Kinetics of Maternal Derived Antibody Status against Canine Distemper in Pups

Sixty-four sera samples were collected from 25- and 45-days old puppies [16 puppies each from vaccinated (Group I) and unvaccinated (Group II) dam] brought to Immunization Unit, Madras Veterinary College Teaching Hospital, Chennai. The samples were subjected to functional antibody assay (SNT) and commercially available Indirect ELISA to know the kinetics of maternal derived antibody (MDA) against canine distemper. The mean MDA titre in Group I puppies were found as 4.38 ± 1.41 and the ELISA titre were 30 - 60 and 10–30 AU on 25 and 45 days of age respectively whereas the Group II (MDA-UV) had titre value of0.33 ± 0.60 and 0 by SNT (SN50) and ≤ 10 and ≤ 3 AU by Indirect ELISA on 25 and 45 days of pups respectively. Though the statistical analysis (Mann-Whitney test) revealed a significant difference (P<0.01) between MDA of two groups with none of the group member had required protective titre, this study strongly suggests that the dogs aged more than 4 weeks needs to be immunized against CDV in endemic region in view of eliciting protective titre at earlier with a view of avoiding window period of susceptibility between 25 and 45 days of age.

Production of equine sera as a potential immunotherapy against COVID-19

Emerging viruses such as the COVID-19-inducing virus, SARSCoV- 2, represent a threat to human health, unless effective vaccines, drugs or alternative treatments, such as passive immunization, become accessible. Animal-derived immunoglobulins, such as equine immunoglobulins might be useful as immunoprophylaxis or immunotherapy against this viral disease. Therapeutic antibodies (Abs) for SARS-CoV-2 were obtained from hyperimmune equine plasma using the Spike protein receptor binding domain (RBD) as an immunogen. The presence of anti-RBD antibodies was evaluated by ELISA and the titres of neutralizing antibodies were determined in viral cell culture. Immunized horses generated high-titre of anti-RBD antibodies with antiviral neutralizing activity on Vero-E6 cells of 1/1,000. To minimize potential adverse effects, the immunoglobulins were digested with pepsin, and purified to obtain the F(ab’)2 fragments with the protocol standardized by Biotecfar C.A for the production of snake antivenom. Pre-immune serum displayed an unexpected anti-RBD reactivity by ELISA (titre up to 1/900) and Western Blot, but no angioneutralizing activity. Modelling of the RBD of equine coronavirus showed that some of the known epitopes of SARS-CoV-2 RBD were structurally conserved in the equine coronavirus protein. This might suggest that some of the reactivity observed in the pre-immune serum to the SARS-CoV-2 RBD might be due to a previous exposure to equine coronavirus.

Decay pattern of maternally derived antibodies and antibody response of infectious bursal diseases live vaccine

Introduction: Repeated outbreaks of infectious bursal disease (IBD) despite vaccination necessitated this study. Methods: The right age of IBD vaccination, the immunogenicity and the strain of the vaccine were established. Boven gold pullets (n = 150) were used. They were grouped into 6 groups; unvaccinated and vaccinated chicks according to weeks of blood sampling. Both antibodies titres (unvaccinated and vaccinated) were determined by enzyme- linked immune sorbent assay (ELISA). Results: In broiler chicks, the maternally-derived antibodies (MDA) titre decayed from 1,500 ELISA titre at day old to zero at 35 days , while the antibody rose from a titre of 500 at day old to titre of 2000 at 40 days following vaccination and intercepted at a titre of 700 at 21 days. In pullet chicks, the MDA started with an ELISA titre of 1,500 at day old to zero at 38 days of age, while antibodies rose from a titre of 1,100 at day old to 2,000 at 35 days, and then intercepted at a titre of 800 at 22 days of age, hence the breakthrough titre of the live vaccine for pullet chicks. Significance: MDA for broiler and pullet chicks for the chicks from this hatchery completely decayed at 35 and 38 days, respectively and intercepted at a titre of 700. Thus, the chicks should be vaccinated at 21 and 22 days, respectively. Also, poultry farmer should not use the same vaccination days for chicks of different hatchery. The breakthrough titre of the vaccine was 700. Therefore, it is an intermediate plus. The decay was faster in broilers than pullets, hence vaccination days should be early in broilers than pullets.

