[Oligoryzomys longicaudatus characteristics' associated with the presence of Andes virus (Hantavirus)]. / Características de Oligoryzomys longicaudatus asociadas a la presencia del virus Andes (Hantavirus).

Oligoryzomys longicaudatus is the main reservoir of Andes virus (AND), which causes hantavirus pulmonary syndrome in Patagonia. The factors associated with the presence of antibodies against AND in this species are unknown. This study used a logistic regression model to analyze which characteristics of O. longicaudatus, captured in northern Argentinean Patagonia, led to an increased probability of an animal having antibodies against AND and to relate these characteristics to possible mechanisms of transmission of the virus within the population. Sex, age, body mass, and wounds were important predictors regarding the presence of antibodies against AND within O. longicaudatus populations. The probability of a wounded male O. longicaudatus adult having AND antibodies increased in parallel with the body mass. The probability of having antibodies was more than 80% in individuals with body masses above 44 gram. However, the possible transmission mechanism of AND within O. longicaudatus population is still uncertain and further studies involving a larger number of individuals and prolonged monitoring including the process of seroconversion are needed.

Características de Oligoryzomys longicaudatus asociadas a la presencia del virus Andes (Hantavirus) / Oligoryzomys longicaudatus characteristics' associated with the presence of Andes virus (Hantavirus)

Oligoryzomys longicaudatus is the main reservoir of Andes virus (AND), which causes hantavirus pulmonary syndrome in Patagonia. The factors associated with the presence of antibodies against AND in this species are unknown. This study used a logistic regression model to analyze which characteristics of O. longicaudatus, captured in northern Argentinean Patagonia, led to an increased probability of an animal having antibodies against AND and to relate these characteristics to possible mechanisms of transmission of the virus within the population. Sex, age, body mass, and wounds were important predictors regarding the presence of antibodies against AND within O. longicaudatus populations. The probability of a wounded male O. longicaudatus adult having AND antibodies increased in parallel with the body mass. The probability of having antibodies was more than 80% in individuals with body masses above 44 gram. However, the possible transmission mechanism of AND within O. longicaudatus population is still uncertain and further studies involving a larger number of individuals and prolonged monitoring including the process of seroconversion are needed.

Oligoryzomys longicaudatus es el principal reservorio del virus Andes Sur (AND) causante del síndrome pulmonar por hantavirus en la Patagonia. Aún se desconoce qué características individuales están asociadas a una mayor presencia de anticuerpos contra AND en esta especie. En este estudio, mediante un modelo de regresión logística evaluamos qué características de O. longicaudatus, capturados en la Patagonia norte de Argentina, incrementan la probabilidad de un individuo de presentar anticuerpos contra AND para relacionarlos con posibles mecanismos de transmisión del virus dentro de la población. El sexo, la edad, la masa corporal y las heridas resultaron factores importantes para la circulación y persistencia del virus dentro de la población de O. longicaudatus. La probabilidad de que un O. longicaudatus, macho, adulto con heridas presente anticuerpos contra AND aumentó con el incremento de la masa corporal, siendo esta probabilidad mayor al 80% en individuos con masas corporales mayores a 44 g. Sin embargo, el posible mecanismo de transmisión de AND dentro de la población de O. longicaudatus queda aún incierto, por lo que son necesarios estudios futuros que involucren un mayor número de individuos y un tiempo prolongado de seguimiento en su proceso de seroconversión.

Rodent community structure and Andes virus infection in sylvan and peridomestic habitats in northwestern Patagonia, Argentina.

Modifications of natural habitat in peridomestic rural areas could affect original rodent community composition, diversity, and evenness. In zoonoses such as hantavirus pulmonary syndrome, the presence of a diverse community can dilute the impact of the principal reservoir, reducing risk to humans. The goal of this study was to examine rodent community composition, abundance of Andes virus (ANDV) host (Oligoryzomys longicaudatus), ANDV prevalence, and temporal variability associated with rural peridomestic settings in Patagonia, Argentina. We trapped rodents in peridomestic settings and nearby sylvan areas for 2 years. The numerically dominant species differed between peridomestic and sylvan settings. O. longicaudatus was the most abundant species in peridomestic settings (>50% of individuals). Diversity and evenness in peridomestic settings fluctuated temporally, with an abrupt decline in evenness coinciding with peaks in ANDV prevalence. The probability of finding an ANDV-positive mouse in peridomestic settings was 2.44 times greater than in sylvan habitats. Changes in rodent communities in peridomestic settings may increase the probability for human exposure to ANDV because those settings promote the presence of O. longicaudatus with high ANDV antibody prevalence. High O. longicaudatus relative abundance in an unstable community associated with peridomestic settings may favor intraspecific contact, leading to a higher probability of virus transmission.

Distribution and abundance of sigmodontine rodents in relation to hantavirus in Neuquén, Argentina.

