RESUMEN
Vaccination is the main tool for controlling infectious diseases in livestock. Yet current vaccines only provide partial protection raising concerns about vaccine effectiveness in the field. Two successive transmission trials were performed involving 52 pigs to evaluate the effectiveness of a Porcine Reproductive and Respiratory Syndrome (PRRS) vaccinal strain candidate against horizontal transmission of a virulent heterologous strain. PRRS virus, above the specified limit of detection, was observed in serum and nasal secretions for all but one pig (the exception only tested positive for serum), indicating that vaccination did not protect pigs from becoming infected and shedding the heterologous strain. However, vaccination delayed the onset of viraemia, reduced the duration of shedding and significantly decreased viral load throughout infection. Serum antibody profiles indicated that 4 out of 13 (31%) vaccinates in one trial had no serological response (NSR). A Bayesian epidemiological model was fitted to the data to assess the impact of vaccination and presence of NSRs on PRRS virus transmission dynamics. Despite little evidence for reduction in the transmission rate, vaccinated animals were on average slower to become infectious, experienced a shorter infectious period and recovered faster. The overall PRRSV transmission potential, represented by the reproductive ratio R0 was lower for the vaccinated animals, although there was substantial overlap in the credibility intervals for both groups. Model selection suggests that transmission parameters of vaccinated pigs with NSR were more similar to those of unvaccinated animals. The presence of NSRs in a population, however, seemed to only marginally affect the transmission dynamics. The results suggest that even when vaccination can't prevent infection, it can still have beneficial impacts on the transmission dynamics and contribute to reducing a herd's R0. However, biosecurity and other measures need to be considered to decrease contact rates and lower R0 below 1.
Asunto(s)
Síndrome Respiratorio y de la Reproducción Porcina , Porcinos/virología , Vacunación/veterinaria , Vacunas Virales/inmunología , Animales , Anticuerpos Antivirales/sangre , Número Básico de Reproducción , Teorema de Bayes , Síndrome Respiratorio y de la Reproducción Porcina/prevención & control , Síndrome Respiratorio y de la Reproducción Porcina/transmisión , Virus del Síndrome Respiratorio y Reproductivo Porcino , Vacunas Atenuadas/inmunología , Viremia , Esparcimiento de VirusRESUMEN
Canine leishmaniasis is an important zoonosis caused by uncontrolled infection with Leishmania infantum, where an inappropriate immune response is not only responsible for permitting this intracellular parasite to multiply, but is also responsible for several of the pathological processes seen in this disease. Effective canine vaccines are therefore a highly desirable prevention tool. In this randomised, double-blinded, controlled trial, the efficacy of the LiESP/QA-21 vaccine (CaniLeish, Virbac, France) was assessed by exposing 90 naïve dogs to natural L. infantum infection during 2 consecutive transmission seasons, in two highly endemic areas of the Mediterranean basin. Regular PCR, culture, serological and clinical examinations were performed, and the infection/disease status of the dogs was classified at each examination. The vaccine was well-tolerated, and provided a significant reduction in the risk of progressing to uncontrolled active infection (pâ=â0.025) or symptomatic disease (pâ=â0.046), with an efficacy of 68.4% and a protection rate of 92.7%. The probability of becoming PCR positive was similar between groups, but the probability of returning to a PCR negative condition was higher in the vaccinated group (pâ=â0.04). In conclusion, we confirmed the interest of using this vaccine as part of a comprehensive control program for canine leishmaniasis, and validated the use of a protocol based on regular in-depth assessments over time to assess the efficacy of a canine leishmaniasis vaccine.
