Evaluation of enzyme-linked immunosorbent assays based on monoclonal antibodies for the serology and antigen detection in canine parvovirus infections

Canine parvovirology - A brief updated review on structural biology, occurrence, pathogenesis, clinical diagnosis, treatment and prevention

Canine parvovirus (CPV) is a major cause of hemorrhagic diarrhea and mortality in puppies worldwide. There are 2 types of Parvovirus which affects canines: Canine parvovirus 2 (CPV-2) and Canine parvovirus 1 (CPV-1) or the Minute Virus of Canine (MVC). CPV-2 originated from Feline panleukopenia virus and has undergone genetic variation to give rise to its three variants (CPV-2a, CPV-2b and CPV-2c). Amino acid substitutions in VP2 capsid protein have led virus to adapt new host range. The original CPV-2 was known to be dominant in Japan, Belgium, Australia as well as USA and later circulated throughout the world. Clinically, CPV-2 infection is characterized by anorexia, lethargy, depression, vomiting, leukopenia and severe hemorrhagic diarrhea. Several diagnostic tests have been developed to detect parvoviral infections which are categorized into immunological tests (latex agglutination test, SIT-SAT and ELISA etc.) and molecular based tests (PCR, mPCR and RT-PCR etc.). To control and manage the disease several treatments like fluid therapies, antibiotics, and adjunctive treatments are available and some are in various stages of development. Apart from this, many vaccines are also commercially available and some are in developmental stages. The present review contains detailed information regarding structural biology, occurrence, pathogenesis, clinical diagnosis, treatments and prevention in order to understand the need and the growing importance of CPV-2.

[Diagnostic tools for canine parvovirus infection]

Canine parvovirus (CPV) infection is one of the most important and common infectious diseases in dogs, in particular affecting young puppies when maternal antibodies have waned and vaccine-induced antibodies have not yet developed. The mortality rate remains high. Therefore, a rapid and safe diagnostic tool is essential to diagnose the disease to 1) provide intensive care treatment and 2) to identify virus-shedding animals and thus prevent virus spread. Whilst the detection of antibodies against CPV is considered unsuitable to diagnose the disease, there are several different methods to directly detect complete virus, virus antigen or DNA. Additionally, to test in commercial laboratories, rapid in-house tests based on ELISA are available worldwide. The specificity of the ELISA rapid in-house tests is reported to be excellent. However, results on sensitivity vary and high numbers of false-negative results are commonly reported, which potentially leads to misdiagnosis. Polymerase chain reaction (PCR) is a very sensitive and specific diagnostic tool. It also provides the opportunity to differentiate vaccine strains from natural infection when sequencing is performed after PCR.

Development and evaluation of an immunochromatographic strip for rapid detection of porcine hemagglutinating encephalomyelitis virus

Background

The incidence of PHE among pigs in many countries is on the rise, and it has caused great economic losses to the pig industry. Therefore, the development of a sensitive, specific, and easily-performed assay is crucial for the rapid detection and surveillance of PHE-CoV infection and transmission.

Results

An immunochromatographic strip was developed for the detection of PHE-CoV. The colloidal gold-labeled MAb 4D4 was used as the detection reagent, and the MAb 1E2 and goat anti-mouse IgG coated the strip's test and control lines, respectively. The immunochromatographic strip was capable of specifically detecting PHE-CoV with a HA unit of 2 within 10 min. Storage of the strips at room temperature for 6 months or at 4°C for 12 months did not change their sensitivity or specificity. Using RT-PCR as a reference test, the relative specificity and sensitivity of the immunochromatographic strip were determined to be 100% and 97.78%, respectively. There was an excellent agreement between the results obtained by RT-PCR and the immunochromatographic strips (kappa = 0.976). Additionally, there was a strong agreement between the sandwich enzyme-linked immunosorbent assay (ELISA) and immunochromatographic strips (Kappa = 0.976). When the immunochromatographic strips were used for diagnosing PHE-CoV infection in the Jilin Province, the PHE-CoV-positive rate ranged from 61.54% in the Jilin district to 17.95% in the Songyuan district.

