A sensitive enzyme-linked immunosorbent assay for the detection of herpes simplex virus antigens

A sandwich ELISA for the detection of herpes simplex virus (HSV) antigens was developed using sheep anti-HSV F(ab')2 fragments for capture and an indirect antibody system for detection. Current detection limits are 0.5 ng protein for HSV1 and 1.5 ng protein for HSV2. This compares to a single HSV1-infected Vero-cell in a background of 10(6) non-infected cells or 10 plaque forming units (PFU) of HSV1 in culture supernatants as determined in separate experiments. Limiting dilution experiments show that one PFU of HSV1 can be detected after overnight culture in both supernatant and cell extracts. The use of F(ab')2 for capture completely eliminated binding of Staphylococcus aureus. No cross-reactivity was observed with other human herpes viruses. When evaluated with 245 random 'left-overs' of genital swab specimens in transport medium the test showed a sensitivity and specificity of 77.2 and 97.8%, respectively, with respect to virus isolation in culture. In a preliminary study on 16 direct ELISA swab-specimens extracted in 0.5 ml ELISA sample buffer both sensitivity and specificity were 100% with respect to culture. In both clinical series there was a proportional relationship between the ELISA value and the estimated amount of infectious virus in the specimen.

Influence of special surveillance programmes and AIDS on declining incidence of syphilis in Amsterdam

In 1976-8 the incidence of syphilis in Amsterdam doubled from 41 to 88 per 100,000. Contact tracers identified two major risk groups, homosexual men with multiple partners and prostitutes using drugs, and special surveillance programmes for these groups have been organised on a regular basis since 1979. As a result of these two programmes the incidence of syphilis started to decline appreciably in 1981-3. From 1984 onwards a further decline occurred in men as a result of a change of lifestyle by homosexual men, probably because of the appearance of AIDS. In 1985 the incidence of syphilis in Amsterdam had dropped to 30 per 100,000, the lowest level since notification started.

Risk factors and prevalence of HIV antibodies in homosexual men in the Netherlands

As part of the prospective AIDS study in Amsterdam, blood samples were collected from 741 healthy homosexual men with multiple sexual partners, between October 1984 and May 1985. Samples were analyzed for the presence of antibodies to the human immunodeficiency virus (anti-HIV). Anti-HIV was demonstrated in 233 (31%) of the respondents. Seropositive respondents engaged in anal receptive sexual techniques with more sexual partners than did seronegative respondents, whereas seronegatives engaged in manual sexual techniques with more sexual partners than did seropositives. As far as it was possible to control for the interrelations between the measured variables, a direct relation with anti-HIV was established. This leads to the conclusion that when the number of sexual partners is considered a risk factor for HIV, a clear distinction should be made between the sexual techniques practiced with these partners. Two other risk factors for the presence of anti-HIV were the use of cannabis and of nitrite.

Viral gene expression, antibody production and immune complex formation in human immunodeficiency virus infection

Human immunodeficiency virus (HIV) antigen (HIV-Ag) in polyethylene glycol (PEG) precipitates and supernatants and HIV antibodies (HIV-Ab) to core and envelope antigens were studied in serial serum samples of three HIV-Ab seroconverters and 11 HIV-Ab seropositive men with a mean follow-up time of 16.1 months. In five men not progressing beyond persistent generalized lymphadenopathy (PGL) and two progressing to AIDS, HIV-Ag was detected once in 'free' configuration before HIV-Ab seroconversion and persistently or intermittently 'complexed' thereafter; in six of these men HIV core antibodies were continuously present with a declining level in one. In two men not progressing beyond PGL and five progressing to AIDS HIV-Ag was detected 'complexed' before HIV-Ab seroconversion once and persisted predominantly in 'free' configuration thereafter, while no HIV core antibody was detected in six of these men and a declining level in one. HIV-Ag was detected in 37% (14 out of 38) of HIV core antibody seropositive samples, mostly in 'complexed' form, while HIV-Ag was detected in 86% (43 out of 50) of HIV core antibody seronegative samples, mostly in both 'complexed' and 'free' configuration. Antibodies to HIV envelope antigen were detected in all HIV-Ab seropositive samples. These results indicate that the level of HIV-Ag expression is the primary determinant of detectability of HIV core antigens as well as antibodies. Enhancement of HIV-Ag expression, in a significant number of cases associated with clinical deterioration, appears to lead to clearance of HIV core antibodies in immune complexes, while HIV envelope antibody levels remain relatively unaffected.