Standardization and application of rapid tests viz dot ELISA and vertical flow through tests for serodiagnosis of classical swine fever

The present study was carried out to develop rapid field-based immunoassays for onsite detection of Classical swine fever virus (CSFV) antibody in clinical serum sample. Purified CSFV antigen was coated onto nitrocellulose membranes housed in a plastic module with layers of absorbent filter pads underneath. Following addition of serum to be tested appearance of a red dot indicated the presence of antibodies to CSF virus in the sample tested. A total of 240 serum samples collected from different areas of North Eastern States of India were tested for the presence of CSFV antibody by Indirect ELISA, Dot ELISA and Vertical flow through test. The result of the Indirect ELISA could be obtained within 2.5 hours whereas the result in case of Dot ELISA and Vertical Flow through test was obtained within 1 hour and 15 minutes respectively. Dot-ELISA and Vertical flow through test could equally detect the CSFV antibody in samples possessing 1:4 and above ELISA titre. The specificity and sensitivity of Dot-ELISA and vertical flow through test after comparison with Indirect ELISA indicated 100% specific and 84.28% sensitive. These tests have the potential to be used as a field-based kit to assess the serodiagnosis of CSFV.

Specificity of accumulation and transmission of tomato spotted wilt virus (TSWV) in two genera, Frankliniella and Thrips (Thysanoptera: Thripidae)

The accumulation and transmission of tomato spotted wilt virus (TSWV) was examined in second instar larvae and adults of two thrips genera, Frankliniella and Thrips. The species tested were F. occidentalis (Pergande), F. intonsa (Trybom), T. tabaciLindeman, T. setosus Moulton, T. palmi Karny and T. hawaiiensis (Morgan). In a standard petunia leaf disc assay, the efficiencies of TSWV transmission by two species of Frankliniella were higher than those of any Thrips species in the adult stage. A triple antibody sandwich enzyme-linked immunosorbent assay (TAS-ELISA) showed that large amounts of the TSWV-nucleocapsid (N) protein were present in the ELISA-positive larvae of each species, with the exception of T. palmi. The ELISA titre of and the proportion of virus-infected individuals of the two Frankliniella species increased or did not significantly change from the larval to the adult stages, whereas those of the four Thrips species decreased significantly. These results show that the specificity of virus transmission by adult thrips is probably affected by the amount of viral N protein accumulation in the adults and that the accumulation pattern from the larval to the adult stages is in between the two genera tested in the present study.

Responses to housing conditions and immunological state in sows

If a housing condition results in impaired immune system function then vulnerability to disease is greater in that condition. Measures of immune system function can therefore be important indicators of welfare. Another indicator of welfare is the maximal adrenal cortex response to ACTH challenge. Ten third parturition sows kept in stalls, and 27 first parturition sows kept in an electronic sow feeder system have been studied. A direct measure of immune system function is to assess B-cell responses by measuring antibody production following antigen challenge. Sows in stalls were injected with tetanus toxoid, as commonly practised for protection against tetanus. The amount of antibody produced was negatively correlated with adrenal weight. The colostral antibody ELISA titre was 1/125,000 when the response to ACTH challenge was zero but was almost zero in animals which showed an increase in salivary Cortisol of 25 nmol l-1 after ACTH challenge i.e. antibody production was negatively correlated with adrenal response (r = -0.634, p = 0.028 (Fig. 1)).

A competitive ELISA for the detection of group-specific antibodies to African horse sickness virus

SUMMARYA competition enzyme-linked immunosorbent assay (ELISA) has been developed for the rapid identification and quantification of antibodies against African horse sickness (AHS) in sera from solipeds. The data showed the ELISA to be sensitive, specific and reliable.More than 1600 sera from 37 different countries were examined and results compared with those obtained by agar gel immuno-diffusion (AGID) tests. In no case did any of 775 sera from countries where AHS has never been reported and where AHS vaccines are not used, record an ELISA titre greater than 4. A titre equal to or greater than 8 was considered positive. Using this criterion, 96·3% of sera tested in both assays were in agreement. Doubtful results by AGID (1·7%) were clearly defined in terms of positivity and negativity by ELISA.This ELISA is suited for the rapid laboratory confirmation of AHS and should be considered as a replacement for the traditional AGID test.