Conclusions

Based on its high specificity, sensitivity, and stability, the immunochromatographic strip would be suitable for on-site detection of PHE-CoV for surveillance and epidemiological purposes.

Inactivated recombinant plant virus protects dogs from a lethal challenge with canine parvovirus

A vaccine based upon a recombinant plant virus (CPMV-PARVO1), displaying a peptide derived from the VP2 capsid protein of canine parvovirus (CPV), has previously been described. To date, studies with the vaccine have utilized viable plant chimaeric particles (CVPs). In this study, CPMV-PARVO1 was inactivated by UV treatment to remove the possibility of replication of the recombinant plant virus in a plant host after manufacture of the vaccine. We show that the inactivated CVP is able to protect dogs from a lethal challenge with CPV following parenteral immunization with the vaccine. Dogs immunized with the inactivated CPMV-PARVO1 in adjuvant displayed no clinical signs of disease and shedding of CPV in faeces was limited following CPV challenge. All immunized dogs elicited high titres of peptide-specific antibody, which neutralized CPV in vitro. Levels of protection, virus shedding and VP2-specific antibody were comparable to those seen in dogs immunized with the same VP2- peptide coupled to keyhole limpet hemocyanin (KLH). Since plant virus-derived vaccines have the potential for cost-effective manufacture and are not known to replicate in mammalian cells, they represent a viable alternative to current replicating vaccine vectors for development of both human and veterinary vaccines.

A comparative study of a new rapid and one-step test for the detection of parvovirus in faeces from dogs, cats and mink

A one-step immunochromatographic test, based on the use of monoclonal antibodies, was developed for the detection of canine parvovirus (CPV) in dog faeces. In addition to canine parvovirus the test can also be used for the diagnosis of infections with viruses causing parvovirus enteritis in cats (feline panleukopenia virus) and mink (mink enteritis virus). Four hundred and forty-three faecal samples were evaluated by comparative testing between this one-step test and three different enzyme-linked immunosorbent assays (ELISA) in Sweden, Denmark and The Netherlands. The result of the evaluation showed an overall relative sensitivity and specificity of 95.8 and 99.7%, respectively. Furthermore, the comparative testing of 83 dog samples in Germany between the one-step test and an immune electron microscopy (IEM) agreed to 85.5%. The sensitivity and specificity were 83.9 and 88.9%, respectively. These results show that the one-step test is a rapid, simple, reproducible and sensitive diagnostic test for the detection of parvovirus in faecal samples of dogs, cats and mink.

Canine parvovirus infection, canine distemper and infectious canine hepatitis: inclination to vaccinate and antibody response in the Swedish dog population

The inclination of dog owners to vaccinate was investigated by sending a questionnaire to randomly selected Swedish dog-owning households. According to the owners (n = 538), 86.7% of the dogs had been vaccinated against CPV and 95.8% had been vaccinated against CD/ICH. The inclination to vaccinate mixed breeds was significantly lower than the inclination to vaccinate pure-bred dogs. In a second study titres of CPV, CD and CAV-1 virus antibodies were measured in 176 randomly selected dogs with known vaccination histories. CPV antibody titres > or = 1:80 were detected in 70.9% of the CPV vaccinated dogs. There was a significant difference in the fraction of dogs with CPV titre > or = 1:80 between the group last vaccinated with live attenuated vaccine and the group last vaccinated with inactivated vaccine. Titres of CD and CAV-1 virus antibodies > or = 1:16 were found in 86.1% and 91.6% of the vaccinated dogs respectively. The fraction of dogs with CAV-1 antibody titres > or = 1:16 was significantly greater in the group that received inactivated CAV-1 vaccine than in the group vaccinated with attenuated live CAV-2 vaccine. Approximately 50% of the dogs were booster vaccinated against all 3 diseases at one year of age.

