Israel Quijano-Hernández

Advances and challenges towards a vaccine against Chagas disease

Chagas disease is major public health problem, affecting nearly 10 million people, characterized by cardiac alterations leading to congestive heart failure and death of 20-40% of the patients infected with Trypanosoma cruzi, the protozoan parasite responsible for the disease. A vaccine would be key to improve disease control and we review here the recent advances and challenges of a T. cruzi vaccine. There is a growing consensus that a protective immune response requires the activation of a Th1 immune profile, with the stimulation of CD8+ T cells. Several vacines types, including recombinant proteins, DNA and viral vectors, as well as heterologous prime-boost combinations, have been found immunogenic and protective in mouse models, providing proof-of-concept data on the feasibility of a preventive or therapeutic vaccine to control a T. cruzi infection. However, several challenges such as better end-points, safety issues and trial design need to be addressed for further vaccine development to proceed.

Immunopathology of natural infection with Trypanosoma cruzi in dogs

Chagas disease is caused by Trypanosoma cruzi and dogs are an important reservoir of the parasite as well as a good model for the study of the pathogenesis of the disease. We aimed here at characterizing the immunopathology of naturally infected dogs in Merida, Yucatan, Mexico. Following an initial screening for T. cruzi seropositive stray dogs, we examined 9 seropositive and 10 seronegative animals. High lymphocytes and low monocytes counts were observed in peripheral blood from seropositives dogs. Three of nine seropositive dogs presented electrocardiographic alterations including right bundle branch block, sinusal block and QRS complex alterations and some right ventricle enlargement was noted. Histopathologic analysis of cardiac walls revealed significant inflammation with a clear tropism for the right ventricle, although most walls were affected. Seropositive dogs presented low IgG1 and high IgG2 levels. Higher IgG1 levels were associated with increased cardiac index and myocarditis, suggesting that a Th2 immune response leads to susceptibility and increased disease severity. These observations shed some light on the mechanisms of pathogenesis of Chagas disease in dogs, and provide a good framework for the evaluation of novel drugs and vaccines in this animal model.

Preventive and therapeutic DNA vaccination partially protect dogs against an infectious challenge with Trypanosoma cruzi.

American trypanosomiasis, or Chagas disease, is caused by Trypanosoma cruzi, and a vaccine would greatly improve disease control. While some studies in mice suggest that a vaccine is feasible, limited efficacy has been observed in dogs. We evaluated here the safety and efficacy of a DNA vaccine encoding TSA-1 and Tc24 antigens in a dog model of acute T. cruzi infection. Mongrel dogs were immunized with two doses of 500 μg of DNA vaccine, two weeks apart, and infected with T. cruzi (SylvioX10/4 strain) two weeks after the second vaccine dose. Another group of dogs was infected first and treated with the vaccine. Disease progression was monitored for up to 70 days post-infection. The vaccine did not induce any critical change in blood parameters, nor exacerbation of disease in vaccinated animals. On the contrary, it prevented anemia and a decrease in lymphocyte counts following T. cruzi infection in vaccinated dogs. Both preventive and therapeutic vaccination significantly reduced parasitemia, cardiac inflammation and cardiac parasite burden, and tended to reduce the development of cardiac arrhythmias. These results indicate that a preventive or therapeutic DNA vaccine encoding TSA-1 and Tc24 antigens is safe and may reduce both parasite transmission and the clinical progression of Chagas disease in vaccinated dogs. This DNA vaccine may thus be an excellent veterinary vaccine candidate. These data also further strengthen the feasibility of a Chagas disease vaccine for humans.

Identification of a new genotype of canine distemper virus circulating in America

Canine Distemper is a highly contagious viral systemic disease that affects a wide variety of terrestrial carnivores. Canine Distemper virus (CDV) appears genetically heterogeneous, markedly in the hemagglutinin protein (H), showing geographic patterns of diversification that are useful to monitor CDV molecular epidemiology. In Mexico the activity of canine distemper remains high in dogs, likely because vaccine prophylaxis coverage in canine population is under the levels required to control effectively the disease. By phylogenetic analysis based on the nucleoprotein (N) and on the H genes, Mexican CDV strains collected between 2007 and 2010 were distinguished into several genovariants, all which constituted a unique group, clearly distinct from field and vaccine strains circulating worldwide, but resembling a CDV strain, 19876, identified in Missouri, USA, 2004, that was genetically unrelated to other North-American CDV strains. Gathering information on the genetic heterogeneity of CDV on a global scale appears pivotal in order to investigate the origin and modalities of introduction of unusual/novel CDV strains, as well as to understand if vaccine breakthroughs or disease epidemics may be somewhat related to genetic/antigenic or biological differences between field and vaccine strains.

Dirofilaria immitis and Trypanosoma cruzi natural co-infection in dogs.

