Antigenic characterization of the inclusion body hepatitis virus

Proof that inclusion body hepatitis of chickens (IBHC) is caused by a virus (IBHV) was established in 1973. Characterization of IBHV has been conducted by employing the standard criteria for virus classification. The results have indicated that IBHV is a member of the avian adenovirus group. However, no antigenic relationship was found between IBHV and two other avian adenovirus isolates (CELO and Indiana C) as observed by hemagglutination (HA) and virus-serum neutralization tests. Another adenovirus isolate was found to be serologically different from IBHV (Tipton strain) but it incited typical IBHC in susceptible chicks. A novel antigen, detectable by the agar gel immunodiffusion test, was demonstrated in livers from chicks infected experimentally with IBHV. This antigen was able to give a specific precipitin reaction with serums from chickens previously exposed to IBHV. Repeated embryo passage of IBHV lowered its pathogenicity for susceptible chickens. Protection of chickens against IBHV challenge was obtained by vaccination with high embryo passage IBHV (Tipton strain). It was also found that subcutaneous administration of the vaccine virus induced a better immune response than the eye-drop route as observed by the virus-serum neutralization index obtained.

Antibody responses to neonatal immunisation in calves

Antibody responses were measured in colostrum-fed (CF) and colostrum-deprived (CD) calves immunised at ages varying from birth to four months using a variety of antigens with and without adjuvant. In addition immunoglobulin production in CD calves over the same period was compared with that of CF calves. A marked unresponsiveness to antigens injected at birth was observed if maternal antibody specific for the antigen used was present in the circulation. However, significant responses to all antigens tested occurred in CD calves and also in CF calves immunised with an antigen (egg albumin) to which there was no maternal antibody. Since these responses were not as great as those in older calves immunised similarly it is clear that age was influencing the response. It was also found that subsequent responsiveness was not significantly enhanced or impaired by neonatal exposure to antigen. With respect to immunoglobulin production the results conclusively demonstrated that endogenous production occurred much earlier in CD calves than CF calves and even after 128 days the serum concentrations of IgG1 and IgA in CD calves exceeded those for CF calves. Thus it appears that the most important consideration in immunological responsiveness of neonates is not so much immaturity of the lymphoid system as the effects of maternal antibody on the cells in that system.

Human leptospirosis

Human leptospirosis is a subject of increasing interest. Although this disease was frequently associated with individuals whose occupation or geographic location placed them in close proximity to wild animals or farm animals, recent cases have been particularly prevalent in young children and adolescents in urban and suburban America. Many of the recent cases have been acquired from household pets, particularly from dogs or hamsters. In particular, healthy dogs who have been immunized with leptospiral organisms, thereby creating a significant risk for their owners. This article will review the pathophysiology, clincal manifestations, laboratory diagnosis, treatment, and prevention of leptospirosis in the modern era, with particular emphasis on a more complete understanding of the epidemiology of this disorder.

The specific immunoglobulin response in cattle immunized with isolated Theileria parva antigens

Cattle were inoculated with purified Theileria parva piroplasm and/or schizont antigen. Two similar inoculations were given 10 days apart. Serum samples were regularly collected and the indirect haemagglutination (IHA), indirect immunofluorescence (IFA), complement-fixation (CF) and immunodiffusion (ID) tests were used to detect T. parva antibodies. Selected sera were separated by Sephadex G 200 and fractions examined for specific immunoglobulin activity.

With the IHA test specific antibody first appeared 4 days post inoculation (dpi) and reached high titres by 8 dpi. With the IFA and CF tests specific antibody also appeared 4 dpi and reached high titres by 8–14 and 10–14 dpi respectively. Specific ID activity was detected as early as 6 dpi and persisted for the length of the experiment.

On fractionation of the sera both the IHA and CF tests indicated a sequential production of T. parva IgM and 7S Ig. However, in cattle inoculated with schizont antigen only, a significant 7S Ig component was not detected by the IHA test until 16 dpi, but was demonstrated by the CF test 7 dpi. The IFA test, however, detected anti T. parva activity almost exclusively in the 7S Ig fractions. All cattle were challenged 35–42 dpi with infective T. parva stabilate and all cattle proved fully susceptible. The lack of protection by high titres of specific T. parva immunoglobulin is discussed, together with the data on the differential immunoglobulin response, in relation to previous results.

The specific immunoglobulin response in cattle immunized with Theileria parva (Muguga) stabilate

Immunoglobulin synthesis in response to experimental infection of cattle withTheileria parva(Muguga) was studied by Sephadex G 200 chromatography. Serum samples were collected for 88 days following inoculation. Indirect fluorescent antibody (IFA), complement fixation (CF), indirect haemagglutination (IHA) and immunodiffusion (ID) tests were used to detect activity againstT. parvapiroplasm antigen. There was a small and transient IgM response in the IFA test, thereafter all IFA activity was 7S Ig. A sequential production of IgM and 7S Ig CF antibodies was demonstrated. In all sera tested only IgM activity was demonstrated by the IHA test. These results are compared with those from similar studies withT. parvaand other protozoan diseases, especially in the differential immunoglobulin response shown by the contrasting results from the three serological tests.

The effect of edema, hydrocortisone acetate, concurrent viral infection and immunization on the clearance of Pasteurella hemolytica from the bovine lung

The influence of pulmonary edema, hydrocortisone, immunization against Pasteurella hemolytica and concurrent infection with parainfluenza-3 virus upon pulmonary clearance of aerosolized P. hemolytica was studied in 31 calves. Following the various treatments calves were challenged with an aerosol of P. hemolytica. One control calf was killed immediately after the aerosol and the numbers of bacteria in the lung taken as 100%. Two calves were killed four hours after challenge and the numbers of bacteria in the lungs were compared to the 100% of the control calf. The result was the percentage clearance of bacteria at four hours. PULMONARY EDEMA WAS INDUCED BY THREE DIFFERENT METHODS: by an aerosol of histamine, by intravenous injection of endotoxin and by intravenous injection of croton oil emulsion. The edema impaired the clearance of P. hemolytica, which was reflected in high numbers of P. hemolytica present in the lungs at four hours after challenge: 260% after histamine, 300% and 400% after endotoxin and 92% after croton oil. SIX DAYS OF TREATMENT OF FOUR CALVES WITH HIGH DOSES OF HYDROCORTISONE ACETATE PRODUCED INCONSISTENT RESULTS: two calves treated with a higher daily dose (36 mg/kg) had normal clearance whereas two calves treated with a lower dose had pulmonary edema and displayed lowered clearance with 111% and 31% respectively of P. hemolytica retained in the lungs four hours after challenge. Immunization of calves by three different methods, a subcutaneously injected bacterin of P. hemolytica (2 calves), single aerosol (2 calves) and four aerosols (4 calves) of live P. hemolytica was reflected in an accelerated pulmonary clearance of P. hemolytica (with a mean of 1.55% of bacteria retained at four hours). Concurrent infection with parainfluenza-3 virus did not lower the clearance of P. hemolytica in the lungs of 12 calves over 15 days except on the first day following the exposure to parainfluenza-3 virus. These calves had hemagglutinating antibodies against P. hemolytica before exposure.