HTLV infections are common among intravenous drug users and are primarily caused by HTLV-II. Among patients seen at STD clinics, HTLV is strongly associated with intravenous drug use, but the retrovirus is also prevalent among non-drug users.

Cloning and expression of hepatitis C virus have allowed the development of immunoassays to detect hepatitis C virus infection. However, currently available recombinant fusion protein C100-3 assays, based on a nonstructural protein of the virus, are limited in sensitivity, particularly for detecting acute infection. In this report seroconversion panels showed that an assay based on synthetic peptides, derived from immunodominant regions of both capsid and nonstructural proteins, accelerated hepatitis C virus antibody detection by 4-10 weeks. In screening, this enzyme immunoassay increased detection from 47% to 64% in plasmapheresis donors with elevated alanine aminotransferase levels (>100 international units per liter), from 15% to 24% in anti-hepatitis B core antigen-positive blood donors, and from 28% to 42% in renal dialysis patients when compared with nonstructural peptide-based assays. The screening assay was repeatedly reactive for 27 of 2902 volunteer blood donor samples (0.93%); four sera reacted only with the capsid antigen. The peptide test distinguished true from false positive results in agreement with recombinant immunoblot assay in 96% of blood donor samples repeatably reactive on a recombinant hepatitis C virus enzyme immunoassay.

A titer for homologous viral neutralization activity (greater than 1:19,683) was observed after a 3.5-year immunization period with an octameric, branching peptide representing the principal neutralizing determinant (PND) of the human immunodeficiency virus-1IIIB envelope protein. Booster immunizations elicited persistent and potent antibodies in guinea pigs, exceeding responses produced by a conventional bovine serum albumin conjugate by 100-fold. Peptide length, central presentation of a conserved sequence, and inclusion of an upstream sequence contributed to immunogenicity. Titers (greater than 1:1,000) of heterotypic neutralizing antibodies also developed. Octameric PND peptides are a promising approach for an acquired immunodeficiency syndrome (AIDS) vaccine.

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ABSTRACr-The amino-terminal sequences of two peptides of type 24 streptococcal M protein show similarities with that of rabbit skeletal muscle tropomyosin, having up to 40% identical residues and probabilities of occurring by chance as low as P < 10-5. In addition, a hexapeptide (Glu-Ala-Glu-Lys-AlaAla) that is found five times in the M24 protein was shown to be identical to a sequence in tropomyosin. Similarities are also seen in the amino acid compositions and physicochemical properties of tfie two proteins. The amino-terminal sequences of peptides from another bacterial surface protein, staphylococcal protein A, are highly correlated with segments of two other myofibrillar proteins, rabbit actin (P < 10-7) and rabbit myosin Al light chain (P < 10-6). The data presented suggest that a close structural relationship exists between mammalian muscle proteins and the biologically active surface proteins of staphylococci and streptococci. In addition, the correlation between sequences in M protein and tropomyosin represents direct evidence of a structural similarity at a molecular level between a streptococcal protein and a mammalian muscle component and may therefore prove relevant to the pathogenicity of the streptococcus.Group A streptococci possess antiphagocytic surface antigens, known as M proteins, that are primarily responsible for the virulence of these organisms (1). Based on extensive immunological data, it has been clearly shown that resistance to streptococcal infection is dependent on neutralization of the antiphagocytic effect of M proteins by type-specific opsonic antibodies (1, 2). Immunological cross reactions do occur' between certain of the more than 70 immunologically distinct M types (3, 4), but the antibodies involved rarely afford crossprotection (3). Recent peptide analyses (5) and sequence studies (6, 7) on a limited number of M protein types revealed that, in spite of a common biological activity, M proteins are composed of different primary structures. Despite these immunological and structural differences, all M protein molecules studied to date share certain noteworthy chemical and physical properties (8). Their extreme thermal stability (9), their highly elongated shape (10, 11), and their appearance as a network of projections on streptococcal cell walls (12) suggested that M proteins might have properties in common with previously characterized fibrous proteins.This report describes striking chemical, physical, and sequence similarities between streptococcal M protein and rabbit skeletal muscle tropomyosin. In addition, computer analysis of the partial sequence of staphylococcal protein A, another biologically active, Gram-positive, surface protein, having properties in common with M protein, reveals significant homology with two other myofibrillar proteins, actin and myosin Al light chain.