Duration of immunity after rabies vaccination in dogs: The Rabies Challenge Fund research study.

A prospective study of 65 research beagles kept in a rabies-free environment was undertaken to determine the duration of immunity after they received licensed rabies vaccines. The eventual goal was to extend mandated rabies booster intervals to 5 or 7 years and help reduce the risk of vaccine-associated adverse events. Three groups of dogs were vaccinated with 1 of 2 commercial rabies vaccines or saline at 12 and 15 weeks of age. Beginning 5 years 5 months later, vaccinated and unvaccinated dogs were challenged with virulent rabies virus and observed for 90 days over a series of 3 trials. Humoral and cellular immune responses were examined by serology and flow cytometry. Brain tissue from all challenged dogs was tested for rabies virus. Challenge trial 1 was confounded due to insufficiently virulent virus. In trials 2 and 3 virulent challenge provided 100% mortality in controls. Vaccinate survival was 80% (4/5) after 6 years 7 months, 50% (6/12) after 7 years 1 month, and 20% (1/5) after 8years 0 months. Antibody responses 12 days post-challenge correlated strongly with survival. In a separate non-challenge trial, administration of either a recombinant or a killed rabies vaccine demonstrated memory antibody responses 6 years 1 month after initial vaccination compared with unvaccinated controls. Our data demonstrated that i) duration of immunity to rabies in vaccinated dogs extends beyond 3 years; ii) immunologic memory exists even in vaccinated dogs with serum antibody titer < 0.1 IU/mL; and iii) non-adjuvanted recombinant rabies vaccine induces excellent antibody responses in previously vaccinated dogs 14 days after administration.

Une étude prospective sur 65 chiens beagle de recherche gardés dans un environnement exempt de rage fut entreprise afin de déterminer la durée de l'immunité après qu'ils reçurent un vaccin homologué contre la rage. Le but éventuel était d'allonger l'intervalle requis du rappel du vaccin contre la rage à 5 ou 7 ans et aider à réduire le risque associé aux réactions adverses au vaccin. Trois groupes de chiens furent vaccinés avec un des deux vaccins commerciaux contre la rage ou de la saline à 12 et 15 semaines d'âge. Débutant 5 ans et 5 mois plus tard, les chiens vaccinés et non-vaccinés furent soumis à une infection défi avec un virus de la rage virulent et observés pendant 90 jours lors d'une série de trois essais. Les réponses immunitaires humorale et cellulaire furent examinées par sérologie et cytométrie de flux. Du tissu cérébral de tous les chiens infectés fut testé pour la présence du virus rabique. L'essai 1 était décevant étant donné la quantité insuffisante de virus virulent. Lors des essais 2 et 3, l'infection défi a entrainé 100 % de mortalité chez les témoins. Le taux de survie des animaux vaccinés était de 80 % (4/5) après 6 ans et 7 mois, 50 % (6/12) après 7 ans et 1 mois et 20 % (1/5) après 8 ans 0 mois. La réponse en anticorps 12 jours post-infection corrélait fortement avec la survie. Dans un essai séparé sans infection défi, l'administration de soit un vaccin recombinant ou un vaccin tué a mis en évidence une réponse anamnestique en anticorps 6 ans et 1 mois après la vaccination initiale comparativement aux témoins non-vaccinés. Nos résultats démontrent que (1) la durée de l'immunité contre la rage chez les chiens vaccinés va au-delà de 3 ans, (2) une mémoire immunologique existe même chez les chiens vaccinés avec des titres d'anticorps sériques < 0,1 IU/mL, et (3) un vaccin antirabique recombinant sans adjuvant induit d'excellentes réponses en anticorps chez des chiens préalablement vaccinés 14 jours après son administration.(Traduit par Docteur Serge Messier).

Anti-bovine herpesvirus and anti-bovine viral diarrhea virus antibody responses in pregnant Holstein dairy cattle following administration of a multivalent killed virus vaccine.