Asunto(s)
Enfermedades de los Perros/prevención & control , Enfermedades Endémicas/veterinaria , Leishmania infantum/inmunología , Vacunas contra la Leishmaniasis/administración & dosificación , Leishmaniasis Visceral/veterinaria , Animales , Enfermedades de los Perros/inmunología , Enfermedades de los Perros/transmisión , Perros , Método Doble Ciego , Enfermedades Endémicas/prevención & control , Femenino , Insectos Vectores/parasitología , Italia , Leishmania infantum/genética , Leishmaniasis Visceral/prevención & control , Leishmaniasis Visceral/transmisión , Masculino , Phlebotomus/parasitología , EspañaRESUMEN
The SAG2 vaccine (RABIGEN® SAG2) is a modified live attenuated rabies virus vaccine, selected from the SAD Bern strain in a two-step process of amino acid mutation using neutralizing monoclonal antibodies. The strain is genetically stable and does not spread in vivo or induce a persistent infection. Its absence of residual pathogenicity was extensively demonstrated in multiple target and non target species (such as wild carnivores and rodent species), including non-human primates. The efficacy of SAG2 baits was demonstrated according to the EU requirements for the red fox and raccoon dog. The use of safe and potent rabies vaccines such as SAG2 largely contributed to the elimination of rabies in Estonia, France, Italy and Switzerland. Importantly, these countries were declared free of rabies after few years of oral vaccination campaigns with SAG2 baits distributed with an appropriate strategy. The excellent tolerance of the SAG2 vaccine has been confirmed in the field since its first use in 1993. No safety issues have been reported, and in particular no vaccine-induced rabies cases were diagnosed, after the distribution of more than 20 million SAG2 baits in Europe.
Asunto(s)
Zorros , Vacunas Antirrábicas/administración & dosificación , Virus de la Rabia/fisiología , Rabia/veterinaria , Perros Mapache , Administración Oral , Animales , Erradicación de la Enfermedad , Europa (Continente) , Rabia/prevención & control , Vacunas Antirrábicas/genética , Vacunas Antirrábicas/normas , Vacunación/veterinaria , Vacunas Atenuadas/administración & dosificación , Vacunas Atenuadas/genéticaRESUMEN
Control of canine leishmaniasis is an important objective for the benefit of dogs living in or visiting endemic areas and for public health because of the zoonotic nature of this disease. Resistance or susceptibility to developing canine leishmaniasis after exposure to Leishmania infantum is primarily determined by the ability of the immune system to develop an appropriate Th1-dominated specific response to the parasite. For this reason there is a need for effective canine vaccines that can decrease the number of dogs developing progressive infections. In this study, we followed the impact of the LiESP/QA-21 canine vaccine (composed of excreted-secreted proteins of L. infantum and the QA-21 saponin adjuvant), recently launched commercially in Europe, on selected humoral and cellular immune parameters following an infectious intravenous challenge with L. infantum promastigotes administered one year after the primary vaccine course. We also followed parasitological parameters to determine the parasitological status of the challenged dogs. In contrast to controls, vaccinated dogs retained significantly stronger cell-mediated immune responses against the parasite despite a virulent challenge and had significantly lower mean parasite burdens at the end of the study, associated with a lower probability of developing active infections. These results confirm that the immune responses generated by vaccination with LiESP/QA-21 are still effective against an intravenous challenge one year after the primary vaccine course.
Asunto(s)
Inmunidad Adaptativa , Enfermedades de los Perros/prevención & control , Leishmania infantum/inmunología , Vacunas contra la Leishmaniasis/inmunología , Leishmaniasis Visceral/veterinaria , Células TH1/inmunología , Animales , Médula Ósea/parasitología , Enfermedades de los Perros/parasitología , Perros , Femenino , Esquemas de Inmunización , Vacunas contra la Leishmaniasis/administración & dosificación , Leishmaniasis Visceral/parasitología , Leishmaniasis Visceral/prevención & control , Masculino , Carga de Parásitos/veterinaria , Factores de TiempoRESUMEN
Canine leishmaniasis, an important zoonotic disease of dogs, is the result of an ineffective and inappropriate immune response to infection with Leishmania infantum. It is widely accepted that the appropriate immune response is characterised by a T-helper (Th)1-dominated profile in an overall mixed Th1/Th2 response. The absence of a strong Th1 response is associated with progression to the clinical disease. Thus, there is a need for an effective vaccine that could modulate the immune response to a more appropriate profile against the parasite. In this study we measured the impact of the LiESP/QA-21 canine vaccine, recently launched commercially in Europe, on selected humoral and cellular immune markers for one year after a primary vaccination course. The humoral response to vaccination was characterised by a predominantly IgG2 profile. Vaccinated dogs developed long-lasting cell-mediated immune responses against L. infantum, specifically with a stronger ability of macrophages to reduce intracellular parasite burdens in co-culture with autologous lymphocytes compared to control dogs (p=0.0002), which was correlated with induction of inducible nitric oxide synthase (iNOS) and production of nitric oxide (NO) derivatives. These results confirm that vaccination with LiESP/QA-21 is capable of inducing an appropriate Th1-dominated immune profile which persists for a full year.
