Cross-immunity Studies Research Articles

Infectivity and cross-immunity studies of Theileria lestoquardi and Theileria annulata in sheep and cattle: I. In vivo responses

In a series of experiments, sporozoite stabilates of a Theileria lestoquardi (Lahr) and a T. annulata (Ankara) stock prepared from Hyalomma anatolicum anatolicum ticks, were used to examine the infectivity of both parasite species for sheep and cattle and to study the development of cross-immunity between these parasite species. In the first experiment sheep and cattle were inoculated with T. lestoquardi sporozoites. Surviving animals and naive sheep and cattle were, in the second experiment, inoculated with T. annulata. In the third experiment, naive sheep and sheep previously infected with T. annulata, were inoculated with T. lestoquardi. The following responses to inoculations were monitored: clinical and haematological signs of infection, appearance of parasitic stages of the parasites in lymph node biopsies and in peripheral blood and serological response to T. lestoquardi and T. annulata schizont antigens. While T. lestoquardi readily infected sheep and caused severe disease, it did not infect cattle. On the other hand, T. annulata infected both cattle and sheep. However, whereas cattle became severely affected, infected sheep showed mild clinical symptoms only and piroplasms did not develop. Despite their different behaviour in the host species examined, cross-immunity studies suggested that the parasite species are very closely related. Experiments in sheep indicated that T. lestoquardi infection protected against subsequent T. annulata infection. On the other hand, recovery from T. annulata infection did not prevent infection by sporozoites of T. lestoquardi, resulting in the establishment of schizonts and their subsequent development into piroplasms, although it protected against the major clinical effects of T. lestoquardi infection.

Infectivity and cross-immunity studies of Theileria lestoquardi and Theileria annulata in sheep and cattle : II. In vitro studies

In the studies previously reported, the tick-borne protozoan parasites Theileria lestoquardi and Theileria annulata were shown to differ in their capacity to infect sheep and cattle. In the studies presented here, these findings were further supported. In vitro infectivity of T. lestoquardi and T. annulata sporozoites for peripheral blood mononuclear cells of sheep and cattle were determined by analysis of cell cultures for cell proliferation, the detection of parasites in Giemsa-stained cytospin smears and the establishment of continuously growing schizont-infected cell lines. In the same way, the development of schizont-infected cells into continuously growing cell lines was studied with material isolated ex vivo from the sheep and cattle undergoing primary infections described elsewhere. Comparisons were also made between development of ex vivo cell lines from animals undergoing primary infections with those of the animals undergoing challenge infection with the other parasite species. Theileria species specific primers were used in a PCR to determine the identity of the parasites in the cell lines. These in vitro studies confirmed earlier observations that T. lestoquardi was unable to infect cattle, whereas infection of all sheep with T. annulata was proven. Moreover, earlier indications of the development of partial cross-immunity in sheep of T. annulata to T. lestoquardi and vice versa were strengthened. These findings may thus have consequences for the understanding of the epidemiology of T. lestoquardi infections of sheep. On the other hand, since piroplasms were not demonstrated in sheep infected with T. annulata, such sheep will not be infective to ticks and will consequently be unlikely to play a role in the maintenance and transmission of T. annulata to cattle.

The Early History of Infectious Bronchitis

Two years later, Bushnell and Brandly (3) reported on an essentially identical disease. They established that the causative agent was a filterable virus because the disease could be transmitted by Berkefeld-filtered material. Because the symptoms of respiratory distress were caused by a filterable virus, Bushnell and Brandly regarded the disease as a form of infectious laryngotracheitis (LT). Further critical tests were not made to confirm this identity. Bushnell and Brandly's report (3) was considered by most later research workers in avian respiratory diseases to actually describe further outbreaks of infectious bronchitis (IB). It was not until much later that the possibility could be considered that some or all of their cases could really have been cases of the mild or lowvirulence type of LT described by Cover and Benton (4). A further source of confusion was that, in the 1930s, the name infectious bronchitis was used in some papers actually describing LT. This confusion was cleared up a few years later by Beach and Schalm (1), who proved by cross-immunity studies in chickens that IB virus was distinct from infectious LT virus and

Evaluation of a Commercial Quail Pox Vaccine (Bio-Pox Q [Trademark]) for the Control of "Variant" Fowl Poxvirus Infections