Persistent HIV antigenaemia and decline of HIV core antibodies associated with transition to AIDS

Sequential serum samples from 13 homosexual men who seroconverted for antibodies to human immunodeficiency virus (HIV) were tested for HIV antigen. In one of these men, who developed the acquired immune deficiency syndrome (AIDS), HIV antigenaemia preceded the onset of AIDS by more than a year and persisted throughout the course of the disease. This antigenaemia was accompanied by the disappearance of IgG antibody reactivity to the major HIV core protein p24. In none of the 12 others, who all remained without serious disease, were serum concentrations of HIV antigen detected, except on one occasion in one man. All their serum samples showed strong IgG antibody reactivity to p24. Nine children who were infected with HIV in 1981 by plasma transfusion from a single donor were also followed up for HIV antigenaemia. HIV antigen was almost constantly present in the serum (26 of 28 samples) of five children who developed AIDS related complex or AIDS and less often in the serum (four of 10 samples) of four children who remained free of symptoms. The two children who developed AIDS showed a virtual absence of antibody reactivity to p24. These results indicate that increased HIV gene expression is a contributing factor to the development of AIDS and also provide evidence for a switch from latent to active HIV infection.

Introduction of lymphadenopathy associated virus or human T lymphotropic virus (LAV/HTLV-III) into the male homosexual community in Amsterdam

To establish when lymphadenopathy associated virus or human T lymphotropic virus (LAV/HTLV-III) was introduced into the Netherlands, we studied a cohort of homosexual men who participated in a hepatitis B vaccine efficacy study between 1980 and 1982. On entry into the study (November 1980 to December 1981) five (0.7%) out of 685 participants were found to have antibodies to LAV/HTLV-III, and during follow up 15 seroconversions were detected among the 680 who had been seronegative initially (end point attack rate 3%). LAV/HTLV-III was not transmitted by the heat inactivated hepatitis B virus (HBV) vaccine used. Anal sexual contact and antibodies to cytomegalovirus (CMV) were found to correlate with seropositivity or seroconversion for LAV/HTLV-III. Six out of 15 men who seroconverted reported a mononucleosis like illness, but three of them had other concurrent virus infections. To date, only one of the 20 seropositive men has developed the acquired immune deficiency syndrome (AIDS), three years after his seroconversion. This study shows that the introduction of LAV/HTLV-III into the Dutch male homosexual community took place at the end of the 1970s, a few years before the first case of AIDS in a native Dutchman.

Distinct IgG recognition patterns during progression of subclinical and clinical infection with lymphadenopathy associated virus/human T lymphotropic virus

Longitudinal IgG recognition patterns of viral proteins were studied in 15 men who had seroconverted for lymphadenopathy associated virus/human T lymphotropic virus (LAV/HTLV-III). Antibodies to the major viral core protein p24, which is a cleavage product of the gag gene encoded precursor protein pr55, appeared first. These were soon followed by antibodies to pr55 and more gradually by antibodies to the other gag gene encoded cleavage product p18, the env gene encoded transmembrane glycoprotein gp41, the env gene encoded glycoproteins gp65 and gp110, and the putative pol gene product p33. In 13 subjects who remained healthy the reactivity to the different proteins increased or stabilised with time, while in two men who developed acquired immune deficiency syndrome (AIDS) the reactivity, most noticeably to gag encoded proteins, diminished before or at the onset of symptoms.

