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Unlinked anonymous screening was optimized and used for a survey of HIV prevalence in Finland. In 1993, 66,170 serum samples, covering more than 99% of pregnant women in the country were tested in pools of 5 sera. The pools tested were coded but it was possible to trace the region from where the samples had been collected. A total of 5 positive samples were found corresponding to a prevalence of 1/13,000 (0.01%) which is in accordance with prevalence estimates from earlier serosurveys and the national HIV registry. Information from voluntary regional HIV-testing programmes for pregnant women indicated that probably at least 3 of these positive cases had been identified by voluntary testing. Nine commercial EIAs were evaluated to investigate the effect of pooling on sensitivity and specificity of anti-HIV detection. Only 3 EIAs detected all pools with known positive samples. Individual sera from repeatedly positive pools were tested using the same EIA and positive results were confirmed by Western blot. This algorithm saved more than 80% of the cost compared to the conventional test algorithm used in diagnostic laboratories. The savings were mainly due to the reduced number of primary and supplemental tests.

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Endoproteolytic processing of human immunodeficiency virus type 1 (HIV-1) gp160 membrane glycoprotein precursor into gp 120 and gp41 is necessary for formation of infectious HIV particles [1]. We have studied the intracellular site of this processing using inhibition of transport at reduced temperature (20 degrees C). That reduced temperature (20 degrees C) inhibits the intracellular transport also in Jurkat-tat cells was demonstrated using the Semliki Forest virus p62 precursor processing as model. In HIV-1 infected Jurkat-tat cells the proteolytic processing of gp 160 precursor did not occur when the protein was accumulated in the TGN at 20 degrees C temperature. When the temperature was shifted to 37 degrees C the HIV-1 gp 160, which had accumulated in the TGN at the reduced temperature, was proteolytically processed. The processing of gp 160 was inhibited when the temperature reversion was carried out in the presence of brefeldin A (BFA) or aluminium fluoride (ALFn) indicating that the exit from the TGN is required for the proteolytic cleavage of HIV-1 gp160 precursor. The results suggest that the processing of gp 160 takes place at a yet unidentified transport step which is distal to the TGN/20 degrees C block site.

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Viruses of different geographical origin are circulating in Finland. We wanted to test whether phylogenetic analysis of patient lymphocyte proviral quasispecies sequences could be used to group different strains into genetic lineages. The gag p7/p9 coding region was analyzed using solid-phase direct sequencing from 30 patients in Finland and Estonia. Proviral sequences were found to represent at least four, possibly even five, different, highly diverged major lineages. Different methods of phylogenetic analysis resulted in the same conclusion. Serial samples from the same patients, taken over a period of several years showed limited variation over time. Cases of potential patient-to-patient transmission or common source of infection were identified based on the sequence analysis. Compared to similar analyses of longer genome segments, the gag p7/p9 nucleic acid binding protein coding region produces analogous results in phylogenetic analysis. The method can be used as a rapid way of determining the genetic subtype of HIV-1 strains circulating in populations.

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In order to cooperate with voluntary screening programs aimed at the surveillance of the HIV epidemic in Finland, we have studied medicolegal autopsies for HIV antibodies since 1986 using an enzyme immunoassay on postmortem sera. The investigation covered 47.4% and 39.2%, respectively, of all deaths under the age of 65 years in the metropolitan areas of Helsinki and Turku--two cities on the densely populated southern coast of Finland from which most HIV infections have thus far been detected. Nine HIV-positive cases (0.12%) were detected among the 7305 medicolegal autopsies tested in 1986 to 1990. This figure is higher than the prevalence of 0.01 to 0.03% in voluntary screening programs for the general population would suggest. Seven of our cases had previously tested positive, and two were previously unknown cases, indicating that people at high risk are clustered in the medicolegal autopsy series. Of the six cases in an early stage of infection, three committed suicide suggesting the importance of HIV-screening in suicide cases in tracing symptomless HIV carriers. Five of the cases were detected in 1990, a year when the number of new HIV infections had more than doubled compared to the previous two years. This suggests that testing of medicolegal autopsies as surrogate tests for the population gives useful information even in low-prevalence areas like Finland. Such testing has none of the ethical problems of many other back-up surveys, and may be particularly sensitive to early changes in epidemiology.

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Serum viral antibody titers against 21 viruses were studied in 19 of 23 same-sex twin pairs with multiple sclerosis derived from the Finnish Twin Cohort. Thorough neurologic examinations showed two monozygotic pairs to be concordant, whereas all dizygotic pairs were discordant. Special attention was given to measles, mumps, and rubella viruses, against which the antibody levels were determined with the complement fixation, hemagglutination inhibition, hemolysis-ingel, and enzyme immunoassay methods. Epstein-Barr virus antibody levels were determined by enzyme assay. In pairwise comparisons, the measles, mumps, and Epstein-Barr virus-IgG antibody levels were more often elevated in the patients with multiple sclerosis, compared with the healthy co-twins. The same antibody levels were more often above the median in the diseased twin, compared with the healthy twin, but the difference was not significant. No human T-cell lymphotropic virus type I antibodies were found in any of the individuals examined. The total IgG, IgA, and IgM levels did not differ between the diseased and healthy subjects. The HLA types, severity of the disease, and cell-mediated immunity parameters did not influence antibody levels.

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5,287 serum samples from 2 different sources in Finland, people possibly at risk and healthy blood donors, were tested for the presence of HTLV-I antibodies. No positive cases were found. The result suggests that this virus is not endemic in Finland. 10 cases gave repeatedly a low positive value in the enzyme immune assay (EIA) test but were confirmed negative with other tests that included western blot, passive agglutination and immunofluorescence. Four of these samples originated from healthy blood donors, 6 from other categories. Several of them showed restricted reactivity in western blots. Five HIV-positive sera, discovered during the study from people with possible risk factors, were also tested for HTLV-I but showed no reactivity.

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During a thorough surveillance of viral infections of the central nervous system an outbreak of aseptic meningitis was discovered in the western part of Finland in late 1985. The 21 diseased young adults were carefully studied by different virological methods. A presumed viral etiology, in all cases of enteroviral origin, was found in 16 of 20 (80%) with adequate specimens. Four different enteroviruses were associated with this episode; in 9 cases the presumed etiological agent was echovirus 5, while coxsackie B5, echo 25 and echo 17 viruses appeared to be responsible for 4, 2 and 1 case, respectively. Sensitivity of different diagnostic methods as regards detection of the echovirus 5 infections was in order: increase of type-specific neutralizing serum antibodies, isolation of virus from faeces, isolation from throat and group diagnosis by demonstrating an increase in complement-fixing antibodies to coxsackie B5 virus antigen.

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IgA-deficient blood donors and their age- and sex-matched controls were compared for the occurrence of complement-fixing antibodies in serum against several viruses. The level in the IgA-deficient persons was slightly higher against several respiratory pathogens (adenoviruses, type B influenza virus, parainfluenza virus, and respiratory syncytial virus) that give rise to localized infections, and against coxsackie B group of viruses. No corresponding difference was observed in mumps, varicella, and cytomegalovirus infections, where viraemia is a characteristic feature, or in Mycoplasma pneumoniae infection.

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