Asunto(s)
Enfermedades de los Perros/prevención & control , Leishmania infantum/inmunología , Vacunas contra la Leishmaniasis/administración & dosificación , Leishmaniasis Visceral/veterinaria , Animales , Anticuerpos Antiprotozoarios/biosíntesis , Enfermedades de los Perros/inmunología , Perros , Femenino , Inmunidad Celular , Inmunidad Humoral , Inmunoglobulina G/biosíntesis , Leishmaniasis Visceral/inmunología , Leishmaniasis Visceral/prevención & control , Masculino , Células TH1/inmunología , Factores de Tiempo , Vacunación/veterinaria , Zoonosis/inmunología , Zoonosis/prevención & controlRESUMEN
Feline calicivirus (FCV) is a common feline pathogen with a potential for antigenic diversity. This study aimed to evaluate and characterize the protective efficacy of the FCV-F9 valency of a tetravalent vaccine, Leucofeligen, against challenge with an unrelated strain. Ten 9-week-old kittens were vaccinated while 10 remained as unvaccinated controls. The vaccinated cats received Leucofeligen twice subcutaneously with a 3-week interval. Four weeks after the second vaccination, all cats were challenged with virulent heterologous FCV and followed up for 21 days, monitoring their general condition, clinical signs, and immunological responses. During the vaccination phase, rectal temperatures and body weights were indistinguishable between the two groups. Only vaccinated cats showed FCV-specific seroconversion (both total and neutralizing antibodies). In the first week after challenge, the vaccinated cats had an 82.6% reduction in median clinical score compared to controls. Leucofeligen was thus shown to provide a significant clinical protection to kittens challenged with heterologous virulent FCV. This protection was similar whether the cats had neutralizing antibody or not, indicating a key role for cellular immunity in the overall protection. This also suggests that previously reported seroneutralisation studies may underestimate the level of cross-protection against field strains obtained with this modified live FCV-F9 vaccine.
RESUMEN
Canine leishmaniasis is an important zoonotic disease of dogs. The clinical outcome of infection is variable, with the efficiency of the immune response being the key determining factor. There is now a general consensus that a predominant Th1 immune profile in an overall mixed Th1/Th2 response is associated with resistance in dogs, and the absence of a strong Th1 influence is associated with a progression to clinical disease. As a result, there has been a growing demand for vaccines that can induce a specific, strong Th1 response. In this study, we measured the impact of a primary course of a newly available LiESP/QA-21 vaccine on selected humoral and cellular markers of the canine immune response during the onset of immunity. All vaccinated dogs developed a humoral response characterised by IgG2 production. More importantly, vaccinated dogs developed significantly stronger cell-mediated immunity responses than did control dogs. Vaccination induced specific cellular reactivity to soluble Leishmania antigens, with a Leishmania-specific lymphoproliferation (pâ=â0.0072), characterised by an increased population of T lymphocytes producing IFN-γ (pâ=â0.0021) and a significant ability of macrophages to reduce intracellular parasite burdens in vitro after co-culture with autologous lymphocytes (pâ=â0.0014). These responses were correlated with induction of the NOS pathway and production of NO derivatives, which has been shown to be an important leishmanicidal mechanism. These results confirm that vaccination with LiESP/QA-21 induces an appropriate Th1-profile cell-mediated response within three weeks of completing the primary course, and that this response effectively reduces the parasite load in pre-infected macrophages in vitro.
