- Volume 64, Issue 9, 1983

The immune response to Japanese encephalitis virus (JEV) was assessed in JEV-infected mice (mothers) and their offspring. The congenitally infected baby mice responded poorly in all assays for cell-mediated immunity. The total number of their splenic cells remained unaltered but the percentage of T cells was significantly reduced; a depressed delayed hypersensitivity response was seen against both homologous (JEV) and heterologous (sheep erythrocytes) antigens. In addition, significantly higher leukocyte migration inhibition (LMI) of spleen cells in the presence of specific antigen was observed. Adult mice infected during pregnancy demonstrated an impaired delayed hypersensitivity response to JEV antigen only. LMI was positive in mothers at 2 weeks post-partum, but not at later periods.

Passive transfer of monoclonal antibodies specific for herpes simplex virus type 1 (HSV-1) glycoproteins gC or gD resulted in the generation of highly potent HSV-specific and H-2-restricted primary cytotoxic T-lymphocytes (CTL) in the lymph nodes of recipients provided they were injected at 12 h post-infection. When the same antibody was injected at 3 h before HSV infection, the recipients failed to generate primary anti-HSV CTL. Rather, lymph node cells from such donors proved unsuitable for the initiation in vitro of a secondary anti-HSV CTL response by restimulation.

During experiments on the purification of scrapie infectivity, changes were found in the dynamics of scrapie titration. After exposure to detergent, infectivity estimates by both endpoint titration and incubation period were altered. The addition of detergent to the diluent used in titration resulted in at least a 100-fold increase in the infectivity estimate. This suggests that the amount of scrapie in a sample, as measured by serial dilution and titration, may be underestimated to different extents, depending on the biochemical milieu of the inoculum. Membrane fractions treated with detergents before dilution exhibited longer incubation periods than untreated fractions for the same number of infectious units of scrapie. This demonstrates that detergent treatments and possibly other biochemical manipulations can cause changes in the response of the host to the inoculum that are not detectable if incubation periods alone are used to estimate scrapie ‘titre’.

Cells which produce ecotropic murine leukaemia virus have been detected in the bone marrow and the spleen of weanling AKR mice, using an infectious centre technique based on the XC test. There is a noticeable increase in the number of virusproducing cells between day 3 and day 12 after birth, in both of these organs. Some of the virus-producing cells that appear after day 3 have been identified as haemopoietic precursor cells of the granulocyte-macrophage blood lineage. Such precursor cells do not produce virus during the embryonic period and they progressively become involved in virus production after day 3. By day 12, all of them are active virus producers. Thus, the ecotropic virus is expressed in precursor cells of the haemopoietic system, and the latter represent at least one-third of the virus-producing cells in the bone marrow of young AKR mice.

Intracellular polyadenylated viral RNA from cells infected by five different isolates of Moloney murine sarcoma virus (Mo-MuSV) was analysed by gel transfer hybridization. Genomic sizes of 4.6 kilobases (kb) for the m1-MuSV isolate, 5.2 kb for the m3- and 124-MuSV, 6.1 kb for the HT1-MuSV and 6.7 kb for the 78-A1-MuSV were determined. With the exception of the m1 strain, subgenomic RNA species were found in cells infected by the various isolates. However, no common subgenomic RNA containing v-mos sequences could be characterized. Each transformed cell line expressed a different set of viral RNA species in terms of size and structure.

The role of phosphorylation and the minor core protein V in adenovirus type 2 assembly was examined. Comparison of the phosphoprotein composition of top components (TC), young virions and mature virions of wild-type and assembly mutants showed specific changes related to virus assembly and maturation. TC were identified as precursors of young virions which contain two molecular weight forms of core protein V, one of which is phosphorylated. Conversion of TC into young virions by DNA encapsidation resulted in the loss of the unphosphorylated form of protein V, and subsequent maturation to old virions resulted in the dephosphorylation of the core protein. This last step is blocked by the ts1 mutation which inactivates the viral endoproteinase.

Monoclonal antibodies to the haemagglutinin—neuraminidase (HN), fusion (F), polymerase and nucleocapsid polypeptides of Newcastle disease virus were prepared. Two epitopes were recognized on the HN polypeptide: one was associated with inhibition of haemagglutination and poor neutralization and the other with good neutralization and no inhibition of haemagglutination. The most effective neutralizing antibody was that produced against the F polypeptide. The poorer neutralization associated with the antibody against the HN epitope was augmented by antiglobulin or complement. The monoclonal antibodies that inhibited haemagglutination also inhibited neuraminidase activity when fetuin but not neuraminyl lactose was the substrate.

The cloned BglII N fragment of herpes simplex virus type 2 (HSV-2) DNA has been shown to code for a 35K polypeptide. Subfragments made by cleavage with XhoI, BamHI, SstII and XorII were then cloned and used with RNA extracted from HSV-2-infected cells for mRNA selection and in vitro protein synthesis. We found that the major translation product of such hybrid-selected mRNA has a molecular weight of 35000. By further mapping, DNA coding sequences for this mRNA were located within the region of BglII N, at approximately 0.585 to 0.596 genome map units. DNA sequences complementary to mRNA encoding a 56K polypeptide were located between 0.607 and 0.612 map units.

Uptake of [3H]thymidine by serum-starved baby hamster kidney cells infected with herpes simplex virus type 2 was investigated by light microscopic and electron microscopic autoradiography. The distribution of incorporated label altered throughout the period of viral DNA synthesis. It was restricted initially to a few well-defined sites within the nucleus which increased in size and spread as infection proceeded until the entire nucleus was involved. The label was not associated with any identifiable subnuclear structure although there was a high degree of association with the nuclear membrane at early times post-infection.

Digestion of the N-acetylated-tyrosylated form of brome mosaic virus (BMV) RNA with proteinase K removed the 3′-blocking N-acetyl-tyrosine residue. Removal of the blocking group affected neither infectivity nor mRNA activity. The previously reported effect of acetylation of tyrosylated BMV RNA on infectivity appears to result from non-specific acetylation of the RNA.