An investigation of the occurrence of SV40 antibodies in South Africa.

We developed an enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to simian virus 40 (SV40) in human serum. We then used the ELISA to test for anti-SV40 antibodies in healthy individuals and patients suffering from cancer and renal diseases. The aim of the study was to determine the presence of antibodies against SV40 in sera of individuals who received the South African poliovirus vaccines from 1958 to the present. Detecting such antibodies could give an indication of whether any of the poliovirus vaccines used in South Africa were ever contaminated with the SV40 or not. A total of 5/164 samples were repeatedly positive for SV40 antibodies by the ELISA. Four of the samples were from the healthy population group and the remaining 1 (1/64) was from the patient group. An SV40 antibody-blocking assay and a Western blot were used as additional confirmation for the SV40 antibodies, whereas the Western blot assay developed a single common band on all 5 samples.

Lack of susceptibility of Chacma baboons (Papio ursinus orientalis) to hepatitis C virus infection.

The main reason to ascertain whether baboons are susceptible to infection with hepatitis C virus (HCV) is the need to replace chimpanzees, which are endangered, as an animal model for undertaking research into the biology and host-virus interactions of HCV, and for developing a vaccine against this virus. A second reason is that baboons are a possible source of xenografts for human liver transplantation. We inoculated serum containing HCV into four Chacma baboons and monitored them for 52 weeks for evidence of infection. Serum was tested for antibody to HCV, HCV RNA, and aminotransferase concentrations at 2-week intervals for 26 weeks and thereafter at 4-week intervals. Liver tissue was examined at 28 and 52 weeks for histopathological changes and viral RNA, and at 52 weeks for viral particles using electron microscopy. Reverse transcription-polymerase chain reaction assay was used to detect HCV RNA, and the results were confirmed by Southern hybridization. Serum aminotransferase concentrations remained within the normal range and liver histology was normal during the follow-up period. Passive transmission of anti-HCV to the baboons was observed during the first 4 weeks. HCV RNA was not detectable in any serum or liver sample and electron microscopy failed to reveal viral particles in liver tissue. In conclusion, we did not find Chacma baboons to be susceptible to infection with HCV, although we cannot deny that in an immunosuppressed liver transplant recipient, infection of a baboon xenograft might occur. Another animal model for HCV infection must be sought.

Susceptibility of chacma baboons (Papio ursinus orientalis) to infection by hepatitis B virus.

BACKGROUND: Because baboons are being considered as a source of xenografts for human liver transplantation in patients with hepatitis B virus- (HBV) induced cirrhosis to forestall infection of the graft by the virus, we undertook a study to ascertain if baboons are resistant to HBV infection. METHODS: Six chacma baboons were inoculated with serum containing HBV and were followed for 52 weeks to detect transmission of infection. RESULTS: Anti-HBc was detected in the serum of four baboons 16 weeks after inoculation. Virions, small spherical particles, and tubular forms were seen at this time in the serum of the one baboon studied by transmission electron microscopy. HBV DNA was detected by polymerase chain reaction in the serum of the same four baboons throughout the period of follow-up, as well as in liver tissue obtained after 52 weeks. The specificity of the DNA was confirmed by Southern hybridization. Nucleotide sequences showed complete sequence identity between the HBV DNA in each of the baboon sera and one of the two HBV genotypes inoculated. Serum transaminase levels tested at 4-weekly intervals were always normal and histological examination of liver tissue after 52 weeks showed no evidence of chronic hepatitis. Examination of squash preparations of liver tissue by electron microscopy in one baboon revealed core-like particles. CONCLUSIONS: Chacma baboons are susceptible to HBV infection and appear to develop a chronic carrier state. The use of xenografts from baboons should preferably be avoided, but if they are used again for HBV-infected patients it would be prudent to treat the patients as if they had received an organ from a human donor.

Characterisation of gastro-enteritis-associated adenoviruses in South Africa.

OBJECTIVE: To analyse adenovirus (Ad) numbers and types associated with paediatric gastro-enteritis in South Africa. SETTING: Gauteng, 1994-1996. METHODS: A total of 234 paediatric diarrhoeal stool samples were screened for Ad using commercial enzyme-linked immunosorbent assays (ELISAs). Adenoviral isolates were typed, where possible, using restriction enzyme analysis. RESULTS: Ad was detected in 23 (9.8%) specimens, of which 8 (34.8%) were found by subgroup F-specific ELISA to contain Ad40 or 41. Six of these isolates were typed and 2 could not be typed. Of the remaining 15 specimens, 2 isolates had restriction profiles that did not correspond with known Ads, while 2 were identified as Ad31 and 1 as a subgroup C Ad. The remaining 10 specimens negative for Ad40/41 were non-cultivable and could not be typed. CONCLUSIONS: The high percentage of non-cultivable Ads other than Ad40/41 is unusual, and may possibly indicate the prevalence of hexon variants of Ad40/41 or of emerging Ad types in South Africa.

Transmission electron microscopy on simian immunodeficiency virus-infected cocultures of vervet monkeys.

