Vertical transmission efficiency and insecticidal properties of Spodoptera exigua Nucleopolyhedrovirus (SeMNPV) genotypes for their use in biological control

El nucleopoliedrovirus de Spodoptera exigua (SeMNPV) es un patógeno natural de las poblaciones larvarias de S. exigua que constituye la base de un bioinsecticida comercializado en España para el control biológico de esta plaga en pimiento. Recientes estudios han demostrado que la transmisión del virus a la descendencia (transmisión vertical) se da con frecuencia y podría ser una característica deseable para su uso en aplicaciones de campo. En el presente trabajo se discute la conveniencia de utilizar una mezcla de dos genotipos SeAl1 (transmisión vertical) y SeG25 (transmisión horizontal) en determinadas proporciones para mejorar las características que cada uno de ellos presenta por separado y así explotar cada una de las vías de transmisión. La patogenicidad (CL50) del genotipo SeG25, y de cualquiera de las mezclas que contienen un 25, 50 o 75 % del mismo, fue más alta que la del aislado SeAl1. Sin embargo, en términos de virulencia (TMM) y productividad (OBs/larva) no se observaron diferencias significativas entre genotipos ni entre sus mezclas. Además se evaluó la capacidad de producir infecciones encubiertas de cada genotipo y sus mezclas sometiendo larvas de S. exigua a infecciones subletales del virus. Se encontraron transcritos del virus para el gen temprano ie0 mediante RT-PCR en los adultos supervivientes a infecciones provocadas por el genotipo SeG25 y todas las mezclas. También se testaron otros dos genes virales que se expresan de manera temprana y tardía en la infección de baculovirus (DNA-polimerasa y polihedrina) para los que en ningún caso se detectaron transcritos.

A mathematical model for the dynamics of Banana Xanthomonas Wilt with vertical transmission and inflorescence infection

A mathematical model for Banana Xanthomonas Wilt (BXW) spread by insect is presented. The model incorporates inflorescence infection and vertical transmission from the mother corm to attached suckers, but not tool-based transmission by humans. Expressions for the basic reproduction number R0 are obtained and it is verified that disease persists, at a unique endemic level, when R0 > 1. From sensitivity analysis, inflorescence infection rate and roguing rate were the parameters with most influence on disease persistence and equilibrium level. Vertical transmission parameters had less effect on persistence threshold values. Parameters were approximately estimated from field data. The model indicates that single stem removal is a feasible approach to eradication if spread is mainly via inflorescence infection. This requires continuous surveillance and debudding such that a 50% reduction in inflorescence infection and 2–3 weeks interval of surveillance would eventually lead to full recovery of banana plantations and hence improved production.

Vertical transmission of hepatitis C virus: A tale of multiple outcomes

Globally, hepatitis C virus (HCV) infection affects approximately 130 million people and 3 million new infections occur annually. HCV is also recognized as an important cause of chronic liver disease in children. The absence of proofreading properties of the HCV RNA polymerase leads to a highly error prone replication process, allowing HCV to escape host immune response. The adaptive nature of HCV evolution dictates the outcome of the disease in many ways. Here, we investigated the molecular evolution of HCV in three unrelated children who acquired chronic HCV infection as a result of mother-to-child transmission, two of whom were also coinfected with HIV-1. The persistence of discrete HCV variants and their population structure were assessed using median joining network and Bayesian approaches. While patterns of viral evolution clearly differed between subjects, immune system dysfunction related to HIV coinfection or persistent HCV seronegativity stand as potential mechanisms to explain the lack of molecular evolution observed in these three cases. In contrast, treatment of HCV infection with PegIFN, which did not lead to sustained virologic responses in all 3 cases, was not associated with commensurate variations in the complexity of the variant spectrum. Finally, the differences in the degree of divergence suggest that the mode of transmission of the virus was not the main factor driving viral evolution. (C) 2013 Elsevier B. V. All rights reserved.