OBJECTIVE: To determine the effect of a commercially available multivalent killed virus vaccine on serum neutralizing (SN) and colostrum neutralizing (CN) antibodies against bovine herpesvirus (BHV) type 1 and bovine viral diarrhea virus (BVDV) types 1 and 2 in pregnant dairy cattle. ANIMALS: 49 Holstein dairy cattle. PROCEDURES :25 cattle were vaccinated (IM injection) at least 60 days prior to calving (ie, at the end of the lactation period or according to the expected calving date for heifers) and again 5 weeks later. The remaining 24 cattle were not vaccinated (control group). Titers of SN antibodies were measured at the 5-week time point. Titers of SN and CN antibodies were measured at parturition. RESULTS: 5 weeks after initial vaccination, titers of SN antibodies against BHV-1 and BVDV types 1 and 2 were 1:512, 1:128, and 1:2,048, respectively, in vaccinates and 1:64, 1:128, and 1:64, respectively, in unvaccinated controls. Equivalent SN antibody titers at parturition were 1:256, 1:64, and 1:512, respectively, in vaccinates and 1:128, 1:128, and 1:64, respectively, in controls. Median titers of CN antibodies against BHV-1 and BVDV types 1 and 2 were 1:1,280, 1:10,240, and 1:20,480, respectively, in vaccinates and 1:80, 1:1,280, and 1:2,560, respectively, in controls. CONCLUSIONS AND CLINICAL RELEVANCE: Titers of antibodies against viral respiratory pathogens were significantly enhanced in both serum (BHV-1 and BVDV type 2) and colostrum (BHV-1 and BVDV types 1 and 2) in cattle receiving a killed virus vaccine (with no adverse reactions) before parturition. To maximize protection of bovine neonates, this method of vaccination should be considered.

Use of serologic tests to predict resistance to Canine distemper virus-induced disease in vaccinated dogs.

The objective of the current study was to determine whether detection of Canine distemper virus (CDV)-specific serum antibodies correlates with resistance to challenge with virulent virus. Virus neutralization (VN) assay results were compared with resistance to viral challenge in 2 unvaccinated Beagle puppies, 9 unvaccinated Beagle dogs (4.4-7.2 years of age), and 9 vaccinated Beagle dogs (3.7-4.7 years of age). Eight of 9 (89%) unvaccinated adult dogs exhibited clinical signs after virus challenge, and 1 (13%) dog died. As compared to adult dogs, the 2 unvaccinated puppies developed more severe clinical signs and either died or were euthanized after challenge. In contrast, no clinical signs were detected after challenge of the 9 adult vaccinated dogs with post-vaccination intervals of up to 4.4 years. In vaccinated dogs, the positive and negative predictive values of VN assay results for resistance to challenge were 100% and 0%, respectively. Results indicate that dogs vaccinated with modified live CDV can be protected from challenge for ≤4.4 years postvaccination and that detection of virus-specific antibodies is predictive of whether dogs are resistant to challenge with virulent virus. Results also indicate that CDV infection in unvaccinated dogs results in age-dependent morbidity and mortality. Knowledge of age-dependent morbidity and mortality, duration of vaccine-induced immunity, and the positive and negative predictive values of detection of virus-specific serum antibodies are useful in development of rational booster vaccination intervals for the prevention of CDV-mediated disease in adult dogs.

Efficacy of the canine influenza virus H3N8 vaccine to decrease severity of clinical disease after cochallenge with canine influenza virus and Streptococcus equi subsp. zooepidemicus.

Since first emerging in the North American canine population in 2004, canine influenza virus (CIV) subtype H3N8 has shown horizontal transmission among dogs, with a high level of adaptation to this species. The severity of disease is variable, and coinfection by other respiratory pathogens is an important factor in the degree of morbidity and mortality. The first influenza vaccine for dogs, an inactivated vaccine containing CIV subtype H3N8, was conditionally approved by the U.S. Department of Agriculture (USDA) for licensure in May 2009 and fully licensed in June 2010. This study evaluates the efficacy of this vaccine to reduce the severity of illness in dogs cochallenged with virulent CIV and Streptococcus equi subsp. zooepidemicus.

Seroprevalence of seasonal and pandemic influenza A viruses in domestic cats.

Infection of domestic cats with pandemic H1N1 influenza virus has recently been documented. We conducted a seroprevalence survey and found that 17 of 78 (21.8%) cats sampled during the 2009-2010 influenza season had antibody titers ≥40 against the novel H1N1 strain by hemagglutinin-inhibition assay, compared to only 1 of 39 (2.6%) sampled in 2008 prior to emergence of the pandemic (p = 0.006). Seroprevalance of seasonal H1N1 (41.9%) and H3N2 (25.6%) viruses was similarly high. These data reflecting past infection of household cats raise the possibility that they may act as a vector of influenza transmission within households.

Feline leukemia virus immunity induced by whole inactivated virus vaccination.

