The distribution of ABO and Rh-D blood groups was studied among 150,536 blood donors screened at the Dr John Scudder Memorial Blood Bank, Christian Medical College Hospital, Vellore, over a period of 11 years (April 1988 to March 1999). The most common blood group was found to be group O [58,330 (38.75%)], followed by group B [49,202 (32.69%)], and group A [28,372 (18.85%)]. The least common blood group was AB group [7,930 (5.27%)]. A2 or A2B groups were found in 3.01% and 1.43% of donors, respectively. The prevalence of Rh-D negative group was found in 8,225 (5.47%) donors. Bombay group (H negative non-secretor, genotype hh phenotype Oh) was found in six donors (0.004%). Although the incidence of Rh-D negative group was identical to previously published data from North India, the most common blood group was O group in our study as opposed to B group.

During replication of human immunodeficiency virus type 1 (HIV-1), proteolytic cleavage of Gag and Gag-Pol precursor proteins into different functional protein subunits is catalyzed by the viral proteinase, and this enzyme is the target of the antiviral proteinase inhibitor, Ro 31-8959. We investigated in vitro which HIV mutants with reduced sensitivity to Ro 31-8959 emerged during proteinase inhibition treatment; from three different HIV-1 strains, comparable progeny virus resistant to proteinase inhibitor were found, whereas the same experimental protocol detected no resistant HIV-2 mutants. Molecular analysis of the mutations underlying resistance revealed a multistep mechanism in which an amino acid exchange was common to all resistant isolates, and in all experiments preceded further exchanges at position 90 (leucine to methionine) and/or at position 54 (isoleucine to valine). For wild-type strains the 90% inhibitory concentrations of Ro 31-8959 were close to 20 nM, whereas HIV-1 mutants with all 3 amino acid exchanges had more than 50-fold increased 90% inhibitory concentrations (above 1000 nM). The primary event (Gly-48 to valine) occurs at the hinge of the flaps of the proteinase, thus hampering entry of the inhibitor to the active center and suggesting steric hindrance. Detailed knowledge of this stereotypic process could open inhibitor design, thus preventing conceivable escape of resistant virus on proteinase inhibitor action.

Monoclonal antibodies (McAb) were obtained to potato virus Y (PVY) after immunisation of BALB/c mice with purified PVY, tobacco necrotic strain (PVY,). Spleen cells from a mouse showing a high serum titre were used for fusion with X63NS 1 myeloma cells. Hybridomas were selected in medium containing HAT. Culture supernatants were screened for antibody production against PVY, ordinary strain (PVY,) and PVY, using indirect ELISA.Clones of interest were further cross-reacted with 12 isolates each of PVY, and PVY, and two isolates of potato virus A (PVA) and healthy sap.For further trials, two clones which reacted specifically with PVY, isolates and one which detected all PVY isolates except two of potato virus C (PVC) were selected.

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In an investigation conducted over 5 years, tests of samples from the Scottish Seed Potato Classification Scheme showed that when monoclonal antibodies (McABs) were used with the enzyme‐linked immunosorbent assay (ELISA), they reliably detected the tobacco veinal necrosis strain of potato virus Y (PVYN). Polyclonal antibodies used in the first 3 years of the investigation were unreliable in differentiating PVYN from the ordinary strain (PVYN). It is suggested that ELISA and McABs be routinely used to diagnose PVYN and that all samples which give negative results be further assayed biologically to identify the virus or to indicate strains of PVYN not detectable by the McAB. Problems encountered with both assay systems are discussed.

The extent of human T-cell lymphotropic retrovirus HTLV-I and HTLV-II infections in the general population in central Europe has not been investigated fully. Two hundred forty-eight thousand blood donors from southern Germany were examined serologically for antibodies to the human lymphotropic retroviruses HTLV-I and HTLV-II: 0.021% were confirmed positive and 0.056% were "indeterminate". A limited number of seropositives and "indeterminate" samples were analyzed by polymerase chain reaction (PCR): the seropositives were confirmed as positive and 43% of the "indeterminate" samples were PCR-positive. The range of 0.021% HTLV-positives in 248,000 donors, i.e. about two in 10,000 individuals, mirrors closely the published data for the United States.

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