Orf virus, derived from contagious pustular dermatitis (scabby mouth) lesions in sheep, was adapted to cell culture and subsequently evaluated as a potential vaccine for sheep. The traditional vaccine virus, prepared from the infected scabs of orf virus lesions in sheep, was used to vaccinate sheep by scratching with an applicator (mounted pins) dipped in virus. Less than 10 TCID50 (50% tissue culture infectious doses) of virus was required to produce large lesions (greater than 5 mm diameter) which developed during a period of 10 to 14 d prior to onset of healing which was complete by 28 to 30 d. A serum neutralising antibody response was also detected and protection against challenge by application of virulent virus to abraded skin was demonstrated in that challenge lesions developed and healed more quickly (14 d against 30 d). However, cell culture-adapted virus required more than 10(5) TCID50 to induce even small lesions (less than 2 mm diameter). An antibody response could not be detected and no evidence of protection against challenge with virulent virus was demonstrated. In contrast, a recent field isolate has yielded a cell culture-adapted virus preparation that readily infects sheep, produces large lesions, detectable antibody and protects against challenge. This isolate is distinct from the traditional vaccine strain on the basis of restriction enzyme analysis but provides cross-protection in sheep inmmunisation and challenge studies. These results demonstrate that a cell culture produced scabby mouth vaccine is feasible.

SUMMARYThis simple procedure for the detection of serum antibodies to Nosema cuniculi in rabbits and other host species incorporates indirect immunofluorescence and uses as antigen N. cuniculi isolated from urine and cultured in a human fibroblast-like cell line derived from foetal tongue. Examination of rabbit sera from 8 institutions indicated that no institution was free from Nosema infection. The prevalence of infection in 4 separate Australian rabbit colonies varied from 25 to 75 %.

Saimiri sciurus monkeys were immunized at multiple sites with recombinant vaccinia viruses expressing Plasmodium falciparum antigen genes and boosted 4 weeks later. Control monkeys were immunized with a thymidine kinase-negative vaccinia virus mutant. Two weeks later, all of the monkeys were challenged by intravenous inoculation of P. falciparum (Indochina strain) parasites. A group of unimmunized monkeys was challenged in parallel. All of the monkeys that received vaccinia virus recombinants or the control virus produced good anti-vaccinia virus antibody responses. However, those that received a single construct containing ring-infected erythrocyte surface antigen (RESA) given at eight sites did not produce significant antibody to any of the three major RESA repeat epitopes after immunization but were primed for an enhanced antibody response after challenge infection with P. falciparum. Most of the monkeys produced detectable antibodies to the RESA epitopes after challenge infection. One group of monkeys was immunized with four constructs (expressing RESA, two merozoite surface antigens [MSA-1 and MSA-2], and a rhoptry protein [AMA-1]), each given at two sites. While these monkeys failed to produce significant antibody against MSA-2 or AMA-1 after immunization, they produced enhanced responses against these antigens after challenge infection. Immunization involved an allelic form of MSA-2 different from that present in the parasite challenge strain, so that the enhanced responses seen after challenge infection indicated the presence of T-cell epitopes common to both allelic forms. No groups of monkeys showed any evidence of protection against challenge, as determined by examination of the resulting parasitemias.

SUMMARYSera from 823 wild rabbits (Oryctolagus cuniculus) collected from a number of geographic regions of Victoria, Australia over the past eight years were examined for antibodies to Encephalitozoon cuniculi, along with sera from 46 hares (Lepus europaeus) (Pallas) and 57 New Zealand wild rabbits. No sera were positive, implying that this common laboratory rabbit parasite is absent from wild rabbits in these areas. However, wild rabbits were found to be readily infected by the oral route with small numbers of tissue-culture-grown spores of E. cuniculi. A possible explanation for the absence of encephalitozoonosis in wild rabbits is that E. cuniculi infection places them at a biological disadvantage for survival. The natural hygiene habit of wild rabbits may also significantly decrease post-natal infection.

Encephalitozoon cuniculi was isolated from the urine of infected rabbits using human and canine tissue cultures. The organism was isolated from 7 of 11 contaminated urines from seropositive animals. The advantages of urine over tissue as a source of E. cuniculi are that it is obtainable from living animals, can be examined for the presence of organisms, and is essentially free of cells likely to overgrow the tissue cultures used for isolation.