A fraction of cats exposed to feline leukemia virus (FeLV) effectively contain virus and resist persistent antigenemia/viremia. Using real-time PCR (qPCR) to quantitate circulating viral DNA levels, previously we detected persistent FeLV DNA in blood cells of non-antigenemic cats considered to have resisted FeLV challenge. In addition, previously we used RNA qPCR to quantitate circulating viral RNA levels and determined that the vast majority of viral DNA is transcriptionally active, even in the absence of antigenemia. A single comparison of all USDA-licensed commercially available FeLV vaccines using these modern sensitive methods has not been reported. To determine whether FeLV vaccination would prevent nucleic acid persistence, we assayed circulating viral DNA, RNA, antigen, infectious virus, and virus neutralizing (VN) antibody in vaccinated and unvaccinated cats challenged with infectious FeLV. We identified challenged vaccinates with undetectable antigenemia and viremia concomitant with persistent FeLV DNA and/or RNA. Moreover, these studies demonstrated that two whole inactivated virus (WIV) adjuvanted FeLV vaccines (Fort Dodge Animal Health's Fel-O-Vax Lv-K) and Schering-Plough Animal Health's FEVAXYN FeLV) provided effective protection against FeLV challenge. In nearly every recipient of these vaccines, neither viral DNA, RNA, antigen, nor infectious virus could be detected in blood after FeLV challenge. Interestingly, this effective viral containment occurred despite a weak to undetectable VN antibody response. The above findings reinforce the precept of FeLV infection as a unique model of effective retroviral immunity elicited by WIV vaccination, and as such holds valuable insights into retroviral immunoprevention and therapy.

Development and application of a quantitative real-time PCR assay to detect feline leukemia virus RNA.

We previously defined four categories of feline leukemia virus (FeLV) infection, designated as abortive, regressive, latent, and progressive. To determine if detectable viral DNA is transcriptionally active in the absence of antigenemia, we developed and validated a real-time viral RNA qPCR assay. This assay proved to be highly sensitive, specific, reproducible, and allowed reliable quantitation. We then applied this methodology, together with real-time DNA qPCR and p27 capsid antigen capture ELISA, to examine cats challenged with FeLV. We found that circulating viral RNA and DNA levels were highly correlated and the assays were almost in perfect agreement. This indicates that the vast majority of viral DNA is transcriptionally active, even in the absence of antigenemia. The real-time qPCR assays are more sensitive than the most commonly used FeLV diagnostic assay, the p27 capsid antigen capture ELISA. Application of qPCR assays may add greater depth in understanding of FeLV-host relationships.

A cryptic promoter in potato virus X vector interrupted plasmid construction.

BACKGROUND: Potato virus X has been developed into an expression vector for plants. It is widely used to express foreign genes. In molecular manipulation, the foreign genes need to be sub-cloned into the vector. The constructed plasmid needs to be amplified. Usually, during amplification stage, the foreign genes are not expressed. However, if the foreign gene is expressed, the construction work could be interrupted. Two different viral genes were sub-cloned into the vector, but only one foreign gene was successfully sub-cloned. The other foreign gene, canine parvovirus type 2 (CPV-2) VP1 could not be sub-cloned into the vector and amplified without mutation (frame shift mutation). RESULTS: A cryptic promoter in the PVX vector was discovered with RT-PCR. The promoter activity was studied with Northern blots and Real-time RT-PCR. CONCLUSION: It is important to recognize the homologous promoter sequences in the vector when a virus is developed as an expression vector. During the plasmid amplification stage, an unexpected expression of the CPV-2 VP1 gene (not in the target plants, but in E. coli) can interrupt the downstream work.

Leukocyte profile of cattle persistently infected with bovine viral diarrhea virus.

Animals acutely infected with bovine viral diarrhea virus (BVDV) exhibit transient immunosuppression as a result of the virus' predilection for cells that play critical roles in the host immune system. Acute BVDV infections have major effects on thymic and follicular T-lymphocytes, as well as follicular B-lymphocytes, often resulting in severe reduction in circulating numbers of lymphocytes and suppression of functional activities of these cells. Granulocytes and monocytes are equally susceptible to BVDV infections with reduction in numbers and suppression functions. However, there is limited information on the leukocyte profile of cattle persistently infected (PI) with BVDV. This study reports on phagocytic activities of granulocytes and monocytes as well as immunophenotyping by flow cytometric analysis of leukocytes isolated from healthy non-PI (NPI) and PI animals. No significant differences were found between the leukocyte profiles and the phagocytic activities of PI animals when compared to a group of healthy NPI animals.

The 2006 American Association of Feline Practitioners Feline Vaccine Advisory Panel report.

Vaccination is a medical procedure, and the decision to vaccinate should be based on a risk-based assessment for each cat and each vaccine.

Duration of immunity for canine and feline vaccines: a review.

