Elizabeth Loza-Rubio

The continuous spread of West Nile virus (WNV): seroprevalence in asymptomatic horses

West Nile virus (WNV) was probably introduced in southern and northern Mexico from the USA in two independent events. Since then, WNV activity has been reported in several Mexican states bordering the USA and the Gulf of Mexico, but disease manifestations seen there in humans and equids are quite different to those observed in the USA. We have analysed WNV seroprevalence in asymptomatic, unvaccinated equids from two Mexican states where no data had been previously recorded. WNV IgG antibodies were detected in 31.6% (91/288) of equine sera from Chiapas and Puebla states (53.3% and 8.0%, respectively). Analysis by plaque reduction neutralization test (PRNT) showed good specificity (99.4%) and sensitivity (84.9%) with the ELISA results. Further analyses to detect antibodies against three different flaviviruses (WNV, St Louis encephalitis virus, Ilheus virus) by haemagglutination inhibition (HI) tests on a subset of 138 samples showed that 53% of the 83 HI-positive samples showed specific reaction to WNV. These data suggest continuous expansion of WNV through Mexico.

Evaluation of an enzyme-linked immunosorbent assay for detection of West Nile virus infection based on a recombinant envelope protein produced in Trichoplusia ni larvae.

West Nile virus (WNV), a Flavivirus distributed most widely, is presenting lately variable epidemiological and ecological patterns, including an increasing virulence that has already caused over 1000 human deaths in USA. Currently, diagnosis of WNV is achieved mainly by enzyme-linked immunoassays (ELISAs) based on the use of inactivated whole WNV (iWNV) as antigen, although results have to be confirmed by plaque reduction neutralization tests (PRNTs). Expression of WNV envelope recombinant E (rE) protein and its usefulness as ELISA antigen are described. Production of rE was achieved upon infection of Trichoplusia ni insect larvae with a recombinant baculovirus. Once optimized, the rE-based ELISA was validated with a battery of mouse and equine sera characterized previously. Concordance with the iWNV-based ELISA used routinely was good (95%), as it was with the reference PRNT (90%), with specificity of 94.4% and sensitivity of 88.1%. Production of rE protein in insect larvae allows for an easy, low cost and quite large-scale yield of partially purified antigen which is suitable for serological diagnosis of WNV, without the need for manipulation of large quantities of infective virus.

Porcine Reproductive and Respiratory Syndrome (PRRS)

Porcine reproductive and respiratory syndrome (PRRS) is an economically frustrating viral disease of pigs, characterized by severe reproductive failure in pregnant sows and respiratory disorders in piglets and growing pigs. Several research groups around the world have developed PRRSV vaccines. Some of these have been effective; however, owing to the complications that the syndrome presents and the viral evasion of the immune system, vaccines have not always been 100% effective. Biotechnological tools, such as the generation of plant-derived vaccines, offer alternatives to obtain more stable biologics, free of fermentation and cold chains. According to the literature, these vaccines are cost effective. In this document, we present some of the vaccines that have been developed against PRRSV, both traditional and new, and describe some alternatives developed in plants.

Genomic analysis of an atypical Mexican low-pathogenic H5N2 avian influenza virus

Veterinaria Mexico OA ISSN: 2448-6760 Cite this as: Steffani Hernandez G, Chavez Maya F, Rojas Anaya E, Loza Rubio E, Garcia Espinosa G. Genomic analysis of an atypical Mexican low-pathogenic H5N2 avian influenza virus. Veterinaria Mexico OA. 2016;3(2). doi: 10.21753/vmoa.3.2.363 We analysed the genome of a low-pathogenic avian H5N2 influenza virus isolated from the faeces of experimentally infected Pekin ducks and Leghorn-type chickens to determine its origin and molecular characteristics. The complete genomic sequence was determined using a Sanger-based genome sequencing method and was subsequently characterized by phylogenetic analysis and genetic comparison. The results of this study showed that 8 genomic segments corresponded to an avian influenza virus that were related with strains isolated in Mexico. Investigation of the haemagglutinin gene revealed the presence of few basic amino acids at the cleavage site and lack of a potential N-glycosylation site at position 11. The gene encoding the PB1 protein lacked PB1-F2 and the basic polymerase gene codes for PA-X. In addition, the basic polymerase gene contained the consensus ribosomal frameshifting motif TCC TTT CGT C, which is required for the expression of the PA-X. Molecular characteristics showed that the virus has features of a low-pathogenic H5 influenza virus with the exception of a potential N-glycosylation site at position 11. The genome information for this particular virus will provide a molecular map for further in vivo studies to identify why some influenza viruses can persist in chickens for long periods of time. Such information will be useful in countries such as Mexico, where the virus has been a poultry health problem since 1994 and has the potential to evolve high pathogenicity. Figure 1. Phylogenetic tree of the HA gene of A/chicken/Mexico/2007 (H5N2) Influenza A virus [ ]. The phylogenetic tree was constructed using the neighbour-joining method. The percentages of replicate trees in which the associated taxa clustered together in a bootstrap test (1,000 replicates) are shown next to the branches. The evolutionary distances were computed using the Kimura 2-parameter method. The analysis involved 101 chicken nucleotide sequences. Evolutionary analyses were conducted in MEGA 5.05. A larger triangle size represents a larger number of nucleotide sequences with genetic relationship.

Prevalence of neutralizing antibodies against West Nile virus (WNV) in monkeys (Ateles geoffroyi and Alouatta pigra) and crocodiles (Crocodylus acutus and C. acutus–C. moreletti hybrids) in Mexico

West Nile virus (WNV) is a mosquito-borne neurotropic viral pathogen maintained in an enzootic cycle between mosquitoes (vectors) and birds (natural hosts) with equids, humans, and other vertebrates acting as dead-end hosts. WNV activity in Mexico has been reported in several domestic and wild fauna and in humans, and the virus has been isolated from birds, mosquitoes, and humans. However, no serological studies have been conducted in monkeys, and only two in a limited number of crocodiles (Crocodylus moreletii). Here we present data on the prevalence of neutralizing antibodies against WNV in 53 healthy wild monkeys (49 Ateles geoffroyi and four Alouatta pigra), and 80 semi-captive healthy crocodiles (60 C. acutus and 20 C. acutus-C. moreletti hybrids) sampled during 2012. None of the monkey sera neutralized WNV, whereas 55% of the crocodile sera presented neutralizing antibodies against WNV. These results can contribute to the design of surveillance programmes in Mexico.

Edible Rabies Vaccines

Rabies has been one of the most feared diseases throughout history. Human rabies remains an important public health problem in many developing countries. The WHO reports that more than 55,000 people die of this disease every year. Most of these cases occur in developing countries. In most Latin American countries, the major reservoirs of rabies are the dog and the hematophagous bat (Desmodus rotundus), which is present in the tropical and subtropical areas from Northern Mexico to Northern Argentina and Chile and transmits the disease to cattle. One of the better options for controlling rabies is vaccination. The expression of rabies virus G protein in different plant systems for developing an oral rabies vaccine could reduce costs of production and distribution and would be convenient for developing countries where the disease is endemic.