Marlon Vicente da Silva

Immune response in cattle vaccinated against rabies

In order to determine the best type of rabies vaccine to use as a booster, 78 serological samples from singly vaccinated cattle were analyzed by counterimmunoelectrophoresis technique. The animals were divided into several groups, received the first vaccine dose with modified live virus vaccine (ERA strain) and were revaccinated with inactivated virus or modified live virus vaccines. Boosters were given at 2, 4, 8, 12 and 16 weeks following first vaccination. Results showed high titres in the cases of booster with inactivated vaccine. In all cases, however, detectable antibody titres declined quickly.

Vírus rábico em morcego Nyctinomops laticaudatus na Cidade do Rio de Janeiro, RJ: isolamento, titulação e epidemiologia

The first case report of rabies in bats of the species Nyctinomops laticaudatus, in the city of Rio de Janeiro City, is presented. Virus isolation and titration were performed in different tissues, and high titers were found in the brain and salivary glands. Rabies occurrence in such an infrequent species in this state suggests that the disease may be more prevalent than it appears to be.

An inactivated yellow fever 17DD vaccine cultivated in Vero cell cultures

Yellow fever is an acute infectious disease caused by prototype virus of the genus Flavivirus. It is endemic in Africa and South America where it represents a serious public health problem causing epidemics of hemorrhagic fever with mortality rates ranging from 20% to 50%. There is no available antiviral therapy and vaccination is the primary method of disease control. Although the attenuated vaccines for yellow fever show safety and efficacy it became necessary to develop a new yellow fever vaccine due to the occurrence of rare serious adverse events, which include visceral and neurotropic diseases. The new inactivated vaccine should be safer and effective as the existing attenuated one. In the present study, the immunogenicity of an inactivated 17DD vaccine in C57BL/6 mice was evaluated. The yellow fever virus was produced by cultivation of Vero cells in bioreactors, inactivated with β-propiolactone, and adsorbed to aluminum hydroxide (alum). Mice were inoculated with inactivated 17DD vaccine containing alum adjuvant and followed by intracerebral challenge with 17DD virus. The results showed that animals receiving 3 doses of the inactivated vaccine (2 μg/dose) with alum adjuvant had neutralizing antibody titers above the cut-off of PRNT50 (Plaque Reduction Neutralization Test). In addition, animals immunized with inactivated vaccine showed survival rate of 100% after the challenge as well as animals immunized with commercial attenuated 17DD vaccine.

Development of a membrane adsorber based capture step for the purification of yellow fever virus.

Yellow fever (YF) is an endemic disease in some tropical areas of South America and Africa that presents lethality rate between 20 and 50%. There is no specific treatment and to control this disease a highly effective live-attenuated egg based vaccine is widely used for travelers and residents of areas where YF is endemic. However, recent reports of rare, sometimes fatal, adverse events post-vaccination have raised concerns. In order to increase safety records, alternative strategies should be considered, such as developing a new inactivated vaccine using a cell culture based technology, capable of meeting the demands in cases of epidemic. With this goal, the production of YF virus in Vero cells grown on microcarriers and its subsequent purification by chromatographic techniques was studied. In this work we investigate the capture step of the purification process of the YF virus. At first, virus stability was studied over a wide pH range, showing best results for the alkaline region. Considering this result and the pI of the envelope protein previously determined in silico, a strong anion exchanger was considered most suitable. Due to the easy scalability, simplicity to handle, absence of diffusional limitations and suitability for virus handling of membrane adsorbers, a Q membrane was evaluated. The amount of antigen adsorbed onto the membrane was investigated within the pH range for virus stability, and the best pH for virus adsorption was considered to be 8.5. Finally, studies on gradient and step elution allowed to determine the most adequate salt concentration for washing (0.15M) and virus elution (0.30 M). Under these operating conditions, it was shown that this capture step is quite efficient, showing high product recovery (93.2±30.3%) and efficient DNA clearance (0.9±0.3 ng/dose).

Increasing Vero viable cell densities for yellow fever virus production in stirred-tank bioreactors using serum-free medium.

In this work, changes in Vero cell cultivation methods have been employed in order to improve cell growth conditions to obtain higher viable cell densities and to increase viral titers. The propagation of the 17DD yellow fever virus (YFV) in Vero cells grown on Cytodex I microcarriers was evaluated in 3-L bioreactor vessels. Prior to the current changes, Vero cells were repeatedly displaying insufficient microcarrier colonization. A modified cultivation process with four changes has resulted in higher cell densities and higher virus titers than previously observed for 17DD YFV.

Demonstration of Viral Antibodies by the Counterimmunoelectrophoresis Test

Neutralization tests are one of the most commonly used methods for quantifying antibodies against rabies virus (RABV). A Counterimmunoelectrophoresis Test (CIET) is another in vitro technique for titrating RABV antibodies. It is performed on an agarose slide gel and based on the reaction between antibodies present in serial dilutions of serum with RABV antigens. Binding is shown by the presence of precipitation lines that result from the migration of unbound viral antigens towards the specific antibodies present in a hyper-immune indicator serum (IS) under constant electrical current. The technique requires the production and standardization of antigen and IS, as well as the preparation of agarose slide gels, and specific chambers for electrophoresis. CIET has the ability to determine the potency of tested sera, providing results that correlate well with other techniques.

COMPARAÇÃO ENTRE CONJUGADOS IN HOUSE E COMERCIAIS PELA TÉCNICA DE RÁPIDA INIBIÇÃO DE FOCOS FLUORESCENTES (RFFIT) NA AVALIAÇÃO DE ANTICORPOS ANTIRRÁBICOS

Rabies is a lethal zoonosis that may be transmitted to man through virus inoculation, mainly by the bite of infected animals. In 2005, the Brazilian Ministry of Health spent about R

Isolamento de Cryptococcus neoformans, C. gattii e C. laurentii de sistema nervoso central de cães na cidade do Rio de Janeiro, RJ, Brasil*

66 millions in epidemiological surveillance actions, in order to carry out vaccination campaigns and acquisition of immunobiologicals. The serological evaluation is the basic requirement for surveillance of individuals vaccinated. Ninety one sera, from 34 vaccinees, were selected to evaluate the antibody titration by rapid fluorescent focus inhibition test adapted to 96-well microplates, to compare an in house produced conjugate and a commercial one. Seventy four sera (82.2%) had titers of ?0.5 IU/mL and 12 sera (13.3%) had titers of <0.5 IU/mL. Theses results showed that the rapid fluorescent focus inhibition test using the in house conjugate was as sensitive as the commercial one. The difference between the results using both conjugates was not significant; the antibody titers were highly correlated (r= 0.94).