In our studies aimed at assessing the minimum duration of vaccinal immunity (DOI), approximately 1000 dogs have been vaccinated with products from all the major US veterinary biological companies. The DOI for the various products is determined by antibody titers for all dogs and, by challenge studies in selected groups of dogs. Recently, all major companies that make canine vaccines for the U.S. market have completed their own studies; published data show a 3 years or longer minimum DOI for the canine core products, canine distemper virus (CDV), canine parvovirus type 2 (CPV-2), and canine adenovirus-2 (CAV-2). Studies with feline core vaccines - feline parvovirus (FPV), calicivirus (FCV) and herpes virus type I (FHV-1) have shown a minimum DOI of greater than 3 years. Based on these results, the current canine and feline guidelines (which recommend that the last dose of core vaccines be given to puppies and kittens > or =12 weeks of age or older, then revaccination again at 1 year, then not more often than every 3 years) should provide a level of protection equal to that achieved by annual revaccination. In contrast, the non-core canine and feline vaccines, perhaps with the exception of feline leukaemia vaccines, provide immunity for < or =1 year. In general the effectiveness of the non-core products is less than the core products. Thus, when required, non-core vaccines should be administered yearly, or even more frequently.

2006 AAHA canine vaccine guidelines.

In 2005, AAHA's Canine Vaccine Task Force met to reexamine and revise guidelines on the use of vaccines in dogs. The results of the Task Force's work are summarized and tabulated in this article and are published in their entirety on the AAHA website (www.aahanet.org). The 2006 AAHA Canine Vaccine Guidelines contain information on new technological developments in vaccines, an introduction to conditionally licensed vaccines, and detailed recommendations on the use of available vaccines. Perhaps the most noteworthy addition to the guidelines is a separate set of recommendations created for shelter facilities. Vaccines are classified as core (universally recommended), noncore (optional), or not recommended. The Task Force recognizes that vaccination decisions must always be made on an individual basis, based on risk and lifestyle factors.

Evaluation of five antibody detection tests for diagnosis of bovine paratuberculosis.

Five diagnostic tests based on enzyme-linked immunosorbent assay (ELISA) technology for bovine paratuberculosis were evaluated by using individual serum or milk samples from 359 dairy cattle in seven paratuberculosis-free herds and 2,094 dairy cattle in seven Mycobacterium paratuberculosis-infected dairy herds. Three independent laboratories using three different culture procedures completed fecal cultures for M. paratuberculosis on these cattle and found 417 cows to be shedding M. paratuberculosis in their feces. An animal that was fecal culture positive for M. paratuberculosis by any of the three laboratories was considered a confirmed case of infection. The specificity of three ELISAs (two on serum and one on milk) was > or =99.8%. The specificity of the remaining two ELISAs, both done on serum, was 94.9 and 84.7%. Four of the five ELISAs evaluated produced similar sensitivity in detecting fecal culture-positive cattle (27.8 to 28.9%). Serum ELISA "D" had the lowest specificity (84.7%) and the highest sensitivity (44.5%), but if the cutoff value defining a positive test was changed from 125 to 250% (of the positive control) the sensitivity and specificity, 31.8 and 97.5%, respectively, were comparable to those of the other four assays. If the case definition for M. paratuberculosis infection was based on the culture results of a single laboratory instead of the combined results of three laboratories, ELISA sensitivity estimates were 45.7 to 50.0%. With the exception of ELISA D, assay agreement was high (kappa 0.66 to 0.85) for categorical assay interpretations (positive or negative), but linear regression of quantitative results showed low correlation coefficients (r(2) = 0.40 to 0.68) due to the fact that ELISA results for some cows were high in one assay but low in another assay. Likelihood ratio analysis showed a direct relationship between the magnitude of ELISA result and the odds of a cow shedding M. paratuberculosis in its feces. If used judiciously and interpreted quantitatively, these ELISAs are useful tools in support of paratuberculosis control programs in dairy herds.

Evaluation of cytotoxicity and antiviral activity of recombinant human interferon alfa-2a and recombinant human interferon alfa-B/D hybrid against bovine viral diarrhea virus, infectious bovine rhinotracheitis virus, and vesicular stomatitis virus in vitro.