Dirofilariasis (Dirofilaria immitis) and American trypanosomiasis (Trypanosoma cruzi) are zoonotic parasitic diseases affecting the hearts of a variety of mammalian host species, including dogs. In this study, some of the immunopathological characteristics of natural co-infection by these two parasites were compared with T. cruzi infection in dogs from Mexico. Antibody analysis in serum indicated significantly lower anti-T. cruzi IgG levels in co-infected dogs (n = 4) compared to those with T. cruzi infection alone (n = 9), together with a somewhat lower IgG2/IgG1 ratio. Cardiac tissue inflammation was limited and focal in co-infected animals whereas T. cruzi infected dogs had extensive and diffuse tissue inflammation. Three out of nine T. cruzi infected dogs and 1/4 of T. cruzi and D. immitis co-infected dogs showed cardiac alterations. The results showed that co-infections may interfere with host responses, and their significant prevalence (4/13 T. cruzi infected dogs) suggests that they should be taken into account by researchers and clinicians.

Evaluation of clinical and immunopathological features of different infective doses of Trypanosoma cruzi in dogs during the acute phase

Infection with Trypanosoma cruzi is a major risk in Latin America, and dogs are believed to be good models for evaluating Chagas disease. Here, we evaluated the clinical and immunopathological alterations developed by mongrel dogs experimentally infected with different infective doses (2,000, 20,000, and 200,000 metacyclic trypomastigotes of Sylvio X10/4 strain kg−1 via intraperitoneal). Clinical and electrocardiographic parameters, as well as antibody production and pathologic lesions were evaluated. All three doses of this strain of T. cruzi induced a similar pattern of infection characterized by cardiac arrhythmias and severe and diffuse myocarditis. Specific anti-T. cruzi IgG indicated seroconversion by day 14 after infection, and IgG levels increased during the period of evaluation. Mortality was observed only in dogs infected with the medium or high parasite doses, but not in the group infected with a low dose of 2,000 parasites kg−1. Infection with a low dose of parasites provides an excellent nonlethal model to evaluate the immunopathology of the acute disease in dogs infected with the Sylvio X10/4 strain of T. cruzi.

Reliability of clinical diagnosis and laboratory testing techniques currently used for identification of canine parvovirus enteritis in clinical settings

Canine parvovirus type 2 (CPV-2) is the main etiological agent of viral enteritis in dogs. Actually in literature, CPV-2 has been reported with clinical signs that vary from the classical disease, and immunochromatography test and PCR technique have been introduced to veterinary hospitals to confirm CPV-2 diagnosis and other infections. However, the reliability of these techniques has been poorly analyzed. In this study, we evaluated the sensitivity and specificity of veterinary clinical diagnosis, immunochromatography test and PCR technique. Our data indicate that variations in the clinical signs of CPV-2 complicate the gathering of an appropriate diagnosis; and immunochromatography test and PCR technique do not have adequate sensitivity to diagnose positive cases.

Identification molecular and clinical characterization of CPV-2c in dogs from the state of Mexico.

Canine parvovirus type 2 (CPV-2) is the main etiological agent of viral enteritis in dogs. Actually in literature, CPV-2 has been reported with clinical signs that vary from the classical disease. In this study, we evaluated the clinical signs presented in 50 dogs infected naturally with CPV-2. All the infected dogs were analyzed by PCR and sequenced. Our data indicate that the CPV-2c is the most frequently genovariant in Mexico the 50 dogs belong to the CPV-2c, through the amino acid change 426 Asn-Glu and concerning clinical signs, the presence of either vomiting or enlarged lymph node was observed in all virally infected patients.

INTERMITTENT GASTROESOPHAGEAL INTUSSUSCEPTION IN A KITTEN RESOLVED WITH A PERCUTANEOUS GASTROPEXY

Abstract Gastroesophageal intussusception is a rare pathology characterized by an acute or intermittent invagination of the stomach into the lumen caudal to the thoracic esophagus, the pathogenesis is not well understood, although it is likely multifactorial. The mortality is high, associated with a late diagnosis and a rapid deterioration. A 4-month-old male domestic shorthair kitten presented for evaluation of intermittent respiratory distress and abdominal discomfort with two weeks of evolution. Based on clinical history, clinical sings and imaging studies a diagnosis of intermittent gastroesophageal intussusception was established. The reduction of the intussusception was performed with endoscopy maneuvers and with medical and nutritional management for some days, but this failed and finally was reduced with a percutaneous gastropexy tube to prevent recurrence with a good long-term outcome. Gastroesophageal intussusception in cats is associated with megaesophagus or hiatal hernia, and should be considered as a differential diagnosis in patients with chronic vomiting, regurgitation or respiratory disease. Survey and contrasted thoracic radiographs can be used to identify gross anatomical abnormalities, but the definitive diagnosis should be made by esophagogastroscopy with the possibility of reducing the intussusception. The use of percutaneous gastropexy provides other possible option to conventional surgery for the management of this pathology in cats.

Respuesta del Tumor Venéreo Transmisible Canino a Presentaciones de Vincristina de Patente y Genérica

The aim of this study was to compare the response of naturally infected dogs with transmissible venereal tumor (TVT) to treatment with two sources of vincristine: patented and generic. Twelve naturally infected dogs diagnosed with TVT by cytology and PCR