Search

Monovalent, inactivated and adjuvanted vaccines against African horse sickness, prepared with serotypes 5 and 9, were tested on guinea-pigs to select the formulation that offered the greatest immunity. The final formulation of the vaccines took into account the immune response in the guinea-pig and the inflammatory properties of two types of adjuvant previously tested on target animals. A pilot study was subsequently conducted on horses using a vaccine prepared with serotype 9. The vaccine stimulated neutralising antibodies from the first administration and, after the booster dose, 28 days later; high antibody levels were recorded for at least 10 months. The guinea-pig appears to be a useful laboratory model for the evaluation of the antigenic properties of African horse sickness vaccines.

The epidemiology of hepatitis A, a disease endemic in various countries, is in a state of continuous change. Adults are more exposed to infection and considering the frequent absence of immunity, in contrast to children in whom the disease is almost always asymptomatic, the disease is often serious and prolonged with a mortality of up to 2.5%. The mode of transmission of HAV is predominantly the fecal-oral route; the virus is isolated during the prodromic period of the disease from the feces, blood, bile and seminal fluid. The virus can also be found in saliva (OMS '95); in addition it may also be transmitted by the maternal-fetal route. The HAV infects cells in vitro but does not cause a direct cytopathic effect. At the beginning of the acute phase of the disease the production of anti-HAV antibodies is of the IgM type followed later by IgG. Some studies have shown a potential role of cellular immunity in clearance of the virus from the hepatocytes and in the pathogenesis of the infection of HAV. The efficacy of immunoglobulin serum in the prevention of hepatitis A has been demonstrated since 1944. As regards active immunity two types of vaccinations have been prepared. One with live attenuated HAV carried by either bacteria or virus. The other, killed inactivated HAV, HAV capsule, antigenic subunit, synthetic peptides, anti-idiotypes or virosomes. The recent literature describe the vaccine produced by Merck Sharp & Dohme and by Smith Kline Beecham (SKB); both vaccines are made from HAV, grown in vitro, inactivated with formalin and adsorbed to aluminum hydroxide. The protection of the vaccine begins 14 days after administration and lasts from one month to one year. Numerous studies have been conducted which have shown that the vaccine is effective when given in 2 doses and confers protection against HAV for at least one year. The results have shown that the vaccination causes seroconversion in approximately 100% of subjects, and does not cause serious side effects and the acceptance of the vaccination worldwide has been good.

Hepatitis A is a worldwide disease transmitted by oral-fecal route, the endemicity level is high in developing countries and in the Far East. In northern Europe the endemicity level is low, but it is intermediate in the European Mediterranean area. Seroepidemiological surveys show that in Italy, as in many other European countries, hepatitis type A endemicity is declining. Therefore, immunity to infection shifts towards the older generations, leaving an increasing number of teenagers and young adults susceptible to the infection. Since in adults the infection is associated with higher levels of morbidity and mortality than in children, hepatitis A remains a public health problem. Moreover, travellers visiting an endemic area are at risk of acquiring the disease. Short-term, passive immunization with immune serum globulins is not a satisfactory method of controlling hepatitis A. The best way of controlling HAV endemicity is vaccination and a satisfactory vaccine will be available by 1993. Soon after HAV propagation in cell culture was achieved, three different approaches to HAV vaccine production were investigated: recombinant vaccines, live attenuated vaccines, inactivated vaccines. The production of a recombinant vaccine is, as yet, unavailable, because two HAV surface proteins linked together in a definite three dimensional configuration are needed to stimulate an effective immune response. A satisfactory live attenuated vaccine has not yet been obtained because of difficulties in maintaining a stable level of attenuation. Consequently, attention has shifted towards inactivated vaccines, and the HM 175 strain inactivated vaccine has been produced and widely studied in over 25,000 human volunteers.(ABSTRACT TRUNCATED AT 250 WORDS)

In order to contribute to the planning of antirabies oral vaccination of foxes a series of ethological and ecological investigations have been carried out. The results obtained are briefly summarized and discussed together with experimental data on antirabies immunization of dogs and foxes with different vaccines.

The appearance and the progression of the specific immunoreactions at biliary levels (agglutinant titre, immunoenzimatic titration of IgAGM, IgA, IgG) in rabbits treated per os from 1 to 10 times, daily or bi-weekly, with 20 and 40 milliard of inactivated bacterial antigens (E. coli, Proteus vulgaris, Staph. aureus, Str. faecalis) have been studied. The appearance of the specific biliary antibodies has been very precocious (only one day after the first administration) and the values increased progressively with the number of administrations. The posology of 40 milliard and the bi-weekly sequence of the treatments presented the highest immunoreactions. In the bile the IgA and IgG increased considerably, but the IgA have been preponderant; in the serum only the IgG presented a remarkable increase, not the IgA, that are present in very small quantity.