Vertical transmission of a fluoroquinolone-resistant Escherichia coli within an integrated broiler operation

The epidemiology of an enrofloxacin-resistant Escherichia coli clone was investigated during two separate outbreaks of colibacillosis in the Danish broiler production. In total five flocks were reported affected by the outbreaks. Recorded first-week mortalities were in the range of 1.7-12.7%. The clone was first isolated from dead broilers and subsequently demonstrated in samples from associated hatchers and the parent flock with its embryonated eggs, suggesting a vertical transmission from the parents. The second outbreak involved two broiler flocks unrelated to the affected flocks from the first outbreak. However, the clone could not be demonstrated in the associated parent flock. Furthermore, samplings from grand-parent flocks were negative for the outbreak clone. The clonality was evaluated by plasmid profiling and pulsed-field gel electrophoresis. None of the recognized virulence factors were demonstrated in the outbreak clone by microarray and PCR assay. The molecular background for the fluoroquinolone-resistance was investigated and point mutations in gyrA and parC leading to amino-acid substitutions in quinolone-resistance determining regions of GyrA and ParC were demonstrated. Vertical transmission of enrofloxacin-resistant E. coli from healthy parents resulting in high first-week mortality in the offspring illustrates the potential of the emergence and spreading of fluoroquinolone-resistant bacteria in animal husbandry, even though the use of fluoroquinolones is restricted.

Vaccination with recombinant NcROP2 combined with recombinant NcMIC1 and NcMIC3 reduces cerebral infection and vertical transmission in mice experimentally infected with Neospora caninum tachyzoites

We investigated the protective potential of recombinant his-tagged antigens recNcMIC1, recNcMIC3 and recNcROP2, applied either as single vaccines or as vaccine combinations, in BALB/c mouse models for cerebral and fetal infection. Subsequently, mice were mated and challenged by i.p. inoculation of 2 x 10(6)Neospora caninum tachyzoites at day 7 of pregnancy. The mortality and morbidity of adult mice (non-pregnant and dams) and of the newborn pups was studied for a period of 40 days following birth. Vaccination of non-pregnant mice with recNcROP2 or combinations of recNcROP2 with recNcMIC antigens significantly reduced the numbers of mice suffering from clinical signs, and morbidity was completely prevented with the combination of all three antigens. Of the dams, the groups receiving either recNcROP2 alone or the combination of all three antigens did not exhibit any morbidity, the groups receiving ROP2 mixed with either MIC1 or MIC3 exhibited reduced numbers of deaths, and in the infection control group and the adjuvant group 50% and 43% of mice, respectively, succumbed to disease. For pups, the highest survival rates were noted for the groups receiving recNcROP2 (50%) and recNcROP2/NcMIC1/NcMIC3 (35%), while in the infection- and adjuvant- control groups all pups died, the latest at days 25 and 30, respectively. Quantification of parasite DNA by N. caninum-specific real-time PCR revealed consistently lower parasite burdens in brain tissue of pups from vaccinated groups compared with the controls. However, dense granule antigen 2 (GRA2) real-time reverse transcriptase-PCR on brain tissue of surviving pups (applied here to detect viable parasites) demonstrated that only the pups from the group vaccinated with all three antigens in combination appeared free of viable tachyzoites, while in all other groups viable parasites were still present. Serological analysis of humoral (total IgG, IgG1 and IgG2a) and serum cytokine (IL-4 and IFN-gamma) responses showed that this effect was associated with a Th-2-biased immune response, with a clearly elevated IL-4/IFN-gamma ratio in the mice receiving all three antigens in combination. In conclusion, a mixture of recombinant antigens representing important secretory micronemal and rhoptry proteins leads to a significant protection against vertical transmission of N. caninum in mice.

Repurposing of antiparasitic drugs: the hydroxy-naphthoquinone buparvaquone inhibits vertical transmission in the pregnant neosporosis mouse model.

The three anti-malarial drugs artemiside, artemisone, and mefloquine, and the naphthoquinone buparvaquone known to be active against theileriosis in cattle and Leishmania infections in rodents, were assessed for activity against Neospora caninum infection. All four compounds inhibited the proliferation of N. caninum tachyzoites in vitro with IC50 in the sub-micromolar range, but artemisone and buparvaquone were most effective (IC50 = 3 and 4.9 nM, respectively). However, in a neosporosis mouse model for cerebral infection comprising Balb/c mice experimentally infected with the virulent isolate Nc-Spain7, the three anti-malarial compounds failed to exhibit any activity, since treatment did not reduce the parasite burden in brains and lungs compared to untreated controls. Thus, these compounds were not further evaluated in pregnant mice. On the other hand, buparvaquone, shown earlier to be effective in reducing the parasite load in the lungs in an acute neosporosis disease model, was further assessed in the pregnant mouse model. Buparvaquone efficiently inhibited vertical transmission in Balb/c mice experimentally infected at day 7 of pregnancy, reduced clinical signs in the pups, but had no effect on cerebral infection in the dams. This demonstrates proof-of-concept that drug repurposing may lead to the discovery of an effective compound against neosporosis that can protect offspring from vertical transmission and disease.

