease induced by an oncornavirus infection that inevitably causes clinically affected cats to die. It has been estimated that 40% of cats are dead within 4 weeks and 70% within 8 weeks of the onset of clinical symptoms. Acemannan is a complex carbohydrate with both immunostimulatory and direct antiviral properties. Administration of acemannan for 6 weeks intraperitoneally to clinically symptomatic cats significantly improved both the quality of life and the survival rate. Twelve weeks after initiation of treatment, 71% of treated cats were alive and in good health.     

Plasma viral RNA load predicts disease progression in accelerated feline immunodeficiency virus infection.

Viral RNA load has been shown to indicate disease stage and predict the rapidity of disease progression in human immunodeficiency virus type 1 (HIV-1)-infected individuals. We had previously demonstrated that feline immunodeficiency virus (FIV) RNA levels in plasma correlate with disease stage in infected cats. Here we expand upon those observations by demonstrating that plasma virus load is 1 to 2 logs higher in cats with rapidly progressive FIV disease than in long-term survivors. Differences in plasma FIV RNA levels are evident by 1 to 2 weeks after infection and are consistent throughout infection. We also evaluated humoral immune responses in FIV-infected cats for correlation with survival times. Total anti-FIV antibody titers did not differ between cats with rapidly progressive FIV disease and long-term survivors. These findings indicate that virus replication plays an important role in FIV disease progression, as it does in HIV-1 disease progression. The parallels in virus loads and disease progressions between HIV-1 and FIV support the idea that the accelerated disease model is well suited for the study of therapeutic agents directed at reducing lentiviral replication.     

Substrate specificity of three viral thymidine kinases (TK): vaccinia virus TK, feline herpesvirus TK, and canine herpesvirus TK

In search of novel suicide gene candidates we have cloned and characterized thymidine kinases from three viruses; vaccinia virus TK (VVTK), feline herpesvirus TK (FHV-TK), and canine herpesvirus TK (CHV-TK). Our studies showed that VVTK primarily is a thymidine kinase, with a substrate specificity mainly restricted to dThd and only minor affinity for dCyd. VVTK also is related closely to mammalian thymidine kinase 1 (TK1), with 66% identity and 75% general homology. Although CHV-TK and FHV-TK are sequence related to herpes simplex virus types 1 thymidine kinase (HSV1-TK), with 31% and 35% identity and a general similarity of 54%, the substrate specificity of these enzymes was restricted to dThd and thymidine analogs.     

Association of plasma viral RNA load with prognosis in cats naturally infected with feline immunodeficiency virus

We measured the quantity of plasma feline immunodeficiency virus (FIV) RNA using a real-time sequence detecting system. Plasma viral RNA load was shown to correlate with the clinical stage, survival time, and disease progression in naturally FIV-infected cats. The present study indicates that the plasma viral RNA load can be used as a clinical marker representing the impairment of the immune system and predicting the clinical outcome in FIV-infected cats.