OBJECTIVE: To evaluate cytotoxicity and antiviral activity of recombinant human interferon alfa-2a and recombinant human interferon alfa-B/D hybrid against cytopathic and noncytopathic bovine viral diarrhea virus (BVDV), infectious bovine rhinotracheitis virus (IBRV), and vesicular stomatitis virus (VSV) in vitro. SAMPLE POPULATION: Primary bovine testicular cells and Mardin Darby bovine kidney cells. PROCEDURES: To evaluate cytotoxicity, cells were added to serial dilutions of each interferon. To evaluate antiviral activity of each interferon, interferons were serially diluted 1:10, and tissue culture cells were added; virus was then added at 3 time points. Prevention of viral infection by interferon was defined as failure to induce cytopathologic effect for VSV, IBRV, and cytopathic BVDV and failure to detect virus immunohistochemically for cytopathic and noncytopathic BVDV. RESULTS: No evidence of cytotoxicity in either cell line was detected after incubation with interferon alfa-2a or interferon alfa-B/D. However, reduced growth rates of tissue culture cells were detected for each interferon when undiluted interferon was tested. Comparable and profound antiviral activities against cytopathic and noncytopathic BVDV were evident for each interferon. Interferon alfa-2a and interferon a-B/D had comparable antiviral activities against VSV. Neither interferon had antiviral activity against IBRV. CONCLUSIONS AND CLINICAL RELEVANCE: The safety and marked in vitro antiviral activity against noncytopathic BVDV, cytopathic BVDV, and VSV suggest that interferons alfa-2a and alfa-B/D may be useful for treatment of natural disease after infection with these viruses.

Evaluation of antiviral activity and toxicity of recombinant human interferon alfa-2a in calves persistently infected with type 1 bovine viral diarrhea virus.

OBJECTIVE: To evaluate antiviral activity and toxicity of recombinant human interferon alfa-2a in calves persistently infected with noncytopathic type 1 bovine viral diarrhea virus (BVDV). ANIMALS: 5 Holstein heifers, 4 to 12 months of age. PROCEDURES: Calves persistently infected with noncytopathic type 1 BVDV were treated with recombinant human interferon alfa-2a every other day for 12 weeks. Viral loads were measured during the treatment period and compared with pre- and post-treatment values. Complete physical examinations were performed weekly, and calves were observed daily for signs of systemic illness. Complete blood counts and serum biochemical analyses were performed before, during, and after the treatment period. Because calves developed anemia during the treatment period, bone marrow biopsy specimens were collected. Antirecombinant human interferon alfa-2a antibody concentrations in serum samples obtained before, during, and after the treatment period were measured by use of an ELISA. RESULTS: Recombinant human interferon alfa-2a had no antiviral activity against noncytopathic type 1 BVDV in persistently infected calves. All calves developed microcytic anemia during the treatment period that persisted for up to 13 weeks after cessation of treatment. Anti-interferon antibodies were detected during the treatment period and persisted for at least 2 weeks after cessation of treatment. CONCLUSIONS AND CLINICAL RELEVANCE: Because of lack of in vivo antiviral activity against BVDV, recombinant human interferon alfa-2a has little promise as a therapeutic agent for the treatment of BVDV infection, at least in persistently infected cattle. Furthermore, treatment was associated with adverse immunologic and hematologic effects.

Report of the American Animal Hospital Association (AAHA) Canine Vaccine Task Force: executive summary and 2003 canine vaccine guidelines and recommendations.

The AAHA has undertaken the development of this document in an effort to inform veterinary practitioners, clarify misunderstandings held by veterinarians, and encourage practitioners to recognize that immunization of patients is a medical procedure. As such, it is bound by the same tenets that govern the recommendation of other medical procedures-principally, that it be tailored to the needs of the individual patient. Many diseases we immunize against are ubiquitous. Many are serious and some even life threatening. Some are of limited demographic concern given the exposure risk for each patient. These factors have all been considered in developing the AAHA Canine Vaccination Guidelines. In the end, each veterinarian must do what he or she determines to be in the best interest of the patient. Vaccination of individual animals produces not only individual immunity but also population or herd immunity. Since we have no readily available and reliable way to determine if each patient has developed an adequate immune response, we encourage the practice philosophy of vaccinating more patients while vaccinating each patient no more than needed.

Spurious hyperphosphatemia in a dog with chronic lymphocytic leukemia and an IgM monoclonal gammopathy.

Spurious hyperphosphatemia was diagnosed in a 6-year-old, neutered female, mixed-breed dog with chronic lymphocytic leukemia associated with an IgM monoclonal gammopathy. The spurious hyperphosphatemia was probably caused by paraprotein precipitation which interfered with the ASTRA 8 automated analyzer measurements. Serial dilutions of the sample did not change the phosphorus value. Another analyzer system in which a protein-free sample was prepared prior to analysis gave a normal serum phosphorus concentration. There was a linear relationship between the amount of paraprotein and the measured total serum inorganic phosphate (r=0.75). A review of 700 chemistry profiles from dogs and cats and a review of 36 cases with polygonal gammopathy and 6 cases with monoclonal gammopathy did not reveal other cases of spurious hyperphosphatemia.