Groups of 3-week-old specific pathogen-free chickens immunized with a commercial live-virus quail pox vaccine (Bio-Pox Q) were not protected against challenge with "variant" poxviruses isolated from chickens that were previously vaccinated with commercial fowl pox vaccine. The percentages of vaccinated chickens resistant to challenge with each of the five variant field isolates were 0%, 20%, 0%, 20%, and 10%, respectively. However, when immunity engendered by the variant field isolates was challenged with the commercial quail pox vaccine virus, 80%, 70%, 80%, 50%, and 60% of the vaccinates, respectively, were protected. Results from cross-immunity studies indicate that the commercial quail pox vaccine does share some immunologic relationship with these variant poxvirus field isolates, but not enough to be used in the control of some outbreaks of pox caused by variant poxviruses.

Generation and characterization of cloned Theileria parva parasites.

A 3-step procedure for cloning Theileria parva parasites was developed. The first step involved the in vitro infection of a fixed number of bovine lymphocytes with titrated sporozoites. The cell lines obtained from infections initiated using sporozoite/lymphocyte ratios below 1:100 were then selected for cloning as these contained schizont-infected cells, each of which was derived from infection with a single sporozoite. In the second step, these cell lines were cloned by limiting dilution. As sporozoites infect lymphocytes and transform to induce clonal multiplication, this step produced infected cell lines containing both cloned parasites and cloned lymphocytes. In the third step, the cloned cell lines were used to infect cattle and isolation of the parasite in ticks was made during piroplasm parasitaemia. Finally, sporozoites were harvested from infected ticks and used for further characterization. Sporozoites derived from cloned cell lines of T. parva Muguga, Marikebuni, Boleni, Uganda and buffalo-derived 7014 were characterized using monoclonal antibody profiles, DNA restriction fragment length polymorphism detected using repetitive and telomeric probes, in vivo infectivity and, in one case, cross-immunity studies. Additionally, several distinct schizont-infected lymphocyte clones were isolated from the Muguga, Mariakani and buffalo-derived 7014 stocks. The combined results of the characterization revealed that the cloning procedure selected clones of T. parva from the parental stocks which were known to contain a mixture of genetically different parasite populations. The cloning method and the clones generated will be of value in studies of the biology of the parasite and in elucidating the strain specificity of immune responses in cattle.

Experimental american leishmaniasis and chagas' disease in the brazilian squirrel monkey: Cross immunity and electrocardiographic studies of monkeys infected with Leishmania braziliensis and Trypanosoma cruzi

Pung O. J., Hulsebos L. H. and Kuhn R. E. 1988. Experimental American leishmaniasis and Chagas' disease in the Brazilian squirrel monkey: cross immunity and electrocardiographic studies of monkeys infected with Leishmania braziliensis and Trypanosoma cruzi. International Journal for Parasitology 18: 1053–1059. Adult, laboratory-bred squirrel monkeys ( Saimiri sciureus) previously infected with either Leishmania braziliensis braziliensis or L. b. panamensis were challenge infected with blood-form trypomastigotes of Trypanosoma cruzi (Brazil strain). Monkeys previously infected with T. cruzi were challenged with stationary phase promastigote forms of L. b. braziliensis. Monkeys were examined during the course of challenge for evidence of infection, electrocardiographic alterations and parasite-specific antibody responses. T. cruzi epimastigotes were cultured from the blood of monkeys up to 3 months after challenge with this parasite. Unulcerated cutaneous lesions appeared and persisted in monkeys challenged with L. b. braziliensis. The formation of satellite lesions was observed in one monkey. Increased QRS intervals were not observed in T. cruzi challenged monkeys without prior cardiac irregularities and QRS left axis shifts were observed in only two of these monkeys. Elevated titers of parasite binding IgM and IgG specific for both T. cruzi and L. braziliensis were observed in all monkeys following challenge. These results indicate that prior infection with T. cruzi or L. braziliensis does not protect against heterologous challenge infection with these organisms. However, prior infection with Leishmania parasites may provide some protection against chagasic cardiopathies.