Asunto(s)
Vacunas contra la Leishmaniasis/administración & dosificación , Vacunas contra la Leishmaniasis/inmunología , Células TH1/inmunología , Animales , Anticuerpos Antiprotozoarios/sangre , Proliferación Celular , Perros , Femenino , Inmunoglobulina G/sangre , Interferón gamma/metabolismo , Leucocitos Mononucleares/inmunología , Macrófagos/inmunología , Masculino , Óxido Nítrico/metabolismoRESUMEN
Prevention of urinary shedding of Leptospira interrogans spp. by chronically infected dogs remains a key objective of the vaccination in dogs against leptospirosis which is a zoonotic disease. An inactivated bivalent vaccine composed of Leptospira interrogans serovars icterohaemorrhagiae [L. icterohaemorrhagiae] and canicola [L. canicola] bacterins was tested for its ability to protect puppies against a challenge exposure with L. icterohaemorrhagiae. The vaccine was administered twice at a 3-week interval to six puppies aged from 8 to 9 weeks. Six other puppies were used as unvaccinated controls. All puppies were challenged 2 weeks after the second vaccine injection by intraperitoneal (IP) administration of L. icterohaemorrhagiae (day 0). Clinical signs, haematological and biochemical changes and evidence of Leptospira in blood, urine and kidney were monitored for 4 weeks after the challenge exposure (days 0-28). Puppies were euthanised on day 28 for post-mortem and histological examinations of liver and kidney. Control group presented clinical pictures of severe or subclinical infection. One dog developed severe clinical signs (hypothermia, depression, anorexia, abdominal pain, dehydration, icterus, weight loss) and died on post-infection day (PID) 7 due to an acute renal failure. Gross and microscopic lesions were in accordance with this clinical pattern. In the five remaining control dogs, the challenge exposure induced mainly a systemic infection including leptospiraemia, leptospiruria and renal carriage. The vaccinated group remained healthy throughout the study period. In conclusion, immunisation with a Leptospira vaccine was shown to protect dogs against symptomatology and leptospiraemia, urine shedding and renal infection.
Asunto(s)
Vacunas Bacterianas , Enfermedades de los Perros/prevención & control , Enfermedades Renales/veterinaria , Leptospirosis/veterinaria , Animales , Anticuerpos Antibacterianos/sangre , Perros , Enfermedades Renales/microbiología , Enfermedades Renales/prevención & control , Leptospira interrogans/inmunología , Leptospirosis/prevención & controlRESUMEN
Canine parvoviral enteritis continues to cause significant morbidity and mortality in dogs worldwide, and efficacious antiviral therapies are lacking. The present trial was aimed at evaluating the therapeutic efficacy of a recombinant feline interferon (type omega) preparation in the treatment of parvoviral enteritis in dogs. A double-blind, placebo-controlled challenge trial was performed in beagle pups (8-9 weeks); clinical signs, body weight, hematologic parameters, and mortality were monitored for a period of 14 days after challenge. Fourteen animals were inoculated with virulent canine parvovirus; 10 animals that developed clinical signs thereby meeting the inclusion criteria were admitted to the treatment phase in two randomly selected groups (placebo and IFN) of equal size. The IFN group received daily intravenous injections of rFeIFN-omega (2.5 MU/kg) for three consecutive days. The placebo group received daily injections of saline without IFN. Both groups of animals received individual supportive treatment consisting of adjusted diet and electrolyte solution. All five dogs in the placebo group developed fulminating enteritis with typical clinical signs and died within 10 days post-inoculation (or 6 days post-treatment). In the IFN-treated group, one animal died on day 2 after the treatment was started, whereas the other four dogs survived the challenge and gradually recovered. Our data confirm that the rFeIFN-omega can exert a significant therapeutic effect on dogs with parvoviral enteritis by improving clinical signs and reducing mortality.