Pair approximation for a model of vertical and horizontal transmission of parasites.

We apply Stochastic Dynamics method for a differential equations model, proposed by Marc Lipsitch and collaborators (Proc. R. Soc. Lond. B 260, 321, 1995), for which the transmission dynamics of parasites occurs from a parent to its offspring (vertical transmission), and by contact with infected host (horizontal transmission). Herpes, Hepatitis and AIDS are examples of diseases for which both horizontal and vertical transmission occur simultaneously during the virus spreading. Understanding the role of each type of transmission in the infection prevalence on a susceptible host population may provide some information about the factors that contribute for the eradication and/or control of those diseases. We present a pair mean-field approximation obtained from the master equation of the model. The pair approximation is formed by the differential equations of the susceptible and infected population densities and the differential equations of pairs that contribute to the former ones. In terms of the model parameters, we obtain the conditions that lead to the disease eradication, and set up the phase diagram based on the local stability analysis of fixed points. We also perform Monte Carlo simulations of the model on complete graphs and Erdös-Rényi graphs in order to investigate the influence of population size and neighborhood on the previous mean-field results; by this way, we also expect to evaluate the contribution of vertical and horizontal transmission on the elimination of parasite. Pair Approximation for a Model of Vertical and Horizontal Transmission of Parasites.

"Quando eu descobri tive um baque: os desafios da prevenção da transmissão vertical do HIV

A eficácia da quimioprofilaxia da transmissão vertical do HIV tem contribuído para minimizar o numero de crianças infectadas pelo vírus. No entanto é essencial para essa finalidade o uso correto do protocolo pela mãe. Mas onde estão as falhas desse processo? Porque ainda há crianças sendo desnecessariamente expostas ao vírus HIV? Foi objetivo desse estudo conhecer as concepções sobre gravidez, HIV/AIDS e transmissão vertical de gestantes e mães soropositivas. A partir disso, fornecer subsídios para o aperfeiçoamento da prevenção da transmissão vertical. Partiu-se da hipótese de que aspectos sociais, culturais e econômicos das mulheres podem estar envolvidos na adesão ou não da prevenção da transmissão vertical da AIDS. Quatorze mulheres soropositivas, sendo onze com filhos já nascidos e três gestantes, deram seus depoimentos através de entrevistas semi-estruturadas orientadas por roteiro. Os Fatores sócio culturais das mulheres não foram investigados de forma direta, mas foi possível registrar através das falas uma possível associação destes com a quimioprofilaxia da transmissão vertical do HIV. Ainda que de forma incompleta todas realizaram a quimioprofilaxia, com exceção de uma mulher que teve o diagnostico somente após o parto. Através da análise dos depoimentos foi possível identificar que as mulheres que possuíam nível sócio cultural mais elevado demonstraram maior domínio quanto à importância do tratamento, embora a principal motivação para a realização do tratamento tenha sido a não contaminação de seus filhos. Foram descritos alguns determinantes envolvidos na adesão das mulheres ao tratamento, dentre eles; o conhecimento acerca do tratamento e aspectos ligados aos serviços de saúde. Algumas falhas no pré-natal foram apontadas como ponto negativo neste processo. Dentre os resultados encontrados ocasionalmente foi ressaltado a forma que os companheiros reagiram à doença. E a constatação de que a grande maioria das mulheres ao não reconhecerem sua posição de risco para a infecção pelo HIV, descobrem-se soropositivas somente no pré-natal.