Assessment of cross‐immunity dm chickens to strains of avian infectious bronchitis virus using tracheal organ cultures

A method is described of assessing cross-immunity in chickens afforded by strains of avian infectious bronchitis virus (IBV), by observing the presence or absence of ciliary activity in tracheal explants prepared from chickens following challenge. Chickens inoculated with the H120 vaccine strain were challenged intra-tracheally 3 weeks later with the homologous strain or one of seven heterologous strains of IBV. Vaccinated chickens were protected against challenge by the homologous strain (H120) and four other strains (Massachusetts M-41, Connecticut 46, Holte, Iowa 609), but not by one strain (T). The vaccine strain afforded incomplete protection against one further strain (Iowa 97) and less still against another (Gray). All unvaccinated birds were susceptible to challenge by all strains. The method is recommended for use in cross-immunity studies and for assessing strains for use in IBV vaccines.

Strain variation within Eimeria meleagrimitis from the turkey

During the course of a field study of coccidiosis in turkeys, Eimeria oocysts were found which had much smaller dimensions that any previously recorded isolate from the turkey. These oocysts were purified by single oocyst infection of a turkey. The first oocysts (mean dimensions 16-15 X 14-75 micrometer) were recovered 103 h later. Inoculation of between 0-5 and 2-5 X 10(5) oocysts of this isolate caused severe effects on body weight gain. Cross-immunity studies showed the parasite to be a strain of E. meleagrimitis. Electrophoretic analyses of two enzymes showed that the strain could be differentiated from another strain of E. meleagrimitis (Weybridge strain B). The results show that strain variation occurs within the species E. meleagrimitis and extreme caution should be used in identifying species of Eimeria from the turkey by the oocyst characters.

Cross Immunity Between Plasmodium relictum and Plasmodium lophurae in Chickens

DATA from several experiments have suggested that host defenses, responding to the presence of parasites, may be implicated in host-specificity of avian malaria. Such defenses include the spleen which has been designated as the organ of importance in this protection (Taliaferro and Taliaferro, 1955; Moulder and Taliaferro, 1955; Taliaferro, 1956; and Longenecker et al., 1966). That antibodies are produced in response to malarial infections is well documented (Manwell and Goldstein, 1940; Taliaferro, 1940; Coggeshall and Kumm, 1938; Zuckerman, 1945; Ingram et al., 1961).Yet while there is much evidence for host specificity there is also evidence for cross immunity. Examination of the Plasmodium literature indicates that results of previous cross immunity studies have been variable. The complete lack of heterologous cross immunity has been frequently reported. Hartman (1927), used P. praecox (now P. elongatum) and the H strain of P. cathemerium and Manwell (1929), used the same parasites. Kikuth (1931),…

Immunity Following Aerosol Exposure to High-Embryo-Passage Avian Infectious Bronchitis Virus

Live virus vaccines are used extensively in the control of avian infectious bronchitis. The virus used in today's vaccines is an embryo-propagated strain that has been passaged serially at least 25-30 times in embryonating chicken eggs. At this passage level the virus retains its immunogenicity while its pathogenicity for chickens is somewhat reduced. Correctly applied, these vaccines induce a good immunity. However, have been reported following bronchitis immunization (7). Since there are several serological types of infectious bronchitis virus (IBV), it is surprising that more breaks do not occur following vaccination. It was observed in cross-immunity studies (5) that some degree of immunity to challenge could be demonstrated between serological types of IBV even though the serum antibody level was low or negligible. The experiments reported here were made to study the response of the tracheal mucosa to virus challenge over 6-8 months following initial aerosol exposure of chicks to a high-embryo-passage bronchitis virus.

Antigenic and Immunological Studies on Several Isolates of Avian Infectious Bronchitis Virus

APREVIOUS communication2 reported studies on 14 isolates of infectious bronchitis virus (IBV) by reciprocal serum neutralization (SN) tests. Three isolates were found antigenically different from the usual pathogenic strains of IBV and different from each other as determined by SN tests. The present study deals with an additional 5 isolates of IBV, including two commercial vaccine strains. The serological relationship of these isolates and the three antigenically different isolates mentioned above were studied by SN tests. Cross-immunity studies were also done to correlate SN with cross-challenge results.

Cross Immunity Studies between Virus Strains in the Psittacosis-Lymphogranuloma Venereum Group

Morphologically similar strains in the psittacosis-lymphogranuloma venereum group of viruses, producing minute, intra-cytoplasmic, coccoid elementary bodies, have been isolated from man,1 ferrets,2 hamsters,8 mice,4 parakeets,6 and many other avian species.6 The close antigenic relationship between these virus strains that has been shown to exist by the complement-fixation test7'8,913 has not been borne out in the