Assessment of maternal antibody decay and response to canine parvovirus vaccination using a clinic-based enzyme-linked immunosorbent assay

Interference caused by maternal antibodies is considered a major cause of canine parvovirus (CPV) vaccination failure. In this study, an immunoblot clinic-based enzyme-linked immunosorbent assay (ELISA) method was used to detect CPV antibodies in sera of pregnant bitches and their offspring to study the response of pups to vaccination. With a easily accessible procedure for CPV antibody determination, the veterinarian should be able to gauge the response of pups after vaccination. The validity of the technique was tested in parallel against the standard hemagglutination inhibition (HI) test. Results of the ELISA were correlated with those of the standard HI method for quantification of CPV antibodies. With the ELISA, successfully immunized pups were identified, allowing for a more reliable and cost-effective program of vaccination. This simple clinic-based test could be used for the assessment of vaccination status of pups during the critical phase of 6 to about 16 weeks of age. This study is the first in which vaccination response to CPV in pups was followed, using a clinic-based ELISA for CPV antibody monitoring.

Effective induction of neutralizing antibodies with the amino terminus of VP2 of canine parvovirus as a synthetic peptide

Fourteen synthetic peptides corresponding to previously mapped antigenic sites in VP2 of canine parvovirus (CPV) were used for immunization of rabbits to identify antiviral properties favourable for inclusion into a vaccine. Most antipeptide antisera obtained were reactive with viral protein, and with one of them it was possible to locate the hypothetical amino terminus of VP3 within positions 15-31 of VP2. Virus-neutralizing antibodies were only obtained with two overlapping 15-mer peptides corresponding in sequence to the amino terminus of VP2 (MSDGAVQPDGGQPAVRNERAT). Antibodies in the neutralizing sera bound most strongly to amino acids of the sequence DGGQPAV within the N-terminus of VP2, indicating that efforts to develop a synthetic vaccine against CVP should be focused on this stretch of amino acids. The two peptides induced long-lasting immunity (at least 8 months) using either Freund's adjuvant or aluminium hydroxide plus Quil A. Thus, this approach delineated the exact peptide sequence useful for vaccines applied to the amino-terminal region of VP2. These findings in experimental animals form a solid basis for exploration of a synthetic peptide vaccine against parvovirus infection in dogs, minks or cats.

Evaluation of a novel diagnostic test for canine parvovirus

The CPV ELISA detection kit (CSL Ltd., Melbourne Australia) was developed as a rapid field test for the detection of canine parvovirus (CPV) antigen in canine faecal samples. The kit utilises a novel concept in enzyme immunoassay (ELISA) where the conjugate is lyophilised along with the solid-phase capture antibody in the test well. The CPV ELISA was compared to the haemagglutination assay (HA) test using electron microscopy (EM) and/or virus isolation (VI) to confirm infection. The CPV ELISA had a sensitivity of 87% and a specificity of 100% compared to 87% and 63% respectively for the HA. The poor specificity of the HA results in a low positive predictive value of 51% compared to 100% for the CPV ELISA. The CPV ELISA requires no specialised equipment, is simple to perform and provides a visible result in less than 15 minutes.

First peptide vaccine providing protection against viral infection in the target animal: studies of canine parvovirus in dogs

A synthetic peptide vaccine which protects dogs against challenge with virulent canine parvovirus is described. The amino acid sequence used was discovered in previous studies on the immunogenic properties of previously mapped antigenic sites and represents the amino-terminal region of viral protein VP2. As with marker vaccines, it is possible to discriminate between vaccinated dogs that have not been exposed to the virus and dogs that have been infected with the virus. The protective mechanism can be explained by a humoral response against the peptide aided by T-cell epitopes contained in the carrier protein used for peptide coupling. This is the first example of a synthetic peptide vaccine that induces protection in target animals.

The use of enzyme-linked immunosorbent assay systems for serology and antigen detection in parvovirus, coronavirus and rotavirus infections in dogs in The Netherlands

Complex trapping blocking (CTB) enzyme-linked immunosorbent assays (ELISAs) and indirect ELISAs for the detection of antibodies to canine parvovirus (CPV), canine coronavirus (CCV) and rotavirus in sera of dogs were established. Double antibody sandwich ELISAs for the detection of CPV-, CCV- and rotavirus antigens in fecal samples were also developed. Both the serological and antigen-detection ELISAs were used to screen samples from dogs in The Netherlands, with or without a history of acute diarrhea. It was shown that the results of the respective serological ELISAs correlated well and that CPV was the major cause of virus-induced acute diarrhea in dogs in The Netherlands.