Hepatitis B vaccination

As hepatitis B virus does not replicate in tissue culture systems, it was impossible to prepare a vaccine in the conventional way. However, the surface-antigen of the virus is present in abundance in the blood of certain virus carriers. This phenomenon has been used to develop plasma-derived hepatitis B vaccines and these vaccines are now available. In low incidence countries vaccination should be restricted to high-risk groups after initial screening for antibodies to hepatitis B virus. In areas where hepatitis B virus infection is highly endemic immunisation of the whole population, immediately after birth, is probably the most effective strategy. The high cost of the currently available plasma-derived vaccine is a constraint on the implementation of public health programmes for the prevention of hepatitis B. A second generation of vaccines - made by DNA recombinant technology - is expected to be available in the near future and could be the answer to these problems.

Infection with cytomegalovirus in homosexual men

The prevalence and incidence of cytomegalovirus (CMV) infections were studied in a group of homosexual men. Of the 710 participants, 501 (70.6%) had complement fixing antibodies to CMV on entry to the study. During the follow up (maximum 23 months) 69 CMV infections were found: 50 primary infections among the 209 seronegative men (attack rate 27.3%), and 19 recurrent infections among the 501 seropositive men (attack rate 6.2%). The prevalence of antibody to CMV was correlated with four characteristics of the participants' lifestyles: duration of homosexual activity, number of different sexual partners, history of syphilis, and anal sexual contact. Among the seronegative men, the incidence of primary infection with CMV correlated with a history of syphilis and anal sexual contact. We conclude that infections with CMV are highly prevalent among homosexual men, and that anal sexual contact plays an important part in the transmission of this virus.

Epidemiology of PPNG infections in Amsterdam: analysis by auxanographic typing and plasmid characterisation

In January 1981 the incidence of penicillinase producing Neisseria gonorrhoeae (PPNG) strains in Amsterdam had increased to 18% of all new cases of gonorrhoea. Auxanographic typing in combination with plasmid determination of 729 PPNG strains showed that in 1981 the predominant and endemic types were those with the Africa plasmid and transfer factor which were non-requiring and inhibited by phenylalanine. In 1982 proline requiring strains with the Asia plasmid and transfer factor increased after being imported and spread by prostitution. Four different plasmid patterns and 12 auxotypes were distinguishable. Unusual auxotypes of both African and Asian plasmid types are frequently imported, some disappearing soon after their introduction into Holland but others providing an opportunity to trace sources and contacts. Prostitution and the biological properties of PPNG strains seem to play an important role in their spread. Only 2.6% of them were isolated from homosexual men. In areas where PPNG strains are prevalent, auxotyping is an important tool in their surveillance.

Prevalence of HTLV-specific antibodies in Surinam emigrants to The Netherlands

Sera of 98 participants in a methadone maintenance programme, all recent Surinam emigrants to the Netherlands, were examined for antibodies to disrupted HTLV using the ELISA technique. Twelve per cent of the donors possessed HTLV-specific antibodies with a range of titre from 41 to 20,000. Sera of 26 control Dutch drug users lacked such antibodies with the exception of one female who subsequently was found to reside with a Surinam male. Intravenous drug use was not a factor in these studies. These data indicate that HTLV circulates within the Surinam community in the Netherlands. More broadly, these results show that the region of the Caribbean endemic for HTLV extends as far south as Surinam. Furthermore, an antibody prevalence of 12% for clinically healthy donors with non-malignant disease suggests that the Caribbean has an incidence of HTLV infection approaching, if not equal to, that of southwestern Japan.

Prevalence and incidence of hepatitis A among male homosexuals

In a study of 689 male homosexuals 290 (42%) were found to have antibodies to hepatitis A virus. The 399 men who did not have antibodies were followed up for up to 690 days, and 35 cases of hepatitis A were detected. The attack rate at the end of the study was 14%. The incidence climbed steadily, indicating that the cases of hepatitis A did not occur in clusters. Statistical analysis showed that the prevalence of antibodies to hepatitis A virus was significantly correlated with the duration of homosexual activity (p less than 0.006), and this was independent of age. The incidence of hepatitis A was found to be correlated with the number of different sexual partners in the preceding six months. It is concluded that hepatitis A is a sexually transmitted disease among homosexual men in countries with a low rate of exposure to hepatitis A during childhood.