Kamal K. Mittal

Comparative Virulence and Immunogenicity of the Towne Strain and a Nonattenuated Strain of Cytomegalovirus

The Towne strain cytomegalovirus and a low-passage strain, Toledo-1, were compared for virulence and immunogenicity in healthy adult male subjects to determine the suitability of the Towne strain for vaccination. Five seropositive subjects who received the Toledo-1 strain developed infections ranging in severity from laboratory abnormalities to mild mononucleosis syndromes (mean incubation, 4.7 weeks). None of the four seronegative subjects receiving the Towne strain developed systemic infection, but all developed delayed local reactions at the injection sites. All subjects developed cytotoxic lymphocyte responses specific to cytomegalovirus, usually HLA-restricted, but these were of greater magnitude and duration in the Toledo-1 recipients. The latter also developed natural killer cell and interferon responses, atypical lymphocytosis, inversion of helper/suppressor cell ratios, and depressed responses to T-cell mitogens, none of which occurred in Towne strain recipients. The results further substantiate the avirulence and immunogenicity of the Towne strain cytomegalovirus.

The HLA polymorphism and susceptibility to disease.

Abstract. Remarkable differences were observed when 1,465 healthy Caucasian individuals and 128 healthy Negro individuals were compared for the genetic distribution of 25 different HLA antigens. Caucasians had a significantly higher frequency of A1, A3, B8, and Bw16, and Negroes of A28 and Aw30. The haplotype which had the highest incidence as well as the greatest positive linkage disequilibrium was A1‐B8 among Caucasians and A2‐B12 among Negroes. Genetic distance between the two races was 0.0592.

Cross-reactivity of monospecific anti-HL-A antisera.

Abstract. 32 ‘monospecific’ anti‐HL‐A alloantisera were absorbed in separate tests with platelets from a maximum of 56 different persons and examined for residual cytotoxicity against target lymphocytes from one or two unrelated persons having the homologous (or test) antigen. Of the 799 combinations in which platelets had the test antigen, 715 (90%) were specifically inhibited; of the 720 combinations in which platelets had the cross‐reactive antigen(s) (but not the test antigen), 417 (58%) were specifically cross‐inhibited; and of the 1,839 combinations in which platelets had neither the homologous nor a discernable cross‐reactive antigen, 133 (7%) were cross‐inhibited ‘nonspecifically’. Earlier findings of cross‐reactivity were confirmed, and results suggested that HL‐A1, HL‐A10 and W30 on platelets may cross‐inhibit anti‐HL‐A2 antibodies; HL‐A7 and W21 may cross‐inhibit anti‐HL‐A5 and anti‐W5 antibodies; W16 may cross‐inhibit anti‐HL‐A5 antibodies; and W22 may cross‐inhibit anti‐HL‐A13 antibodies.

Human Histocompatibility (Hl-A) Antigens in Semen and their Role in Reproduction*†

Seminal plasma from 7 of 10 normal persons was found to inhibit anti-HL-A2, 3, 7, 8, and 12 antisera specifically. Inhibition by seminal plasma appeared quantitatively less than that by whole serum and even less than that by platelets from the same individuals. No decrease in the number of offspring was found due to increased numbers of HL-A incompatibilities of the male spouse in 67 normal couples. No clear decrease in the number of pregnancies was observed in normal women with lymphocytotoxic antibodies. A similar study with infertile persons may yet reveal a role for HL-A antigens in human reproduction.

Evidence for lack of linkage between HLA and C3 deficiency in man

In the human, inheritance of the C2 component of the classic complement system (Fu et al. 1974) and of properdin factor B (GBG, C3PA) of the alternative pathway of complement activation (Allen 1974) have been shown to be controlled by genes linked to inheritance of the HLA system. In the pedigrees of families with Clr and C6 deficiency, respectively, genetic independence appeared to exist between the HLA system and deficits in the levels of these components of complement (Mittal et al. 1976), although in a separate study of four unrelated individuals with approximately half-levels of C6, an association between HLA Aw24 and C6 levels was suggested (Raum et al. 1976). It has been shown in mice that the S region of H-2 influences the hemolytic activity of mouse complement (D6mant et al. 1973), and further, that serum levels of C3 in young mice are determined by genes linked to the H-2 system (Ferreira and Nussenzweig 1976). It has also been demonstrated that the H-2-1inked Ss protein is the murine equivalent of human C2 or C4 (Capra etal. 1975, Meo et al. 1975, Lachmann etal. 1975, Curman etal. 1975); the mechanism which underlies the association is unknown. Fifteen family members of a patient whose homozygous C3 deficiency has previously been reported (Osofsky et al. 1976) were tested for serum C3 protein levels (Kohler and M/iller-Eberhard 1967), HLA (Mittal etal. 1968, 1973), and ABO antigens by the agglutination method. The family pedigree is shown in Figure 1. The individuals with C3 levels below 80 mg per cent are probably heterozygotes. The propositus, who had a complete C3 deficiency, had an HLA genotype (A9, BS/A2, B18) identical to that of his sister, who had only a 50 per cent C3 deficit. The maternal chromosome (A9, B5) of the propositus was shared by his other sister, a maternal aunt, and a maternal uncle, each of whom had normal C3 levels. The paternal chromosome (A2, B18) was shared by the propo-

A role for cAMP in the preparation of human platelets for the extraction of histocompatibility antigens.

Abstract Conditions were developed for the preparation of platelets to obtain optimal yields of HL-A antigens by hypertonic salt (3 M KCl) extraction. Although these antigens were readily demonstrable on the surface of platelets prepared in 10 −2 M EDTA, they could not be solubilized by 3 M KCl. However, antigens could readily be solubilized from platelets prepared in 10 −2 M caffeine, 10 −2 M theophylline or a combination of 10 −6 M prostaglandin E 1 , and 10 −3 M theophylline. Using these conditions, three fractions of HL-A antigenic activity, as determined by specific inhibition of cytotoxicity, were obtained; (1) a fraction extractable by 3 M KCl; (2) a fraction not extractable by 3 M KCl but extractable by isotonic saline; and (3) residual activity not extractable by either solvent. Significantly higher intracellular cAMP levels were observed in those platelet preparations from which HL-A antigens were solubilized. Quantitative inhibition studies of whole platelets, performed using monospecific HL-A antisera, indicated that increased cAMP levels did not alter the immunologic potency of cell-bound HL-A antigens. In addition, extractions of cell surface-radioiodinated platelets demonstrated that a generalized increase in the extractability of cell membrane proteins, by hypertonic salt, resulted from increased intracellular cAMP levels. These results indicate that the levels of platelet cAMP, prior to 3 M KCl extraction, are important in determining whether HL-A antigens can be effectively solubilized.