Hepatitis A virus infections in Voyvodina.

Sera of 1000 persons in Voyvodina were tested with radioimmunoassay for antibodies against hepatitis A virus (HAV). The morbidity and age incidence of positive findings have been analysed and compared with relevant findings in other countries. Below the age of 19 years the morbidity rates are higher (0.138 to 0.595 per mill) and the prevalences of seropositives are lower (17.1-64.0%) than the respective frequencies above that age (0.011 to 0.052 per mill and 85.7-98.7% respectively). Below the first year of life seropositivity is more frequent than in 1- to 14-year old children. After the first year until the age of 30-39 years the frequency of seropositives increases with increasing age up to a maximum of about 90%.

Haemagglutination-inhibiting (HI) antibodies against four prototype strains of influenza A virus in different age groups.

Sera of 197 apparently well persons were tested for residual haemagglutination-inhibiting antibodies against live Hong Kong/68, A/FM/47 and A/PR/34 strains. Sera of 62 well persons, regularly exposed to contacts with swine, were tested against an inactivated A/New Jersey/76 antigen. Those born some time before and during a certain influenza era showed a significantly greater proportion of homologous residual titres against the subtype prevailing in that influenza era, than those born after the termination of the same era. In each of the seven age groups tested both the percentage of positives and the geometric mean titres were usually highest against the Hong Kong strain (representing the most recent era); the next highest were those against the FM1 strain and the lowest were those against the PR8 strain (representing the most distant of these three influenza eras). The serological involvement of donors exposed to regular contacts with swine was relatively stronger against the New Jersey antigen than the response of other serum donors shown against the other three, more recent, prototypes of influenza virus A. The oldest age groups showed significantly lower antibody response against the PR8, FM1 and Hong Kong strains (but not against the New Jersey antigen) than the next one or two of the younger age groups.

Detection of "alpha-type" inhibitors in the presence of low levels of specific influenza antibodies.

In native, heated or otherwise treated egg white and in sera of men and guinea pigs, haemagglutination inhibition titres were determined against three inhibitor-sensitive (IS) strains and one inhibitor-resistant (IR) variant on influenza A virus. A few human sera with no detectable antibody revealed high inhibition titres even against the IR variant. Human sera after treatment with trypsin and periodate revealed mostly a reduction or no change, and exceptionally an increase of their inhibition titre. The extent of these changes varied with different influenza virus strains and showed a positive correlation with the inhibitor content and no correlation with the antibody levels of the sera. The so-called "nonspecific" thermostable inhibitors possess a certain degree of specificity for different influenza virus strains.

Age-specific incidence of neutralization antibodies of Herpes simplex virus.

Sera of 1255 individuals from Novi Sad, varying in age from less than 1 month to 69 years, have been tested for neutralization antibodies to Herpes implex virus type 1. The eight newborns tested and 97% of the 507 adults were positive, with titres ranging from 1/4 to 1/256. The titres in newborns were significantly lower than the titres in adults. After birth the maternal antibodies declined rapidly and 94% of infants at the age of greater than 6 months and less than 2 years were negative. After the first year infants in Novi Sad start to acquire herpes-neutralizing antibodies actively, reaching a 50% incidence of positives between the 2nd and 3rd year of age. Age-specific incidence rates of herpes positives found in Novi Sad have been compared with those reported from Edinburgh, Freiburg i. Br. and Louisiana. Possible influences of several circumstances upon the incidence rate of positives detected by the neutralization test are discussed.

Serological studies of Australia-antigenaemia in different categories of sick and healthy persons.

Sera (1,333) were collected from patients at various days after the onset of manifest B-virus hepatitis; from long term asymptomatic carriers of Au-antigen, with or without a demonstrable history of hepatitis; and from apparently healthy Au-negative persons. Au-anti-genaemia was tested with gel-diffusion (GD), counter immunoelectrophoresis (CIE), reversed haemagglutination (RHA) and complement fixation (CF). The CF test was found to be as sensitive as the RHA test, about 10 times more sensitive than the CIE, and about 25 times more sensitive than the GD test. With greater amounts of antibodies used in CF tests, the titres of AU-antigen were higher and the heights of prozones were lower. It is stressed that in screening for Au-antigen, sera should be tested in dilutions from 2 to 64, against 4 to 8 CF units of antibody. The frequency of asymptomatic long term Au-carriers, in the group with a known history of hepatitis, amounted to 41%, and themean titre of Au-antigen was 1:392. In the group of long-term carriers with no detectable history of hepatitis, the rate of Au-carriers was 1.6%, and the mean titre was 1:19.

A virological study of post-vaccinal encephalitis.

In the province of Voyvodina 18 cases of post-vaccinal encephalitis have been recorded, three of which were fatal.The estimated morbidity rate was 0.6 per 10(5) after revaccination, and 3.9 per 10(5) after primary vaccination. The virological studies described, as well as other findings referred to in this report, are consistent with the possibility of an autoimmune aetiology of the post-vaccinal encephalitis cases observed.

Skin reactivity and antibody response following vaccination against smallpox.

Revaccination between 2 and 5 years after the last vaccination induced higher complement-fixation titres than revaccination 7-63 years after the last vaccination. The highest CF titres were reached during the 3rd to the 5th week after vaccination.Fifty-two serum samples, taken 137 or more days after a successful vaccination, all showed CF titres lower than 1/2.In a group of successfully vaccinated persons with no post-vaccinal complications, 65 out of 66 had a successful ;take' after one or two subsequent vaccinations.Sera of persons receiving primary vaccination showed significantly lower CF titres than sera of revaccinated persons. Cases of post-vaccinal encephalitis showed greater antibody response than uncomplicated successfully vaccinated cases in both the primary vaccination and revaccination groups. The antibody response in revaccinated persons with post-vaccinal encephalitis was greater than that in the group of successfully revaccinated cases without encephalitis.A group of 26 naturally hyporeactive persons completely failed to ;take' even after vaccination repeated between 3 and 10 times (average 5 times per person). The frequency of seropositives in this group, and the height of their CF titres, were significantly lower than in the group of successfully vaccinated persons. These findings support the view that untreated persons who repeatedly fail to ;take' with the vaccine must not be considered immune.In vaccinated persons treated with immunoglobulin (with or without simultaneous treatment with Marboran) antibody production was apparently diminished. Treatment of patients with Marboran significantly lowers the capacity of the vaccine to ;take'.