Vaginal infections of BALB/c Ann mice with herpes simplex virus type 1 (HSV-1) were studied. Mice were inoculated with virulent strains ANG path and 17 syn+ or low-virulent recombinant strains 27/III and 17-syn3 that differ from parental strains in their glycoprotein B (gB) gene sequences. When low-virulent strains were inoculated separately, no vaginitis/vulvitis was produced despite replication in the vagina. In contrast, after coinfection of mice with the two low-virulent strains, vaginitis/vulvitis was produced and virus could be recovered from the central nervous system (CNS). Two of the CNS isolates produced vaginitis/vulvitis, neuroinvasiveness and death of mice after vaginal infection. Restriction fragment analysis and sequencing were used to assess recombination events in the gB gene sequence of the CNS isolates. After mixed vaginal infection recombination between non-virulent HSV strains occurs, resulting in vaginitis/vulvitis and neuroinvasiveness. No correlation was detected between the syncytial phenotype and local vaginal virulence. Virulence of HSV is not solely dependent on gB function; it seems to be more probable that several genes act in concert to induce virulence and neuroinvasiveness.

After vaginal infections of mice with neuroinvasive strains of herpes simplex virus type 1 and 2 (HSV-1, HSV-2) virus replicates in the epithelium of the vagina, in the paravaginal ganglia, in the spinal cord and finally in the brain and in the adrenal glands. However, viral antigens could be demonstrated only in the medulla of the adrenal glands but not in the cortex, as assessed by immunohistochemistry (IHC). HSV could not be isolated from liver, spleen, uterus, and ovaries. This contrasts to the intraperitoneal (i.p) route of infection with replication in different visceral organs including the adrenal gland's cortex.

One of the causes of genital tract infections in humans are herpes simplex virus types 1 and 2 (HSV-1, HSV-2). Although primary and recurrent infections can be clinically apparent and in part very serious, many infections are asymptomatic and result only in temporary genital shedding of virus (recurrences). During our investigations of vaginitis, strain IES of HSV-1 produced an asymptomatic infection. Replication in the murine vaginal (vag.) epithelium as well as antibody formation after vag. infection was comparable to those of survivors after infection with highly virulent strains. Titration of liver, spleen, ovaries, adrenal glands spinal cord, or brain after vag. IES infection revealed no virus, whereas after i.p. infection virus could be demonstrated in many organs examined. Histological examination with a DNA probe (in situ hybridisation), HSV antibodies (immunohistochemistry), and haematoxylin and eosin (HE) staining showed only small focal HSV lesions of the vaginal epithelium in early stages of the infection, never exceeding to the subepithelial tissue. Severe infiltrations and ulcerations after infection with highly virulent strains (17syn +, ER-) could never be demonstrated after IES vag. infection. Identical replication rates of both groups of HSV despite much greater areas of epithelial necrosis with the virulent strains may be explained by the large number of virus inactivating granulocytes induced by the virulent strains, thus inactivating the hypothetical higher virus load.

The vagina and medulla of the adrenal gland of mice vaginally infected with herpes simplex virus (HSV) types 1 and 2 were examined in the latent stage of infection (5 to 51 weeks post-infection). RNA in situ hybridization with HSV-1 and -2 latencyassociated transcript (LAT) RNA probes resulted in positively stained neuronal cell nuclei in the uterovaginal plexus, but not in the medulla of the adrenal gland. These organs were chosen because HSV antigens can be detected not only in the vaginal epithelium, but also in neurons of the uterovaginal plexus and in the medulla of the adrenal gland at the acute stage of genital infection. To our knowledge, this is the first report describing LATs in neurons of the uterovaginal plexus in the genital tract of latently HSV-infected mice. Recently, latent HSV was reported in ganglia of the gastric plexus (Gesser et al., 1994 ; Gesser & Koo, 1996), a part of the autonomic nervous system. Because neurons of the autonomic nervous system exist in close proximity to the vaginal epithelium, we looked at the uterovaginal ganglia (Frankenha$ user plexus) to determine whether or not HSV can establish latency in these neurons. InA great number of publications exists demonstrating latency-associated transcripts (LATs) in situ ( Arthur et al., 1993 ; Ecob-Prince et al., 1994 ; Fraser et al., 1992 ; Mitchell et al., 1990 a, b ; Speck & Simmonds, 1992 ;Spivack & Fraser, 1987 ;Tanaka et al., 1994 ;Valyi-Nagy et al., 1994). We also employed the RNA in situ hybridization (