Influencia del sexo en la transmisión vertical del nucleopoliedrovirus de Spodoptera exigua (SeMNPV-Al1)

El ciclo ecológico de los baculovirus comprende dos vías de transmisión: la horizontal que se produce entre congéneres y la vertical, que implica el paso de genomas virales de los parentales a la progenie. Recientemente se ha estudiado la efectiva transmisión vertical del Nucleopoliedrovirus de Spodoptera exigua (SeMNPV-Al1) en una población de su húesped de los invernaderos de Almería (España). La detección de progenie infectada de hembras sanas, sugiere la necesidad de determinar el papel que juegan ambos sexos en la transmisión del virus. En el presente trabajo se establecieron infecciones subletales para obtener adultos con infecciones encubiertas y utilizando un esquema de apareamientos entre adultos sanos e infectados se verificó que la transmisión del virus es posible vía paterna o materna. La vía materna parece más constante en su respuesta de acuerdo a la medición de la carga viral obtenida en la descendencia (qPCR). El tratamiento de desinfección de la puesta no afectó a la detección de ADN viral en la descendencia, lo que sugiere una transmisión transovo. La carga viral por insecto fue similar independientemente del sexo de los parentales y la descendencia masculina y femenina se vio afectada de igual manera por la infección.

Deformed wing virus and drone mating flights in the honey bee (Apis mellifera): implications for sexual transmission of a major honey bee virus

Deformed wing virus (DWV) represents an ideal model to study the interaction between mode of transmission and virulence in honey bees since it exhibits both horizontal and vertical transmissions. However, it is not yet clear if venereal-vertical transmission represents a regular mode of transmission for this virus in natural honey bee populations. Here, we provide clear evidence for the occurrence of high DWV titres in the endophallus of sexually mature drones collected from drone congregation areas (DCAs). Furthermore, the endophallus DWV titres of drones collected at their maternal hives were no different from drones collected at nearby DCAs, suggesting that high-titre DWV infection of the endophallus does not hinder the ability of drones to reach the mating area. The results are discussed within the context of the dispersal of DWV between colonies and the definition of DWV virulence with respect to the transmission route and the types of tissues infected.

Étude du goulot d’étranglement dans la transmission mère-enfant du virus de l’hépatite C.

La transmission mère-enfant (TME) du virus de l’hépatite C (VHC) est la première cause d’acquisition de l’infection chez les enfants des pays développés. Celle-ci prend place dans <10% des cas. Toutefois, dans le cas d’une coinfection maternelle avec le virus de l’immunodéficience de type 1 (VIH-1), ce taux est accru alors qu’il n’existe aucune intervention préventive de la TME du VHC. Le VHC arbore une diversité importante qui est le résultat d’une réplication exempte de mécanisme de correction. Il est donc retrouvé chez son hôte sous la forme d’un spectre de virions génétiquement apparentés mais différents qu’on appelle quasiespèce. Lorsque le VHC est transmis entre adultes, seulement un nombre limité de variantes sont responsables de l’infection, c’est ce qu’on appelle un goulot d’étranglement génétique. L’existence d’un tel profil de transmission lors de la TME du VHC restait, jusqu’à maintenant, à confirmer. En se basant sur la détection par RT-PCR de la virémie à la naissance, la TME du VHC est réputée prendre place in utero et peripartum, une dynamique de transmission qui reste à démontrer. Ici, nous rapportons une analyse longitudinale de la TME du VHC par séquençage de nouvelle génération chez 5 paires mère-enfant dont 3 mères sont également coinfectées avec le VIH-1. L’analyse de l’identité des variantes virales basée sur la séquence nucléotidique des régions hypervariables 1-2 de la glycoprotéine E2 (positions 1491-1787 de l’isolat H77) révèle qu’un nombre limité de variantes virales sont transmises de la mère à l’enfant lorsque la mère est seulement infectée par le VHC (n = 1-4 variantes transmises). Dans le cas de la coinfection maternelle avec le VIH-1, ce nombre est toutefois drastiquement plus important (n = 111-118). La détection de variantes retrouvées chez la mère au deuxième trimestre et l’enfant mais non détectées subséquemment chez la mère témoigne que la TME du VHC peut prendre place aussi tôt que lors du deuxième trimestre de grossesse. Finalement, nous montrons que la dynamique d’infection chez l’enfant implique une augmentation transitoire de la virémie concomitante avec une perte de diversité de la quasiespèce. Dans l’ensemble ces résultats sont les premiers à démontrer directement l’existence d’un goulot d’étranglement lors de la TME du VHC. Celui-ci serait moins restringent dans le cas de la coinfection maternelle avec le VIH-1. Cette transmission peut prendre place aussi tôt que lors du deuxième trimestre de grossesse et il semblerait qu’un spectre limité de variantes soit responsable pour l’établissement de l’essentiel de la production virale chez le jeune enfant.