In order to estimate spatial distribution, temporal variation, and prevalence of Andes hantavirus antibody in the rodent community, and especially in Oligoryzomys longicaudatus populations, four different ecosystems were trapped seasonally between spring 2001 and winter 2002 in Neuquen, northwestern Argentinean Patagonia. Five peridomestic settings were sampled within the same period. The rodent O. longicaudatus had the widest distribution in Neuquen, as it was the only species captured at every sample site except for the High Andean steppe, and it was also the most common species captured. Rodents of 13 species were tested for hantavirus antibody prevalence, but O. longicaudatus and Abrothrix longipilis were the only seropositive species. Seropositive individuals were captured during spring and summer in the Subantarctic forest and in winter 2001 in a peridomestic setting in the Patagonian steppe. The dominant presence of O. longicaudatus throughout Neuquen must be incorporated into strategies to prevent human exposure to hantavirus.

Whole-cell Bordetella pertussis vaccine component modulates the mouse immune response to an unrelated soluble antigen.

Several factors are involved in the selective activation of Th1 or Th2 cells, such as different physical characteristics of antigens and the type of antigen-presenting cells involved in the immune response, among others. To study the influence of a particulate antigen on Th1/Th2 cell differentiation during the immune response to another antigen, we analysed the immune response to tetanus toxoid (soluble antigen) in BALB/c mice immunized with one of the three following vaccines: tetanus and diphtheria toxoids (DT), or DT associated with whole-cell Bordetella pertussis or its soluble antigens (DTPw and DTPa, respectively). Similar total antibody levels were observed for all vaccines. DT vaccine showed a higher IgG1/IgG2a ratio than the similar values observed for DTPw and DTPa vaccines. DT- and DTPa-primed spleen cells showed a Th2 (IL-5) profile while a Th1/Th2 (IFN gamma, IL-5) profile was observed for DTPw. IL-6 was only produced by DTPw-primed cells. Besides, IL-12 levels induced by DTPw were three times higher than the ones induced by both DT and DTPa. Our findings indicate that whole-cell B. pertussis priming modifies the tetanus immune response from Th2 to Th1/Th2 type probably via inflammatory mechanisms. In addition, in the light of conflicting reports regarding the mechanisms of protection induced by DTP vaccines, we studied the pertussis immune response. Only DTPw immunization generated memory T cells capable of proliferating with B. pertussis as an in vitro stimulus. Results might indicate that these cells may not play a key role in protecting against B. pertussis when the host is vaccinated with DTPa.

[Cytokines induced by experimental anti-tetanus immunization. Vaccine formulation effect]. / Citoquinas inducidas por la inmunización experimental antitetánica. Efecto de la formulación vacunal.

Several factors are involved in the selective activation of T helper 1 or T helper 2 cells, such as the type of antigen-presenting cells involved in the immune response and the different physical characteristics of antigens. The aim of this work was to evaluate if adding other antigens to tetanus toxoid modifies the original immune response. BALB/c mice were immunized with tetanus and diphtheria toxoids associated with whole-cell Bordetella pertussis (DTPw vaccine), B. pertussis soluble antigens (DTPa vaccine) or Salmonella typhi plus DTPa (DTPaSt vaccine). DTPw and DTPaSt immunization induced a T helper 1/T helper 2 (Th1/Th2) anti-tetanus response with gamma interferon and interleukin 5 production. DTPa immunization induced a Th2 response with production of interleukin 5 and interleukin 6. Only DTPw vaccine induced higher levels of IL-12 in non-immunized mice. Our findings indicate that the co-injection of whole-cell antigens such as B. pertussis or S. typhi, modifies the anti-tetanus response shifting it from Th2 to Th1 type. However, the original Th2 immune response is not modified when the vaccine consists only of soluble antigens.

Citoquinas inducidas por la inmunización experimental antitetánica. Efecto de la formulación vacunal / [Cytokines induced by experimental anti-tetanus immunization. Vaccine formulation effect]

Several factors are involved in the selective activation of T helper 1 or T helper 2 cells, such as the type of antigen-presenting cells involved in the immune response and the different physical characteristics of antigens. The aim of this work was to evaluate if adding other antigens to tetanus toxoid modifies the original immune response. BALB/c mice were immunized with tetanus and diphtheria toxoids associated with whole-cell Bordetella pertussis (DTPw vaccine), B. pertussis soluble antigens (DTPa vaccine) or Salmonella typhi plus DTPa (DTPaSt vaccine). DTPw and DTPaSt immunization induced a T helper 1/T helper 2 (Th1/Th2) anti-tetanus response with gamma interferon and interleukin 5 production. DTPa immunization induced a Th2 response with production of interleukin 5 and interleukin 6. Only DTPw vaccine induced higher levels of IL-12 in non-immunized mice. Our findings indicate that the co-injection of whole-cell antigens such as B. pertussis or S. typhi, modifies the anti-tetanus response shifting it from Th2 to Th1 type. However, the original Th2 immune response is not modified when the vaccine consists only of soluble antigens.