Healthy African green monkeys are the natural reservoirs for certain HIV-related SIVs. More research is now focused on these nonhuman primates that are asymptomatic, so as to answer questions of origins, pathogenesis and therapy with respect to HIV in man. The present study involves the isolation and subsequent co-cultivation of SIV variants from two healthy vervet monkeys (Cercopithecus aethiops pygerythrus). Western Blots (New LAV Blot 1 and New LAV Blot 2, Pasteur) revealed sero cross-reactivity of each monkey to major HIV-1 and HIV-2 antigens. Freshly isolated peripheral blood mononuclear cells of each monkey were co-cultivated with the CEMss and M4C8 T-cell lines. The cocultures were incubated in CO2 at 37 degrees C for 3-4 days, before refeeding with RPMI 1640, phytohaaemagglutinin and interleukin-2. Cytopathic effects in the cocultures were observed 14 days post-infection, with syncytia and enlarged, granular cells being predominant in both of the cell-lines used. The presence and morphology of viral-like particles were observed by transmission electron microscopy. Immunocytochemistry and in situ hybridization may help in characterization of the particles, as well as aid in determining localization and concentration in vitro.

Serologic markers for hepatitis B virus and hepatitis A virus in Bushmen in West Caprivi, Namibia.

A community based sero-epidemiological study was undertaken to determine the age specific prevalence rates of hepatitis A virus (HAV) and hepatitis B virus (HBV) infection in a band of Bushmen in the West Caprivi, Namibia. All children tested and all but two of the adults tested showed the presence of anti-HAV antibodies. Nineteen individuals (18%) were positive for HBsAg and 65 (61%) individuals had serologic evidence of past exposure to HBV infection.

Astrovirus-like particles, adenoviruses and rotaviruses associated with diarrhoea in piglets.

Faecal specimens from 1- to 7-week-old piglets (n = 251) with acute diarrhoeal illness were examined by direct negative staining electron microscopy for the presence of viral agents. Rotaviruses were observed in almost 40% of cases while adenoviruses and astroviruses were also observed in 3 specimens each. The majority of the rotaviruses reacted with a commercial Group A rotavirus ELISA although in 11 specimens they did not react with the Group A antigen and could represent atypical rotaviruses. This is the first report of adenoviruses and astroviruses in diarrhoeal faecal specimens from pigs in South Africa.

Low prevalence of human T lymphotropic virus type I in !Kung San in Bushmanland, Namibia.

Antibodies to human immunodeficiency virus 1 (HIV-1) and human T lymphotropic virus type 1 (HTLV-I) have been identified in various population groups living in southern and central Africa. Sera from 291 !Kung Bushmen in Bushmanland, Namibia were examined for the presence of antibodies to HIV-1 and HIV-2 and to HTLV-I. Initial screening for HIV-1/2 by two enzyme-linked immunosorbent assays (ELISAs) revealed evidence of past exposure in four individuals. However, no HIV-1/2 infection could be confirmed by a particle agglutination assay, a recombinant ELISA, or by Western blot for HIV-1 and HIV-2. Indeterminate Western blot profiles (with a p55 for each and either a p25 or p18 band) existed for all four HIV-1-reactive sera. Eight sera were reactive in the HTLV-I ELISA, although only five were positive on a second ELISA. Only three of the five HTLV-I-reactive sera could be confirmed by Western blot.

Prevalence of hepatitis B in !Kung (San) children from Bushmanland, Namibia.

Serum samples from 248 predominantly !Kung children (aged 5-19 years) attending various bush schools and a clinic in Bushmanland, northern Namibia were examined for the presence of hepatitis B virus (HBV) markers by radioimmunoassay. HBsAg was detected in 18 (7.3%) children while 117 (47.6%) showed one or more markers of HBV infection. These prevalence rates are lower than those of the closely situated territory of Kavango to the north and East Caprivi to the north-east. No significant difference in HBs antigenaemia between !Kung boys and girls was found (p > 0.05). However, HBs antigenaemia was found to vary between children in different bush schools. A significantly higher number of children attending the Omatako bush school were positive for HBsAg than the number attending the Luhebu bush school (p < 0.0167). These local variations could assist in the initial targeting of HBV vaccine to high-risk areas. In situ investigations of hyperendemic foci in Bushmanland, Namibia should help to elucidate the variation in HBs antigenaemia and the factors responsible for transmission of HBV.

Human T-lymphotropic virus type I-associated myelopathy. A case report.

Tropical spastic paraparesis (TSP) has been reported from various parts of the world for several decades. Recently reports have emerged from Japan and also countries in tropical zones associating endemic TSP with abnormally high titres of antibodies to human T-lymphotropic virus type I (HTLV-I). Data indicate that this lymphotropic retrovirus is neuropathogenic, either by direct invasion or via immunopathological mechanisms. A South African man is described who met the diagnostic criteria of TSP. Both serum and cerebrospinal fluid were antibody-positive for HTLV-I. It is possible that HTLV-I infection may be implicated in the 'myelopathies of undetermined cause' that form a substantial subgroup of spinal cord disease occurring in black South Africans.